diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cef23f26fc..ffd3d0686b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -91,9 +91,8 @@ jobs:
         # The $(ls ...) shell expansion is done in the Github environment;
         # the value of TOGA_INSTALL_COMMAND will be a literal string,
         # without any shell expansions to perform
-        TOGA_INSTALL_COMMAND="python -m pip install ../$(ls core/dist/toga_core-*.whl)[dev] ../$(ls dummy/dist/toga_dummy-*.whl)" tox -e py-core
-        cd core
-        mv .coverage .coverage.${{ matrix.platform }}.${{ matrix.python-version }}
+        TOGA_INSTALL_COMMAND="python -m pip install ../$(ls core/dist/toga_core-*.whl)[dev] ../$(ls dummy/dist/toga_dummy-*.whl)" tox -e py
+        mv core/.coverage core/.coverage.${{ matrix.platform }}.${{ matrix.python-version }}
     - name: Store coverage data
       uses: actions/upload-artifact@v3.1.3
       with:
@@ -128,7 +127,7 @@ jobs:
         cd core
         python -m coverage combine
         python -m coverage html --skip-covered --skip-empty
-        python -m coverage report --rcfile ../pyproject.toml # --fail-under=100
+        python -m coverage report --rcfile ../pyproject.toml --fail-under=100
     - name: Upload HTML report if check failed.
       uses: actions/upload-artifact@v3.1.3
       with:
@@ -136,56 +135,6 @@ jobs:
         path: core/htmlcov
       if: ${{ failure() }}
 
-  backend:
-    runs-on: ${{ matrix.runs-on }}
-    needs: [package, core]
-    strategy:
-      matrix:
-        backend: [ "android", "cocoa", "gtk", "iOS", "web", "winforms" ]
-        include:
-          - runs-on: ubuntu-latest
-          - python-version: "3.8"  # Should be env.min_python_version (https://github.com/actions/runner/issues/480)
-          - pre-command:
-
-          - backend: cocoa
-            runs-on: macos-latest
-
-          - backend: gtk
-            pre-command: |
-              sudo apt update -y
-              sudo apt install -y pkg-config python3-dev libgirepository1.0-dev libcairo2-dev gir1.2-gtk-3.0
-
-          - backend: iOS
-            runs-on: macos-latest
-
-          - backend: winforms
-            runs-on: windows-latest
-            # Py3.9 is the first Python version for which
-            # a wheel of pythonnet isn't available on PyPI.
-            python-version: "3.9"
-    steps:
-    - uses: actions/checkout@v4.1.1
-    - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v4.7.1
-      with:
-        python-version: ${{ matrix.python-version }}
-    - name: Get packages
-      uses: actions/download-artifact@v3.0.2
-      with:
-        name: ${{ needs.package.outputs.artifact-name }}
-    - name: Install dev dependencies
-      run: |
-        ${{ matrix.pre-command }}
-        # We don't actually want to install toga-core;
-        # we just want the dev extras so we have a known version of tox
-        python -m pip install ./core[dev]
-    - name: Test
-      run: |
-        # The $(ls ...) shell expansion is done in the Github environment;
-        # the value of TOGA_INSTALL_COMMAND will be a literal string,
-        # without any shell expansions to perform
-        TOGA_INSTALL_COMMAND="python -m pip install ../$(ls core/dist/toga_core-*.whl)[dev] ../$(ls dummy/dist/toga_dummy-*.whl) ../$(ls ${{ matrix.backend }}/dist/toga_${{ matrix.backend }}-*.whl)" tox -e py-${{ matrix.backend }}
-
   testbed:
     runs-on: ${{ matrix.runs-on }}
     needs: core
@@ -288,3 +237,11 @@ jobs:
       with:
         name: testbed-failure-app-data-${{ matrix.backend }}
         path: testbed/app_data/*
+    # This step is only needed if you're trying to diagnose test failures that
+    # only occur in CI, and can't be reproduced locally. When it runs, it will
+    # open an SSH server (URL reported in the logs) so you can ssh into the CI
+    # machine.
+    # - uses: actions/checkout@v3
+    # - name: Setup tmate session
+    #   uses: mxschmitt/action-tmate@v3
+    #   if: failure()
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 8cfba1e5e9..4d32924938 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -9,9 +9,17 @@ jobs:
   ci:
     uses: ./.github/workflows/ci.yml
 
+  docs:
+    name: Verify Docs Build
+    uses: beeware/.github/.github/workflows/docs-build-verify.yml@main
+    secrets: inherit
+    with:
+      project-name: "toga"
+      project-version: ${{ github.ref_name }}
+
   release:
     name: Create GitHub release
-    needs: ci
+    needs: [ ci, docs ]
     runs-on: ubuntu-latest
     permissions:
       contents: write
@@ -68,4 +76,4 @@ jobs:
       - name: Publish to TestPyPI
         uses: pypa/gh-action-pypi-publish@release/v1
         with:
-          repository_url: https://test.pypi.org/legacy/
+          repository-url: https://test.pypi.org/legacy/
diff --git a/.gitignore b/.gitignore
index 822fd730c6..95f5bd0ed5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@
 coverage.xml
 dist
 build
+logs
 _build
 distribute-*
 docs/env
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2d1d7d6e4f..4331e241bb 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -20,7 +20,7 @@ repos:
       - id: pyupgrade
         args: [--py38-plus]
   - repo: https://github.com/psf/black
-    rev: 23.10.0
+    rev: 23.10.1
     hooks:
     - id: black
   - repo: https://github.com/PyCQA/flake8
diff --git a/android/setup.cfg b/android/setup.cfg
index eb812857a0..e3ef915b3c 100644
--- a/android/setup.cfg
+++ b/android/setup.cfg
@@ -12,7 +12,7 @@ author_email = russell@keith-magee.com
 maintainer = BeeWare Team
 maintainer_email = team@beeware.org
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Intended Audience :: Developers
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
diff --git a/android/src/toga_android/app.py b/android/src/toga_android/app.py
index dd7ed4aa78..2c572a642a 100644
--- a/android/src/toga_android/app.py
+++ b/android/src/toga_android/app.py
@@ -1,13 +1,13 @@
 import asyncio
+import sys
 
+from android.graphics.drawable import BitmapDrawable
+from android.media import RingtoneManager
+from android.view import Menu, MenuItem
 from java import dynamic_proxy
 from org.beeware.android import IPythonApp, MainActivity
 
-import toga
-from android.graphics.drawable import Drawable
-from android.media import RingtoneManager
-from android.view import Menu, MenuItem
-from toga.command import Group
+from toga.command import GROUP_BREAK, SECTION_BREAK, Command, Group
 
 from .libs import events
 from .window import Window
@@ -41,18 +41,19 @@ def onResume(self):
         print("Toga app: onResume")
 
     def onPause(self):
-        print("Toga app: onPause")
+        print("Toga app: onPause")  # pragma: no cover
 
     def onStop(self):
-        print("Toga app: onStop")
+        print("Toga app: onStop")  # pragma: no cover
 
     def onDestroy(self):
-        print("Toga app: onDestroy")
+        print("Toga app: onDestroy")  # pragma: no cover
 
     def onRestart(self):
-        print("Toga app: onRestart")
+        print("Toga app: onRestart")  # pragma: no cover
 
-    def onActivityResult(self, requestCode, resultCode, resultData):
+    # TODO #1798: document and test this somehow
+    def onActivityResult(self, requestCode, resultCode, resultData):  # pragma: no cover
         """Callback method, called from MainActivity when an Intent ends.
 
         :param int requestCode: The integer request code originally supplied to startActivityForResult(),
@@ -75,94 +76,86 @@ def onActivityResult(self, requestCode, resultCode, resultData):
             print("No intent matching request code {requestCode}")
 
     def onConfigurationChanged(self, new_config):
-        pass
+        pass  # pragma: no cover
 
     def onOptionsItemSelected(self, menuitem):
-        consumed = False
-        try:
-            cmd = self.menuitem_mapping[menuitem.getItemId()]
-            consumed = True
-            if cmd.action is not None:
-                cmd.action(menuitem)
-        except KeyError:
-            print("menu item id not found in menuitem_mapping dictionary!")
-        return consumed
+        itemid = menuitem.getItemId()
+        if itemid == Menu.NONE:
+            # This method also fires when opening submenus
+            return False
+        else:
+            self.menuitem_mapping[itemid].action()
+            return True
 
     def onPrepareOptionsMenu(self, menu):
         menu.clear()
-        itemid = 0
+        itemid = 1  # 0 is the same as Menu.NONE.
+        groupid = 1
         menulist = {}  # dictionary with all menus
         self.menuitem_mapping.clear()
 
         # create option menu
         for cmd in self._impl.interface.commands:
-            if cmd == toga.SECTION_BREAK or cmd == toga.GROUP_BREAK:
+            if cmd == SECTION_BREAK or cmd == GROUP_BREAK:
+                groupid += 1
                 continue
-            if cmd in self._impl.interface.main_window.toolbar:
-                continue  # do not show toolbar commands in the option menu (except when overflowing)
 
-            grouppath = cmd.group.path
-            if grouppath[0] != Group.COMMANDS:
-                # only the Commands group (and its subgroups) are supported
-                # other groups should eventually go into the navigation drawer
+            # Toolbar commands are added below.
+            if cmd in self._impl.interface.main_window.toolbar:
                 continue
+
             if cmd.group.key in menulist:
                 menugroup = menulist[cmd.group.key]
             else:
                 # create all missing submenus
                 parentmenu = menu
-                for group in grouppath:
-                    groupkey = group.key
+                groupkey = ()
+                for section, order, text in cmd.group.key:
+                    groupkey += ((section, order, text),)
                     if groupkey in menulist:
                         menugroup = menulist[groupkey]
                     else:
-                        if group.text == toga.Group.COMMANDS.text:
+                        if len(groupkey) == 1 and text == Group.COMMANDS.text:
+                            # Add this group directly to the top-level menu
                             menulist[groupkey] = menu
                             menugroup = menu
                         else:
-                            itemid += 1
-                            order = Menu.NONE if group.order is None else group.order
+                            # Add all other groups as submenus
                             menugroup = parentmenu.addSubMenu(
-                                Menu.NONE, itemid, order, group.text
-                            )  # groupId, itemId, order, title
+                                groupid, Menu.NONE, Menu.NONE, text
+                            )
                             menulist[groupkey] = menugroup
                     parentmenu = menugroup
+
             # create menu item
-            itemid += 1
-            order = Menu.NONE if cmd.order is None else cmd.order
-            menuitem = menugroup.add(
-                Menu.NONE, itemid, order, cmd.text
-            )  # groupId, itemId, order, title
+            menuitem = menugroup.add(groupid, itemid, Menu.NONE, cmd.text)
             menuitem.setShowAsActionFlags(MenuItem.SHOW_AS_ACTION_NEVER)
             menuitem.setEnabled(cmd.enabled)
-            self.menuitem_mapping[
-                itemid
-            ] = cmd  # store itemid for use in onOptionsItemSelected
+            self.menuitem_mapping[itemid] = cmd
+            itemid += 1
 
         # create toolbar actions
-        if self._impl.interface.main_window:
+        if self._impl.interface.main_window:  # pragma: no branch
             for cmd in self._impl.interface.main_window.toolbar:
-                if cmd == toga.SECTION_BREAK or cmd == toga.GROUP_BREAK:
+                if cmd == SECTION_BREAK or cmd == GROUP_BREAK:
+                    groupid += 1
                     continue
-                itemid += 1
-                order = Menu.NONE if cmd.order is None else cmd.order
-                menuitem = menu.add(
-                    Menu.NONE, itemid, order, cmd.text
-                )  # groupId, itemId, order, title
-                menuitem.setShowAsActionFlags(
-                    MenuItem.SHOW_AS_ACTION_IF_ROOM
-                )  # toolbar button / item in options menu on overflow
+
+                menuitem = menu.add(groupid, itemid, Menu.NONE, cmd.text)
+                # SHOW_AS_ACTION_IF_ROOM is too conservative, showing only 2 items on
+                # a medium-size screen in portrait.
+                menuitem.setShowAsActionFlags(MenuItem.SHOW_AS_ACTION_ALWAYS)
                 menuitem.setEnabled(cmd.enabled)
                 if cmd.icon:
-                    icon = Drawable.createFromPath(str(cmd.icon._impl.path))
-                    if icon:
-                        menuitem.setIcon(icon)
-                    else:
-                        print("Could not create icon: " + str(cmd.icon._impl.path))
-                self.menuitem_mapping[
-                    itemid
-                ] = cmd  # store itemid for use in onOptionsItemSelected
+                    menuitem.setIcon(
+                        BitmapDrawable(
+                            self.native.getResources(), cmd.icon._impl.native
+                        )
+                    )
+                self.menuitem_mapping[itemid] = cmd
+                itemid += 1
 
+        # Display the menu.
         return True
 
 
@@ -184,9 +177,20 @@ def create(self):
         self._listener = TogaApp(self)
         # Call user code to populate the main window
         self.interface._startup()
-
-    def open_document(self, fileURL):
-        print("Can't open document %s (yet)" % fileURL)
+        self._create_app_commands()
+
+    def create_menus(self):
+        self.native.invalidateOptionsMenu()  # Triggers onPrepareOptionsMenu
+
+    def _create_app_commands(self):
+        self.interface.commands.add(
+            # About should be the last item in the menu, in a section on its own.
+            Command(
+                lambda _: self.interface.about(),
+                f"About {self.interface.formal_name}",
+                section=sys.maxsize,
+            ),
+        )
 
     def main_loop(self):
         # In order to support user asyncio code, start the Python/Android cooperative event loop.
@@ -200,7 +204,21 @@ def set_main_window(self, window):
         pass
 
     def show_about_dialog(self):
-        self.interface.factory.not_implemented("App.show_about_dialog()")
+        message_parts = []
+        if self.interface.version is not None:
+            message_parts.append(
+                f"{self.interface.formal_name} v{self.interface.version}"
+            )
+        else:
+            message_parts.append(self.interface.formal_name)
+
+        if self.interface.author is not None:
+            message_parts.append(f"Author: {self.interface.author}")
+        if self.interface.description is not None:
+            message_parts.append(f"\n{self.interface.description}")
+        self.interface.main_window.info_dialog(
+            f"About {self.interface.formal_name}", "\n".join(message_parts)
+        )
 
     def beep(self):
         uri = RingtoneManager.getActualDefaultRingtoneUri(
@@ -210,9 +228,16 @@ def beep(self):
         ringtone.play()
 
     def exit(self):
+        pass  # pragma: no cover
+
+    def get_current_window(self):
+        return self.interface.main_window._impl
+
+    def set_current_window(self, window):
         pass
 
-    async def intent_result(self, intent):
+    # TODO #1798: document and test this somehow
+    async def intent_result(self, intent):  # pragma: no cover
         """Calls an Intent and waits for its result.
 
         A RuntimeError will be raised when the Intent cannot be invoked.
@@ -234,6 +259,12 @@ async def intent_result(self, intent):
         except AttributeError:
             raise RuntimeError("No appropriate Activity found to handle this intent.")
 
+    def enter_full_screen(self, windows):
+        pass
+
+    def exit_full_screen(self, windows):
+        pass
+
     def hide_cursor(self):
         pass
 
diff --git a/android/src/toga_android/colors.py b/android/src/toga_android/colors.py
index 971ef9ea1b..ffd8a71e30 100644
--- a/android/src/toga_android/colors.py
+++ b/android/src/toga_android/colors.py
@@ -1,6 +1,5 @@
-from travertino.colors import NAMED_COLOR, TRANSPARENT
-
 from android.graphics import Color
+from travertino.colors import TRANSPARENT
 
 CACHE = {TRANSPARENT: Color.TRANSPARENT}
 
@@ -9,8 +8,6 @@ def native_color(c):
     try:
         color = CACHE[c]
     except KeyError:
-        if isinstance(c, str):
-            c = NAMED_COLOR[c]
         color = Color.argb(
             int(c.rgba.a * 255), int(c.rgba.r), int(c.rgba.g), int(c.rgba.b)
         )
diff --git a/android/src/toga_android/command.py b/android/src/toga_android/command.py
index 8575d29e27..1cec2474cc 100644
--- a/android/src/toga_android/command.py
+++ b/android/src/toga_android/command.py
@@ -1,7 +1,10 @@
+from org.beeware.android import MainActivity
+
+
 class Command:
     def __init__(self, interface):
         self.interface = interface
         self.native = []
 
     def set_enabled(self, value):
-        pass
+        MainActivity.singletonThis.invalidateOptionsMenu()
diff --git a/android/src/toga_android/dialogs.py b/android/src/toga_android/dialogs.py
index ab8c0abdf1..83f044ba21 100644
--- a/android/src/toga_android/dialogs.py
+++ b/android/src/toga_android/dialogs.py
@@ -1,10 +1,9 @@
 from abc import ABC
 
-from java import dynamic_proxy
-
 from android import R
 from android.app import AlertDialog
 from android.content import DialogInterface
+from java import dynamic_proxy
 
 
 class OnClickListener(dynamic_proxy(DialogInterface.OnClickListener)):
@@ -58,7 +57,7 @@ def __init__(
         self.native.show()
 
     def completion_handler(self, return_value: bool) -> None:
-        self.on_result(self, return_value)
+        self.on_result(return_value)
         self.interface.future.set_result(return_value)
 
 
diff --git a/android/src/toga_android/factory.py b/android/src/toga_android/factory.py
index fd6a84014f..9171ea4766 100644
--- a/android/src/toga_android/factory.py
+++ b/android/src/toga_android/factory.py
@@ -10,6 +10,7 @@
 from .widgets.canvas import Canvas
 from .widgets.dateinput import DateInput
 from .widgets.detailedlist import DetailedList
+from .widgets.divider import Divider
 from .widgets.imageview import ImageView
 from .widgets.label import Label
 from .widgets.multilinetextinput import MultilineTextInput
@@ -33,34 +34,41 @@ def not_implemented(feature):
 
 __all__ = [
     "App",
-    "Box",
-    "Button",
-    "Canvas",
     "Command",
-    "DateInput",
+    "MainWindow",
+    "not_implemented",
+    # Resources
+    "dialogs",
     "Font",
     "Icon",
     "Image",
+    "Paths",
+    # Widgets
+    # ActivityIndicator
+    "Box",
+    "Button",
+    "Canvas",
+    "DateInput",
+    "DetailedList",
+    "Divider",
     "ImageView",
     "Label",
-    "MainWindow",
     "MultilineTextInput",
     "NumberInput",
+    # "OptionContainer",
     "PasswordInput",
     "ProgressBar",
+    "ScrollContainer",
+    # "SplitContainer",
     "Selection",
     "Slider",
-    "ScrollContainer",
     "Switch",
     "Table",
     "TextInput",
     "TimeInput",
+    # "Tree",
     "WebView",
     "Window",
-    "DetailedList",
-    "not_implemented",
-    "Paths",
-    "dialogs",
 ]
 
 
diff --git a/android/src/toga_android/fonts.py b/android/src/toga_android/fonts.py
index 677343115f..f3b7018564 100644
--- a/android/src/toga_android/fonts.py
+++ b/android/src/toga_android/fonts.py
@@ -1,10 +1,10 @@
 from pathlib import Path
 
-from org.beeware.android import MainActivity
-
 from android import R
 from android.graphics import Typeface
 from android.util import TypedValue
+from org.beeware.android import MainActivity
+
 from toga.fonts import (
     _REGISTERED_FONT_CACHE,
     BOLD,
diff --git a/android/src/toga_android/images.py b/android/src/toga_android/images.py
index e3a357e57f..8ed5ededda 100644
--- a/android/src/toga_android/images.py
+++ b/android/src/toga_android/images.py
@@ -1,8 +1,7 @@
 from pathlib import Path
 
-from java.io import FileOutputStream
-
 from android.graphics import Bitmap, BitmapFactory
+from java.io import ByteArrayOutputStream, FileOutputStream
 
 
 class Image:
@@ -24,6 +23,11 @@ def get_width(self):
     def get_height(self):
         return self.native.getHeight()
 
+    def get_data(self):
+        stream = ByteArrayOutputStream()
+        self.native.compress(Bitmap.CompressFormat.PNG, 90, stream)
+        return bytes(stream.toByteArray())
+
     def save(self, path):
         path = Path(path)
         try:
diff --git a/android/src/toga_android/keys.py b/android/src/toga_android/keys.py
index db1407f57b..59e8cad444 100644
--- a/android/src/toga_android/keys.py
+++ b/android/src/toga_android/keys.py
@@ -1,4 +1,5 @@
 from android.view import KeyEvent
+
 from toga.keys import Key
 
 KEYEVENT_KEYS = {
@@ -197,13 +198,13 @@ def toga_key(event):
 
         # TODO: Confirm the mapping of Control, Meta and Hyper are correct.
         if event.isCapsLockOn():
-            modifiers.add(Key.CAPSLOCK)
+            modifiers.add(Key.CAPSLOCK)  # pragma: no cover
         if event.isShiftPressed():
-            modifiers.add(Key.SHIFT)
+            modifiers.add(Key.SHIFT)  # pragma: no cover
         if event.isCtrlPressed():
-            modifiers.add(Key.MOD_1)
+            modifiers.add(Key.MOD_1)  # pragma: no cover
         if event.isAltPressed():
-            modifiers.add(Key.MOD_2)
+            modifiers.add(Key.MOD_2)  # pragma: no cover
 
         return {"key": key, "modifiers": modifiers}
     except KeyError:  # pragma: nocover
diff --git a/android/src/toga_android/libs/events.py b/android/src/toga_android/libs/events.py
index 2e1a3c16f9..77cdde3bc2 100644
--- a/android/src/toga_android/libs/events.py
+++ b/android/src/toga_android/libs/events.py
@@ -7,12 +7,11 @@
 import sys
 import threading
 
+from android.os import Handler, Looper, MessageQueue
 from java import dynamic_proxy
 from java.io import FileDescriptor
 from java.lang import Runnable
 
-from android.os import Handler, Looper, MessageQueue
-
 # Some methods in this file are based on CPython's implementation.
 # Per https://github.com/python/cpython/blob/master/LICENSE , re-use is permitted
 # via the Python Software Foundation License Version 2, which includes inclusion
@@ -54,7 +53,7 @@ def __init__(self):
     # `executor` thread that typically exists in event loops. The event loop itself relies
     # on `run_in_executor()` for DNS lookups. In the future, we can restore `run_in_executor()`.
     async def run_in_executor(self, executor, func, *args):
-        return func(*args)
+        return func(*args)  # pragma: no cover
 
     # Override parent `_call_soon()` to ensure Android wakes us up to do the delayed task.
     def _call_soon(self, callback, args, context):
@@ -74,9 +73,13 @@ def run_forever_cooperatively(self):
         event loop interop is not paid by apps that don't use the event loop."""
         # Based on `BaseEventLoop.run_forever()` in CPython.
         if self.is_running():
-            raise RuntimeError("Refusing to start since loop is already running.")
+            raise RuntimeError(
+                "Refusing to start since loop is already running."
+            )  # pragma: no cover
         if self._closed:
-            raise RuntimeError("Event loop is closed. Create a new object.")
+            raise RuntimeError(
+                "Event loop is closed. Create a new object."
+            )  # pragma: no cover
         self._set_coroutine_origin_tracking(self._debug)
         self._thread_id = threading.get_ident()
 
@@ -97,7 +100,7 @@ def enqueue_android_wakeup_for_delayed_tasks(self):
         loop.
         """
         # If we are supposed to stop, actually stop.
-        if self._stopping:
+        if self._stopping:  # pragma: no cover
             self._stopping = False
             self._thread_id = None
             asyncio.events._set_running_loop(None)
@@ -124,7 +127,7 @@ def enqueue_android_wakeup_for_delayed_tasks(self):
     def _set_coroutine_origin_tracking(self, debug):
         # If running on Python 3.7 or 3.8, integrate with upstream event loop's debug feature, allowing
         # unawaited coroutines to have some useful info logged. See https://bugs.python.org/issue32591
-        if hasattr(super(), "_set_coroutine_origin_tracking"):
+        if hasattr(super(), "_set_coroutine_origin_tracking"):  # pragma: no cover
             super()._set_coroutine_origin_tracking(debug)
 
     def _get_next_delayed_task_wakeup(self):
@@ -140,7 +143,7 @@ def _get_next_delayed_task_wakeup(self):
             sched_count > _MIN_SCHEDULED_TIMER_HANDLES
             and self._timer_cancelled_count / sched_count
             > _MIN_CANCELLED_TIMER_HANDLES_FRACTION
-        ):
+        ):  # pragma: no cover
             # Remove delayed calls that were cancelled if their number
             # is too high
             new_scheduled = []
@@ -162,7 +165,7 @@ def _get_next_delayed_task_wakeup(self):
 
         timeout = None
         if self._ready or self._stopping:
-            if self._debug:
+            if self._debug:  # pragma: no cover
                 print("AndroidEventLoop: self.ready is", self._ready)
             timeout = 0
         elif self._scheduled:
@@ -199,8 +202,8 @@ def run_delayed_tasks(self):
         for i in range(ntodo):
             handle = self._ready.popleft()
             if handle._cancelled:
-                continue
-            if self._debug:
+                continue  # pragma: no cover
+            if self._debug:  # pragma: no cover
                 try:
                     self._current_handle = handle
                     t0 = self.time()
@@ -293,7 +296,7 @@ def message_queue(self):
     # unregister() and register(), so we rely on that as well.
 
     def register(self, fileobj, events, data=None):
-        if self._debug:
+        if self._debug:  # pragma: no cover
             print(
                 "register() fileobj={fileobj} events={events} data={data}".format(
                     fileobj=fileobj, events=events, data=data
@@ -303,7 +306,7 @@ def register(self, fileobj, events, data=None):
         self.register_with_android(fileobj, events)
         return ret
 
-    def unregister(self, fileobj):
+    def unregister(self, fileobj):  # pragma: no cover
         self.message_queue.removeOnFileDescriptorEventListener(_create_java_fd(fileobj))
         return super().unregister(fileobj)
 
@@ -311,13 +314,13 @@ def reregister_with_android_soon(self, fileobj):
         def _reregister():
             # If the fileobj got unregistered, exit early.
             key = self._key_from_fd(fileobj)
-            if key is None:
+            if key is None:  # pragma: no cover
                 if self._debug:
                     print(
                         "reregister_with_android_soon reregister_temporarily_ignored_fd exiting early; key=None"
                     )
                 return
-            if self._debug:
+            if self._debug:  # pragma: no cover
                 print(
                     "reregister_with_android_soon reregistering key={key}".format(
                         key=key
@@ -329,7 +332,7 @@ def _reregister():
         self.loop.call_later(0, _reregister)
 
     def register_with_android(self, fileobj, events):
-        if self._debug:
+        if self._debug:  # pragma: no cover
             print(
                 "register_with_android() fileobj={fileobj} events={events}".format(
                     fileobj=fileobj, events=events
@@ -348,7 +351,7 @@ def handle_fd_wakeup(self, fd, events):
 
         Filter the events to just those that are registered, then notify the loop."""
         key = self._key_from_fd(fd)
-        if key is None:
+        if key is None:  # pragma: no cover
             print(
                 "Warning: handle_fd_wakeup: wakeup for unregistered fd={fd}".format(
                     fd=fd
@@ -361,7 +364,7 @@ def handle_fd_wakeup(self, fd, events):
             if events & event_type and key.events & event_type:
                 key_event_pairs.append((key, event_type))
         if key_event_pairs:
-            if self._debug:
+            if self._debug:  # pragma: no cover
                 print(
                     "handle_fd_wakeup() calling parent for key_event_pairs={key_event_pairs}".format(
                         key_event_pairs=key_event_pairs
@@ -369,7 +372,7 @@ def handle_fd_wakeup(self, fd, events):
                 )
             # Call superclass private method to notify.
             self.loop._process_events(key_event_pairs)
-        else:
+        else:  # pragma: no cover
             print(
                 "Warning: handle_fd_wakeup(): unnecessary wakeup fd={fd} events={events} key={key}".format(
                     fd=fd, events=events, key=key
@@ -407,7 +410,7 @@ def onFileDescriptorEvents(self, fd_obj, events):
         selectors.EVENT_WRITE have the same value (2)."""
         # Call hidden (non-private) method to get the numeric FD, so we can pass that to Python.
         fd = getattr(fd_obj, "getInt$")()
-        if self._debug:
+        if self._debug:  # pragma: no cover
             print(
                 "onFileDescriptorEvents woke up for fd={fd} events={events}".format(
                     fd=fd, events=events
diff --git a/android/src/toga_android/widgets/base.py b/android/src/toga_android/widgets/base.py
index 9fae28706f..5acba9a5fb 100644
--- a/android/src/toga_android/widgets/base.py
+++ b/android/src/toga_android/widgets/base.py
@@ -1,13 +1,13 @@
 from abc import ABC, abstractmethod
-from decimal import ROUND_HALF_EVEN, ROUND_UP, Decimal
-
-from org.beeware.android import MainActivity
-from travertino.size import at_least
+from decimal import ROUND_HALF_EVEN, Decimal
 
 from android.graphics import PorterDuff, PorterDuffColorFilter, Rect
 from android.graphics.drawable import ColorDrawable, InsetDrawable
 from android.view import Gravity, View
 from android.widget import RelativeLayout
+from org.beeware.android import MainActivity
+from travertino.size import at_least
+
 from toga.constants import CENTER, JUSTIFY, LEFT, RIGHT, TRANSPARENT
 
 from ..colors import native_color
@@ -33,7 +33,7 @@ def scale_out(self, value, rounding=SCALE_DEFAULT_ROUNDING):
             return self.scale_round(value / self.dpi_scale, rounding)
 
     def scale_round(self, value, rounding):
-        if rounding is None:
+        if rounding is None:  # pragma: no cover
             return value
         return int(Decimal(value).to_integral(rounding))
 
@@ -182,18 +182,13 @@ def remove_child(self, child):
     # TODO: consider calling requestLayout or forceLayout here
     # (https://github.com/beeware/toga/issues/1289#issuecomment-1453096034)
     def refresh(self):
-        intrinsic = self.interface.intrinsic
-        intrinsic.width = intrinsic.height = None
+        # Default values; may be overwritten by rehint().
+        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
+        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
         self.rehint()
-        assert intrinsic.width is not None, self
-        assert intrinsic.height is not None, self
-
-        intrinsic.width = self.scale_out(intrinsic.width, ROUND_UP)
-        intrinsic.height = self.scale_out(intrinsic.height, ROUND_UP)
 
-    @abstractmethod
     def rehint(self):
-        ...
+        pass
 
 
 def align(value):
diff --git a/android/src/toga_android/widgets/box.py b/android/src/toga_android/widgets/box.py
index 2a584a130f..c4ad8dbe18 100644
--- a/android/src/toga_android/widgets/box.py
+++ b/android/src/toga_android/widgets/box.py
@@ -1,5 +1,3 @@
-from travertino.size import at_least
-
 from android.widget import RelativeLayout
 
 from .base import Widget
@@ -11,7 +9,3 @@ def create(self):
 
     def set_background_color(self, value):
         self.set_background_simple(value)
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(0)
-        self.interface.intrinsic.height = at_least(0)
diff --git a/android/src/toga_android/widgets/button.py b/android/src/toga_android/widgets/button.py
index ccc167fc5c..6fb4340b5f 100644
--- a/android/src/toga_android/widgets/button.py
+++ b/android/src/toga_android/widgets/button.py
@@ -1,8 +1,9 @@
-from java import dynamic_proxy
-from travertino.size import at_least
+from decimal import ROUND_UP
 
 from android.view import View
 from android.widget import Button as A_Button
+from java import dynamic_proxy
+from travertino.size import at_least
 
 from .label import TextViewWidget
 
@@ -13,7 +14,7 @@ def __init__(self, button_impl):
         self.button_impl = button_impl
 
     def onClick(self, _view):
-        self.button_impl.interface.on_press(None)
+        self.button_impl.interface.on_press()
 
 
 class Button(TextViewWidget):
@@ -41,5 +42,9 @@ def rehint(self):
             View.MeasureSpec.UNSPECIFIED,
             View.MeasureSpec.UNSPECIFIED,
         )
-        self.interface.intrinsic.width = at_least(self.native.getMeasuredWidth())
-        self.interface.intrinsic.height = self.native.getMeasuredHeight()
+        self.interface.intrinsic.width = self.scale_out(
+            at_least(self.native.getMeasuredWidth()), ROUND_UP
+        )
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.getMeasuredHeight(), ROUND_UP
+        )
diff --git a/android/src/toga_android/widgets/canvas.py b/android/src/toga_android/widgets/canvas.py
index 47cbb4508d..a2be9aaace 100644
--- a/android/src/toga_android/widgets/canvas.py
+++ b/android/src/toga_android/widgets/canvas.py
@@ -1,9 +1,5 @@
-from math import degrees, pi
-
-from java import dynamic_proxy, jint
-from java.io import ByteArrayOutputStream
-from org.beeware.android import DrawHandlerView, IDrawHandler
-from travertino.size import at_least
+import itertools
+from math import degrees
 
 from android.graphics import (
     Bitmap,
@@ -14,7 +10,11 @@
     Path,
 )
 from android.view import MotionEvent, View
-from toga.widgets.canvas import Baseline, FillRule
+from java import dynamic_proxy, jint
+from java.io import ByteArrayOutputStream
+from org.beeware.android import DrawHandlerView, IDrawHandler
+
+from toga.widgets.canvas import Baseline, FillRule, arc_to_bezier, sweepangle
 
 from ..colors import native_color
 from .base import Widget
@@ -40,11 +40,11 @@ def __init__(self, impl):
     def onTouch(self, canvas, event):
         x, y = map(self.impl.scale_out, (event.getX(), event.getY()))
         if (action := event.getAction()) == MotionEvent.ACTION_DOWN:
-            self.interface.on_press(None, x, y)
+            self.interface.on_press(x, y)
         elif action == MotionEvent.ACTION_MOVE:
-            self.interface.on_drag(None, x, y)
+            self.interface.on_drag(x, y)
         elif action == MotionEvent.ACTION_UP:
-            self.interface.on_release(None, x, y)
+            self.interface.on_release(x, y)
         else:  # pragma: no cover
             return False
         return True
@@ -58,7 +58,7 @@ def create(self):
 
     def set_bounds(self, x, y, width, height):
         super().set_bounds(x, y, width, height)
-        self.interface.on_resize(None, width=width, height=height)
+        self.interface.on_resize(width=width, height=height)
 
     def redraw(self):
         self.native.invalidate()
@@ -101,25 +101,8 @@ def quadratic_curve_to(self, cpx, cpy, x, y, path, **kwargs):
         path.quadTo(cpx, cpy, x, y)
 
     def arc(self, x, y, radius, startangle, endangle, anticlockwise, path, **kwargs):
-        sweepangle = endangle - startangle
-        if anticlockwise:
-            if sweepangle > 0:
-                sweepangle -= 2 * pi
-        else:
-            if sweepangle < 0:
-                sweepangle += 2 * pi
-
-        # HTML says sweep angles should be clamped at +/- 360 degrees, but Android uses
-        # mod 360 instead, so 360 would cause the circle to completely disappear.
-        limit = 359.999  # Must be less than 360 in 32-bit floating point.
-        path.arcTo(
-            x - radius,
-            y - radius,
-            x + radius,
-            y + radius,
-            degrees(startangle),
-            max(-limit, min(degrees(sweepangle), limit)),
-            False,  # forceMoveTo
+        self.ellipse(
+            x, y, radius, radius, 0, startangle, endangle, anticlockwise, path, **kwargs
         )
 
     def ellipse(
@@ -136,19 +119,23 @@ def ellipse(
         **kwargs,
     ):
         matrix = Matrix()
-        matrix.postScale(radiusx, radiusy)
-        matrix.postRotate(degrees(rotation))
-        matrix.postTranslate(x, y)
-
-        # Creating the ellipse as a separate path and then using addPath would make it a
-        # disconnected contour. And there's no way to extract the segments from a path
-        # until getPathIterator in API level 34. So this is the simplest solution I
-        # could find.
-        inverse = Matrix()
-        matrix.invert(inverse)
-        path.transform(inverse)
-        self.arc(0, 0, 1, startangle, endangle, anticlockwise, path)
-        path.transform(matrix)
+        matrix.preTranslate(x, y)
+        matrix.preRotate(degrees(rotation))
+        matrix.preScale(radiusx, radiusy)
+        matrix.preRotate(degrees(startangle))
+
+        coords = list(
+            itertools.chain(
+                *arc_to_bezier(sweepangle(startangle, endangle, anticlockwise))
+            )
+        )
+        matrix.mapPoints(coords)
+
+        self.line_to(coords[0], coords[1], path, **kwargs)
+        i = 2
+        while i < len(coords):
+            self.bezier_curve_to(*coords[i : i + 6], path, **kwargs)
+            i += 6
 
     def rect(self, x, y, width, height, path, **kwargs):
         path.addRect(x, y, x + width, y + height, Path.Direction.CW)
@@ -265,7 +252,3 @@ def get_image_data(self):
 
     def set_background_color(self, value):
         self.set_background_simple(value)
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(0)
-        self.interface.intrinsic.height = at_least(0)
diff --git a/android/src/toga_android/widgets/dateinput.py b/android/src/toga_android/widgets/dateinput.py
index 2f3e000c4e..a2398e687c 100644
--- a/android/src/toga_android/widgets/dateinput.py
+++ b/android/src/toga_android/widgets/dateinput.py
@@ -1,9 +1,8 @@
 from datetime import date, datetime, time
 
-from java import dynamic_proxy
-
 from android import R
 from android.app import DatePickerDialog
+from java import dynamic_proxy
 
 from .internal.pickers import PickerBase
 
@@ -43,7 +42,7 @@ def get_value(self):
     def set_value(self, value):
         self.native.setText(value.isoformat())
         self._dialog.updateDate(value.year, value.month - 1, value.day)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_min_date(self):
         return py_date(self._picker.getMinDate())
diff --git a/android/src/toga_android/widgets/detailedlist.py b/android/src/toga_android/widgets/detailedlist.py
index bdcc487eb8..ac439159b7 100644
--- a/android/src/toga_android/widgets/detailedlist.py
+++ b/android/src/toga_android/widgets/detailedlist.py
@@ -1,15 +1,13 @@
 from dataclasses import dataclass
 
-from androidx.swiperefreshlayout.widget import SwipeRefreshLayout
-from java import dynamic_proxy
-from travertino.size import at_least
-
 from android import R
 from android.app import AlertDialog
 from android.content import DialogInterface
 from android.graphics import Rect
 from android.view import Gravity, View
 from android.widget import ImageView, LinearLayout, RelativeLayout, ScrollView, TextView
+from androidx.swiperefreshlayout.widget import SwipeRefreshLayout
+from java import dynamic_proxy
 
 from .base import Widget
 
@@ -22,7 +20,7 @@ def __init__(self, impl, row_number):
 
     def onClick(self, _view):
         self.impl._set_selection(self.row_number)
-        self.impl.interface.on_select(None)
+        self.impl.interface.on_select()
 
 
 @dataclass
@@ -41,7 +39,7 @@ def __init__(self, impl, row_number):
 
     def onLongClick(self, _view):
         self.impl._set_selection(self.row_number)
-        self.impl.interface.on_select(None)
+        self.impl.interface.on_select()
 
         actions = [
             action
@@ -77,7 +75,7 @@ def __init__(self, actions, row):
         self.row = row
 
     def onClick(self, dialog, which):
-        self.actions[which].handler(None, row=self.row)
+        self.actions[which].handler(row=self.row)
 
 
 class OnRefreshListener(dynamic_proxy(SwipeRefreshLayout.OnRefreshListener)):
@@ -86,7 +84,7 @@ def __init__(self, interface):
         self._interface = interface
 
     def onRefresh(self):
-        self._interface.on_refresh(None)
+        self._interface.on_refresh()
 
 
 class DetailedList(Widget):
@@ -244,7 +242,3 @@ def scroll_to_row(self, row):
             hit_rect,
             True,  # Immediate, not animated
         )
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
diff --git a/android/src/toga_android/widgets/divider.py b/android/src/toga_android/widgets/divider.py
new file mode 100644
index 0000000000..3c856abac2
--- /dev/null
+++ b/android/src/toga_android/widgets/divider.py
@@ -0,0 +1,42 @@
+from android.graphics import Color
+from android.view import View
+from android.widget import LinearLayout
+from travertino.size import at_least
+
+from .base import Widget
+
+
+class Divider(Widget):
+    def create(self):
+        self.native = View(self._native_activity)
+
+        # Background color needs to be set or else divider will not be visible.
+        self.native.setBackgroundColor(Color.LTGRAY)
+
+        self._direction = self.interface.HORIZONTAL
+
+    def set_background_color(self, value):
+        self.set_background_simple(value)
+
+    def get_direction(self):
+        return self._direction
+
+    def set_direction(self, value):
+        self._direction = value
+
+        if value == self.interface.VERTICAL:
+            # Set the height for a vertical divider
+            params = LinearLayout.LayoutParams(1, self.interface._MIN_HEIGHT)
+        else:
+            # Set the width for a horizontal divider
+            params = LinearLayout.LayoutParams(self.interface._MIN_WIDTH, 1)
+
+        self.native.setLayoutParams(params)
+
+    def rehint(self):
+        if self.get_direction() == self.interface.VERTICAL:
+            self.interface.intrinsic.width = 1
+            self.interface.intrinsic.height = at_least(self.native.getHeight())
+        else:
+            self.interface.intrinsic.width = at_least(self.native.getWidth())
+            self.interface.intrinsic.height = 1
diff --git a/android/src/toga_android/widgets/imageview.py b/android/src/toga_android/widgets/imageview.py
index e70bd38392..6f92541793 100644
--- a/android/src/toga_android/widgets/imageview.py
+++ b/android/src/toga_android/widgets/imageview.py
@@ -1,4 +1,7 @@
+from decimal import ROUND_UP
+
 from android.widget import ImageView as A_ImageView
+
 from toga.widgets.imageview import rehint_imageview
 
 from .base import Widget
@@ -20,7 +23,7 @@ def set_image(self, image):
 
     def rehint(self):
         # User specified sizes are in "pixels", which is DP;
-        # we need to convert all sizes into SP.
+        # we need to convert all sizes into physical pixels.
         dpi = self.native.getContext().getResources().getDisplayMetrics().densityDpi
         # Toga needs to know how the current DPI compares to the platform default,
         # which is 160: https://developer.android.com/training/multiscreen/screendensities
@@ -29,8 +32,8 @@ def rehint(self):
         width, height, aspect_ratio = rehint_imageview(
             image=self.interface.image, style=self.interface.style, scale=scale
         )
-        self.interface.intrinsic.width = width
-        self.interface.intrinsic.height = height
+        self.interface.intrinsic.width = self.scale_out(width, ROUND_UP)
+        self.interface.intrinsic.height = self.scale_out(height, ROUND_UP)
         if aspect_ratio is not None:
             self.native.setScaleType(A_ImageView.ScaleType.FIT_CENTER)
         else:
diff --git a/android/src/toga_android/widgets/internal/pickers.py b/android/src/toga_android/widgets/internal/pickers.py
index 470f1b05e5..61e00a1d46 100644
--- a/android/src/toga_android/widgets/internal/pickers.py
+++ b/android/src/toga_android/widgets/internal/pickers.py
@@ -1,10 +1,10 @@
 from abc import ABC, abstractmethod
-
-from java import dynamic_proxy
-from travertino.size import at_least
+from decimal import ROUND_UP
 
 from android.view import View
 from android.widget import EditText
+from java import dynamic_proxy
+from travertino.size import at_least
 
 from ..label import TextViewWidget
 
@@ -43,4 +43,6 @@ def create(self):
     def rehint(self):
         self.interface.intrinsic.width = at_least(300)
         self.native.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED)
-        self.interface.intrinsic.height = self.native.getMeasuredHeight()
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.getMeasuredHeight(), ROUND_UP
+        )
diff --git a/android/src/toga_android/widgets/label.py b/android/src/toga_android/widgets/label.py
index 756fa51e0c..5737514ae6 100644
--- a/android/src/toga_android/widgets/label.py
+++ b/android/src/toga_android/widgets/label.py
@@ -1,10 +1,12 @@
-from travertino.size import at_least
+from decimal import ROUND_UP
 
 from android.os import Build
 from android.text import Layout
 from android.util import TypedValue
 from android.view import Gravity, View
 from android.widget import TextView
+from travertino.size import at_least
+
 from toga.constants import JUSTIFY
 from toga_android.colors import native_color
 
@@ -68,13 +70,15 @@ def rehint(self):
         # This is the height with word-wrapping disabled.
         self.native.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED)
         min_height = self.native.getMeasuredHeight()
-        self.interface.intrinsic.height = min_height
+        self.interface.intrinsic.height = self.scale_out(min_height, ROUND_UP)
         # Ask it how wide it would be if it had to be the minimum height.
         self.native.measure(
             View.MeasureSpec.UNSPECIFIED,
             View.MeasureSpec.makeMeasureSpec(min_height, View.MeasureSpec.AT_MOST),
         )
-        self.interface.intrinsic.width = at_least(self.native.getMeasuredWidth())
+        self.interface.intrinsic.width = self.scale_out(
+            at_least(self.native.getMeasuredWidth()), ROUND_UP
+        )
 
     def set_alignment(self, value):
         self.set_textview_alignment(value, Gravity.TOP)
diff --git a/android/src/toga_android/widgets/multilinetextinput.py b/android/src/toga_android/widgets/multilinetextinput.py
index a3ee4a1591..0f876c6136 100644
--- a/android/src/toga_android/widgets/multilinetextinput.py
+++ b/android/src/toga_android/widgets/multilinetextinput.py
@@ -1,7 +1,6 @@
-from travertino.size import at_least
-
 from android.text import InputType
 from android.view import Gravity
+from travertino.size import at_least
 
 from .textinput import TextInput
 
@@ -13,7 +12,7 @@ def create(self):
         )
 
     def _on_change(self):
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def _on_confirm(self):  # pragma: nocover
         pass  # The interface doesn't support this event.
@@ -27,6 +26,7 @@ def _on_lose_focus(self):
     def set_alignment(self, value):
         self.set_textview_alignment(value, Gravity.TOP)
 
+    # This method is necessary to override the TextInput base class.
     def rehint(self):
         self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
         self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
diff --git a/android/src/toga_android/widgets/numberinput.py b/android/src/toga_android/widgets/numberinput.py
index e91050e8e2..8ff2ce79c9 100644
--- a/android/src/toga_android/widgets/numberinput.py
+++ b/android/src/toga_android/widgets/numberinput.py
@@ -1,6 +1,7 @@
 from decimal import InvalidOperation
 
 from android.text import InputType
+
 from toga.widgets.numberinput import _clean_decimal
 
 from .textinput import TextInput
@@ -33,7 +34,7 @@ def set_min_value(self, value):
         pass  # This backend doesn't support stepped increments.
 
     def _on_change(self):
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def _on_confirm(self):  # pragma: nocover
         pass  # The interface doesn't support this event.
diff --git a/android/src/toga_android/widgets/progressbar.py b/android/src/toga_android/widgets/progressbar.py
index 539f1ce1d6..2567537be3 100644
--- a/android/src/toga_android/widgets/progressbar.py
+++ b/android/src/toga_android/widgets/progressbar.py
@@ -1,4 +1,4 @@
-from travertino.size import at_least
+from decimal import ROUND_UP
 
 from android import R
 from android.view import View
@@ -93,5 +93,6 @@ def rehint(self):
             View.MeasureSpec.UNSPECIFIED,
             View.MeasureSpec.UNSPECIFIED,
         )
-        self.interface.intrinsic.width = at_least(self.native.getMeasuredWidth())
-        self.interface.intrinsic.height = self.native.getMeasuredHeight()
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.getMeasuredHeight(), ROUND_UP
+        )
diff --git a/android/src/toga_android/widgets/scrollcontainer.py b/android/src/toga_android/widgets/scrollcontainer.py
index 1e727774f4..193f29a247 100644
--- a/android/src/toga_android/widgets/scrollcontainer.py
+++ b/android/src/toga_android/widgets/scrollcontainer.py
@@ -1,10 +1,8 @@
 from decimal import ROUND_DOWN
 
-from java import dynamic_proxy
-from travertino.size import at_least
-
 from android.view import Gravity, View
 from android.widget import HorizontalScrollView, LinearLayout, ScrollView
+from java import dynamic_proxy
 
 from ..container import Container
 from .base import Widget
@@ -28,7 +26,7 @@ def __init__(self, impl):
         self.impl = impl
 
     def onScrollChange(self, view, new_x, new_y, old_x, old_y):
-        self.impl.interface.on_scroll(None)
+        self.impl.interface.on_scroll()
 
 
 class ScrollContainer(Widget, Container):
@@ -104,7 +102,3 @@ def set_position(self, horizontal_position, vertical_position):
 
     def set_background_color(self, value):
         self.set_background_simple(value)
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(0)
-        self.interface.intrinsic.height = at_least(0)
diff --git a/android/src/toga_android/widgets/selection.py b/android/src/toga_android/widgets/selection.py
index 2e79e93382..cddd649f5f 100644
--- a/android/src/toga_android/widgets/selection.py
+++ b/android/src/toga_android/widgets/selection.py
@@ -1,9 +1,9 @@
-from java import dynamic_proxy
-from travertino.size import at_least
+from decimal import ROUND_UP
 
 from android import R
 from android.view import View
 from android.widget import AdapterView, ArrayAdapter, Spinner
+from java import dynamic_proxy
 
 from .base import Widget
 
@@ -36,7 +36,7 @@ def create(self):
     # the change, and use self.last_selection to prevent duplication.
     def on_change(self, index):
         if index != self.last_selection:
-            self.interface.on_change(None)
+            self.interface.on_change()
             self.last_selection = index
 
     def insert(self, index, item):
@@ -69,7 +69,7 @@ def remove(self, index, item=None):
                 self.select_item(self.last_selection)
 
         if removed_selection:
-            self.interface.on_change(None)
+            self.interface.on_change()
 
     def select_item(self, index, item=None):
         self.native.setSelection(index)
@@ -85,5 +85,6 @@ def clear(self):
 
     def rehint(self):
         self.native.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED)
-        self.interface.intrinsic.width = at_least(self.native.getMeasuredWidth())
-        self.interface.intrinsic.height = self.native.getMeasuredHeight()
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.getMeasuredHeight(), ROUND_UP
+        )
diff --git a/android/src/toga_android/widgets/slider.py b/android/src/toga_android/widgets/slider.py
index 6f75168977..12a263b152 100644
--- a/android/src/toga_android/widgets/slider.py
+++ b/android/src/toga_android/widgets/slider.py
@@ -1,10 +1,11 @@
-from java import dynamic_proxy
-from travertino.size import at_least
+from decimal import ROUND_UP
 
-import toga
 from android import R
 from android.view import View
 from android.widget import SeekBar
+from java import dynamic_proxy
+
+import toga
 
 from .base import Widget
 
@@ -24,10 +25,10 @@ def onProgressChanged(self, _view, _progress, _from_user):
         self.impl.on_change()
 
     def onStartTrackingTouch(self, native_seekbar):
-        self.impl.interface.on_press(None)
+        self.impl.interface.on_press()
 
     def onStopTrackingTouch(self, native_seekbar):
-        self.impl.interface.on_release(None)
+        self.impl.interface.on_release()
 
 
 class Slider(Widget, toga.widgets.slider.IntSliderImpl):
@@ -67,5 +68,6 @@ def _load_tick_drawable(self):
 
     def rehint(self):
         self.native.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED)
-        self.interface.intrinsic.width = at_least(self.native.getMeasuredWidth())
-        self.interface.intrinsic.height = self.native.getMeasuredHeight()
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.getMeasuredHeight(), ROUND_UP
+        )
diff --git a/android/src/toga_android/widgets/switch.py b/android/src/toga_android/widgets/switch.py
index e843cd94bd..d1202171e1 100644
--- a/android/src/toga_android/widgets/switch.py
+++ b/android/src/toga_android/widgets/switch.py
@@ -1,8 +1,9 @@
-from java import dynamic_proxy
-from travertino.size import at_least
+from decimal import ROUND_UP
 
 from android.view import View
 from android.widget import CompoundButton, Switch as A_Switch
+from java import dynamic_proxy
+from travertino.size import at_least
 
 from .label import TextViewWidget
 
@@ -13,7 +14,7 @@ def __init__(self, impl):
         self._impl = impl
 
     def onCheckedChanged(self, _button, _checked):
-        self._impl.interface.on_change(None)
+        self._impl.interface.on_change()
 
 
 class Switch(TextViewWidget):
@@ -44,5 +45,9 @@ def set_value(self, value):
 
     def rehint(self):
         self.native.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED)
-        self.interface.intrinsic.width = at_least(self.native.getMeasuredWidth())
-        self.interface.intrinsic.height = self.native.getMeasuredHeight()
+        self.interface.intrinsic.width = self.scale_out(
+            at_least(self.native.getMeasuredWidth()), ROUND_UP
+        )
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.getMeasuredHeight(), ROUND_UP
+        )
diff --git a/android/src/toga_android/widgets/table.py b/android/src/toga_android/widgets/table.py
index 849addeff0..72cdfd724f 100644
--- a/android/src/toga_android/widgets/table.py
+++ b/android/src/toga_android/widgets/table.py
@@ -1,13 +1,12 @@
 from warnings import warn
 
-from java import dynamic_proxy
-from travertino.size import at_least
-
-import toga
 from android import R
 from android.graphics import Rect, Typeface
 from android.view import Gravity, View
 from android.widget import LinearLayout, ScrollView, TableLayout, TableRow, TextView
+from java import dynamic_proxy
+
+import toga
 
 from .base import Widget
 from .label import set_textview_font
@@ -28,7 +27,7 @@ def onClick(self, view):
         else:
             self.impl.clear_selection()
             self.impl.add_selection(tr_id, view)
-        self.impl.interface.on_select(None)
+        self.impl.interface.on_select()
 
 
 class TogaOnLongClickListener(dynamic_proxy(View.OnLongClickListener)):
@@ -40,8 +39,8 @@ def onLongClick(self, view):
         self.impl.clear_selection()
         index = view.getId()
         self.impl.add_selection(index, view)
-        self.impl.interface.on_select(None)
-        self.impl.interface.on_activate(None, row=self.impl.interface.data[index])
+        self.impl.interface.on_select()
+        self.impl.interface.on_activate(row=self.impl.interface.data[index])
         return True
 
 
@@ -221,7 +220,3 @@ def set_background_color(self, value):
     def set_font(self, font):
         self._font_impl = font._impl
         self.change_source(self.interface.data)
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
diff --git a/android/src/toga_android/widgets/textinput.py b/android/src/toga_android/widgets/textinput.py
index 24d1529026..b6c1c90c56 100644
--- a/android/src/toga_android/widgets/textinput.py
+++ b/android/src/toga_android/widgets/textinput.py
@@ -1,9 +1,10 @@
-from java import dynamic_proxy
-from travertino.size import at_least
+from decimal import ROUND_UP
 
 from android.text import InputType, TextWatcher
 from android.view import Gravity, View
 from android.widget import EditText
+from java import dynamic_proxy
+
 from toga_android.keys import toga_key
 
 from .label import TextViewWidget
@@ -110,19 +111,20 @@ def is_valid(self):
         return self.native.getError() is None
 
     def _on_change(self):
-        self.interface.on_change(None)
+        self.interface.on_change()
         self.interface._validate()
 
     def _on_confirm(self):
-        self.interface.on_confirm(None)
+        self.interface.on_confirm()
 
     def _on_gain_focus(self):
-        self.interface.on_gain_focus(None)
+        self.interface.on_gain_focus()
 
     def _on_lose_focus(self):
-        self.interface.on_lose_focus(None)
+        self.interface.on_lose_focus()
 
     def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
         self.native.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED)
-        self.interface.intrinsic.height = self.native.getMeasuredHeight()
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.getMeasuredHeight(), ROUND_UP
+        )
diff --git a/android/src/toga_android/widgets/timeinput.py b/android/src/toga_android/widgets/timeinput.py
index 05d9744ae9..7c065c0d8b 100644
--- a/android/src/toga_android/widgets/timeinput.py
+++ b/android/src/toga_android/widgets/timeinput.py
@@ -1,9 +1,8 @@
 from datetime import time
 
-from java import dynamic_proxy
-
 from android import R
 from android.app import TimePickerDialog
+from java import dynamic_proxy
 
 from .internal.pickers import PickerBase
 
@@ -39,7 +38,7 @@ def get_value(self):
     def set_value(self, value):
         self.native.setText(value.isoformat(timespec="minutes"))
         self._dialog.updateTime(value.hour, value.minute)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_min_time(self):
         return self._min_time
diff --git a/android/src/toga_android/widgets/webview.py b/android/src/toga_android/widgets/webview.py
index 343fadd954..25dcbda30d 100644
--- a/android/src/toga_android/widgets/webview.py
+++ b/android/src/toga_android/widgets/webview.py
@@ -1,9 +1,8 @@
 import json
 
+from android.webkit import ValueCallback, WebView as A_WebView, WebViewClient
 from java import dynamic_proxy
-from travertino.size import at_least
 
-from android.webkit import ValueCallback, WebView as A_WebView, WebViewClient
 from toga.widgets.webview import JavaScriptResult
 
 from .base import Widget
@@ -81,7 +80,3 @@ def evaluate_javascript(self, javascript, on_result=None):
             javascript, ReceiveString(result.future, on_result)
         )
         return result
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
diff --git a/android/src/toga_android/window.py b/android/src/toga_android/window.py
index 88fc0fd77b..ffd523a7d1 100644
--- a/android/src/toga_android/window.py
+++ b/android/src/toga_android/window.py
@@ -1,9 +1,13 @@
 from decimal import ROUND_UP
 
-from java import dynamic_proxy
-
 from android import R
+from android.graphics import (
+    Bitmap,
+    Canvas as A_Canvas,
+)
 from android.view import ViewTreeObserver
+from java import dynamic_proxy
+from java.io import ByteArrayOutputStream
 
 from .container import Container
 
@@ -66,7 +70,7 @@ def set_size(self, size):
         pass
 
     def create_toolbar(self):
-        pass
+        self.app.native.invalidateOptionsMenu()
 
     def show(self):
         pass
@@ -98,3 +102,17 @@ def close(self):
 
     def set_full_screen(self, is_full_screen):
         self.interface.factory.not_implemented("Window.set_full_screen()")
+
+    def get_image_data(self):
+        bitmap = Bitmap.createBitmap(
+            self.native_content.getWidth(),
+            self.native_content.getHeight(),
+            Bitmap.Config.ARGB_8888,
+        )
+        canvas = A_Canvas(bitmap)
+        # TODO: Need to draw window background as well as the content.
+        self.native_content.draw(canvas)
+
+        stream = ByteArrayOutputStream()
+        bitmap.compress(Bitmap.CompressFormat.PNG, 0, stream)
+        return bytes(stream.toByteArray())
diff --git a/android/tests/test_implementation.py b/android/tests/test_implementation.py
deleted file mode 100644
index 7c3f93dfb9..0000000000
--- a/android/tests/test_implementation.py
+++ /dev/null
@@ -1,13 +0,0 @@
-import os
-
-from toga_dummy import test_implementation
-
-globals().update(
-    test_implementation.create_impl_tests(
-        os.path.abspath(
-            os.path.join(
-                os.path.dirname(os.path.dirname(__file__)), "src", "toga_android"
-            )
-        )
-    )
-)
diff --git a/android/tests_backend/app.py b/android/tests_backend/app.py
index 30bed800b1..76365fcc4d 100644
--- a/android/tests_backend/app.py
+++ b/android/tests_backend/app.py
@@ -1,17 +1,26 @@
 from pathlib import Path
 
+from android import R
 from org.beeware.android import MainActivity
+from pytest import xfail
+
+from toga import Group
 
 from .probe import BaseProbe
+from .window import WindowProbe
 
 
 class AppProbe(BaseProbe):
+    supports_key = False
+
     def __init__(self, app):
         super().__init__(app)
-        assert isinstance(self.app._impl.native, MainActivity)
+        self.native = self.app._impl.native
+        self.main_window_probe = WindowProbe(self.app, app.main_window)
+        assert isinstance(self.native, MainActivity)
 
     def get_app_context(self):
-        return self.app._impl.native.getApplicationContext()
+        return self.native.getApplicationContext()
 
     @property
     def config_path(self):
@@ -28,3 +37,72 @@ def cache_path(self):
     @property
     def logs_path(self):
         return Path(self.get_app_context().getFilesDir().getPath()) / "log"
+
+    def _menu_item(self, path):
+        menu = self.main_window_probe._native_menu()
+        for i_path, label in enumerate(path):
+            if i_path == 0 and label == Group.COMMANDS.text:
+                continue
+
+            for i_item in range(menu.size()):
+                item = menu.getItem(i_item)
+                assert not item.requestsActionButton()
+                if item.getTitle() == label and not item.requiresActionButton():
+                    break
+            else:
+                raise AssertionError(f"no item named {path[:i_path+1]}")
+
+            if i_path < len(path) - 1:
+                # Simulate opening the submenu.
+                assert self.native.onOptionsItemSelected(item) is False
+                menu = item.getSubMenu()
+                assert menu is not None
+
+        return item
+
+    def _activate_menu_item(self, path):
+        assert self.native.onOptionsItemSelected(self._menu_item(path))
+
+    def activate_menu_exit(self):
+        xfail("This backend doesn't have an exit command")
+
+    def activate_menu_about(self):
+        self._activate_menu_item(["About Toga Testbed"])
+
+    async def close_about_dialog(self):
+        await self.main_window_probe.close_info_dialog(None)
+
+    def activate_menu_visit_homepage(self):
+        xfail("This backend doesn't have a visit homepage command")
+
+    def assert_menu_item(self, path, *, enabled=True):
+        assert self._menu_item(path).isEnabled() == enabled
+
+    def assert_system_menus(self):
+        self.assert_menu_item(["About Toga Testbed"])
+
+    def activate_menu_close_window(self):
+        xfail("This backend doesn't have a window management menu")
+
+    def activate_menu_close_all_windows(self):
+        xfail("This backend doesn't have a window management menu")
+
+    def activate_menu_minimize(self):
+        xfail("This backend doesn't have a window management menu")
+
+    def enter_background(self):
+        xfail(
+            "This is possible (https://stackoverflow.com/a/7071289), but there's no "
+            "easy way to bring it to the foreground again"
+        )
+
+    def enter_foreground(self):
+        xfail("See enter_background")
+
+    def terminate(self):
+        xfail("Can't simulate this action without killing the app")
+
+    def rotate(self):
+        self.native.findViewById(
+            R.id.content
+        ).getViewTreeObserver().dispatchOnGlobalLayout()
diff --git a/android/tests_backend/fonts.py b/android/tests_backend/fonts.py
index 600444add0..6a0ddddf02 100644
--- a/android/tests_backend/fonts.py
+++ b/android/tests_backend/fonts.py
@@ -1,12 +1,12 @@
 from concurrent.futures import ThreadPoolExecutor
 
+from android.graphics import Typeface
+from android.graphics.fonts import FontFamily
+from android.util import TypedValue
 from fontTools.ttLib import TTFont
 from java import jint
 from java.lang import Integer, Long
 
-from android.graphics import Typeface
-from android.graphics.fonts import FontFamily
-from android.util import TypedValue
 from toga.fonts import (
     BOLD,
     ITALIC,
diff --git a/android/tests_backend/icons.py b/android/tests_backend/icons.py
index 7e09968550..c436051a80 100644
--- a/android/tests_backend/icons.py
+++ b/android/tests_backend/icons.py
@@ -1,5 +1,4 @@
 import pytest
-
 from android.graphics import Bitmap
 
 from .probe import BaseProbe
diff --git a/android/tests_backend/probe.py b/android/tests_backend/probe.py
index fc8c458e79..d21380ee43 100644
--- a/android/tests_backend/probe.py
+++ b/android/tests_backend/probe.py
@@ -1,11 +1,11 @@
 import asyncio
 
-from java import dynamic_proxy
-from org.beeware.android import MainActivity
-
 from android import R
 from android.view import View, ViewTreeObserver, WindowManagerGlobal
 from android.widget import Button
+from java import dynamic_proxy
+from org.beeware.android import MainActivity
+from pytest import approx
 
 
 class LayoutListener(dynamic_proxy(ViewTreeObserver.OnGlobalLayoutListener)):
@@ -89,7 +89,14 @@ async def redraw(self, message=None, delay=0):
             print("Redraw timed out")
 
         if self.app.run_slow:
-            delay = min(delay, 1)
+            delay = max(delay, 1)
         if delay:
             print("Waiting for redraw" if message is None else message)
             await asyncio.sleep(delay)
+
+    def assert_image_size(self, image_size, size):
+        # Sizes are approximate because of scaling inconsistencies.
+        assert image_size == (
+            approx(size[0] * self.scale_factor, abs=2),
+            approx(size[1] * self.scale_factor, abs=2),
+        )
diff --git a/android/tests_backend/widgets/base.py b/android/tests_backend/widgets/base.py
index 67193ec22f..123c7b8d1c 100644
--- a/android/tests_backend/widgets/base.py
+++ b/android/tests_backend/widgets/base.py
@@ -1,8 +1,6 @@
 import asyncio
 
 import pytest
-from pytest import approx
-
 from android.graphics.drawable import (
     ColorDrawable,
     DrawableContainer,
@@ -11,6 +9,7 @@
 )
 from android.os import Build, SystemClock
 from android.view import MotionEvent, View, ViewGroup
+
 from toga.colors import TRANSPARENT
 from toga.style.pack import JUSTIFY, LEFT
 
@@ -86,12 +85,12 @@ def assert_layout(self, size, position):
         # Size and position is as expected. Values must be scaled from DP, and
         # compared inexactly due to pixel scaling
         assert (
-            approx(self.native.getWidth() / self.scale_factor, rel=0.01),
-            approx(self.native.getHeight() / self.scale_factor, rel=0.01),
+            pytest.approx(self.native.getWidth() / self.scale_factor, rel=0.01),
+            pytest.approx(self.native.getHeight() / self.scale_factor, rel=0.01),
         ) == size
         assert (
-            approx(self.native.getLeft() / self.scale_factor, rel=0.01),
-            approx(self.native.getTop() / self.scale_factor, rel=0.01),
+            pytest.approx(self.native.getLeft() / self.scale_factor, rel=0.01),
+            pytest.approx(self.native.getTop() / self.scale_factor, rel=0.01),
         ) == position
 
     @property
diff --git a/android/tests_backend/widgets/canvas.py b/android/tests_backend/widgets/canvas.py
index 380bc9c3f2..55fc16f15d 100644
--- a/android/tests_backend/widgets/canvas.py
+++ b/android/tests_backend/widgets/canvas.py
@@ -1,11 +1,10 @@
 from io import BytesIO
 
 import pytest
-from org.beeware.android import DrawHandlerView
-from PIL import Image
-
 from android.os import SystemClock
 from android.view import MotionEvent
+from org.beeware.android import DrawHandlerView
+from PIL import Image
 
 from .base import SimpleProbe
 
@@ -21,10 +20,6 @@ def reference_variant(self, reference):
     def get_image(self):
         return Image.open(BytesIO(self.impl.get_image_data()))
 
-    def assert_image_size(self, image, width, height):
-        assert image.width == width * self.scale_factor
-        assert image.height == height * self.scale_factor
-
     def motion_event(self, action, x, y):
         time = SystemClock.uptimeMillis()
         super().motion_event(
diff --git a/android/tests_backend/widgets/detailedlist.py b/android/tests_backend/widgets/detailedlist.py
index 2921e14be2..2e42c7b28e 100644
--- a/android/tests_backend/widgets/detailedlist.py
+++ b/android/tests_backend/widgets/detailedlist.py
@@ -1,7 +1,5 @@
 import asyncio
 
-from androidx.swiperefreshlayout.widget import SwipeRefreshLayout
-
 from android.os import SystemClock
 from android.view import KeyEvent
 from android.widget import (
@@ -12,6 +10,7 @@
     ScrollView,
     TextView,
 )
+from androidx.swiperefreshlayout.widget import SwipeRefreshLayout
 
 from .base import SimpleProbe, find_view_by_type
 
diff --git a/android/tests_backend/widgets/divider.py b/android/tests_backend/widgets/divider.py
new file mode 100644
index 0000000000..1526ba2849
--- /dev/null
+++ b/android/tests_backend/widgets/divider.py
@@ -0,0 +1,7 @@
+from java import jclass
+
+from .base import SimpleProbe
+
+
+class DividerProbe(SimpleProbe):
+    native_class = jclass("android.view.View")
diff --git a/android/tests_backend/widgets/label.py b/android/tests_backend/widgets/label.py
index 93c5145f33..f74ccb6562 100644
--- a/android/tests_backend/widgets/label.py
+++ b/android/tests_backend/widgets/label.py
@@ -1,6 +1,5 @@
-from java import jclass
-
 from android.os import Build
+from java import jclass
 
 from .base import SimpleProbe
 from .properties import toga_alignment, toga_color
diff --git a/android/tests_backend/widgets/properties.py b/android/tests_backend/widgets/properties.py
index c202caecbe..356fb78552 100644
--- a/android/tests_backend/widgets/properties.py
+++ b/android/tests_backend/widgets/properties.py
@@ -1,9 +1,9 @@
-from java import jint
-
 from android.graphics import Color
 from android.os import Build
 from android.text import Layout
 from android.view import Gravity
+from java import jint
+
 from toga.colors import TRANSPARENT, rgba
 from toga.constants import BOTTOM, CENTER, JUSTIFY, LEFT, RIGHT, TOP
 
diff --git a/android/tests_backend/widgets/selection.py b/android/tests_backend/widgets/selection.py
index 8925cf272f..390cd90004 100644
--- a/android/tests_backend/widgets/selection.py
+++ b/android/tests_backend/widgets/selection.py
@@ -1,6 +1,5 @@
-from pytest import xfail
-
 from android.widget import Spinner
+from pytest import xfail
 
 from .base import SimpleProbe
 
diff --git a/android/tests_backend/widgets/slider.py b/android/tests_backend/widgets/slider.py
index 32f24ea085..4847e2fd6d 100644
--- a/android/tests_backend/widgets/slider.py
+++ b/android/tests_backend/widgets/slider.py
@@ -1,7 +1,6 @@
-from java import jclass
-
 from android.os import Build, SystemClock
 from android.view import MotionEvent
+from java import jclass
 
 from .base import SimpleProbe
 
diff --git a/android/tests_backend/widgets/table.py b/android/tests_backend/widgets/table.py
index d27084314f..aea21ed8a0 100644
--- a/android/tests_backend/widgets/table.py
+++ b/android/tests_backend/widgets/table.py
@@ -1,5 +1,4 @@
 import pytest
-
 from android.widget import ScrollView, TableLayout, TextView
 
 from .base import SimpleProbe
diff --git a/android/tests_backend/widgets/textinput.py b/android/tests_backend/widgets/textinput.py
index 149765bbea..2bbc62c4f9 100644
--- a/android/tests_backend/widgets/textinput.py
+++ b/android/tests_backend/widgets/textinput.py
@@ -1,10 +1,9 @@
 import pytest
-from java import jclass
-
 from android.os import SystemClock
 from android.text import InputType
 from android.view import KeyEvent
 from android.view.inputmethod import EditorInfo
+from java import jclass
 
 from .label import LabelProbe
 
diff --git a/android/tests_backend/widgets/timeinput.py b/android/tests_backend/widgets/timeinput.py
index 4c784e480f..0edd7f6044 100644
--- a/android/tests_backend/widgets/timeinput.py
+++ b/android/tests_backend/widgets/timeinput.py
@@ -1,7 +1,7 @@
 import re
 from datetime import time
 
-from android import R as android_R
+from android import R
 from android.widget import TimePicker
 
 from .base import find_view_by_type
@@ -34,9 +34,7 @@ async def _change_dialog_value(self, delta):
 
     @property
     def _picker(self):
-        picker = find_view_by_type(
-            self._dialog.findViewById(android_R.id.content), TimePicker
-        )
+        picker = find_view_by_type(self._dialog.findViewById(R.id.content), TimePicker)
         assert picker is not None
         assert picker.is24HourView()
         return picker
diff --git a/android/tests_backend/window.py b/android/tests_backend/window.py
index 20a9747e01..bc283f43a3 100644
--- a/android/tests_backend/window.py
+++ b/android/tests_backend/window.py
@@ -1,4 +1,5 @@
 import pytest
+from androidx.appcompat import R as appcompat_R
 
 from .probe import BaseProbe
 
@@ -6,6 +7,7 @@
 class WindowProbe(BaseProbe):
     def __init__(self, app, window):
         super().__init__(app)
+        self.native = self.app._impl.native
 
     async def wait_for_window(self, message, minimize=False, full_screen=False):
         await self.redraw(message)
@@ -48,3 +50,40 @@ async def close_open_file_dialog(self, dialog, result, multiple_select):
 
     async def close_select_folder_dialog(self, dialog, result, multiple_select):
         pytest.skip("Select Folder dialog not implemented on Android")
+
+    def _native_menu(self):
+        return self.native.findViewById(appcompat_R.id.action_bar).getMenu()
+
+    def _toolbar_items(self):
+        result = []
+        prev_group = None
+        menu = self._native_menu()
+        for i_item in range(menu.size()):
+            item = menu.getItem(i_item)
+            assert not item.requestsActionButton()
+
+            if item.requiresActionButton():
+                if prev_group and prev_group != item.getGroupId():
+                    # The separator doesn't actually appear, but it keeps the indices
+                    # correct for the tests.
+                    result.append(None)
+                prev_group = item.getGroupId()
+                result.append(item)
+
+        return result
+
+    def has_toolbar(self):
+        return bool(self._toolbar_items())
+
+    def assert_is_toolbar_separator(self, index, section=False):
+        assert self._toolbar_items()[index] is None
+
+    def assert_toolbar_item(self, index, label, tooltip, has_icon, enabled):
+        item = self._toolbar_items()[index]
+        assert item.getTitle() == label
+        # Tooltips are not implemented
+        assert (item.getIcon() is not None) == has_icon
+        assert item.isEnabled() == enabled
+
+    def press_toolbar_button(self, index):
+        self.native.onOptionsItemSelected(self._toolbar_items()[index])
diff --git a/changes/1215.bugfix.rst b/changes/1215.bugfix.rst
deleted file mode 100644
index e4bc5ad084..0000000000
--- a/changes/1215.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Widgets are now removed from windows when the window is closed, preventing a memory leak on window closure.
diff --git a/changes/1235.bugfix.rst b/changes/1235.bugfix.rst
deleted file mode 100644
index ec4c06a7d3..0000000000
--- a/changes/1235.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Android and iOS apps no longer crash if you invoke ``App.hide_cursor()`` or ``App.show_cursor()``.
diff --git a/changes/1723.bugfix.rst b/changes/1723.bugfix.rst
deleted file mode 100644
index a3ca28204a..0000000000
--- a/changes/1723.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-A Selection widget with no items now consistently returns a current value of ``None`` on all platforms.
diff --git a/changes/1767.feature.txt b/changes/1767.feature.txt
deleted file mode 100644
index f53e314286..0000000000
--- a/changes/1767.feature.txt
+++ /dev/null
@@ -1,2 +0,0 @@
-Headings are no longer mandatory for Tree widgets.
-If headings are not provided, the widget will not display its header bar.
diff --git a/changes/1779.bugfix.rst b/changes/1779.bugfix.rst
deleted file mode 100644
index 7008e135e7..0000000000
--- a/changes/1779.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-macOS widget methods that return strings are now guaranteed to return strings, rather than native Objective C string objects.
diff --git a/changes/1837.feature.rst b/changes/1837.feature.rst
deleted file mode 100644
index e9b4941620..0000000000
--- a/changes/1837.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Support for custom font loading was added to the GTK, Cocoa and iOS backends.
diff --git a/changes/1847.feature.rst b/changes/1847.feature.rst
deleted file mode 100644
index 8cc68e68cf..0000000000
--- a/changes/1847.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The testbed app has better diagnostic output when running in test mode.
diff --git a/changes/1849.doc.rst b/changes/1849.doc.rst
deleted file mode 100644
index 6b8dd7b08b..0000000000
--- a/changes/1849.doc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Documentation for application paths was added.
diff --git a/changes/1855.bugfix.rst b/changes/1855.bugfix.rst
deleted file mode 100644
index 46db31d18b..0000000000
--- a/changes/1855.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Webviews on Windows no longer have a black background when they are resized.
diff --git a/changes/1865.misc.rst b/changes/1865.misc.rst
deleted file mode 100644
index a15dd7ff1a..0000000000
--- a/changes/1865.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-PyPI package names were removed as valid spelling words.
diff --git a/changes/1866.bugfix.rst b/changes/1866.bugfix.rst
deleted file mode 100644
index c3abc9d0dc..0000000000
--- a/changes/1866.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Ensure correct value is set for `MultilineTextInput.readonly` for iOS
diff --git a/changes/1867.feature.rst b/changes/1867.feature.rst
deleted file mode 100644
index 98c16c6c7f..0000000000
--- a/changes/1867.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-A new Textual backend was added to support terminal applications.
diff --git a/changes/1868.doc.rst b/changes/1868.doc.rst
deleted file mode 100644
index 469cd25ed5..0000000000
--- a/changes/1868.doc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The contribution guide was expanded to include more suggestions for potential projects, and to explain how the backend tests work.
diff --git a/changes/1872.bugfix.rst b/changes/1872.bugfix.rst
deleted file mode 100644
index 5c00193447..0000000000
--- a/changes/1872.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-A window without an ``on_close`` handler can now be closed using the window frame close button.
diff --git a/changes/1872.feature.rst b/changes/1872.feature.rst
deleted file mode 100644
index cbdbd0eb5e..0000000000
--- a/changes/1872.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Support for determining the currently active window was added to Winforms.
diff --git a/changes/1875.misc.rst b/changes/1875.misc.rst
deleted file mode 100644
index 190c84554d..0000000000
--- a/changes/1875.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/checkout from 3.5.0 to 3.5.2.
diff --git a/changes/1876.feature.rst b/changes/1876.feature.rst
deleted file mode 100644
index 5f567757f0..0000000000
--- a/changes/1876.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Programmatically scrolling to top and bottom in MultilineTextInput is now possible on iOS
diff --git a/changes/1878.bugfix.rst b/changes/1878.bugfix.rst
deleted file mode 100644
index f6a4d57117..0000000000
--- a/changes/1878.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Fixed a startup crash on Android devices older than API level 29 (Android 10).
diff --git a/changes/1879.bugfix.rst b/changes/1879.bugfix.rst
deleted file mode 100644
index c47ecfff95..0000000000
--- a/changes/1879.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Missing value handling on Tables was fixed on Android and Linux.
diff --git a/changes/1880.feature.rst b/changes/1880.feature.rst
deleted file mode 100644
index 1bc205820a..0000000000
--- a/changes/1880.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-A handler has been added for users confirming the contents of a TextInput by pressing Enter/Return.
diff --git a/changes/1881.bugfix.rst b/changes/1881.bugfix.rst
deleted file mode 100644
index d0b1244e14..0000000000
--- a/changes/1881.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Changed spelling to prevent Sphinx spelling error.
diff --git a/changes/1882.misc.rst b/changes/1882.misc.rst
deleted file mode 100644
index 24dd6618eb..0000000000
--- a/changes/1882.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``tox`` commands for building docs now use multi-processing for faster builds.
diff --git a/changes/1886.misc.rst b/changes/1886.misc.rst
deleted file mode 100644
index 98a4438747..0000000000
--- a/changes/1886.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The latest version of ``docformatter``, i.e. v1.6.1, was run to lint all docstrings in Toga.
diff --git a/changes/1887.feature.rst b/changes/1887.feature.rst
deleted file mode 100644
index 9a6030b167..0000000000
--- a/changes/1887.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-An API for setting a window into active focus was added.
diff --git a/changes/1889.misc.rst b/changes/1889.misc.rst
deleted file mode 100644
index 71b65af880..0000000000
--- a/changes/1889.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/setup-python from 4.5.0 to 4.6.0.
diff --git a/changes/1892.bugfix.rst b/changes/1892.bugfix.rst
deleted file mode 100644
index 14168889f6..0000000000
--- a/changes/1892.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-A bug in the gtk backend for `current_window` property was fixed.
diff --git a/changes/1893.feature.rst b/changes/1893.feature.rst
deleted file mode 100644
index a3d87b4ea9..0000000000
--- a/changes/1893.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Widgets now have a `.clear()` method to remove all child widgets.
diff --git a/changes/1894.feature.rst b/changes/1894.feature.rst
deleted file mode 100644
index 63eaef269a..0000000000
--- a/changes/1894.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Winforms now supports hiding and re-showing the app cursor.
diff --git a/changes/1895.misc.rst b/changes/1895.misc.rst
deleted file mode 100644
index 3785d48e9d..0000000000
--- a/changes/1895.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The implementation of ``current_window`` on Winforms was corrected.
diff --git a/changes/1897.doc.rst b/changes/1897.doc.rst
deleted file mode 100644
index 5367252d9a..0000000000
--- a/changes/1897.doc.rst
+++ /dev/null
@@ -1 +0,0 @@
-All code blocks were updated to add a button to copy the relevant contents on to the user's clipboard.
diff --git a/changes/1900.misc.rst b/changes/1900.misc.rst
deleted file mode 100644
index d616e6fe32..0000000000
--- a/changes/1900.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Release processes were changed to use Trusted Publishing.
diff --git a/changes/1901.feature.rst b/changes/1901.feature.rst
deleted file mode 100644
index df25c72d92..0000000000
--- a/changes/1901.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-New ProgressBar and Switch widgets were added to the web platform implementation.
diff --git a/changes/1902.misc.rst b/changes/1902.misc.rst
deleted file mode 100644
index 5679e35d9c..0000000000
--- a/changes/1902.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Moved font measuring logic for GTK from Font class to Canvas widget
diff --git a/changes/1903.feature.rst b/changes/1903.feature.rst
deleted file mode 100644
index a448645944..0000000000
--- a/changes/1903.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Font APIs now have 100% test coverage.
diff --git a/changes/1903.removal.rst b/changes/1903.removal.rst
deleted file mode 100644
index 9deb0249da..0000000000
--- a/changes/1903.removal.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``weight``, ``style`` and ``variant`` arguments for ``Font`` and ``Font.register`` are now keyword-only.
diff --git a/changes/1906.misc.rst b/changes/1906.misc.rst
deleted file mode 100644
index 671ef25abf..0000000000
--- a/changes/1906.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The root user prompt ``#`` has been removed as a prompt match for copying commands from code blocks.
diff --git a/changes/1909.bugfix.rst b/changes/1909.bugfix.rst
deleted file mode 100644
index f6a633067c..0000000000
--- a/changes/1909.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Error handling associated with the creation of creation of Android Intents has been improved.
diff --git a/changes/1913.feature.rst b/changes/1913.feature.rst
deleted file mode 100644
index 4c4ed18a0a..0000000000
--- a/changes/1913.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Missing value handling was added to Trees.
diff --git a/changes/1916.misc.rst b/changes/1916.misc.rst
deleted file mode 100644
index 6aa9d82606..0000000000
--- a/changes/1916.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Installation ordering in tox environment was altered to ensure correct resolution of dependencies.
diff --git a/changes/1917.misc.rst b/changes/1917.misc.rst
deleted file mode 100644
index 248da6ab25..0000000000
--- a/changes/1917.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated ``pre-commit`` hooks to the latest version.
diff --git a/changes/1918.misc.rst b/changes/1918.misc.rst
deleted file mode 100644
index bdedcccfa5..0000000000
--- a/changes/1918.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated dsaltares/fetch-gh-release-asset from 1.1.0 to 1.1.1.
diff --git a/changes/1920.bugfix.rst b/changes/1920.bugfix.rst
deleted file mode 100644
index 547ecc89ae..0000000000
--- a/changes/1920.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-The DetailedList widget on GTK now provides an accurate size hint during layout.
diff --git a/changes/1921.bugfix.rst b/changes/1921.bugfix.rst
deleted file mode 100644
index 52c86fb701..0000000000
--- a/changes/1921.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Apps on Linux no longer segfault if an X Windows display cannot be identified.
diff --git a/changes/1926.misc.rst b/changes/1926.misc.rst
deleted file mode 100644
index 75768c042d..0000000000
--- a/changes/1926.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Dependencies in attic projects were unpinned to avoid spurious dependabot security alerts.
diff --git a/changes/1933.misc.rst b/changes/1933.misc.rst
deleted file mode 100644
index 248da6ab25..0000000000
--- a/changes/1933.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated ``pre-commit`` hooks to the latest version.
diff --git a/changes/1938.feature.rst b/changes/1938.feature.rst
deleted file mode 100644
index 1b4b1de04d..0000000000
--- a/changes/1938.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The MultilineTextInput widget now has 100% test coverage, and complete API documentation.
diff --git a/changes/1938.removal.rst b/changes/1938.removal.rst
deleted file mode 100644
index 6460bbbea3..0000000000
--- a/changes/1938.removal.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``clear()`` method for resetting the value of a MultilineTextInput, TextInput and PasswordInput has been removed. This method was an ambiguous override of the ``clear()`` method on Widget that removed all child nodes. To remove all content from a text input widget, use ``widget.value = ""``.
diff --git a/changes/1944.feature.rst b/changes/1944.feature.rst
deleted file mode 100644
index cedc7c9b58..0000000000
--- a/changes/1944.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The TextInput and PasswordInput widgets now have 100% test coverage, and complete API documentation.
diff --git a/changes/1944.removal.1.rst b/changes/1944.removal.1.rst
deleted file mode 100644
index fd7f331eba..0000000000
--- a/changes/1944.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The argument names used to construct validators have changed. Error message arguments now all end with ``_message``; ``compare_count`` has been renamed ``count``; and ``min_value`` and ``max_value`` have been renamed ``min_length`` and ``max_length``, respectively.
diff --git a/changes/1944.removal.2.rst b/changes/1944.removal.2.rst
deleted file mode 100644
index edb06c6a2e..0000000000
--- a/changes/1944.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ability to perform multiple substring matches in a ``Contains`` validator has been removed.
diff --git a/changes/1944.removal.3.rst b/changes/1944.removal.3.rst
deleted file mode 100644
index 4c5055fae3..0000000000
--- a/changes/1944.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``TextInput.validate`` method has been removed. Validation now happens automatically whenever the ``value`` or ``validators`` properties are changed.
diff --git a/changes/1946.feature.rst b/changes/1946.feature.rst
deleted file mode 100644
index 0d19d9dd40..0000000000
--- a/changes/1946.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The NumberInput widget now has 100% test coverage, and complete API documentation.
diff --git a/changes/1947.bugfix.rst b/changes/1947.bugfix.rst
deleted file mode 100644
index 3a7016b732..0000000000
--- a/changes/1947.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``on_result`` handler is now used by Cocoa file dialogs.
diff --git a/changes/1948.misc.rst b/changes/1948.misc.rst
deleted file mode 100644
index f59c7571f8..0000000000
--- a/changes/1948.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Dialogs were refactored to provide reuse for asynchronous results, and provide full interface/impl separation.
diff --git a/changes/1949.feature.rst b/changes/1949.feature.rst
deleted file mode 100644
index e6f7f1134e..0000000000
--- a/changes/1949.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The WebView widget now has 100% test coverage, and complete API documentation.
diff --git a/changes/1949.removal.1.rst b/changes/1949.removal.1.rst
deleted file mode 100644
index 70f1e709de..0000000000
--- a/changes/1949.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``on_key_down`` handler has been removed from WebView. If you need to catch user input, either use a handler in the embedded Javascript, or create a ``Command`` with a key shortcut.
diff --git a/changes/1949.removal.2.rst b/changes/1949.removal.2.rst
deleted file mode 100644
index 607bdada1a..0000000000
--- a/changes/1949.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``get_dom()`` method on WebView has been removed. This method wasn't implemented on most platforms, and wasn't working on any of the platforms where it *was* implemented, as modern web view implementations don't provide a synchronous API for accessing web content in this way.
diff --git a/changes/1949.removal.3.rst b/changes/1949.removal.3.rst
deleted file mode 100644
index 88ee8ad077..0000000000
--- a/changes/1949.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``evaluate_javascript()`` method on WebView has been modified to work in both synchronous and asynchronous contexts. In a synchronous context you can invoke the method and use a functional ``on_result`` callback to be notified when evaluation is complete. In an asynchronous context, you can await the result.
diff --git a/changes/1949.removal.4.rst b/changes/1949.removal.4.rst
deleted file mode 100644
index 04b5c24a0d..0000000000
--- a/changes/1949.removal.4.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``invoke_javascript()`` method has been removed. All usage of ``invoke_javascript()`` can be replaced with ``evaluate_javascript()``.
diff --git a/changes/1949.removal.5.rst b/changes/1949.removal.5.rst
deleted file mode 100644
index 4840d9beb1..0000000000
--- a/changes/1949.removal.5.rst
+++ /dev/null
@@ -1 +0,0 @@
-The usage of local ``file://`` URLs has been explicitly prohibited. ``file://`` URLs have not been reliable for some time; their usage is now explicitly prohibited.
diff --git a/changes/1950.misc.rst b/changes/1950.misc.rst
deleted file mode 100644
index 9fa62a8b94..0000000000
--- a/changes/1950.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The NavigationView was removed; it wasn't exposed in public API.
diff --git a/changes/1951.feature.rst b/changes/1951.feature.rst
deleted file mode 100644
index a9fe48f668..0000000000
--- a/changes/1951.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The DateInput and TimeInput widgets now have 100% test coverage, and complete API documentation.
diff --git a/changes/1951.removal.1.rst b/changes/1951.removal.1.rst
deleted file mode 100644
index 1ae323e047..0000000000
--- a/changes/1951.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-``DatePicker`` has been renamed ``DateInput``.
diff --git a/changes/1951.removal.2.rst b/changes/1951.removal.2.rst
deleted file mode 100644
index 697d6e1f85..0000000000
--- a/changes/1951.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-``TimePicker`` has been renamed ``TimeInput``.
diff --git a/changes/1952.misc.rst b/changes/1952.misc.rst
deleted file mode 100644
index a6ba419dee..0000000000
--- a/changes/1952.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Type annotations were updated for all widgets that have been audited.
diff --git a/changes/1954.misc.rst b/changes/1954.misc.rst
deleted file mode 100644
index 13f8fc2a61..0000000000
--- a/changes/1954.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/setup-python from 4.6.0 to 4.6.1.
diff --git a/changes/1955.feature.rst b/changes/1955.feature.rst
deleted file mode 100644
index cce0a75039..0000000000
--- a/changes/1955.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The Selection widget now has 100% test coverage and complete API documentation.
diff --git a/changes/1955.removal.1.rst b/changes/1955.removal.1.rst
deleted file mode 100644
index 9064fdce96..0000000000
--- a/changes/1955.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``on_select`` handler on the Selection widget has been renamed ``on_change`` for consistency with other widgets.
diff --git a/changes/1955.removal.2.rst b/changes/1955.removal.2.rst
deleted file mode 100644
index 37dc673205..0000000000
--- a/changes/1955.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``_notify()`` method on data sources has been renamed ``notify()``, reflecting its status as a public API.
diff --git a/changes/1955.removal.3.rst b/changes/1955.removal.3.rst
deleted file mode 100644
index 862c0cdbca..0000000000
--- a/changes/1955.removal.3.rst
+++ /dev/null
@@ -1,2 +0,0 @@
-The ``prepend()`` method was removed from the ``ListSource`` and ``TreeSource`` APIs.
-Calls to ``prepend(...)`` can be replaced with ``insert(0, ...)``.
diff --git a/changes/1955.removal.4.rst b/changes/1955.removal.4.rst
deleted file mode 100644
index ec2d1e50d0..0000000000
--- a/changes/1955.removal.4.rst
+++ /dev/null
@@ -1,5 +0,0 @@
-The ``insert`` and ``append`` APIs on ``ListSource`` and ``TreeSource`` have been
-modified to provide an interface that is closer to that ``list`` API. These methods
-previously accepted a variable list of positional and keyword arguments; these arguments
-should be combined into a single tuple or dictionary. This matches the API provided by
-``__setitem__()``.
diff --git a/changes/1956.feature.rst b/changes/1956.feature.rst
deleted file mode 100644
index 59de21d71f..0000000000
--- a/changes/1956.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ImageView widget now has 100% test coverage, and complete API documentation.
diff --git a/changes/1956.removal.rst b/changes/1956.removal.rst
deleted file mode 100644
index 49c9bce655..0000000000
--- a/changes/1956.removal.rst
+++ /dev/null
@@ -1 +0,0 @@
-Images and ImageViews no longer support loading images from URLs. If you need to display an image from a URL, use a background task to obtain the image data asynchronously, then create the Image and/or set the ImageView ``image`` property on the completion of the asynchronous load.
diff --git a/changes/1958.bugfix.rst b/changes/1958.bugfix.rst
deleted file mode 100644
index a50af370ca..0000000000
--- a/changes/1958.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Pack layout now honors an explicit width/height setting of 0.
diff --git a/changes/1958.removal.1.rst b/changes/1958.removal.1.rst
deleted file mode 100644
index 0a92873e23..0000000000
--- a/changes/1958.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-A row box contained inside a row box will now expand to the full height of its parent, rather than collapsing to the maximum height of the inner box's child content.
diff --git a/changes/1958.removal.2.rst b/changes/1958.removal.2.rst
deleted file mode 100644
index e37636b8ae..0000000000
--- a/changes/1958.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-A column box contained inside a column box will now expand to the full width of its parent, rather than collapsing to the maximum width of the inner box's child content.
diff --git a/changes/1963.misc.rst b/changes/1963.misc.rst
deleted file mode 100644
index f37035e948..0000000000
--- a/changes/1963.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The iOS handler for focus changes was corrected to correctly resign focus.
diff --git a/changes/1964.feature.1.rst b/changes/1964.feature.1.rst
deleted file mode 100644
index ecdf5b3422..0000000000
--- a/changes/1964.feature.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The Paths property of apps now has 100% test coverage, and complete API documentation.
diff --git a/changes/1964.feature.2.rst b/changes/1964.feature.2.rst
deleted file mode 100644
index 1f4d50f228..0000000000
--- a/changes/1964.feature.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-The app paths now include a ``config`` path for storing config files.
diff --git a/changes/1964.removal.1.rst b/changes/1964.removal.1.rst
deleted file mode 100644
index 2945eb7b2f..0000000000
--- a/changes/1964.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The location returned by ``toga.App.paths.app`` is now the folder that contains the Python source file that defines the app class used by the app. If you are using a ``toga.App`` instance directly, this may alter the path that is returned.
diff --git a/changes/1964.removal.2.rst b/changes/1964.removal.2.rst
deleted file mode 100644
index 3dbe9045e2..0000000000
--- a/changes/1964.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-On Winforms, if an application doesn't define an author, an author of ``Unknown`` is now used in application data paths, rather than ``Toga``.
diff --git a/changes/1964.removal.3.rst b/changes/1964.removal.3.rst
deleted file mode 100644
index 22bcae6c19..0000000000
--- a/changes/1964.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-Winforms now returns ``AppData/Local/<Author Name>/<App Name>/Data`` as the user data file location, rather than ``AppData/Local/<Author Name>/<App Name>``.
diff --git a/changes/1964.removal.4.rst b/changes/1964.removal.4.rst
deleted file mode 100644
index b22fe6ab97..0000000000
--- a/changes/1964.removal.4.rst
+++ /dev/null
@@ -1 +0,0 @@
-On Android, the user data folder is now a ``data`` subdirectory of the location returned by ``context.getFilesDir()``, rather than the bare ``context.getFilesDir()`` location.
diff --git a/changes/1964.removal.5.rst b/changes/1964.removal.5.rst
deleted file mode 100644
index debf6198aa..0000000000
--- a/changes/1964.removal.5.rst
+++ /dev/null
@@ -1 +0,0 @@
-GTK now returns ``~/.local/state/appname/log`` as the log file location, rather than ``~/.cache/appname/log``.
diff --git a/changes/1969.feature.rst b/changes/1969.feature.rst
deleted file mode 100644
index c0261629de..0000000000
--- a/changes/1969.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ScrollContainer widget now has 100% test coverage, and complete API documentation.
diff --git a/changes/1972.misc.rst b/changes/1972.misc.rst
deleted file mode 100644
index 05105d7c6e..0000000000
--- a/changes/1972.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/checkout from 3.5.2 to 3.5.3.
diff --git a/changes/1977.misc.rst b/changes/1977.misc.rst
deleted file mode 100644
index 9eb46067a6..0000000000
--- a/changes/1977.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``pyupgrade`` was updated to its latest version.
diff --git a/changes/1980.misc.rst b/changes/1980.misc.rst
deleted file mode 100644
index 36887818c7..0000000000
--- a/changes/1980.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-References to Android system libraries have been modified to use Chaquopy native syntax, rather than Rubicon Java.
diff --git a/changes/1984.feature.rst b/changes/1984.feature.rst
deleted file mode 100644
index caadeee2d1..0000000000
--- a/changes/1984.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The SplitContainer widget now has 100% test coverage, and complete API documentation.
diff --git a/changes/1984.removal.1.rst b/changes/1984.removal.1.rst
deleted file mode 100644
index 8b3e8f37a9..0000000000
--- a/changes/1984.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-Support for SplitContainers with more than 2 panels of content has been removed.
diff --git a/changes/1984.removal.2.rst b/changes/1984.removal.2.rst
deleted file mode 100644
index 7d194c8aa1..0000000000
--- a/changes/1984.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-Support for 3-tuple form of specifying SplitContainer items, used to prevent panels from resizing, has been removed.
diff --git a/changes/1988.misc.rst b/changes/1988.misc.rst
deleted file mode 100644
index 0ac6a013de..0000000000
--- a/changes/1988.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-An error in path instantiation by the web backend was corrected.
diff --git a/changes/1989.misc.rst b/changes/1989.misc.rst
deleted file mode 100644
index 9480ad6111..0000000000
--- a/changes/1989.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The on_webview_load signal when setting the URL to None was deferred to the event loop, rather than being invoked immediately.
diff --git a/changes/1992.feature.rst b/changes/1992.feature.rst
deleted file mode 100644
index 803d761478..0000000000
--- a/changes/1992.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-A more informative error message is returned when a platform backend doesn't support a widget.
diff --git a/changes/1995.feature.rst b/changes/1995.feature.rst
deleted file mode 100644
index 77d89cf247..0000000000
--- a/changes/1995.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The example apps were updated to support being run with ``briefcase run`` on all platforms.
diff --git a/changes/1996.feature.rst b/changes/1996.feature.rst
deleted file mode 100644
index 405bb99826..0000000000
--- a/changes/1996.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The OptionContainer widget now has 100% test coverage, and complete API documentation.
diff --git a/changes/1996.removal.1.rst b/changes/1996.removal.1.rst
deleted file mode 100644
index 119d0bd069..0000000000
--- a/changes/1996.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ability to increment and decrement the current OptionContainer tab was removed. Instead of `container.current_tab += 1`, use `container.current_tab = container.current_tab.index + 1`
diff --git a/changes/1996.removal.2.rst b/changes/1996.removal.2.rst
deleted file mode 100644
index 7b1b2a7c64..0000000000
--- a/changes/1996.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-``OptionContainer.add()``, ``OptionContainer.remove()`` and ``OptionContainer.insert()`` have been removed, due to being ambiguous with base widget methods of the same name. Use the ``OptionContainer.content.append()``, ``OptionContainer.content.remove()`` and ``OptionContainer.content.insert()`` APIs instead.
diff --git a/changes/1996.removal.3.rst b/changes/1996.removal.3.rst
deleted file mode 100644
index cd32b910ab..0000000000
--- a/changes/1996.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``on_select`` handler for OptionContainer no longer receives the ``option`` argument providing the selected tab. Use ``current_tab`` to obtain the currently selected tab.
diff --git a/changes/1998.misc.rst b/changes/1998.misc.rst
deleted file mode 100644
index 977eddaf66..0000000000
--- a/changes/1998.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The reference to ``toga.paths.Paths`` in API Reference was corrected to resolve correctly.
diff --git a/changes/1999.removal.1.rst b/changes/1999.removal.1.rst
deleted file mode 100644
index 8c5f27b7e7..0000000000
--- a/changes/1999.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-``Slider.range`` has been replaced by ``Slider.min`` and ``Slider.max``.
diff --git a/changes/1999.removal.2.rst b/changes/1999.removal.2.rst
deleted file mode 100644
index 3b102fe4ff..0000000000
--- a/changes/1999.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-``NumberInput.min_value`` and ``NumberInput.max_value`` have been renamed ``NumberInput.min`` and ``NumberInput.max``, respectively.
diff --git a/changes/1999.removal.3.rst b/changes/1999.removal.3.rst
deleted file mode 100644
index 8e47bd7180..0000000000
--- a/changes/1999.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-``DatePicker.min_date`` and ``DatePicker.max_date`` has been renamed ``DateInput.min`` and ``DateInput.max``, respectively.
diff --git a/changes/1999.removal.4.rst b/changes/1999.removal.4.rst
deleted file mode 100644
index 3b2264aa6b..0000000000
--- a/changes/1999.removal.4.rst
+++ /dev/null
@@ -1 +0,0 @@
-``TimePicker.min_time`` and ``TimePicker.max_time`` has been renamed ``TimeInput.min`` and ``TimeInput.max``, respectively.
diff --git a/changes/2001.doc.rst b/changes/2001.doc.rst
deleted file mode 100644
index a0b6cbcf3a..0000000000
--- a/changes/2001.doc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Class references were updated to reflect their prefererred import location, rather than location where they are defined in code.
diff --git a/changes/2008.misc.rst b/changes/2008.misc.rst
deleted file mode 100644
index 59d9323c51..0000000000
--- a/changes/2008.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The import for Pyodide's ``create_proxy`` function was updated to import from the ``ffi`` submodule.
diff --git a/changes/2011.feature.1.rst b/changes/2011.feature.1.rst
deleted file mode 100644
index 476813d4d7..0000000000
--- a/changes/2011.feature.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The Table widget now has 100% test coverage and complete API documentation.
diff --git a/changes/2011.feature.2.rst b/changes/2011.feature.2.rst
deleted file mode 100644
index e48283fa2b..0000000000
--- a/changes/2011.feature.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-Tables can now omit the header row by specifying ``headings=None`` and providing accessors.
diff --git a/changes/2011.removal.1.rst b/changes/2011.removal.1.rst
deleted file mode 100644
index 28d434d518..0000000000
--- a/changes/2011.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-``Table.on_double_click`` has been renamed ``Table.on_activate``.
diff --git a/changes/2011.removal.2.rst b/changes/2011.removal.2.rst
deleted file mode 100644
index 950ee3c64c..0000000000
--- a/changes/2011.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-Tables now use an empty string for the default missing value, rather than warning about missing values.
diff --git a/changes/2011.removal.3.rst b/changes/2011.removal.3.rst
deleted file mode 100644
index 0f8d7c80be..0000000000
--- a/changes/2011.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-``Table.add_column()`` has been deprecated in favor of ``Table.append_column()`` and ``Table.insert_column()``
diff --git a/changes/2014.misc.rst b/changes/2014.misc.rst
deleted file mode 100644
index 9eb46067a6..0000000000
--- a/changes/2014.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``pyupgrade`` was updated to its latest version.
diff --git a/changes/2017.feature.1.rst b/changes/2017.feature.1.rst
deleted file mode 100644
index 9e581442ce..0000000000
--- a/changes/2017.feature.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The Tree widget now has 100% test coverage and complete API documentation.
diff --git a/changes/2017.feature.2.rst b/changes/2017.feature.2.rst
deleted file mode 100644
index 65351dd337..0000000000
--- a/changes/2017.feature.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-Columns can now be added and removed from a Tree.
diff --git a/changes/2017.removal.1.rst b/changes/2017.removal.1.rst
deleted file mode 100644
index 882b3b9d01..0000000000
--- a/changes/2017.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``parent`` argument has been removed from the ``insert`` and ``append`` calls on ``TreeSource``. This improves consistency between the API for ``TreeSource`` and the API for ``list``. To insert or append a row in to a descendent of a TreeSource root, use ``insert`` and ``append`` on the parent node itself - i.e., ``source.insert(parent, index, ...)`` becomes ``parent.insert(index, ...)``, and ``source.insert(None, index, ...)`` becomes ``source.insert(index, ...)``.
diff --git a/changes/2017.removal.2.rst b/changes/2017.removal.2.rst
deleted file mode 100644
index 150389a5c1..0000000000
--- a/changes/2017.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-Trees now use an empty string for the default missing value, rather than warning about missing values.
diff --git a/changes/2017.removal.3.rst b/changes/2017.removal.3.rst
deleted file mode 100644
index 28d434d518..0000000000
--- a/changes/2017.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-``Table.on_double_click`` has been renamed ``Table.on_activate``.
diff --git a/changes/2018.feature.rst b/changes/2018.feature.rst
deleted file mode 100644
index de95a2461a..0000000000
--- a/changes/2018.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The default system notification sound can be played via app.beep()
diff --git a/changes/2019.misc.rst b/changes/2019.misc.rst
deleted file mode 100644
index 113d1d37c0..0000000000
--- a/changes/2019.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The Toga repository checkout for Read the Docs builds is now made unshallow to ensure accurate SCM versioning.
diff --git a/changes/2020.bugfix.rst b/changes/2020.bugfix.rst
deleted file mode 100644
index 24040c2fd3..0000000000
--- a/changes/2020.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-The minimum window size is now correctly recomputed and enforced if window content changes.
diff --git a/changes/2021.doc.rst b/changes/2021.doc.rst
deleted file mode 100644
index f4462e2bcb..0000000000
--- a/changes/2021.doc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The Linux system dependencies were updated to reflect current requirements for developing and using Toga.
diff --git a/changes/2022.misc.rst b/changes/2022.misc.rst
deleted file mode 100644
index 9eb46067a6..0000000000
--- a/changes/2022.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``pyupgrade`` was updated to its latest version.
diff --git a/changes/2025.feature.1.rst b/changes/2025.feature.1.rst
deleted file mode 100644
index 1f27d4f773..0000000000
--- a/changes/2025.feature.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-The DetailedList widget now has 100% test coverage and complete API documentation.
diff --git a/changes/2025.feature.2.rst b/changes/2025.feature.2.rst
deleted file mode 100644
index acfbf94e1a..0000000000
--- a/changes/2025.feature.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-The accessors used to populate a DetailedList can now be customised.
diff --git a/changes/2025.feature.3.rst b/changes/2025.feature.3.rst
deleted file mode 100644
index c08ba6a011..0000000000
--- a/changes/2025.feature.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-A DetailedList can now provide a value to use when a row doesn't provide the required data.
diff --git a/changes/2025.feature.4.rst b/changes/2025.feature.4.rst
deleted file mode 100644
index c20370c7b3..0000000000
--- a/changes/2025.feature.4.rst
+++ /dev/null
@@ -1 +0,0 @@
-DetailedList can now respond to "primary" and "secondary" user actions. These may be implemented as left and right swipe respectively, or using any other platform-appropriate mechanism.
diff --git a/changes/2025.removal.1.rst b/changes/2025.removal.1.rst
deleted file mode 100644
index 14d19c204e..0000000000
--- a/changes/2025.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-When constructing a DetailedList from a list of tuples, or a list of lists, the required order of values has changed from (icon, title, subtitle) to (title, subtitle, icon).
diff --git a/changes/2025.removal.2.rst b/changes/2025.removal.2.rst
deleted file mode 100644
index 7b3dc14033..0000000000
--- a/changes/2025.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``on_select`` handler for DetailedList no longer receives the selected row as an argument.
diff --git a/changes/2025.removal.3.rst b/changes/2025.removal.3.rst
deleted file mode 100644
index 14e44ed1af..0000000000
--- a/changes/2025.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-The handling of row deletion in DetailedList widgets has been significantly altered. The ``on_delete`` event handler has been renamed ``on_primary_action``, and is now *only* a notification that a "swipe left" event (or platform equivalent) has been confirmed. This was previously inconsistent across platforms. Some platforms would update the data source to remove the row; some treated ``on_delete`` as a notification event and expected the application to handle the deletion. It is now the application's responsibility to perform the data deletion.
diff --git a/changes/2027.removal.rst b/changes/2027.removal.rst
deleted file mode 100644
index d591714633..0000000000
--- a/changes/2027.removal.rst
+++ /dev/null
@@ -1 +0,0 @@
-Support for Python 3.7 was removed.
diff --git a/changes/2028.misc.rst b/changes/2028.misc.rst
deleted file mode 100644
index 9eb46067a6..0000000000
--- a/changes/2028.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``pyupgrade`` was updated to its latest version.
diff --git a/changes/2029.feature.1.rst b/changes/2029.feature.1.rst
deleted file mode 100644
index 7f58ef70cd..0000000000
--- a/changes/2029.feature.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-Canvas now has 100% test coverage, and complete API documentation.
diff --git a/changes/2029.feature.2.rst b/changes/2029.feature.2.rst
deleted file mode 100644
index cdd27cda72..0000000000
--- a/changes/2029.feature.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-Transformations can now be applied to *any* canvas context, not just the root context.
diff --git a/changes/2029.feature.3.rst b/changes/2029.feature.3.rst
deleted file mode 100644
index c6208565ae..0000000000
--- a/changes/2029.feature.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-Canvas now provides more ``list``-like methods for manipulating drawing objects in a context.
diff --git a/changes/2029.feature.4.rst b/changes/2029.feature.4.rst
deleted file mode 100644
index 4021d671db..0000000000
--- a/changes/2029.feature.4.rst
+++ /dev/null
@@ -1 +0,0 @@
-On Windows, the default font now follows the system theme. On most devices, this means it has changed from Microsoft Sans Serif 8pt to Segoe UI 9pt.
diff --git a/changes/2029.feature.5.rst b/changes/2029.feature.5.rst
deleted file mode 100644
index c8c2e1146e..0000000000
--- a/changes/2029.feature.5.rst
+++ /dev/null
@@ -1 +0,0 @@
-Font sizes are now consistently interpreted as CSS points. On Android, iOS and macOS, this means any numeric font sizes will appear 33% larger than before. The default font size on these platforms is unchanged.
diff --git a/changes/2029.removal.1.rst b/changes/2029.removal.1.rst
deleted file mode 100644
index d1eb9f64ad..0000000000
--- a/changes/2029.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-A Canvas is no longer implicitly a context object. The ``Canvas.context`` property now returns the root context of the canvas. If you were previously using ``Canvas.context()`` to generate an empty context, it should be replaced with ``Canvas.Context()``. Any operations to ``remove()`` drawing objects from the canvas or ``clear()`` the canvas of drawing objects should be made on ``Canvas.context``. Invoking these methods on ``Canvas`` will now call the base ``Widget`` implementations, which will throw an exception because ``Canvas`` widgets cannot have children.
diff --git a/changes/2029.removal.2.rst b/changes/2029.removal.2.rst
deleted file mode 100644
index 3c46c50b0a..0000000000
--- a/changes/2029.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-Drawing operations (e.g., ``arc``, ``line_to``, etc) can no longer be invoked directly on a Canvas. Instead, they should be invoked on the root context of the canvas, retrieved with via the `canvas` property. Context creating operations (``Fill``, ``Stroke`` and ``ClosedPath``) are not affected.
diff --git a/changes/2029.removal.3.rst b/changes/2029.removal.3.rst
deleted file mode 100644
index f4ad827055..0000000000
--- a/changes/2029.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``preserve`` option on ``Fill()`` operations has been deprecated. It was required for an internal optimization and can be safely removed without impact.
diff --git a/changes/2029.removal.4.rst b/changes/2029.removal.4.rst
deleted file mode 100644
index d72db3803d..0000000000
--- a/changes/2029.removal.4.rst
+++ /dev/null
@@ -1 +0,0 @@
-Methods that generate new contexts have been renamed: ``context()``, ``closed_path()``, ``fill()`` and ``stroke()`` have become ``Context()``, ``ClosedPath()``, ``Fill()`` and ``Stroke()`` respectively. This has been done to make it easier to differentiate between primitive drawing operations and context-generating operations.
diff --git a/changes/2029.removal.5.rst b/changes/2029.removal.5.rst
deleted file mode 100644
index ccf97a0fac..0000000000
--- a/changes/2029.removal.5.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``new_path`` operation has been renamed ``begin_path`` for consistency with the HTML5 Canvas API.
diff --git a/changes/2029.removal.6.rst b/changes/2029.removal.6.rst
deleted file mode 100644
index 556a37cf82..0000000000
--- a/changes/2029.removal.6.rst
+++ /dev/null
@@ -1 +0,0 @@
-``fill()`` and ``stroke()`` now return simple drawing operations, rather than context managers. If you attempt to use ``fill()`` or ``stroke()`` on a context as a context manager, an exception will be raised; using these methods on Canvas will raise a warning, but return the appropriate context manager.
diff --git a/changes/2029.removal.7.rst b/changes/2029.removal.7.rst
deleted file mode 100644
index 2508b97086..0000000000
--- a/changes/2029.removal.7.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``clicks`` argument to ``Canvas.on_press`` has been removed. Instead, to detect "double clicks", you should use ``Canvas.on_activate``. The ``clicks`` argument has also been removed from ``Canvas.on_release``, ``Canvas.on_drag``, ``Canvas.on_alt_press``, ``Canvas.on_alt_release``, and ``Canvas.on_alt_drag``.
diff --git a/changes/2029.removal.8.rst b/changes/2029.removal.8.rst
deleted file mode 100644
index c464565d38..0000000000
--- a/changes/2029.removal.8.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``tight`` argument to ``Canvas.measure_text()`` has been deprecated. It was a GTK implementation detail, and can be safely removed without impact.
diff --git a/changes/2034.misc.rst b/changes/2034.misc.rst
deleted file mode 100644
index 0be930004b..0000000000
--- a/changes/2034.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``black`` was updated to its latest version.
diff --git a/changes/2035.misc.rst b/changes/2035.misc.rst
deleted file mode 100644
index 37b0513f6f..0000000000
--- a/changes/2035.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/setup-python from 4.6.1 to 4.7.0.
diff --git a/changes/2039.misc.rst b/changes/2039.misc.rst
deleted file mode 100644
index 87b0c6d54d..0000000000
--- a/changes/2039.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Fixing a bug introduced in #1969 that clashes the dialog display on iOS
diff --git a/changes/2044.feature.rst b/changes/2044.feature.rst
deleted file mode 100644
index d0acf985ec..0000000000
--- a/changes/2044.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Toga now has significantly improved type annotations for its public API
diff --git a/changes/2047.feature.rst b/changes/2047.feature.rst
deleted file mode 100644
index c5bd725787..0000000000
--- a/changes/2047.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Applications now verify that a main window has been created as part of the ``startup()`` method.
diff --git a/changes/2050.feature.rst b/changes/2050.feature.rst
deleted file mode 100644
index e1632062c5..0000000000
--- a/changes/2050.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-An implementation of ActivityIndicator was added to the Web backend.
diff --git a/changes/2051.feature.rst b/changes/2051.feature.rst
deleted file mode 100644
index 49248b82c0..0000000000
--- a/changes/2051.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-An implementation of Divider was added to the Web backend.
diff --git a/changes/2052.misc.rst b/changes/2052.misc.rst
deleted file mode 100644
index a4ee91fe66..0000000000
--- a/changes/2052.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The version pin for the prerelease pygobject has been updated, following the resolution of pygobject#119.
diff --git a/changes/2053.misc.rst b/changes/2053.misc.rst
deleted file mode 100644
index 44850f3029..0000000000
--- a/changes/2053.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-An edge case in SplitContainer having empty content was corrected on Cocoa.
diff --git a/changes/2055.misc.rst b/changes/2055.misc.rst
deleted file mode 100644
index c1a62a07d2..0000000000
--- a/changes/2055.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Full test coverage for handlers was added.
diff --git a/changes/2056.misc.rst b/changes/2056.misc.rst
deleted file mode 100644
index e1b6193e1c..0000000000
--- a/changes/2056.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``flake8`` was updated to its latest version.
diff --git a/changes/2057.misc.rst b/changes/2057.misc.rst
deleted file mode 100644
index 2b29b4a1c2..0000000000
--- a/changes/2057.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Codespell was added to the pre-commit configuration.
diff --git a/changes/2058.feature.rst b/changes/2058.feature.rst
deleted file mode 100644
index e50fbe1a5f..0000000000
--- a/changes/2058.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Window and MainWindow now have 100% test coverage, and complete API documentation.
diff --git a/changes/2058.removal.1.rst b/changes/2058.removal.1.rst
deleted file mode 100644
index 402071ece3..0000000000
--- a/changes/2058.removal.1.rst
+++ /dev/null
@@ -1 +0,0 @@
-Windows no longer need to be explicitly added to the app's window list. When a window is created, it will be automatically added to the windows for the currently running app.
diff --git a/changes/2058.removal.2.rst b/changes/2058.removal.2.rst
deleted file mode 100644
index 3499758242..0000000000
--- a/changes/2058.removal.2.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``multiselect`` argument to Open File and Select Folder dialogs has been renamed ``multiple_select``, for consistency with other widgets that have multiple selection capability.
diff --git a/changes/2058.removal.3.rst b/changes/2058.removal.3.rst
deleted file mode 100644
index 4c6d52f106..0000000000
--- a/changes/2058.removal.3.rst
+++ /dev/null
@@ -1 +0,0 @@
-``Window.resizeable`` and ``Window.closeable`` have been renamed ``Window.resizable`` and ``Window.closable``, to adhere to US spelling conventions.
diff --git a/changes/2059.misc.rst b/changes/2059.misc.rst
deleted file mode 100644
index c3ec018f49..0000000000
--- a/changes/2059.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Changed spelling to prevent pre-commit(Codespell) error.
diff --git a/changes/2067.misc.rst b/changes/2067.misc.rst
deleted file mode 100644
index 9eb46067a6..0000000000
--- a/changes/2067.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``pyupgrade`` was updated to its latest version.
diff --git a/changes/2068.misc.rst b/changes/2068.misc.rst
deleted file mode 100644
index 16e1a04a63..0000000000
--- a/changes/2068.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-App.beep() has been implemented for Android.
diff --git a/changes/2069.misc.rst b/changes/2069.misc.rst
deleted file mode 100644
index bb5a3c7699..0000000000
--- a/changes/2069.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-A backwards incompatibility issue in the date_and_time example was corrected.
diff --git a/changes/2085.misc.rst b/changes/2085.misc.rst
deleted file mode 100644
index fc40890351..0000000000
--- a/changes/2085.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-WebView no longer uses the deprecated ``run_javascript`` API on Gtk.
diff --git a/changes/2089.feature.rst b/changes/2089.feature.rst
deleted file mode 100644
index d8ec047366..0000000000
--- a/changes/2089.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-A PasswordInput widget was added to the Web backend.
diff --git a/changes/2090.misc.rst b/changes/2090.misc.rst
deleted file mode 100644
index 20cd09480d..0000000000
--- a/changes/2090.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The use of indirect imports on Winforms has been replaced with direct imports.
diff --git a/changes/2092.misc.rst b/changes/2092.misc.rst
deleted file mode 100644
index 16b6a7f30a..0000000000
--- a/changes/2092.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Dialogs were added to the textual backend.
diff --git a/changes/2093.misc.rst b/changes/2093.misc.rst
deleted file mode 100644
index a8aa22d02b..0000000000
--- a/changes/2093.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Repeated autodoc options were refactored into the Sphinx configuration.
diff --git a/changes/2094.bugfix.rst b/changes/2094.bugfix.rst
deleted file mode 100644
index ee4d11b975..0000000000
--- a/changes/2094.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Fixes `TypeError` when `toga.Window.title` is invoked on WinForms.
diff --git a/changes/2095.bugfix.rst b/changes/2095.bugfix.rst
deleted file mode 100644
index 9d741d8ac8..0000000000
--- a/changes/2095.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Modified WinForms backend to prevent error when window content is not set.
diff --git a/changes/2101.misc.rst b/changes/2101.misc.rst
deleted file mode 100644
index 13e36e26e1..0000000000
--- a/changes/2101.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated ncipollo/release-action from 1.12.0 to 1.13.0.
diff --git a/changes/2102.misc.rst b/changes/2102.misc.rst
deleted file mode 100644
index 53d6e44bab..0000000000
--- a/changes/2102.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/checkout from 3.5.3 to 3.6.0.
diff --git a/changes/2109.feature.rst b/changes/2109.feature.rst
deleted file mode 100644
index 5d1a07e596..0000000000
--- a/changes/2109.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-The WebKit inspector is automatically enabled on all webviews, provided you're using macOS 13.3 (Ventura) or iOS 16.4, or later.
diff --git a/changes/2113.misc.rst b/changes/2113.misc.rst
deleted file mode 100644
index 5ba9f597d6..0000000000
--- a/changes/2113.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/checkout from 3.6.0 to 4.0.0.
diff --git a/changes/2114.misc.rst b/changes/2114.misc.rst
deleted file mode 100644
index 75ff7bec3d..0000000000
--- a/changes/2114.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/upload-artifact from 3.1.2 to 3.1.3.
diff --git a/changes/2115.misc.rst b/changes/2115.misc.rst
deleted file mode 100644
index 0be930004b..0000000000
--- a/changes/2115.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``black`` was updated to its latest version.
diff --git a/changes/2116.misc.rst b/changes/2116.misc.rst
deleted file mode 100644
index 05179231dd..0000000000
--- a/changes/2116.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-An error raised when displaying a GTK About dialog was resolved.
diff --git a/changes/2118.misc.rst b/changes/2118.misc.rst
deleted file mode 100644
index e10be4a164..0000000000
--- a/changes/2118.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-A stray symlink in the tutorials folder was purged.
diff --git a/changes/2119.misc.rst b/changes/2119.misc.rst
deleted file mode 100644
index 941f7e555a..0000000000
--- a/changes/2119.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-An issue with imageview scaling on GTK was resolved.
diff --git a/changes/2123.misc.rst b/changes/2123.misc.rst
deleted file mode 100644
index 9eb46067a6..0000000000
--- a/changes/2123.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``pyupgrade`` was updated to its latest version.
diff --git a/changes/2124.misc.rst b/changes/2124.misc.rst
deleted file mode 100644
index 0be930004b..0000000000
--- a/changes/2124.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``black`` was updated to its latest version.
diff --git a/changes/2127.misc.rst b/changes/2127.misc.rst
deleted file mode 100644
index 96fd43c442..0000000000
--- a/changes/2127.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-A misspelled delegate assignment was removed from the iOS and Cocoa Webkit implementations.
diff --git a/changes/2128.misc.rst b/changes/2128.misc.rst
deleted file mode 100644
index 2ddf867e95..0000000000
--- a/changes/2128.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The copyright year was removed from the documentation footer.
diff --git a/changes/2131.misc.rst b/changes/2131.misc.rst
deleted file mode 100644
index 9eb46067a6..0000000000
--- a/changes/2131.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``pyupgrade`` was updated to its latest version.
diff --git a/changes/2132.misc.rst b/changes/2132.misc.rst
deleted file mode 100644
index 74ff099c31..0000000000
--- a/changes/2132.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/checkout from 4.0.0 to 4.1.0.
diff --git a/changes/2136.bugfix.rst b/changes/2136.bugfix.rst
deleted file mode 100644
index 4357ea961d..0000000000
--- a/changes/2136.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-Multiline text inputs no longer show spelling suggestions when in readonly mode.
diff --git a/changes/2146.misc.rst b/changes/2146.misc.rst
deleted file mode 100644
index 6375be371e..0000000000
--- a/changes/2146.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``pre-commit-hooks`` was updated to its latest version.
diff --git a/changes/2147.misc.rst b/changes/2147.misc.rst
deleted file mode 100644
index 9eb46067a6..0000000000
--- a/changes/2147.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``pyupgrade`` was updated to its latest version.
diff --git a/changes/2148.misc.rst b/changes/2148.misc.rst
deleted file mode 100644
index f2f6d8b238..0000000000
--- a/changes/2148.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``codespell`` was updated to its latest version.
diff --git a/changes/2149.misc.rst b/changes/2149.misc.rst
deleted file mode 100644
index 8b779af0e5..0000000000
--- a/changes/2149.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/setup-python from 4.7.0 to 4.7.1.
diff --git a/changes/2150.misc.rst b/changes/2150.misc.rst
deleted file mode 100644
index 75ff7bec3d..0000000000
--- a/changes/2150.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/upload-artifact from 3.1.2 to 3.1.3.
diff --git a/changes/2151.feature.rst b/changes/2151.feature.rst
deleted file mode 100644
index 9ec4d2524c..0000000000
--- a/changes/2151.feature.rst
+++ /dev/null
@@ -1 +0,0 @@
-Text input widgets on macOS now support undo and redo.
diff --git a/changes/2161.bugfix.rst b/changes/2161.bugfix.rst
deleted file mode 100644
index 443b8aac2d..0000000000
--- a/changes/2161.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-iOS container views are now set to automatically resize with their parent view
diff --git a/changes/2163.misc.rst b/changes/2163.misc.rst
deleted file mode 100644
index 971a390ec9..0000000000
--- a/changes/2163.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Winforms command event handlers were made persistent objects, rather than on-demand closures.
diff --git a/changes/2165.misc.rst b/changes/2165.misc.rst
deleted file mode 100644
index 0be930004b..0000000000
--- a/changes/2165.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-The ``pre-commit`` hook for ``black`` was updated to its latest version.
diff --git a/changes/2166.misc.rst b/changes/2166.misc.rst
deleted file mode 100644
index 160e818feb..0000000000
--- a/changes/2166.misc.rst
+++ /dev/null
@@ -1 +0,0 @@
-Updated actions/checkout from 4.1.0 to 4.1.1.
diff --git a/changes/2194.bugfix.rst b/changes/2194.bugfix.rst
new file mode 100644
index 0000000000..5e064641e3
--- /dev/null
+++ b/changes/2194.bugfix.rst
@@ -0,0 +1 @@
+The web backend no longer generates a duplicate titlebar.
diff --git a/changes/2195.bugfix.rst b/changes/2195.bugfix.rst
new file mode 100644
index 0000000000..4fb4695357
--- /dev/null
+++ b/changes/2195.bugfix.rst
@@ -0,0 +1 @@
+An issue with the display of the About dialog on the web backend was corrected.
diff --git a/changes/2198.feature.rst b/changes/2198.feature.rst
new file mode 100644
index 0000000000..4b2d73689a
--- /dev/null
+++ b/changes/2198.feature.rst
@@ -0,0 +1 @@
+A wider range of command shortcut keys are now supported on WinForms.
diff --git a/changes/2198.removal.rst b/changes/2198.removal.rst
new file mode 100644
index 0000000000..02e332e010
--- /dev/null
+++ b/changes/2198.removal.rst
@@ -0,0 +1 @@
+The use of Caps Lock as a keyboard modifier for commands was removed.
diff --git a/changes/2199.doc.rst b/changes/2199.doc.rst
new file mode 100644
index 0000000000..4ee080ce2d
--- /dev/null
+++ b/changes/2199.doc.rst
@@ -0,0 +1 @@
+Documentation for ``toga.Key`` was added.
diff --git a/changes/2200.feature.rst b/changes/2200.feature.rst
new file mode 100644
index 0000000000..701f35111b
--- /dev/null
+++ b/changes/2200.feature.rst
@@ -0,0 +1 @@
+Most widgets with flexible sizes now default to a minimum size of 100 CSS pixels. An explicit size will still override this value.
diff --git a/changes/2201.misc.rst b/changes/2201.misc.rst
new file mode 100644
index 0000000000..4d73995780
--- /dev/null
+++ b/changes/2201.misc.rst
@@ -0,0 +1 @@
+Minor fix: removed a repeated word in the docs for App Paths
diff --git a/changes/2204.misc.rst b/changes/2204.misc.rst
new file mode 100644
index 0000000000..1524aa29c5
--- /dev/null
+++ b/changes/2204.misc.rst
@@ -0,0 +1 @@
+Some inconsistencies in widget support documentation were corrected.
diff --git a/changes/2214.bugfix.rst b/changes/2214.bugfix.rst
new file mode 100644
index 0000000000..97e2873a7e
--- /dev/null
+++ b/changes/2214.bugfix.rst
@@ -0,0 +1 @@
+Compliance with Apple's HIG regarding the naming and shortcuts for the Close and Close All menu items was improved.
diff --git a/changes/2215.misc.rst b/changes/2215.misc.rst
new file mode 100644
index 0000000000..918e180a5b
--- /dev/null
+++ b/changes/2215.misc.rst
@@ -0,0 +1 @@
+On Android the creation of the app commands has been moved to the method _create_app_commands()
diff --git a/changes/2216.misc.rst b/changes/2216.misc.rst
new file mode 100644
index 0000000000..dd3c07c506
--- /dev/null
+++ b/changes/2216.misc.rst
@@ -0,0 +1 @@
+Add more tests for sliders with empty ranges
diff --git a/changes/750.bugfix.rst b/changes/750.bugfix.rst
deleted file mode 100644
index 15b2c1ae59..0000000000
--- a/changes/750.bugfix.rst
+++ /dev/null
@@ -1 +0,0 @@
-The WinForms event loop was decoupled from the main form, allowing background tasks to run without a main window being present.
diff --git a/cocoa/setup.cfg b/cocoa/setup.cfg
index 80743dbd64..7b9f2cc29f 100644
--- a/cocoa/setup.cfg
+++ b/cocoa/setup.cfg
@@ -12,7 +12,7 @@ author_email = russell@keith-magee.com
 maintainer = BeeWare Team
 maintainer_email = team@beeware.org
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Intended Audience :: Developers
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
diff --git a/cocoa/setup.py b/cocoa/setup.py
index f9c2736edd..30217c2e40 100644
--- a/cocoa/setup.py
+++ b/cocoa/setup.py
@@ -7,7 +7,7 @@
     version=version,
     install_requires=[
         "fonttools >= 4.42.1, < 5.0.0",
-        "rubicon-objc >= 0.4.5rc1, < 0.5.0",
+        "rubicon-objc >= 0.4.7, < 0.5.0",
         f"toga-core == {version}",
     ],
 )
diff --git a/cocoa/src/toga_cocoa/app.py b/cocoa/src/toga_cocoa/app.py
index 54bbd2a2e3..d22135fdf0 100644
--- a/cocoa/src/toga_cocoa/app.py
+++ b/cocoa/src/toga_cocoa/app.py
@@ -2,11 +2,13 @@
 import inspect
 import os
 import sys
+from pathlib import Path
 from urllib.parse import unquote, urlparse
 
 from rubicon.objc.eventloop import CocoaLifecycle, EventLoopPolicy
 
 import toga
+from toga.command import GROUP_BREAK, SECTION_BREAK
 from toga.handlers import NativeHandler
 
 from .keys import cocoa_key
@@ -16,6 +18,7 @@
     NSAboutPanelOptionApplicationIcon,
     NSAboutPanelOptionApplicationName,
     NSAboutPanelOptionApplicationVersion,
+    NSAboutPanelOptionVersion,
     NSApplication,
     NSApplicationActivationPolicyRegular,
     NSBeep,
@@ -40,11 +43,11 @@
 class MainWindow(Window):
     def cocoa_windowShouldClose(self):
         # Main Window close is a proxy for "Exit app".
-        # Defer all handling to the app's exit method.
+        # Defer all handling to the app's on_exit handler.
         # As a result of calling that method, the app will either
         # exit, or the user will cancel the exit; in which case
         # the main window shouldn't close, either.
-        self.interface.app.exit()
+        self.interface.app.on_exit()
         return False
 
 
@@ -57,21 +60,21 @@ def applicationDidFinishLaunching_(self, notification):
         self.native.activateIgnoringOtherApps(True)
 
     @objc_method
-    def applicationOpenUntitledFile_(self, sender) -> bool:
+    def applicationOpenUntitledFile_(self, sender) -> bool:  # pragma: no cover
         self.impl.select_file()
         return True
 
     @objc_method
-    def addDocument_(self, document) -> None:
+    def addDocument_(self, document) -> None:  # pragma: no cover
         # print("Add Document", document)
         super().addDocument_(document)
 
     @objc_method
-    def applicationShouldOpenUntitledFile_(self, sender) -> bool:
+    def applicationShouldOpenUntitledFile_(self, sender) -> bool:  # pragma: no cover
         return True
 
     @objc_method
-    def application_openFiles_(self, app, filenames) -> None:
+    def application_openFiles_(self, app, filenames) -> None:  # pragma: no cover
         for i in range(0, len(filenames)):
             filename = filenames[i]
             # If you start your Toga application as `python myapp.py` or
@@ -98,8 +101,7 @@ def application_openFiles_(self, app, filenames) -> None:
     @objc_method
     def selectMenuItem_(self, sender) -> None:
         cmd = self.impl._menu_items[sender]
-        if cmd.action:
-            cmd.action(None)
+        cmd.action()
 
     @objc_method
     def validateMenuItem_(self, sender) -> bool:
@@ -119,6 +121,9 @@ def __init__(self, interface):
         asyncio.set_event_loop_policy(EventLoopPolicy())
         self.loop = asyncio.new_event_loop()
 
+        # Stimulate the build of the app
+        self.create()
+
     def create(self):
         self.native = NSApplication.sharedApplication
         self.native.setActivationPolicy(NSApplicationActivationPolicyRegular)
@@ -142,6 +147,8 @@ def create(self):
 
         # Create the lookup table of menu items,
         # then force the creation of the menus.
+        self._menu_groups = {}
+        self._menu_items = {}
         self.create_menus()
 
     def _create_app_commands(self):
@@ -155,7 +162,7 @@ def _create_app_commands(self):
             ),
             toga.Command(
                 None,
-                "Preferences",
+                "Settings\u2026",
                 shortcut=toga.Key.MOD_1 + ",",
                 group=toga.Group.APP,
                 section=20,
@@ -185,31 +192,30 @@ def _create_app_commands(self):
             ),
             # Quit should always be the last item, in a section on its own
             toga.Command(
-                self._menu_exit,
+                self._menu_quit,
                 "Quit " + formal_name,
                 shortcut=toga.Key.MOD_1 + "q",
                 group=toga.Group.APP,
                 section=sys.maxsize,
             ),
             # ---- File menu ----------------------------------
-            # This is a bit of an oddity. Safari has 2 distinct "Close Window" and
-            # "Close All Windows" menu items (partially to differentiate from "Close
-            # Tab"). Most other Apple HIG apps have a "Close" item that becomes
-            # "Close All" when you press Option (MOD_2). That behavior isn't something
-            # we're currently set up to implement, so we live with a separate menu item
-            # for now.
+            # This is a bit of an oddity. Apple HIG apps that don't have tabs as
+            # part of their interface (so, Preview and Numbers, but not Safari)
+            # have a "Close" item that becomes "Close All" when you press Option
+            # (MOD_2). That behavior isn't something we're currently set up to
+            # implement, so we live with a separate menu item for now.
             toga.Command(
                 self._menu_close_window,
-                "Close Window",
-                shortcut=toga.Key.MOD_1 + "W",
+                "Close",
+                shortcut=toga.Key.MOD_1 + "w",
                 group=toga.Group.FILE,
                 order=1,
                 section=50,
             ),
             toga.Command(
                 self._menu_close_all_windows,
-                "Close All Windows",
-                shortcut=toga.Key.MOD_2 + toga.Key.MOD_1 + "W",
+                "Close All",
+                shortcut=toga.Key.MOD_2 + toga.Key.MOD_1 + "w",
                 group=toga.Group.FILE,
                 order=2,
                 section=50,
@@ -285,7 +291,7 @@ def _create_app_commands(self):
             ),
             # ---- Help menu ----------------------------------
             toga.Command(
-                lambda _, **kwargs: self.interface.visit_homepage(),
+                self._menu_visit_homepage,
                 "Visit homepage",
                 enabled=self.interface.home_page is not None,
                 group=toga.Group.HELP,
@@ -295,32 +301,42 @@ def _create_app_commands(self):
     def _menu_about(self, app, **kwargs):
         self.interface.about()
 
-    def _menu_exit(self, app, **kwargs):
-        self.interface.exit()
+    def _menu_quit(self, app, **kwargs):
+        self.interface.on_exit()
 
     def _menu_close_window(self, app, **kwargs):
         if self.interface.current_window:
             self.interface.current_window._impl.native.performClose(None)
 
     def _menu_close_all_windows(self, app, **kwargs):
-        for window in self.interface.windows:
+        # Convert to a list to so that we're not altering a set while iterating
+        for window in list(self.interface.windows):
             window._impl.native.performClose(None)
 
     def _menu_minimize(self, app, **kwargs):
         if self.interface.current_window:
             self.interface.current_window._impl.native.miniaturize(None)
 
+    def _menu_visit_homepage(self, app, **kwargs):
+        self.interface.visit_homepage()
+
     def create_menus(self):
-        # Recreate the menu
-        self._menu_items = {}
-        self._menu_groups = {}
+        # Recreate the menu.
+        # Remove any native references to the existing menu
+        for menu_item, cmd in self._menu_items.items():
+            cmd._impl.native.remove(menu_item)
+
+        # Create a clean menubar instance.
         menubar = NSMenu.alloc().initWithTitle("MainMenu")
         submenu = None
+        self._menu_groups = {}
+        self._menu_items = {}
+
         for cmd in self.interface.commands:
-            if cmd == toga.GROUP_BREAK:
+            if cmd == GROUP_BREAK:
                 submenu = None
-            elif cmd == toga.SECTION_BREAK:
-                submenu.addItem_(NSMenuItem.separatorItem())
+            elif cmd == SECTION_BREAK:
+                submenu.addItem(NSMenuItem.separatorItem())
             else:
                 submenu = self._submenu(cmd.group, menubar)
 
@@ -343,9 +359,17 @@ def create_menus(self):
                     action=action,
                     keyEquivalent=key,
                 )
+
                 if modifier is not None:
                     item.keyEquivalentModifierMask = modifier
 
+                # Explicit set the initial enabled/disabled state on the menu item
+                item.setEnabled(cmd.enabled)
+
+                # Associated the MenuItem with the command, so that future
+                # changes to enabled etc are reflected.
+                cmd._impl.native.add(item)
+
                 self._menu_items[item] = cmd
                 submenu.addItem(item)
 
@@ -379,9 +403,6 @@ def _submenu(self, group, menubar):
             return submenu
 
     def main_loop(self):
-        # Stimulate the build of the app
-        self.create()
-
         self.loop.run_forever(lifecycle=CocoaLifecycle(self.native))
 
     def set_main_window(self, window):
@@ -391,28 +412,28 @@ def show_about_dialog(self):
         options = NSMutableDictionary.alloc().init()
 
         options[NSAboutPanelOptionApplicationIcon] = self.interface.icon._impl.native
+        options[NSAboutPanelOptionApplicationName] = self.interface.formal_name
 
-        if self.interface.name is not None:
-            options[NSAboutPanelOptionApplicationName] = self.interface.name
-
-        if self.interface.version is not None:
+        if self.interface.version is None:
+            options[NSAboutPanelOptionApplicationVersion] = "0.0"
+        else:
             options[NSAboutPanelOptionApplicationVersion] = self.interface.version
 
         # The build number
-        # if self.interface.version is not None:
-        #     options[NSAboutPanelOptionVersion] = "the build"
+        options[NSAboutPanelOptionVersion] = "1"
 
-        if self.interface.author is not None:
-            options["Copyright"] = "Copyright © {author}".format(
-                author=self.interface.author
-            )
+        if self.interface.author is None:
+            options["Copyright"] = ""
+        else:
+            options["Copyright"] = f"Copyright © {self.interface.author}"
 
         self.native.orderFrontStandardAboutPanelWithOptions(options)
 
     def beep(self):
         NSBeep()
 
-    def exit(self):
+    # We can't call this under test conditions, because it would kill the test harness
+    def exit(self):  # pragma: no cover
         self.loop.stop()
 
     def get_current_window(self):
@@ -422,11 +443,6 @@ def set_current_window(self, window):
         window._impl.native.makeKeyAndOrderFront(window._impl.native)
 
     def enter_full_screen(self, windows):
-        # If we're already in full screen mode, exit so that
-        # we can re-assign windows to screens.
-        if self.interface.is_full_screen:
-            self.interface.exit_full_screen()
-
         opts = NSMutableDictionary.alloc().init()
         opts.setObject(
             NSNumber.numberWithBool(True), forKey="NSFullScreenModeAllScreens"
@@ -470,19 +486,22 @@ def select_file(self, **kwargs):
         """No-op when the app is not a ``DocumentApp``."""
 
 
-class DocumentApp(App):
+class DocumentApp(App):  # pragma: no cover
     def _create_app_commands(self):
         super()._create_app_commands()
         self.interface.commands.add(
             toga.Command(
-                lambda _: self.select_file(),
-                text="Open...",
+                self._menu_open_file,
+                text="Open\u2026",
                 shortcut=toga.Key.MOD_1 + "o",
                 group=toga.Group.FILE,
                 section=0,
             ),
         )
 
+    def _menu_open_file(self, app, **kwargs):
+        self.select_file()
+
     def select_file(self, **kwargs):
         # FIXME This should be all we need; but for some reason, application types
         # aren't being registered correctly..
@@ -504,20 +523,9 @@ def select_file(self, **kwargs):
         self.appDelegate.application_openFiles_(None, panel.URLs)
 
     def open_document(self, fileURL):
-        """Open a new document in this app.
-
-        Args:
-            fileURL (str): The URL/path to the file to add as a document.
-        """
         # Convert a cocoa fileURL to a file path.
         fileURL = fileURL.rstrip("/")
-        path = unquote(urlparse(fileURL).path)
-        extension = os.path.splitext(path)[1][1:]
-
-        # Create the document instance
-        DocType = self.interface.document_types[extension]
-        document = DocType(path, app=self.interface)
-        self.interface._documents.append(document)
+        path = Path(unquote(urlparse(fileURL).path))
 
-        # Show the document.
-        document.show()
+        # Create and show the document instance
+        self.interface._open(path)
diff --git a/cocoa/src/toga_cocoa/command.py b/cocoa/src/toga_cocoa/command.py
index 8575d29e27..876a7226d5 100644
--- a/cocoa/src/toga_cocoa/command.py
+++ b/cocoa/src/toga_cocoa/command.py
@@ -1,7 +1,17 @@
+from toga_cocoa.libs import NSMenuItem
+
+
 class Command:
     def __init__(self, interface):
         self.interface = interface
-        self.native = []
+        self.native = set()
 
     def set_enabled(self, value):
-        pass
+        for item in self.native:
+            if isinstance(item, NSMenuItem):
+                # Menu item enabled status is determined by the app delegate
+                item.menu.update()
+            else:
+                # Otherwise, assume the native object has
+                # and explicit enabled property
+                item.setEnabled(value)
diff --git a/cocoa/src/toga_cocoa/constraints.py b/cocoa/src/toga_cocoa/constraints.py
index 352ac0c838..b0de131005 100644
--- a/cocoa/src/toga_cocoa/constraints.py
+++ b/cocoa/src/toga_cocoa/constraints.py
@@ -34,10 +34,15 @@ def __del__(self):  # pragma: nocover
     def _remove_constraints(self):
         if self.container:
             # print(f"Remove constraints for {self.widget} in {self.container}")
-            self.container.native.removeConstraint(self.width_constraint)
-            self.container.native.removeConstraint(self.height_constraint)
-            self.container.native.removeConstraint(self.left_constraint)
-            self.container.native.removeConstraint(self.top_constraint)
+            # Due to the unpredictability of garbage collection, it's possible for
+            # the native object of the window's container to be deleted on the ObjC
+            # side before the constraints for the window have been removed. Protect
+            # against this possibility.
+            if self.container.native:
+                self.container.native.removeConstraint(self.width_constraint)
+                self.container.native.removeConstraint(self.height_constraint)
+                self.container.native.removeConstraint(self.left_constraint)
+                self.container.native.removeConstraint(self.top_constraint)
 
             self.width_constraint.release()
             self.height_constraint.release()
diff --git a/cocoa/src/toga_cocoa/container.py b/cocoa/src/toga_cocoa/container.py
index 8cef990686..f612b291ac 100644
--- a/cocoa/src/toga_cocoa/container.py
+++ b/cocoa/src/toga_cocoa/container.py
@@ -67,7 +67,7 @@ def __init__(
             NSLayoutAttributeLeft,
             1.0,
             min_width,
-        )
+        ).retain()
         self.native.addConstraint(self._min_width_constraint)
 
         self._min_height_constraint = NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant_(  # noqa: E501
@@ -78,9 +78,14 @@ def __init__(
             NSLayoutAttributeTop,
             1.0,
             min_height,
-        )
+        ).retain()
         self.native.addConstraint(self._min_height_constraint)
 
+    def __del__(self):
+        self._min_height_constraint.release()
+        self._min_width_constraint.release()
+        self.native = None
+
     @property
     def content(self):
         """The Toga implementation widget that is the root content of this container.
diff --git a/cocoa/src/toga_cocoa/dialogs.py b/cocoa/src/toga_cocoa/dialogs.py
index d2e5fd70ed..31a4a8997e 100644
--- a/cocoa/src/toga_cocoa/dialogs.py
+++ b/cocoa/src/toga_cocoa/dialogs.py
@@ -54,14 +54,14 @@ def build_dialog(self):
         pass
 
     def completion_handler(self, return_value: int) -> None:
-        self.on_result(None, None)
+        self.on_result(None)
 
         self.interface.future.set_result(None)
 
     def bool_completion_handler(self, return_value: int) -> None:
         result = return_value == NSAlertFirstButtonReturn
 
-        self.on_result(None, result)
+        self.on_result(result)
 
         self.interface.future.set_result(result)
 
@@ -216,7 +216,7 @@ def single_path_completion_handler(self, return_value: int) -> None:
         else:
             result = None
 
-        self.on_result(None, result)
+        self.on_result(result)
         self.interface.future.set_result(result)
 
     def multi_path_completion_handler(self, return_value: int) -> None:
@@ -225,7 +225,7 @@ def multi_path_completion_handler(self, return_value: int) -> None:
         else:
             result = None
 
-        self.on_result(None, result)
+        self.on_result(result)
 
         self.interface.future.set_result(result)
 
diff --git a/cocoa/src/toga_cocoa/documents.py b/cocoa/src/toga_cocoa/documents.py
index 81166fb51c..efa7b91092 100644
--- a/cocoa/src/toga_cocoa/documents.py
+++ b/cocoa/src/toga_cocoa/documents.py
@@ -1,9 +1,10 @@
+import os
 from urllib.parse import quote
 
 from toga_cocoa.libs import NSURL, NSDocument, objc_method, objc_property
 
 
-class TogaDocument(NSDocument):
+class TogaDocument(NSDocument):  # pragma: no cover
     interface = objc_property(object, weak=True)
     impl = objc_property(object, weak=True)
 
@@ -19,14 +20,17 @@ def readFromFileWrapper_ofType_error_(
         return True
 
 
-class Document:
+class Document:  # pragma: no cover
+    # macOS has multiple documents in a single app instance.
+    SINGLE_DOCUMENT_APP = False
+
     def __init__(self, interface):
         self.native = TogaDocument.alloc()
         self.native.interface = interface
         self.native.impl = self
 
         self.native.initWithContentsOfURL(
-            NSURL.URLWithString(f"file://{quote(interface.filename)}"),
+            NSURL.URLWithString(f"file://{quote(os.fsdecode(interface.path))}"),
             ofType=interface.document_type,
             error=None,
         )
diff --git a/cocoa/src/toga_cocoa/images.py b/cocoa/src/toga_cocoa/images.py
index 466b9a0876..012ab55779 100644
--- a/cocoa/src/toga_cocoa/images.py
+++ b/cocoa/src/toga_cocoa/images.py
@@ -1,3 +1,4 @@
+from ctypes import POINTER, c_char, cast
 from pathlib import Path
 
 from toga_cocoa.libs import (
@@ -8,6 +9,15 @@
 )
 
 
+def nsdata_to_bytes(data: NSData) -> bytes:
+    """Convert an NSData into a raw bytes representation"""
+    # data is an NSData object that has .bytes as a c_void_p, and a .length. Cast to
+    # POINTER(c_char) to get an addressable array of bytes, and slice that array to
+    # the known length. We don't use c_char_p because it has handling of NUL
+    # termination, and POINTER(c_char) allows array subscripting.
+    return cast(data.bytes, POINTER(c_char))[: data.length]
+
+
 class Image:
     def __init__(self, interface, path=None, data=None):
         self.interface = interface
@@ -40,6 +50,15 @@ def get_width(self):
     def get_height(self):
         return self.native.size.height
 
+    def get_data(self):
+        return nsdata_to_bytes(
+            NSBitmapImageRep.representationOfImageRepsInArray(
+                self.native.representations,
+                usingType=NSBitmapImageFileType.PNG,
+                properties=None,
+            )
+        )
+
     def save(self, path):
         path = Path(path)
         try:
diff --git a/cocoa/src/toga_cocoa/keys.py b/cocoa/src/toga_cocoa/keys.py
index b027dae328..9648bba62b 100644
--- a/cocoa/src/toga_cocoa/keys.py
+++ b/cocoa/src/toga_cocoa/keys.py
@@ -2,122 +2,147 @@
 
 from toga import Key
 from toga_cocoa.libs import (
-    NSEventModifierFlagCapsLock,
     NSEventModifierFlagCommand,
     NSEventModifierFlagControl,
     NSEventModifierFlagOption,
     NSEventModifierFlagShift,
 )
 
+# A map of Cocoa keycodes to Toga key values, when no Shift is pressed
+TOGA_KEYS = {
+    0: Key.A,
+    1: Key.S,
+    2: Key.D,
+    3: Key.F,
+    4: Key.H,
+    5: Key.G,
+    6: Key.Z,
+    7: Key.X,
+    8: Key.C,
+    9: Key.V,
+    11: Key.B,
+    12: Key.Q,
+    13: Key.W,
+    14: Key.E,
+    15: Key.R,
+    16: Key.Y,
+    17: Key.T,
+    18: Key._1,
+    19: Key._2,
+    20: Key._3,
+    21: Key._4,
+    22: Key._6,
+    23: Key._5,
+    24: Key.PLUS,
+    25: Key._9,
+    26: Key._7,
+    27: Key.MINUS,
+    28: Key._8,
+    29: Key._0,
+    30: Key.CLOSE_BRACKET,
+    31: Key.O,
+    32: Key.U,
+    33: Key.OPEN_BRACKET,
+    34: Key.I,
+    35: Key.P,
+    36: Key.ENTER,
+    37: Key.L,
+    38: Key.J,
+    39: Key.QUOTE,
+    40: Key.K,
+    41: Key.COLON,
+    42: Key.BACKSLASH,
+    43: Key.COMMA,
+    44: Key.SLASH,
+    45: Key.N,
+    46: Key.M,
+    47: Key.FULL_STOP,
+    48: Key.TAB,
+    49: Key.SPACE,
+    50: Key.BACK_QUOTE,
+    51: Key.BACKSPACE,
+    53: Key.ESCAPE,
+    65: Key.NUMPAD_DECIMAL_POINT,
+    67: Key.NUMPAD_MULTIPLY,
+    69: Key.NUMPAD_PLUS,
+    71: Key.NUMPAD_CLEAR,
+    75: Key.NUMPAD_DIVIDE,
+    76: Key.NUMPAD_ENTER,
+    78: Key.NUMPAD_MINUS,
+    81: Key.NUMPAD_EQUAL,
+    82: Key.NUMPAD_0,
+    83: Key.NUMPAD_1,
+    84: Key.NUMPAD_2,
+    85: Key.NUMPAD_3,
+    86: Key.NUMPAD_4,
+    87: Key.NUMPAD_5,
+    88: Key.NUMPAD_6,
+    89: Key.NUMPAD_7,
+    91: Key.NUMPAD_8,
+    92: Key.NUMPAD_9,
+    # : Key.F4,
+    96: Key.F5,
+    97: Key.F7,
+    98: Key.F5,
+    99: Key.F3,
+    100: Key.F8,
+    101: Key.F9,
+    109: Key.F9,
+    115: Key.HOME,
+    116: Key.PAGE_UP,
+    117: Key.DELETE,
+    119: Key.END,
+    120: Key.F2,
+    121: Key.PAGE_DOWN,
+    122: Key.F1,
+    123: Key.LEFT,
+    124: Key.RIGHT,
+    125: Key.DOWN,
+    126: Key.UP,
+}
 
-def modified_key(key, shift=None):
-    def mod_fn(modifierFlags):
-        if modifierFlags & NSEventModifierFlagShift:
-            return shift
-        return key
-
-    return mod_fn
+# Keys that have a different Toga key when Shift is pressed.
+TOGA_SHIFT_MODIFIED = {
+    Key._1: Key.EXCLAMATION,
+    Key._2: Key.AT,
+    Key._3: Key.HASH,
+    Key._4: Key.DOLLAR,
+    Key._6: Key.CARET,
+    Key._5: Key.PERCENT,
+    Key.PLUS: Key.EQUAL,
+    Key._9: Key.OPEN_PARENTHESIS,
+    Key._7: Key.AMPERSAND,
+    Key.MINUS: Key.UNDERSCORE,
+    Key._8: Key.ASTERISK,
+    Key._0: Key.CLOSE_PARENTHESIS,
+    Key.CLOSE_BRACKET: Key.CLOSE_BRACKET,
+    Key.OPEN_BRACKET: Key.OPEN_BRACKET,
+    Key.ENTER: Key.ENTER,
+    Key.QUOTE: Key.DOUBLE_QUOTE,
+    Key.COLON: Key.SEMICOLON,
+    Key.COMMA: Key.LESS_THAN,
+    Key.SLASH: Key.QUESTION,
+    Key.FULL_STOP: Key.GREATER_THAN,
+    Key.BACK_QUOTE: Key.TILDE,
+}
 
 
 def toga_key(event):
     """Convert a Cocoa NSKeyEvent into a Toga event."""
-    key = {
-        0: Key.A,
-        1: Key.S,
-        2: Key.D,
-        3: Key.F,
-        4: Key.H,
-        5: Key.G,
-        6: Key.Z,
-        7: Key.X,
-        8: Key.C,
-        9: Key.V,
-        11: Key.B,
-        12: Key.Q,
-        13: Key.W,
-        14: Key.E,
-        15: Key.R,
-        16: Key.Y,
-        17: Key.T,
-        18: modified_key(Key._1, shift=Key.EXCLAMATION)(event.modifierFlags),
-        19: modified_key(Key._2, shift=Key.AT)(event.modifierFlags),
-        20: modified_key(Key._3, shift=Key.HASH)(event.modifierFlags),
-        21: modified_key(Key._4, shift=Key.DOLLAR)(event.modifierFlags),
-        22: modified_key(Key._6, shift=Key.CARET)(event.modifierFlags),
-        23: modified_key(Key._5, shift=Key.PERCENT)(event.modifierFlags),
-        24: modified_key(Key.PLUS, shift=Key.EQUAL)(event.modifierFlags),
-        25: modified_key(Key._9, shift=Key.OPEN_PARENTHESIS)(event.modifierFlags),
-        26: modified_key(Key._7, shift=Key.AMPERSAND)(event.modifierFlags),
-        27: modified_key(Key.MINUS, shift=Key.UNDERSCORE)(event.modifierFlags),
-        28: modified_key(Key._8, shift=Key.ASTERISK)(event.modifierFlags),
-        29: modified_key(Key._0, shift=Key.CLOSE_PARENTHESIS)(event.modifierFlags),
-        30: Key.CLOSE_BRACKET,
-        31: Key.O,
-        32: Key.U,
-        33: Key.OPEN_BRACKET,
-        34: Key.I,
-        35: Key.P,
-        36: Key.ENTER,
-        37: Key.L,
-        38: Key.J,
-        39: modified_key(Key.QUOTE, shift=Key.DOUBLE_QUOTE)(event.modifierFlags),
-        40: Key.K,
-        41: modified_key(Key.COLON, shift=Key.SEMICOLON)(event.modifierFlags),
-        42: Key.BACKSLASH,
-        43: modified_key(Key.COMMA, shift=Key.LESS_THAN)(event.modifierFlags),
-        44: modified_key(Key.SLASH, shift=Key.QUESTION)(event.modifierFlags),
-        45: Key.N,
-        46: Key.M,
-        47: modified_key(Key.FULL_STOP, shift=Key.GREATER_THAN)(event.modifierFlags),
-        48: Key.TAB,
-        49: Key.SPACE,
-        50: modified_key(Key.BACK_QUOTE, shift=Key.TILDE)(event.modifierFlags),
-        51: Key.BACKSPACE,
-        53: Key.ESCAPE,
-        65: Key.NUMPAD_DECIMAL_POINT,
-        67: Key.NUMPAD_MULTIPLY,
-        69: Key.NUMPAD_PLUS,
-        71: Key.NUMPAD_CLEAR,
-        75: Key.NUMPAD_DIVIDE,
-        76: Key.NUMPAD_ENTER,
-        78: Key.NUMPAD_MINUS,
-        81: Key.NUMPAD_EQUAL,
-        82: Key.NUMPAD_0,
-        83: Key.NUMPAD_1,
-        84: Key.NUMPAD_2,
-        85: Key.NUMPAD_3,
-        86: Key.NUMPAD_4,
-        87: Key.NUMPAD_5,
-        88: Key.NUMPAD_6,
-        89: Key.NUMPAD_7,
-        91: Key.NUMPAD_8,
-        92: Key.NUMPAD_9,
-        # : Key.F4,
-        96: Key.F5,
-        97: Key.F7,
-        98: Key.F5,
-        99: Key.F3,
-        100: Key.F8,
-        101: Key.F9,
-        109: Key.F9,
-        115: Key.HOME,
-        116: Key.PAGE_UP,
-        117: Key.DELETE,
-        119: Key.END,
-        120: Key.F2,
-        121: Key.PAGE_DOWN,
-        122: Key.F1,
-        123: Key.LEFT,
-        124: Key.RIGHT,
-        125: Key.DOWN,
-        126: Key.UP,
-    }.get(event.keyCode, None)
+    natural_key = TOGA_KEYS.get(event.keyCode, None)
+    if event.modifierFlags & NSEventModifierFlagShift:
+        try:
+            key = TOGA_SHIFT_MODIFIED[natural_key]
+        except KeyError:
+            key = natural_key
+    else:
+        key = natural_key
 
     modifiers = set()
 
-    if event.modifierFlags & NSEventModifierFlagCapsLock:
-        modifiers.add(Key.CAPSLOCK)
-    if event.modifierFlags & NSEventModifierFlagShift:
+    # Only apply a shift modifier for the a/A case.
+    # keys like ! that inherently need shift don't return as modified.
+    if event.modifierFlags & NSEventModifierFlagShift and key == natural_key:
         modifiers.add(Key.SHIFT)
     if event.modifierFlags & NSEventModifierFlagCommand:
         modifiers.add(Key.MOD_1)
@@ -130,39 +155,39 @@ def toga_key(event):
 
 
 COCOA_KEY_CODES = {
-    Key.ESCAPE: "%c" % 0x001B,
-    Key.TAB: "%c" % 0x0009,
-    Key.BACKSPACE: "%c" % 0x0008,
-    Key.ENTER: "%c" % 0x000D,
-    Key.F1: "",  # TODO
-    Key.F2: "",  # TODO
-    Key.F3: "",  # TODO
-    Key.F4: "",  # TODO
-    Key.F5: "",  # TODO
-    Key.F6: "",  # TODO
-    Key.F7: "",  # TODO
-    Key.F8: "",  # TODO
-    Key.F9: "",  # TODO
-    Key.F10: "",  # TODO
-    Key.F11: "",  # TODO
-    Key.F12: "",  # TODO
-    Key.F13: "",  # TODO
-    Key.F14: "",  # TODO
-    Key.F15: "",  # TODO
-    Key.F16: "",  # TODO
-    Key.F17: "",  # TODO
-    Key.F18: "",  # TODO
-    Key.F19: "",  # TODO
+    Key.ESCAPE: chr(0x001B),
+    Key.TAB: chr(0x0009),
+    Key.BACKSPACE: chr(0x0008),
+    Key.ENTER: chr(0x000D),
+    Key.F1: chr(0xF704),
+    Key.F2: chr(0xF705),
+    Key.F3: chr(0xF706),
+    Key.F4: chr(0xF707),
+    Key.F5: chr(0xF708),
+    Key.F6: chr(0xF709),
+    Key.F7: chr(0xF70A),
+    Key.F8: chr(0xF70B),
+    Key.F9: chr(0xF70C),
+    Key.F10: chr(0xF70D),
+    Key.F11: chr(0xF70E),
+    Key.F12: chr(0xF70F),
+    Key.F13: chr(0xF710),
+    Key.F14: chr(0xF711),
+    Key.F15: chr(0xF712),
+    Key.F16: chr(0xF713),
+    Key.F17: chr(0xF714),
+    Key.F18: chr(0xF715),
+    Key.F19: chr(0xF716),
     Key.EJECT: "",  # TODO
-    Key.HOME: "%c" % 0x2196,
-    Key.END: "%c" % 0x2198,
-    Key.DELETE: "%c" % 0x007F,
-    Key.PAGE_UP: "%c" % 0x21DE,
-    Key.PAGE_DOWN: "%c" % 0x21DF,
-    Key.UP: "%c" % 0x001E,
-    Key.DOWN: "%c" % 0x001F,
-    Key.LEFT: "%c" % 0x001C,
-    Key.RIGHT: "%c" % 0x001D,
+    Key.HOME: chr(0x2196),
+    Key.END: chr(0x2198),
+    Key.DELETE: chr(0x007F),
+    Key.PAGE_UP: chr(0x21DE),
+    Key.PAGE_DOWN: chr(0x21DF),
+    Key.UP: chr(0x001E),
+    Key.DOWN: chr(0x001F),
+    Key.LEFT: chr(0x001C),
+    Key.RIGHT: chr(0x001D),
     Key.NUMPAD_0: "0",
     Key.NUMPAD_1: "1",
     Key.NUMPAD_2: "2",
@@ -174,18 +199,17 @@ def toga_key(event):
     Key.NUMPAD_8: "8",
     Key.NUMPAD_9: "9",
     Key.NUMPAD_CLEAR: "",  # TODO
-    Key.NUMPAD_DECIMAL_POINT: "",  # TODO
-    Key.NUMPAD_DIVIDE: "",  # TODO
-    Key.NUMPAD_ENTER: "",  # TODO
-    Key.NUMPAD_EQUAL: "",  # TODO
-    Key.NUMPAD_MINUS: "",  # TODO
-    Key.NUMPAD_MULTIPLY: "",  # TODO
-    Key.NUMPAD_PLUS: "",  # TODO
+    Key.NUMPAD_DECIMAL_POINT: ".",
+    Key.NUMPAD_DIVIDE: "/",
+    Key.NUMPAD_ENTER: chr(0x000D),
+    Key.NUMPAD_EQUAL: "=",
+    Key.NUMPAD_MINUS: "-",
+    Key.NUMPAD_MULTIPLY: "*",
+    Key.NUMPAD_PLUS: "+",
 }
 
 COCOA_MODIFIERS = {
     Key.SHIFT: NSEventModifierFlagShift,
-    Key.CAPSLOCK: NSEventModifierFlagCapsLock,
     Key.MOD_1: NSEventModifierFlagCommand,
     Key.MOD_2: NSEventModifierFlagOption,
     Key.MOD_3: NSEventModifierFlagControl,
@@ -213,4 +237,8 @@ def cocoa_key(shortcut):
             key = key.replace(mod.value, "")
             modifiers |= mask
 
+    # If the remaining key string is upper case, add a shift modifier.
+    if key.isupper():
+        modifiers |= NSEventModifierFlagShift
+
     return key, modifiers
diff --git a/cocoa/src/toga_cocoa/widgets/button.py b/cocoa/src/toga_cocoa/widgets/button.py
index 1eb11323de..75b4976b15 100644
--- a/cocoa/src/toga_cocoa/widgets/button.py
+++ b/cocoa/src/toga_cocoa/widgets/button.py
@@ -22,7 +22,7 @@ class TogaButton(NSButton):
 
     @objc_method
     def onPress_(self, obj) -> None:
-        self.interface.on_press(None)
+        self.interface.on_press()
 
 
 class Button(Widget):
diff --git a/cocoa/src/toga_cocoa/widgets/canvas.py b/cocoa/src/toga_cocoa/widgets/canvas.py
index 1df8900f8a..d8c8ca8305 100644
--- a/cocoa/src/toga_cocoa/widgets/canvas.py
+++ b/cocoa/src/toga_cocoa/widgets/canvas.py
@@ -1,4 +1,3 @@
-from ctypes import POINTER, c_char, cast
 from math import ceil
 
 from rubicon.objc import objc_method, objc_property
@@ -7,6 +6,7 @@
 from toga.colors import BLACK, TRANSPARENT, color
 from toga.widgets.canvas import Baseline, FillRule
 from toga_cocoa.colors import native_color
+from toga_cocoa.images import nsdata_to_bytes
 from toga_cocoa.libs import (
     CGFloat,
     CGPathDrawingMode,
@@ -50,34 +50,34 @@ def isFlipped(self) -> bool:
     def mouseDown_(self, event) -> None:
         position = self.convertPoint(event.locationInWindow, fromView=None)
         if event.clickCount == 1:
-            self.interface.on_press(None, position.x, position.y)
+            self.interface.on_press(position.x, position.y)
         else:
-            self.interface.on_activate(None, position.x, position.y)
+            self.interface.on_activate(position.x, position.y)
 
     @objc_method
     def rightMouseDown_(self, event) -> None:
         position = self.convertPoint(event.locationInWindow, fromView=None)
-        self.interface.on_alt_press(None, position.x, position.y)
+        self.interface.on_alt_press(position.x, position.y)
 
     @objc_method
     def mouseUp_(self, event) -> None:
         position = self.convertPoint(event.locationInWindow, fromView=None)
-        self.interface.on_release(None, position.x, position.y)
+        self.interface.on_release(position.x, position.y)
 
     @objc_method
     def rightMouseUp_(self, event) -> None:
         position = self.convertPoint(event.locationInWindow, fromView=None)
-        self.interface.on_alt_release(None, position.x, position.y)
+        self.interface.on_alt_release(position.x, position.y)
 
     @objc_method
     def mouseDragged_(self, event) -> None:
         position = self.convertPoint(event.locationInWindow, fromView=None)
-        self.interface.on_drag(None, position.x, position.y)
+        self.interface.on_drag(position.x, position.y)
 
     @objc_method
     def rightMouseDragged_(self, event) -> None:
         position = self.convertPoint(event.locationInWindow, fromView=None)
-        self.interface.on_alt_drag(None, position.x, position.y)
+        self.interface.on_alt_drag(position.x, position.y)
 
 
 class Canvas(Widget):
@@ -94,7 +94,7 @@ def redraw(self):
 
     def set_bounds(self, x, y, width, height):
         super().set_bounds(x, y, width, height)
-        self.interface.on_resize(None, width=width, height=height)
+        self.interface.on_resize(width=width, height=height)
 
     def set_background_color(self, color):
         if color is TRANSPARENT or color is None:
@@ -325,15 +325,12 @@ def get_image_data(self):
         bitmap.setSize(self.native.bounds.size)
         self.native.cacheDisplayInRect(self.native.bounds, toBitmapImageRep=bitmap)
 
-        data = bitmap.representationUsingType(
-            NSBitmapImageFileType.PNG,
-            properties=None,
+        return nsdata_to_bytes(
+            bitmap.representationUsingType(
+                NSBitmapImageFileType.PNG,
+                properties=None,
+            )
         )
-        # data is an NSData object that has .bytes as a c_void_p, and a .length. Cast to
-        # POINTER(c_char) to get an addressable array of bytes, and slice that array to
-        # the known length. We don't use c_char_p because it has handling of NUL
-        # termination, and POINTER(c_char) allows array subscripting.
-        return cast(data.bytes, POINTER(c_char))[: data.length]
 
     # Rehint
     def rehint(self):
diff --git a/cocoa/src/toga_cocoa/widgets/detailedlist.py b/cocoa/src/toga_cocoa/widgets/detailedlist.py
index b5566d19a2..6745cb694a 100644
--- a/cocoa/src/toga_cocoa/widgets/detailedlist.py
+++ b/cocoa/src/toga_cocoa/widgets/detailedlist.py
@@ -56,12 +56,12 @@ def menuForEvent_(self, event):
     @objc_method
     def primaryActionOnRow_(self, menuitem):
         row = self.interface.data[menuitem.tag]
-        self.interface.on_primary_action(self.interface, row=row)
+        self.interface.on_primary_action(row=row)
 
     @objc_method
     def secondaryActionOnRow_(self, menuitem):
         row = self.interface.data[menuitem.tag]
-        self.interface.on_secondary_action(self.interface, row=row)
+        self.interface.on_secondary_action(row=row)
 
     # TableDataSource methods
     @objc_method
@@ -122,7 +122,7 @@ def selectionShouldChangeInTableView_(self, table) -> bool:
 
     @objc_method
     def tableViewSelectionDidChange_(self, notification) -> None:
-        self.interface.on_select(self.interface)
+        self.interface.on_select()
 
 
 class DetailedList(Widget):
@@ -180,7 +180,7 @@ def remove(self, index, item):
 
         # After deletion, the selection changes, but Cocoa doesn't send
         # a tableViewSelectionDidChange: message.
-        self.interface.on_select(self.interface)
+        self.interface.on_select()
 
     def clear(self):
         self.native_detailedlist.reloadData()
diff --git a/cocoa/src/toga_cocoa/widgets/internal/refresh.py b/cocoa/src/toga_cocoa/widgets/internal/refresh.py
index 2c6ee33717..c4abaa2df9 100644
--- a/cocoa/src/toga_cocoa/widgets/internal/refresh.py
+++ b/cocoa/src/toga_cocoa/widgets/internal/refresh.py
@@ -273,7 +273,7 @@ def scrollWheel_(self, event) -> None:
                 NSMakePoint(self.contentView.bounds.origin.x, -HEADER_HEIGHT)
             )
             self.refresh_indicator.startAnimation(self)
-            self.interface.on_refresh(self.interface)
+            self.interface.on_refresh()
 
         send_super(__class__, self, "scrollWheel:", event, argtypes=[c_void_p])
 
diff --git a/cocoa/src/toga_cocoa/widgets/multilinetextinput.py b/cocoa/src/toga_cocoa/widgets/multilinetextinput.py
index b08fa86c1f..c651fa8e47 100644
--- a/cocoa/src/toga_cocoa/widgets/multilinetextinput.py
+++ b/cocoa/src/toga_cocoa/widgets/multilinetextinput.py
@@ -21,7 +21,7 @@ class TogaTextView(NSTextView):
 
     @objc_method
     def textDidChange_(self, notification) -> None:
-        self.interface.on_change(None)
+        self.interface.on_change()
 
 
 class MultilineTextInput(Widget):
@@ -78,7 +78,7 @@ def get_value(self):
 
     def set_value(self, value):
         self.native_text.string = value
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def set_color(self, value):
         self.native_text.textColor = native_color(value)
diff --git a/cocoa/src/toga_cocoa/widgets/numberinput.py b/cocoa/src/toga_cocoa/widgets/numberinput.py
index e9b93e7812..906ebbbee2 100644
--- a/cocoa/src/toga_cocoa/widgets/numberinput.py
+++ b/cocoa/src/toga_cocoa/widgets/numberinput.py
@@ -47,7 +47,7 @@ def controlTextDidChange_(self, notification) -> None:
             # would make it invalid.
             self.impl.native_input.stringValue = _clean_decimal_str(value)
 
-        self.interface.on_change(self.interface)
+        self.interface.on_change()
 
 
 class TogaNumberInput(NSTextField):
@@ -234,7 +234,7 @@ def set_value(self, value):
         else:
             self.native_stepper.floatValue = float(value)
             self.native_input.stringValue = str(value)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_enabled(self):
         return self.native_input.isEnabled
diff --git a/cocoa/src/toga_cocoa/widgets/optioncontainer.py b/cocoa/src/toga_cocoa/widgets/optioncontainer.py
index 66566470ea..1057afdff9 100644
--- a/cocoa/src/toga_cocoa/widgets/optioncontainer.py
+++ b/cocoa/src/toga_cocoa/widgets/optioncontainer.py
@@ -26,7 +26,7 @@ def tabView_didSelectTabViewItem_(self, view, item) -> None:
         container.content.interface.refresh()
 
         # Notify of the change in selection.
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     @objc_method
     def refreshContent(self) -> None:
diff --git a/cocoa/src/toga_cocoa/widgets/scrollcontainer.py b/cocoa/src/toga_cocoa/widgets/scrollcontainer.py
index 5c9226e22b..40721bdeee 100644
--- a/cocoa/src/toga_cocoa/widgets/scrollcontainer.py
+++ b/cocoa/src/toga_cocoa/widgets/scrollcontainer.py
@@ -22,7 +22,7 @@ class TogaScrollView(NSScrollView):
 
     @objc_method
     def didScroll_(self, note) -> None:
-        self.interface.on_scroll(None)
+        self.interface.on_scroll()
 
     @objc_method
     def refreshContent(self):
@@ -109,7 +109,7 @@ def set_vertical(self, value):
 
         # Disabling scrolling implies a position reset; that's a scroll event.
         if not value:
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
 
     def get_horizontal(self):
         return self.native.hasHorizontalScroller
@@ -123,7 +123,7 @@ def set_horizontal(self, value):
 
         # Disabling scrolling implies a position reset; that's a scroll event.
         if not value:
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
 
     def rehint(self):
         self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
@@ -161,4 +161,4 @@ def set_position(self, horizontal_position, vertical_position):
         new_position = NSMakePoint(horizontal_position, vertical_position)
         self.native.contentView.scrollToPoint(new_position)
         self.native.reflectScrolledClipView(self.native.contentView)
-        self.interface.on_scroll(None)
+        self.interface.on_scroll()
diff --git a/cocoa/src/toga_cocoa/widgets/selection.py b/cocoa/src/toga_cocoa/widgets/selection.py
index a846c32c99..e0a3bfd52e 100644
--- a/cocoa/src/toga_cocoa/widgets/selection.py
+++ b/cocoa/src/toga_cocoa/widgets/selection.py
@@ -11,7 +11,7 @@ class TogaPopupButton(NSPopUpButton):
 
     @objc_method
     def onSelect_(self, obj) -> None:
-        self.interface.on_change(None)
+        self.interface.on_change()
 
 
 class Selection(Widget):
@@ -41,7 +41,7 @@ def insert(self, index, item):
         # If this is the first time item in the list, it will be automatically
         # selected; trigger a change event.
         if len(self.interface.items) == 1:
-            self.interface.on_change(None)
+            self.interface.on_change()
 
     def change(self, item):
         index = self.interface._items.index(item)
@@ -56,15 +56,15 @@ def remove(self, index, item):
         self.native.removeItemAtIndex(index)
 
         if selection_change:
-            self.interface.on_change(None)
+            self.interface.on_change()
 
     def clear(self):
         self.native.removeAllItems()
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def select_item(self, index, item):
         self.native.selectItemAtIndex(index)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_selected_index(self):
         index = self.native.indexOfSelectedItem
diff --git a/cocoa/src/toga_cocoa/widgets/slider.py b/cocoa/src/toga_cocoa/widgets/slider.py
index bf80d24a4f..98d86b9642 100644
--- a/cocoa/src/toga_cocoa/widgets/slider.py
+++ b/cocoa/src/toga_cocoa/widgets/slider.py
@@ -20,11 +20,11 @@ class TogaSlider(NSSlider):
     def onSlide_(self, sender) -> None:
         event_type = sender.window.currentEvent().type
         if event_type == NSEventType.LeftMouseDown:
-            self.interface.on_press(None)
+            self.interface.on_press()
         elif event_type == NSEventType.LeftMouseUp:
-            self.interface.on_release(None)
+            self.interface.on_release()
 
-        self.interface.on_change(None)
+        self.interface.on_change()
 
 
 class Slider(Widget, toga.widgets.slider.SliderImpl):
diff --git a/cocoa/src/toga_cocoa/widgets/switch.py b/cocoa/src/toga_cocoa/widgets/switch.py
index 666ec2393f..15f92bc6aa 100644
--- a/cocoa/src/toga_cocoa/widgets/switch.py
+++ b/cocoa/src/toga_cocoa/widgets/switch.py
@@ -20,7 +20,7 @@ class TogaSwitch(NSButton):
 
     @objc_method
     def onPress_(self, obj) -> None:
-        self.interface.on_change(None)
+        self.interface.on_change()
 
 
 class Switch(Widget):
@@ -53,7 +53,7 @@ def set_value(self, value):
         old_value = self.native.state == NSOnState
         self.native.state = NSOnState if value else NSOffState
         if self.interface.on_change and value != old_value:
-            self.interface.on_change(self.interface)
+            self.interface.on_change()
 
     def rehint(self):
         content_size = self.native.intrinsicContentSize()
diff --git a/cocoa/src/toga_cocoa/widgets/table.py b/cocoa/src/toga_cocoa/widgets/table.py
index 6e0c616432..d9c218e82d 100644
--- a/cocoa/src/toga_cocoa/widgets/table.py
+++ b/cocoa/src/toga_cocoa/widgets/table.py
@@ -1,11 +1,7 @@
-from ctypes import c_void_p
-
-from rubicon.objc import SEL, at, objc_method, objc_property, send_super
+from rubicon.objc import SEL, at, objc_method, objc_property
 from travertino.size import at_least
 
 import toga
-from toga.keys import Key
-from toga_cocoa.keys import toga_key
 from toga_cocoa.libs import (
     NSBezelBorder,
     NSIndexSet,
@@ -83,16 +79,6 @@ def tableView_pasteboardWriterForRow_(self, table, row) -> None:  # pragma: no c
         # this seems to be required to prevent issue 21562075 in AppKit
         return None
 
-    @objc_method
-    def keyDown_(self, event) -> None:
-        # any time this table is in focus and a key is pressed, this method will be called
-        if toga_key(event) == {"key": Key.A, "modifiers": {Key.MOD_1}}:
-            if self.interface.multiple_select:
-                self.selectAll(self)
-        else:
-            # forward call to super
-            send_super(__class__, self, "keyDown:", event, argtypes=[c_void_p])
-
     # TableDelegate methods
     @objc_method
     def selectionShouldChangeInTableView_(self, table) -> bool:
@@ -102,7 +88,7 @@ def selectionShouldChangeInTableView_(self, table) -> bool:
 
     @objc_method
     def tableViewSelectionDidChange_(self, notification) -> None:
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     # 2021-09-04: Commented out this method because it appears to be a
     # source of significant slowdown when the table has a lot of data
@@ -133,7 +119,7 @@ def tableViewSelectionDidChange_(self, notification) -> None:
     def onDoubleClick_(self, sender) -> None:
         clicked = self.interface.data[self.clickedRow]
 
-        self.interface.on_activate(None, row=clicked)
+        self.interface.on_activate(row=clicked)
 
 
 class Table(Widget):
diff --git a/cocoa/src/toga_cocoa/widgets/textinput.py b/cocoa/src/toga_cocoa/widgets/textinput.py
index 2cf47cd812..ee7f762e98 100644
--- a/cocoa/src/toga_cocoa/widgets/textinput.py
+++ b/cocoa/src/toga_cocoa/widgets/textinput.py
@@ -38,17 +38,17 @@ class TogaTextFieldProxy:
 
     @staticmethod
     def textDidChange_(cls, self, notification) -> None:
-        self.interface.on_change(None)
+        self.interface.on_change()
         self.interface._validate()
 
     @staticmethod
     def becomeFirstResponder(cls, self) -> bool:
-        self.interface.on_gain_focus(self.interface)
+        self.interface.on_gain_focus()
         return send_super(cls, self, "becomeFirstResponder")
 
     @staticmethod
     def textDidEndEditing_(cls, self, textObject) -> None:
-        self.interface.on_lose_focus(self.interface)
+        self.interface.on_lose_focus()
         send_super(cls, self, "textDidEndEditing:", textObject, argtypes=[c_void_p])
 
     @staticmethod
@@ -60,7 +60,7 @@ def control_textView_doCommandBySelector_(
         selector: SEL,
     ) -> bool:
         if selector.name == b"insertNewline:":
-            self.interface.on_confirm(None)
+            self.interface.on_confirm()
         return False
 
 
@@ -213,7 +213,7 @@ def get_value(self):
 
     def set_value(self, value):
         self.native.stringValue = value
-        self.interface.on_change(None)
+        self.interface.on_change()
         self.interface._validate()
 
     def rehint(self):
diff --git a/cocoa/src/toga_cocoa/widgets/tree.py b/cocoa/src/toga_cocoa/widgets/tree.py
index 6af99f1774..fb206f7558 100644
--- a/cocoa/src/toga_cocoa/widgets/tree.py
+++ b/cocoa/src/toga_cocoa/widgets/tree.py
@@ -1,11 +1,7 @@
-from ctypes import c_void_p
-
-from rubicon.objc import SEL, at, objc_method, objc_property, send_super
+from rubicon.objc import SEL, at, objc_method, objc_property
 from travertino.size import at_least
 
 import toga
-from toga.keys import Key
-from toga_cocoa.keys import toga_key
 from toga_cocoa.libs import (
     NSBezelBorder,
     NSIndexSet,
@@ -159,26 +155,16 @@ def outlineView_pasteboardWriterForItem_(
     #         else:
     #             self.reloadData()
 
-    @objc_method
-    def keyDown_(self, event) -> None:
-        # any time this table is in focus and a key is pressed, this method will be called
-        if toga_key(event) == {"key": Key.A, "modifiers": {Key.MOD_1}}:
-            if self.interface.multiple_select:
-                self.selectAll(self)
-        else:
-            # forward call to super
-            send_super(__class__, self, "keyDown:", event, argtypes=[c_void_p])
-
     # OutlineViewDelegate methods
     @objc_method
     def outlineViewSelectionDidChange_(self, notification) -> None:
-        self.interface.on_select(self.interface)
+        self.interface.on_select()
 
     # target methods
     @objc_method
     def onDoubleClick_(self, sender) -> None:
         node = self.itemAtRow(self.clickedRow).attrs["node"]
-        self.interface.on_activate(self.interface, node=node)
+        self.interface.on_activate(node=node)
 
 
 class Tree(Widget):
diff --git a/cocoa/src/toga_cocoa/widgets/webview.py b/cocoa/src/toga_cocoa/widgets/webview.py
index 63e51123f3..925164fa59 100644
--- a/cocoa/src/toga_cocoa/widgets/webview.py
+++ b/cocoa/src/toga_cocoa/widgets/webview.py
@@ -1,5 +1,4 @@
-from rubicon.objc import objc_method, objc_property, py_from_ns
-from rubicon.objc.runtime import objc_id
+from rubicon.objc import objc_id, objc_method, objc_property, py_from_ns
 from travertino.size import at_least
 
 from toga.widgets.webview import JavaScriptResult
@@ -31,7 +30,7 @@ class TogaWebView(WKWebView):
 
     @objc_method
     def webView_didFinishNavigation_(self, navigation) -> None:
-        self.interface.on_webview_load(self.interface)
+        self.interface.on_webview_load()
 
         if self.impl.loaded_future:
             self.impl.loaded_future.set_result(None)
diff --git a/cocoa/src/toga_cocoa/window.py b/cocoa/src/toga_cocoa/window.py
index 3ac7332313..e1d82e1cd6 100644
--- a/cocoa/src/toga_cocoa/window.py
+++ b/cocoa/src/toga_cocoa/window.py
@@ -1,8 +1,10 @@
-from toga.command import Command as BaseCommand
+from toga.command import Command
 from toga_cocoa.container import Container
+from toga_cocoa.images import nsdata_to_bytes
 from toga_cocoa.libs import (
     SEL,
     NSBackingStoreBuffered,
+    NSBitmapImageFileType,
     NSMakeRect,
     NSMutableArray,
     NSPoint,
@@ -18,7 +20,10 @@
 
 
 def toolbar_identifier(cmd):
-    return "ToolbarItem-%s" % id(cmd)
+    if isinstance(cmd, Command):
+        return "ToolbarItem-%s" % id(cmd)
+    else:
+        return "ToolbarSeparator-%s" % id(cmd)
 
 
 class TogaWindow(NSWindow):
@@ -40,10 +45,11 @@ def windowDidResize_(self, notification) -> None:
     ######################################################################
 
     @objc_method
-    def toolbarAllowedItemIdentifiers_(self, toolbar):
+    def toolbarAllowedItemIdentifiers_(self, toolbar):  # pragma: no cover
         """Determine the list of available toolbar items."""
-        # This method is required by the Cocoa API, but isn't actually invoked,
-        # because customizable toolbars are no longer a thing.
+        # This method is required by the Cocoa API, but it's only ever called if the
+        # toolbar allows user customization. We don't turn that option on so this method
+        # can't ever be invoked - but we need to provide an implementation.
         allowed = NSMutableArray.alloc().init()
         for item in self.interface.toolbar:
             allowed.addObject_(toolbar_identifier(item))
@@ -59,25 +65,27 @@ def toolbarDefaultItemIdentifiers_(self, toolbar):
 
     @objc_method
     def toolbar_itemForItemIdentifier_willBeInsertedIntoToolbar_(
-        self, toolbar, identifier, insert: bool
+        self,
+        toolbar,
+        identifier,
+        insert: bool,
     ):
         """Create the requested toolbar button."""
         native = NSToolbarItem.alloc().initWithItemIdentifier_(identifier)
         try:
             item = self.impl._toolbar_items[str(identifier)]
-            if item.text:
-                native.setLabel(item.text)
-                native.setPaletteLabel(item.text)
+            native.setLabel(item.text)
+            native.setPaletteLabel(item.text)
             if item.tooltip:
                 native.setToolTip(item.tooltip)
             if item.icon:
                 native.setImage(item.icon._impl.native)
 
-            item._impl.native.append(native)
+            item._impl.native.add(native)
 
             native.setTarget_(self)
             native.setAction_(SEL("onToolbarButtonPress:"))
-        except KeyError:
+        except KeyError:  # Separator items
             pass
 
         # Prevent the toolbar item from being deallocated when
@@ -89,7 +97,14 @@ def toolbar_itemForItemIdentifier_willBeInsertedIntoToolbar_(
     @objc_method
     def validateToolbarItem_(self, item) -> bool:
         """Confirm if the toolbar item should be enabled."""
-        return self.impl._toolbar_items[str(item.itemIdentifier)].enabled
+        try:
+            return self.impl._toolbar_items[str(item.itemIdentifier)].enabled
+        except KeyError:  # pragma: nocover
+            # This branch *shouldn't* ever happen; but there's an edge
+            # case where a toolbar redraw happens in the middle of deleting
+            # a toolbar item that can't be reliably reproduced, so it sometimes
+            # happens in testing.
+            return False
 
     ######################################################################
     # Toolbar button press delegate methods
@@ -99,7 +114,7 @@ def validateToolbarItem_(self, item) -> bool:
     def onToolbarButtonPress_(self, obj) -> None:
         """Invoke the action tied to the toolbar button."""
         item = self.impl._toolbar_items[str(obj.itemIdentifier)]
-        item.action(obj)
+        item.action()
 
 
 class Window:
@@ -130,7 +145,8 @@ def __init__(self, interface, title, position, size):
 
         # Cocoa releases windows when they are closed; this causes havoc with
         # Toga's widget cleanup because the ObjC runtime thinks there's no
-        # references to the object left. Add an explicit reference to the window.
+        # references to the object left. Add a reference that can be released
+        # in response to the close.
         self.native.retain()
 
         self.set_title(title)
@@ -142,21 +158,60 @@ def __init__(self, interface, title, position, size):
         self.container = Container(on_refresh=self.content_refreshed)
         self.native.contentView = self.container.native
 
+        # Ensure that the container renders it's background in the same color as the window.
+        self.native.wantsLayer = True
+        self.container.native.backgroundColor = self.native.backgroundColor
+
+        # By default, no toolbar
+        self._toolbar_items = {}
+        self.native_toolbar = None
+
     def __del__(self):
+        self.purge_toolbar()
         self.native.release()
 
+    def purge_toolbar(self):
+        while self._toolbar_items:
+            dead_items = []
+            _, cmd = self._toolbar_items.popitem()
+            # The command might have toolbar representations on multiple window
+            # toolbars, and may have other representations (at the very least, a menu
+            # item). Only clean up the representation pointing at *this* window. Do this
+            # in 2 passes so that we're not modifying the set of native objects while
+            # iterating over it.
+            for item_native in cmd._impl.native:
+                if (
+                    isinstance(item_native, NSToolbarItem)
+                    and item_native.target == self.native
+                ):
+                    dead_items.append(item_native)
+
+            for item_native in dead_items:
+                cmd._impl.native.remove(item_native)
+                item_native.release()
+
     def create_toolbar(self):
-        self._toolbar_items = {}
-        for cmd in self.interface.toolbar:
-            if isinstance(cmd, BaseCommand):
-                self._toolbar_items[toolbar_identifier(cmd)] = cmd
+        # Purge any existing toolbar items
+        self.purge_toolbar()
 
-        self._toolbar_native = NSToolbar.alloc().initWithIdentifier(
-            "Toolbar-%s" % id(self)
-        )
-        self._toolbar_native.setDelegate(self.native)
+        # Create the new toolbar items.
+        if self.interface.toolbar:
+            for cmd in self.interface.toolbar:
+                if isinstance(cmd, Command):
+                    self._toolbar_items[toolbar_identifier(cmd)] = cmd
+
+            self.native_toolbar = NSToolbar.alloc().initWithIdentifier(
+                "Toolbar-%s" % id(self)
+            )
+            self.native_toolbar.setDelegate(self.native)
+        else:
+            self.native_toolbar = None
 
-        self.native.setToolbar(self._toolbar_native)
+        self.native.setToolbar(self.native_toolbar)
+
+        # Adding/removing a toolbar changes the size of the content window.
+        if self.interface.content:
+            self.interface.content.refresh()
 
     def set_content(self, widget):
         # Set the content of the window's container
@@ -239,8 +294,22 @@ def cocoa_windowShouldClose(self):
         # The on_close handler has a cleanup method that will enforce
         # the close if the on_close handler requests it; this initial
         # "should close" request can always return False.
-        self.interface.on_close(None)
+        self.interface.on_close()
         return False
 
     def close(self):
         self.native.close()
+
+    def get_image_data(self):
+        bitmap = self.container.native.bitmapImageRepForCachingDisplayInRect(
+            self.container.native.bounds
+        )
+        bitmap.setSize(self.container.native.bounds.size)
+        self.container.native.cacheDisplayInRect(
+            self.container.native.bounds, toBitmapImageRep=bitmap
+        )
+        data = bitmap.representationUsingType(
+            NSBitmapImageFileType.PNG,
+            properties=None,
+        )
+        return nsdata_to_bytes(data)
diff --git a/cocoa/tests/__init__.py b/cocoa/tests/__init__.py
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/cocoa/tests/test_implementation.py b/cocoa/tests/test_implementation.py
deleted file mode 100644
index 39e6781b4c..0000000000
--- a/cocoa/tests/test_implementation.py
+++ /dev/null
@@ -1,13 +0,0 @@
-import os
-
-from toga_dummy import test_implementation
-
-globals().update(
-    test_implementation.create_impl_tests(
-        os.path.abspath(
-            os.path.join(
-                os.path.dirname(os.path.dirname(__file__)), "src", "toga_cocoa"
-            )
-        )
-    )
-)
diff --git a/cocoa/tests_backend/app.py b/cocoa/tests_backend/app.py
index e06b9e1c2b..ec9ffaea93 100644
--- a/cocoa/tests_backend/app.py
+++ b/cocoa/tests_backend/app.py
@@ -1,11 +1,24 @@
 from pathlib import Path
 
-from toga_cocoa.libs import NSApplication
+from rubicon.objc import NSPoint, ObjCClass, objc_id, send_message
+
+from toga_cocoa.keys import cocoa_key, toga_key
+from toga_cocoa.libs import (
+    NSApplication,
+    NSEvent,
+    NSEventModifierFlagShift,
+    NSEventType,
+)
 
 from .probe import BaseProbe
 
+NSPanel = ObjCClass("NSPanel")
+
 
 class AppProbe(BaseProbe):
+    supports_key = True
+    supports_key_mod3 = True
+
     def __init__(self, app):
         super().__init__()
         self.app = app
@@ -28,3 +41,136 @@ def cache_path(self):
     @property
     def logs_path(self):
         return Path.home() / "Library" / "Logs" / "org.beeware.toga.testbed"
+
+    @property
+    def is_cursor_visible(self):
+        # There's no API level mechanism to detect cursor visibility;
+        # fall back to the implementation's proxy variable.
+        return self.app._impl._cursor_visible
+
+    def is_full_screen(self, window):
+        return window.content._impl.native.isInFullScreenMode()
+
+    def content_size(self, window):
+        return (
+            window.content._impl.native.frame.size.width,
+            window.content._impl.native.frame.size.height,
+        )
+
+    def _menu_item(self, path):
+        main_menu = self.app._impl.native.mainMenu
+
+        menu = main_menu
+        orig_path = path.copy()
+        while True:
+            label, path = path[0], path[1:]
+            item = menu.itemWithTitle(label)
+            if item is None:
+                raise AssertionError(
+                    f"Menu {' > '.join(orig_path)} not found; "
+                    f"no item named {label!r}; options are: "
+                    + ",".join(f"{str(item.title)!r}" for item in menu.itemArray)
+                )
+
+            if path:
+                menu = item.submenu
+                if menu is None:
+                    raise AssertionError(
+                        f"Menu {' > '.join(orig_path)} not found; "
+                        f"{str(item.title)} does not have a submenu"
+                    )
+            else:
+                # No more path segments; we've found the full path.
+                break
+
+        return item
+
+    def _activate_menu_item(self, path):
+        item = self._menu_item(path)
+        send_message(
+            self.app._impl.native.delegate,
+            item.action,
+            item,
+            restype=None,
+            argtypes=[objc_id],
+        )
+
+    def activate_menu_exit(self):
+        self._activate_menu_item(["*", "Quit Toga Testbed"])
+
+    def activate_menu_about(self):
+        self._activate_menu_item(["*", "About Toga Testbed"])
+
+    async def close_about_dialog(self):
+        about_dialog = self.app._impl.native.keyWindow
+        if isinstance(about_dialog, NSPanel):
+            about_dialog.close()
+
+    def activate_menu_visit_homepage(self):
+        self._activate_menu_item(["Help", "Visit homepage"])
+
+    def assert_system_menus(self):
+        self.assert_menu_item(["*", "About Toga Testbed"], enabled=True)
+        self.assert_menu_item(["*", "Settings\u2026"], enabled=False)
+        self.assert_menu_item(["*", "Hide Toga Testbed"], enabled=True)
+        self.assert_menu_item(["*", "Hide Others"], enabled=True)
+        self.assert_menu_item(["*", "Show All"], enabled=True)
+        self.assert_menu_item(["*", "Quit Toga Testbed"], enabled=True)
+
+        self.assert_menu_item(["File", "Close"], enabled=True)
+        self.assert_menu_item(["File", "Close All"], enabled=True)
+
+        self.assert_menu_item(["Edit", "Undo"], enabled=True)
+        self.assert_menu_item(["Edit", "Redo"], enabled=True)
+        self.assert_menu_item(["Edit", "Cut"], enabled=True)
+        self.assert_menu_item(["Edit", "Copy"], enabled=True)
+        self.assert_menu_item(["Edit", "Paste"], enabled=True)
+        self.assert_menu_item(["Edit", "Paste and Match Style"], enabled=True)
+        self.assert_menu_item(["Edit", "Delete"], enabled=True)
+        self.assert_menu_item(["Edit", "Select All"], enabled=True)
+
+        self.assert_menu_item(["Window", "Minimize"], enabled=True)
+
+        self.assert_menu_item(["Help", "Visit homepage"], enabled=True)
+
+    def activate_menu_close_window(self):
+        self._activate_menu_item(["File", "Close"])
+
+    def activate_menu_close_all_windows(self):
+        self._activate_menu_item(["File", "Close All"])
+
+    def activate_menu_minimize(self):
+        self._activate_menu_item(["Window", "Minimize"])
+
+    def assert_menu_item(self, path, enabled):
+        item = self._menu_item(path)
+        assert item.isEnabled() == enabled
+
+    def keystroke(self, combination):
+        key, modifiers = cocoa_key(combination)
+        key_code = {
+            "a": 0,
+            "A": 0,
+            "1": 18,
+            "!": 18,
+            chr(0xF708): 96,  # F5
+            chr(0x2196): 115,  # Home
+        }[key]
+
+        # Add the shift modifier to disambiguate 1 from !
+        if key in {"!"}:
+            modifiers |= NSEventModifierFlagShift
+
+        event = NSEvent.keyEventWithType(
+            NSEventType.KeyDown,
+            location=NSPoint(0, 0),  # key presses don't have a location.
+            modifierFlags=modifiers,
+            timestamp=0,
+            windowNumber=self.app.main_window._impl.native.windowNumber,
+            context=None,
+            characters="?",
+            charactersIgnoringModifiers="?",
+            isARepeat=False,
+            keyCode=key_code,
+        )
+        return toga_key(event)
diff --git a/cocoa/tests_backend/probe.py b/cocoa/tests_backend/probe.py
index d28bfc049c..df70de74c7 100644
--- a/cocoa/tests_backend/probe.py
+++ b/cocoa/tests_backend/probe.py
@@ -59,3 +59,8 @@ async def redraw(self, message=None, delay=None):
             # Running at "normal" speed, we need to release to the event loop
             # for at least one iteration. `runUntilDate:None` does this.
             NSRunLoop.currentRunLoop.runUntilDate(None)
+
+    def assert_image_size(self, image_size, size):
+        # Cocoa reports image sizing in the natural screen coordinates, not the size of
+        # the backing store.
+        assert image_size == size
diff --git a/cocoa/tests_backend/widgets/canvas.py b/cocoa/tests_backend/widgets/canvas.py
index b91d1ebb37..cd2472ef0a 100644
--- a/cocoa/tests_backend/widgets/canvas.py
+++ b/cocoa/tests_backend/widgets/canvas.py
@@ -40,12 +40,6 @@ def get_image(self):
         except KeyError:
             return image
 
-    def assert_image_size(self, image, width, height):
-        # Cocoa reports image sizing in the natural screen coordinates, not the size of
-        # the backing store.
-        assert image.width == width
-        assert image.height == height
-
     async def mouse_press(self, x, y):
         await self.mouse_event(
             NSEventType.LeftMouseDown,
diff --git a/cocoa/tests_backend/window.py b/cocoa/tests_backend/window.py
index 285adbb978..eb7e7ef96d 100644
--- a/cocoa/tests_backend/window.py
+++ b/cocoa/tests_backend/window.py
@@ -1,5 +1,6 @@
 from unittest.mock import Mock
 
+from rubicon.objc import objc_id, send_message
 from rubicon.objc.collections import ObjCListInstance
 
 from toga_cocoa.libs import (
@@ -35,7 +36,7 @@ def __init__(self, app, window):
     async def wait_for_window(self, message, minimize=False, full_screen=False):
         await self.redraw(
             message,
-            delay=0.75 if full_screen else 0.5 if minimize else None,
+            delay=0.75 if full_screen else 0.5 if minimize else 0.1,
         )
 
     def close(self):
@@ -233,3 +234,28 @@ async def close_select_folder_dialog(self, dialog, result, multiple_select):
             f"{'Multiselect' if multiple_select else ' Select'} folder dialog "
             f"({'OPEN' if result else 'CANCEL'}) dismissed"
         )
+
+    def has_toolbar(self):
+        return self.native.toolbar is not None
+
+    def assert_is_toolbar_separator(self, index, section=False):
+        item = self.native.toolbar.items[index]
+        assert str(item.itemIdentifier).startswith("ToolbarSeparator-")
+
+    def assert_toolbar_item(self, index, label, tooltip, has_icon, enabled):
+        item = self.native.toolbar.items[index]
+
+        assert str(item.label) == label
+        assert (None if item.toolTip is None else str(item.toolTip)) == tooltip
+        assert (item.image is not None) == has_icon
+        assert item.isEnabled() == enabled
+
+    def press_toolbar_button(self, index):
+        item = self.native.toolbar.items[index]
+        send_message(
+            item.target,
+            item.action,
+            item,
+            restype=None,
+            argtypes=[objc_id],
+        )
diff --git a/core/setup.cfg b/core/setup.cfg
index dd9dbd8310..7b954d50ba 100644
--- a/core/setup.cfg
+++ b/core/setup.cfg
@@ -12,7 +12,7 @@ author_email = russell@keith-magee.com
 maintainer = BeeWare Team
 maintainer_email = team@beeware.org
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Intended Audience :: Developers
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
@@ -67,7 +67,7 @@ dev =
     pre-commit == 3.0.2
     pytest == 7.3.1
     pytest-asyncio == 0.21.0
-    pytest-freezegun == 0.4.2
+    pytest-freezer == 0.4.8
     setuptools-scm[toml] == 7.0.5
     tox == 4.3.5
 docs =
diff --git a/core/src/toga/__init__.py b/core/src/toga/__init__.py
index 1c8f24e6f4..705ee52e06 100644
--- a/core/src/toga/__init__.py
+++ b/core/src/toga/__init__.py
@@ -1,8 +1,8 @@
-from .app import App, DocumentApp, MainWindow
+from .app import App, DocumentApp, DocumentMainWindow, MainWindow
 
 # Resources
 from .colors import hsl, hsla, rgb, rgba
-from .command import GROUP_BREAK, SECTION_BREAK, Command, CommandSet, Group
+from .command import Command, Group
 from .documents import Document
 from .fonts import Font
 from .icons import Icon
@@ -42,12 +42,10 @@
     "App",
     "DocumentApp",
     "MainWindow",
+    "DocumentMainWindow",
     # Commands
     "Command",
-    "CommandSet",
     "Group",
-    "GROUP_BREAK",
-    "SECTION_BREAK",
     # Documents
     "Document",
     # Keys
diff --git a/core/src/toga/app.py b/core/src/toga/app.py
index 1b1c50986f..18d90c0cfa 100644
--- a/core/src/toga/app.py
+++ b/core/src/toga/app.py
@@ -1,16 +1,18 @@
 from __future__ import annotations
 
+import asyncio
+import importlib.metadata
 import signal
 import sys
 import warnings
 import webbrowser
-from builtins import id as identifier
-from collections.abc import MutableSet
+from collections.abc import Collection, Iterator, Mapping, MutableSet
 from email.message import Message
-from importlib import metadata as importlib_metadata
-from typing import Any, Iterable, Protocol
+from typing import Any, Protocol
+from warnings import warn
 
-from toga.command import CommandSet
+from toga.command import Command, CommandSet
+from toga.documents import Document
 from toga.handlers import wrapped_handler
 from toga.icons import Icon
 from toga.paths import Paths
@@ -28,11 +30,9 @@ def __call__(self, app: App, **kwargs: Any) -> Widget:
 
         Called during app startup to set the initial main window content.
 
-        .. note::
-            ``**kwargs`` ensures compatibility with additional arguments
-            introduced in future versions.
-
         :param app: The app instance that is starting.
+        :param kwargs: Ensures compatibility with additional arguments introduced in
+            future versions.
         :returns: The widget to use as the main window content.
         """
         ...
@@ -45,11 +45,9 @@ def __call__(self, app: App, **kwargs: Any) -> bool:
         The return value of this callback controls whether the app is allowed to exit.
         This can be used to prevent the app exiting with unsaved changes, etc.
 
-        .. note::
-            ``**kwargs`` ensures compatibility with additional arguments
-            introduced in future versions.
-
         :param app: The app instance that is exiting.
+        :param kwargs: Ensures compatibility with additional arguments introduced in
+            future versions.
         :returns: ``True`` if the app is allowed to exit; ``False`` if the app is not
             allowed to exit.
         """
@@ -60,30 +58,27 @@ class BackgroundTask(Protocol):
     def __call__(self, app: App, **kwargs: Any) -> None:
         """Code that should be executed as a background task.
 
-        .. note::
-            ``**kwargs`` ensures compatibility with additional arguments
-            introduced in future versions.
-
         :param app: The app that is handling the background task.
+        :param kwargs: Ensures compatibility with additional arguments introduced in
+            future versions.
         """
         ...
 
 
 class WindowSet(MutableSet):
-    """A collection of windows managed by an app.
-
-    A window can be added to app by using `app.windows.add(toga.Window(...))` or
-    `app.windows += toga.Window(...)` notations. Adding a window to app automatically
-    sets `window.app` property to the app.
-    """
+    def __init__(self, app: App):
+        """A collection of windows managed by an app.
 
-    def __init__(self, app: App, iterable: Iterable[Window] = ()):
+        A window is automatically added to the app when it is created, and removed when
+        it is closed. Adding a window to an App's window set automatically sets the
+        :attr:`~toga.Window.app` property of the Window.
+        """
         self.app = app
-        self.elements = set(iterable)
+        self.elements = set()
 
     def add(self, window: Window) -> None:
         if not isinstance(window, Window):
-            raise TypeError("Toga app.windows can only add objects of toga.Window type")
+            raise TypeError("Can only add objects of type toga.Window")
         # Silently not add if duplicate
         if window not in self.elements:
             self.elements.add(window)
@@ -91,30 +86,45 @@ def add(self, window: Window) -> None:
 
     def discard(self, window: Window) -> None:
         if not isinstance(window, Window):
-            raise TypeError(
-                "Toga app.windows can only discard an object of a toga.Window type"
-            )
+            raise TypeError("Can only discard objects of type toga.Window")
         if window not in self.elements:
-            raise AttributeError(
-                "The window you are trying to remove is not associated with this app"
-            )
+            raise ValueError(f"{window!r} is not part of this app")
         self.elements.remove(window)
 
-    def __iadd__(self, window):
-        self.add(window)
+    ######################################################################
+    # 2023-10: Backwards compatibility
+    ######################################################################
+
+    def __iadd__(self, window: Window) -> None:
+        # The standard set type does not have a += operator.
+        warn(
+            "Windows are automatically associated with the app; += is not required",
+            DeprecationWarning,
+            stacklevel=2,
+        )
         return self
 
-    def __isub__(self, other):
-        self.discard(other)
+    def __isub__(self, other: Window) -> None:
+        # The standard set type does have a -= operator, but it takes sets rather than
+        # individual items.
+        warn(
+            "Windows are automatically removed from the app; -= is not required",
+            DeprecationWarning,
+            stacklevel=2,
+        )
         return self
 
-    def __iter__(self):
+    ######################################################################
+    # End backwards compatibility
+    ######################################################################
+
+    def __iter__(self) -> Iterator:
         return iter(self.elements)
 
-    def __contains__(self, value):
+    def __contains__(self, value: Window) -> bool:
         return value in self.elements
 
-    def __len__(self):
+    def __len__(self) -> int:
         return len(self.elements)
 
 
@@ -129,6 +139,8 @@ def __init__(
         size: tuple[int, int] = (640, 480),
         resizable: bool = True,
         minimizable: bool = True,
+        resizeable=None,  # DEPRECATED
+        closeable=None,  # DEPRECATED
     ):
         """Create a new main window.
 
@@ -141,6 +153,8 @@ def __init__(
             pixels <css-units>`.
         :param resizable: Can the window be resized by the user?
         :param minimizable: Can the window be minimized by the user?
+        :param resizeable: **DEPRECATED** - Use ``resizable``.
+        :param closeable: **DEPRECATED** - Use ``closable``.
         """
         super().__init__(
             id=id,
@@ -150,6 +164,9 @@ def __init__(
             resizable=resizable,
             closable=True,
             minimizable=minimizable,
+            # Deprecated arguments
+            resizeable=resizeable,
+            closeable=closeable,
         )
 
     @property
@@ -164,8 +181,7 @@ def on_close(self) -> None:
         Always returns ``None``. Main windows should use :meth:`toga.App.on_exit`,
         rather than ``on_close``.
 
-        :raises ValueError: if an attempt is made to set the ``on_close`` handler for a
-            MainWindow.
+        :raises ValueError: if an attempt is made to set the ``on_close`` handler.
         """
         return None
 
@@ -173,10 +189,54 @@ def on_close(self) -> None:
     def on_close(self, handler: Any):
         if handler:
             raise ValueError(
-                "Cannot set on_close handler for the main window. Use the app on_exit handler instead"
+                "Cannot set on_close handler for the main window. "
+                "Use the app on_exit handler instead."
             )
 
 
+class DocumentMainWindow(Window):
+    def __init__(
+        self,
+        doc: Document,
+        id: str | None = None,
+        title: str | None = None,
+        position: tuple[int, int] = (100, 100),
+        size: tuple[int, int] = (640, 480),
+        resizable: bool = True,
+        minimizable: bool = True,
+    ):
+        """Create a new document Main Window.
+
+        This installs a default on_close handler that honors platform-specific document
+        closing behavior. If you want to control whether a document is allowed to close
+        (e.g., due to having unsaved change), override
+        :meth:`toga.Document.can_close()`, rather than implementing an on_close handler.
+
+        :param document: The document being managed by this window
+        :param id: The ID of the window.
+        :param title: Title for the window. Defaults to the formal name of the app.
+        :param position: Position of the window, as a tuple of ``(x, y)`` coordinates.
+        :param size: Size of the window, as a tuple of ``(width, height)``, in pixels.
+        :param resizable: Can the window be manually resized by the user?
+        :param minimizable: Can the window be minimized by the user?
+        """
+        self.doc = doc
+        super().__init__(
+            id=id,
+            title=title,
+            position=position,
+            size=size,
+            resizable=resizable,
+            closable=True,
+            minimizable=minimizable,
+            on_close=doc.handle_close,
+        )
+
+    @property
+    def _default_title(self) -> str:
+        return self.doc.path.name
+
+
 class App:
     app = None
 
@@ -185,189 +245,155 @@ def __init__(
         formal_name: str | None = None,
         app_id: str | None = None,
         app_name: str | None = None,
-        id: str | None = None,
+        *,
         icon: Icon | str | None = None,
         author: str | None = None,
         version: str | None = None,
         home_page: str | None = None,
         description: str | None = None,
         startup: AppStartupMethod | None = None,
-        windows: Iterable[Window] = (),
         on_exit: OnExitHandler | None = None,
-        factory: None = None,  # DEPRECATED !
+        id=None,  # DEPRECATED
+        windows=None,  # DEPRECATED
     ):
-        """An App is the top level of any GUI program.
-
-        The App is the manager of all the other aspects of execution. An app will
-        usually have a main window; this window will hold the widgets with which the
-        user will interact.
-
-        When you create an App you need to provide a name, an id for uniqueness (by
-        convention, the identifier is a reversed domain name) and an optional startup
-        function which should run once the App has initialized. The startup function
-        constructs the initial user interface. If a startup function is not provided as
-        an argument, you must subclass the App class and define a ``startup()`` method.
-
-        If the name and app_id are *not* provided, the application will attempt to find
-        application metadata. This process will determine the module in which the App
-        class is defined, and look for a ``.dist-info`` file matching that name.
+        """Create a new App instance.
 
-        Once the app is created you should invoke the ``main_loop()`` method, which will
-        start the event loop of your App.
+        Once the app has been created, you should invoke the
+        :meth:`~toga.App.main_loop()` method, which will start the event loop of your
+        App.
 
-        :param formal_name: The formal name of the application. Will be derived from
-            packaging metadata if not provided.
+        :param formal_name: The human-readable name of the app. If not provided,
+            the metadata key ``Formal-Name`` must be present.
         :param app_id: The unique application identifier. This will usually be a
-            reversed domain name, e.g. ``org.beeware.myapp``. Will be derived from
-            packaging metadata if not provided.
-        :param app_name: The name of the Python module containing the app. Will be
-            derived from the module defining the instance of the App class if not
-            provided.
-        :param id: The DOM identifier for the app (optional)
-        :param icon: Identifier for the application's icon.
+            reversed domain name, e.g. ``org.beeware.myapp``. If not provided, the
+            metadata key ``App-ID`` must be present.
+        :param app_name: The name of the distribution used to load metadata with
+            :any:`importlib.metadata`. If not provided, the following will be tried in
+            order:
+
+            #. If the ``__main__`` module is contained in a package, that package's name
+               will be used.
+            #. If the ``app_id`` argument was provided, its last segment will be used.
+               For example, an ``app_id`` of ``com.example.my-app`` would yield a
+               distribution name of ``my-app``.
+            #. As a last resort, the name ``toga``.
+        :param icon: The :any:`Icon` for the app. If not provided, Toga will attempt to
+            load an icon from ``resources/app_name``, where ``app_name`` is defined
+            above. If no resource matching this name can be found, a warning will be
+            printed, and the app will fall back to a default icon.
         :param author: The person or organization to be credited as the author of the
-            application. Will be derived from application metadata if not provided.
-        :param version: The version number of the app. Will be derived from packaging
-            metadata if not provided.
-        :param home_page: A URL for a home page for the app. Used in auto-generated help
-            menu items. Will be derived from packaging metadata if not provided.
-        :param description: A brief (one line) description of the app. Will be derived
-            from packaging metadata if not provided.
-        :param startup: The callback method before starting the app, typically to add
-            the components. Must be a ``callable`` that expects a single argument of
-            :class:`~toga.App`.
-        :param windows: An iterable with objects of :class:`~toga.Window` that will be
-            the app's secondary windows.
+            app. If not provided, the metadata key ``Author`` will be used.
+        :param version: The version number of the app.  If not provided, the metadata
+            key ``Version`` will be used.
+        :param home_page: The URL of a web page for the app. Used in auto-generated help
+            menu items. If not provided, the metadata key ``Home-page`` will be used.
+        :param description: A brief (one line) description of the app. If not provided,
+            the metadata key ``Summary`` will be used.
+        :param startup: A callable to run before starting the app.
+        :param on_exit: The initial :any:`on_exit` handler.
+        :param id: **DEPRECATED** - This argument will be ignored. If you need a
+            machine-friendly identifier, use ``app_id``.
+        :param windows: **DEPRECATED** – Windows are now automatically added to the
+            current app. Passing this argument will cause an exception.
         """
-
         ######################################################################
-        # 2022-09: Backwards compatibility
+        # 2023-10: Backwards compatibility
         ######################################################################
-        # factory no longer used
-        if factory:
-            warnings.warn("The factory argument is no longer used.", DeprecationWarning)
+        if id is not None:
+            warn(
+                "App.id is deprecated and will be ignored. Use app_id instead",
+                DeprecationWarning,
+                stacklevel=2,
+            )
+
+        if windows is not None:
+            raise ValueError(
+                "The `windows` constructor argument of toga.App has been removed. "
+                "Windows are now automatically added to the current app."
+            )
         ######################################################################
-        # End backwards compatibility.
+        # End backwards compatibility
         ######################################################################
 
         # Initialize empty widgets registry
         self._widgets = WidgetRegistry()
 
-        # Keep an accessible copy of the app instance
+        # Keep an accessible copy of the app singleton instance
         App.app = self
 
-        # We need a module name to load app metadata. If an app_name has been
-        # provided, we can set the app name now, and derive the module name
-        # from there.
-        if app_name:
-            self._app_name = app_name
-        else:
-            # If the code is contained in appname.py, and you start the app
-            # using `python -m appname`, the main module package will report
-            # as ''. Set the initial app name as None.
+        # We need a distribution name to load app metadata.
+        if app_name is None:
+            # If the code is contained in appname.py, and you start the app using
+            # `python -m appname`, then __main__.__package__ will be an empty string.
             #
-            # If the code is contained in appname.py, and you start the app
-            # using `python appname.py`, the main module will report as None.
+            # If the code is contained in appname.py, and you start the app using
+            # `python appname.py`, then __main__.__package__ will be None.
             #
-            # If the code is contained in a folder, and you start the app
-            # using `python -m appname`, the main module will report as the
-            # name of the folder.
+            # If the code is contained in appname/__main__.py, and you start the app
+            # using `python -m appname`, then __main__.__package__ will be "appname".
             try:
                 main_module_pkg = sys.modules["__main__"].__package__
-                if main_module_pkg == "":
-                    self._app_name = None
-                else:
-                    self._app_name = main_module_pkg
+                if main_module_pkg:
+                    app_name = main_module_pkg
             except KeyError:
-                # We use the existence of a __main__ module as a proxy for
-                # being in test conditions. This isn't *great*, but the __main__
-                # module isn't meaningful during tests, and removing it allows
-                # us to avoid having explicit "if under test conditions" checks.
-                # If there's no __main__ module, we're in a test, and we can't
-                # imply an app name from that module name.
-                self._app_name = None
-
-            # Try deconstructing the app name from the app ID
-            if self._app_name is None and app_id:
-                self._app_name = app_id.split(".")[-1]
-
-        # Load the app metadata (if it is available)
-        # Apps packaged with Briefcase will have this metadata.
-        try:
-            self.metadata = importlib_metadata.metadata(self.module_name)
-        except importlib_metadata.PackageNotFoundError:
-            self.metadata = Message()
+                # If there's no __main__ module, we're probably in a test.
+                pass
+
+        # Try deconstructing the distribution name from the app ID
+        if (app_name is None) and app_id:
+            app_name = app_id.split(".")[-1]
 
-        # Now that we have metadata, we can fix the app name (in the case
-        # where the app name and the module name differ - e.g., an app name
-        # of ``hello-world`` will have a module name of ``hello_world``).
-        # We use the PEP566-compliant key ``Name```, rather than the internally
-        # consistent key ``App-Name```.
-        if self.metadata["Name"] is not None:
-            self._app_name = self.metadata["Name"]
-
-        # Whatever app name has been given, speculatively attempt to import
-        # the app module. Single-file apps won't have an app folder; apps with
-        # misleading or misconfigured app names haven't given us enough
-        # metadata to determine the app folder. In those cases, fall back to
-        # an app name that *will* exist (``toga```)
+        # If we still don't have a distribution name, fall back to ``toga`` as a
+        # last resort.
+        if app_name is None:
+            app_name = "toga"
+
+        # Try to load the app metadata with our best guess of the distribution name.
+        self._app_name = app_name
         try:
-            sys.modules[self.module_name]
-        except KeyError:
-            # Well that didn't work...
-            self._app_name = "toga"
+            self.metadata = importlib.metadata.metadata(app_name)
+        except importlib.metadata.PackageNotFoundError:
+            self.metadata = Message()
 
-        # If a name has been provided, use it; otherwise, look to
-        # the module metadata. However, a name *must* be provided.
+        # If a formal name has been provided, use it; otherwise, look to
+        # the metadata. However, a formal name *must* be provided.
         if formal_name:
             self._formal_name = formal_name
         else:
-            self._formal_name = self.metadata["Formal-Name"]
-
+            self._formal_name = self.metadata.get("Formal-Name")
         if self._formal_name is None:
             raise RuntimeError("Toga application must have a formal name")
 
         # If an app_id has been provided, use it; otherwise, look to
-        # the module metadata. However, an app_id *must* be provided
+        # the metadata. However, an app_id *must* be provided
         if app_id:
             self._app_id = app_id
         else:
             self._app_id = self.metadata.get("App-ID", None)
-
         if self._app_id is None:
-            raise RuntimeError("Toga application must have an App ID")
+            raise RuntimeError("Toga application must have an app ID")
 
-        # If an author has been provided, use it; otherwise, look to
-        # the module metadata.
+        # Other metadata may be passed to the constructor, or loaded with importlib.
         if author:
             self._author = author
         else:
             self._author = self.metadata.get("Author", None)
 
-        # If a version has been provided, use it; otherwise, look to
-        # the module metadata.
         if version:
             self._version = version
         else:
             self._version = self.metadata.get("Version", None)
 
-        # If a home_page has been provided, use it; otherwise, look to
-        # the module metadata.
         if home_page:
             self._home_page = home_page
         else:
             self._home_page = self.metadata.get("Home-page", None)
 
-        # If a description has been provided, use it; otherwise, look to
-        # the module metadata.
         if description:
             self._description = description
         else:
             self._description = self.metadata.get("Summary", None)
 
-        # Set the application DOM ID; create an ID if one hasn't been provided.
-        self._id = str(id if id else identifier(self))
-
         # Get a platform factory.
         self.factory = get_platform_factory()
 
@@ -375,106 +401,108 @@ class is defined, and look for a ``.dist-info`` file matching that name.
         self._paths = Paths()
 
         # If an icon (or icon name) has been explicitly provided, use it;
-        # otherwise, the icon will be based on the app name.
+        # otherwise, the icon will be based on the distribution name.
         if icon:
             self.icon = icon
         else:
-            self.icon = f"resources/{self.app_name}"
+            self.icon = f"resources/{app_name}"
+
+        self.on_exit = on_exit
 
-        self.commands = CommandSet()
+        # We need the command set to exist so that startup et al can add commands;
+        # but we don't have an impl yet, so we can't set the on_change handler
+        self._commands = CommandSet()
 
         self._startup_method = startup
 
         self._main_window = None
-        self.windows = WindowSet(self, windows)
+        self._windows = WindowSet(self)
 
         self._full_screen_windows = None
 
-        self._impl = self._create_impl()
-        self.on_exit = on_exit
+        self._create_impl()
+
+        # Now that we have an impl, set the on_change handler for commands
+        self.commands.on_change = self._impl.create_menus
 
     def _create_impl(self):
-        return self.factory.App(interface=self)
+        self.factory.App(interface=self)
 
     @property
     def paths(self) -> Paths:
-        """Paths for platform appropriate locations on the user's file system.
-
-        Some platforms do not allow arbitrary file access to any location on
-        disk; even when arbitrary file system access is allowed, there are
-        "preferred" locations for some types of content.
+        """Paths for platform-appropriate locations on the user's file system.
 
-        The :class:`~toga.paths.Paths` object has a set of sub-properties that
-        return :class:`pathlib.Path` instances of platform-appropriate paths on
-        the file system.
+        Some platforms do not allow access to any file system location other than these
+        paths. Even when arbitrary file access is allowed, there are preferred locations
+        for each type of content.
         """
         return self._paths
 
     @property
     def name(self) -> str:
-        """The formal name of the app."""
+        """**DEPRECATED** – Use :any:`formal_name`."""
+        warn(
+            "App.name is deprecated. Use formal_name instead",
+            DeprecationWarning,
+            stacklevel=2,
+        )
         return self._formal_name
 
     @property
     def formal_name(self) -> str:
-        """The formal name of the app."""
+        """The human-readable name of the app (read-only)."""
         return self._formal_name
 
     @property
     def app_name(self) -> str:
-        """The machine-readable, PEP508-compliant name of the app."""
+        """The name of the distribution used to load metadata with
+        :any:`importlib.metadata` (read-only)."""
         return self._app_name
 
-    @property
-    def module_name(self) -> str | None:
-        """The module name for the app."""
-        try:
-            return self._app_name.replace("-", "_")
-        except AttributeError:
-            # If the app was created from an interactive prompt,
-            # there won't be a module name.
-            return None
-
     @property
     def app_id(self) -> str:
-        """The identifier for the app.
-
-        This is a reversed domain name, often used for targeting resources,
-        etc.
+        """The unique application identifier (read-only). This will usually be a
+        reversed domain name, e.g. ``org.beeware.myapp``.
         """
         return self._app_id
 
     @property
-    def author(self) -> str:
-        """The author of the app. This may be an organization name."""
+    def author(self) -> str | None:
+        """The person or organization to be credited as the author of the app
+        (read-only)."""
         return self._author
 
     @property
-    def version(self) -> str:
-        """The version number of the app."""
+    def version(self) -> str | None:
+        """The version number of the app (read-only)."""
         return self._version
 
     @property
-    def home_page(self) -> str:
-        """The URL of a web page for the app."""
+    def home_page(self) -> str | None:
+        """The URL of a web page for the app (read-only). Used in auto-generated help
+        menu items."""
         return self._home_page
 
     @property
-    def description(self) -> str:
-        """A brief description of the app."""
+    def description(self) -> str | None:
+        """A brief (one line) description of the app (read-only)."""
         return self._description
 
     @property
     def id(self) -> str:
-        """The DOM identifier for the app.
-
-        This id can be used to target CSS directives.
-        """
-        return self._id
+        """**DEPRECATED** – Use :any:`app_id`."""
+        warn(
+            "App.id is deprecated. Use app_id instead", DeprecationWarning, stacklevel=2
+        )
+        return self._app_id
 
     @property
     def icon(self) -> Icon:
-        """The Icon for the app."""
+        """The Icon for the app.
+
+        When setting the icon, you can provide either an :any:`Icon` instance, or a
+        path that will be passed to the ``Icon`` constructor.
+        """
         return self._icon
 
     @icon.setter
@@ -485,7 +513,7 @@ def icon(self, icon_or_name: Icon | str) -> None:
             self._icon = Icon(icon_or_name)
 
     @property
-    def widgets(self) -> WidgetRegistry:
+    def widgets(self) -> Mapping[str, Widget]:
         """The widgets managed by the app, over all windows.
 
         Can be used to look up widgets by ID over the entire app (e.g.,
@@ -493,6 +521,31 @@ def widgets(self) -> WidgetRegistry:
         """
         return self._widgets
 
+    @property
+    def windows(self) -> Collection[Window]:
+        """The windows managed by the app. Windows are automatically added to the app
+        when they are created, and removed when they are closed."""
+        return self._windows
+
+    ######################################################################
+    # 2023-10: Backwards compatibility
+    ######################################################################
+
+    # Support WindowSet __iadd__ and __isub__
+    @windows.setter
+    def windows(self, windows):
+        if windows is not self._windows:
+            raise AttributeError("can't set attribute 'windows'")
+
+    ######################################################################
+    # End backwards compatibility
+    ######################################################################
+
+    @property
+    def commands(self) -> MutableSet[Command]:
+        """The commands available in the app."""
+        return self._commands
+
     @property
     def main_window(self) -> MainWindow:
         """The main window for the app."""
@@ -504,15 +557,15 @@ def main_window(self, window: MainWindow) -> None:
         self._impl.set_main_window(window)
 
     @property
-    def current_window(self):
-        """Return the currently active content window."""
+    def current_window(self) -> Window | None:
+        """Return the currently active window."""
         window = self._impl.get_current_window()
         if window is None:
-            return window
+            return None
         return window.interface
 
     @current_window.setter
-    def current_window(self, window):
+    def current_window(self, window: Window):
         """Set a window into current active focus."""
         self._impl.set_current_window(window)
 
@@ -532,9 +585,8 @@ def set_full_screen(self, *windows: Window) -> None:
             those windows will not be visible. If no windows are specified, the app will
             exit full screen mode.
         """
-        if not windows:
-            self.exit_full_screen()
-        else:
+        self.exit_full_screen()
+        if windows:
             self._impl.enter_full_screen(windows)
             self._full_screen_windows = windows
 
@@ -545,7 +597,7 @@ def exit_full_screen(self) -> None:
             self._full_screen_windows = None
 
     def show_cursor(self) -> None:
-        """Show cursor."""
+        """Make the cursor visible."""
         self._impl.show_cursor()
 
     def hide_cursor(self) -> None:
@@ -553,7 +605,12 @@ def hide_cursor(self) -> None:
         self._impl.hide_cursor()
 
     def startup(self) -> None:
-        """Create and show the main window for the application."""
+        """Create and show the main window for the application.
+
+        Subclasses can override this method to define customized startup behavior;
+        however, any override *must* ensure the :any:`main_window` has been assigned
+        before it returns.
+        """
         self.main_window = MainWindow(title=self.formal_name)
 
         if self._startup_method:
@@ -583,9 +640,9 @@ def about(self) -> None:
         self._impl.show_about_dialog()
 
     def visit_homepage(self) -> None:
-        """Open the application's homepage in the default browser.
+        """Open the application's :any:`home_page` in the default browser.
 
-        If the application metadata doesn't define a homepage, this is a no-op.
+        If the :any:`home_page` is ``None``, this is a no-op.
         """
         if self.home_page is not None:
             webbrowser.open(self.home_page)
@@ -595,9 +652,10 @@ def beep(self) -> None:
         self._impl.beep()
 
     def main_loop(self) -> None:
-        """Invoke the application to handle user input.
+        """Start the application.
 
-        This method typically only returns once the application is exiting.
+        On desktop platforms, this method will block until the application has exited.
+        On mobile and web platforms, it returns immediately.
         """
         # Modify signal handlers to make sure Ctrl-C is caught and handled.
         signal.signal(signal.SIGINT, signal.SIG_DFL)
@@ -605,27 +663,33 @@ def main_loop(self) -> None:
         self._impl.main_loop()
 
     def exit(self) -> None:
-        """Quit the application gracefully."""
-        self.on_exit(None)
+        """Exit the application gracefully.
+
+        This *does not* invoke the ``on_exit`` handler; the app will be immediately
+        and unconditionally closed.
+        """
+        self._impl.exit()
 
     @property
     def on_exit(self) -> OnExitHandler:
-        """The handler to invoke before the application exits."""
+        """The handler to invoke if the user attempts to exit the app."""
         return self._on_exit
 
     @on_exit.setter
     def on_exit(self, handler: OnExitHandler | None) -> None:
-        if handler is None:
-
-            def handler(app, *args, **kwargs):
-                app._impl.exit()
-
         def cleanup(app, should_exit):
-            if should_exit:
-                app._impl.exit()
+            if should_exit or handler is None:
+                app.exit()
 
         self._on_exit = wrapped_handler(self, handler, cleanup=cleanup)
 
+    @property
+    def loop(self) -> asyncio.AbstractEventLoop:
+        """The `event loop
+        <https://docs.python.org/3/library/asyncio-eventloop.html>`__ of the app's main
+        thread (read-only)."""
+        return self._impl.loop
+
     def add_background_task(self, handler: BackgroundTask) -> None:
         """Schedule a task to run in the background.
 
@@ -637,7 +701,7 @@ def add_background_task(self, handler: BackgroundTask) -> None:
 
         :param handler: A coroutine, generator or callable.
         """
-        self._impl.loop.call_soon_threadsafe(wrapped_handler(self, handler), None)
+        self.loop.call_soon_threadsafe(wrapped_handler(self, handler))
 
 
 class DocumentApp(App):
@@ -646,43 +710,35 @@ def __init__(
         formal_name: str | None = None,
         app_id: str | None = None,
         app_name: str | None = None,
-        id: str | None = None,
+        *,
         icon: str | None = None,
         author: str | None = None,
         version: str | None = None,
         home_page: str | None = None,
         description: str | None = None,
         startup: AppStartupMethod | None = None,
-        document_types: list[str] | None = None,
+        document_types: dict[str, type[Document]] = None,
         on_exit: OnExitHandler | None = None,
-        factory: None = None,  # DEPRECATED !
+        id=None,  # DEPRECATED
     ):
-        """Create a document-based Application.
+        """Create a document-based application.
 
         A document-based application is the same as a normal application, with the
-        exception that there is no main window. Instead, each document managed by
-        the app will have it's own window.
+        exception that there is no main window. Instead, each document managed by the
+        app will create and manage it's own window (or windows).
 
-        :param document_types: The file extensions that this application can manage.
+        :param document_types: Initial :any:`document_types` mapping.
         """
-        ######################################################################
-        # 2022-09: Backwards compatibility
-        ######################################################################
-        # factory no longer used
-        if factory:
-            warnings.warn("The factory argument is no longer used.", DeprecationWarning)
-        ######################################################################
-        # End backwards compatibility.
-        ######################################################################
+        if document_types is None:
+            raise ValueError("A document must manage at least one document type.")
 
-        self.document_types = document_types
+        self._document_types = document_types
         self._documents = []
 
         super().__init__(
             formal_name=formal_name,
             app_id=app_id,
             app_name=app_name,
-            id=id,
             icon=icon,
             author=author,
             version=version,
@@ -690,6 +746,7 @@ def __init__(
             description=description,
             startup=startup,
             on_exit=on_exit,
+            id=id,
         )
 
     def _create_impl(self):
@@ -700,6 +757,39 @@ def _verify_startup(self):
         pass
 
     @property
-    def documents(self) -> list[str]:
+    def document_types(self) -> dict[str, type[Document]]:
+        """The document types this app can manage.
+
+        A dictionary of file extensions, without leading dots, mapping to the
+        :class:`toga.Document` subclass that will be created when a document with that
+        extension is opened. The subclass must take exactly 2 arguments in its
+        constructor: ``path`` and ``app``.
+        """
+        return self._document_types
+
+    @property
+    def documents(self) -> list[Document]:
         """The list of documents associated with this app."""
         return self._documents
+
+    def startup(self) -> None:
+        """No-op; a DocumentApp has no windows until a document is opened.
+
+        Subclasses can override this method to define customized startup behavior.
+        """
+
+    def _open(self, path):
+        """Internal utility method; open a new document in this app, and shows the document.
+
+        :param path: The path to the document to be opened.
+        :raises ValueError: If the document is of a type that can't be opened. Backends can
+            suppress this exception if necessary to presere platform-native behavior.
+        """
+        try:
+            DocType = self.document_types[path.suffix[1:]]
+        except KeyError:
+            raise ValueError(f"Don't know how to open documents of type {path.suffix}")
+        else:
+            document = DocType(path, app=self)
+            self._documents.append(document)
+            document.show()
diff --git a/core/src/toga/command.py b/core/src/toga/command.py
index 4f66dabd83..8dd95ea554 100644
--- a/core/src/toga/command.py
+++ b/core/src/toga/command.py
@@ -1,97 +1,80 @@
-import warnings
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any, Protocol
 
 from toga.handlers import wrapped_handler
 from toga.icons import Icon
+from toga.keys import Key
 from toga.platform import get_platform_factory
 
-# BACKWARDS COMPATIBILITY: a token object that can be used to differentiate
-# between an explicitly provided ``None``, and an unspecified value falling
-# back to a default.
-NOT_PROVIDED = object()
+if TYPE_CHECKING:
+    from toga.app import App
 
 
 class Group:
-    """
-
-    Args:
-        text:
-        order:
-        parent:
-    """
-
     def __init__(
         self,
-        text=NOT_PROVIDED,  # BACKWARDS COMPATIBILITY: The default value
-        # can be removed when the handling for
-        # `label` is removed
-        order=None,
-        section=None,
-        parent=None,
-        label=None,  # DEPRECATED!
+        text: str,
+        *,
+        parent: Group | None = None,
+        section: int = 0,
+        order: int = 0,
     ):
-        ##################################################################
-        # 2022-07: Backwards compatibility
-        ##################################################################
-        # When deleting this block, also delete the NOT_PROVIDED
-        # placeholder, and replace its usage in default values.
-
-        # label replaced with text
-        if label is not None:
-            if text is not NOT_PROVIDED:
-                raise ValueError(
-                    "Cannot specify both `label` and `text`; "
-                    "`label` has been deprecated, use `text`"
-                )
-            else:
-                warnings.warn(
-                    "Group.label has been renamed Group.text", DeprecationWarning
-                )
-                text = label
-        elif text is NOT_PROVIDED:
-            # This would be raised by Python itself; however, we need to use a placeholder
-            # value as part of the migration from text->value.
-            raise TypeError(
-                "Group.__init__ missing 1 required positional argument: 'text'"
-            )
-
-        ##################################################################
-        # End backwards compatibility.
-        ##################################################################
-
+        """
+        An collection of commands to display together.
+
+        :param text: A label for the group.
+        :param parent: The parent of this group; use ``None`` to make a root group.
+        :param section: The section where the group should appear within its parent. A
+            section cannot be specified unless a parent is also specified.
+        :param order: The position where the group should appear within its section.
+            If multiple items have the same group, section and order, they will be
+            sorted alphabetically by their text.
+        """
         self.text = text
-        self.order = order if order else 0
-        if parent is None and section is not None:
+        self.order = order
+        if parent is None and section != 0:
             raise ValueError("Section cannot be set without parent group")
-        self.section = section if section else 0
+        self.section = section
 
-        # First initialization needed for later
+        # Prime the underlying value of _parent so that the setter has a current value
+        # to work with
         self._parent = None
         self.parent = parent
 
     @property
-    def parent(self):
+    def parent(self) -> Group | None:
+        """The parent of this group; returns ``None`` if the group is a root group."""
         return self._parent
 
     @parent.setter
-    def parent(self, parent):
+    def parent(self, parent: Group | None):
         if parent is None:
             self._parent = None
-            self._root = self
-            return
-        if parent == self or self.is_parent_of(parent):
-            error_message = (
-                "Cannot set {} to be a parent of {} "
-                "because it causes a cyclic parenting."
-            ).format(parent.text, self.text)
-            raise ValueError(error_message)
-        self._parent = parent
-        self._root = parent.root
+        elif parent == self:
+            raise ValueError("A group cannot be it's own parent")
+        elif self.is_parent_of(parent):
+            raise ValueError(
+                f"Cannot set parent; {self.text!r} is an ancestor of {parent.text!r}."
+            )
+        else:
+            self._parent = parent
 
     @property
-    def root(self):
-        return self._root
+    def root(self) -> Group:
+        """The root group for this group.
+
+        This will be ``self`` if the group *is* a root group."""
+        if self.parent is None:
+            return self
+        return self.parent.root
+
+    def is_parent_of(self, child: Group | None) -> bool:
+        """Is this group a parent of the provided group, directly or indirectly?
 
-    def is_parent_of(self, child):
+        :param child: The potential child to check
+        :returns: True if this group is a parent of the provided child.
+        """
         if child is None:
             return False
         if child.parent is None:
@@ -100,68 +83,59 @@ def is_parent_of(self, child):
             return True
         return self.is_parent_of(child.parent)
 
-    def is_child_of(self, parent):
+    def is_child_of(self, parent: Group | None) -> bool:
+        """Is this group a child of the provided group, directly or indirectly?
+
+        :param parent: The potential parent to check
+        :returns: True if this group is a child of the provided parent.
+        """
+        if parent is None:
+            return False
         return parent.is_parent_of(self)
 
-    def __hash__(self):
+    def __hash__(self) -> int:
         return hash(self.key)
 
-    def __lt__(self, other):
+    def __lt__(self, other: Any) -> bool:
+        if not isinstance(other, (Group, Command)):
+            return False
         return self.key < other.key
 
-    def __gt__(self, other):
+    def __gt__(self, other: Any) -> bool:
+        if not isinstance(other, (Group, Command)):
+            return False
         return other < self
 
-    def __eq__(self, other):
-        if other is None:
+    def __eq__(self, other: Any) -> bool:
+        if not isinstance(other, (Group, Command)):
             return False
         return self.key == other.key
 
-    def __repr__(self):
-        parent_string = "None" if self.parent is None else self.parent.text
-        return "<Group text={} order={} parent={}>".format(
-            self.text, self.order, parent_string
+    def __repr__(self) -> str:
+        parent_string = (
+            f" parent={self.parent} section={self.section}"
+            if self.parent is not None
+            else ""
         )
+        return f"<Group text={self.text!r} order={self.order}{parent_string}>"
 
     @property
-    def key(self):
+    def key(self) -> tuple[(int, int, str)]:
         """A unique tuple describing the path to this group."""
         self_tuple = (self.section, self.order, self.text)
         if self.parent is None:
             return tuple([self_tuple])
         return tuple([*self.parent.key, self_tuple])
 
-    @property
-    def path(self):
-        """A list containing the chain of groups that contain this group."""
-        if self.parent is None:
-            return [self]
-        return [*self.parent.path, self]
-
-    ######################################################################
-    # 2022-07: Backwards compatibility
-    ######################################################################
-    # label replaced with text
-    @property
-    def label(self):
-        """Group text.
-
-        **DEPRECATED: renamed as text**
-
-        Returns:
-            The button text as a ``str``
-        """
-        warnings.warn("Group.label has been renamed Group.text", DeprecationWarning)
-        return self.text
-
-    @label.setter
-    def label(self, label):
-        warnings.warn("Group.label has been renamed Group.text", DeprecationWarning)
-        self.text = label
-
-    ######################################################################
-    # End backwards compatibility.
-    ######################################################################
+    # Standard groups - docstrings can only be provided within the `class` statement,
+    # but the objects can't be instantiated here.
+    APP = None  #: Application-level commands
+    FILE = None  #: File commands
+    EDIT = None  #: Editing commands
+    VIEW = None  #: Content appearance commands
+    COMMANDS = None  #: Default group for user-provided commands
+    WINDOW = None  #: Window management commands
+    HELP = None  #: Help commands
 
 
 Group.APP = Group("*", order=0)
@@ -173,180 +147,132 @@ def label(self, label):
 Group.HELP = Group("Help", order=100)
 
 
-class Command:
-    """
-    Args:
-        action: a function to invoke when the command is activated.
-        text: caption for the command.
-        shortcut: (optional) a key combination that can be used to invoke the
-            command.
-        tooltip: (optional) a short description for what the command will do.
-        icon: (optional) a path to an icon resource to decorate the command.
-        group: (optional) a Group object describing a collection of similar
-            commands. If no group is specified, a default "Command" group will
-            be used.
-        section: (optional) an integer providing a sub-grouping. If no section
-            is specified, the command will be allocated to section 0 within the
-            group.
-        order: (optional) an integer indicating where a command falls within a
-            section. If a Command doesn't have an order, it will be sorted
-            alphabetically by text within its section.
-        enabled: whether to enable the command or not.
-    """
+class ActionHandler(Protocol):
+    def __call__(self, command: Command, **kwargs) -> bool:
+        """A handler that will be invoked when a Command is invoked.
+
+        :param command: The command that triggered the action.
+        :param kwargs: Ensures compatibility with additional arguments introduced in
+            future versions.
+        """
+        ...
+
 
+class Command:
     def __init__(
         self,
-        action,
-        text=NOT_PROVIDED,  # BACKWARDS COMPATIBILITY: The default value
-        # can be removed when the handling for
-        # `label` is removed
-        shortcut=None,
-        tooltip=None,
-        icon=None,
-        group=None,
-        section=None,
-        order=None,
-        enabled=True,
-        factory=None,  # DEPRECATED!
-        label=None,  # DEPRECATED!
+        action: ActionHandler | None,
+        text: str,
+        *,
+        shortcut: str | Key | None = None,
+        tooltip: str | None = None,
+        icon: str | Icon | None = None,
+        group: Group = Group.COMMANDS,
+        section: int = 0,
+        order: int = 0,
+        enabled: bool = True,
     ):
-        ######################################################################
-        # 2022-09: Backwards compatibility
-        ######################################################################
-        # factory no longer used
-        if factory:
-            warnings.warn("The factory argument is no longer used.", DeprecationWarning)
-        ######################################################################
-        # End backwards compatibility.
-        ######################################################################
-
-        ##################################################################
-        # 2022-07: Backwards compatibility
-        ##################################################################
-        # When deleting this block, also delete the NOT_PROVIDED
-        # placeholder, and replace its usage in default values.
-
-        # label replaced with text
-        if label is not None:
-            if text is not NOT_PROVIDED:
-                raise ValueError(
-                    "Cannot specify both `label` and `text`; "
-                    "`label` has been deprecated, use `text`"
-                )
-            else:
-                warnings.warn(
-                    "Command.label has been renamed Command.text", DeprecationWarning
-                )
-                text = label
-        elif text is NOT_PROVIDED:
-            # This would be raised by Python itself; however, we need to use a placeholder
-            # value as part of the migration from text->value.
-            raise TypeError(
-                "Command.__init__ missing 1 required positional argument: 'text'"
-            )
-
-        ##################################################################
-        # End backwards compatibility.
-        ##################################################################
+        """
+        Create a new Command.
+
+        Commands may not use all the arguments - for example, on some platforms, menus
+        will contain icons; on other platforms they won't.
+
+        :param action: A handler to invoke when the command is activated. If this is
+            ``None``, the command will be disabled.
+        :param text: A label for the command.
+        :param shortcut: A key combination that can be used to invoke the command.
+        :param tooltip: A short description of what the command will do.
+        :param icon: The icon, or icon resource, that can be used to decorate the
+            command if the platform requires.
+        :param group: The group to which this command belongs.
+        :param section: The section where the command should appear within its group.
+        :param order: The position where the command should appear within its section.
+            If multiple items have the same group, section and order, they will be
+            sorted alphabetically by their text.
+        :param enabled: Is the Command currently enabled?
+        """
         self.text = text
 
         self.shortcut = shortcut
         self.tooltip = tooltip
         self.icon = icon
 
-        self.group = group if group else Group.COMMANDS
-        self.section = section if section else 0
-        self.order = order if order else 0
+        self.group = group
+        self.section = section
+        self.order = order
 
-        orig_action = action
         self.action = wrapped_handler(self, action)
 
         self.factory = get_platform_factory()
         self._impl = self.factory.Command(interface=self)
 
-        self.enabled = enabled and orig_action is not None
+        self.enabled = enabled
 
     @property
-    def key(self):
-        """A unique tuple describing the path to this command."""
-        return tuple([*self.group.key, (self.section, self.order, self.text)])
+    def key(self) -> tuple[(int, int, str)]:
+        """A unique tuple describing the path to this command.
 
-    def bind(self, factory=None):
-        warnings.warn(
-            "Commands no longer need to be explicitly bound.", DeprecationWarning
-        )
-        return self._impl
+        Each element in the tuple describes the (section, order, text) for the
+        groups that must be navigated to invoke this action.
+        """
+        return tuple([*self.group.key, (self.section, self.order, self.text)])
 
     @property
-    def enabled(self):
+    def enabled(self) -> bool:
+        """Is the command currently enabled?"""
         return self._enabled
 
     @enabled.setter
-    def enabled(self, value):
-        self._enabled = value
-        if self._impl is not None:
-            self._impl.set_enabled(value)
+    def enabled(self, value: bool):
+        self._enabled = value and getattr(self.action, "_raw", True) is not None
+        self._impl.set_enabled(value)
 
     @property
-    def icon(self):
-        """The Icon for the app.
+    def icon(self) -> Icon | None:
+        """The Icon for the command.
 
-        :returns: A ``toga.Icon`` instance for the app's icon.
+        When setting the icon, you can provide either an :any:`Icon` instance, or a
+        path that will be passed to the ``Icon`` constructor.
         """
         return self._icon
 
     @icon.setter
-    def icon(self, icon_or_name):
+    def icon(self, icon_or_name: str | Icon):
         if isinstance(icon_or_name, Icon) or icon_or_name is None:
             self._icon = icon_or_name
         else:
             self._icon = Icon(icon_or_name)
 
-    def __lt__(self, other):
+    def __lt__(self, other: Any) -> bool:
+        if not isinstance(other, (Group, Command)):
+            return False
         return self.key < other.key
 
-    def __gt__(self, other):
+    def __gt__(self, other: Any) -> bool:
+        if not isinstance(other, (Group, Command)):
+            return False
         return other < self
 
-    def __repr__(self):
-        return "<Command text={} group={} section={} order={}>".format(
-            self.text,
-            self.group,
-            self.section,
-            self.order,
+    def __repr__(self) -> bool:
+        return (
+            f"<Command text={self.text!r} "
+            f"group={self.group} "
+            f"section={self.section} "
+            f"order={self.order}>"
         )
 
-    ######################################################################
-    # 2022-07: Backwards compatibility
-    ######################################################################
-    # label replaced with text
-    @property
-    def label(self):
-        """Command text.
 
-        **DEPRECATED: renamed as text**
+class Break:
+    def __init__(self, name: str):
+        """A representation of a separator between Command Groups, or between sections
+        in a Group.
 
-        Returns:
-            The command text as a ``str``
+        :param name: A name of the break type.
         """
-        warnings.warn("Command.label has been renamed Command.text", DeprecationWarning)
-        return self.text
-
-    @label.setter
-    def label(self, label):
-        warnings.warn("Command.label has been renamed Command.text", DeprecationWarning)
-        self.text = label
-
-    ######################################################################
-    # End backwards compatibility.
-    ######################################################################
-
-
-class Break:
-    def __init__(self, name):
         self.name = name
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return f"<{self.name} break>"
 
 
@@ -354,49 +280,64 @@ def __repr__(self):
 SECTION_BREAK = Break("Section")
 
 
-class CommandSet:
-    """
+class CommandSetChangeHandler(Protocol):
+    def __call__(self) -> None:
+        """A handler that will be invoked when a Command or Group is added to the CommandSet.
 
-    Args:
-        factory:
-        widget:
-        on_change:
+        .. note::
+            ``**kwargs`` ensures compatibility with additional arguments
+            introduced in future versions.
+
+        :return: Nothing
+        """
+        ...
 
-    Todo:
-        * Add missing Docstrings.
-    """
 
+class CommandSet:
     def __init__(
         self,
-        factory=None,  # DEPRECATED!
-        widget=None,
-        on_change=None,
+        on_change: CommandSetChangeHandler = None,
+        app: App | None = None,
     ):
-        ######################################################################
-        # 2022-09: Backwards compatibility
-        ######################################################################
-        # factory no longer used
-        if factory:
-            warnings.warn("The factory argument is no longer used.", DeprecationWarning)
-        ######################################################################
-        # End backwards compatibility.
-        ######################################################################
-
-        self.widget = widget
+        """
+        A collection of commands.
+
+        This is used as an internal representation of Menus, Toolbars, and any other
+        graphical manifestations of commands. You generally don't need to construct a
+        CommandSet of your own; you should use existing app or window level CommandSet
+        instances.
+
+        The collection can be iterated over to provide the display order of the commands
+        managed by the group.
+
+        :param on_change: A method that should be invoked when this command set changes.
+        :param app: The app this command set is associated with, if it is not the app's
+            own commandset.
+        """
+        self._app = app
         self._commands = set()
         self.on_change = on_change
 
-    def add(self, *commands):
-        if self.widget and self.widget.app is not None:
-            self.widget.app.commands.add(*commands)
+    def add(self, *commands: Command | Group):
+        if self.app and self.app is not None:
+            self.app.commands.add(*commands)
         self._commands.update(commands)
         if self.on_change:
             self.on_change()
 
-    def __len__(self):
+    def clear(self):
+        self._commands = set()
+        if self.on_change:
+            self.on_change()
+
+    @property
+    def app(self) -> App:
+        return self._app
+
+    def __len__(self) -> int:
         return len(self._commands)
 
-    def __iter__(self):
+    def __iter__(self) -> Command | Group | Break:
         prev_cmd = None
         for cmd in sorted(self._commands):
             if prev_cmd:
diff --git a/core/src/toga/documents.py b/core/src/toga/documents.py
index 4604314a32..a4a02dd7c7 100644
--- a/core/src/toga/documents.py
+++ b/core/src/toga/documents.py
@@ -1,16 +1,118 @@
-class Document:
-    def __init__(self, filename, document_type, app=None):
-        self.filename = filename
-        self.document_type = document_type
+from __future__ import annotations
 
+import asyncio
+import warnings
+from abc import ABC, abstractmethod
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from toga.app import App
+    from toga.window import Window
+
+
+class Document(ABC):
+    def __init__(
+        self,
+        path: str | Path,
+        document_type: str,
+        app: App = None,
+    ):
+        """Create a new Document.
+
+        :param path: The path where the document is stored.
+        :param document_type: A human-readable description of the document type.
+        :param app: The application the document is associated with.
+        """
+        self._path = Path(path)
+        self._document_type = document_type
         self._app = app
+        self._main_window = None
+
+        # Create the visual representation of the document
+        self.create()
 
         # Create a platform specific implementation of the Document
         self._impl = app.factory.Document(interface=self)
 
+    def can_close(self) -> bool:
+        """Is the main document window allowed to close?
+
+        The default implementation always returns ``True``; subclasses can override this
+        to prevent a window closing with unsaved changes, etc.
+
+        This default implementation is a function; however, subclasses can define it
+        as an asynchronous co-routine if necessary to allow for dialog confirmations.
+        """
+        return True
+
+    async def handle_close(self, window, **kwargs):
+        """An ``on-close`` handler for the main window of this document that implements
+        platform-specific document close behavior.
+
+        It interrogates the :meth:`~toga.Document.can_close()` method to determine if
+        the document is allowed to close.
+        """
+        if asyncio.iscoroutinefunction(self.can_close):
+            can_close = await self.can_close()
+        else:
+            can_close = self.can_close()
+
+        if can_close:
+            if self._impl.SINGLE_DOCUMENT_APP:
+                self.app.exit()
+                return False
+            else:
+                return True
+        else:
+            return False
+
     @property
-    def app(self):
+    def path(self) -> Path:
+        """The path where the document is stored (read-only)."""
+        return self._path
+
+    @property
+    def filename(self) -> Path:
+        """**DEPRECATED** - Use :attr:`path`."""
+        warnings.warn(
+            "Document.filename has been renamed Document.path.",
+            DeprecationWarning,
+        )
+        return self._path
+
+    @property
+    def document_type(self) -> Path:
+        """A human-readable description of the document type (read-only)."""
+        return self._document_type
+
+    @property
+    def app(self) -> App:
+        """The app that this document is associated with (read-only)."""
         return self._app
 
-    def read(self):
-        raise NotImplementedError("Document class must define read()")
+    @property
+    def main_window(self) -> Window:
+        """The main window for the document."""
+        return self._main_window
+
+    @main_window.setter
+    def main_window(self, window):
+        self._main_window = window
+
+    def show(self) -> None:
+        """Show the :any:`main_window` for this document."""
+        self.main_window.show()
+
+    @abstractmethod
+    def create(self) -> None:
+        """Create the window (or windows) for the document.
+
+        This method must, at a minimum, assign the :any:`main_window` property. It
+        may also create additional windows or UI elements if desired.
+        """
+
+    @abstractmethod
+    def read(self) -> None:
+        """Load a representation of the document into memory and populate the document
+        window."""
diff --git a/core/src/toga/handlers.py b/core/src/toga/handlers.py
index 5d22ed279b..8d345883c6 100644
--- a/core/src/toga/handlers.py
+++ b/core/src/toga/handlers.py
@@ -69,7 +69,7 @@ def wrapped_handler(interface, handler, cleanup=None):
         if isinstance(handler, NativeHandler):
             return handler.native
 
-        def _handler(widget, *args, **kwargs):
+        def _handler(*args, **kwargs):
             if asyncio.iscoroutinefunction(handler):
                 asyncio.ensure_future(
                     handler_with_cleanup(handler, cleanup, interface, *args, **kwargs)
@@ -98,7 +98,7 @@ def _handler(widget, *args, **kwargs):
 
     else:
         # A dummy no-op handler
-        def _handler(widget, *args, **kwargs):
+        def _handler(*args, **kwargs):
             try:
                 if cleanup:
                     cleanup(interface, None)
diff --git a/core/src/toga/images.py b/core/src/toga/images.py
index b072dd2124..a436a8103c 100644
--- a/core/src/toga/images.py
+++ b/core/src/toga/images.py
@@ -34,20 +34,23 @@ def __init__(
                 self.path = path
             else:
                 self.path = Path(path)
-            self.data = None
         else:
             self.path = None
-            self.data = data
 
         self.factory = get_platform_factory()
-        if self.data is not None:
-            self._impl = self.factory.Image(interface=self, data=self.data)
+        if data is not None:
+            self._impl = self.factory.Image(interface=self, data=data)
         else:
             self.path = toga.App.app.paths.app / self.path
             if not self.path.is_file():
                 raise FileNotFoundError(f"Image file {self.path} does not exist")
             self._impl = self.factory.Image(interface=self, path=self.path)
 
+    @property
+    def size(self) -> (int, int):
+        """The size of the image, as a tuple"""
+        return (self._impl.get_width(), self._impl.get_height())
+
     @property
     def width(self) -> int:
         """The width of the image, in pixels."""
@@ -58,6 +61,14 @@ def height(self) -> int:
         """The height of the image, in pixels."""
         return self._impl.get_height()
 
+    @property
+    def data(self) -> bytes:
+        """The raw data for the image, in PNG format.
+
+        :returns: The raw image data in PNG format.
+        """
+        return self._impl.get_data()
+
     def save(self, path: str | Path):
         """Save image to given path.
 
diff --git a/core/src/toga/keys.py b/core/src/toga/keys.py
index d6d02f6fd8..6e78728eb8 100644
--- a/core/src/toga/keys.py
+++ b/core/src/toga/keys.py
@@ -2,6 +2,9 @@
 
 
 class Key(Enum):
+    """An enumeration providing a symbolic representation for the characters on
+    a keyboard."""
+
     A = "a"
     B = "b"
     C = "c"
@@ -92,25 +95,25 @@ class Key(Enum):
     MOD_2 = "<mod 2>"  # OPT on macOS, ALT on Linux/Windows
     MOD_3 = "<mod 3>"  # CTRL on macOS, Flag on Windows, Tux on Linux
 
-    F1 = "<F1>"
-    F2 = "<F2>"
-    F3 = "<F3>"
-    F4 = "<F4>"
-    F5 = "<F5>"
-    F6 = "<F6>"
-    F7 = "<F7>"
-    F8 = "<F8>"
-    F9 = "<F9>"
-    F10 = "<F10>"
-    F11 = "<F11>"
-    F12 = "<F12>"
-    F13 = "<F13>"
-    F14 = "<F14>"
-    F15 = "<F15>"
-    F16 = "<F16>"
-    F17 = "<F17>"
-    F18 = "<F18>"
-    F19 = "<F19>"
+    F1 = "<f1>"
+    F2 = "<f2>"
+    F3 = "<f3>"
+    F4 = "<f4>"
+    F5 = "<f5>"
+    F6 = "<f6>"
+    F7 = "<f7>"
+    F8 = "<f8>"
+    F9 = "<f9>"
+    F10 = "<f10>"
+    F11 = "<f11>"
+    F12 = "<f12>"
+    F13 = "<f13>"
+    F14 = "<f14>"
+    F15 = "<f15>"
+    F16 = "<f16>"
+    F17 = "<f17>"
+    F18 = "<f18>"
+    F19 = "<f19>"
 
     EJECT = "<eject>"
 
@@ -144,7 +147,8 @@ class Key(Enum):
     NUMPAD_MULTIPLY = "numpad:*"
     NUMPAD_PLUS = "numpad:+"
 
-    def is_printable(self):
+    def is_printable(self) -> bool:
+        """Does pressing the key result in a printable character?"""
         return not (self.value.startswith("<") and self.value.endswith(">"))
 
     def __add__(self, other):
diff --git a/core/src/toga/widgets/box.py b/core/src/toga/widgets/box.py
index 3bc9485682..cc6a61b9ad 100644
--- a/core/src/toga/widgets/box.py
+++ b/core/src/toga/widgets/box.py
@@ -4,6 +4,9 @@
 
 
 class Box(Widget):
+    _MIN_WIDTH = 0
+    _MIN_HEIGHT = 0
+
     def __init__(
         self,
         id: str | None = None,
diff --git a/core/src/toga/widgets/canvas.py b/core/src/toga/widgets/canvas.py
index 6592862416..96caa3fec3 100644
--- a/core/src/toga/widgets/canvas.py
+++ b/core/src/toga/widgets/canvas.py
@@ -3,7 +3,7 @@
 import warnings
 from abc import ABC, abstractmethod
 from contextlib import contextmanager
-from math import pi
+from math import cos, pi, sin, tan
 from typing import Protocol
 
 from travertino.colors import Color
@@ -1181,6 +1181,9 @@ def __call__(self, widget: Canvas, width: int, height: int, **kwargs):
 
 
 class Canvas(Widget):
+    _MIN_WIDTH = 0
+    _MIN_HEIGHT = 0
+
     def __init__(
         self,
         id=None,
@@ -1628,3 +1631,78 @@ def stroke(
             DeprecationWarning,
         )
         return self.Stroke(color=color, line_width=line_width, line_dash=line_dash)
+
+
+def sweepangle(startangle, endangle, anticlockwise):
+    """Returns an arc length in the range [-2 * pi, 2 * pi], where positive numbers are
+    clockwise. Based on the "ellipse method steps" in the HTML spec."""
+
+    if anticlockwise:
+        if endangle - startangle <= -2 * pi:
+            return -2 * pi
+    else:
+        if endangle - startangle >= 2 * pi:
+            return 2 * pi
+
+    startangle %= 2 * pi
+    endangle %= 2 * pi
+    sweepangle = endangle - startangle
+    if anticlockwise:
+        if sweepangle > 0:
+            sweepangle -= 2 * pi
+    else:
+        if sweepangle < 0:
+            sweepangle += 2 * pi
+
+    return sweepangle
+
+
+# Based on https://stackoverflow.com/a/30279817
+def arc_to_bezier(sweepangle):
+    """Approximates an arc of a unit circle as a sequence of Bezier segments.
+
+    :param sweepangle: Length of the arc in radians, where positive numbers are
+        clockwise.
+    :returns: [(1, 0), (cp1x, cp1y), (cp2x, cp2y), (x, y), ...], where each group of 3
+        points has the same meaning as in the bezier_curve_to method, and there are
+        between 1 and 4 groups."""
+
+    matrices = [
+        [1, 0, 0, 1],  # 0 degrees
+        [0, -1, 1, 0],  # 90
+        [-1, 0, 0, -1],  # 180
+        [0, 1, -1, 0],  # 270
+    ]
+
+    if sweepangle < 0:  # Anticlockwise
+        sweepangle *= -1
+        for matrix in matrices:
+            matrix[2] *= -1
+            matrix[3] *= -1
+
+    result = [(1.0, 0.0)]
+    for matrix in matrices:
+        if sweepangle < 0:
+            break
+
+        phi = min(sweepangle, pi / 2)
+        k = 4 / 3 * tan(phi / 4)
+        result += [
+            transform(x, y, matrix)
+            for x, y in [
+                (1, k),
+                (cos(phi) + k * sin(phi), sin(phi) - k * cos(phi)),
+                (cos(phi), sin(phi)),
+            ]
+        ]
+
+        sweepangle -= pi / 2
+
+    return result
+
+
+def transform(x, y, matrix):
+    return (
+        x * matrix[0] + y * matrix[1],
+        x * matrix[2] + y * matrix[3],
+    )
diff --git a/core/src/toga/widgets/selection.py b/core/src/toga/widgets/selection.py
index 2ffabc74c6..a6feae80c9 100644
--- a/core/src/toga/widgets/selection.py
+++ b/core/src/toga/widgets/selection.py
@@ -109,7 +109,7 @@ def items(self, items):
 
         # Restore the original change handler and trigger it.
         self._on_change = orig_on_change
-        self.on_change(None)
+        self.on_change()
 
         self.refresh()
 
diff --git a/core/src/toga/widgets/slider.py b/core/src/toga/widgets/slider.py
index 8dc9e331ae..28d129af8d 100644
--- a/core/src/toga/widgets/slider.py
+++ b/core/src/toga/widgets/slider.py
@@ -98,7 +98,7 @@ def _programmatic_change(self):
 
         self._on_change = on_change
         if self.value != old_value:
-            on_change(None)
+            on_change()
 
     @property
     def value(self) -> float:
@@ -404,7 +404,7 @@ def set_tick_count(self, tick_count):
     def on_change(self):
         span = self.max - self.min
         self.value = self.min + (self.get_int_value() / self.get_int_max() * span)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     @abstractmethod
     def get_int_value(self):
diff --git a/core/src/toga/window.py b/core/src/toga/window.py
index f223ee31f5..227bbb7bb4 100644
--- a/core/src/toga/window.py
+++ b/core/src/toga/window.py
@@ -2,11 +2,13 @@
 
 import warnings
 from builtins import id as identifier
+from collections.abc import Mapping, MutableSet
 from pathlib import Path
 from typing import TYPE_CHECKING, Any, Literal, Protocol, TypeVar, overload
 
-from toga.command import CommandSet
+from toga.command import Command, CommandSet
 from toga.handlers import AsyncResult, wrapped_handler
+from toga.images import Image
 from toga.platform import get_platform_factory
 from toga.widgets.base import WidgetRegistry
 
@@ -110,7 +112,7 @@ def __init__(
         # Needs to be a late import to avoid circular dependencies.
         from toga import App
 
-        self.widgets = WidgetRegistry()
+        self._widgets = WidgetRegistry()
 
         self._id = str(id if id else identifier(self))
         self._impl = None
@@ -130,10 +132,15 @@ def __init__(
             size=size,
         )
 
+        # Add the window to the app
         self._app = None
-        App.app.windows += self
+        if App.app is None:
+            raise RuntimeError("Cannot create a Window before creating an App")
+        App.app.windows.add(self)
+
+        # Create a toolbar that is linked to the app
+        self._toolbar = CommandSet(on_change=self._impl.create_toolbar, app=self._app)
 
-        self._toolbar = CommandSet(widget=self, on_change=self._impl.create_toolbar)
         self.on_close = on_close
 
     @property
@@ -194,7 +201,7 @@ def minimizable(self) -> bool:
         return self._minimizable
 
     @property
-    def toolbar(self) -> CommandSet:
+    def toolbar(self) -> MutableSet[Command]:
         """Toolbar for the window."""
         return self._toolbar
 
@@ -225,6 +232,14 @@ def content(self, widget: Widget) -> None:
         # Update the geometry of the widget
         widget.refresh()
 
+    @property
+    def widgets(self) -> Mapping[str, Widget]:
+        """The widgets contained in the window.
+
+        Can be used to look up widgets by ID (e.g., ``window.widgets["my_id"]``).
+        """
+        return self._widgets
+
     @property
     def size(self) -> tuple[int, int]:
         """Size of the window, as a tuple of ``(width, height)``, in
@@ -310,10 +325,16 @@ def close(self) -> None:
         undefined, except for :attr:`closed` which can be used to check if the window
         was closed.
         """
-        self.app.windows -= self
+        self.app.windows.discard(self)
         self._impl.close()
         self._closed = True
 
+    def as_image(self) -> Image:
+        """Render the current contents of the window as an image.
+
+        :returns: A :class:`toga.Image` containing the window content."""
+        return Image(data=self._impl.get_image_data())
+
     ############################################################
     # Dialogs
     ############################################################
diff --git a/android/tests/__init__.py b/core/tests/app/__init__.py
similarity index 100%
rename from android/tests/__init__.py
rename to core/tests/app/__init__.py
diff --git a/core/tests/app/test_app.py b/core/tests/app/test_app.py
new file mode 100644
index 0000000000..deac2063f5
--- /dev/null
+++ b/core/tests/app/test_app.py
@@ -0,0 +1,623 @@
+import asyncio
+import importlib.metadata
+import sys
+import webbrowser
+from pathlib import Path
+from unittest.mock import Mock
+
+import pytest
+
+import toga
+from toga_dummy.utils import (
+    assert_action_not_performed,
+    assert_action_performed,
+    assert_action_performed_with,
+)
+
+EXPLICIT_FULL_APP_KWARGS = dict(
+    formal_name="Explicit App",
+    app_id="org.beeware.explicit-app",
+    app_name="override-app",
+)
+EXPLICIT_MIN_APP_KWARGS = dict(
+    formal_name="Explicit App",
+    app_id="org.beeware.explicit-app",
+)
+APP_METADATA = {
+    "Formal-Name": "Test App",
+    "App-ID": "org.beeware.test-app",
+    "Name": "test-app",
+}
+
+
+@pytest.mark.parametrize(
+    (
+        "kwargs, metadata, main_module, expected_formal_name, expected_app_id, "
+        "expected_app_name"
+    ),
+    [
+        ###########################################################################
+        # Invoking as python my_app.py, or as an interactive prompt
+        # This causes a main package of None
+        ###########################################################################
+        # Explicit app properties, no metadata
+        (
+            EXPLICIT_FULL_APP_KWARGS,
+            None,
+            Mock(__package__=None),
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "override-app",
+        ),
+        # Explicit app properties, but implied distribution name from app_id, no
+        # metadata
+        (
+            EXPLICIT_MIN_APP_KWARGS,
+            None,
+            Mock(__package__=None),
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "explicit-app",
+        ),
+        # No app properties, with metadata
+        (
+            dict(),
+            APP_METADATA,
+            Mock(__package__=None),
+            "Test App",
+            "org.beeware.test-app",
+            "toga",
+        ),
+        # Explicit app properties, with metadata. Explicit values take precedence.
+        (
+            EXPLICIT_FULL_APP_KWARGS,
+            APP_METADATA,
+            Mock(__package__=None),
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "override-app",
+        ),
+        ###########################################################################
+        # Invoking as python -m my_app, where code is in my_app.py
+        # This causes a main module of ""
+        ###########################################################################
+        # Explicit app properties, no metadata
+        (
+            EXPLICIT_FULL_APP_KWARGS,
+            None,
+            Mock(__package__=""),
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "override-app",
+        ),
+        # Explicit app properties, but implied distribution name from app_id, no metadata
+        (
+            EXPLICIT_MIN_APP_KWARGS,
+            None,
+            Mock(__package__=""),
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "explicit-app",
+        ),
+        # No app properties, with metadata
+        (
+            dict(),
+            APP_METADATA,
+            Mock(__package__=""),
+            "Test App",
+            "org.beeware.test-app",
+            "toga",
+        ),
+        # Explicit app properties, with metadata. Explicit values take precedence.
+        (
+            EXPLICIT_FULL_APP_KWARGS,
+            APP_METADATA,
+            Mock(__package__=""),
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "override-app",
+        ),
+        ###########################################################################
+        # Invoking as python -m my_app, where my_app is a folder with a __main__
+        # This causes a main module of "my_app"
+        ###########################################################################
+        # Explicit app properties, no metadata
+        (
+            EXPLICIT_FULL_APP_KWARGS,
+            None,
+            Mock(__package__="my_app"),
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "override-app",
+        ),
+        # Explicit app properties, but implied distribution name from __package__, no
+        # metadata
+        (
+            EXPLICIT_MIN_APP_KWARGS,
+            None,
+            Mock(__package__="my_app"),
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "my_app",
+        ),
+        # No app properties, with metadata
+        (
+            dict(),
+            APP_METADATA,
+            Mock(__package__="my_app"),
+            "Test App",
+            "org.beeware.test-app",
+            "my_app",
+        ),
+        # Explicit app properties, with metadata. Explicit values take precedence.
+        (
+            EXPLICIT_FULL_APP_KWARGS,
+            APP_METADATA,
+            Mock(__package__="my_app"),
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "override-app",
+        ),
+        ###########################################################################
+        # Invoking in a test harness, where there's no __main__
+        ###########################################################################
+        # Explicit app properties, no metadata
+        (
+            EXPLICIT_FULL_APP_KWARGS,
+            None,
+            None,
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "override-app",
+        ),
+        # Explicit app properties, but implied distribution name from app_id, no metadata
+        (
+            EXPLICIT_MIN_APP_KWARGS,
+            None,
+            None,
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "explicit-app",
+        ),
+        # No app properties, with metadata
+        (
+            dict(),
+            APP_METADATA,
+            None,
+            "Test App",
+            "org.beeware.test-app",
+            "toga",
+        ),
+        # Explicit app properties, with metadata. Explicit values take precedence.
+        (
+            EXPLICIT_FULL_APP_KWARGS,
+            APP_METADATA,
+            None,
+            "Explicit App",
+            "org.beeware.explicit-app",
+            "override-app",
+        ),
+    ],
+)
+def test_create(
+    monkeypatch,
+    kwargs,
+    metadata,
+    main_module,
+    expected_formal_name,
+    expected_app_id,
+    expected_app_name,
+):
+    """A simple app can be created"""
+    # Monkeypatch the metadata retrieval function
+    if metadata:
+        metadata_mock = Mock(return_value=metadata)
+    else:
+        metadata_mock = Mock(
+            side_effect=importlib.metadata.PackageNotFoundError(expected_app_name)
+        )
+    monkeypatch.setattr(importlib.metadata, "metadata", metadata_mock)
+
+    # Monkeypatch the main module
+    if main_module is None:
+        try:
+            monkeypatch.delitem(sys.modules, "__main__")
+        except KeyError:
+            pass
+    else:
+        monkeypatch.setitem(sys.modules, "__main__", main_module)
+
+    app = toga.App(**kwargs)
+
+    assert app.formal_name == expected_formal_name
+    assert app.app_id == expected_app_id
+    assert app.app_name == expected_app_name
+    assert app.on_exit._raw is None
+
+    metadata_mock.assert_called_once_with(expected_app_name)
+
+
+@pytest.mark.parametrize(
+    "kwargs, exc_type, message",
+    [
+        (dict(), RuntimeError, "Toga application must have a formal name"),
+        (
+            dict(formal_name="Something"),
+            RuntimeError,
+            "Toga application must have an app ID",
+        ),
+        (
+            dict(windows=()),
+            ValueError,
+            "The `windows` constructor argument of toga.App has been removed",
+        ),
+    ],
+)
+def test_bad_app_creation(kwargs, exc_type, message):
+    """Errors are raised"""
+    with pytest.raises(exc_type, match=message):
+        toga.App(**kwargs)
+
+
+def test_app_metadata(monkeypatch):
+    """An app can load metadata from the .dist-info file"""
+    monkeypatch.setattr(
+        importlib.metadata,
+        "metadata",
+        Mock(
+            return_value={
+                "Formal-Name": "Metadata Name",
+                "Name": "metadata",
+                "App-ID": "org.beeware.metadata",
+                "Author": "Jane Developer",
+                "Version": "1.2.3",
+                "Home-page": "https://example.com/test-app",
+                "Summary": "A test app",
+            }
+        ),
+    )
+
+    # We can't use the app fixture here, because we need the metadata to be loaded as
+    # part of app construction.
+    app = toga.App(
+        formal_name="Test App",
+        app_id="org.example.test-app",
+    )
+
+    assert app.author == "Jane Developer"
+    assert app.version == "1.2.3"
+    assert app.home_page == "https://example.com/test-app"
+    assert app.description == "A test app"
+
+
+def test_explicit_app_metadata(monkeypatch):
+    """App metadata can be provided explicitly, overriding module-level metadata"""
+    monkeypatch.setattr(
+        importlib.metadata,
+        "metadata",
+        Mock(
+            return_value={
+                "Formal-Name": "Metadata Name",
+                "Name": "metadata",
+                "App-ID": "org.beeware.metadata",
+                "Author": "Alice Metadata",
+                "Version": "2.3.4",
+                "Home-page": "https://example.com/metadata",
+                "Summary": "Metadata description of app",
+            }
+        ),
+    )
+
+    on_exit_handler = Mock()
+
+    app = toga.App(
+        formal_name="Test App",
+        app_id="org.example.test-app",
+        author="Jane Developer",
+        version="1.2.3",
+        home_page="https://example.com/test-app",
+        description="A test app",
+        on_exit=on_exit_handler,
+    )
+
+    assert app.author == "Jane Developer"
+    assert app.version == "1.2.3"
+    assert app.home_page == "https://example.com/test-app"
+    assert app.description == "A test app"
+
+    assert app.on_exit._raw == on_exit_handler
+
+
+@pytest.mark.parametrize("construct", [True, False])
+def test_icon_construction(construct):
+    """The app icon can be set during construction"""
+    if construct:
+        icon = toga.Icon("path/to/icon")
+    else:
+        icon = "path/to/icon"
+
+    app = toga.App(
+        formal_name="Test App",
+        app_id="org.example.test",
+        icon=icon,
+    )
+    assert isinstance(app.icon, toga.Icon)
+    assert app.icon.path == Path("path/to/icon")
+
+
+@pytest.mark.parametrize("construct", [True, False])
+def test_icon(app, construct):
+    """The app icon can be changed"""
+    if construct:
+        icon = toga.Icon("path/to/icon")
+    else:
+        icon = "path/to/icon"
+
+    # Default icon matches distribution name
+    assert isinstance(app.icon, toga.Icon)
+    assert app.icon.path == Path("resources/test-app")
+
+    # Change icon
+    app.icon = icon
+    assert isinstance(app.icon, toga.Icon)
+    assert app.icon.path == Path("path/to/icon")
+
+
+def test_current_window(app):
+    """The current window can be set and changed."""
+    other_window = toga.Window()
+
+    # There are two windows - the main window, plus "other"
+    assert len(app.windows) == 2
+    assert_action_performed_with(app, "set_main_window", window=app.main_window)
+
+    # The initial current window is the main window
+    assert app.current_window == app.main_window
+
+    # Change the current window
+    app.current_window = other_window
+    assert app.current_window == other_window
+    assert_action_performed_with(app, "set_current_window", window=other_window)
+
+
+def test_no_current_window(app):
+    """If there's no current window, current_window reflects this"""
+    # If all the windows are deleted, and there's no main window (e.g., if it's a document app)
+    # there might be no current window.
+    app._main_window = None
+
+    # The current window evaluates as None
+    assert app.current_window is None
+
+
+def test_full_screen():
+    """The app can be put into full screen mode."""
+    window1 = toga.Window()
+    window2 = toga.Window()
+    app = toga.App(formal_name="Test App", app_id="org.example.test")
+
+    assert not app.is_full_screen
+
+    # If we're not full screen, exiting full screen is a no-op
+    app.exit_full_screen()
+    assert_action_not_performed(app, "exit_full_screen")
+
+    # Enter full screen with 2 windows
+    app.set_full_screen(window2, app.main_window)
+    assert app.is_full_screen
+    assert_action_performed_with(
+        app, "enter_full_screen", windows=(window2, app.main_window)
+    )
+
+    # Change the screens that are full screen
+    app.set_full_screen(app.main_window, window1)
+    assert app.is_full_screen
+    assert_action_performed_with(
+        app, "enter_full_screen", windows=(app.main_window, window1)
+    )
+
+    # Exit full screen mode
+    app.exit_full_screen()
+    assert not app.is_full_screen
+    assert_action_performed_with(
+        app, "exit_full_screen", windows=(app.main_window, window1)
+    )
+
+
+def test_set_empty_full_screen_window_list():
+    """Setting the full screen window list to [] is an explicit exit"""
+    app = toga.App(formal_name="Test App", app_id="org.example.test")
+    window1 = toga.Window()
+    window2 = toga.Window()
+
+    assert not app.is_full_screen
+
+    # Change the screens that are full screen
+    app.set_full_screen(window1, window2)
+    assert app.is_full_screen
+    assert_action_performed_with(app, "enter_full_screen", windows=(window1, window2))
+
+    # Exit full screen mode by setting no windows full screen
+    app.set_full_screen()
+    assert not app.is_full_screen
+    assert_action_performed_with(app, "exit_full_screen", windows=(window1, window2))
+
+
+def test_show_hide_cursor(app):
+    """The app cursor can be shown and hidden"""
+    app.hide_cursor()
+    assert_action_performed(app, "hide_cursor")
+
+    app.show_cursor()
+    assert_action_performed(app, "show_cursor")
+
+
+def test_startup_method():
+    """If an app provides a startup method, it will be invoked during startup"""
+    startup = Mock()
+    app = toga.App(
+        formal_name="Test App",
+        app_id="org.example.test",
+        startup=startup,
+    )
+
+    startup.assert_called_once_with(app)
+
+
+def test_startup_subclass():
+    """App can be subclassed"""
+
+    class SubclassedApp(toga.App):
+        def startup(self):
+            self.main_window = toga.MainWindow()
+
+    app = SubclassedApp(formal_name="Test App", app_id="org.example.test")
+
+    # The main window will exist, and will have the app's formal name.
+    assert app.main_window.title == "Test App"
+
+
+def test_startup_subclass_no_main_window():
+    """If a subclassed app doesn't define a main window, an error is raised"""
+
+    class SubclassedApp(toga.App):
+        def startup(self):
+            pass
+
+    with pytest.raises(ValueError, match=r"Application does not have a main window."):
+        SubclassedApp(formal_name="Test App", app_id="org.example.test")
+
+
+def test_about(app):
+    """The about dialog for the app can be shown"""
+    app.about()
+    assert_action_performed(app, "show_about_dialog")
+
+
+def test_visit_homepage(monkeypatch):
+    """The app's homepage can be opened"""
+    app = toga.App(
+        formal_name="Test App",
+        app_id="org.example.test",
+        home_page="https://example.com/test-app",
+    )
+    open_webbrowser = Mock()
+    monkeypatch.setattr(webbrowser, "open", open_webbrowser)
+
+    # The app has no homepage by default, so visit is a no-op
+    app.visit_homepage()
+
+    open_webbrowser.assert_called_once_with("https://example.com/test-app")
+
+
+def test_no_homepage(monkeypatch, app):
+    """If the app doesn't have a home page, visit_homepage is a no-op"""
+    open_webbrowser = Mock()
+    monkeypatch.setattr(webbrowser, "open", open_webbrowser)
+
+    # The app has no homepage by default, so visit is a no-op
+    app.visit_homepage()
+
+    open_webbrowser.assert_not_called()
+
+
+def test_beep(app):
+    """The machine can go Bing!"""
+    app.beep()
+    assert_action_performed(app, "beep")
+
+
+def test_exit_direct(app):
+    """An app can be exited directly"""
+    on_exit_handler = Mock(return_value=True)
+    app.on_exit = on_exit_handler
+
+    # Exit the app directly
+    app.exit()
+
+    # App has been exited, but the exit handler has *not* been invoked.
+    assert_action_performed(app, "exit")
+    on_exit_handler.assert_not_called()
+
+
+def test_exit_no_handler(app):
+    """A app without a exit handler can be exited"""
+    # Exit the app
+    app._impl.simulate_exit()
+
+    # Window has been exitd, and is no longer in the app's list of windows.
+    assert_action_performed(app, "exit")
+
+
+def test_exit_sucessful_handler(app):
+    """An app with a successful exit handler can be exited"""
+    on_exit_handler = Mock(return_value=True)
+    app.on_exit = on_exit_handler
+
+    # Close the app
+    app._impl.simulate_exit()
+
+    # App has been exited
+    assert_action_performed(app, "exit")
+    on_exit_handler.assert_called_once_with(app)
+
+
+def test_exit_rejected_handler(app):
+    """An app can have a exit handler that rejects the exit"""
+    on_exit_handler = Mock(return_value=False)
+    app.on_exit = on_exit_handler
+
+    # Close the window
+    app._impl.simulate_exit()
+
+    # App has been *not* exited
+    assert_action_not_performed(app, "exit")
+    on_exit_handler.assert_called_once_with(app)
+
+
+def test_loop(app, event_loop):
+    """The main thread's event loop can be accessed"""
+    assert isinstance(app.loop, asyncio.AbstractEventLoop)
+    assert app.loop is event_loop
+
+
+def test_background_task(app):
+    """A background task can be queued"""
+    canary = Mock()
+
+    async def background(app, **kwargs):
+        canary()
+
+    app.add_background_task(background)
+
+    # Create an async task that we can use to start the event loop for a short time.
+    async def waiter():
+        await asyncio.sleep(0.1)
+
+    app.loop.run_until_complete(waiter())
+
+    # Once the loop has executed, the background task should have executed as well.
+    canary.assert_called_once()
+
+
+def test_deprecated_id():
+    """The deprecated `id` constructor argument is ignored, and the property of the same
+    name is redirected to `app_id`
+    """
+    id_warning = r"App.id is deprecated.* Use app_id instead"
+    with pytest.warns(DeprecationWarning, match=id_warning):
+        app = toga.App("Test App", "org.example.test", id="test_app_id")
+
+    assert app.app_id == "org.example.test"
+    with pytest.warns(DeprecationWarning, match=id_warning):
+        assert app.id == "org.example.test"
+
+
+def test_deprecated_name():
+    """The deprecated `name` property is redirected to `formal_name`"""
+    name_warning = r"App.name is deprecated. Use formal_name instead"
+    app = toga.App("Test App", "org.example.test")
+
+    assert app.formal_name == "Test App"
+    with pytest.warns(DeprecationWarning, match=name_warning):
+        assert app.name == "Test App"
diff --git a/core/tests/app/test_documentapp.py b/core/tests/app/test_documentapp.py
new file mode 100644
index 0000000000..f4c53af086
--- /dev/null
+++ b/core/tests/app/test_documentapp.py
@@ -0,0 +1,158 @@
+import asyncio
+import sys
+from pathlib import Path
+from unittest.mock import Mock
+
+import pytest
+
+import toga
+from toga.platform import get_platform_factory
+from toga_dummy.documents import Document as DummyDocument
+from toga_dummy.utils import assert_action_performed
+
+
+class ExampleDocument(toga.Document):
+    def __init__(self, path, app):
+        super().__init__(path=path, document_type="Example Document", app=app)
+
+    def create(self):
+        self.main_window = toga.DocumentMainWindow(self)
+
+    def read(self):
+        self.content = self.path
+
+
+def test_create_no_cmdline(monkeypatch):
+    """A document app can be created with no command line."""
+    monkeypatch.setattr(sys, "argv", ["app-exe"])
+
+    app = toga.DocumentApp(
+        "Test App",
+        "org.beeware.document-app",
+        document_types={"foobar": ExampleDocument},
+    )
+    app.main_loop()
+
+    assert app._impl.interface == app
+    assert_action_performed(app, "create DocumentApp")
+
+    assert app.document_types == {"foobar": ExampleDocument}
+    assert app.documents == []
+
+
+def test_create_with_cmdline(monkeypatch):
+    """If a document is specified at the command line, it is opened."""
+    monkeypatch.setattr(sys, "argv", ["app-exe", "/path/to/filename.foobar"])
+
+    app = toga.DocumentApp(
+        "Test App",
+        "org.beeware.document-app",
+        document_types={"foobar": ExampleDocument},
+    )
+    app.main_loop()
+
+    assert app._impl.interface == app
+    assert_action_performed(app, "create DocumentApp")
+
+    assert app.document_types == {"foobar": ExampleDocument}
+    assert len(app.documents) == 1
+    assert isinstance(app.documents[0], ExampleDocument)
+
+    # Document content has been read
+    assert app.documents[0].content == Path("/path/to/filename.foobar")
+
+    # Document window has been created and shown
+    assert_action_performed(app.documents[0].main_window, "create Window")
+    assert_action_performed(app.documents[0].main_window, "show")
+
+
+def test_create_with_unknown_document_type(monkeypatch):
+    """If the document specified at the command line is an unknown type, an exception is raised"""
+    monkeypatch.setattr(sys, "argv", ["app-exe", "/path/to/filename.unknown"])
+
+    with pytest.raises(
+        ValueError,
+        match=r"Don't know how to open documents of type .unknown",
+    ):
+        toga.DocumentApp(
+            "Test App",
+            "org.beeware.document-app",
+            document_types={"foobar": ExampleDocument},
+        )
+
+
+def test_create_no_document_type():
+    """A document app must manage at least one document type."""
+    with pytest.raises(
+        ValueError,
+        match=r"A document must manage at least one document type.",
+    ):
+        toga.DocumentApp("Test App", "org.beeware.document-app")
+
+
+def test_close_single_document_app():
+    """An app in single document mode closes the app when the window is closed"""
+    # Monkeypatch the dummy impl to use single document mode
+    DummyDocument.SINGLE_DOCUMENT_APP = True
+
+    # Mock the app, but preserve the factory
+    app = Mock()
+    app.factory = get_platform_factory()
+
+    doc = ExampleDocument(path=Path("/path/to/doc.txt"), app=app)
+
+    # Window technically was prevented from closing, but the app has been exited.
+    # This must be run as a co-routine.
+    async def _do_close():
+        return await doc.handle_close(Mock())
+
+    assert not asyncio.get_event_loop().run_until_complete(_do_close())
+    app.exit.assert_called_once_with()
+
+
+def test_close_multiple_document_app():
+    """An app in multiple document mode doesn't close when the window is closed"""
+    # Monkeypatch the dummy impl to use single document mode
+    DummyDocument.SINGLE_DOCUMENT_APP = False
+
+    # Mock the app, but preserve the factory
+    app = Mock()
+    app.factory = get_platform_factory()
+
+    doc = ExampleDocument(path=Path("/path/to/doc.txt"), app=app)
+
+    # Window has closed, but app has not exited.
+    # This must be run as a co-routine.
+    async def _do_close():
+        return await doc.handle_close(Mock())
+
+    assert asyncio.get_event_loop().run_until_complete(_do_close())
+    app.exit.assert_not_called()
+
+
+@pytest.mark.parametrize("is_single_doc_app", [True, False])
+def test_no_close(monkeypatch, is_single_doc_app):
+    """A document can prevent itself from being closed."""
+    # Monkeypatch the dummy impl to set the app mode
+    DummyDocument.SINGLE_DOCUMENT_APP = is_single_doc_app
+
+    # Monkeypatch the Example document to prevent closing.
+    # Define this as a co-routine to simulate an implementation that called a dialog.
+    async def can_close(self):
+        return False
+
+    ExampleDocument.can_close = can_close
+
+    # Mock the app, but preserve the factory
+    app = Mock()
+    app.factory = get_platform_factory()
+
+    doc = ExampleDocument(path=Path("/path/to/doc.txt"), app=app)
+
+    # Window was prevented from closing.
+    # This must be run as a co-routine.
+    async def _do_close():
+        await doc.handle_close(Mock())
+
+    assert not asyncio.get_event_loop().run_until_complete(_do_close())
+    app.exit.assert_not_called()
diff --git a/core/tests/app/test_mainwindow.py b/core/tests/app/test_mainwindow.py
new file mode 100644
index 0000000000..69749e9014
--- /dev/null
+++ b/core/tests/app/test_mainwindow.py
@@ -0,0 +1,41 @@
+from unittest.mock import Mock
+
+import pytest
+
+import toga
+from toga_dummy.utils import assert_action_performed
+
+
+def test_create(app):
+    "A MainWindow can be created with minimal arguments"
+    window = toga.MainWindow()
+
+    assert window.app == app
+    assert window.content is None
+
+    assert window._impl.interface == window
+    assert_action_performed(window, "create Window")
+
+    # We can't know what the ID is, but it must be a string.
+    assert isinstance(window.id, str)
+    # Window title is the app title.
+    assert window.title == "Test App"
+    assert window.position == (100, 100)
+    assert window.size == (640, 480)
+    assert window.resizable
+    assert window.closable
+    assert window.minimizable
+    assert len(window.toolbar) == 0
+    # No on-close handler
+    assert window.on_close is None
+
+
+def test_no_close():
+    "An on_close handler cannot be set on MainWindow"
+    window = toga.MainWindow()
+
+    with pytest.raises(
+        ValueError,
+        match=r"Cannot set on_close handler for the main window. Use the app on_exit handler instead.",
+    ):
+        window.on_close = Mock()
diff --git a/core/tests/app/test_windowset.py b/core/tests/app/test_windowset.py
new file mode 100644
index 0000000000..fe0e771cd6
--- /dev/null
+++ b/core/tests/app/test_windowset.py
@@ -0,0 +1,89 @@
+import pytest
+
+import toga
+from toga.app import WindowSet
+
+
+@pytest.fixture
+def window1(app):
+    return toga.Window(title="Window 1")
+
+
+@pytest.fixture
+def window2(app):
+    return toga.Window(title="Window 2")
+
+
+def test_create(app):
+    """An empty windowset can be created."""
+    windowset = WindowSet(app)
+
+    assert windowset.app == app
+    assert len(windowset) == 0
+
+
+def test_add_discard(app, window1, window2):
+    """An item can be added to a windowset"""
+    # The windowset has 3 windows - the main window, plus 2 extras
+    assert len(app.windows) == 3
+
+    # Check the iterator works
+    assert set(iter(app.windows)) == {app.main_window, window1, window2}
+
+    with pytest.raises(
+        TypeError,
+        match=r"Can only add objects of type toga.Window",
+    ):
+        app.windows.add(object())
+
+    # Explicitly re-add a window that is already in the windowset
+    app.windows.add(window2)
+    assert len(app.windows) == 3
+    assert window2 in app.windows
+    assert window2.app == app
+
+    # Explicitly discard a window that is in the windowset
+    app.windows.discard(window2)
+    assert window2 not in app.windows
+
+    # Duplicate discard - it's no longer a member
+    with pytest.raises(
+        ValueError,
+        match=r"<toga.window.Window object at .*> is not part of this app",
+    ):
+        app.windows.discard(window2)
+
+    with pytest.raises(
+        TypeError,
+        match=r"Can only discard objects of type toga.Window",
+    ):
+        app.windows.discard(object())
+
+
+def test_iadd_isub(app, window1, window2):
+    """The deprecated += and -= operators are no-ops"""
+    # The windowset has 3 windows - the main window, plus 2 extras
+    assert window2 in app.windows
+    assert len(app.windows) == 3
+
+    with pytest.warns(
+        DeprecationWarning,
+        match=r"Windows are automatically associated with the app; \+= is not required",
+    ):
+        app.windows += window2
+
+    assert window2 in app.windows
+    assert len(app.windows) == 3
+
+    with pytest.warns(
+        DeprecationWarning,
+        match=r"Windows are automatically removed from the app; -= is not required",
+    ):
+        app.windows -= window2
+
+    # -= is a no-op.
+    assert window2 in app.windows
+    assert len(app.windows) == 3
+
+    with pytest.raises(AttributeError, match=r"can't set attribute 'windows'"):
+        app.windows = None
diff --git a/core/tests/command/conftest.py b/core/tests/command/conftest.py
new file mode 100644
index 0000000000..de127dd3b3
--- /dev/null
+++ b/core/tests/command/conftest.py
@@ -0,0 +1,28 @@
+import pytest
+
+import toga
+
+
+@pytest.fixture
+def parent_group_1():
+    return toga.Group("P", order=1)
+
+
+@pytest.fixture
+def child_group_1(parent_group_1):
+    return toga.Group("C", order=2, parent=parent_group_1)
+
+
+@pytest.fixture
+def child_group_2(parent_group_1):
+    return toga.Group("B", order=4, parent=parent_group_1)
+
+
+@pytest.fixture
+def parent_group_2():
+    return toga.Group("O", order=2)
+
+
+@pytest.fixture
+def child_group_3(parent_group_2):
+    return toga.Group("A", order=2, parent=parent_group_2)
diff --git a/core/tests/command/constants.py b/core/tests/command/constants.py
deleted file mode 100644
index e4cf81958b..0000000000
--- a/core/tests/command/constants.py
+++ /dev/null
@@ -1,38 +0,0 @@
-import toga
-
-PARENT_GROUP1 = toga.Group("P", 1)
-CHILD_GROUP1 = toga.Group("C", order=2, parent=PARENT_GROUP1)
-CHILD_GROUP2 = toga.Group("B", order=4, parent=PARENT_GROUP1)
-PARENT_GROUP2 = toga.Group("O", 2)
-CHILD_GROUP3 = toga.Group("A", 2, parent=PARENT_GROUP2)
-
-A = toga.Command(None, "A", group=PARENT_GROUP2, order=1)
-S = toga.Command(None, "S", group=PARENT_GROUP1, order=5)
-T = toga.Command(None, "T", group=CHILD_GROUP2, order=2)
-U = toga.Command(None, "U", group=CHILD_GROUP2, order=1)
-V = toga.Command(None, "V", group=PARENT_GROUP1, order=3)
-B = toga.Command(None, "B", group=CHILD_GROUP1, section=2, order=1)
-W = toga.Command(None, "W", group=CHILD_GROUP1, order=4)
-X = toga.Command(None, "X", group=CHILD_GROUP1, order=2)
-Y = toga.Command(None, "Y", group=CHILD_GROUP1, order=1)
-Z = toga.Command(None, "Z", group=PARENT_GROUP1, order=1)
-
-COMMANDS_IN_ORDER = [Z, Y, X, W, B, V, U, T, S, A]
-COMMANDS_IN_SET = [
-    Z,
-    toga.GROUP_BREAK,
-    Y,
-    X,
-    W,
-    toga.SECTION_BREAK,
-    B,
-    toga.GROUP_BREAK,
-    V,
-    toga.GROUP_BREAK,
-    U,
-    T,
-    toga.GROUP_BREAK,
-    S,
-    toga.GROUP_BREAK,
-    A,
-]
diff --git a/core/tests/command/test_command.py b/core/tests/command/test_command.py
index 0b43d2e30b..5eb032a977 100644
--- a/core/tests/command/test_command.py
+++ b/core/tests/command/test_command.py
@@ -1,147 +1,193 @@
 from pathlib import Path
+from unittest.mock import Mock
 
-from tests.command.constants import COMMANDS_IN_ORDER, PARENT_GROUP1
-from tests.utils import order_test
+import pytest
 
 import toga
-from toga_dummy.utils import TestCase
-
-
-class TestCommand(TestCase):
-    def setUp(self):
-        super().setUp()
-        # We need to define a test app to instantiate paths.
-        self.app = toga.App(
-            formal_name="Test App",
-            app_id="org.beeware.test-app",
-        )
-
-    def test_command_init_defaults(self):
-        cmd = toga.Command(lambda x: print("Hello World"), "test")
-        self.assertEqual(cmd.text, "test")
-        self.assertEqual(cmd.shortcut, None)
-        self.assertEqual(cmd.tooltip, None)
-        self.assertEqual(cmd.icon, None)
-        self.assertEqual(cmd.group, toga.Group.COMMANDS)
-        self.assertEqual(cmd.section, 0)
-        self.assertEqual(cmd.order, 0)
-        self.assertTrue(cmd._enabled)
-
-    def test_command_init_kargs(self):
-        grp = toga.Group("Test group", order=10)
-        cmd = toga.Command(
-            lambda x: print("Hello World"),
-            text="test",
-            tooltip="test command",
-            shortcut="t",
-            icon="icons/none.png",
-            group=grp,
-            section=1,
-            order=1,
-        )
-        self.assertEqual(cmd.text, "test")
-        self.assertEqual(cmd.shortcut, "t")
-        self.assertEqual(cmd.tooltip, "test command")
-        self.assertEqual(cmd.icon.path, Path("icons/none.png"))
-        self.assertEqual(cmd.group, grp)
-        self.assertEqual(cmd.section, 1)
-        self.assertEqual(cmd.order, 1)
-        self.assertTrue(cmd._enabled)
-        self.assertTrue(cmd.enabled)
-        cmd.enabled = False
-        self.assertFalse(cmd._enabled)
-        self.assertFalse(cmd.enabled)
-
-    def test_command_bind(self):
-        grp = toga.Group("Test group", order=10)
-        cmd = toga.Command(
-            lambda x: print("Hello World"),
-            text="test",
-            tooltip="test command",
-            shortcut="t",
-            icon="icons/none.png",
-            group=grp,
-            section=1,
-            order=1,
-        )
-
-        with self.assertWarns(DeprecationWarning):
-            return_val = cmd.bind()
-        self.assertEqual(return_val, cmd._impl)
-
-    def test_command_enabler(self):
-        grp = toga.Group("Test group", order=10)
-        cmd = toga.Command(
-            lambda x: print("Hello World"),
-            text="test",
-            tooltip="test command",
-            shortcut="t",
-            icon="icons/none.png",
-            group=grp,
-            section=1,
-            order=1,
-        )
-
-        cmd.enabled = False
-        self.assertActionPerformedWith(cmd, "set enabled", value=False)
-        cmd.enabled = True
-        self.assertActionPerformedWith(cmd, "set enabled", value=True)
-
-    def test_command_repr(self):
-        self.assertEqual(
-            repr(toga.Command(None, "A", group=PARENT_GROUP1, order=1, section=4)),
-            "<Command text=A group=<Group text=P order=1 parent=None> section=4 order=1>",
-        )
-
-    test_order_commands_by_text = order_test(
-        toga.Command(None, "A"), toga.Command(None, "B")
+from toga.command import Break
+from toga_dummy.utils import assert_action_performed_with
+
+
+def assert_order(*items):
+    for i in range(0, len(items) - 1):
+        for j in range(i + 1, len(items)):
+            assert items[i] < items[j]
+            assert items[j] > items[i]
+
+            # For good measure; check comparisons with other types
+            assert not items[i] < None
+            assert not items[i] < 42
+            assert not items[i] > None
+            assert not items[i] > 42
+
+
+def test_break():
+    """A break can be created"""
+
+    example_break = Break("Example")
+    assert repr(example_break) == "<Example break>"
+
+
+def test_create():
+    """A command can be created with defaults"""
+    cmd = toga.Command(None, "Test command")
+
+    assert cmd.text == "Test command"
+    assert cmd.shortcut is None
+    assert cmd.tooltip is None
+    assert cmd.group == toga.Group.COMMANDS
+    assert cmd.section == 0
+    assert cmd.order == 0
+    assert cmd.action._raw is None
+
+    assert (
+        repr(cmd)
+        == "<Command text='Test command' group=<Group text='Commands' order=30> section=0 order=0>"
+    )
+
+
+def test_create_explicit(app):
+    """A command can be created with explicit arguments"""
+    grp = toga.Group("Test group", order=10)
+
+    handler = Mock()
+    cmd = toga.Command(
+        handler,
+        text="Test command",
+        tooltip="This is a test command",
+        shortcut="t",
+        group=grp,
+        section=3,
+        order=4,
+    )
+
+    assert cmd.text == "Test command"
+    assert cmd.shortcut == "t"
+    assert cmd.tooltip == "This is a test command"
+    assert cmd.group == grp
+    assert cmd.section == 3
+    assert cmd.order == 4
+
+    assert cmd.action._raw == handler
+
+    assert (
+        repr(cmd)
+        == "<Command text='Test command' group=<Group text='Test group' order=10> section=3 order=4>"
+    )
+
+
+@pytest.mark.parametrize("construct", [True, False])
+def test_icon_construction(app, construct):
+    """The command icon can be set during construction"""
+    if construct:
+        icon = toga.Icon("path/to/icon")
+    else:
+        icon = "path/to/icon"
+
+    cmd = toga.Command(None, "Test command", icon=icon)
+    assert isinstance(cmd.icon, toga.Icon)
+    assert cmd.icon.path == Path("path/to/icon")
+
+
+@pytest.mark.parametrize("construct", [True, False])
+def test_icon(app, construct):
+    """The command icon can be changed"""
+    if construct:
+        icon = toga.Icon("path/to/icon")
+    else:
+        icon = "path/to/icon"
+
+    cmd = toga.Command(None, "Test command")
+
+    # No icon by default
+    assert cmd.icon is None
+
+    # Change icon
+    cmd.icon = icon
+
+    # Icon path matches
+    assert isinstance(cmd.icon, toga.Icon)
+    assert cmd.icon.path == Path("path/to/icon")
+
+
+@pytest.mark.parametrize(
+    "action, enabled, initial_state",
+    [
+        (Mock(), True, True),
+        (Mock(), False, False),
+        (None, True, False),
+        (None, False, False),
+    ],
+)
+def test_enable(action, enabled, initial_state):
+    cmd = toga.Command(action, text="Test command", enabled=enabled)
+
+    assert cmd.enabled is initial_state
+
+    # Set enabled; triggers an implementation response
+    cmd.enabled = True
+    assert_action_performed_with(cmd, "set enabled", value=True)
+
+    # Disable; triggers an implementation response
+    cmd.enabled = False
+    assert_action_performed_with(cmd, "set enabled", value=False)
+
+    # Disable again; triggers an implementation response
+    cmd.enabled = False
+    assert_action_performed_with(cmd, "set enabled", value=False)
+
+    # Set enabled; triggers an implementation response
+    cmd.enabled = True
+    assert_action_performed_with(cmd, "set enabled", value=True)
+
+
+def test_order_by_text():
+    """Commands are ordered by text when group, section and order match"""
+    assert_order(
+        toga.Command(None, "A"),
+        toga.Command(None, "B"),
     )
-    test_order_commands_by_number = order_test(
-        toga.Command(None, "B", order=1), toga.Command(None, "A", order=2)
+
+
+def test_order_by_number():
+    """Commands are ordered by number when group and section match"""
+    assert_order(
+        toga.Command(None, "B", order=1),
+        toga.Command(None, "A", order=2),
     )
-    test_order_commands_by_section = order_test(
-        toga.Command(None, "B", group=PARENT_GROUP1, section=1, order=2),
-        toga.Command(None, "A", group=PARENT_GROUP1, section=2, order=1),
+
+
+def test_order_by_section(parent_group_1):
+    """Section ordering takes priority over order and text"""
+    assert_order(
+        toga.Command(None, "B", group=parent_group_1, section=1, order=2),
+        toga.Command(None, "A", group=parent_group_1, section=2, order=1),
+    )
+
+
+def test_order_by_groups(parent_group_1, parent_group_2, child_group_1, child_group_2):
+    """Commands are ordered by group over"""
+
+    command_z = toga.Command(None, "Z", group=parent_group_1, order=1)
+    command_y = toga.Command(None, "Y", group=child_group_1, order=1)
+    command_x = toga.Command(None, "X", group=child_group_1, order=2)
+    command_w = toga.Command(None, "W", group=child_group_1, order=4)
+    command_b = toga.Command(None, "B", group=child_group_1, section=2, order=1)
+    command_v = toga.Command(None, "V", group=parent_group_1, order=3)
+    command_u = toga.Command(None, "U", group=child_group_2, order=1)
+    command_t = toga.Command(None, "T", group=child_group_2, order=2)
+    command_s = toga.Command(None, "S", group=parent_group_1, order=5)
+    command_a = toga.Command(None, "A", group=parent_group_2, order=1)
+
+    assert_order(
+        command_z,
+        command_y,
+        command_x,
+        command_w,
+        command_b,
+        command_v,
+        command_u,
+        command_t,
+        command_s,
+        command_a,
     )
-    test_order_commands_by_groups = order_test(*COMMANDS_IN_ORDER)
-
-    def test_missing_argument(self):
-        "If the no text is provided for the group, an error is raised"
-        # This test is only required as part of the backwards compatibility
-        # path renaming label->text; when that shim is removed, this teset
-        # validates default Python behavior
-        with self.assertRaises(TypeError):
-            toga.Command(lambda x: print("Hello World"))
-
-    ######################################################################
-    # 2022-07: Backwards compatibility
-    ######################################################################
-
-    def test_label_deprecated(self):
-        cmd = toga.Command(lambda x: print("Hello World"), label="test")
-        new_text = "New Text"
-        with self.assertWarns(DeprecationWarning):
-            cmd.label = new_text
-        with self.assertWarns(DeprecationWarning):
-            self.assertEqual(cmd.label, new_text)
-        self.assertEqual(cmd.text, new_text)
-
-    def test_init_with_deprecated(self):
-        # label is a deprecated argument
-        with self.assertWarns(DeprecationWarning):
-            toga.Command(
-                lambda x: print("Hello World"),
-                label="test",
-            )
-
-        # can't specify both label *and* text
-        with self.assertRaises(ValueError):
-            toga.Command(
-                lambda x: print("Hello World"),
-                label="test",
-                text="test",
-            )
-
-    ######################################################################
-    # End backwards compatibility.
-    ######################################################################
diff --git a/core/tests/command/test_commands_group.py b/core/tests/command/test_commands_group.py
deleted file mode 100644
index 2ab00fe2d8..0000000000
--- a/core/tests/command/test_commands_group.py
+++ /dev/null
@@ -1,183 +0,0 @@
-import unittest
-
-from tests.command.constants import PARENT_GROUP1, PARENT_GROUP2
-from tests.utils import order_test
-
-import toga
-
-
-class TestCommandsGroup(unittest.TestCase):
-    def test_group_init_no_order(self):
-        grp = toga.Group("text")
-        self.assertEqual(grp.text, "text")
-        self.assertEqual(grp.order, 0)
-
-    def test_group_init_with_order(self):
-        grp = toga.Group("text", 2)
-        self.assertEqual(grp.text, "text")
-        self.assertEqual(grp.order, 2)
-
-    def test_hashable(self):
-        grp1 = toga.Group("text 1")
-        grp2 = toga.Group("text 2")
-
-        # The hash is based on the full path, not just the text.
-        # This allows texts to be non-unique, as long as they're in
-        # different groups
-        grp1_child = toga.Group("text", parent=grp1)
-        grp2_child = toga.Group("text", parent=grp2)
-
-        # Insert the groups as keys in a dict. This is
-        # only possible if Group is hashable.
-        groups = {
-            grp1: "First",
-            grp2: "Second",
-            grp1_child: "Child of 1",
-            grp2_child: "Child of 2",
-        }
-
-        self.assertEqual(groups[grp1], "First")
-        self.assertEqual(groups[grp2], "Second")
-        self.assertEqual(groups[grp1_child], "Child of 1")
-        self.assertEqual(groups[grp2_child], "Child of 2")
-
-    def test_group_eq(self):
-        self.assertEqual(toga.Group("A"), toga.Group("A"))
-        self.assertEqual(toga.Group("A", 1), toga.Group("A", 1))
-        self.assertNotEqual(toga.Group("A"), toga.Group("B"))
-        self.assertNotEqual(toga.Group("A"), None)
-        self.assertNotEqual(toga.Group("A", 1), toga.Group("A", 2))
-        self.assertNotEqual(toga.Group("A", 1), toga.Group("B", 1))
-
-    def test_set_parent_in_constructor(self):
-        parent = toga.Group("parent")
-        child = toga.Group("child", parent=parent)
-        self.assert_parent_and_root(parent, None, parent)
-        self.assert_parent_and_root(child, parent, parent)
-
-    def test_set_parent_in_property(self):
-        parent = toga.Group("parent")
-        child = toga.Group("child")
-        child.parent = parent
-        self.assert_parent_and_root(parent, None, parent)
-        self.assert_parent_and_root(child, parent, parent)
-
-    def test_change_parent(self):
-        parent1 = toga.Group("parent1")
-        parent2 = toga.Group("parent2")
-        child = toga.Group("child", parent=parent1)
-        child.parent = parent2
-        self.assert_parent_and_root(parent1, None, parent1)
-        self.assert_parent_and_root(parent2, None, parent2)
-        self.assert_parent_and_root(child, parent2, parent2)
-
-    def test_is_parent_and_is_child_of(self):
-        top = toga.Group("C")
-        middle = toga.Group("B", parent=top)
-        bottom = toga.Group("A", parent=middle)
-        groups = [top, middle, bottom]
-        for i in range(0, 2):
-            for j in range(i + 1, 3):
-                self.assertTrue(groups[i].is_parent_of(groups[j]))
-                self.assertTrue(groups[j].is_child_of(groups[i]))
-
-    def test_is_parent_of_none(self):
-        group = toga.Group("A")
-        self.assertFalse(group.is_parent_of(None))
-
-    def test_root(self):
-        top = toga.Group("C")
-        middle = toga.Group("B", parent=top)
-        bottom = toga.Group("A", parent=middle)
-        self.assertEqual(top.root, top)
-        self.assertEqual(middle.root, top)
-        self.assertEqual(top.root, top)
-        self.assertEqual(bottom.root, top)
-
-    test_order_by_number = order_test(toga.Group("A", 1), toga.Group("A", 2))
-    test_order_ignore_text = order_test(toga.Group("B", 1), toga.Group("A", 2))
-    test_order_by_text = order_test(toga.Group("A"), toga.Group("B"))
-    test_order_by_groups = order_test(
-        PARENT_GROUP1,
-        toga.Group("C", parent=PARENT_GROUP1),
-        toga.Group("D", parent=PARENT_GROUP1),
-        toga.Group("A", parent=PARENT_GROUP1, section=2),
-        PARENT_GROUP2,
-        toga.Group("B", parent=PARENT_GROUP2),
-    )
-
-    def test_group_repr(self):
-        parent = toga.Group("P")
-        self.assertEqual(repr(toga.Group("A")), "<Group text=A order=0 parent=None>")
-        self.assertEqual(
-            repr(toga.Group("A", parent=parent)), "<Group text=A order=0 parent=P>"
-        )
-
-    def test_set_section_without_parent(self):
-        with self.assertRaises(ValueError):
-            toga.Group("A", section=2)
-
-    def test_set_parent_causes_cyclic_parenting(self):
-        parent = toga.Group("P")
-        child = toga.Group("C", parent=parent)
-        with self.assertRaises(ValueError):
-            parent.parent = child
-        self.assert_parent_and_root(parent, None, parent)
-        self.assert_parent_and_root(child, parent, parent)
-
-    def test_cannot_set_self_as_parent(self):
-        group = toga.Group("P")
-        with self.assertRaises(ValueError):
-            group.parent = group
-        self.assert_parent_and_root(group, None, group)
-
-    def test_cannot_set_child_to_be_a_parent_of_its_grandparent(self):
-        grandparent = toga.Group("G")
-        parent = toga.Group("P", parent=grandparent)
-        child = toga.Group("C", parent=parent)
-        with self.assertRaises(ValueError):
-            grandparent.parent = child
-        self.assert_parent_and_root(grandparent, None, grandparent)
-        self.assert_parent_and_root(parent, grandparent, grandparent)
-        self.assert_parent_and_root(child, parent, grandparent)
-
-    def assert_parent_and_root(self, group, parent, root):
-        self.assertEqual(group.parent, parent)
-        self.assertEqual(group.root, root)
-
-    def test_missing_argument(self):
-        "If the no text is provided for the group, an error is raised"
-        # This test is only required as part of the backwards compatibility
-        # path renaming label->text; when that shim is removed, this teset
-        # validates default Python behavior
-        with self.assertRaises(TypeError):
-            toga.Group()
-
-    ######################################################################
-    # 2022-07: Backwards compatibility
-    ######################################################################
-
-    def test_label_deprecated(self):
-        grp = toga.Group(label="text")
-        new_text = "New Text"
-        with self.assertWarns(DeprecationWarning):
-            grp.label = new_text
-        with self.assertWarns(DeprecationWarning):
-            self.assertEqual(grp.label, new_text)
-        self.assertEqual(grp.text, new_text)
-
-    def test_init_with_deprecated(self):
-        # label is a deprecated argument
-        with self.assertWarns(DeprecationWarning):
-            toga.Group(label="test")
-
-        # can't specify both label *and* text
-        with self.assertRaises(ValueError):
-            toga.Group(
-                label="test",
-                text="test",
-            )
-
-    ######################################################################
-    # End backwards compatibility.
-    ######################################################################
diff --git a/core/tests/command/test_commands_set.py b/core/tests/command/test_commands_set.py
deleted file mode 100644
index 75139541b5..0000000000
--- a/core/tests/command/test_commands_set.py
+++ /dev/null
@@ -1,51 +0,0 @@
-import random
-import unittest
-from unittest.mock import Mock
-
-from tests.command.constants import COMMANDS_IN_ORDER, COMMANDS_IN_SET
-
-import toga
-
-
-class TestCommandSet(unittest.TestCase):
-    changed = False
-
-    def _changed(self):
-        self.changed = True
-
-    def test_cmdset_init(self):
-        test_widget = toga.Widget()
-        cs = toga.CommandSet(test_widget)
-        self.assertEqual(cs._commands, set())
-        self.assertEqual(cs.on_change, None)
-
-    def test_cmdset_add(self):
-        self.changed = False
-        test_widget = toga.Widget()
-        cs = toga.CommandSet(widget=test_widget, on_change=self._changed)
-        grp = toga.Group("Test group", order=10)
-        cmd = toga.Command(
-            lambda x: print("Hello World"),
-            text="test",
-            tooltip="test command",
-            shortcut="t",
-            icon="icons/none.png",
-            group=grp,
-            section=1,
-            order=1,
-        )
-        cs.add(cmd)
-
-        self.assertTrue(self.changed)
-        self.assertIsNotNone(cmd._impl)
-
-    def test_cmdset_iter_in_order(self):
-        test_widget = toga.Widget()
-        test_widget._impl = Mock()
-        test_widget.app = Mock()
-        cs = toga.CommandSet(widget=test_widget)
-        commands = list(COMMANDS_IN_ORDER)
-        random.shuffle(commands)
-        cs.add(*commands)
-        test_widget.app.commands.add.assert_called_once_with(*commands)
-        self.assertEqual(list(cs), COMMANDS_IN_SET)
diff --git a/core/tests/command/test_commandset.py b/core/tests/command/test_commandset.py
new file mode 100644
index 0000000000..cfd2fa2970
--- /dev/null
+++ b/core/tests/command/test_commandset.py
@@ -0,0 +1,174 @@
+import random
+from unittest.mock import Mock
+
+import pytest
+
+import toga
+from toga.command import GROUP_BREAK, SECTION_BREAK, CommandSet
+
+
+def test_create():
+    """A CommandSet can be created with defaults"""
+    cs = CommandSet()
+
+    assert list(cs) == []
+    assert cs.on_change is None
+
+
+def test_create_with_values():
+    """A CommandSet can be created with values"""
+    change_handler = Mock()
+    cs = CommandSet(on_change=change_handler)
+
+    assert list(cs) == []
+    assert cs.on_change == change_handler
+
+
+@pytest.mark.parametrize("change_handler", [(None), (Mock())])
+def test_add_clear(app, change_handler):
+    """Commands can be added and removed from a commandset"""
+    # Put some commands into the app
+    cmd_a = toga.Command(None, text="App command a")
+    cmd_b = toga.Command(None, text="App command b", order=10)
+    app.commands.add(cmd_a, cmd_b)
+    assert list(app.commands) == [cmd_a, cmd_b]
+
+    # Create a standalone command set and add some commands
+    cs = CommandSet(on_change=change_handler)
+    cmd1a = toga.Command(None, text="Test command 1a", order=3)
+    cmd1b = toga.Command(None, text="Test command 1b", order=1)
+    cs.add(cmd1a, cmd1b)
+
+    # Change handler was called once.
+    if change_handler:
+        change_handler.assert_called_once()
+        change_handler.reset_mock()
+
+    # Command set has commands, and the order is the opposite to the insertion order.
+    assert list(cs) == [cmd1b, cmd1a]
+
+    # New Commands aren't known to the app
+    assert list(app.commands) == [cmd_a, cmd_b]
+
+    # Clear the command set
+    cs.clear()
+
+    # Change handler was called once.
+    if change_handler:
+        change_handler.assert_called_once()
+        change_handler.reset_mock()
+
+    # Command set no commands.
+    assert list(cs) == []
+
+    # App command set hasn't changed.
+    assert list(app.commands) == [cmd_a, cmd_b]
+
+
+@pytest.mark.parametrize("change_handler", [(None), (Mock())])
+def test_add_clear_with_app(app, change_handler):
+    """Commands can be added and removed from a commandset that is linked to an app"""
+    # Put some commands into the app
+    cmd_a = toga.Command(None, text="App command a")
+    cmd_b = toga.Command(None, text="App command b", order=10)
+    app.commands.add(cmd_a, cmd_b)
+    assert list(app.commands) == [cmd_a, cmd_b]
+
+    # Create a command set that is linked to the app and add some commands
+    cs = CommandSet(on_change=change_handler, app=app)
+    cmd1a = toga.Command(None, text="Test command 1a", order=3)
+    cmd1b = toga.Command(None, text="Test command 1b", order=1)
+    cs.add(cmd1a, cmd1b)
+
+    # Change handler was called once.
+    if change_handler:
+        change_handler.assert_called_once()
+        change_handler.reset_mock()
+
+    # Command set has commands, and the order is the opposite to the insertion order.
+    assert list(cs) == [cmd1b, cmd1a]
+
+    # New Commands are known to the app
+    assert list(app.commands) == [cmd_a, cmd1b, cmd1a, cmd_b]
+
+    # Add another command to the commandset
+    cmd2 = toga.Command(None, text="Test command 2", order=2)
+    cs.add(cmd2)
+
+    # Change handler was called once.
+    if change_handler:
+        change_handler.assert_called_once()
+        change_handler.reset_mock()
+
+    # Command set has commands, and the output is ordered.
+    assert list(cs) == [cmd1b, cmd2, cmd1a]
+
+    # App also knows about the command
+    assert list(app.commands) == [cmd_a, cmd1b, cmd2, cmd1a, cmd_b]
+
+    # Clear the command set
+    cs.clear()
+
+    # Change handler was called once.
+    if change_handler:
+        change_handler.assert_called_once()
+        change_handler.reset_mock()
+
+    # Command set no commands.
+    assert list(cs) == []
+
+    # App command set hasn't changed.
+    assert list(app.commands) == [cmd_a, cmd1b, cmd2, cmd1a, cmd_b]
+
+
+def test_ordering(parent_group_1, parent_group_2, child_group_1, child_group_2):
+    """Ordering of groups, breaks and commands is preserved"""
+
+    command_a = toga.Command(None, "A", group=parent_group_2, order=1)
+    command_b = toga.Command(None, "B", group=child_group_1, section=2, order=1)
+    command_s = toga.Command(None, "S", group=parent_group_1, order=5)
+    command_t = toga.Command(None, "T", group=child_group_2, order=2)
+    command_u = toga.Command(None, "U", group=child_group_2, order=1)
+    command_v = toga.Command(None, "V", group=parent_group_1, order=3)
+    command_w = toga.Command(None, "W", group=child_group_1, order=4)
+    command_x = toga.Command(None, "X", group=child_group_1, order=2)
+    command_y = toga.Command(None, "Y", group=child_group_1, order=1)
+    command_z = toga.Command(None, "Z", group=parent_group_1, order=1)
+
+    commands = [
+        command_z,
+        command_y,
+        command_x,
+        command_w,
+        command_b,
+        command_v,
+        command_u,
+        command_t,
+        command_s,
+        command_a,
+    ]
+
+    # Do this a couple of times to make sure insertion order doesn't matter
+    for _ in range(0, 10):
+        random.shuffle(commands)
+        cs = CommandSet()
+        cs.add(*commands)
+
+        assert list(cs) == [
+            command_z,
+            GROUP_BREAK,
+            command_y,
+            command_x,
+            command_w,
+            SECTION_BREAK,
+            command_b,
+            GROUP_BREAK,
+            command_v,
+            GROUP_BREAK,
+            command_u,
+            command_t,
+            GROUP_BREAK,
+            command_s,
+            GROUP_BREAK,
+            command_a,
+        ]
diff --git a/core/tests/command/test_group.py b/core/tests/command/test_group.py
new file mode 100644
index 0000000000..e4519aa8ae
--- /dev/null
+++ b/core/tests/command/test_group.py
@@ -0,0 +1,290 @@
+import pytest
+
+import toga
+
+from .test_command import assert_order
+
+
+def test_create():
+    """A group can be created with defaults"""
+    grp = toga.Group("Group name")
+    assert grp.text == "Group name"
+    assert grp.order == 0
+
+    assert repr(grp) == "<Group text='Group name' order=0>"
+
+
+def test_create_with_params():
+    """A fully specified group can be created"""
+    parent = toga.Group("Parent name")
+    grp = toga.Group("Group name", order=2, section=3, parent=parent)
+
+    assert grp.text == "Group name"
+    assert grp.order == 2
+    assert grp.section == 3
+    assert grp.parent == parent
+
+    assert (
+        repr(grp)
+        == "<Group text='Group name' order=2 parent=<Group text='Parent name' order=0> section=3>"
+    )
+
+
+def test_create_section_without_parent():
+    """A group cannot be created with a section but no parent."""
+    with pytest.raises(
+        ValueError,
+        match=r"Section cannot be set without parent group",
+    ):
+        toga.Group("Group name", order=2, section=3)
+
+
+def test_hashable():
+    """Groups are hashable."""
+    grp1 = toga.Group("text 1")
+    grp2 = toga.Group("text 2")
+
+    # The hash is based on the full path, not just the text.
+    # This allows texts to be non-unique, as long as they're in
+    # different groups
+    grp1_child = toga.Group("text", parent=grp1)
+    grp2_child = toga.Group("text", parent=grp2)
+
+    # Insert the groups as keys in a dict. This is
+    # only possible if Group is hashable.
+    groups = {
+        grp1: "First",
+        grp2: "Second",
+        grp1_child: "Child of 1",
+        grp2_child: "Child of 2",
+    }
+
+    assert groups[grp1] == "First"
+    assert groups[grp2] == "Second"
+    assert groups[grp1_child] == "Child of 1"
+    assert groups[grp2_child] == "Child of 2"
+
+
+def test_group_eq():
+    """Groups can be compared for equality."""
+    group_a = toga.Group("A")
+    group_b = toga.Group("B")
+    group_a1 = toga.Group("A", order=1)
+    # Assign None to variable to trick flake8 into not giving an E711
+    other = None
+
+    # Same instance is equal
+    assert group_a == group_a
+    assert group_a1 == group_a1
+
+    # Same values are equal
+    assert group_a == toga.Group("A")
+    assert group_a1 == toga.Group("A", order=1)
+
+    # Different values are not equal
+    assert group_a != group_b
+    assert group_a != other
+
+    # Partially same values are not equal
+    assert group_a1 != group_a
+    assert group_a1 != toga.Group("B", order=1)
+    assert group_a1 != toga.Group("A", order=2)
+
+
+def test_parent_creation():
+    """Parents can be assigned at creation"""
+    group_a = toga.Group("A")
+    group_b = toga.Group("B", parent=group_a)
+    group_c = toga.Group("C", parent=group_b)
+
+    # None checks
+    assert not group_a.is_parent_of(None)
+    assert not group_a.is_child_of(None)
+
+    # Parent relationships
+    assert group_a.is_parent_of(group_b)
+    assert group_b.is_parent_of(group_c)
+    assert group_a.is_parent_of(group_c)  # grandparent
+
+    # Child relationships
+    assert group_b.is_child_of(group_a)
+    assert group_c.is_child_of(group_b)
+    assert group_c.is_child_of(group_a)  # grandchild
+
+    # Reverse direction relationships aren't true
+    assert not group_a.is_child_of(group_b)
+    assert not group_b.is_child_of(group_c)
+    assert not group_a.is_child_of(group_c)
+
+    assert not group_b.is_parent_of(group_a)
+    assert not group_c.is_parent_of(group_b)
+    assert not group_c.is_parent_of(group_a)
+
+    assert group_a.parent is None
+    assert group_a.root == group_a
+
+    assert group_b.parent == group_a
+    assert group_b.root == group_a
+
+    assert group_c.parent == group_b
+    assert group_c.root == group_a
+
+
+def test_parent_assignment():
+    """Parents can be assigned at runtime"""
+    # Eventually, we'll end up with A->B->C, D.
+    group_a = toga.Group("A")
+    group_b = toga.Group("B")
+    group_c = toga.Group("C")
+    group_d = toga.Group("D")
+
+    assert not group_a.is_parent_of(group_b)
+    assert not group_b.is_parent_of(group_c)
+    assert not group_a.is_parent_of(group_c)
+    assert not group_b.is_parent_of(group_d)
+    assert not group_a.is_parent_of(group_d)
+
+    assert not group_b.is_child_of(group_a)
+    assert not group_c.is_child_of(group_b)
+    assert not group_c.is_child_of(group_a)
+    assert not group_d.is_child_of(group_b)
+    assert not group_d.is_child_of(group_a)
+
+    assert not group_a.is_child_of(group_b)
+    assert not group_b.is_child_of(group_c)
+    assert not group_a.is_child_of(group_c)
+    assert not group_b.is_child_of(group_d)
+    assert not group_a.is_child_of(group_d)
+
+    assert not group_b.is_parent_of(group_a)
+    assert not group_c.is_parent_of(group_b)
+    assert not group_c.is_parent_of(group_a)
+    assert not group_d.is_parent_of(group_b)
+    assert not group_d.is_parent_of(group_a)
+
+    assert group_a.parent is None
+    assert group_a.root == group_a
+
+    assert group_b.parent is None
+    assert group_b.root == group_b
+
+    assert group_c.parent is None
+    assert group_c.root == group_c
+
+    # Assign parents.
+    # C is assigned to B *before* B is assigned to A.
+    # D is assigned to B *after* B is assigned to A.
+    # This ensures that root isn't preserved in an intermediate state
+    group_c.parent = group_b
+    group_b.parent = group_a
+    group_d.parent = group_b
+
+    assert group_a.is_parent_of(group_b)
+    assert group_b.is_parent_of(group_c)
+    assert group_a.is_parent_of(group_c)  # grandparent
+    assert group_b.is_parent_of(group_d)
+    assert group_a.is_parent_of(group_d)  # grandparent
+
+    assert group_b.is_child_of(group_a)
+    assert group_c.is_child_of(group_b)
+    assert group_c.is_child_of(group_a)  # grandchild
+    assert group_d.is_child_of(group_b)
+    assert group_d.is_child_of(group_a)  # grandchild
+
+    # Reverse direction relationships aren't true
+    assert not group_a.is_child_of(group_b)
+    assert not group_b.is_child_of(group_c)
+    assert not group_a.is_child_of(group_c)
+    assert not group_b.is_child_of(group_d)
+    assert not group_a.is_child_of(group_d)
+
+    assert not group_b.is_parent_of(group_a)
+    assert not group_c.is_parent_of(group_b)
+    assert not group_c.is_parent_of(group_a)
+    assert not group_d.is_parent_of(group_b)
+    assert not group_d.is_parent_of(group_a)
+
+    assert group_a.parent is None
+    assert group_a.root == group_a
+
+    assert group_b.parent == group_a
+    assert group_b.root == group_a
+
+    assert group_c.parent == group_b
+    assert group_c.root == group_a
+
+    assert group_d.parent == group_b
+    assert group_d.root == group_a
+
+
+def test_parent_loops():
+    """Parent loops are prevented can be assigned at runtime"""
+    group_a = toga.Group("A")
+    group_b = toga.Group("B", parent=group_a)
+    group_c = toga.Group("C", parent=group_b)
+
+    #
+    with pytest.raises(
+        ValueError,
+        match=r"A group cannot be it's own parent",
+    ):
+        group_a.parent = group_a
+
+    with pytest.raises(
+        ValueError,
+        match=r"Cannot set parent; 'A' is an ancestor of 'B'.",
+    ):
+        group_a.parent = group_b
+
+    with pytest.raises(
+        ValueError,
+        match=r"Cannot set parent; 'A' is an ancestor of 'C'.",
+    ):
+        group_a.parent = group_c
+
+
+def test_order_by_text():
+    """Groups are ordered by text if order and section are equivalent"""
+    assert_order(toga.Group("A"), toga.Group("B"))
+
+
+def test_order_by_number():
+    """Groups are ordered by number"""
+    assert_order(toga.Group("B", order=1), toga.Group("A", order=2))
+
+
+def test_order_by_groups(parent_group_1, parent_group_2):
+    """Groups are ordered by parent, then section, then order."""
+    assert_order(
+        parent_group_1,
+        toga.Group("C", parent=parent_group_1),
+        toga.Group("D", parent=parent_group_1),
+        toga.Group("AA3", parent=parent_group_1, section=2),
+        toga.Group("AA2", parent=parent_group_1, section=3, order=1),
+        toga.Group("AA1", parent=parent_group_1, section=3, order=2),
+        parent_group_2,
+        toga.Group("B", parent=parent_group_2),
+    )
+
+
+# def test_cannot_set_self_as_parent(self):
+#     group = toga.Group("P")
+#     with self.assertRaises(ValueError):
+#         group.parent = group
+#     self.assert_parent_and_root(group, None, group)
+
+
+# def test_cannot_set_child_to_be_a_parent_of_its_grandparent(self):
+#     grandparent = toga.Group("G")
+#     parent = toga.Group("P", parent=grandparent)
+#     child = toga.Group("C", parent=parent)
+#     with self.assertRaises(ValueError):
+#         grandparent.parent = child
+#     self.assert_parent_and_root(grandparent, None, grandparent)
+#     self.assert_parent_and_root(parent, grandparent, grandparent)
+#     self.assert_parent_and_root(child, parent, grandparent)
+
+
+# def assert_parent_and_root(self, group, parent, root):
+#     self.assertEqual(group.parent, parent)
+#     self.assertEqual(group.root, root)
diff --git a/core/tests/conftest.py b/core/tests/conftest.py
index 59c769cff1..e8f8aabe89 100644
--- a/core/tests/conftest.py
+++ b/core/tests/conftest.py
@@ -1,8 +1,27 @@
+import sys
+
 import pytest
 
+import toga
 from toga_dummy.utils import EventLog
 
 
 @pytest.fixture(autouse=True)
 def reset_event_log():
     EventLog.reset()
+
+
+@pytest.fixture(autouse=True)
+def clear_sys_modules(monkeypatch):
+    try:
+        # App startup is influenced by things like the state of sys.modules, and the
+        # presence of __main__ in particular. Pytest doesn't need __main__ to work;
+        # so if it exists, delete it for the purposes of each test.
+        monkeypatch.delitem(sys.modules, "__main__")
+    except KeyError:
+        pass
+
+
+@pytest.fixture
+def app(event_loop):
+    return toga.App(formal_name="Test App", app_id="org.beeware.toga.test-app")
diff --git a/core/tests/test_app.py b/core/tests/test_app.py
deleted file mode 100644
index d5ad87ea3b..0000000000
--- a/core/tests/test_app.py
+++ /dev/null
@@ -1,214 +0,0 @@
-import asyncio
-from pathlib import Path
-from unittest.mock import Mock
-
-import toga
-from toga.widgets.base import WidgetRegistry
-from toga_dummy.utils import TestCase
-
-
-class AppTests(TestCase):
-    def setUp(self):
-        super().setUp()
-
-        self.name = "Test App"
-        self.app_id = "org.beeware.test-app"
-        self.id = "dom-id"
-
-        self.content = Mock()
-        self.content_id = "content-id"
-        self.content.id = self.content_id
-
-        self.started = False
-
-        def test_startup_function(app):
-            self.started = True
-            return self.content
-
-        self.app = toga.App(
-            formal_name=self.name,
-            app_id=self.app_id,
-            startup=test_startup_function,
-            id=self.id,
-        )
-
-    def test_app_name(self):
-        self.assertEqual(self.app.name, self.name)
-
-    def test_app_icon(self):
-        # App icon will default to a name autodetected from the running module
-        self.assertEqual(self.app.icon.path, Path("resources/toga"))
-        # This icon will be bound
-        self.assertIsNotNone(self.app.icon._impl)
-
-        # Set the icon to a different resource
-        self.app.icon = "other.icns"
-        self.assertEqual(self.app.icon.path, Path("other.icns"))
-
-        # This icon name will *not* exist. The Impl will be the DEFAULT_ICON's impl
-        self.assertEqual(self.app.icon._impl, toga.Icon.DEFAULT_ICON._impl)
-
-    def test_app_app_id(self):
-        self.assertEqual(self.app.app_id, self.app_id)
-
-    def test_app_id(self):
-        self.assertEqual(self.app.id, self.id)
-
-    def test_widgets_registry(self):
-        self.assertTrue(isinstance(self.app.widgets, WidgetRegistry))
-        self.assertEqual(len(self.app.widgets), 0)
-
-    def test_app_main_loop_call_impl_main_loop(self):
-        self.app.main_loop()
-        self.assertActionPerformed(self.app, "main loop")
-
-    def test_app_startup(self):
-        self.app.startup()
-
-        self.assertTrue(self.started)
-        self.assertEqual(self.app.main_window.content, self.content)
-        self.assertEqual(self.app.main_window.app, self.app)
-        self.assertActionPerformed(self.app.main_window, "show")
-
-    def test_is_full_screen(self):
-        self.assertFalse(self.app.is_full_screen)
-
-        self.app.set_full_screen(self.app.main_window)
-        self.assertTrue(self.app.is_full_screen)
-
-        self.app.set_full_screen(["window1", "window2", "window3"])
-        self.assertTrue(self.app.is_full_screen)
-
-        self.app.set_full_screen()
-        self.assertFalse(self.app.is_full_screen)
-
-    def test_app_exit(self):
-        def exit_handler(widget):
-            return True
-
-        self.app.on_exit = exit_handler
-        self.assertIs(self.app.on_exit._raw, exit_handler)
-        self.app.exit()
-
-        self.assertActionPerformed(self.app, "exit")
-
-    def test_full_screen(self):
-        # set full screen and exit full screen
-        self.app.set_full_screen(self.app.main_window)
-        self.assertTrue(self.app.is_full_screen)
-        self.app.exit_full_screen()
-        self.assertFalse(self.app.is_full_screen)
-        # set full screen and set full with no args
-        self.app.set_full_screen(self.app.main_window)
-        self.assertTrue(self.app.is_full_screen)
-        self.app.set_full_screen()
-        self.assertFalse(self.app.is_full_screen)
-
-    def test_add_window(self):
-        self.assertEqual(len(self.app.windows), 0)
-        test_window = toga.Window()
-        self.assertEqual(len(self.app.windows), 1)
-        self.app.windows += test_window
-        self.assertEqual(len(self.app.windows), 1)
-        self.assertIs(test_window.app, self.app)
-
-        not_a_window = "not_a_window"
-        with self.assertRaises(TypeError):
-            self.app.windows += not_a_window
-
-    def test_remove_window(self):
-        test_window = toga.Window()
-        self.assertEqual(len(self.app.windows), 1)
-        self.app.windows -= test_window
-        self.assertEqual(len(self.app.windows), 0)
-
-        with self.assertRaises(TypeError):
-            self.app.windows -= "not_a_window"
-
-        with self.assertRaises(AttributeError):
-            self.app.windows -= test_window
-
-    def test_app_contains_window(self):
-        test_window = toga.Window()
-        self.assertTrue(test_window in self.app.windows)
-        self.app.windows -= test_window
-        self.assertFalse(test_window in self.app.windows)
-
-    def test_window_iteration(self):
-        test_windows = [
-            toga.Window(id=1),
-            toga.Window(id=2),
-            toga.Window(id=3),
-        ]
-        for window in test_windows:
-            self.app.windows += window
-        self.assertEqual(len(self.app.windows), 3)
-
-        for window in self.app.windows:
-            self.assertIn(window, test_windows)
-
-    def test_beep(self):
-        self.app.beep()
-        self.assertActionPerformed(self.app, "beep")
-
-    def test_add_background_task(self):
-        thing = Mock()
-
-        async def test_handler(sender):
-            thing()
-
-        self.app.add_background_task(test_handler)
-
-        async def run_test():
-            # Give the background task time to run.
-            await asyncio.sleep(0.1)
-            thing.assert_called_once()
-
-        self.app._impl.loop.run_until_complete(run_test())
-
-    def test_override_startup(self):
-        class BadApp(toga.App):
-            "A startup method that doesn't assign main window raises an error (#760)"
-
-            def startup(self):
-                # Override startup but don't create a main window
-                pass
-
-        app = BadApp(app_name="bad_app", formal_name="Bad Aoo", app_id="org.beeware")
-        with self.assertRaisesRegex(
-            ValueError,
-            r"Application does not have a main window.",
-        ):
-            app.main_loop()
-
-
-class DocumentAppTests(TestCase):
-    def setUp(self):
-        super().setUp()
-
-        self.name = "Test Document App"
-        self.app_id = "beeware.org"
-        self.id = "id"
-
-        self.content = Mock()
-
-        self.app = toga.DocumentApp(self.name, self.app_id, id=self.id)
-
-    def test_app_documents(self):
-        self.assertEqual(self.app.documents, [])
-
-        doc = Mock()
-        self.app._documents.append(doc)
-        self.assertEqual(self.app.documents, [doc])
-
-    def test_override_startup(self):
-        mock = Mock()
-
-        class DocApp(toga.DocumentApp):
-            def startup(self):
-                # A document app doesn't have to provide a Main Window.
-                mock()
-
-        app = DocApp(app_name="docapp", formal_name="Doc App", app_id="org.beeware")
-        app.main_loop()
-        mock.assert_called_once()
diff --git a/core/tests/test_deprecated_factory.py b/core/tests/test_deprecated_factory.py
deleted file mode 100644
index 4ce4680c58..0000000000
--- a/core/tests/test_deprecated_factory.py
+++ /dev/null
@@ -1,46 +0,0 @@
-import toga
-from toga_dummy.utils import TestCase
-
-
-class DeprecatedFactoryTests(TestCase):
-    def setUp(self):
-        super().setUp()
-        self.factory = object()
-        self.callback = lambda x: None
-
-    ######################################################################
-    # 2022-09: Backwards compatibility
-    ######################################################################
-    # factory no longer used
-
-    def test_app(self):
-        with self.assertWarns(DeprecationWarning):
-            widget = toga.App(
-                formal_name="Test", app_id="org.beeware.test-app", factory=self.factory
-            )
-        self.assertEqual(widget._impl.interface, widget)
-        self.assertNotEqual(widget.factory, self.factory)
-
-    def test_document_app(self):
-        with self.assertWarns(DeprecationWarning):
-            widget = toga.DocumentApp(
-                formal_name="Test", app_id="org.beeware.test-app", factory=self.factory
-            )
-        self.assertEqual(widget._impl.interface, widget)
-        self.assertNotEqual(widget.factory, self.factory)
-
-    def test_command(self):
-        with self.assertWarns(DeprecationWarning):
-            widget = toga.Command(self.callback, "Test", factory=self.factory)
-        with self.assertWarns(DeprecationWarning):
-            widget.bind(factory=self.factory)
-        self.assertEqual(widget._impl.interface, widget)
-        self.assertNotEqual(widget.factory, self.factory)
-
-    def test_command_set(self):
-        with self.assertWarns(DeprecationWarning):
-            toga.CommandSet(factory=self.factory)
-
-    ######################################################################
-    # End backwards compatibility.
-    ######################################################################
diff --git a/core/tests/test_documents.py b/core/tests/test_documents.py
index cb00665d14..a0da06a9a9 100644
--- a/core/tests/test_documents.py
+++ b/core/tests/test_documents.py
@@ -1,22 +1,52 @@
+from pathlib import Path
+
+import pytest
+
 import toga
-import toga_dummy
-from toga_dummy.utils import TestCase
 
 
-class DocumentTests(TestCase):
-    def setUp(self):
-        super().setUp()
+class MyDoc(toga.Document):
+    def __init__(self, path, app):
+        super().__init__(path, "Dummy Document", app)
+        pass
+
+    def create(self):
+        pass
+
+    def read(self):
+        pass
+
+
+@pytest.mark.parametrize("path", ["/path/to/doc.mydoc", Path("/path/to/doc.mydoc")])
+def test_create_document(app, path):
+    doc = MyDoc(path, app)
 
-        self.filename = "path/to/document.txt"
-        self.document_type = "path/to/document.txt"
-        self.document = toga.Document(
-            filename=self.filename, document_type=self.document_type, app=toga_dummy
+    assert doc.path == Path(path)
+    assert doc.app == app
+    assert doc.document_type == "Dummy Document"
+
+
+class MyDeprecatedDoc(toga.Document):
+    def __init__(self, filename, app):
+        super().__init__(
+            path=filename,
+            document_type="Deprecated Document",
+            app=app,
         )
 
-    def test_app(self):
-        self.assertEqual(self.filename, self.document.filename)
-        self.assertEqual(self.document.app, toga_dummy)
+    def create(self):
+        pass
+
+    def read(self):
+        pass
+
+
+def test_deprecated_names(app):
+    """Deprecated names still work."""
+    doc = MyDeprecatedDoc("/path/to/doc.mydoc", app)
 
-    def test_read(self):
-        with self.assertRaises(NotImplementedError):
-            self.document.read()
+    with pytest.warns(
+        DeprecationWarning,
+        match=r"Document.filename has been renamed Document.path.",
+    ):
+        assert doc.filename == Path("/path/to/doc.mydoc")
diff --git a/core/tests/test_handlers.py b/core/tests/test_handlers.py
index 32dbdcc818..1d7e29f2e0 100644
--- a/core/tests/test_handlers.py
+++ b/core/tests/test_handlers.py
@@ -71,7 +71,7 @@ def handler(*args, **kwargs):
     assert wrapped._raw == handler
 
     # Invoke wrapper
-    wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+    wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
 
     # Handler arguments are as expected.
     assert handler_call == {
@@ -95,7 +95,7 @@ def handler(*args, **kwargs):
     assert wrapped._raw == handler
 
     # Invoke handler. The exception is swallowed
-    wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+    wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
 
     # Handler arguments are as expected.
     assert handler_call == {
@@ -127,7 +127,7 @@ def handler(*args, **kwargs):
     assert wrapped._raw == handler
 
     # Invoke handler
-    wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+    wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
 
     # Handler arguments are as expected.
     assert handler_call == {
@@ -156,7 +156,7 @@ def handler(*args, **kwargs):
     assert wrapped._raw == handler
 
     # Invoke handler. The exception in cleanup is swallowed
-    wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+    wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
 
     # Handler arguments are as expected.
     assert handler_call == {
@@ -194,7 +194,7 @@ def handler(*args, **kwargs):
 
     # Invoke wrapper inside an active run loop.
     async def waiter():
-        wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+        wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
         count = 0
         while not handler_call.get("done", False) and count < 5:
             await asyncio.sleep(0.01)
@@ -229,7 +229,7 @@ def handler(*args, **kwargs):
 
     # Invoke wrapper inside an active run loop.
     async def waiter():
-        wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+        wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
         count = 0
         while not handler_call.get("done", False) and count < 5:
             await asyncio.sleep(0.01)
@@ -272,7 +272,7 @@ def handler(*args, **kwargs):
 
     # Invoke wrapper inside an active run loop.
     async def waiter():
-        wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+        wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
         count = 0
         while not handler_call.get("done", False) and count < 5:
             await asyncio.sleep(0.01)
@@ -314,7 +314,7 @@ def handler(*args, **kwargs):
 
     # Invoke wrapper inside an active run loop.
     async def waiter():
-        wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+        wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
         count = 0
         while not handler_call.get("done", False) and count < 5:
             await asyncio.sleep(0.01)
@@ -358,7 +358,7 @@ async def handler(*args, **kwargs):
 
     # Invoke wrapper inside an active run loop.
     async def waiter():
-        wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+        wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
         count = 0
         while not handler_call.get("done", False) and count < 5:
             await asyncio.sleep(0.01)
@@ -392,7 +392,7 @@ async def handler(*args, **kwargs):
 
     # Invoke wrapper inside an active run loop.
     async def waiter():
-        wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+        wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
         count = 0
         while not handler_call.get("done", False) and count < 5:
             await asyncio.sleep(0.01)
@@ -433,7 +433,7 @@ async def handler(*args, **kwargs):
 
     # Invoke wrapper inside an active run loop.
     async def waiter():
-        wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+        wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
         count = 0
         while not handler_call.get("done", False) and count < 5:
             await asyncio.sleep(0.01)
@@ -472,7 +472,7 @@ async def handler(*args, **kwargs):
 
     # Invoke wrapper inside an active run loop.
     async def waiter():
-        wrapped("dummy", "arg1", "arg2", kwarg1=3, kwarg2=4)
+        wrapped("arg1", "arg2", kwarg1=3, kwarg2=4)
         count = 0
         while not handler_call.get("done", False) and count < 5:
             await asyncio.sleep(0.01)
diff --git a/core/tests/test_images.py b/core/tests/test_images.py
index 787cc2ed59..85f3321349 100644
--- a/core/tests/test_images.py
+++ b/core/tests/test_images.py
@@ -9,11 +9,6 @@
 ABSOLUTE_FILE_PATH = Path(toga.__file__).parent / "resources" / "toga.png"
 
 
-@pytest.fixture
-def app():
-    return toga.App("Images Test", "org.beeware.toga.images")
-
-
 @pytest.mark.parametrize(
     "args, kwargs",
     [
@@ -109,10 +104,18 @@ def test_dimensions():
 
     image = toga.Image(path="resources/toga.png")
 
+    assert image.size == (60, 40)
     assert image.width == 60
     assert image.height == 40
 
 
+def test_data():
+    "The raw data of the image can be retrieved."
+    image = toga.Image(path="resources/toga.png")
+
+    assert image.data == b"pretend this is PNG image data"
+
+
 def test_image_save():
     "An image can be saved"
     save_path = Path("/path/to/save.png")
diff --git a/core/tests/test_window.py b/core/tests/test_window.py
index 09bbf28ee4..61a5e1209e 100644
--- a/core/tests/test_window.py
+++ b/core/tests/test_window.py
@@ -11,11 +11,6 @@
 )
 
 
-@pytest.fixture
-def app(event_loop):
-    return toga.App("Test App", "org.beeware.toga.window")
-
-
 @pytest.fixture
 def window(app):
     return toga.Window()
@@ -75,12 +70,22 @@ def test_window_created_explicit(app):
     assert window.on_close._raw == on_close_handler
 
 
+def test_window_created_without_app():
+    "A window cannot be created without an active app"
+    toga.App.app = None
+    with pytest.raises(
+        RuntimeError, match="Cannot create a Window before creating an App"
+    ):
+        toga.Window()
+
+
 def test_set_app(window, app):
     """A window's app cannot be reassigned"""
     assert window.app == app
 
+    app2 = toga.App("Test App 2", "org.beeware.toga.test-app-2")
     with pytest.raises(ValueError, match=r"Window is already associated with an App"):
-        window.app = app
+        window.app = app2
 
 
 def test_set_app_with_content(window, app):
@@ -110,6 +115,31 @@ def test_title(window, value, expected):
     assert window.title == expected
 
 
+def test_toolbar_implicit_add(window, app):
+    """Adding an item to to a toolbar implicitly adds it to the app."""
+    cmd1 = toga.Command(None, "Command 1")
+    cmd2 = toga.Command(None, "Command 2")
+
+    toolbar = window.toolbar
+    assert list(toolbar) == []
+    assert list(app.commands) == []
+
+    # Adding a command to the toolbar automatically adds it to the app
+    toolbar.add(cmd1)
+    assert list(toolbar) == [cmd1]
+    assert list(app.commands) == [cmd1]
+
+    # But not vice versa
+    app.commands.add(cmd2)
+    assert list(toolbar) == [cmd1]
+    assert list(app.commands) == [cmd1, cmd2]
+
+    # Adding a command to both places does not cause a duplicate
+    app.commands.add(cmd1)
+    assert list(toolbar) == [cmd1]
+    assert list(app.commands) == [cmd1, cmd2]
+
+
 def test_change_content(window, app):
     """The content of a window can be changed"""
     assert window.content is None
@@ -316,6 +346,13 @@ def test_close_rejected_handler(window, app):
     on_close_handler.assert_called_once_with(window)
 
 
+def test_as_image(window):
+    """A window can be captured as an image"""
+    image = window.as_image()
+
+    assert image.data == b"pretend this is PNG image data"
+
+
 def test_info_dialog(window, app):
     """An info dialog can be shown"""
     on_result_handler = Mock()
diff --git a/core/tests/utils.py b/core/tests/utils.py
deleted file mode 100644
index 504132d874..0000000000
--- a/core/tests/utils.py
+++ /dev/null
@@ -1,22 +0,0 @@
-import asyncio
-
-
-def async_test(coroutine):
-    """Run an async test to completion."""
-
-    def _test(self):
-        asyncio.run(coroutine(self))
-
-    return _test
-
-
-def order_test(*items):
-    def _test(self):
-        for i in range(0, len(items) - 1):
-            for j in range(i + 1, len(items)):
-                self.assertLess(items[i], items[j])
-                self.assertGreater(items[j], items[i])
-                self.assertFalse(items[j] < items[i])
-                self.assertFalse(items[i] > items[j])
-
-    return _test
diff --git a/core/tests/widgets/canvas/test_helpers.py b/core/tests/widgets/canvas/test_helpers.py
new file mode 100644
index 0000000000..e3c414ce33
--- /dev/null
+++ b/core/tests/widgets/canvas/test_helpers.py
@@ -0,0 +1,218 @@
+from math import pi
+
+from pytest import approx
+
+from toga.widgets.canvas import arc_to_bezier, sweepangle
+
+
+def test_sweepangle():
+    # Zero start angles
+    for value in [0, 1, pi, 2 * pi]:
+        assert sweepangle(0, value, False) == approx(value)
+
+    for value in [2.1 * pi, 3 * pi, 4 * pi, 5 * pi]:
+        assert sweepangle(0, value, False) == approx(2 * pi)
+
+    # Non-zero start angles
+    assert sweepangle(pi, 2 * pi, False) == approx(pi)
+    assert sweepangle(pi, 2.5 * pi, False) == approx(1.5 * pi)
+    assert sweepangle(pi, 3 * pi, False) == approx(2 * pi)
+    assert sweepangle(pi, 3.1 * pi, False) == approx(2 * pi)
+
+    # Zero crossings
+    assert sweepangle(0, 2 * pi, False) == approx(2 * pi)
+    assert sweepangle(0, -2 * pi, False) == approx(0)
+    assert sweepangle(0, 1.9 * pi, False) == approx(1.9 * pi)
+    assert sweepangle(0, 2.1 * pi, False) == approx(2 * pi)
+    assert sweepangle(0, -1.9 * pi, False) == approx(0.1 * pi)
+    assert sweepangle(0, -2.1 * pi, False) == approx(1.9 * pi)
+    assert sweepangle(pi, 0, False) == approx(pi)
+    assert sweepangle(pi, 2 * pi, False) == approx(pi)
+    assert sweepangle(pi, 0.1 * pi, False) == approx(1.1 * pi)
+    assert sweepangle(pi, 2.1 * pi, False) == approx(1.1 * pi)
+
+    # Zero crossings, anticlockwise
+    assert sweepangle(0, 2 * pi, True) == approx(0)
+    assert sweepangle(0, -2 * pi, True) == approx(-2 * pi)
+    assert sweepangle(0, 1.9 * pi, True) == approx(-0.1 * pi)
+    assert sweepangle(0, 2.1 * pi, True) == approx(-1.9 * pi)
+    assert sweepangle(0, -1.9 * pi, True) == approx(-1.9 * pi)
+    assert sweepangle(0, -2.1 * pi, True) == approx(-2 * pi)
+    assert sweepangle(pi, 0, True) == approx(-pi)
+    assert sweepangle(pi, 2 * pi, True) == approx(-pi)
+    assert sweepangle(pi, 0.1 * pi, True) == approx(-0.9 * pi)
+    assert sweepangle(pi, 2.1 * pi, True) == approx(-0.9 * pi)
+
+
+def assert_arc_to_bezier(sweepangle, expected):
+    actual = arc_to_bezier(sweepangle)
+    for a, e in zip(actual, expected):
+        assert a == approx(e, abs=0.000001)
+
+
+def test_arc_to_bezier():
+    assert_arc_to_bezier(
+        0,
+        [
+            (1.0, 0.0),
+            (1.0, 0.0),
+            (1.0, 0.0),
+            (1.0, 0.0),
+        ],
+    )
+
+    assert_arc_to_bezier(
+        0.25 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, 0.2652164),
+            (0.8946431, 0.5195704),
+            (0.7071067, 0.7071067),
+        ],
+    )
+    assert_arc_to_bezier(
+        -0.25 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, -0.2652164),
+            (0.8946431, -0.5195704),
+            (0.7071067, -0.7071067),
+        ],
+    )
+
+    assert_arc_to_bezier(
+        0.5 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, 0.5522847),
+            (0.5522847, 1.0),
+            (0.0, 1.0),
+        ],
+    )
+    assert_arc_to_bezier(
+        -0.5 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, -0.5522847),
+            (0.5522847, -1.0),
+            (0.0, -1.0),
+        ],
+    )
+
+    assert_arc_to_bezier(
+        0.75 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, 0.5522847),
+            (0.5522847, 1.0),
+            (0.0, 1.0),
+            (-0.2652164, 1.0),
+            (-0.5195704, 0.8946431),
+            (-0.7071067, 0.7071067),
+        ],
+    )
+    assert_arc_to_bezier(
+        -0.75 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, -0.5522847),
+            (0.5522847, -1.0),
+            (0.0, -1.0),
+            (-0.2652164, -1.0),
+            (-0.5195704, -0.8946431),
+            (-0.7071067, -0.7071067),
+        ],
+    )
+
+    assert_arc_to_bezier(
+        1 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, 0.5522847),
+            (0.5522847, 1.0),
+            (0.0, 1.0),
+            (-0.5522847, 1.0),
+            (-1.0, 0.5522847),
+            (-1.0, 0.0),
+        ],
+    )
+    assert_arc_to_bezier(
+        -1 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, -0.5522847),
+            (0.5522847, -1.0),
+            (0.0, -1.0),
+            (-0.5522847, -1.0),
+            (-1.0, -0.5522847),
+            (-1.0, 0.0),
+        ],
+    )
+
+    assert_arc_to_bezier(
+        1.5 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, 0.5522847),
+            (0.5522847, 1.0),
+            (0.0, 1.0),
+            (-0.5522847, 1.0),
+            (-1.0, 0.5522847),
+            (-1.0, 0.0),
+            (-1.0, -0.5522847),
+            (-0.5522847, -1.0),
+            (0.0, -1.0),
+        ],
+    )
+    assert_arc_to_bezier(
+        -1.5 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, -0.5522847),
+            (0.5522847, -1.0),
+            (0.0, -1.0),
+            (-0.5522847, -1.0),
+            (-1.0, -0.5522847),
+            (-1.0, 0.0),
+            (-1.0, 0.5522847),
+            (-0.5522847, 1.0),
+            (0.0, 1.0),
+        ],
+    )
+
+    assert_arc_to_bezier(
+        2 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, 0.5522847),
+            (0.5522847, 1.0),
+            (0.0, 1.0),
+            (-0.5522847, 1.0),
+            (-1.0, 0.5522847),
+            (-1.0, 0.0),
+            (-1.0, -0.5522847),
+            (-0.5522847, -1.0),
+            (0.0, -1.0),
+            (0.5522847, -1.0),
+            (1.0, -0.5522847),
+            (1.0, 0.0),
+        ],
+    )
+    assert_arc_to_bezier(
+        -2 * pi,
+        [
+            (1.0, 0.0),
+            (1.0, -0.5522847),
+            (0.5522847, -1.0),
+            (0.0, -1.0),
+            (-0.5522847, -1.0),
+            (-1.0, -0.5522847),
+            (-1.0, 0.0),
+            (-1.0, 0.5522847),
+            (-0.5522847, 1.0),
+            (0.0, 1.0),
+            (0.5522847, 1.0),
+            (1.0, 0.5522847),
+            (1.0, 0.0),
+        ],
+    )
diff --git a/core/tests/widgets/test_base.py b/core/tests/widgets/test_base.py
index b3f3ca810a..7bf7eba305 100644
--- a/core/tests/widgets/test_base.py
+++ b/core/tests/widgets/test_base.py
@@ -110,10 +110,9 @@ def test_add_child_without_app(widget):
     assert_action_performed_with(widget, "refresh")
 
 
-def test_add_child(widget):
+def test_add_child(app, widget):
     "A child can be added to a node when there's an app & window"
     # Set the app and window for the widget.
-    app = toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = widget
     # Clear the event log
@@ -163,10 +162,9 @@ def test_add_child(widget):
     assert app.widgets["child_id"] == child
 
 
-def test_add_multiple_children(widget):
+def test_add_multiple_children(app, widget):
     "Multiple children can be added in one call"
     # Set the app and window for the widget.
-    app = toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = widget
     # Clear the event log
@@ -341,10 +339,9 @@ def test_insert_child_without_app(widget):
     assert_action_performed_with(widget, "refresh")
 
 
-def test_insert_child(widget):
+def test_insert_child(app, widget):
     "A child can be inserted into a node when there's an app & window"
     # Set the app and window for the widget.
-    app = toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = widget
     # Clear the event log
@@ -397,10 +394,9 @@ def test_insert_child(widget):
     }
 
 
-def test_insert_position(widget):
+def test_insert_position(app, widget):
     "Insert can put a child into a specific position"
     # Set the app and window for the widget.
-    app = toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = widget
     # Clear the event log
@@ -473,10 +469,9 @@ def test_insert_position(widget):
     }
 
 
-def test_insert_bad_position(widget):
+def test_insert_bad_position(app, widget):
     "If the position is invalid, an error is raised"
     # Set the app and window for the widget.
-    app = toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = widget
     # Clear the event log
@@ -637,13 +632,12 @@ def test_remove_child_without_app(widget):
     assert_action_performed_with(widget, "refresh")
 
 
-def test_remove_child(widget):
+def test_remove_child(app, widget):
     "A child associated with an app & window can be removed from a widget"
     # Add a child to the widget
     child = ExampleLeafWidget(id="child_id")
     widget.add(child)
 
-    app = toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = widget
     # Clear the event log
@@ -684,7 +678,7 @@ def test_remove_child(widget):
     assert "child_id" not in app.widgets
 
 
-def test_remove_multiple_children(widget):
+def test_remove_multiple_children(app, widget):
     "Multiple children can be removed from a widget"
     # Add children to the widget
     child1 = ExampleLeafWidget(id="child1_id")
@@ -692,7 +686,6 @@ def test_remove_multiple_children(widget):
     child3 = ExampleLeafWidget(id="child3_id")
     widget.add(child1, child2, child3)
 
-    app = toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = widget
     # Clear the event log
@@ -744,7 +737,7 @@ def test_remove_multiple_children(widget):
     assert "child3_id" not in window.widgets
 
 
-def test_clear_all_children(widget):
+def test_clear_all_children(app, widget):
     "All children can be simultaneously removed from a widget"
     # Add children to the widget
     child1 = ExampleLeafWidget(id="child1_id")
@@ -752,7 +745,6 @@ def test_clear_all_children(widget):
     child3 = ExampleLeafWidget(id="child3_id")
     widget.add(child1, child2, child3)
 
-    app = toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = widget
     # Clear the event log
@@ -807,9 +799,8 @@ def test_clear_all_children(widget):
     assert "child3_id" not in window.widgets
 
 
-def test_clear_no_children(widget):
+def test_clear_no_children(app, widget):
     "No changes are made (no-op) if widget has no children"
-    toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = widget
     # Clear the event log
@@ -830,10 +821,9 @@ def test_clear_no_children(widget):
     assert_action_not_performed(window.content, "refresh")
 
 
-def test_clear_leaf():
+def test_clear_leaf(app):
     "`clear` cannot be called on a leaf node"
     leaf = ExampleLeafWidget()
-    toga.App("Test", "com.example.test")
     window = toga.Window()
     window.content = leaf
     # Clear the event log
@@ -881,9 +871,8 @@ def test_remove_from_non_parent(widget):
     assert_action_not_performed(widget, "refresh")
 
 
-def test_set_app(widget):
+def test_set_app(app, widget):
     "A widget can be assigned to an app"
-    app = toga.App("Test App", "org.beeware.test")
     assert len(app.widgets) == 0
 
     # Assign the widget to an app
@@ -900,7 +889,7 @@ def test_set_app(widget):
     assert attribute_value(widget, "app") == app
 
 
-def test_set_app_with_children(widget):
+def test_set_app_with_children(app, widget):
     "If a widget has children, the children get the app assignment"
     # Add children to the widget
     child1 = ExampleLeafWidget(id="child1_id")
@@ -908,8 +897,6 @@ def test_set_app_with_children(widget):
     child3 = ExampleLeafWidget(id="child3_id")
     widget.add(child1, child2, child3)
 
-    # Set up an app
-    app = toga.App("Test App", "org.beeware.test")
     assert len(app.widgets) == 0
 
     # Assign the widget to an app
@@ -937,9 +924,8 @@ def test_set_app_with_children(widget):
     assert attribute_value(child3, "app") == app
 
 
-def test_set_same_app(widget):
+def test_set_same_app(app, widget):
     "A widget can be re-assigned to the same app"
-    app = toga.App("Test App", "org.beeware.test")
     assert len(app.widgets) == 0
 
     # Assign the widget to an app
@@ -955,9 +941,8 @@ def test_set_same_app(widget):
     assert_attribute_not_set(widget, "app")
 
 
-def test_reset_app(widget):
+def test_reset_app(app, widget):
     "A widget can be re-assigned to no app"
-    app = toga.App("Test App", "org.beeware.test")
     assert len(app.widgets) == 0
 
     # Assign the widget to an app
@@ -979,10 +964,8 @@ def test_reset_app(widget):
     assert attribute_value(widget, "app") is None
 
 
-def test_set_new_app(widget):
+def test_set_new_app(app, widget):
     "A widget can be assigned to a different app"
-    app = toga.App("Test App", "org.beeware.test")
-
     # Assign the widget to an app
     widget.app = app
     assert len(app.widgets) == 1
@@ -991,7 +974,7 @@ def test_set_new_app(widget):
     EventLog.reset()
 
     # Create a new app
-    new_app = toga.App("Test App", "org.beeware.test")
+    new_app = toga.App("Test App", "org.beeware.toga.test-app")
     assert len(new_app.widgets) == 0
 
     # Assign the widget to the same app
diff --git a/core/tests/widgets/test_imageview.py b/core/tests/widgets/test_imageview.py
index 447d4542e2..f4d99c29c2 100644
--- a/core/tests/widgets/test_imageview.py
+++ b/core/tests/widgets/test_imageview.py
@@ -14,11 +14,6 @@
 )
 
 
-@pytest.fixture
-def app():
-    return toga.App("ImageView Test", "org.beeware.toga.widgets.imageview")
-
-
 @pytest.fixture
 def widget(app):
     return toga.ImageView()
diff --git a/core/tests/widgets/test_optioncontainer.py b/core/tests/widgets/test_optioncontainer.py
index 505f34d64c..4431b238fd 100644
--- a/core/tests/widgets/test_optioncontainer.py
+++ b/core/tests/widgets/test_optioncontainer.py
@@ -10,11 +10,6 @@
 )
 
 
-@pytest.fixture
-def app():
-    return toga.App("Option Container Test", "org.beeware.toga.option_container")
-
-
 @pytest.fixture
 def window():
     return toga.Window()
diff --git a/core/tests/widgets/test_scrollcontainer.py b/core/tests/widgets/test_scrollcontainer.py
index 114049aff6..024701bce9 100644
--- a/core/tests/widgets/test_scrollcontainer.py
+++ b/core/tests/widgets/test_scrollcontainer.py
@@ -11,11 +11,6 @@
 )
 
 
-@pytest.fixture
-def app():
-    return toga.App("Scroll Container Test", "org.beeware.toga.scroll_container")
-
-
 @pytest.fixture
 def window():
     return toga.Window()
diff --git a/core/tests/widgets/test_slider.py b/core/tests/widgets/test_slider.py
index d804f79db4..8f53e12f84 100644
--- a/core/tests/widgets/test_slider.py
+++ b/core/tests/widgets/test_slider.py
@@ -229,36 +229,44 @@ def test_range(slider, on_change, min, max, value):
 
 
 @pytest.mark.parametrize(
-    "new_min, new_max",
+    "new_min, new_value, new_max",
     [
-        [-5, 10],  # less than old min
-        [5, 10],  # more than old min, less than max
-        [15, 15],  # more than max
+        [-5, 5, 10],  # less than old min
+        [5, 5, 10],  # more than old min
+        [6, 6, 10],  # more than old min and value
+        [15, 15, 15],  # more than old min, value and max
     ],
 )
-def test_min_clipping(slider, new_min, new_max):
+def test_min_clipping(slider, new_min, new_value, new_max):
+    slider.tick_count = None
     slider.min = 0
+    slider.value = 5
     slider.max = 10
 
     slider.min = new_min
     assert slider.min == new_min
+    assert slider.value == new_value
     assert slider.max == new_max
 
 
 @pytest.mark.parametrize(
-    "new_max, new_min",
+    "new_min, new_value, new_max",
     [
-        [15, 0],  # less than old max
-        [5, 0],  # less than old max, more than min
-        [-5, -5],  # less than min
+        [0, 5, 15],  # more than old max
+        [0, 5, 5],  # less than old max
+        [0, 4, 4],  # less than old max and value
+        [-5, -5, -5],  # less than old max, value and min
     ],
 )
-def test_max_clipping(slider, new_max, new_min):
+def test_max_clipping(slider, new_min, new_value, new_max):
+    slider.tick_count = None
     slider.min = 0
+    slider.value = 5
     slider.max = 10
 
     slider.max = new_max
     assert slider.min == new_min
+    assert slider.value == new_value
     assert slider.max == new_max
 
 
@@ -429,7 +437,7 @@ def test_int_impl_continuous():
         assert impl.int_value == int_value
         assert impl.get_value() == value
 
-    # Check a range that doesn't start at zero.
+    # Range that doesn't start at zero
     impl.set_min(-0.4)
     assert impl.get_min() == pytest.approx(-0.4)
     impl.set_max(0.6)
@@ -437,6 +445,23 @@ def test_int_impl_continuous():
     impl.set_value(0.5)
     assert impl.get_value() == 0.5
     assert impl.int_value == 9000
+    assert impl.int_max == 10000
+
+    # Empty range
+    impl.set_min(0)
+    impl.set_max(0)
+    impl.set_value(0)
+    assert impl.get_value() == 0
+    assert impl.int_value == 0
+    assert impl.int_max == 10000
+
+    # Empty range that doesn't start at zero
+    impl.set_min(1)
+    impl.set_max(1)
+    impl.set_value(1)
+    assert impl.get_value() == 1
+    assert impl.int_value == 0
+    assert impl.int_max == 10000
 
 
 def test_int_impl_discrete():
@@ -467,7 +492,7 @@ def test_int_impl_discrete():
         assert impl.get_value() == value
         assert impl.int_value == int_value
 
-    # Check a range that doesn't start at zero.
+    # Range that doesn't start at zero
     impl.set_min(-0.4)
     assert impl.get_min() == pytest.approx(-0.4)
     impl.set_max(0.6)
@@ -475,6 +500,23 @@ def test_int_impl_discrete():
     impl.set_value(0.5)
     assert impl.get_value() == 0.5
     assert impl.int_value == 7
+    assert impl.int_max == 8
+
+    # Empty range
+    impl.set_min(0)
+    impl.set_max(0)
+    impl.set_value(0)
+    assert impl.get_value() == 0
+    assert impl.int_value == 0
+    assert impl.int_max == 8
+
+    # Empty range that doesn't start at zero
+    impl.set_min(1)
+    impl.set_max(1)
+    impl.set_value(1)
+    assert impl.get_value() == 1
+    assert impl.int_value == 0
+    assert impl.int_max == 8
 
 
 @pytest.mark.parametrize(
@@ -501,7 +543,7 @@ def test_int_impl_on_change(tick_count, data):
         impl.int_value = int_value
         impl.on_change()
         assert impl.get_value() == approx(value)
-        impl.interface.on_change.assert_called_once_with(None)
+        impl.interface.on_change.assert_called_once_with()
 
 
 def test_deprecated():
diff --git a/core/tests/widgets/test_splitcontainer.py b/core/tests/widgets/test_splitcontainer.py
index 6f6f88263c..e53b9a687c 100644
--- a/core/tests/widgets/test_splitcontainer.py
+++ b/core/tests/widgets/test_splitcontainer.py
@@ -8,11 +8,6 @@
 )
 
 
-@pytest.fixture
-def app():
-    return toga.App("Split Container Test", "org.beeware.toga.split_container")
-
-
 @pytest.fixture
 def window():
     return toga.Window()
diff --git a/demo/setup.cfg b/demo/setup.cfg
index 2831b799f6..d35fa90721 100644
--- a/demo/setup.cfg
+++ b/demo/setup.cfg
@@ -12,7 +12,7 @@ author_email = russell@keith-magee.com
 maintainer = BeeWare Team
 maintainer_email = team@beeware.org
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Intended Audience :: Developers
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
diff --git a/demo/toga_demo/app.py b/demo/toga_demo/app.py
index b4e020bb5d..507659e0f3 100755
--- a/demo/toga_demo/app.py
+++ b/demo/toga_demo/app.py
@@ -6,7 +6,7 @@
 class TogaDemo(toga.App):
     def startup(self):
         # Create the main window
-        self.main_window = toga.MainWindow(self.name)
+        self.main_window = toga.MainWindow()
 
         left_table = toga.Table(
             headings=["Hello", "World"],
@@ -18,20 +18,24 @@ def startup(self):
             ],
         )
 
-        left_tree = toga.Tree(
-            headings=["Navigate"],
-            data={
-                ("root1",): {},
-                ("root2",): {
-                    ("root2.1",): None,
-                    ("root2.2",): [
-                        ("root2.2.1",),
-                        ("root2.2.2",),
-                        ("root2.2.3",),
-                    ],
+        try:
+            left_tree = toga.Tree(
+                headings=["Navigate"],
+                data={
+                    ("root1",): {},
+                    ("root2",): {
+                        ("root2.1",): None,
+                        ("root2.2",): {
+                            ("root2.2.1",): None,
+                            ("root2.2.2",): None,
+                            ("root2.2.3",): None,
+                        },
+                    },
                 },
-            },
-        )
+            )
+        except NotImplementedError:
+            # For now, Winforms doesn't implement tree.
+            left_tree = toga.Box()
 
         left_container = toga.OptionContainer(
             content=[
diff --git a/docs/_static/custom.css b/docs/_static/custom.css
index c3b309ff5a..02b3970e25 100644
--- a/docs/_static/custom.css
+++ b/docs/_static/custom.css
@@ -23,3 +23,21 @@ span.beta, span.stable {
     font-size: x-large;
     line-height: 1;
 }
+
+.sphinx-tabs-tab span.beta {
+    color: lightslategray;
+    font-variant: italic;
+    font-size: smaller;
+    vertical-align: super;
+}
+
+.sphinx-tabs-tab span.no {
+    color: lightcoral;
+    font-variant: italic;
+    font-size: smaller;
+    vertical-align: super;
+}
+
+.sphinx-tabs-panel p {
+    text-align: center;
+}
diff --git a/docs/background/project/releases.rst b/docs/background/project/releases.rst
index 6727bbd250..4e62b06f00 100644
--- a/docs/background/project/releases.rst
+++ b/docs/background/project/releases.rst
@@ -6,6 +6,150 @@ Release History
 
 .. towncrier release notes start
 
+0.4.0 (2023-11-03)
+==================
+
+Features
+--------
+
+* The Toga API has been fully audited. All APIs now have 100% test coverage, complete API documentation (including type annotations), and are internally consistent. ( `#1903 <https://github.com/beeware/toga/issues/1903>`__, `#1938 <https://github.com/beeware/toga/issues/1938>`__, `#1944 <https://github.com/beeware/toga/issues/1944>`__, `#1946 <https://github.com/beeware/toga/issues/1946>`__, `#1949 <https://github.com/beeware/toga/issues/1949>`__, `#1951 <https://github.com/beeware/toga/issues/1951>`__, `#1955 <https://github.com/beeware/toga/issues/1955>`__, `#1956 <https://github.com/beeware/toga/issues/1956>`__, `#1964 <https://github.com/beeware/toga/issues/1964>`__, `#1969 <https://github.com/beeware/toga/issues/1969>`__, `#1984 <https://github.com/beeware/toga/issues/1984>`__, `#1996 <https://github.com/beeware/toga/issues/1996>`__, `#2011 <https://github.com/beeware/toga/issues/2011>`__, `#2017 <https://github.com/beeware/toga/issues/2017>`__, `#2025 <https://github.com/beeware/toga/issues/2025>`__, `#2029 <https://github.com/beeware/toga/issues/2029>`__, `#2044 <https://github.com/beeware/toga/issues/2044>`__, `#2058 <https://github.com/beeware/toga/issues/2058>`__, `#2075 <https://github.com/beeware/toga/issues/2075>`__)
+* Headings are no longer mandatory for Tree widgets. If headings are not provided, the widget will not display its header bar. (`#1767 <https://github.com/beeware/toga/issues/1767>`__)
+* Support for custom font loading was added to the GTK, Cocoa and iOS backends. (`#1837 <https://github.com/beeware/toga/issues/1837>`__)
+* The testbed app has better diagnostic output when running in test mode. (`#1847 <https://github.com/beeware/toga/issues/1847>`__)
+* A Textual backend was added to support terminal applications. (`#1867 <https://github.com/beeware/toga/issues/1867>`__)
+* Support for determining the currently active window was added to Winforms. (`#1872 <https://github.com/beeware/toga/issues/1872>`__)
+* Programmatically scrolling to top and bottom in MultilineTextInput is now possible on iOS. (`#1876 <https://github.com/beeware/toga/issues/1876>`__)
+* A handler has been added for users confirming the contents of a TextInput by pressing Enter/Return. (`#1880 <https://github.com/beeware/toga/issues/1880>`__)
+* An API for giving a window focus was added. (`#1887 <https://github.com/beeware/toga/issues/1887>`__)
+* Widgets now have a ``.clear()`` method to remove all child widgets. (`#1893 <https://github.com/beeware/toga/issues/1893>`__)
+* Winforms now supports hiding and re-showing the app cursor. (`#1894 <https://github.com/beeware/toga/issues/1894>`__)
+* ProgressBar and Switch widgets were added to the Web backend. (`#1901 <https://github.com/beeware/toga/issues/1901>`__)
+* Missing value handling was added to the Tree widget. (`#1913 <https://github.com/beeware/toga/issues/1913>`__)
+* App paths now include a ``config`` path for storing configuration files. (`#1964 <https://github.com/beeware/toga/issues/1964>`__)
+* A more informative error message is returned when a platform backend doesn't support a widget. (`#1992 <https://github.com/beeware/toga/issues/1992>`__)
+* The example apps were updated to support being run with ``briefcase run`` on all platforms. (`#1995 <https://github.com/beeware/toga/issues/1995>`__)
+* Headings are no longer mandatory Table widgets. (`#2011 <https://github.com/beeware/toga/issues/2011>`__)
+* Columns can now be added and removed from a Tree. (`#2017 <https://github.com/beeware/toga/issues/2017>`__)
+* The default system notification sound can be played via ``App.beep()``. (`#2018 <https://github.com/beeware/toga/issues/2018>`__)
+* DetailedList can now respond to "primary" and "secondary" user actions. These may be implemented as left and right swipe respectively, or using any other platform-appropriate mechanism. (`#2025 <https://github.com/beeware/toga/issues/2025>`__)
+* A DetailedList can now provide a value to use when a row doesn't provide the required data. (`#2025 <https://github.com/beeware/toga/issues/2025>`__)
+* The accessors used to populate a DetailedList can now be customized. (`#2025 <https://github.com/beeware/toga/issues/2025>`__)
+* Transformations can now be applied to *any* canvas context, not just the root context. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* Canvas now provides more ``list``-like methods for manipulating drawing objects in a context. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* On Windows, the default font now follows the system theme. On most devices, this means it has changed from Microsoft Sans Serif 8pt to Segoe UI 9pt. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* Font sizes are now consistently interpreted as CSS points. On Android, iOS and macOS, this means any numeric font sizes will appear 33% larger than before. The default font size on these platforms is unchanged. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* MultilineTextInputs no longer show spelling suggestions when in read-only mode. (`#2136 <https://github.com/beeware/toga/issues/2136>`__)
+* Applications now verify that a main window has been created as part of the ``startup()`` method. (`#2047 <https://github.com/beeware/toga/issues/2047>`__)
+* An implementation of ActivityIndicator was added to the Web backend. (`#2050 <https://github.com/beeware/toga/issues/2050>`__)
+* An implementation of Divider was added to the Web backend. (`#2051 <https://github.com/beeware/toga/issues/2051>`__)
+* The ability to capture the contents of a window as an image has been added. (`#2063 <https://github.com/beeware/toga/issues/2063>`__)
+* A PasswordInput widget was added to the Web backend. (`#2089 <https://github.com/beeware/toga/issues/2089>`__)
+* The WebKit inspector is automatically enabled on all macOS WebViews, provided you're using macOS 13.3 (Ventura) or iOS 16.4, or later. (`#2109 <https://github.com/beeware/toga/issues/2109>`__)
+* Text input widgets on macOS now support undo and redo. (`#2151 <https://github.com/beeware/toga/issues/2151>`__)
+* The Divider widget was implemented on Android. (`#2181 <https://github.com/beeware/toga/issues/2181>`__)
+
+Bugfixes
+--------
+
+* The WinForms event loop was decoupled from the main form, allowing background tasks to run without a main window being present. (`#750 <https://github.com/beeware/toga/issues/750>`__)
+* Widgets are now removed from windows when the window is closed, preventing a memory leak on window closure. (`#1215 <https://github.com/beeware/toga/issues/1215>`__)
+* Android and iOS apps no longer crash if you invoke ``App.hide_cursor()`` or ``App.show_cursor()``. (`#1235 <https://github.com/beeware/toga/issues/1235>`__)
+* A Selection widget with no items now consistently returns a selected value of ``None`` on all platforms. (`#1723 <https://github.com/beeware/toga/issues/1723>`__)
+* macOS widget methods that return strings are now guaranteed to return strings, rather than native Objective C string objects. (`#1779 <https://github.com/beeware/toga/issues/1779>`__)
+* WebViews on Windows no longer have a black background when they are resized. (`#1855 <https://github.com/beeware/toga/issues/1855>`__)
+* The interpretation of ``MultilineTextInput.readonly`` was corrected iOS (`#1866 <https://github.com/beeware/toga/issues/1866>`__)
+* A window without an ``on_close`` handler can now be closed using the window frame close button. (`#1872 <https://github.com/beeware/toga/issues/1872>`__)
+* Android apps running on devices older than API level 29 (Android 10) no longer crash. (`#1878 <https://github.com/beeware/toga/issues/1878>`__)
+* Missing value handling on Tables was fixed on Android and Linux. (`#1879 <https://github.com/beeware/toga/issues/1879>`__)
+* The GTK backend is now able to correctly identify the currently active window. (`#1892 <https://github.com/beeware/toga/issues/1892>`__)
+* Error handling associated with the creation of Intents on Android has been improved. (`#1909 <https://github.com/beeware/toga/issues/1909>`__)
+* The DetailedList widget on GTK now provides an accurate size hint during layout. (`#1920 <https://github.com/beeware/toga/issues/1920>`__)
+* Apps on Linux no longer segfault if an X Windows display cannot be identified. (`#1921 <https://github.com/beeware/toga/issues/1921>`__)
+* The ``on_result`` handler is now used by Cocoa file dialogs. (`#1947 <https://github.com/beeware/toga/issues/1947>`__)
+* Pack layout now honors an explicit width/height setting of 0. (`#1958 <https://github.com/beeware/toga/issues/1958>`__)
+* The minimum window size is now correctly recomputed and enforced if window content changes. (`#2020 <https://github.com/beeware/toga/issues/2020>`__)
+* The title of windows can now be modified on Winforms. (`#2094 <https://github.com/beeware/toga/issues/2094>`__)
+* An error on Winforms when a window has no content has been resolved. (`#2095 <https://github.com/beeware/toga/issues/2095>`__)
+* iOS container views are now set to automatically resize with their parent view (`#2161 <https://github.com/beeware/toga/issues/2161>`__)
+
+Backward Incompatible Changes
+-----------------------------
+
+* The ``weight``, ``style`` and ``variant`` arguments for ``Font`` and ``Font.register`` are now keyword-only. (`#1903 <https://github.com/beeware/toga/issues/1903>`__)
+* The ``clear()`` method for resetting the value of a MultilineTextInput, TextInput and PasswordInput has been removed. This method was an ambiguous override of the ``clear()`` method on Widget that removed all child nodes. To remove all content from a text input widget, use ``widget.value = ""``. (`#1938 <https://github.com/beeware/toga/issues/1938>`__)
+* The ability to perform multiple substring matches in a ``Contains`` validator has been removed. (`#1944 <https://github.com/beeware/toga/issues/1944>`__)
+* The ``TextInput.validate`` method has been removed. Validation now happens automatically whenever the ``value`` or ``validators`` properties are changed. (`#1944 <https://github.com/beeware/toga/issues/1944>`__)
+* The argument names used to construct validators have changed. Error message arguments now all end with ``_message``; ``compare_count`` has been renamed ``count``; and ``min_value`` and ``max_value`` have been renamed ``min_length`` and ``max_length``, respectively. (`#1944 <https://github.com/beeware/toga/issues/1944>`__)
+* The ``get_dom()`` method on WebView has been removed. This method wasn't implemented on most platforms, and wasn't working on any of the platforms where it *was* implemented, as modern web view implementations don't provide a synchronous API for accessing web content in this way. (`#1949 <https://github.com/beeware/toga/issues/1949>`__)
+* The ``evaluate_javascript()`` method on WebView has been modified to work in both synchronous and asynchronous contexts. In a synchronous context you can invoke the method and use a functional ``on_result`` callback to be notified when evaluation is complete. In an asynchronous context, you can await the result. (`#1949 <https://github.com/beeware/toga/issues/1949>`__)
+* The ``on_key_down`` handler has been removed from WebView. If you need to catch user input, either use a handler in the embedded JavaScript, or create a ``Command`` with a key shortcut. (`#1949 <https://github.com/beeware/toga/issues/1949>`__)
+* The ``invoke_javascript()`` method has been removed. All usage of ``invoke_javascript()`` can be replaced with ``evaluate_javascript()``. (`#1949 <https://github.com/beeware/toga/issues/1949>`__)
+* The usage of local ``file://`` URLs has been explicitly prohibited. ``file://`` URLs have not been reliable for some time; their usage is now explicitly prohibited. (`#1949 <https://github.com/beeware/toga/issues/1949>`__)
+* ``DatePicker`` has been renamed ``DateInput``. (`#1951 <https://github.com/beeware/toga/issues/1951>`__)
+* ``TimePicker`` has been renamed ``TimeInput``. (`#1951 <https://github.com/beeware/toga/issues/1951>`__)
+* The ``on_select`` handler on the Selection widget has been renamed ``on_change`` for consistency with other widgets. (`#1955 <https://github.com/beeware/toga/issues/1955>`__)
+* The ``_notify()`` method on data sources has been renamed ``notify()``, reflecting its status as a public API. (`#1955 <https://github.com/beeware/toga/issues/1955>`__)
+* The ``prepend()`` method was removed from the ``ListSource`` and ``TreeSource`` APIs. Calls to ``prepend(...)`` can be replaced with ``insert(0, ...)``. (`#1955 <https://github.com/beeware/toga/issues/1955>`__)
+* The ``insert()`` and ``append()`` APIs on ``ListSource`` and ``TreeSource`` have been modified to provide an interface that is closer to that ``list`` API. These methods previously accepted a variable list of positional and keyword arguments; these arguments should be combined into a single tuple or dictionary. This matches the API provided by ``__setitem__()``. (`#1955 <https://github.com/beeware/toga/issues/1955>`__)
+* Images and ImageViews no longer support loading images from URLs. If you need to display an image from a URL, use a background task to obtain the image data asynchronously, then create the Image and/or set the ImageView ``image`` property on the completion of the asynchronous load. (`#1956 <https://github.com/beeware/toga/issues/1956>`__)
+* A row box contained inside a row box will now expand to the full height of its parent, rather than collapsing to the maximum height of the inner box's child content. (`#1958 <https://github.com/beeware/toga/issues/1958>`__)
+* A column box contained inside a column box will now expand to the full width of its parent, rather than collapsing to the maximum width of the inner box's child content. (`#1958 <https://github.com/beeware/toga/issues/1958>`__)
+* On Android, the user data folder is now a ``data`` sub-directory of the location returned by ``context.getFilesDir()``, rather than the bare ``context.getFilesDir()`` location. (`#1964 <https://github.com/beeware/toga/issues/1964>`__)
+* GTK now returns ``~/.local/state/appname/log`` as the log file location, rather than ``~/.cache/appname/log``. (`#1964 <https://github.com/beeware/toga/issues/1964>`__)
+* The location returned by ``toga.App.paths.app`` is now the folder that contains the Python source file that defines the app class used by the app. If you are using a ``toga.App`` instance directly, this may alter the path that is returned. (`#1964 <https://github.com/beeware/toga/issues/1964>`__)
+* On Winforms, if an application doesn't define an author, an author of ``Unknown`` is now used in application data paths, rather than ``Toga``. (`#1964 <https://github.com/beeware/toga/issues/1964>`__)
+* Winforms now returns ``%USERPROFILE%/AppData/Local/<Author Name>/<App Name>/Data`` as the user data file location, rather than ``%USERPROFILE%/AppData/Local/<Author Name>/<App Name>``. (`#1964 <https://github.com/beeware/toga/issues/1964>`__)
+* Support for SplitContainers with more than 2 panels of content has been removed. (`#1984 <https://github.com/beeware/toga/issues/1984>`__)
+* Support for 3-tuple form of specifying SplitContainer items, used to prevent panels from resizing, has been removed. (`#1984 <https://github.com/beeware/toga/issues/1984>`__)
+* The ability to increment and decrement the current OptionContainer tab was removed. Instead of `container.current_tab += 1`, use `container.current_tab = container.current_tab.index + 1` (`#1996 <https://github.com/beeware/toga/issues/1996>`__)
+* ``OptionContainer.add()``, ``OptionContainer.remove()`` and ``OptionContainer.insert()`` have been removed, due to being ambiguous with base widget methods of the same name. Use the ``OptionContainer.content.append()``, ``OptionContainer.content.remove()`` and ``OptionContainer.content.insert()`` APIs instead. (`#1996 <https://github.com/beeware/toga/issues/1996>`__)
+* The ``on_select`` handler for OptionContainer no longer receives the ``option`` argument providing the selected tab. Use ``current_tab`` to obtain the currently selected tab. (`#1996 <https://github.com/beeware/toga/issues/1996>`__)
+* ``TimePicker.min_time`` and ``TimePicker.max_time`` has been renamed ``TimeInput.min`` and ``TimeInput.max``, respectively. (`#1999 <https://github.com/beeware/toga/issues/1999>`__)
+* ``DatePicker.min_date`` and ``DatePicker.max_date`` has been renamed ``DateInput.min`` and ``DateInput.max``, respectively. (`#1999 <https://github.com/beeware/toga/issues/1999>`__)
+* ``NumberInput.min_value`` and ``NumberInput.max_value`` have been renamed ``NumberInput.min`` and ``NumberInput.max``, respectively. (`#1999 <https://github.com/beeware/toga/issues/1999>`__)
+* ``Slider.range`` has been replaced by ``Slider.min`` and ``Slider.max``. (`#1999 <https://github.com/beeware/toga/issues/1999>`__)
+* Tables now use an empty string for the default missing value, rather than warning about missing values. (`#2011 <https://github.com/beeware/toga/issues/2011>`__)
+* ``Table.add_column()`` has been deprecated in favor of ``Table.append_column()`` and ``Table.insert_column()`` (`#2011 <https://github.com/beeware/toga/issues/2011>`__)
+* ``Table.on_double_click`` has been renamed ``Table.on_activate``. (`#2011 <https://github.com/beeware/toga/issues/2011>`__, `#2017 <https://github.com/beeware/toga/issues/2017>`__)
+* Trees now use an empty string for the default missing value, rather than warning about missing values. (`#2017 <https://github.com/beeware/toga/issues/2017>`__)
+* The ``parent`` argument has been removed from the ``insert`` and ``append`` calls on ``TreeSource``. This improves consistency between the API for ``TreeSource`` and the API for ``list``. To insert or append a row in to a descendant of a TreeSource root, use ``insert`` and ``append`` on the parent node itself - i.e., ``source.insert(parent, index, ...)`` becomes ``parent.insert(index, ...)``, and ``source.insert(None, index, ...)`` becomes ``source.insert(index, ...)``. (`#2017 <https://github.com/beeware/toga/issues/2017>`__)
+* When constructing a DetailedList from a list of tuples, or a list of lists, the required order of values has changed from (icon, title, subtitle) to (title, subtitle, icon). (`#2025 <https://github.com/beeware/toga/issues/2025>`__)
+* The ``on_select`` handler for DetailedList no longer receives the selected row as an argument. (`#2025 <https://github.com/beeware/toga/issues/2025>`__)
+* The handling of row deletion in DetailedList widgets has been significantly altered. The ``on_delete`` event handler has been renamed ``on_primary_action``, and is now *only* a notification that a "swipe left" event (or platform equivalent) has been confirmed. This was previously inconsistent across platforms. Some platforms would update the data source to remove the row; some treated ``on_delete`` as a notification event and expected the application to handle the deletion. It is now the application's responsibility to perform the data deletion. (`#2025 <https://github.com/beeware/toga/issues/2025>`__)
+* Support for Python 3.7 was removed. (`#2027 <https://github.com/beeware/toga/issues/2027>`__)
+* ``fill()`` and ``stroke()`` now return simple drawing operations, rather than context managers. If you attempt to use ``fill()`` or ``stroke()`` on a context as a context manager, an exception will be raised; using these methods on Canvas will raise a warning, but return the appropriate context manager. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* The ``clicks`` argument to ``Canvas.on_press`` has been removed. Instead, to detect "double clicks", you should use ``Canvas.on_activate``. The ``clicks`` argument has also been removed from ``Canvas.on_release``, ``Canvas.on_drag``, ``Canvas.on_alt_press``, ``Canvas.on_alt_release``, and ``Canvas.on_alt_drag``. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* The ``new_path`` operation has been renamed ``begin_path`` for consistency with the HTML5 Canvas API. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* Methods that generate new contexts have been renamed: ``context()``, ``closed_path()``, ``fill()`` and ``stroke()`` have become ``Context()``, ``ClosedPath()``, ``Fill()`` and ``Stroke()`` respectively. This has been done to make it easier to differentiate between primitive drawing operations and context-generating operations. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* A Canvas is no longer implicitly a context object. The ``Canvas.context`` property now returns the root context of the canvas. If you were previously using ``Canvas.context()`` to generate an empty context, it should be replaced with ``Canvas.Context()``. Any operations to ``remove()`` drawing objects from the canvas or ``clear()`` the canvas of drawing objects should be made on ``Canvas.context``. Invoking these methods on ``Canvas`` will now call the base ``Widget`` implementations, which will throw an exception because ``Canvas`` widgets cannot have children. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* The ``preserve`` option on ``Fill()`` operations has been deprecated. It was required for an internal optimization and can be safely removed without impact. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* Drawing operations (e.g., ``arc``, ``line_to``, etc) can no longer be invoked directly on a Canvas. Instead, they should be invoked on the root context of the canvas, retrieved with via the `canvas` property. Context creating operations (``Fill``, ``Stroke`` and ``ClosedPath``) are not affected. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* The ``tight`` argument to ``Canvas.measure_text()`` has been deprecated. It was a GTK implementation detail, and can be safely removed without impact. (`#2029 <https://github.com/beeware/toga/issues/2029>`__)
+* The ``multiselect`` argument to Open File and Select Folder dialogs has been renamed ``multiple_select``, for consistency with other widgets that have multiple selection capability. (`#2058 <https://github.com/beeware/toga/issues/2058>`__)
+* ``Window.resizeable`` and ``Window.closeable`` have been renamed ``Window.resizable`` and ``Window.closable``, to adhere to US spelling conventions. (`#2058 <https://github.com/beeware/toga/issues/2058>`__)
+* Windows no longer need to be explicitly added to the app's window list. When a window is created, it will be automatically added to the windows for the currently running app. (`#2058 <https://github.com/beeware/toga/issues/2058>`__)
+* The optional arguments of ``Command`` and ``Group`` are now keyword-only. (`#2075 <https://github.com/beeware/toga/issues/2075>`__)
+* In ``App``, the properties ``id`` and ``name`` have been deprecated in favor of ``app_id`` and ``formal_name`` respectively, and the property ``module_name`` has been removed. (`#2075 <https://github.com/beeware/toga/issues/2075>`__)
+* ``GROUP_BREAK``, ``SECTION_BREAK`` and ``CommandSet`` were removed from the ``toga`` namespace. End users generally shouldn't need to use these classes. If your code *does* need them for some reason, you can access them from the ``toga.command`` namespace. (`#2075 <https://github.com/beeware/toga/issues/2075>`__)
+* The ``windows`` constructor argument of ``toga.App`` has been removed. Windows are now automatically added to the current app. (`#2075 <https://github.com/beeware/toga/issues/2075>`__)
+* The ``filename`` argument and property of ``toga.Document`` has been renamed ``path``, and is now guaranteed to be a ``pathlib.Path`` object. (`#2075 <https://github.com/beeware/toga/issues/2075>`__)
+* Documents must now provide a ``create()`` method to instantiate a ``main_window`` instance. (`#2075 <https://github.com/beeware/toga/issues/2075>`__)
+* ``App.exit()`` now unconditionally exits the app, rather than confirming that the ``on_exit`` handler will permit the exit. (`#2075 <https://github.com/beeware/toga/issues/2075>`__)
+
+Documentation
+-------------
+
+* Documentation for application paths was added. (`#1849 <https://github.com/beeware/toga/issues/1849>`__)
+* The contribution guide was expanded to include more suggestions for potential projects, and to explain how the backend tests work. (`#1868 <https://github.com/beeware/toga/issues/1868>`__)
+* All code blocks were updated to add a button to copy the relevant contents on to the user's clipboard. (`#1897 <https://github.com/beeware/toga/issues/1897>`__)
+* Class references were updated to reflect their preferred import location, rather than location where they are defined in code. (`#2001 <https://github.com/beeware/toga/issues/2001>`__)
+* The Linux system dependencies were updated to reflect current requirements for developing and using Toga. (`#2021 <https://github.com/beeware/toga/issues/2021>`__)
+
+Misc
+----
+
+* `#1865 <https://github.com/beeware/toga/issues/1865>`__, `#1875 <https://github.com/beeware/toga/issues/1875>`__, `#1881 <https://github.com/beeware/toga/issues/1881>`__, `#1882 <https://github.com/beeware/toga/issues/1882>`__, `#1886 <https://github.com/beeware/toga/issues/1886>`__, `#1889 <https://github.com/beeware/toga/issues/1889>`__, `#1895 <https://github.com/beeware/toga/issues/1895>`__, `#1900 <https://github.com/beeware/toga/issues/1900>`__, `#1902 <https://github.com/beeware/toga/issues/1902>`__, `#1906 <https://github.com/beeware/toga/issues/1906>`__, `#1916 <https://github.com/beeware/toga/issues/1916>`__, `#1917 <https://github.com/beeware/toga/issues/1917>`__, `#1918 <https://github.com/beeware/toga/issues/1918>`__, `#1926 <https://github.com/beeware/toga/issues/1926>`__, `#1933 <https://github.com/beeware/toga/issues/1933>`__, `#1948 <https://github.com/beeware/toga/issues/1948>`__, `#1950 <https://github.com/beeware/toga/issues/1950>`__, `#1952 <https://github.com/beeware/toga/issues/1952>`__, `#1954 <https://github.com/beeware/toga/issues/1954>`__, `#1963 <https://github.com/beeware/toga/issues/1963>`__, `#1972 <https://github.com/beeware/toga/issues/1972>`__, `#1977 <https://github.com/beeware/toga/issues/1977>`__, `#1980 <https://github.com/beeware/toga/issues/1980>`__, `#1988 <https://github.com/beeware/toga/issues/1988>`__, `#1989 <https://github.com/beeware/toga/issues/1989>`__, `#1998 <https://github.com/beeware/toga/issues/1998>`__, `#2008 <https://github.com/beeware/toga/issues/2008>`__, `#2014 <https://github.com/beeware/toga/issues/2014>`__, `#2019 <https://github.com/beeware/toga/issues/2019>`__, `#2022 <https://github.com/beeware/toga/issues/2022>`__, `#2028 <https://github.com/beeware/toga/issues/2028>`__, `#2034 <https://github.com/beeware/toga/issues/2034>`__, `#2035 <https://github.com/beeware/toga/issues/2035>`__, `#2039 <https://github.com/beeware/toga/issues/2039>`__, `#2052 <https://github.com/beeware/toga/issues/2052>`__, `#2053 <https://github.com/beeware/toga/issues/2053>`__, `#2055 <https://github.com/beeware/toga/issues/2055>`__, `#2056 <https://github.com/beeware/toga/issues/2056>`__, `#2057 <https://github.com/beeware/toga/issues/2057>`__, `#2059 <https://github.com/beeware/toga/issues/2059>`__, `#2067 <https://github.com/beeware/toga/issues/2067>`__, `#2068 <https://github.com/beeware/toga/issues/2068>`__, `#2069 <https://github.com/beeware/toga/issues/2069>`__, `#2085 <https://github.com/beeware/toga/issues/2085>`__, `#2090 <https://github.com/beeware/toga/issues/2090>`__, `#2092 <https://github.com/beeware/toga/issues/2092>`__, `#2093 <https://github.com/beeware/toga/issues/2093>`__, `#2101 <https://github.com/beeware/toga/issues/2101>`__, `#2102 <https://github.com/beeware/toga/issues/2102>`__, `#2113 <https://github.com/beeware/toga/issues/2113>`__, `#2114 <https://github.com/beeware/toga/issues/2114>`__, `#2115 <https://github.com/beeware/toga/issues/2115>`__, `#2116 <https://github.com/beeware/toga/issues/2116>`__, `#2118 <https://github.com/beeware/toga/issues/2118>`__, `#2119 <https://github.com/beeware/toga/issues/2119>`__, `#2123 <https://github.com/beeware/toga/issues/2123>`__, `#2124 <https://github.com/beeware/toga/issues/2124>`__, `#2127 <https://github.com/beeware/toga/issues/2127>`__, `#2128 <https://github.com/beeware/toga/issues/2128>`__, `#2131 <https://github.com/beeware/toga/issues/2131>`__, `#2132 <https://github.com/beeware/toga/issues/2132>`__, `#2146 <https://github.com/beeware/toga/issues/2146>`__, `#2147 <https://github.com/beeware/toga/issues/2147>`__, `#2148 <https://github.com/beeware/toga/issues/2148>`__, `#2149 <https://github.com/beeware/toga/issues/2149>`__, `#2150 <https://github.com/beeware/toga/issues/2150>`__, `#2163 <https://github.com/beeware/toga/issues/2163>`__, `#2165 <https://github.com/beeware/toga/issues/2165>`__, `#2166 <https://github.com/beeware/toga/issues/2166>`__, `#2171 <https://github.com/beeware/toga/issues/2171>`__, `#2177 <https://github.com/beeware/toga/issues/2177>`__, `#2180 <https://github.com/beeware/toga/issues/2180>`__, `#2184 <https://github.com/beeware/toga/issues/2184>`__, `#2186 <https://github.com/beeware/toga/issues/2186>`__
+
 0.3.1 (2023-04-12)
 ==================
 
diff --git a/docs/background/topics/commands.rst b/docs/background/topics/commands.rst
deleted file mode 100644
index f2c79d95f0..0000000000
--- a/docs/background/topics/commands.rst
+++ /dev/null
@@ -1,111 +0,0 @@
-.. _commands:
-
-============================
-Commands, Menus and Toolbars
-============================
-
-A GUI requires more than just widgets laid out in a user interface - you'll
-also want to allow the user to actually *do* something. In Toga, you do this
-using ``Commands``.
-
-A command encapsulates a piece of functionality that the user can invoke - no
-matter how they invoke it. It doesn't matter if they select a menu item,
-press a button on a toolbar, or use a key combination - the functionality is
-wrapped up in a Command.
-
-When a command is added to an application, Toga takes control of ensuring that
-the command is exposed to the user in a way that they can access it. On desktop
-platforms, this may result in a command being added to a menu.
-
-You can also choose to add a command (or commands) to a toolbar on a specific
-window.
-
-Defining Commands
-~~~~~~~~~~~~~~~~~
-
-When you specify a ``Command``, you provide some additional metadata to help
-classify and organize the commands in your application:
-
-* An **action** - a function to invoke when the command is activated.
-
-* A **label** - a name for the command to.
-
-* A **tooltip** - a short description of what the command will do
-
-* A **shortcut** - (optional) A key combination that can be used to invoke the command.
-
-* An **icon** - (optional) A path to an icon resource to decorate the command.
-
-* A **group** - (optional) a ``Group`` object describing a collection of similar commands. If no group is specified, a default "Command" group will be used.
-
-* A **section** - (optional) an integer providing a sub-grouping. If no section is specified, the command will be allocated to section 0 within the group.
-
-* An **order** - (optional) an integer indicating where a command falls within a section. If a ``Command`` doesn't have an order, it will be sorted alphabetically by label within its section.
-
-Commands may not use all the metadata - for example, on some platforms, menus
-will contain icons; on other platforms they won't. Toga will use the metadata
-if it is provided, but ignore it (or substitute an appropriate default) if it
-isn't.
-
-Commands can be enabled and disabled; if you disable a command, it will
-automatically disable any toolbar or menu item where the command appears.
-
-Groups
-~~~~~~
-
-Toga provides a number of ready-to-use groups:
-
-* ``Group.APP`` - Application level control
-* ``Group.FILE`` - File commands
-* ``Group.EDIT`` - Editing commands
-* ``Group.VIEW`` - Commands to alter the appearance of content
-* ``Group.COMMANDS`` - A Default
-* ``Group.WINDOW`` - Commands for managing different windows in the app
-* ``Group.HELP`` - Help content
-
-You can also define custom groups.
-
-Example
-~~~~~~~
-
-The following is an example of using menus and commands::
-
-    import toga
-
-    def callback(sender):
-        print("Command activated")
-
-    def build(app):
-        ...
-        stuff_group = Group('Stuff', order=40)
-
-        cmd1 = toga.Command(
-            callback,
-            label='Example command',
-            tooltip='Tells you when it has been activated',
-            shortcut='k',
-            icon='icons/pretty.png',
-            group=stuff_group,
-            section=0
-        )
-        cmd2 = toga.Command(
-            ...
-        )
-        ...
-
-        app.commands.add(cmd1, cmd4, cmd3)
-        app.main_window.toolbar.add(cmd2, cmd3)
-
-This code defines a command ``cmd1`` that will be placed in the first section of
-the "Stuff" group. It can be activated by pressing CTRL-k (or CMD-K on a Mac).
-
-The definitions for ``cmd2``, ``cmd3``, and ``cmd4`` have been omitted, but would
-follow a similar pattern.
-
-It doesn't matter what order you add commands to the app - the group, section
-and order will be used to put the commands in the right order.
-
-If a command is added to a toolbar, it will automatically be added to the app
-as well. It isn't possible to have functionality exposed on a toolbar that
-isn't also exposed by the app. So, ``cmd2`` will be added to the app, even though
-it wasn't explicitly added to the app commands.
diff --git a/docs/background/topics/index.rst b/docs/background/topics/index.rst
index 31c750910b..389681b01a 100644
--- a/docs/background/topics/index.rst
+++ b/docs/background/topics/index.rst
@@ -6,5 +6,4 @@ Topic guides
    :maxdepth: 1
 
    layout
-   commands
    data-sources
diff --git a/docs/conf.py b/docs/conf.py
index 2969e977d0..b2764bb273 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -111,8 +111,11 @@
 rst_prolog = """
 .. role:: stable
 .. role:: beta
+.. role:: no
 .. |y| replace:: :stable:`●`
 .. |b| replace:: :beta:`○`
+.. |beta| replace:: :beta:`β`
+.. |no| replace:: :no:`✖︎`
 """
 
 intersphinx_mapping = {"python": ("https://docs.python.org/3", None)}
@@ -147,8 +150,13 @@ def autodoc_process_signature(
 
 # -- Options for link checking -------------------------------------------------
 
-# GitHub generates anchors in javascript
-linkcheck_ignore = [r"https://github.com/.*#"]
+linkcheck_ignore = [
+    # GitHub generates anchors in javascript
+    r"https://github.com/.*#",
+    # References to Github issues/pulls should all be safe.
+    r"^https://github.com/beeware/toga/issues/\d+$",
+    r"^https://github.com/beeware/toga/pull/\d+$",
+]
 
 # -- Options for copy button ---------------------------------------------------
 
diff --git a/docs/how-to/contribute-code.rst b/docs/how-to/contribute-code.rst
index 5006e2d697..c1a3d7f1e2 100644
--- a/docs/how-to/contribute-code.rst
+++ b/docs/how-to/contribute-code.rst
@@ -356,25 +356,6 @@ What should I do?
 Depending on your level of expertise, or areas of interest, there are a number
 of ways you can contribute to Toga's code.
 
-Improve test coverage for the core API
---------------------------------------
-
-If this is your first time contributing, this is probably the easiest place to
-start.
-
-Toga has a test suite that verifies that the public API behaves as expected.
-This API is tested against a "dummy" backend - a backend that implements the
-same API as the platform backends (e.g., ``toga-cocoa`` and ``toga-winforms``),
-but without relying on any specific platform graphical behavior. The dummy
-backend mocks the behavior of a real backend, and provides additional properties
-to verify when various actions have been performed on the backend.
-
-We want to get our core API 100% coverage, but we're not there yet - and you can
-help! Your task: create a test that improves coverage - even by one more line.
-
-Details on how to run the test suite and check coverage :ref:`can be found below
-<run-core-test-suite>`.
-
 Fix a bug in an existing widget
 -------------------------------
 
@@ -408,17 +389,16 @@ information provided by the reporter, and trying to reproduce it. Again, if you
 can't reproduce the problem, report what you have found as a comment on the
 ticket, and pick another ticket.
 
-If you can reproduce the problem - try to fix it! Work out what combination of
-core and backend-specific code is implementing the feature, and see if you can
-work out what isn't working correctly. You may need to refer to platform
-specific documentation (e.g., the `Cocoa AppKit
-<https://developer.apple.com/documentation/appkit?language=objc>`__, `iOS UIKit
-<https://developer.apple.com/documentation/uikit?language=objc>`__, `GTK
+If you can reproduce the problem - try to fix it! Work out what combination of core and
+backend-specific code is implementing the feature, and see if you can work out what
+isn't working correctly. You may need to refer to platform specific documentation (e.g.,
+the `Cocoa AppKit <https://developer.apple.com/documentation/appkit?language=objc>`__,
+`iOS UIKit <https://developer.apple.com/documentation/uikit?language=objc>`__, `GTK
 <https://docs.gtk.org/gtk3/>`__, `Winforms
 <https://learn.microsoft.com/en-us/dotnet/desktop/winforms/controls/overview?view=netdesktop-7.0>`__,
-`Android <https://developer.android.com/reference>`__ or `Shoelace
-<https://shoelace.style>`__ API documentation) to work out why a widget isn't
-behaving as expected.
+`Android <https://developer.android.com/reference>`__, `Shoelace
+<https://shoelace.style>`__ or `Textual <https://textual.textualize.io>`__ API
+documentation) to work out why a widget isn't behaving as expected.
 
 If you're able to fix the problem, you'll need to add tests for :ref:`the core
 API <run-core-test-suite>` and/or :ref:`the testbed backend <run-testbed>` for
@@ -431,27 +411,6 @@ the fix, that knowledge will often be enough for someone who knows more about a
 platform to solve the problem. Even a good reproduction case (a sample app that
 does nothing but reproduce the problem) can be a huge help.
 
-Convert from ``unittest`` to pytest
------------------------------------
-
-Toga's test suite was historically written using Python's builtin ``unittest``
-library. We're currently porting these old tests to pytest. Pick a widget that
-has ``unittest``-based tests, and port those tests over to pytest format. As you
-do this, make sure the test makes good use of pytest features (like fixtures and
-parameterization). The tests that have been already been ported to pytest are a
-good reference for what a good Toga pytest looks like.
-
-Improve test coverage for a backend API
----------------------------------------
-
-If you've got expertise in a particular platform (for example, if you've got
-experience writing iOS apps), or you'd *like* to have that experience, you might
-want to look into writing tests for a platform backend. We want to get to 100%
-coverage for all the backend APIs, but we're a long way from that goal.
-
-The platform backends are tested using a testbed app. Details on how to run the
-testbed app for a given platform :ref:`can be found below <run-testbed>`.
-
 Contribute improvements to documentation
 ----------------------------------------
 
@@ -463,19 +422,21 @@ on.
 Implement a platform native widget
 ----------------------------------
 
-If the core library already specifies an interface for a widget, but the widget
-isn't implemented on your platform of choice, implement that interface. The
-:doc:`supported widgets by platform </reference/widgets_by_platform>` table can
-show you the widgets that are missing on various platforms. You can also look
-for log messages in a running app (or the direct ``factory.not_implemented()``
-function calls that produce those log messages). At present, the web backend
-has a lot of missing widgets, so if you have web skills, or would like to learn
-more about `PyScript <https://pyscript.net>`__ and `Shoelace
-<https://shoelace.style>`__, this could be a good place to contribute.
+If the core library already specifies an interface for a widget, but the widget isn't
+implemented on your platform of choice, implement that interface. The :doc:`supported
+widgets by platform </reference/widgets_by_platform>` table can show you the widgets
+that are missing on various platforms. You can also look for log messages in a running
+app (or the direct ``factory.not_implemented()`` function calls that produce those log
+messages). At present, the Web and Textual backends have the most missing widgets. If
+you have web skills, or would like to learn more about `PyScript
+<https://pyscript.net>`__ and `Shoelace <https://shoelace.style>`__, the web backend
+could be a good place to contribute; if you'd like to learn more about terminal
+applications and the or `Textual <https://textual.textualize.io>`__ API, contributing to
+the Textual backend could be a good place for you to contribute.
 
 Alternatively, if there's a widget that doesn't exist, propose an interface
 design, and implement it for at least one platform. You may find `this
-presentation by BeeWare team member Dan Yeaw
+presentation by BeeWare emeritus team member Dan Yeaw
 <https://www.youtube.com/watch?v=sWt_sEZUiY8>`__ helpful. This talk gives an
 architectural overview of Toga, as well as providing a guide to the process of
 adding new widgets.
@@ -499,11 +460,10 @@ you add.
 Implement an entirely new platform backend
 ------------------------------------------
 
-Toga currently has support for 6 backends - but there's room for more! In
+Toga currently has support for 7 backends - but there's room for more! In
 particular, we'd be interested in seeing a `Qt-based backend
 <https://github.com/beeware/toga/issues/1142>`__ to support KDE-based Linux
-desktops, and a `Textual-based console backend
-<https://github.com/beeware/toga/issues/1867>`__.
+desktops.
 
 The first steps of any new platform backend are always the same:
 
@@ -550,19 +510,19 @@ To run the core test suite:
 
     .. code-block:: console
 
-      (venv) $ tox -e py-core
+      (venv) $ tox -e py
 
   .. group-tab:: Linux
 
     .. code-block:: console
 
-      (venv) $ tox -e py-core
+      (venv) $ tox -e py
 
   .. group-tab:: Windows
 
     .. code-block:: doscon
 
-      (venv) C:\...>tox -e py-core
+      (venv) C:\...>tox -e py
 
 You should get some output indicating that tests have been run. You may see
 ``SKIPPED`` tests, but shouldn't ever get any ``FAIL`` or ``ERROR`` test
@@ -571,51 +531,31 @@ discovers any problems, we don't merge the patch. If you do find a test error or
 failure, either there's something odd in your test environment, or you've found
 an edge case that we haven't seen before - either way, let us know!
 
-Although the tests should all pass, the test suite itself is still incomplete.
-There are many aspects of the Toga Core API that aren't currently tested (or
-aren't tested thoroughly). To work out what *isn't* tested, Toga uses a tool
-called `coverage <https://coverage.readthedocs.io/en/latest>`__. Coverage allows
-you to check which lines of code have (and haven't) been executed - which then
-gives you an idea of what code has (and hasn't) been tested.
-
 At the end of the test output there should be a report of the coverage data that
 was gathered::
 
-      Name                                 Stmts   Miss  Cover   Missing
-      ------------------------------------------------------------------
-      toga/__init__.py                        29      0   100%
-      toga/app.py                             50      0   100%
-      ...
-      toga/window.py                          79     18    77%   58, 75, 87, 92, 104, 141, 155, 164, 168, 172-173, 176, 192, 204, 216, 228, 243, 257
-      ------------------------------------------------------------------
-      TOTAL                                 1034    258    75%
-
-What does this all mean? Well, the "Cover" column tells you what proportion of
-lines in a given file were executed during the test run. In this run, every
-line of ``toga/app.py`` was executed; but only 77% of lines in
-``toga/window.py`` were executed. Which lines were missed? They're listed in
-the next column: lines 58, 75, 87, and so on weren't executed.
-
-Ideally, every single line in every single file will have 100% coverage. If you
-look in `core/tests`, you should find a test file that matches the name of the
-file that has insufficient coverage. If you don't, it's possible the entire test
-file is missing - so you'll have to create it!
-
-Once you've written a test, re-run the test suite to generate fresh coverage
-data. Let's say we added a test for line 58 of ``toga/window.py`` - we'd
-expect to see something like::
-
-      Name                                 Stmts   Miss  Cover   Missing
-      ------------------------------------------------------------------
-      toga/__init__.py                        29      0   100%
-      toga/app.py                             50      0   100%
-      ...
-      toga/window.py                          79     17    78%   75, 87, 92, 104, 141, 155, 164, 168, 172-173, 176, 192, 204, 216, 228, 243, 257
-      ------------------------------------------------------------------
-      TOTAL                                 1034    257    75%
-
-That is, one more test has been executed, resulting in one less missing line
-in the coverage results.
+    Name    Stmts   Miss Branch BrPart   Cover   Missing
+    ----------------------------------------------------
+    TOTAL    4345      0   1040      0  100.0%
+
+This tells us that the test suite has executed every possible branching path
+in the ``toga-core`` library. This isn't a 100% guarantee that there are no bugs,
+but it does mean that we're exercising every line of code in the core API.
+
+If you make changes to the core API, it's possible you'll introduce a gap in this
+coverage. When this happens, the coverage report will tell you which lines aren't
+being executed. For example, lets say we made a change to ``toga/window.py``,
+adding some new logic. The coverage report might look something like::
+
+  Name                 Stmts   Miss Branch BrPart  Cover   Missing
+  ----------------------------------------------------------------
+  src/toga/window.py     186      2     22      2  98.1%   211, 238-240
+  ----------------------------------------------------------------
+  TOTAL                 4345      2   1040      2  99.9%
+
+This tells us that line 211, and lines 238-240 are not being executed by the test
+suite. You'll need to add new tests (or modify an existing test) to restore this
+coverage.
 
 When you're developing your new test, it may be helpful to run *just* that one
 test. To do this, you can pass in the name of a specific test file (or a
@@ -628,19 +568,19 @@ specific test, using `pytest specifiers
 
     .. code-block:: console
 
-      (venv) $ tox -e py-core -- tests/path_to_test_file/test_some_test.py
+      (venv) $ tox -e py -- tests/path_to_test_file/test_some_test.py
 
   .. group-tab:: Linux
 
     .. code-block:: console
 
-      (venv) $ tox -e py-core -- tests/path_to_test_file/test_some_test.py
+      (venv) $ tox -e py -- tests/path_to_test_file/test_some_test.py
 
   .. group-tab:: Windows
 
     .. code-block:: doscon
 
-      (venv) C:\...>tox -e py-core -- tests/path_to_test_file/test_some_test.py
+      (venv) C:\...>tox -e py -- tests/path_to_test_file/test_some_test.py
 
 These test paths are relative to the ``core`` directory. You'll still get a
 coverage report when running a part of the test suite - but the coverage results
@@ -836,6 +776,8 @@ result, the Cocoa implementation of the ``color`` `property of the Button probe
 <https://github.com/beeware/toga/blob/main/cocoa/tests_backend/widgets/button.py#L17>`__
 performs an ``xfail`` describing that limitation.
 
+.. _pr-housekeeping:
+
 Submitting a pull request
 =========================
 
diff --git a/docs/how-to/contribute-docs.rst b/docs/how-to/contribute-docs.rst
index 755818c42a..1654c5df5d 100644
--- a/docs/how-to/contribute-docs.rst
+++ b/docs/how-to/contribute-docs.rst
@@ -174,3 +174,10 @@ However, you don't need to be constrained by these tickets. If you can identify
 a gap in Toga's documentation, or an improvement that can be made, start
 writing! Anything that improves the experience of the end user is a welcome
 change.
+
+Submitting a pull request
+=========================
+
+Before you submit a pull request, there's a few bits of housekeeping to do. See the
+section on submitting a pull request in the :ref:`code contribution guide
+<pr-housekeeping>` for details on our submission process.
diff --git a/docs/how-to/internal/release.rst b/docs/how-to/internal/release.rst
index 77e0ba5294..6a718ed566 100644
--- a/docs/how-to/internal/release.rst
+++ b/docs/how-to/internal/release.rst
@@ -37,7 +37,16 @@ The procedure for cutting a new release is as follows:
 
      $ tox -e towncrier
 
-   to generate the updated release notes.
+   to generate the updated release notes. After doing any edits that may be
+   required, run:
+
+   .. code-block:: console
+
+     $ tox -r -e docs-lint,docs
+
+   to confirm that there are no spelling errors or formatting problems with the
+   new release notes, and the docs build using the current documentation tool
+   versions.
 
 #. Tag the release, and push the branch and tag upstream:
 
@@ -68,8 +77,16 @@ The procedure for cutting a new release is as follows:
       code change, delete the old tag, make the code change, and re-tag the
       release.
 
-#. Download the "packages" artifact from the GitHub workflow, and use its wheels
-   to build some apps and perform any pre-release testing that may be appropriate.
+#. Create a clean virtual environment, install the new release from Test PyPI, and
+   perform any pre-release testing that may be appropriate:
+
+   .. code-block:: console
+
+     $ python3 -m venv testvenv
+     $ . ./testvenv/bin/activate
+     (testvenv) $ pip install --extra-index-url https://test.pypi.org/simple/ toga==1.2.3
+     (testvenv) $ toga-demo
+     (testvenv) $ #... any other manual checks you want to perform ...
 
 #. Log into ReadTheDocs, visit the `Versions tab
    <https://readthedocs.org/projects/toga/versions/>`__, and activate the
diff --git a/docs/images/toga-demo-cocoa.png b/docs/images/toga-demo-cocoa.png
new file mode 100644
index 0000000000..684c7c20d3
Binary files /dev/null and b/docs/images/toga-demo-cocoa.png differ
diff --git a/docs/images/toga-demo-gtk.png b/docs/images/toga-demo-gtk.png
new file mode 100644
index 0000000000..16d0c6cade
Binary files /dev/null and b/docs/images/toga-demo-gtk.png differ
diff --git a/docs/images/toga-demo-winforms.png b/docs/images/toga-demo-winforms.png
new file mode 100644
index 0000000000..663fbd0902
Binary files /dev/null and b/docs/images/toga-demo-winforms.png differ
diff --git a/docs/index.rst b/docs/index.rst
index 92c7c3f0c7..c6b38bf7af 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -9,9 +9,25 @@ development.
 Toga is available on macOS, Windows, Linux (GTK), Android, iOS, and for
 single-page web apps.
 
-.. figure:: tutorial/screenshots/tutorial-2.png
-    :align: center
-    :width: 500
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /images/toga-demo-cocoa.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Linux
+
+    .. figure:: /images/toga-demo-gtk.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Windows
+
+    .. figure:: /images/toga-demo-winforms.png
+       :align: center
+       :width: 450px
 
 
 .. rst-class::  row
diff --git a/docs/reference/api/app.rst b/docs/reference/api/app.rst
index 087cadeb3d..d0c097a974 100644
--- a/docs/reference/api/app.rst
+++ b/docs/reference/api/app.rst
@@ -1,5 +1,7 @@
-Application
-===========
+App
+===
+
+The top-level representation of an application.
 
 .. rst-class:: widget-support
 .. csv-filter:: Availability (:ref:`Key <api-status-key>`)
@@ -8,53 +10,71 @@ Application
    :included_cols: 4,5,6,7,8,9,10
    :exclude: {0: '(?!(Application|Component))'}
 
-The app is the main entry point and container for the Toga GUI.
 
 Usage
 -----
 
-The app class is used by instantiating with a name, namespace and callback to a startup delegate which takes 1 argument of the app instance.
+The App class is the top level representation of all application activity. It is a
+singleton object - any given process can only have a single App. That
+application may manage multiple windows, but it is guaranteed to have at least one
+window (called the :attr:`~toga.App.main_window`); when the App's
+:attr:`~toga.App.main_window` is closed, the application will exit.
 
-To start a UI loop, call ``app.main_loop()``
+The application is started by calling :meth:`~toga.App.main_loop()`. This will invoke
+the :meth:`~toga.App.startup()` method of the app.
 
 .. code-block:: python
 
     import toga
 
+    app = toga.App("Simplest App", "com.example.simplest")
+    app.main_loop()
 
-    def build(app):
-        # build UI
-        pass
+You can populate an app's main window by passing a callable as the ``startup`` argument
+to the :class:`toga.App` constructor. This ``startup`` method must return the content
+that will be added to the main window of the app.
 
+.. code-block:: python
 
-    if __name__ == '__main__':
-        app = toga.App('First App', 'org.beeware.helloworld', startup=build)
-        app.main_loop()
+    import toga
 
-Alternatively, you can subclass App and implement the startup method
+    def create_content(app):
+        return toga.Box(children=[toga.Label("Hello!")])
+
+    app = toga.App("Simple App", "com.example.simple", startup=create_content)
+    app.main_loop()
+
+This approach to app construction is most useful with simple apps. For most complex
+apps, you should subclass :class:`toga.App`, and provide an implementation of
+:meth:`~toga.App.startup()`. This implementation *must* create and assign a
+``main_window`` for the app.
 
 .. code-block:: python
 
     import toga
 
-
     class MyApp(toga.App):
         def startup(self):
-            # build UI
-            pass
-
+            self.main_window = toga.MainWindow()
+            self.main_window.content = toga.Box(children=[toga.Label("Hello!")])
+            self.main_window.show()
 
     if __name__ == '__main__':
-        app = MyApp('First App', 'org.beeware.helloworld')
+        app = MyApp("Realistic App", "org.beeware.realistic")
         app.main_loop()
 
-All App instances must have assigned their :attr:`~toga.App.main_window` before the
-conclusion of their :meth:`~toga.App.startup` method.
+Every app must have a formal name (a human readable name), and an app ID (a
+machine-readable identifier - usually a reversed domain name). In the examples above,
+these are provided as constructor arguments. However, you can also provide these
+details, along with many of the other constructor arguments, as packaging metadata in a
+format compatible with :any:`importlib.metadata`. If you deploy your app with `Briefcase
+<https://briefcase.readthedocs.io/en/stable>`__, this will be done automatically.
 
 Reference
 ---------
 
 .. autoclass:: toga.App
+    :exclude-members: app
 
 .. autoprotocol:: toga.app.AppStartupMethod
 .. autoprotocol:: toga.app.BackgroundTask
diff --git a/docs/reference/api/containers/optioncontainer.rst b/docs/reference/api/containers/optioncontainer.rst
index cdb019484f..5db89609ac 100644
--- a/docs/reference/api/containers/optioncontainer.rst
+++ b/docs/reference/api/containers/optioncontainer.rst
@@ -3,17 +3,41 @@ OptionContainer
 
 A container that can display multiple labeled tabs of content.
 
-.. figure:: /reference/images/OptionContainer.png
-    :align: center
-    :width: 300px
+.. tabs::
 
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(OptionContainer|Component))'}
+  .. group-tab:: macOS
 
+    .. figure:: /reference/images/optioncontainer-cocoa.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/optioncontainer-gtk.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/optioncontainer-winforms.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Android |no|
+
+    Not supported
+
+  .. group-tab:: iOS |no|
+
+    Not supported
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/containers/scrollcontainer.rst b/docs/reference/api/containers/scrollcontainer.rst
index f43c9dfc3a..cb068354f1 100644
--- a/docs/reference/api/containers/scrollcontainer.rst
+++ b/docs/reference/api/containers/scrollcontainer.rst
@@ -4,16 +4,45 @@ ScrollContainer
 A container that can display a layout larger than the area of the container, with
 overflow controlled by scroll bars.
 
-.. figure:: /reference/images/ScrollContainer.png
-   :align: center
-   :width: 300px
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(ScrollContainer|Component))'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/scrollcontainer-cocoa.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/scrollcontainer-gtk.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/scrollcontainer-winforms.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/scrollcontainer-android.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/scrollcontainer-iOS.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/containers/splitcontainer.rst b/docs/reference/api/containers/splitcontainer.rst
index 53777f397a..48c0ea8e13 100644
--- a/docs/reference/api/containers/splitcontainer.rst
+++ b/docs/reference/api/containers/splitcontainer.rst
@@ -3,17 +3,41 @@ SplitContainer
 
 A container that divides an area into two panels with a movable border.
 
-.. figure:: /reference/images/SplitContainer.png
-   :align: center
-   :width: 300px
+.. tabs::
 
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(SplitContainer|Component))'}
+  .. group-tab:: macOS
 
+    .. figure:: /reference/images/splitcontainer-cocoa.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/splitcontainer-gtk.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/splitcontainer-winforms.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Android |no|
+
+    Not supported
+
+  .. group-tab:: iOS |no|
+
+    Not supported
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/documentapp.rst b/docs/reference/api/documentapp.rst
new file mode 100644
index 0000000000..88a96fe724
--- /dev/null
+++ b/docs/reference/api/documentapp.rst
@@ -0,0 +1,90 @@
+DocumentApp
+===========
+
+The top-level representation of an application that manages documents.
+
+.. rst-class:: widget-support
+.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
+   :header-rows: 1
+   :file: ../data/widgets_by_platform.csv
+   :included_cols: 4,5,6,7,8,9,10
+   :exclude: {0: '(?!(DocumentApp|Component))'}
+
+
+Usage
+-----
+
+A DocumentApp is a specialized subclass of App that is used to manage documents. A
+DocumentApp does *not* have a main window; each document that the app manages has it's
+own main window. Each document may also define additional windows, if necessary.
+
+The types of documents that the DocumentApp can manage must be declared as part of the
+instantiation of the DocumentApp. This requires that you define a subclass of
+:class:`toga.Document` that describes how your document can be read and displayed. In
+this example, the code declares an "Example Document" document type, whose files have an
+extension of ``mydoc``:
+
+.. code-block:: python
+
+    import toga
+
+    class ExampleDocument(toga.Document):
+        def __init__(self, path, app):
+            super().__init__(document_type="Example Document", path=path, app=app)
+
+        def create(self):
+            # Create the representation for the document's main window
+            self.main_window = toga.DocumentMainWindow(self)
+            self.main_window.content = toga.MultilineTextInput()
+
+        def read(self):
+            # Put your logic to read the document here. For example:
+            with self.path.open() as f:
+                self.content = f.read()
+
+            self.main_window.content.value = self.content
+
+    app = toga.DocumentApp("Document App", "com.example.document", {"mydoc": MyDocument})
+    app.main_loop()
+
+The exact behavior of a DocumentApp is slightly different on each platform, reflecting
+platform differences.
+
+macOS
+~~~~~
+
+On macOS, there is only ever a single instance of a DocumentApp running at any given
+time. That instance can manage multiple documents. If you use the Finder to open a
+second document of a type managed by the DocumentApp, it will be opened in the existing
+DocumentApp instance. Closing all documents will not cause the app to exit; the app will
+keep executing until explicitly exited.
+
+If the DocumentApp is started without an explicit file reference, a file dialog will be
+displayed prompting the user to select a file to open. If this dialog can be dismissed,
+the app will continue running. Selecting "Open" from the file menu will also display this
+dialog; if a file is selected, a new document window will be opened.
+
+Linux/Windows
+~~~~~~~~~~~~~
+
+On Linux and Windows, each DocumentApp instance manages a single document. If your app
+is running, and you use the file manager to open a second document, a second instance of
+the app will be started. If you close a document's main window, the app instance
+associated with that document will exit, but any other app instances will keep running.
+
+If the DocumentApp is started without an explicit file reference, a file dialog will be
+displayed prompting the user to select a file to open. If this dialog is dismissed, the
+app will continue running, but will show an empty document. Selecting "Open" from the
+file menu will also display this dialog; if a file is selected, the current document
+will be replaced.
+
+Reference
+---------
+
+.. autoclass:: toga.DocumentApp
+   :members:
+   :undoc-members:
+
+.. autoclass:: toga.Document
+   :members:
+   :undoc-members:
diff --git a/docs/reference/api/index.rst b/docs/reference/api/index.rst
index 2d20fcc2c8..3b46b6e653 100644
--- a/docs/reference/api/index.rst
+++ b/docs/reference/api/index.rst
@@ -7,13 +7,14 @@ API Reference
 Core application components
 ---------------------------
 
-=============================================== ===================================================
- Component                                       Description
-=============================================== ===================================================
- :doc:`Application </reference/api/app>`         The application itself
- :doc:`Window </reference/api/window>`           An operating system-managed container of widgets.
- :doc:`MainWindow </reference/api/mainwindow>`   The main window of the application.
-=============================================== ===================================================
+================================================= ===================================================
+ Component                                         Description
+================================================= ===================================================
+ :doc:`App </reference/api/app>`                   The top-level representation of an application.
+ :doc:`DocumentApp </reference/api/documentapp>`   An application that manages documents.
+ :doc:`Window </reference/api/window>`             An operating system-managed container of widgets.
+ :doc:`MainWindow </reference/api/mainwindow>`     The main window of the application.
+================================================= ===================================================
 
 General widgets
 ---------------
@@ -76,9 +77,9 @@ Resources
 ==================================================================== ========================================================================
  :doc:`App Paths </reference/api/resources/app_paths>`                A mechanism for obtaining platform-appropriate file system locations
                                                                       for an application.
- :doc:`Command </reference/api/resources/command>`                    Command
+ :doc:`Command </reference/api/resources/command>`                    A representation of app functionality that the user can invoke from
+                                                                      menus or toolbars.
  :doc:`Font </reference/api/resources/fonts>`                         Fonts
- :doc:`Group </reference/api/resources/group>`                        Command group
  :doc:`Icon </reference/api/resources/icons>`                         An icon for buttons, menus, etc
  :doc:`Image </reference/api/resources/images>`                       An image
  :doc:`ListSource </reference/api/resources/sources/list_source>`     A data source describing an ordered list of data.
@@ -95,15 +96,18 @@ Other
  Component                                      Description
 ============================================== ========================================================================
  :doc:`Constants </reference/api/constants>`    Symbolic constants used by various APIs.
+ :doc:`Keys </reference/api/keys>`              Symbolic representation of keys used for keyboard shortcuts.
 ============================================== ========================================================================
 
 .. toctree::
    :hidden:
 
    app
-   mainwindow
+   documentapp
    window
+   mainwindow
    containers/index
    resources/index
    widgets/index
    constants
+   keys
diff --git a/docs/reference/api/keys.rst b/docs/reference/api/keys.rst
new file mode 100644
index 0000000000..31e1f175a4
--- /dev/null
+++ b/docs/reference/api/keys.rst
@@ -0,0 +1,41 @@
+Keys
+====
+
+A symbolic representation of keys used for keyboard shortcuts.
+
+Most keys have a constant that matches the text on the key, or the name of the
+key if the text on the key isn't a legal Python identifier.
+
+However, due to differences between platforms, there's no representation of
+"modifier" keys like Control, Command, Option, or the Windows Key. Instead, Toga
+provides three generic modifier constants, and maps those to the modifier keys,
+matching the precedence with which they are used on the underlying platforms:
+
+========== ============== ============== ==================
+ Platform   :any:`MOD_1`   :any:`MOD_2`   :any:`MOD_3`
+========== ============== ============== ==================
+ Linux      Control        Alt            Tux/Windows/Meta
+ macOS      Command (⌘)    Option         Control (^)
+ Windows    Control        Alt            Not supported
+========== ============== ============== ==================
+
+Key combinations can be expressed by combining multiple ``Key`` values with the
+``+`` operator.
+
+.. code-block:: python
+
+    from toga import Key
+
+    just_an_a = Key.A
+    shift_a = Key.SHIFT + Key.A
+    # Windows/Linux - Control-Shift-A:
+    # macOS - Command-Shift-A:
+    modified_shift_a = Key.MOD_1 + Key.SHIFT + Key.A
+
+The order of addition is not significant. ``Key.SHIFT + Key.A`` and ``Key.A +
+Key.SHIFT`` will produce the same key representation.
+
+Reference
+---------
+
+.. autoclass:: toga.Key
diff --git a/docs/reference/api/mainwindow.rst b/docs/reference/api/mainwindow.rst
index 57e9deb1ef..7dc17936d7 100644
--- a/docs/reference/api/mainwindow.rst
+++ b/docs/reference/api/mainwindow.rst
@@ -3,16 +3,53 @@ MainWindow
 
 The main window of the application.
 
-.. figure:: /reference/images/MainWindow.png
-   :align: center
-   :width: 300px
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(MainWindow|Component))'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/mainwindow-cocoa.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/mainwindow-gtk.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/mainwindow-winforms.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/mainwindow-android.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/mainwindow-iOS.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Web |beta|
+
+    .. .. figure:: /reference/images/mainwindow-web.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
+
+  .. group-tab:: Textual |beta|
+
+    .. .. figure:: /reference/images/mainwindow-textual.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
 
 Usage
 -----
diff --git a/docs/reference/api/resources/app_paths.rst b/docs/reference/api/resources/app_paths.rst
index e4b174a59d..12fa3e48d0 100644
--- a/docs/reference/api/resources/app_paths.rst
+++ b/docs/reference/api/resources/app_paths.rst
@@ -25,7 +25,7 @@ cases, hard restrictions) over where certain file types should be stored. For
 example, macOS provides the ``~/Library/Application Support`` folder; Linux
 encourages use of the ``~/.config`` folder (amongst others), and Windows
 provides the ``AppData/Local`` folder in the user's home directory. Application
-sandbox and security policies will prevent sometimes prevent reading or
+sandbox and security policies will sometimes prevent reading or
 writing files in any location other than these pre-approved locations.
 
 To assist with finding an appropriate location to store application files, every
diff --git a/docs/reference/api/resources/command.rst b/docs/reference/api/resources/command.rst
index ed58049084..9eb805f59e 100644
--- a/docs/reference/api/resources/command.rst
+++ b/docs/reference/api/resources/command.rst
@@ -1,6 +1,8 @@
 Command
 =======
 
+A representation of app functionality that the user can invoke from menus or toolbars.
+
 .. rst-class:: widget-support
 .. csv-filter:: Availability (:ref:`Key <api-status-key>`)
    :header-rows: 1
@@ -12,7 +14,73 @@ Command
 Usage
 -----
 
+Aside from event handlers on widgets, most GUI toolkits also provide other ways for
+the user to give instructions to an app. In Toga, these UI patterns are supported
+by the :class:`~toga.Command` class.
+
+A command encapsulates a piece of functionality that the user can invoke - no matter how
+they invoke it. It doesn't matter if they select a menu item, press a button on a
+toolbar, or use a key combination - the functionality is wrapped up in a Command.
+
+Commands are added to an app using the properties :any:`toga.App.commands` and
+:any:`toga.Window.toolbar`. Toga then takes control of ensuring that the
+command is exposed to the user in a way that they can access. On desktop platforms,
+this may result in a command being added to a menu.
+
+Commands can be organized into a :class:`~toga.Group` of similar commands. Groups are
+hierarchical, so a group can contain a sub-group, which can contain a sub-group, and so
+on. Inside a group, commands can be organized into sections.
+
+For example:
+
+.. code-block:: python
+
+    import toga
+
+    def callback(sender, **kwargs):
+        print("Command activated")
+
+    stuff_group = Group('Stuff', order=40)
+
+    cmd1 = toga.Command(
+        callback,
+        label='Example command',
+        tooltip='Tells you when it has been activated',
+        shortcut=toga.Key.MOD_1 + 'k',
+        icon='icons/pretty.png',
+        group=stuff_group,
+        section=0
+    )
+    cmd2 = toga.Command(
+        ...
+    )
+    ...
+
+    app.commands.add(cmd1, cmd4, cmd3)
+    app.main_window.toolbar.add(cmd2, cmd3)
+
+This code defines a command ``cmd1`` that will be placed in the first section of the
+"Stuff" group. It can be activated by pressing CTRL-k (or CMD-K on a Mac).
+
+The definitions for ``cmd2``, ``cmd3``, and ``cmd4`` have been omitted, but would follow
+a similar pattern.
+
+It doesn't matter what order you add commands to the app - the group, section and order
+will be used to display the commands in the right order.
+
+If a command is added to a toolbar, it will automatically be added to the app
+as well. It isn't possible to have functionality exposed on a toolbar that
+isn't also exposed by the app. So, ``cmd2`` will be added to the app, even though
+it wasn't explicitly added to the app commands.
+
+
 Reference
 ---------
 
 .. autoclass:: toga.Command
+    :exclude-members: key
+
+.. autoclass:: toga.Group
+    :exclude-members: key
+
+.. autoprotocol:: toga.command.ActionHandler
diff --git a/docs/reference/api/resources/group.rst b/docs/reference/api/resources/group.rst
deleted file mode 100644
index 8f1354846c..0000000000
--- a/docs/reference/api/resources/group.rst
+++ /dev/null
@@ -1,19 +0,0 @@
-Group
-=====
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(Group|Component))'}
-
-
-
-Usage
------
-
-Reference
----------
-
-.. autoclass:: toga.Group
diff --git a/docs/reference/api/resources/index.rst b/docs/reference/api/resources/index.rst
index 7f2d6e94d1..0544de2680 100644
--- a/docs/reference/api/resources/index.rst
+++ b/docs/reference/api/resources/index.rst
@@ -6,7 +6,6 @@ Resources
    app_paths
    fonts
    command
-   group
    icons
    images
    sources/source
diff --git a/docs/reference/api/widgets/activityindicator.rst b/docs/reference/api/widgets/activityindicator.rst
index 168bc99625..0a19d4be23 100644
--- a/docs/reference/api/widgets/activityindicator.rst
+++ b/docs/reference/api/widgets/activityindicator.rst
@@ -4,15 +4,43 @@ ActivityIndicator
 A small animated indicator showing activity on a task of indeterminate length,
 usually rendered as a "spinner" animation.
 
-.. figure:: /reference/images/ActivityIndicator.jpeg
-    :align: center
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(ActivityIndicator|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/activityindicator-cocoa.png
+       :align: center
+       :width: 100px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/activityindicator-gtk.png
+       :align: center
+       :width: 100px
+
+  .. group-tab:: Windows |no|
+
+    Not supported
+
+  .. group-tab:: Android |no|
+
+    Not supported
+
+  .. group-tab:: iOS |no|
+
+    Not supported
+
+  .. group-tab:: Web |beta|
+
+    .. .. figure:: /reference/images/activityindicator-web.png
+    ..    :align: center
+    ..    :width: 100px
+
+    Screenshot not available
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/button.rst b/docs/reference/api/widgets/button.rst
index 2f6b3118ae..cb588d43ea 100644
--- a/docs/reference/api/widgets/button.rst
+++ b/docs/reference/api/widgets/button.rst
@@ -3,16 +3,53 @@ Button
 
 A button that can be pressed or clicked.
 
-.. figure:: /reference/images/Button.jpeg
-    :align: center
-    :width: 300
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(Button|Component))'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/button-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/button-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/button-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/button-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/button-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |beta|
+
+    .. .. figure:: /reference/images/button-web.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
+
+  .. group-tab:: Textual |beta|
+
+    .. .. figure:: /reference/images/button-textual.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/canvas.rst b/docs/reference/api/widgets/canvas.rst
index 2cc384edd8..8f184520da 100644
--- a/docs/reference/api/widgets/canvas.rst
+++ b/docs/reference/api/widgets/canvas.rst
@@ -3,16 +3,45 @@ Canvas
 
 A drawing area for 2D vector graphics.
 
-.. figure:: /reference/images/Canvas.png
-    :align: center
-    :width: 300
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(Canvas|Component))'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/canvas-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/canvas-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/canvas-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/canvas-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/canvas-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/dateinput.rst b/docs/reference/api/widgets/dateinput.rst
index 670a889e1f..2854869094 100644
--- a/docs/reference/api/widgets/dateinput.rst
+++ b/docs/reference/api/widgets/dateinput.rst
@@ -3,16 +3,39 @@ DateInput
 
 A widget to select a calendar date.
 
-.. figure:: /reference/images/DateInput.png
-    :align: center
-    :width: 300
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(DateInput|Component))'}
+.. tabs::
+
+  .. group-tab:: macOS |no|
+
+    Not supported
+
+  .. group-tab:: Linux |no|
+
+    Not supported
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/dateinput-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/dateinput-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS |no|
+
+    Not supported
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/detailedlist.rst b/docs/reference/api/widgets/detailedlist.rst
index 9ba0e20be6..f679552281 100644
--- a/docs/reference/api/widgets/detailedlist.rst
+++ b/docs/reference/api/widgets/detailedlist.rst
@@ -1,19 +1,46 @@
 DetailedList
 ============
 
-An ordered list where each item has an icon, a title, and a line of text. Scroll bars
-will be provided if necessary.
-
-.. figure:: /reference/images/DetailedList.png
-   :width: 300px
-   :align: center
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(DetailedList|Component))'}
+
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/detailedlist-cocoa.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/detailedlist-gtk.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Windows |beta|
+
+    .. figure:: /reference/images/detailedlist-winforms.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/detailedlist-android.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/detailedlist-iOS.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/divider.rst b/docs/reference/api/widgets/divider.rst
index c5d34a3db1..d2a8fa9a8b 100644
--- a/docs/reference/api/widgets/divider.rst
+++ b/docs/reference/api/widgets/divider.rst
@@ -3,15 +3,47 @@ Divider
 
 A separator used to visually distinguish two sections of content in a layout.
 
-.. figure:: /reference/images/Divider.jpeg
-    :align: center
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(Divider|Component))'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/divider-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/divider-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/divider-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/divider-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS |no|
+
+    Not supported
+
+  .. group-tab:: Web |beta|
+
+    .. .. figure:: /reference/images/divider-web.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/imageview.rst b/docs/reference/api/widgets/imageview.rst
index 7ff4cd1bdd..90f9a0da47 100644
--- a/docs/reference/api/widgets/imageview.rst
+++ b/docs/reference/api/widgets/imageview.rst
@@ -1,15 +1,48 @@
 ImageView
 =========
 
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(ImageView|Component)$)'}
-
 A widget that displays an image.
 
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/imageview.png
+       :align: center
+       :width: 150px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/imageview.png
+       :align: center
+       :width: 150px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/imageview.png
+       :align: center
+       :width: 150px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/imageview.png
+       :align: center
+       :width: 150px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/imageview.png
+       :align: center
+       :width: 150px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
+
 Usage
 -----
 
diff --git a/docs/reference/api/widgets/label.rst b/docs/reference/api/widgets/label.rst
index a0f1bc1591..cfc5119e0c 100644
--- a/docs/reference/api/widgets/label.rst
+++ b/docs/reference/api/widgets/label.rst
@@ -3,15 +3,53 @@ Label
 
 A text label for annotating forms or interfaces.
 
-.. figure:: /reference/images/Label.jpeg
-    :align: center
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(Label|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/label-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/label-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/label-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/label-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/label-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |beta|
+
+    .. .. figure:: /reference/images/label-web.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
+
+  .. group-tab:: Textual |beta|
+
+    .. .. figure:: /reference/images/label-textual.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/multilinetextinput.rst b/docs/reference/api/widgets/multilinetextinput.rst
index 8dbf204692..35fbe4f176 100644
--- a/docs/reference/api/widgets/multilinetextinput.rst
+++ b/docs/reference/api/widgets/multilinetextinput.rst
@@ -3,16 +3,45 @@ MultilineTextInput
 
 A scrollable panel that allows for the display and editing of multiple lines of text.
 
-.. figure:: /reference/images/MultilineTextInput.png
-   :align: center
-   :width: 300
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(MultilineTextInput|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/multilinetextinput-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/multilinetextinput-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/multilinetextinput-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/multilinetextinput-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/multilinetextinput-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/numberinput.rst b/docs/reference/api/widgets/numberinput.rst
index bb05f5cac2..68bde9474d 100644
--- a/docs/reference/api/widgets/numberinput.rst
+++ b/docs/reference/api/widgets/numberinput.rst
@@ -3,15 +3,45 @@ NumberInput
 
 A text input that is limited to numeric input.
 
-.. figure:: /reference/images/NumberInput.png
-    :align: center
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(NumberInput|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/numberinput-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/numberinput-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/numberinput-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/numberinput-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/numberinput-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/passwordinput.rst b/docs/reference/api/widgets/passwordinput.rst
index 0f59d097f3..6ecfc810d9 100644
--- a/docs/reference/api/widgets/passwordinput.rst
+++ b/docs/reference/api/widgets/passwordinput.rst
@@ -5,17 +5,45 @@ A widget to allow the entry of a password. Any value typed by the user will be
 obscured, allowing the user to see the number of characters they have typed, but
 not the actual characters.
 
-.. figure:: /reference/images/PasswordInput.png
-   :align: center
-   :width: 300
+.. tabs::
 
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(PasswordInput|Component)$)'}
+  .. group-tab:: macOS
 
+    .. figure:: /reference/images/passwordinput-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/passwordinput-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/passwordinput-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/passwordinput-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/passwordinput-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/progressbar.rst b/docs/reference/api/widgets/progressbar.rst
index 3530362d61..91185a747f 100644
--- a/docs/reference/api/widgets/progressbar.rst
+++ b/docs/reference/api/widgets/progressbar.rst
@@ -4,15 +4,49 @@ ProgressBar
 A horizontal bar to visualize task progress. The task being monitored can be of
 known or indeterminate length.
 
-.. figure:: /reference/images/ProgressBar.jpeg
-    :align: center
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(ProgressBar|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/progressbar-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/progressbar-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/progressbar-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/progressbar-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/progressbar-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |beta|
+
+    .. .. figure:: /reference/images/progressbar-web.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/selection.rst b/docs/reference/api/widgets/selection.rst
index 6063d59cb8..d0ba61a19a 100644
--- a/docs/reference/api/widgets/selection.rst
+++ b/docs/reference/api/widgets/selection.rst
@@ -3,16 +3,45 @@ Selection
 
 A widget to select a single option from a list of alternatives.
 
-.. figure:: /reference/images/Selection.png
-    :align: center
+.. tabs::
 
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(Selection|Component)$)'}
+  .. group-tab:: macOS
 
+    .. figure:: /reference/images/selection-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/selection-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/selection-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/selection-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/selection-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/slider.rst b/docs/reference/api/widgets/slider.rst
index c698d017b4..a2569d5bdb 100644
--- a/docs/reference/api/widgets/slider.rst
+++ b/docs/reference/api/widgets/slider.rst
@@ -4,16 +4,45 @@ Slider
 A widget for selecting a value within a range. The range is shown as a horizontal line,
 and the selected value is shown as a draggable marker.
 
-.. figure:: /reference/images/Slider.png
-    :align: center
-    :width: 300
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(Slider|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/slider-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/slider-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/slider-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/slider-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/slider-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 
 Usage
diff --git a/docs/reference/api/widgets/switch.rst b/docs/reference/api/widgets/switch.rst
index 81d1599242..d4081b9141 100644
--- a/docs/reference/api/widgets/switch.rst
+++ b/docs/reference/api/widgets/switch.rst
@@ -4,16 +4,49 @@ Switch
 A clickable button with two stable states: True (on, checked); and False (off,
 unchecked). The button has a text label.
 
-.. figure:: /reference/images/Switch.jpeg
-    :align: center
-    :width: 300
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(Switch|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/switch-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/switch-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/switch-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/switch-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/switch-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |beta|
+
+    .. .. figure:: /reference/images/switch-web.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/table.rst b/docs/reference/api/widgets/table.rst
index a2b67c2615..5257fc0e9c 100644
--- a/docs/reference/api/widgets/table.rst
+++ b/docs/reference/api/widgets/table.rst
@@ -4,16 +4,43 @@ Table
 A widget for displaying columns of tabular data. Scroll bars will be provided if
 necessary.
 
-.. figure:: /reference/images/Table.png
-   :width: 300px
-   :align: center
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(Table|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/table-cocoa.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/table-gtk.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/table-winforms.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Android |beta|
+
+    .. figure:: /reference/images/table-android.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: iOS |no|
+
+    Not supported
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/textinput.rst b/docs/reference/api/widgets/textinput.rst
index ee1d6f4da4..dfed425639 100644
--- a/docs/reference/api/widgets/textinput.rst
+++ b/docs/reference/api/widgets/textinput.rst
@@ -3,16 +3,53 @@ TextInput
 
 A widget for the display and editing of a single line of text.
 
-.. figure:: /reference/images/TextInput.png
-   :align: center
-   :width: 300
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(TextInput|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/textinput-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/textinput-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/textinput-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/textinput-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/textinput-iOS.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Web |beta|
+
+    .. .. figure:: /reference/images/textinput-web.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
+
+  .. group-tab:: Textual |beta|
+
+    .. .. figure:: /reference/images/textinput-textual.png
+    ..    :align: center
+    ..    :width: 300px
+
+    Screenshot not available
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/timeinput.rst b/docs/reference/api/widgets/timeinput.rst
index 381b4e28c1..c6d8527b72 100644
--- a/docs/reference/api/widgets/timeinput.rst
+++ b/docs/reference/api/widgets/timeinput.rst
@@ -3,16 +3,39 @@ TimeInput
 
 A widget to select a clock time.
 
-.. figure:: /reference/images/TimeInput.png
-    :align: center
-    :width: 160
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(TimeInput|Component))'}
+.. tabs::
+
+  .. group-tab:: macOS |no|
+
+    Not supported
+
+  .. group-tab:: Linux |no|
+
+    Not supported
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/timeinput-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/timeinput-android.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: iOS |no|
+
+    Not supported
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/tree.rst b/docs/reference/api/widgets/tree.rst
index 07a1da4318..9bb05f5706 100644
--- a/docs/reference/api/widgets/tree.rst
+++ b/docs/reference/api/widgets/tree.rst
@@ -4,16 +4,39 @@ Tree
 A widget for displaying a hierarchical tree of tabular data. Scroll bars will be
 provided if necessary.
 
-.. figure:: /reference/images/Tree.png
-   :width: 300px
-   :align: center
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(Tree|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/tree-cocoa.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/tree-gtk.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Windows |no|
+
+    Not supported
+
+  .. group-tab:: Android |no|
+
+    Not supported
+
+  .. group-tab:: iOS |no|
+
+    Not supported
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/widgets/webview.rst b/docs/reference/api/widgets/webview.rst
index 9068d912ba..6fbcf2c2a6 100644
--- a/docs/reference/api/widgets/webview.rst
+++ b/docs/reference/api/widgets/webview.rst
@@ -3,15 +3,45 @@ WebView
 
 An embedded web browser.
 
-.. figure:: /reference/images/WebView.jpeg
-    :align: center
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!^(WebView|Component)$)'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/webview-cocoa.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/webview-gtk.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/webview-winforms.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Android
+
+    .. figure:: /reference/images/webview-android.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: iOS
+
+    .. figure:: /reference/images/webview-iOS.png
+       :align: center
+       :width: 450px
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/api/window.rst b/docs/reference/api/window.rst
index f622a9cd5f..f0730f0968 100644
--- a/docs/reference/api/window.rst
+++ b/docs/reference/api/window.rst
@@ -3,16 +3,41 @@ Window
 
 An operating system-managed container of widgets.
 
-.. figure:: /reference/images/Window.png
-   :align: center
-   :width: 300px
-
-.. rst-class:: widget-support
-.. csv-filter:: Availability (:ref:`Key <api-status-key>`)
-   :header-rows: 1
-   :file: ../data/widgets_by_platform.csv
-   :included_cols: 4,5,6,7,8,9,10
-   :exclude: {0: '(?!(Window|Component))'}
+.. tabs::
+
+  .. group-tab:: macOS
+
+    .. figure:: /reference/images/window-cocoa.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Linux
+
+    .. figure:: /reference/images/window-gtk.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Windows
+
+    .. figure:: /reference/images/window-winforms.png
+       :align: center
+       :width: 300px
+
+  .. group-tab:: Android |no|
+
+    Not supported
+
+  .. group-tab:: iOS |no|
+
+    Not supported
+
+  .. group-tab:: Web |no|
+
+    Not supported
+
+  .. group-tab:: Textual |no|
+
+    Not supported
 
 Usage
 -----
diff --git a/docs/reference/data/widgets_by_platform.csv b/docs/reference/data/widgets_by_platform.csv
index ca5d10cadf..d671c8fa57 100644
--- a/docs/reference/data/widgets_by_platform.csv
+++ b/docs/reference/data/widgets_by_platform.csv
@@ -1,13 +1,14 @@
 Component,Type,Component,Description,macOS,GTK,Windows,iOS,Android,Web,Terminal
-Application,Core Component,:class:`~toga.App`,The application itself,|b|,|b|,|b|,|b|,|b|,|b|,|b|
-Window,Core Component,:class:`~toga.Window`,An operating system-managed container of widgets.,|y|,|y|,|y|,|y|,|y|,|b|,|b|
+Application,Core Component,:class:`~toga.App`,The application itself,|y|,|y|,|y|,|y|,|y|,|b|,|b|
+DocumentApp,Core Component,:class:`~toga.DocumentApp`,An application that manages documents.,|b|,|b|,,,,,
+Window,Core Component,:class:`~toga.Window`,An operating system-managed container of widgets.,|y|,|y|,|y|,,,,
 MainWindow,Core Component,:class:`~toga.MainWindow`,The main window of the application.,|y|,|y|,|y|,|y|,|y|,|b|,|b|
 ActivityIndicator,General Widget,:class:`~toga.ActivityIndicator`,A spinning activity animation,|y|,|y|,,,,|b|,
 Button,General Widget,:class:`~toga.Button`,Basic clickable Button,|y|,|y|,|y|,|y|,|y|,|b|,|b|
 Canvas,General Widget,:class:`~toga.Canvas`,A drawing area for 2D vector graphics.,|y|,|y|,|y|,|y|,|y|,,
 DateInput,General Widget,:class:`~toga.DateInput`,A widget to select a calendar date,,,|y|,,|y|,|b|,
 DetailedList,General Widget,:class:`~toga.DetailedList`,"An ordered list of content where each item has an icon, a main heading, and a line of supplementary text.",|y|,|y|,|b|,|y|,|y|,,
-Divider,General Widget,:class:`~toga.Divider`,A horizontal or vertical line,|y|,|y|,|y|,,,|b|,
+Divider,General Widget,:class:`~toga.Divider`,A horizontal or vertical line,|y|,|y|,|y|,,|y|,|b|,
 ImageView,General Widget,:class:`~toga.ImageView`,A widget that displays an image,|y|,|y|,|y|,|y|,|y|,,
 Label,General Widget,:class:`~toga.Label`,Text label,|y|,|y|,|y|,|y|,|y|,|b|,|b|
 MultilineTextInput,General Widget,:class:`~toga.MultilineTextInput`,Multi-line Text Input field,|y|,|y|,|y|,|y|,|y|,,
@@ -29,7 +30,6 @@ SplitContainer,Layout Widget,:class:`~toga.SplitContainer`,A container that divi
 OptionContainer,Layout Widget,:class:`~toga.OptionContainer`,A container that can display multiple labeled tabs of content,|y|,|y|,|y|,,,,
 App Paths,Resource,:class:`~toga.paths.Paths`,A mechanism for obtaining platform-appropriate filesystem locations for an application.,|y|,|y|,|y|,|y|,|y|,,|b|
 Font,Resource,:class:`~toga.Font`,A text font,|y|,|y|,|y|,|y|,|y|,,
-Command,Resource,:class:`~toga.Command`,Command,|b|,|b|,|b|,,|b|,,
-Group,Resource,:class:`~toga.Group`,Command group,|b|,|b|,|b|,|b|,|b|,,
+Command,Resource,:class:`~toga.Command`,Command,|y|,|y|,|y|,,|y|,,
 Icon,Resource,:class:`~toga.Icon`,"A small, square image, used to provide easily identifiable visual context to a widget.",|y|,|y|,|y|,|y|,|y|,,|b|
 Image,Resource,:class:`~toga.Image`,An image,|y|,|y|,|y|,|y|,|y|,,
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index 0000000000..b97105bc79
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diff --git a/docs/reference/images/progressbar-gtk.png b/docs/reference/images/progressbar-gtk.png
new file mode 100644
index 0000000000..43a404746c
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diff --git a/docs/reference/images/progressbar-iOS.png b/docs/reference/images/progressbar-iOS.png
new file mode 100644
index 0000000000..40cdc6c96c
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diff --git a/docs/reference/images/progressbar-winforms.png b/docs/reference/images/progressbar-winforms.png
new file mode 100644
index 0000000000..98c3f8ad6e
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diff --git a/docs/reference/images/scrollcontainer-android.png b/docs/reference/images/scrollcontainer-android.png
new file mode 100644
index 0000000000..115318b02d
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diff --git a/docs/reference/images/scrollcontainer-cocoa.png b/docs/reference/images/scrollcontainer-cocoa.png
new file mode 100644
index 0000000000..c0210b90b9
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diff --git a/docs/reference/images/scrollcontainer-gtk.png b/docs/reference/images/scrollcontainer-gtk.png
new file mode 100644
index 0000000000..1767fbc81d
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diff --git a/docs/reference/images/scrollcontainer-iOS.png b/docs/reference/images/scrollcontainer-iOS.png
new file mode 100644
index 0000000000..4a82d02934
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diff --git a/docs/reference/images/scrollcontainer-winforms.png b/docs/reference/images/scrollcontainer-winforms.png
new file mode 100644
index 0000000000..11d624207b
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diff --git a/docs/reference/images/selection-android.png b/docs/reference/images/selection-android.png
new file mode 100644
index 0000000000..05f6697946
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diff --git a/docs/reference/images/selection-cocoa.png b/docs/reference/images/selection-cocoa.png
new file mode 100644
index 0000000000..a21abf65ec
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diff --git a/docs/reference/images/selection-gtk.png b/docs/reference/images/selection-gtk.png
new file mode 100644
index 0000000000..97b7ae6b86
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diff --git a/docs/reference/images/selection-iOS.png b/docs/reference/images/selection-iOS.png
new file mode 100644
index 0000000000..eaf2df9cdf
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diff --git a/docs/reference/images/selection-winforms.png b/docs/reference/images/selection-winforms.png
new file mode 100644
index 0000000000..b8b1920b30
Binary files /dev/null and b/docs/reference/images/selection-winforms.png differ
diff --git a/docs/reference/images/slider-android.png b/docs/reference/images/slider-android.png
new file mode 100644
index 0000000000..076a1e48e8
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diff --git a/docs/reference/images/slider-cocoa.png b/docs/reference/images/slider-cocoa.png
new file mode 100644
index 0000000000..c488720619
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diff --git a/docs/reference/images/slider-gtk.png b/docs/reference/images/slider-gtk.png
new file mode 100644
index 0000000000..1d5cc06e87
Binary files /dev/null and b/docs/reference/images/slider-gtk.png differ
diff --git a/docs/reference/images/slider-iOS.png b/docs/reference/images/slider-iOS.png
new file mode 100644
index 0000000000..92d9695a8a
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diff --git a/docs/reference/images/slider-winforms.png b/docs/reference/images/slider-winforms.png
new file mode 100644
index 0000000000..74c30ef4d4
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diff --git a/docs/reference/images/splitcontainer-cocoa.png b/docs/reference/images/splitcontainer-cocoa.png
new file mode 100644
index 0000000000..bfcdd31698
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diff --git a/docs/reference/images/splitcontainer-gtk.png b/docs/reference/images/splitcontainer-gtk.png
new file mode 100644
index 0000000000..860591adf2
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diff --git a/docs/reference/images/splitcontainer-winforms.png b/docs/reference/images/splitcontainer-winforms.png
new file mode 100644
index 0000000000..9f49315412
Binary files /dev/null and b/docs/reference/images/splitcontainer-winforms.png differ
diff --git a/docs/reference/images/switch-android.png b/docs/reference/images/switch-android.png
new file mode 100644
index 0000000000..9c88e2aea5
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diff --git a/docs/reference/images/switch-cocoa.png b/docs/reference/images/switch-cocoa.png
new file mode 100644
index 0000000000..c2de515a5f
Binary files /dev/null and b/docs/reference/images/switch-cocoa.png differ
diff --git a/docs/reference/images/switch-gtk.png b/docs/reference/images/switch-gtk.png
new file mode 100644
index 0000000000..ef679a893c
Binary files /dev/null and b/docs/reference/images/switch-gtk.png differ
diff --git a/docs/reference/images/switch-iOS.png b/docs/reference/images/switch-iOS.png
new file mode 100644
index 0000000000..11215ece8f
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diff --git a/docs/reference/images/switch-winforms.png b/docs/reference/images/switch-winforms.png
new file mode 100644
index 0000000000..f719732185
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diff --git a/docs/reference/images/table-android.png b/docs/reference/images/table-android.png
new file mode 100644
index 0000000000..fa7dfa1146
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diff --git a/docs/reference/images/table-cocoa.png b/docs/reference/images/table-cocoa.png
new file mode 100644
index 0000000000..4beca508b9
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diff --git a/docs/reference/images/table-gtk.png b/docs/reference/images/table-gtk.png
new file mode 100644
index 0000000000..9e50d0d8e6
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diff --git a/docs/reference/images/table-winforms.png b/docs/reference/images/table-winforms.png
new file mode 100644
index 0000000000..a95c81f500
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diff --git a/docs/reference/images/textinput-android.png b/docs/reference/images/textinput-android.png
new file mode 100644
index 0000000000..42e1e4d01e
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diff --git a/docs/reference/images/textinput-cocoa.png b/docs/reference/images/textinput-cocoa.png
new file mode 100644
index 0000000000..574fb03106
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diff --git a/docs/reference/images/textinput-gtk.png b/docs/reference/images/textinput-gtk.png
new file mode 100644
index 0000000000..b7235d677e
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diff --git a/docs/reference/images/textinput-iOS.png b/docs/reference/images/textinput-iOS.png
new file mode 100644
index 0000000000..4607f0b726
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diff --git a/docs/reference/images/textinput-winforms.png b/docs/reference/images/textinput-winforms.png
new file mode 100644
index 0000000000..4bdf2d0f53
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diff --git a/docs/reference/images/timeinput-android.png b/docs/reference/images/timeinput-android.png
new file mode 100644
index 0000000000..c2f4a62f1b
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diff --git a/docs/reference/images/timeinput-winforms.png b/docs/reference/images/timeinput-winforms.png
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index 0000000000..b1e5ffd725
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diff --git a/docs/reference/images/tree-cocoa.png b/docs/reference/images/tree-cocoa.png
new file mode 100644
index 0000000000..40867d6bff
Binary files /dev/null and b/docs/reference/images/tree-cocoa.png differ
diff --git a/docs/reference/images/tree-gtk.png b/docs/reference/images/tree-gtk.png
new file mode 100644
index 0000000000..ab4ac5ab7c
Binary files /dev/null and b/docs/reference/images/tree-gtk.png differ
diff --git a/docs/reference/images/webview-android.png b/docs/reference/images/webview-android.png
new file mode 100644
index 0000000000..72f1c7a4d8
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diff --git a/docs/reference/images/webview-cocoa.png b/docs/reference/images/webview-cocoa.png
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index 0000000000..9578bad12f
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diff --git a/docs/reference/images/webview-gtk.png b/docs/reference/images/webview-gtk.png
new file mode 100644
index 0000000000..0f24ca06d8
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diff --git a/docs/reference/images/webview-iOS.png b/docs/reference/images/webview-iOS.png
new file mode 100644
index 0000000000..454fc4d412
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diff --git a/docs/reference/images/webview-winforms.png b/docs/reference/images/webview-winforms.png
new file mode 100644
index 0000000000..1338e00bd4
Binary files /dev/null and b/docs/reference/images/webview-winforms.png differ
diff --git a/docs/reference/images/window-cocoa.png b/docs/reference/images/window-cocoa.png
new file mode 100644
index 0000000000..0435b80e91
Binary files /dev/null and b/docs/reference/images/window-cocoa.png differ
diff --git a/docs/reference/images/window-gtk.png b/docs/reference/images/window-gtk.png
new file mode 100644
index 0000000000..839f32f9a2
Binary files /dev/null and b/docs/reference/images/window-gtk.png differ
diff --git a/docs/reference/images/window-winforms.png b/docs/reference/images/window-winforms.png
new file mode 100644
index 0000000000..f40b0a45c0
Binary files /dev/null and b/docs/reference/images/window-winforms.png differ
diff --git a/docs/spelling_wordlist b/docs/spelling_wordlist
index 6c77e72c6e..a24a19c47a 100644
--- a/docs/spelling_wordlist
+++ b/docs/spelling_wordlist
@@ -16,6 +16,7 @@ codepoint
 coroutine
 CSS
 Ctrl
+dialogs
 Django
 draggable
 Flexbox
@@ -58,9 +59,11 @@ reStructuredText
 runtime
 scrollable
 scrollers
+Segoe
 selectable
 Stimpy
 stylesheet
+subclasses
 Subclasses
 substring
 substrings
diff --git a/dummy/setup.cfg b/dummy/setup.cfg
index f960856f4d..b84bab24c0 100644
--- a/dummy/setup.cfg
+++ b/dummy/setup.cfg
@@ -12,7 +12,7 @@ author_email = russell@keith-magee.com
 maintainer = BeeWare Team
 maintainer_email = team@beeware.org
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Intended Audience :: Developers
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
diff --git a/dummy/src/toga_dummy/app.py b/dummy/src/toga_dummy/app.py
index 7e9f635310..0f752b5e7d 100644
--- a/dummy/src/toga_dummy/app.py
+++ b/dummy/src/toga_dummy/app.py
@@ -1,6 +1,8 @@
 import asyncio
+import sys
+from pathlib import Path
 
-from .utils import LoggedObject, not_required_on
+from .utils import LoggedObject
 from .window import Window
 
 
@@ -12,23 +14,24 @@ class App(LoggedObject):
     def __init__(self, interface):
         super().__init__()
         self.interface = interface
-        self.loop = asyncio.new_event_loop()
+        self.interface._impl = self
+
+        self.loop = asyncio.get_event_loop()
+        self.create()
 
     def create(self):
-        self._action("create")
+        self._action("create App")
         self.interface._startup()
 
-    @not_required_on("mobile")
     def create_menus(self):
-        self._action("create menus")
+        self._action("create App menus")
 
     def main_loop(self):
         print("Starting app using Dummy backend.")
         self._action("main loop")
-        self.create()
 
     def set_main_window(self, window):
-        self._set_value("main_window", window)
+        self._action("set_main_window", window=window)
 
     def show_about_dialog(self):
         self._action("show_about_dialog")
@@ -39,31 +42,39 @@ def beep(self):
     def exit(self):
         self._action("exit")
 
-    @not_required_on("mobile")
     def get_current_window(self):
-        self._action("get_current_window")
+        try:
+            return self._get_value("current_window", self.interface.main_window._impl)
+        except AttributeError:
+            return None
 
-    @not_required_on("mobile")
-    def set_current_window(self):
-        self._action("set_current_window")
+    def set_current_window(self, window):
+        self._action("set_current_window", window=window)
+        self._set_value("current_window", window._impl)
 
-    @not_required_on("mobile")
     def enter_full_screen(self, windows):
         self._action("enter_full_screen", windows=windows)
 
-    @not_required_on("mobile")
     def exit_full_screen(self, windows):
         self._action("exit_full_screen", windows=windows)
 
-    @not_required_on("mobile")
     def show_cursor(self):
         self._action("show_cursor")
 
-    @not_required_on("mobile")
     def hide_cursor(self):
         self._action("hide_cursor")
 
+    def simulate_exit(self):
+        self.interface.on_exit()
+
 
-@not_required_on("mobile", "web")
 class DocumentApp(App):
-    pass
+    def create(self):
+        self._action("create DocumentApp")
+        self.interface._startup()
+
+        try:
+            # Create and show the document instance
+            self.interface._open(Path(sys.argv[1]))
+        except IndexError:
+            pass
diff --git a/dummy/src/toga_dummy/dialogs.py b/dummy/src/toga_dummy/dialogs.py
index 9bd760065b..39e23d35e1 100644
--- a/dummy/src/toga_dummy/dialogs.py
+++ b/dummy/src/toga_dummy/dialogs.py
@@ -1,7 +1,3 @@
-from .utils import not_required
-
-
-@not_required  # Testbed coverage is complete.
 class BaseDialog:
     def __init__(self, interface, on_result):
         self.interface = interface
@@ -9,11 +5,10 @@ def __init__(self, interface, on_result):
         self.on_result = on_result
 
     def simulate_result(self, result):
-        self.on_result(None, result)
+        self.on_result(result)
         self.interface.future.set_result(result)
 
 
-@not_required  # Testbed coverage is complete.
 class InfoDialog(BaseDialog):
     def __init__(self, interface, title, message, on_result=None):
         super().__init__(interface, on_result=on_result)
@@ -24,7 +19,6 @@ def __init__(self, interface, title, message, on_result=None):
         )
 
 
-@not_required  # Testbed coverage is complete.
 class QuestionDialog(BaseDialog):
     def __init__(self, interface, title, message, on_result=None):
         super().__init__(interface, on_result=on_result)
@@ -35,7 +29,6 @@ def __init__(self, interface, title, message, on_result=None):
         )
 
 
-@not_required  # Testbed coverage is complete.
 class ConfirmDialog(BaseDialog):
     def __init__(self, interface, title, message, on_result=None):
         super().__init__(interface, on_result=on_result)
@@ -46,7 +39,6 @@ def __init__(self, interface, title, message, on_result=None):
         )
 
 
-@not_required  # Testbed coverage is complete.
 class ErrorDialog(BaseDialog):
     def __init__(self, interface, title, message, on_result=None):
         super().__init__(interface, on_result=on_result)
@@ -57,7 +49,6 @@ def __init__(self, interface, title, message, on_result=None):
         )
 
 
-@not_required  # Testbed coverage is complete.
 class StackTraceDialog(BaseDialog):
     def __init__(self, interface, title, message, content, retry, on_result=None):
         super().__init__(interface, on_result=on_result)
@@ -70,7 +61,6 @@ def __init__(self, interface, title, message, content, retry, on_result=None):
         )
 
 
-@not_required  # Testbed coverage is complete.
 class SaveFileDialog(BaseDialog):
     def __init__(
         self,
@@ -91,7 +81,6 @@ def __init__(
         )
 
 
-@not_required  # Testbed coverage is complete.
 class OpenFileDialog(BaseDialog):
     def __init__(
         self,
@@ -112,7 +101,6 @@ def __init__(
         )
 
 
-@not_required  # Testbed coverage is complete.
 class SelectFolderDialog(BaseDialog):
     def __init__(
         self,
diff --git a/dummy/src/toga_dummy/documents.py b/dummy/src/toga_dummy/documents.py
index a22d2bb254..9de290b969 100644
--- a/dummy/src/toga_dummy/documents.py
+++ b/dummy/src/toga_dummy/documents.py
@@ -5,3 +5,4 @@ class Document(LoggedObject):
     def __init__(self, interface):
         super().__init__()
         self.interface = interface
+        self.interface.read()
diff --git a/dummy/src/toga_dummy/fonts.py b/dummy/src/toga_dummy/fonts.py
index 833e3444e8..ff8d442123 100644
--- a/dummy/src/toga_dummy/fonts.py
+++ b/dummy/src/toga_dummy/fonts.py
@@ -1,7 +1,6 @@
-from .utils import LoggedObject, not_required
+from .utils import LoggedObject
 
 
-@not_required  # Testbed coverage is complete for this class
 class Font(LoggedObject):
     def __init__(self, interface):
         super().__init__()
diff --git a/dummy/src/toga_dummy/icons.py b/dummy/src/toga_dummy/icons.py
index 98a5c66596..fd765e1dd4 100644
--- a/dummy/src/toga_dummy/icons.py
+++ b/dummy/src/toga_dummy/icons.py
@@ -1,7 +1,6 @@
-from .utils import LoggedObject, not_required
+from .utils import LoggedObject
 
 
-@not_required  # Testbed coverage is complete.
 class Icon(LoggedObject):
     EXTENSIONS = [".png", ".ico"]
     SIZES = None
diff --git a/dummy/src/toga_dummy/images.py b/dummy/src/toga_dummy/images.py
index ef70b8a9eb..5949e72c40 100644
--- a/dummy/src/toga_dummy/images.py
+++ b/dummy/src/toga_dummy/images.py
@@ -1,7 +1,6 @@
-from .utils import LoggedObject, not_required
+from .utils import LoggedObject
 
 
-@not_required  # Testbed coverage is complete
 class Image(LoggedObject):
     def __init__(self, interface, path=None, data=None):
         super().__init__()
@@ -17,5 +16,8 @@ def get_width(self):
     def get_height(self):
         return 40
 
+    def get_data(self):
+        return b"pretend this is PNG image data"
+
     def save(self, path):
         self._action("save", path=path)
diff --git a/dummy/src/toga_dummy/test_implementation.py b/dummy/src/toga_dummy/test_implementation.py
deleted file mode 100644
index fbd5600254..0000000000
--- a/dummy/src/toga_dummy/test_implementation.py
+++ /dev/null
@@ -1,456 +0,0 @@
-import ast
-import importlib
-import os
-import unittest
-from collections import defaultdict, namedtuple
-
-try:
-    # Usually, the pattern is "import module; if it doesn't exist,
-    # import the shim". However, we need the 3.10 API for entry_points,
-    # as the 3.8 didn't support the `groups` argument to entry_points.
-    # Therefore, we try to import the compatibility shim first; and fall
-    # back to the stdlib module if the shim isn't there.
-    from importlib_metadata import entry_points
-except ImportError:
-    from importlib.metadata import entry_points
-
-from itertools import zip_longest
-from os.path import join
-from pathlib import Path
-
-import toga_dummy
-
-
-class NoDefault:
-    """This utility class to indicate that no argument default exists.
-
-    The use of `None` is not possible because it itself could be a default argument
-    value.
-    """
-
-    def __eq__(self, other):
-        if isinstance(other, NoDefault):
-            return True
-        else:
-            return False
-
-    def __repr__(self):
-        return "no_default"
-
-
-FunctionArguments = namedtuple(
-    "FunctionArguments", ["args", "vararg", "kwarg", "kwonlyargs"]
-)
-
-
-class DefinitionExtractor:
-    """The DefinitionExtractor consumes a .py file and extracts information, with the
-    help of the 'ast' module from it.
-
-    Non-existing files result in an empty DefinitionExtractor, this means the
-    all properties return empty lists or dicts.
-
-    Args:
-        path (str): The path to the .py file.
-    """
-
-    def __init__(self, path, platform_category=None):
-        self.exists = os.path.isfile(path)
-        self._classes = {}
-        self._methods = defaultdict(dict)
-        self.platform = platform_category if platform_category else None
-
-        if self.exists:
-            # open the file and parse it with the ast module.
-            with open(path) as f:
-                lines = f.read()
-            self.tree = ast.parse(lines)
-            self._extract_file()
-
-    def _extract_file(self):
-        self._extract_classes()
-        self._extract_class_methods()
-
-    @property
-    def class_names(self):
-        return self._classes.keys()
-
-    @property
-    def method_names(self):
-        return self._methods.keys()
-
-    def _extract_classes(self):
-        for node in ast.walk(self.tree):
-            if isinstance(node, ast.ClassDef):
-                if self.is_required_for_platform(node):
-                    self._classes[node.name] = node  # use the class name as the key
-            elif isinstance(node, ast.Assign) and node.col_offset == 0:
-                # Allow a class with no new methods to be defined by assigning
-                # from an existing class. The col_offset means we only pay
-                # attention to assignments at the top level of a module, not
-                # assignments inside method bodies.
-                for target in node.targets:
-                    if isinstance(target, ast.Name):
-                        self._classes[target.id] = node
-
-    def is_required_for_platform(self, node):
-        """Checks if the class or function is required for the given platform. It looks
-        for a decorator with the name `not_required_on`.
-
-        Returns:
-            `True` if the class/function is required for the platform.
-            `False` if the class/function is not required and can be dropped for this platform.
-        """
-        if node.decorator_list:  # check if a decorator list exists
-            for decorator in node.decorator_list:
-                try:
-                    # @not_required is a bare decorator, so the decorator node
-                    # has an `id` attribute.
-                    # @not_required_on is a decorator factory, so the decorator
-                    # node contains a function that has an id.
-                    if getattr(decorator, "id", None) == "not_required":
-                        return False
-                    elif decorator.func.id == "not_required_on":
-                        platforms_to_skip = [arg.s for arg in decorator.args]
-                        if self.platform.intersection(set(platforms_to_skip)):
-                            return False
-                except Exception:
-                    pass
-        return True
-
-    @staticmethod
-    def _get_function_defaults(node, kwonlyargs=False):
-        if kwonlyargs:
-            to_extract = node.kw_defaults
-        else:
-            to_extract = node.defaults
-
-        defaults = []
-        for default in to_extract:
-            if isinstance(default, ast.NameConstant):
-                defaults.append(default.value)
-            elif isinstance(default, ast.Str):
-                defaults.append(default.s)
-            elif isinstance(default, ast.Num):
-                defaults.append(default.n)
-            elif isinstance(default, ast.Tuple) or isinstance(default, ast.List):
-                defaults.append(default.elts)
-            elif isinstance(default, ast.Call):
-                defaults.append(default.func)
-            elif isinstance(default, ast.Attribute):
-                defaults.append(default.value)
-            elif isinstance(default, ast.Name):
-                defaults.append(default.id)
-            else:
-                raise RuntimeWarning(
-                    'ast classes of type "{}" can not be handled at the moment. '
-                    "Please implement to make this warning disappear.".format(default)
-                )
-        return defaults
-
-    def _extract_class_methods(self):
-        """Extract all the methods from the classes and save them in `self.methods`.
-
-        Use the combination of class and method name, like so:
-        `<class_name>.<method_name>` as the key.
-        """
-        for class_name in self._classes:
-            for node in ast.walk(self._classes[class_name]):
-                if isinstance(node, ast.FunctionDef):
-                    if self.is_required_for_platform(node):
-                        function_id = f"{class_name}.{node.name}"
-                        self._methods[function_id]["node"] = node
-                        self._methods[function_id][
-                            "arguments"
-                        ] = self._extract_function_signature(node)
-
-    def _extract_function_signature(self, node):
-        for node in ast.walk(node):
-            if isinstance(node, ast.arguments):
-                # Extract positional arguments and possible default values.
-                args = [arg.arg for arg in node.args]
-                args_defaults = self._get_function_defaults(node)
-                # Extract kwonlyargs and defaults.
-                kwonlyargs = [arg.arg for arg in node.kwonlyargs]
-                kwonlyargs_defaults = self._get_function_defaults(node, kwonlyargs=True)
-
-                # Combine arguments and their corresponding default values,
-                # if no default value exists fill it with a NoDefault object.
-                args_plus_defaults = list(
-                    zip_longest(
-                        reversed(args), reversed(args_defaults), fillvalue=NoDefault()
-                    )
-                )
-                kwonlyargs_plus_defaults = list(
-                    zip_longest(
-                        reversed(kwonlyargs),
-                        reversed(kwonlyargs_defaults),
-                        fillvalue=NoDefault(),
-                    )
-                )
-
-                vararg = node.vararg.arg if node.vararg is not None else None
-                kwarg = node.kwarg.arg if node.kwarg is not None else None
-
-                return FunctionArguments(
-                    args=args_plus_defaults,
-                    vararg=vararg,
-                    kwarg=kwarg,
-                    kwonlyargs=kwonlyargs_plus_defaults,
-                )
-
-    def get_function_def(self, function_id):
-        return self._methods[function_id]
-
-    def methods_of_class(self, class_name):
-        """Get all methods names of a class.
-
-        Args:
-            class_name(str): Name of the class to extract the methods
-
-        Returns:
-            Returns a `List` of (str) with all methods names of the class.
-
-        Warnings:
-            Does not return inherited methods. Only methods that are present in the class and the actual .py file.
-        """
-        methods = []
-        if self.exists:
-            if class_name in self._classes.keys():
-                class_node = self._classes[class_name]
-                for node in ast.walk(class_node):
-                    if isinstance(node, ast.FunctionDef):
-                        if self.is_required_for_platform(
-                            node
-                        ) and not node.name.startswith("simulate_"):
-                            methods.append(node.name)
-        return methods
-
-
-def get_platform_category(path_to_backend):
-    backend_name = os.path.basename(path_to_backend)
-    importlib.import_module(backend_name)
-    platform = {ep.value: ep.name for ep in entry_points(group="toga.backends")}[
-        backend_name
-    ]
-
-    return {
-        # Desktop
-        "macOS": {"desktop", backend_name.split("_")[-1]},
-        "windows": {"desktop", backend_name.split("_")[-1]},
-        "linux": {"desktop", backend_name.split("_")[-1]},
-        # Mobile
-        "iOS": {"mobile", backend_name.split("_")[-1]},
-        "android": {"mobile", backend_name.split("_")[-1]},
-    }.get(platform, {platform, backend_name.split("_")[-1]})
-
-
-def get_required_files(platform_category, path_to_backend):
-    # Find the list of files in the dummy backend
-    # that aren't *this* file, or an __init__.py.
-    files = [
-        str(p.relative_to(Path(__file__).parent))
-        for p in Path(__file__).parent.rglob("**/*.py")
-        if str(p) != __file__ and p.name != "__init__.py"
-    ]
-    if "desktop" in platform_category:
-        for f in TOGA_DESKTOP_EXCLUDED_FILES:
-            files.remove(f)
-    if "mobile" in platform_category:
-        for f in TOGA_MOBILE_EXCLUDED_FILES:
-            files.remove(f)
-    if "web" in platform_category:
-        for f in TOGA_WEB_EXCLUDED_FILES:
-            files.remove(f)
-    if "console" in platform_category:
-        for f in TOGA_CONSOLE_EXCLUDED_FILES:
-            files.remove(f)
-    if "settop" in platform_category:
-        for f in TOGA_SETTOP_EXCLUDED_FILES:
-            files.remove(f)
-    if "watch" in platform_category:
-        for f in TOGA_WATCH_EXCLUDED_FILES:
-            files.remove(f)
-
-    return files
-
-
-def create_impl_tests(root):
-    """Calling this function with the path to a Toga backend will return the
-    implementation tests for this backend.
-
-    Args:
-        root (str): The absolute path to a toga backend.
-
-    Returns:
-        A dictionary of test classes.
-    """
-    platform_category = get_platform_category(root)
-    dummy_files = collect_dummy_files(get_required_files(platform_category, root))
-    tests = {}
-    for name, dummy_path in dummy_files:
-        if "widgets" in dummy_path:
-            path = os.path.join(root, f"widgets/{name}.py")
-        else:
-            path = os.path.join(root, f"{name}.py")
-
-        tests.update(make_toga_impl_check_class(path, dummy_path, platform_category))
-    return tests
-
-
-TestFile = namedtuple("TestFile", ["name", "path"])
-
-
-def collect_dummy_files(required_files):
-    dummy_files = []
-    toga_dummy_base = os.path.dirname(toga_dummy.__file__)
-
-    for root, dirs, filenames in os.walk(toga_dummy_base):
-        for filename in filenames:
-            # exclude non .py filenames or start with '__'
-            if filename.startswith("__") or not filename.endswith(".py"):
-                continue
-
-            full_filename = os.path.join(root, filename)[len(toga_dummy_base) + 1 :]
-            if full_filename in required_files:
-                f = TestFile(filename[:-3], os.path.join(root, filename))
-                dummy_files.append(f)
-
-    return dummy_files
-
-
-def make_test_function(element, element_list, error_msg=None):
-    def fn(self):
-        self.assertIn(element, element_list, msg=error_msg if error_msg else fn.__doc__)
-
-    return fn
-
-
-def make_test_class(path, cls, expected, actual, skip):
-    class_name = f"{cls}ImplTest"
-    test_class = type(class_name, (unittest.TestCase,), {})
-
-    if skip:
-        test_class = unittest.skip(skip)(test_class)
-
-    fn = make_test_function(cls, actual.class_names)
-    fn.__doc__ = (
-        "Expect class {} to be defined in {}, to be consistent with dummy implementation"
-    ).format(cls, path)
-    test_class.test_class_exists = fn
-
-    for method in expected.methods_of_class(cls):
-        # create a test that checks if the method exists in the class.
-        fn = make_test_function(method, actual.methods_of_class(cls))
-        fn.__doc__ = f"The method {cls}.{method}(...) exists"
-        setattr(test_class, f"test_{method}_exists", fn)
-
-        # create tests that check for the right method arguments.
-        method_id = f"{cls}.{method}"
-        method_def = expected.get_function_def(method_id)["arguments"]
-        try:
-            actual_method_def = actual.get_function_def(method_id)["arguments"]
-        except KeyError:
-            actual_method_def = None
-
-        if actual_method_def:
-            # Create test whether the method takes the right arguments
-            # and if the arguments have the right name.
-
-            # ARGS
-            for arg in method_def.args:
-                fn = make_test_function(arg, actual_method_def.args)
-                fn.__doc__ = "The argument {}.{}(..., {}={}, ...) exists".format(
-                    cls, method, *arg
-                )
-                setattr(
-                    test_class, "test_{}_arg_{}_default_{}".format(method, *arg), fn
-                )
-
-            # *varargs
-            if method_def.vararg:
-                vararg = method_def.vararg
-                actual_vararg = (
-                    actual_method_def.vararg if actual_method_def.vararg else []
-                )
-                fn = make_test_function(vararg, actual_vararg)
-                fn.__doc__ = f"The vararg {cls}.{method}(..., *{vararg}, ...) exists"
-                setattr(test_class, f"test_{method}_vararg_{vararg}", fn)
-
-            # **kwarg
-            if method_def.kwarg:
-                kwarg = method_def.kwarg
-                actual_kwarg = (
-                    actual_method_def.kwarg if actual_method_def.kwarg else []
-                )
-                fn = make_test_function(
-                    kwarg,
-                    actual_kwarg,
-                    error_msg="The method does not take kwargs or the "
-                    'variable is not named "{}".'.format(kwarg),
-                )
-                fn.__doc__ = (
-                    f"The kw argument {cls}.{method}(..., **{kwarg}, ...) exists"
-                )
-                setattr(test_class, f"test_{method}_kw_{kwarg}", fn)
-
-            # kwonlyargs
-            if method_def.kwonlyargs:
-                for kwonlyarg in method_def.kwonlyargs:
-                    fn = make_test_function(kwonlyarg, actual_method_def.kwonlyargs)
-                    fn.__doc__ = (
-                        "The kwonly argument {}.{}(..., {}={}, ...) exists".format(
-                            cls, method, *kwonlyarg
-                        )
-                    )
-                    setattr(
-                        test_class,
-                        "test_{}_kwonly_{}_default_{}".format(method, *kwonlyarg),
-                        fn,
-                    )
-
-    return class_name, test_class
-
-
-def make_toga_impl_check_class(path, dummy_path, platform):
-    prefix = os.path.commonprefix([path, dummy_path])
-    expected = DefinitionExtractor(dummy_path, platform)
-    if os.path.isfile(path):
-        skip = None
-        actual = DefinitionExtractor(path)
-    else:
-        skip = f"Implementation file {path[len(prefix):]} does not exist"
-        actual = DefinitionExtractor(path)
-
-    test_classes = {}
-
-    for cls in expected.class_names:
-        class_name, test_class = make_test_class(
-            path[len(prefix) :], cls, expected, actual, skip
-        )
-        test_classes[class_name] = test_class
-
-    return test_classes
-
-
-# Files that do not need to be present in mobile implementations of Toga.
-TOGA_MOBILE_EXCLUDED_FILES = [
-    join("widgets", "splitcontainer.py"),
-]
-
-# Files that do not need to be present in desktop implementations of Toga.
-TOGA_DESKTOP_EXCLUDED_FILES = []
-
-# Files do not need to be present in web implementations of Toga.
-TOGA_WEB_EXCLUDED_FILES = [
-    join("widgets", "splitcontainer.py"),
-]
-
-# Files that do not need to be present in console implementations of Toga.
-TOGA_CONSOLE_EXCLUDED_FILES = []
-
-# Files that do not need to be present in set-top box implementations of Toga.
-TOGA_SETTOP_EXCLUDED_FILES = []
-
-# Files that do not need to be present in watch implementations of Toga.
-TOGA_WATCH_EXCLUDED_FILES = []
diff --git a/dummy/src/toga_dummy/utils.py b/dummy/src/toga_dummy/utils.py
index 629b31ec18..e5c3a772ac 100644
--- a/dummy/src/toga_dummy/utils.py
+++ b/dummy/src/toga_dummy/utils.py
@@ -1,5 +1,3 @@
-import sys
-import unittest
 from unittest.mock import Mock
 
 import pytest
@@ -8,49 +6,6 @@
 from travertino.size import BaseIntrinsicSize
 
 
-def not_required(method_or_class):
-    """This decorator function is used to mark methods or classes that they are not
-    required for interface compliance.
-
-    :param method_or_class: The method or class to decorate
-    :returns: The method or class being decorated
-    """
-    return method_or_class
-
-
-def not_required_on(*args):
-    """This decorator function is used to mark methods or classes that they are not
-    required on certain platforms. This is only used by the implementation checks
-    creation mechanism.
-
-    Examples:
-        >>> # Marks the function as only required on platforms that are not "mobile".
-        >>> @not_required_on('mobile')
-        >>> def open_window():
-        >>>     self.window.open()
-
-        >>> # Function is not required on "mobile" and "gtk" backends.
-        >>> @not_required_on('mobile', 'gtk')
-        >>> def open_window():
-        >>>     self.window.open()
-
-    :param args: The platform(s) on which the method or class isn't required.
-        Can accept a specific backend (e.g., `gtk`, `iOS`), or a class of platform
-        (e.g., `mobile`, `desktop`).
-    :returns: The method or class being decorated
-    """
-
-    def _dec(method_or_class):
-        return method_or_class
-
-    return _dec
-
-
-###########################################################################
-# The event types that can be logged
-###########################################################################
-
-
 class EventLog:
     # Event types that can be logged
     SET_VALUE = "set attribute"
@@ -437,99 +392,3 @@ def assert_action_performed_with(_widget, _action, **test_data):
     except AttributeError as e:
         # None of the recorded actions match the test data.
         pytest.fail(str(e))
-
-
-###########################################################################
-# Unittest widget assertions
-#
-# These have been (re)written in terms of Pytest assertions; this base
-# class is deprecated and should not be used for new tests.
-############################################################################
-class TestCase(unittest.TestCase):
-    def setUp(self):
-        EventLog.reset()
-
-        # We use the existence of a __main__ module as a proxy for being in test
-        # conditions. This isn't *great*, but the __main__ module isn't meaningful
-        # during tests, and removing it allows us to avoid having explicit "if
-        # under test conditions" checks in paths.py.
-        if "__main__" in sys.modules:
-            del sys.modules["__main__"]
-
-    def reset_event_log(self):
-        EventLog.reset()
-
-    def pytest_assert(self, assertion, *args, **kwargs):
-        try:
-            return assertion(*args, **kwargs)
-        except AssertionError as e:
-            self.fail(str(e))
-
-    #####
-
-    def assertValueSet(self, _widget, _attr, value):
-        """Assert that the widget implementation has set an attribute to a value.
-
-        Args:
-            _widget: The interface of the widget to check
-            _attr: The attribute that should have been set
-            value: The value that the attribute have been set to.
-        """
-        self.assertEqual(self.pytest_assert(attribute_value, _widget, _attr), value)
-
-    def assertValuesSet(self, _widget, _attr, values):
-        """Assert that the widget implementation has been set to multiple values.
-
-        Args:
-            _widget: The interface of the widget to check
-            _attr: The attribute that should have been set
-            values: The values that the attribute have been set to.
-        """
-        self.assertEqual(self.pytest_assert(attribute_values, _widget, _attr), values)
-
-    def assertValueGet(self, _widget, _attr):
-        """Assert that the widget implementation attempted to retrieve an attribute.
-
-        Args:
-            _widget: The interface of the widget to check
-            _attr: The attribute that should have been retrieved
-        """
-        self.pytest_assert(assert_attribute_retrieved, _widget, _attr)
-
-    def assertValueNotGet(self, _widget, _attr):
-        self.pytest_assert(assert_attribute_not_retrieved, _widget, _attr)
-
-    def assertValueNotSet(self, _widget, _attr):
-        self.pytest_assert(assert_attribute_not_set, _widget, _attr)
-
-    def assertActionNotPerformed(self, _widget, _action):
-        """Assert that the named action was *not* performed by a widget.
-
-        Args:
-            _widget: The interface of the widget that should not have performed the action.
-            _action: The name of the action to check
-        """
-        self.pytest_assert(assert_action_not_performed, _widget, _action)
-
-    def assertActionPerformed(self, _widget, _action):
-        """Assert that the named action performed by a widget.
-
-        Args:
-            _widget: The interface of the widget that should have performed the action.
-            _action: The name of the action to check
-        """
-        self.pytest_assert(assert_action_performed, _widget, _action)
-
-    def assertActionPerformedWith(self, _widget, _action, **test_data):
-        """Was the action performed with specific test data.
-
-        Args:
-            _widget: The interface of the widget that should have performed the action.
-            _action: The name of the action to check.
-            **test_data: The arguments that should have been passed to the action.
-
-        Returns:
-            If a matching action was performed, the full data of
-            the performed action if. False otherwise.
-        """
-        self.pytest_assert(assert_action_performed_with, _widget, _action, **test_data)
diff --git a/dummy/src/toga_dummy/widgets/activityindicator.py b/dummy/src/toga_dummy/widgets/activityindicator.py
index 4fab7c6fde..fe648b6d65 100644
--- a/dummy/src/toga_dummy/widgets/activityindicator.py
+++ b/dummy/src/toga_dummy/widgets/activityindicator.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class ActivityIndicator(Widget):
     def create(self):
         self._action("create ActivityIndicator")
diff --git a/dummy/src/toga_dummy/widgets/base.py b/dummy/src/toga_dummy/widgets/base.py
index eefe815b99..4868be0eda 100644
--- a/dummy/src/toga_dummy/widgets/base.py
+++ b/dummy/src/toga_dummy/widgets/base.py
@@ -1,7 +1,6 @@
-from ..utils import LoggedObject, not_required
+from ..utils import LoggedObject
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Widget(LoggedObject):
     def __init__(self, interface):
         super().__init__()
diff --git a/dummy/src/toga_dummy/widgets/box.py b/dummy/src/toga_dummy/widgets/box.py
index 59ac712269..9f23c7f41f 100644
--- a/dummy/src/toga_dummy/widgets/box.py
+++ b/dummy/src/toga_dummy/widgets/box.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Box(Widget):
     def create(self):
         self._action("create Box")
diff --git a/dummy/src/toga_dummy/widgets/button.py b/dummy/src/toga_dummy/widgets/button.py
index 3a42efabf8..0937584f2a 100644
--- a/dummy/src/toga_dummy/widgets/button.py
+++ b/dummy/src/toga_dummy/widgets/button.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Button(Widget):
     def create(self):
         self._action("create Button")
@@ -14,4 +12,4 @@ def set_text(self, text):
         self._set_value("text", text)
 
     def simulate_press(self):
-        self.interface.on_press(None)
+        self.interface.on_press()
diff --git a/dummy/src/toga_dummy/widgets/canvas.py b/dummy/src/toga_dummy/widgets/canvas.py
index 5892ebba04..32b515b292 100644
--- a/dummy/src/toga_dummy/widgets/canvas.py
+++ b/dummy/src/toga_dummy/widgets/canvas.py
@@ -2,11 +2,9 @@
 
 from toga.fonts import SYSTEM, SYSTEM_DEFAULT_FONT_SIZE
 
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Canvas(Widget):
     def create(self):
         self._action("create Canvas")
@@ -259,22 +257,22 @@ def simulate_resize(self):
     # 'Mouse' button handlers
 
     def simulate_press(self, x, y):
-        self.interface.on_press(None, x=x, y=y)
+        self.interface.on_press(x=x, y=y)
 
     def simulate_activate(self, x, y):
-        self.interface.on_activate(None, x=x, y=y)
+        self.interface.on_activate(x=x, y=y)
 
     def simulate_alt_press(self, x, y):
-        self.interface.on_alt_press(None, x=x, y=y)
+        self.interface.on_alt_press(x=x, y=y)
 
     def simulate_release(self, x, y):
-        self.interface.on_release(None, x=x, y=y)
+        self.interface.on_release(x=x, y=y)
 
     def simulate_alt_release(self, x, y):
-        self.interface.on_alt_release(None, x=x, y=y)
+        self.interface.on_alt_release(x=x, y=y)
 
     def simulate_drag(self, x, y):
-        self.interface.on_drag(None, x=x, y=y)
+        self.interface.on_drag(x=x, y=y)
 
     def simulate_alt_drag(self, x, y):
-        self.interface.on_alt_drag(None, x=x, y=y)
+        self.interface.on_alt_drag(x=x, y=y)
diff --git a/dummy/src/toga_dummy/widgets/dateinput.py b/dummy/src/toga_dummy/widgets/dateinput.py
index b7596088b1..219f5e9af9 100644
--- a/dummy/src/toga_dummy/widgets/dateinput.py
+++ b/dummy/src/toga_dummy/widgets/dateinput.py
@@ -1,10 +1,8 @@
 from datetime import date
 
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class DateInput(Widget):
     def create(self):
         self._action("create DateInput")
@@ -14,7 +12,7 @@ def get_value(self):
 
     def set_value(self, value):
         self._set_value("value", value)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_min_date(self):
         return self._get_value("min date", date(1901, 1, 1))
diff --git a/dummy/src/toga_dummy/widgets/detailedlist.py b/dummy/src/toga_dummy/widgets/detailedlist.py
index 09e84fdbb1..df4326cc66 100644
--- a/dummy/src/toga_dummy/widgets/detailedlist.py
+++ b/dummy/src/toga_dummy/widgets/detailedlist.py
@@ -1,15 +1,13 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class DetailedList(Widget):
     def create(self):
         self._action("create DetailedList")
 
     def change_source(self, source):
         self._action("change source", source=source)
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def insert(self, index, item):
         self._action("insert item", index=index, item=item)
@@ -43,7 +41,7 @@ def scroll_to_row(self, row):
 
     def simulate_selection(self, row):
         self._set_value("selection", row)
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def stimulate_refresh(self):
-        self.interface.on_refresh(None)
+        self.interface.on_refresh()
diff --git a/dummy/src/toga_dummy/widgets/divider.py b/dummy/src/toga_dummy/widgets/divider.py
index 41d7eb8031..cf439c3652 100644
--- a/dummy/src/toga_dummy/widgets/divider.py
+++ b/dummy/src/toga_dummy/widgets/divider.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Divider(Widget):
     def create(self):
         self._action("create Divider")
diff --git a/dummy/src/toga_dummy/widgets/imageview.py b/dummy/src/toga_dummy/widgets/imageview.py
index b56d326dcb..d967d8bce7 100644
--- a/dummy/src/toga_dummy/widgets/imageview.py
+++ b/dummy/src/toga_dummy/widgets/imageview.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete
 class ImageView(Widget):
     def create(self):
         self._action("create ImageView")
diff --git a/dummy/src/toga_dummy/widgets/label.py b/dummy/src/toga_dummy/widgets/label.py
index 137857b124..2dd5517022 100644
--- a/dummy/src/toga_dummy/widgets/label.py
+++ b/dummy/src/toga_dummy/widgets/label.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Label(Widget):
     def create(self):
         self._action("create Label")
diff --git a/dummy/src/toga_dummy/widgets/multilinetextinput.py b/dummy/src/toga_dummy/widgets/multilinetextinput.py
index 1c2a02c2c8..705ae25bc4 100644
--- a/dummy/src/toga_dummy/widgets/multilinetextinput.py
+++ b/dummy/src/toga_dummy/widgets/multilinetextinput.py
@@ -1,15 +1,13 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class MultilineTextInput(Widget):
     def create(self):
         self._action("create MultilineTextInput")
 
     def set_value(self, value):
         self._set_value("value", value)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_value(self):
         return self._get_value("value")
@@ -33,4 +31,4 @@ def scroll_to_top(self):
         self._action("scroll to top")
 
     def simulate_change(self):
-        self.interface.on_change(None)
+        self.interface.on_change()
diff --git a/dummy/src/toga_dummy/widgets/numberinput.py b/dummy/src/toga_dummy/widgets/numberinput.py
index 024a273fdb..7e6a0500f4 100644
--- a/dummy/src/toga_dummy/widgets/numberinput.py
+++ b/dummy/src/toga_dummy/widgets/numberinput.py
@@ -1,10 +1,8 @@
 from toga.widgets.numberinput import _clean_decimal
 
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class NumberInput(Widget):
     def create(self):
         self._action("create NumberInput")
@@ -26,7 +24,7 @@ def set_max_value(self, value):
 
     def set_value(self, value):
         self._set_value("value", value)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_value(self):
         value = self._get_value("value", None)
@@ -39,4 +37,4 @@ def set_on_change(self, handler):
         self._set_value("on_change", handler)
 
     def simulate_change(self):
-        self.interface.on_change(None)
+        self.interface.on_change()
diff --git a/dummy/src/toga_dummy/widgets/optioncontainer.py b/dummy/src/toga_dummy/widgets/optioncontainer.py
index d35e02d710..c1bcef8a72 100644
--- a/dummy/src/toga_dummy/widgets/optioncontainer.py
+++ b/dummy/src/toga_dummy/widgets/optioncontainer.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required
 class Option:
     def __init__(self, text, widget, enabled):
         self.text = text
@@ -10,7 +8,6 @@ def __init__(self, text, widget, enabled):
         self.enabled = enabled
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class OptionContainer(Widget):
     def create(self):
         self._action("create OptionContainer")
@@ -44,7 +41,7 @@ def get_option_text(self, index):
 
     def set_current_tab_index(self, current_tab_index):
         self._set_value("current_tab_index", current_tab_index)
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def get_current_tab_index(self):
         return self._get_value("current_tab_index", None)
diff --git a/dummy/src/toga_dummy/widgets/passwordinput.py b/dummy/src/toga_dummy/widgets/passwordinput.py
index 0d6b2b5cc7..a3c6315384 100644
--- a/dummy/src/toga_dummy/widgets/passwordinput.py
+++ b/dummy/src/toga_dummy/widgets/passwordinput.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .textinput import TextInput
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class PasswordInput(TextInput):
     def create(self):
         self._action("create PasswordInput")
diff --git a/dummy/src/toga_dummy/widgets/progressbar.py b/dummy/src/toga_dummy/widgets/progressbar.py
index ef2aa59f83..cea8c52ccf 100644
--- a/dummy/src/toga_dummy/widgets/progressbar.py
+++ b/dummy/src/toga_dummy/widgets/progressbar.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class ProgressBar(Widget):
     def create(self):
         self._action("create ProgressBar")
diff --git a/dummy/src/toga_dummy/widgets/scrollcontainer.py b/dummy/src/toga_dummy/widgets/scrollcontainer.py
index b93347fa1e..863d5164ea 100644
--- a/dummy/src/toga_dummy/widgets/scrollcontainer.py
+++ b/dummy/src/toga_dummy/widgets/scrollcontainer.py
@@ -1,9 +1,7 @@
-from ..utils import not_required
 from ..window import Container
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class ScrollContainer(Widget):
     def create(self):
         self._action("create ScrollContainer")
@@ -31,7 +29,7 @@ def set_vertical(self, value):
         # Disabling scrolling implies a position reset; that's a scroll event.
         if value is False:
             self._set_value("vertical_position", 0)
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
 
     def get_horizontal(self):
         return self._get_value("horizontal", True)
@@ -42,7 +40,7 @@ def set_horizontal(self, value):
         # Disabling scrolling implies a position reset; that's a scroll event.
         if value is False:
             self._set_value("horizontal_position", 0)
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
 
     def set_on_scroll(self, on_scroll):
         self._set_value("on_scroll", on_scroll)
@@ -50,7 +48,7 @@ def set_on_scroll(self, on_scroll):
     def set_position(self, horizontal_position, vertical_position):
         self._set_value("horizontal_position", horizontal_position)
         self._set_value("vertical_position", vertical_position)
-        self.interface.on_scroll(None)
+        self.interface.on_scroll()
 
     def get_horizontal_position(self):
         return self._get_value("horizontal_position", 0)
diff --git a/dummy/src/toga_dummy/widgets/selection.py b/dummy/src/toga_dummy/widgets/selection.py
index 44903cf18e..d5af292365 100644
--- a/dummy/src/toga_dummy/widgets/selection.py
+++ b/dummy/src/toga_dummy/widgets/selection.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Selection(Widget):
     def create(self):
         self._action("create Selection")
@@ -47,4 +45,4 @@ def get_selected_index(self):
 
     def simulate_selection(self, item):
         self._set_value("selected_item", item)
-        self.interface.on_change(None)
+        self.interface.on_change()
diff --git a/dummy/src/toga_dummy/widgets/slider.py b/dummy/src/toga_dummy/widgets/slider.py
index 59236b1944..31c2a4137a 100644
--- a/dummy/src/toga_dummy/widgets/slider.py
+++ b/dummy/src/toga_dummy/widgets/slider.py
@@ -1,10 +1,8 @@
 import toga
 
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Slider(Widget, toga.widgets.slider.SliderImpl):
     def create(self):
         self._action("create Slider")
diff --git a/dummy/src/toga_dummy/widgets/splitcontainer.py b/dummy/src/toga_dummy/widgets/splitcontainer.py
index 88690bb594..d6e7d2b107 100644
--- a/dummy/src/toga_dummy/widgets/splitcontainer.py
+++ b/dummy/src/toga_dummy/widgets/splitcontainer.py
@@ -1,11 +1,9 @@
 from toga.constants import Direction
 
-from ..utils import not_required
 from ..window import Container
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class SplitContainer(Widget):
     def create(self):
         self._action("create SplitContainer")
diff --git a/dummy/src/toga_dummy/widgets/switch.py b/dummy/src/toga_dummy/widgets/switch.py
index 33cdc82fdf..0bf88fa5a7 100644
--- a/dummy/src/toga_dummy/widgets/switch.py
+++ b/dummy/src/toga_dummy/widgets/switch.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Switch(Widget):
     def create(self):
         self._action("create Switch")
@@ -20,7 +18,7 @@ def set_value(self, value):
         old_value = self._get_value("value", None)
         self._set_value("value", value)
         if value != old_value:
-            self.interface.on_change(None)
+            self.interface.on_change()
 
     def simulate_toggle(self):
-        self.interface.on_change(None)
+        self.interface.on_change()
diff --git a/dummy/src/toga_dummy/widgets/table.py b/dummy/src/toga_dummy/widgets/table.py
index 1e5d42b710..add89254c7 100644
--- a/dummy/src/toga_dummy/widgets/table.py
+++ b/dummy/src/toga_dummy/widgets/table.py
@@ -1,15 +1,13 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Table(Widget):
     def create(self):
         self._action("create Table")
 
     def change_source(self, source):
         self._action("change source", source=source)
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def insert(self, index, item):
         self._action("insert row", index=index, item=item)
@@ -40,7 +38,7 @@ def remove_column(self, index):
 
     def simulate_selection(self, row):
         self._set_value("selection", row)
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def simulate_activate(self, row):
-        self.interface.on_activate(None, row=self.interface.data[row])
+        self.interface.on_activate(row=self.interface.data[row])
diff --git a/dummy/src/toga_dummy/widgets/textinput.py b/dummy/src/toga_dummy/widgets/textinput.py
index 97703f96fd..6459786ec4 100644
--- a/dummy/src/toga_dummy/widgets/textinput.py
+++ b/dummy/src/toga_dummy/widgets/textinput.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class TextInput(Widget):
     def create(self):
         self._action("create TextInput")
@@ -38,14 +36,14 @@ def is_valid(self):
         return self._get_value("valid")
 
     def simulate_change(self):
-        self.interface.on_change(None)
+        self.interface.on_change()
         self.interface._validate()
 
     def simulate_confirm(self):
-        self.interface.on_confirm(None)
+        self.interface.on_confirm()
 
     def simulate_gain_focus(self):
-        self.interface.on_gain_focus(None)
+        self.interface.on_gain_focus()
 
     def simulate_lose_focus(self):
-        self.interface.on_lose_focus(None)
+        self.interface.on_lose_focus()
diff --git a/dummy/src/toga_dummy/widgets/timeinput.py b/dummy/src/toga_dummy/widgets/timeinput.py
index 5fc37f105d..5e176fe6fd 100644
--- a/dummy/src/toga_dummy/widgets/timeinput.py
+++ b/dummy/src/toga_dummy/widgets/timeinput.py
@@ -1,10 +1,8 @@
 from datetime import datetime, time
 
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class TimeInput(Widget):
     def create(self):
         self._action("create TimeInput")
@@ -14,7 +12,7 @@ def get_value(self):
 
     def set_value(self, value):
         self._set_value("value", value)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_min_time(self):
         return self._get_value("min time", time(0, 0, 0))
diff --git a/dummy/src/toga_dummy/widgets/tree.py b/dummy/src/toga_dummy/widgets/tree.py
index e35868a57d..a5d45edfbe 100644
--- a/dummy/src/toga_dummy/widgets/tree.py
+++ b/dummy/src/toga_dummy/widgets/tree.py
@@ -1,8 +1,6 @@
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required
 def node_for_path(data, path):
     "Convert a path tuple into a specific node"
     if path is None:
@@ -13,14 +11,13 @@ def node_for_path(data, path):
     return result
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class Tree(Widget):
     def create(self):
         self._action("create Tree")
 
     def change_source(self, source):
         self._action("change source", source=source)
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def insert(self, parent, index, item):
         self._action("insert node", parent=parent, index=index, item=item)
@@ -65,7 +62,7 @@ def remove_column(self, index):
 
     def simulate_selection(self, path):
         self._set_value("selection", path)
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def simulate_activate(self, path):
-        self.interface.on_activate(None, node=node_for_path(self.interface.data, path))
+        self.interface.on_activate(node=node_for_path(self.interface.data, path))
diff --git a/dummy/src/toga_dummy/widgets/webview.py b/dummy/src/toga_dummy/widgets/webview.py
index 3e6bec50e9..be6bb46835 100644
--- a/dummy/src/toga_dummy/widgets/webview.py
+++ b/dummy/src/toga_dummy/widgets/webview.py
@@ -1,10 +1,8 @@
 from toga.widgets.webview import JavaScriptResult
 
-from ..utils import not_required
 from .base import Widget
 
 
-@not_required  # Testbed coverage is complete for this widget.
 class WebView(Widget):
     def create(self):
         self._action("create WebView")
@@ -32,7 +30,7 @@ def evaluate_javascript(self, javascript, on_result=None):
         return self._js_result
 
     def simulate_page_loaded(self):
-        self.interface.on_webview_load(self.interface)
+        self.interface.on_webview_load()
 
         loaded_future = self._get_value("loaded_future", None)
         if loaded_future:
diff --git a/dummy/src/toga_dummy/window.py b/dummy/src/toga_dummy/window.py
index 97ffbb920e..7179239f79 100644
--- a/dummy/src/toga_dummy/window.py
+++ b/dummy/src/toga_dummy/window.py
@@ -1,7 +1,6 @@
-from .utils import LoggedObject, not_required
+from .utils import LoggedObject
 
 
-@not_required  # not part of the formal API spec
 class Container:
     def __init__(self, content=None):
         self.baseline_dpi = 96
@@ -37,7 +36,6 @@ def refreshed(self):
             self.content.refresh()
 
 
-@not_required  # Testbed coverage is complete
 class Window(LoggedObject):
     def __init__(self, interface, title, position, size):
         super().__init__()
@@ -93,8 +91,11 @@ def close(self):
         self._action("close")
         self._set_value("visible", False)
 
+    def get_image_data(self):
+        return b"pretend this is PNG image data"
+
     def set_full_screen(self, is_full_screen):
         self._action("set full screen", full_screen=is_full_screen)
 
     def simulate_close(self):
-        self.interface.on_close(None)
+        self.interface.on_close()
diff --git a/examples/.template/{{ cookiecutter.name }}/{{ cookiecutter.name }}/app.py b/examples/.template/{{ cookiecutter.name }}/{{ cookiecutter.name }}/app.py
index 96b5e4f1d5..9117a2c703 100644
--- a/examples/.template/{{ cookiecutter.name }}/{{ cookiecutter.name }}/app.py	
+++ b/examples/.template/{{ cookiecutter.name }}/{{ cookiecutter.name }}/app.py	
@@ -13,7 +13,7 @@ def do_clear(self, widget, **kwargs):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # Label to show responses.
         self.label = toga.Label('Ready.')
diff --git a/examples/activityindicator/activityindicator/app.py b/examples/activityindicator/activityindicator/app.py
index 00bba37b9f..3542fe4820 100644
--- a/examples/activityindicator/activityindicator/app.py
+++ b/examples/activityindicator/activityindicator/app.py
@@ -15,7 +15,7 @@ def do_stuff(self, widget, **kwargs):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         self.spinner = toga.ActivityIndicator(style=Pack(padding_left=10))
         self.button = toga.Button(
diff --git a/examples/beeliza/beeliza/app.py b/examples/beeliza/beeliza/app.py
index ef9dc25254..cac7c62ddd 100644
--- a/examples/beeliza/beeliza/app.py
+++ b/examples/beeliza/beeliza/app.py
@@ -46,7 +46,7 @@ async def handle_input(self, widget, **kwargs):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         self.partner = Eliza()
 
diff --git a/examples/box/box/app.py b/examples/box/box/app.py
index 0140bd52f6..18812722a2 100644
--- a/examples/box/box/app.py
+++ b/examples/box/box/app.py
@@ -5,11 +5,8 @@
 
 class ExampleBoxApp(toga.App):
     def startup(self):
-        # Window class
-        #   Main window of the application with title and size
-        #   Also make the window non-resizable and non-minimizable.
         self.main_window = toga.MainWindow(
-            title=self.name, size=(800, 500), resizeable=False, minimizable=False
+            size=(800, 500), resizable=False, minimizable=False
         )
         self.yellow_button = toga.Button(
             text="Set yellow color",
diff --git a/examples/button/button/app.py b/examples/button/button/app.py
index d51137ca81..d362d9f4b3 100644
--- a/examples/button/button/app.py
+++ b/examples/button/button/app.py
@@ -8,11 +8,8 @@
 
 class ExampleButtonApp(toga.App):
     def startup(self):
-        # Window class
-        #   Main window of the application with title and size
-        #   Also make the window non-resizable and non-minimizable.
         self.main_window = toga.MainWindow(
-            title=self.name, size=(800, 500), resizeable=False, minimizable=False
+            size=(800, 500), resizable=False, minimizable=False
         )
 
         # Common style of the inner boxes
diff --git a/examples/canvas/canvas/app.py b/examples/canvas/canvas/app.py
index 3f47dad0a3..b5a5c5fd4a 100644
--- a/examples/canvas/canvas/app.py
+++ b/examples/canvas/canvas/app.py
@@ -34,7 +34,7 @@
 class ExampleCanvasApp(toga.App):
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name, size=(750, 500))
+        self.main_window = toga.MainWindow(size=(750, 500))
 
         self.canvas = toga.Canvas(
             style=Pack(flex=1),
diff --git a/examples/colors/colors/app.py b/examples/colors/colors/app.py
index e3ee68e7bc..a643a31409 100644
--- a/examples/colors/colors/app.py
+++ b/examples/colors/colors/app.py
@@ -28,7 +28,7 @@ def _change_color_background(widget):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name, size=(700, 800))
+        self.main_window = toga.MainWindow(size=(700, 800))
 
         # create widgets to test colors on
         button = toga.Button("This is a button", style=Pack(padding=5))
diff --git a/examples/command/command/app.py b/examples/command/command/app.py
index 259a1f6793..06ebef0bbf 100644
--- a/examples/command/command/app.py
+++ b/examples/command/command/app.py
@@ -45,10 +45,9 @@ def startup(self):
         tiberius_icon_256 = "resources/tiberius-256"
 
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # Add commands
-        print("adding commands")
         # Create a "Things" menu group to contain some of the commands.
         # No explicit ordering is provided on the group, so it will appear
         # after application-level menus, but *before* the Command group.
@@ -113,16 +112,18 @@ def startup(self):
         )
         cmd7 = toga.Command(
             self.action7,
-            text="TB action 7",
+            text="TB Action 7",
             tooltip="Perform toolbar action 7",
+            shortcut=toga.Key.MOD_1 + "p",
             order=30,
             icon=tiberius_icon_256,
             group=sub_menu,
+            enabled=False,
         )
 
         def action4(widget):
             print("action 4")
-            cmd3.enabled = not cmd3.enabled
+            cmd7.enabled = not cmd7.enabled
             self.textpanel.value += "action 4\n"
 
         cmd4 = toga.Command(
@@ -134,8 +135,12 @@ def action4(widget):
         )
 
         # The order in which commands are added to the app or the toolbar won't
-        # alter anything. Ordering is defined by the command definitions.
-        self.app.commands.add(cmd1, cmd0, cmd6, cmd4, cmd3)
+        # alter anything. Ordering is determined by the command's properties.
+        #
+        # cmd2 and cmd5 are only explicitly added to the toolbar, but that should
+        # automatically add them to the app. cmd7 is added to both places, but this
+        # should not cause a duplicate menu item.
+        self.app.commands.add(cmd1, cmd0, cmd6, cmd4, cmd3, cmd7)
         self.app.main_window.toolbar.add(cmd2, cmd5, cmd7)
 
         # Buttons
@@ -164,7 +169,6 @@ def action4(widget):
 
 
 def main():
-    print("app.main")
     return ExampleTestCommandApp("Test Command", "org.beeware.widgets.command")
 
 
diff --git a/examples/date_and_time/date_and_time/app.py b/examples/date_and_time/date_and_time/app.py
index 6bc5419b8d..3942581b06 100644
--- a/examples/date_and_time/date_and_time/app.py
+++ b/examples/date_and_time/date_and_time/app.py
@@ -13,7 +13,7 @@ def changed_time(self, widget):
         print(f"{widget.id} is {widget.value.strftime('%I:%M:%S %p')}")
 
     def startup(self):
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         any_date_box = toga.Box(
             children=[
diff --git a/examples/detailedlist/detailedlist/app.py b/examples/detailedlist/detailedlist/app.py
index 3e2a3bd8e4..7cc0500c2e 100644
--- a/examples/detailedlist/detailedlist/app.py
+++ b/examples/detailedlist/detailedlist/app.py
@@ -57,7 +57,7 @@ def remove_handler(self, widget, **kwargs):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # Buttons
         btn_style = Pack(flex=1, padding=10)
diff --git a/examples/dialogs/dialogs/app.py b/examples/dialogs/dialogs/app.py
index 8286b064f2..7f827ba900 100644
--- a/examples/dialogs/dialogs/app.py
+++ b/examples/dialogs/dialogs/app.py
@@ -181,8 +181,6 @@ async def window_close_handler(self, window):
     def action_open_secondary_window(self, widget):
         self.window_counter += 1
         window = toga.Window(title=f"New Window {self.window_counter}")
-        # Both self.windows.add() and self.windows += work:
-        self.windows += window
 
         self.set_window_label_text(len(self.windows) - 1)
         secondary_label = toga.Label(text="You are in a secondary window!")
@@ -214,7 +212,7 @@ def set_window_label_text(self, num_windows):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
         self.on_exit = self.exit_handler
 
         # Label to show responses.
diff --git a/examples/divider/divider/app.py b/examples/divider/divider/app.py
index 48bd09cf8b..71cd0cc6e2 100644
--- a/examples/divider/divider/app.py
+++ b/examples/divider/divider/app.py
@@ -5,9 +5,7 @@
 
 class DividerApp(toga.App):
     def startup(self):
-        # Window class
-        #   Main window of the application with title and size
-        self.main_window = toga.MainWindow(title=self.name, size=(300, 150))
+        self.main_window = toga.MainWindow(size=(300, 150))
 
         style = Pack(padding_top=24)
         substyle = Pack(padding_right=12, padding_left=12, flex=1)
diff --git a/examples/documentapp/Ironbark.exampledoc b/examples/documentapp/Ironbark.exampledoc
new file mode 100644
index 0000000000..b76fa61f1b
--- /dev/null
+++ b/examples/documentapp/Ironbark.exampledoc
@@ -0,0 +1,58 @@
+The Man from Ironbark
+=====================
+
+It was the man from Ironbark who struck the Sydney town,
+He wandered over street and park, he wandered up and down.
+He loitered here, he loitered there, till he was like to drop,
+Until at last in sheer despair he sought a barber's shop.
+"'Ere! shave my beard and whiskers off, I'll be a man of mark,
+I'll go and do the Sydney toff up home in Ironbark."
+
+The barber man was small and flash, as barbers mostly are,
+He wore a strike-your-fancy sash, he smoked a huge cigar;
+He was a humorist of note and keen at repartee,
+He laid the odds and kept a "tote", whatever that may be,
+And when he saw our friend arrive, he whispered, "Here's a lark!
+Just watch me catch him all alive, this man from Ironbark."
+
+There were some gilded youths that sat along the barber's wall.
+Their eyes were dull, their heads were flat, they had no brains at all;
+To them the barber passed the wink, his dexter eyelid shut,
+"I'll make this bloomin' yokel think his bloomin' throat is cut."
+And as he soaped and rubbed it in he made a rude remark:
+"I s'pose the flats is pretty green up there in Ironbark."
+
+A grunt was all reply he got; he shaved the bushman's chin,
+Then made the water boiling hot and dipped the razor in.
+He raised his hand, his brow grew black, he paused awhile to gloat,
+Then slashed the red-hot razor-back across his victim's throat:
+Upon the newly-shaven skin it made a livid mark -
+No doubt it fairly took him in - the man from Ironbark.
+
+He fetched a wild up-country yell might wake the dead to hear,
+And though his throat, he knew full well, was cut from ear to ear,
+He struggled gamely to his feet, and faced the murd'rous foe:
+"You've done for me! you dog, I'm beat! one hit before I go!
+I only wish I had a knife, you blessed murdering shark!
+But you'll remember all your life the man from Ironbark."
+
+He lifted up his hairy paw, with one tremendous clout
+He landed on the barber's jaw, and knocked the barber out.
+He set to work with nail and tooth, he made the place a wreck;
+He grabbed the nearest gilded youth, and tried to break his neck.
+And all the while his throat he held to save his vital spark,
+And "Murder! Bloody murder!" yelled the man from Ironbark.
+
+A peeler man who heard the din came in to see the show;
+He tried to run the bushman in, but he refused to go.
+And when at last the barber spoke, and said "'Twas all in fun—
+'Twas just a little harmless joke, a trifle overdone."
+"A joke!" he cried, "By George, that's fine; a lively sort of lark;
+I'd like to catch that murdering swine some night in Ironbark."
+
+And now while round the shearing floor the list'ning shearers gape,
+He tells the story o'er and o'er, and brags of his escape.
+"Them barber chaps what keeps a tote, By George, I've had enough,
+One tried to cut my bloomin' throat, but thank the Lord it's tough."
+And whether he's believed or no, there's one thing to remark,
+That flowing beards are all the go way up in Ironbark.
diff --git a/examples/documentapp/Jabberwocky.exampledoc b/examples/documentapp/Jabberwocky.exampledoc
new file mode 100644
index 0000000000..dfbec58ec1
--- /dev/null
+++ b/examples/documentapp/Jabberwocky.exampledoc
@@ -0,0 +1,37 @@
+Jabberwocky
+===========
+
+'Twas brillig, and the slithy toves
+Did gyre and gimble in the wabe;
+All mimsy were the borogoves,
+And the mome raths outgrabe.
+
+"Beware the Jabberwock, my son!
+The jaws that bite, the claws that catch!
+Beware the Jubjub bird, and shun
+The frumious Bandersnatch!"
+
+He took his vorpal sword in hand:
+Long time the manxome foe he sought—
+So rested he by the Tumtum tree,
+And stood awhile in thought.
+
+And as in uffish thought he stood,
+The Jabberwock, with eyes of flame,
+Came whiffling through the tulgey wood,
+And burbled as it came!
+
+One, two! One, two! And through and through
+The vorpal blade went snicker-snack!
+He left it dead, and with its head
+He went galumphing back.
+
+"And hast thou slain the Jabberwock?
+Come to my arms, my beamish boy!
+O frabjous day! Callooh! Callay!"
+He chortled in his joy.
+
+'Twas brillig, and the slithy toves
+Did gyre and gimble in the wabe;
+All mimsy were the borogoves,
+And the mome raths outgrabe.
diff --git a/examples/documentapp/README.rst b/examples/documentapp/README.rst
new file mode 100644
index 0000000000..b6be1485e7
--- /dev/null
+++ b/examples/documentapp/README.rst
@@ -0,0 +1,16 @@
+DocumentApp
+===========
+
+An example DocumentApp.
+
+Quickstart
+~~~~~~~~~~
+
+To run this example:
+
+    $ pip install toga
+    $ python -m documentapp
+
+Or, pass in a file at the command line
+
+    $ python -m documentapp Jabberwocky.exampledoc
diff --git a/examples/documentapp/documentapp/__init__.py b/examples/documentapp/documentapp/__init__.py
new file mode 100644
index 0000000000..86826e638c
--- /dev/null
+++ b/examples/documentapp/documentapp/__init__.py
@@ -0,0 +1,9 @@
+# Examples of valid version strings
+# __version__ = '1.2.3.dev1'  # Development release 1
+# __version__ = '1.2.3a1'     # Alpha Release 1
+# __version__ = '1.2.3b1'     # Beta Release 1
+# __version__ = '1.2.3rc1'    # RC Release 1
+# __version__ = '1.2.3'       # Final Release
+# __version__ = '1.2.3.post1' # Post Release 1
+
+__version__ = "0.0.1"
diff --git a/examples/documentapp/documentapp/__main__.py b/examples/documentapp/documentapp/__main__.py
new file mode 100644
index 0000000000..974a50572c
--- /dev/null
+++ b/examples/documentapp/documentapp/__main__.py
@@ -0,0 +1,4 @@
+from documentapp.app import main
+
+if __name__ == "__main__":
+    main().main_loop()
diff --git a/examples/documentapp/documentapp/app.py b/examples/documentapp/documentapp/app.py
new file mode 100644
index 0000000000..6cbb733bd9
--- /dev/null
+++ b/examples/documentapp/documentapp/app.py
@@ -0,0 +1,41 @@
+import toga
+
+
+class ExampleDocument(toga.Document):
+    def __init__(self, path, app):
+        super().__init__(path=path, document_type="Example Document", app=app)
+
+    async def can_close(self):
+        return await self.main_window.question_dialog(
+            "Are you sure?",
+            "Do you want to close this document?",
+        )
+
+    def create(self):
+        # Create the main window for the document.
+        self.main_window = toga.DocumentMainWindow(
+            doc=self,
+            title=f"Example: {self.path.name}",
+        )
+        self.main_window.content = toga.MultilineTextInput()
+
+    def read(self):
+        with self.path.open() as f:
+            self.content = f.read()
+
+        self.main_window.content.value = self.content
+
+
+def main():
+    return toga.DocumentApp(
+        "Document App",
+        "org.beeware.widgets.documentapp",
+        document_types={
+            "exampledoc": ExampleDocument,
+        },
+    )
+
+
+if __name__ == "__main__":
+    app = main()
+    app.main_loop()
diff --git a/examples/documentapp/documentapp/resources/README b/examples/documentapp/documentapp/resources/README
new file mode 100644
index 0000000000..84f0abfa08
--- /dev/null
+++ b/examples/documentapp/documentapp/resources/README
@@ -0,0 +1 @@
+Put any icons or images in this directory.
diff --git a/examples/documentapp/pyproject.toml b/examples/documentapp/pyproject.toml
new file mode 100644
index 0000000000..204f699deb
--- /dev/null
+++ b/examples/documentapp/pyproject.toml
@@ -0,0 +1,55 @@
+[build-system]
+requires = ["briefcase"]
+
+[tool.briefcase]
+project_name = "Document App"
+bundle = "org.beeware"
+version = "0.0.1"
+url = "https://beeware.org"
+license = "BSD license"
+author = "Tiberius Yak"
+author_email = "tiberius@beeware.org"
+
+[tool.briefcase.app.documentapp]
+formal_name = "Document App"
+description = "A testing app"
+sources = ["documentapp"]
+requires = [
+    "../../core",
+]
+
+
+[tool.briefcase.app.documentapp.macOS]
+requires = [
+    "../../cocoa",
+    "std-nslog>=1.0.0",
+]
+
+[tool.briefcase.app.documentapp.linux]
+requires = [
+    "../../gtk",
+]
+
+[tool.briefcase.app.documentapp.windows]
+requires = [
+    "../../winforms",
+]
+
+# Mobile deployments
+[tool.briefcase.app.documentapp.iOS]
+requires = [
+    "../../iOS",
+    "std-nslog>=1.0.0",
+]
+
+[tool.briefcase.app.documentapp.android]
+requires = [
+    "../../android",
+]
+
+# Web deployment
+[tool.briefcase.app.documentapp.web]
+requires = [
+    "../../web",
+]
+style_framework = "Shoelace v2.3"
diff --git a/examples/examples_overview/examples_overview/app.py b/examples/examples_overview/examples_overview/app.py
index 279fb68143..5ae3d18e44 100644
--- a/examples/examples_overview/examples_overview/app.py
+++ b/examples/examples_overview/examples_overview/app.py
@@ -8,7 +8,7 @@
 from toga.constants import COLUMN
 from toga.style import Pack
 
-examples_dir = Path(__file__).parents[3]
+examples_dir = Path(__file__).parents[2]
 
 
 class ExampleExamplesOverviewApp(toga.App):
@@ -31,8 +31,8 @@ def open(self, widget, **kwargs):
         else:
             subprocess.run(["xdg-open", row.path])
 
-    def on_example_selected(self, widget, row):
-        readme_path = row.path / "README.rst"
+    def on_example_selected(self, widget):
+        readme_path = widget.selection.path / "README.rst"
 
         try:
             with open(readme_path) as f:
@@ -45,7 +45,7 @@ def on_example_selected(self, widget, row):
     def startup(self):
         # ==== Set up main window ======================================================
 
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # Label for user instructions
         label = toga.Label(
@@ -60,7 +60,7 @@ def startup(self):
         # search for all folders that contain modules
         for root, dirs, files in os.walk(examples_dir):
             # skip hidden folders
-            dirs[:] = [d for d in dirs if not d.startswith(".")]
+            dirs[:] = [d for d in dirs if not d.startswith(".") and d != "build"]
             if any(name == "__main__.py" for name in files):
                 path = Path(root)
                 self.examples.append(dict(name=path.name, path=path.parent))
@@ -70,7 +70,7 @@ def startup(self):
         self.table = toga.Table(
             headings=["Name", "Path"],
             data=self.examples,
-            on_double_click=self.run,
+            on_activate=self.run,
             on_select=self.on_example_selected,
             style=Pack(padding_bottom=10, flex=1),
         )
@@ -102,11 +102,14 @@ def startup(self):
             ),
         )
 
-        split_container = toga.SplitContainer(content=[left_box, self.info_view])
+        split_container = toga.SplitContainer(
+            content=[left_box, self.info_view],
+            style=Pack(flex=1),
+        )
 
         outer_box = toga.Box(
             children=[label, split_container],
-            style=Pack(padding=10, direction=COLUMN),
+            style=Pack(padding=10, direction=COLUMN, flex=1),
         )
 
         # Add the content on the main window
diff --git a/examples/focus/focus/app.py b/examples/focus/focus/app.py
index ad2adf46e4..242209bcdd 100644
--- a/examples/focus/focus/app.py
+++ b/examples/focus/focus/app.py
@@ -11,11 +11,8 @@
 
 class ExampleFocusApp(toga.App):
     def startup(self):
-        # Window class
-        #   Main window of the application with title and size
-        #   Also make the window non-resizable and non-minimizable.
         self.main_window = toga.MainWindow(
-            title=self.name, size=(800, 500), resizeable=False, minimizable=False
+            size=(800, 500), resizable=False, minimizable=False
         )
 
         self.a_button = toga.Button("A", on_press=self.on_button_press)
@@ -112,12 +109,12 @@ def on_switch_toggle(self, widget: toga.Switch):
         on_off = "on" if widget.value else "off"
         self.info_label.text = f"Switch turned {on_off}!"
 
-    def on_textinput_gain_focus(self, widget: toga.TextInput):
+    def on_textinput_gain_focus(self, widget: toga.TextInput, **kwargs):
         self.info_label.text = "TextInput has previously had focus " "{} times".format(
             self.text_input_focus_count
         )
 
-    def on_textinput_lose_focus(self, widget: toga.TextInput):
+    def on_textinput_lose_focus(self, widget: toga.TextInput, **kwargs):
         self.text_input_focus_count += 1
 
     def focus_with_label(self, widget: toga.Widget):
diff --git a/examples/font/font/app.py b/examples/font/font/app.py
index be9b87c677..b2a7b047ed 100644
--- a/examples/font/font/app.py
+++ b/examples/font/font/app.py
@@ -37,7 +37,7 @@ def do_add_content(self, widget, **kwargs):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # register fonts
         toga.Font.register(
diff --git a/examples/handlers/handlers/app.py b/examples/handlers/handlers/app.py
index d0bb4dfaa4..c92d6f1de3 100644
--- a/examples/handlers/handlers/app.py
+++ b/examples/handlers/handlers/app.py
@@ -54,7 +54,7 @@ async def do_background_task(self, widget, **kwargs):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # Labels to show responses.
         self.label = toga.Label("Ready.", style=Pack(padding=10))
diff --git a/examples/imageview/imageview/app.py b/examples/imageview/imageview/app.py
index 655baca80e..55792b4b4f 100644
--- a/examples/imageview/imageview/app.py
+++ b/examples/imageview/imageview/app.py
@@ -8,7 +8,7 @@
 
 class ImageViewApp(toga.App):
     def startup(self):
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         box = toga.Box(
             style=Pack(
diff --git a/examples/multilinetextinput/multilinetextinput/app.py b/examples/multilinetextinput/multilinetextinput/app.py
index 3648f4475f..83232df9a9 100644
--- a/examples/multilinetextinput/multilinetextinput/app.py
+++ b/examples/multilinetextinput/multilinetextinput/app.py
@@ -33,7 +33,7 @@ def set_label(self, widget):
         self.label.text = f"{number_of_lines} lines have been written"
 
     def startup(self):
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         self.multiline_input = toga.MultilineTextInput(
             placeholder="Enter text here...",
diff --git a/examples/numberinput/numberinput/app.py b/examples/numberinput/numberinput/app.py
index 0c8e52ccf7..1339681c27 100644
--- a/examples/numberinput/numberinput/app.py
+++ b/examples/numberinput/numberinput/app.py
@@ -20,22 +20,22 @@ def on_change(self, widget):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # Label to show responses.
         self.label = toga.Label("Ready.")
         label1 = toga.Label("Enter value from -12 to 72:")
         self.input1 = toga.NumberInput(
-            min_value=-12,
-            max_value=72,
+            min=-12,
+            max=72,
             step=2,
             value=37,
             on_change=self.on_change,
         )
         label2 = toga.Label("Enter value from 1.2 to 7.2:")
         self.input2 = toga.NumberInput(
-            min_value=1.2,
-            max_value=7.2,
+            min=1.2,
+            max=7.2,
             step=0.1,
             value=3.7,
             on_change=self.on_change,
diff --git a/examples/optioncontainer/optioncontainer/app.py b/examples/optioncontainer/optioncontainer/app.py
index 7e521aecc8..bc6de7add0 100644
--- a/examples/optioncontainer/optioncontainer/app.py
+++ b/examples/optioncontainer/optioncontainer/app.py
@@ -82,7 +82,7 @@ def on_select_tab(self, widget, **kwargs):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # styles
         style_flex = Pack(flex=1, padding=5)
diff --git a/examples/passwordinput/passwordinput/app.py b/examples/passwordinput/passwordinput/app.py
index 595bda9f70..b0fc62a640 100644
--- a/examples/passwordinput/passwordinput/app.py
+++ b/examples/passwordinput/passwordinput/app.py
@@ -30,7 +30,7 @@ def get_password_content_label(self, content):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
         PADDING = 5
         # Label to show responses.
         self.label = toga.Label("Testing Password")
diff --git a/examples/positron-django/src/positron/app.py b/examples/positron-django/src/positron/app.py
index 64941f1536..8288d6dc26 100644
--- a/examples/positron-django/src/positron/app.py
+++ b/examples/positron-django/src/positron/app.py
@@ -50,7 +50,7 @@ def startup(self):
         host, port = self._httpd.socket.getsockname()
         self.web_view.url = f"http://{host}:{port}/"
 
-        self.main_window = toga.MainWindow(title=self.formal_name)
+        self.main_window = toga.MainWindow()
         self.main_window.content = self.web_view
         self.main_window.show()
 
diff --git a/examples/positron-static/src/positron/app.py b/examples/positron-static/src/positron/app.py
index 06a2f14617..8150d80e5a 100644
--- a/examples/positron-static/src/positron/app.py
+++ b/examples/positron-static/src/positron/app.py
@@ -44,7 +44,7 @@ def startup(self):
         host, port = self._httpd.socket.getsockname()
         self.web_view.url = f"http://{host}:{port}/"
 
-        self.main_window = toga.MainWindow(title=self.formal_name)
+        self.main_window = toga.MainWindow()
         self.main_window.content = self.web_view
         self.main_window.show()
 
diff --git a/examples/progressbar/progressbar/app.py b/examples/progressbar/progressbar/app.py
index c7ed8d8e28..d98b3400ac 100644
--- a/examples/progressbar/progressbar/app.py
+++ b/examples/progressbar/progressbar/app.py
@@ -9,8 +9,7 @@
 
 class ProgressBarApp(toga.App):
     def startup(self):
-        # Main window of the application with title and size
-        self.main_window = toga.MainWindow(title=self.name, size=(500, 500))
+        self.main_window = toga.MainWindow(size=(500, 500))
 
         # the user may change the value with +/- buttons
         self.progress_adder = toga.ProgressBar(max=MAX_PROGRESSBAR_VALUE)
diff --git a/examples/screenshot/README.rst b/examples/screenshot/README.rst
new file mode 100644
index 0000000000..4e0fc4dde6
--- /dev/null
+++ b/examples/screenshot/README.rst
@@ -0,0 +1,12 @@
+Screenshot Generator
+====================
+
+Test app for the Screenshot Generator widget.
+
+Quickstart
+~~~~~~~~~~
+
+To run this example:
+
+    $ pip install toga
+    $ python -m screenshot
diff --git a/examples/screenshot/pyproject.toml b/examples/screenshot/pyproject.toml
new file mode 100644
index 0000000000..63c7f965ca
--- /dev/null
+++ b/examples/screenshot/pyproject.toml
@@ -0,0 +1,49 @@
+[build-system]
+requires = ["briefcase"]
+
+[tool.briefcase]
+project_name = "Screenshot Generator"
+bundle = "org.beeware"
+version = "0.0.1"
+url = "https://beeware.org"
+license = "BSD license"
+author = "Tiberius Yak"
+author_email = "tiberius@beeware.org"
+
+[tool.briefcase.app.screenshot]
+formal_name = "Screenshot Generator"
+description = "A testing app"
+sources = ["screenshot"]
+requires = [
+    "../../core",
+    "pillow",
+]
+
+
+[tool.briefcase.app.screenshot.macOS]
+requires = [
+    "../../cocoa",
+    "std-nslog>=1.0.0",
+]
+
+[tool.briefcase.app.screenshot.linux]
+requires = [
+    "../../gtk",
+]
+
+[tool.briefcase.app.screenshot.windows]
+requires = [
+    "../../winforms",
+]
+
+# Mobile deployments
+[tool.briefcase.app.screenshot.iOS]
+requires = [
+    "../../iOS",
+    "std-nslog>=1.0.0",
+]
+
+[tool.briefcase.app.screenshot.android]
+requires = [
+    "../../android",
+]
diff --git a/examples/screenshot/screenshot/__init__.py b/examples/screenshot/screenshot/__init__.py
new file mode 100644
index 0000000000..86826e638c
--- /dev/null
+++ b/examples/screenshot/screenshot/__init__.py
@@ -0,0 +1,9 @@
+# Examples of valid version strings
+# __version__ = '1.2.3.dev1'  # Development release 1
+# __version__ = '1.2.3a1'     # Alpha Release 1
+# __version__ = '1.2.3b1'     # Beta Release 1
+# __version__ = '1.2.3rc1'    # RC Release 1
+# __version__ = '1.2.3'       # Final Release
+# __version__ = '1.2.3.post1' # Post Release 1
+
+__version__ = "0.0.1"
diff --git a/examples/screenshot/screenshot/__main__.py b/examples/screenshot/screenshot/__main__.py
new file mode 100644
index 0000000000..1dfc6569a0
--- /dev/null
+++ b/examples/screenshot/screenshot/__main__.py
@@ -0,0 +1,4 @@
+from screenshot.app import main
+
+if __name__ == "__main__":
+    main().main_loop()
diff --git a/examples/screenshot/screenshot/app.py b/examples/screenshot/screenshot/app.py
new file mode 100644
index 0000000000..b14d592bb7
--- /dev/null
+++ b/examples/screenshot/screenshot/app.py
@@ -0,0 +1,486 @@
+import asyncio
+from datetime import date, time
+from io import BytesIO
+
+from PIL import Image
+
+import toga
+from toga.constants import CENTER, COLUMN
+from toga.style import Pack
+
+from .canvas import draw_tiberius
+
+
+class ScreenshotGeneratorApp(toga.App):
+    def create_activityindicator(self):
+        return toga.Box(
+            children=[
+                toga.Box(style=Pack(flex=1)),
+                toga.ActivityIndicator(running=True, style=Pack(padding=10)),
+                toga.Box(style=Pack(flex=1)),
+            ],
+            style=Pack(width=100),
+        )
+
+    def create_button(self):
+        return toga.Box(
+            children=[
+                toga.Button(
+                    "Launch rocket",
+                    style=Pack(padding=10, flex=1),
+                )
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_canvas(self):
+        canvas = toga.Canvas(style=Pack(padding=10, width=280, height=290))
+        draw_tiberius(canvas)
+
+        return toga.Box(children=[canvas], style=Pack(width=280, height=290))
+
+    def create_dateinput(self):
+        return toga.Box(
+            children=[
+                toga.Box(style=Pack(flex=1)),
+                toga.DateInput(value=date(2014, 4, 21), style=Pack(padding=10)),
+                toga.Box(style=Pack(flex=1)),
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_detailedlist(self):
+        brutus_icon = toga.Icon("resources/brutus.png")
+        user_icon = toga.Icon("resources/user.png")
+        return toga.DetailedList(
+            data=[
+                {
+                    "icon": brutus_icon,
+                    "title": "Brutus",
+                    "subtitle": "Are you the very model of a modern major general?",
+                },
+                {
+                    "icon": user_icon,
+                    "title": "Major General",
+                    "subtitle": "I have information animal, mineral, and vegetable...",
+                },
+                {
+                    "icon": brutus_icon,
+                    "title": "Brutus",
+                    "subtitle": "Ah - but do you know the kings of England?",
+                },
+                {
+                    "icon": user_icon,
+                    "title": "Major General",
+                    "subtitle": "I can quote the fights historical!",
+                },
+            ],
+            style=Pack(padding=10, width=self.MAX_WIDTH, height=300),
+        )
+
+    def create_divider(self):
+        return toga.Box(
+            children=[
+                toga.Label(
+                    "I'm on top", style=Pack(flex=1, padding=5, text_align=CENTER)
+                ),
+                toga.Divider(direction=toga.Divider.HORIZONTAL, style=Pack(padding=5)),
+                toga.Label(
+                    "I'm below", style=Pack(flex=1, padding=5, text_align=CENTER)
+                ),
+            ],
+            style=Pack(width=300, direction=COLUMN),
+        )
+
+    def create_label(self):
+        return toga.Box(
+            children=[
+                toga.Label(
+                    "Brutus was here!",
+                    style=Pack(padding=10, text_align=CENTER, flex=1),
+                )
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_multilinetextinput(self):
+        return toga.MultilineTextInput(
+            value="\n".join(
+                [
+                    "I am the very model of a modern Major-General.",
+                    "I've information animal, mineral, and vegetable.",
+                    "I know the kings of England, and I quote the fights historical",
+                    "From Marathon to Waterloo, in order categorical.",
+                    "I'm very well acquainted, too, with matters mathematical,",
+                    "I understand equations, both the simple and quadratical,",
+                    "About binomial theorem I'm teeming with a lot o' news,",
+                    "With many cheerful facts about the square of the hypotenuse.",
+                    "",
+                    "I'm very good at integral and differential calculus;",
+                    "I know the scientific names of beings animalculous:",
+                    "In short, in matters vegetable, animal, and mineral,",
+                    "I am the very model of a modern Major-General.",
+                ]
+            ),
+            style=Pack(padding=10, width=self.MAX_WIDTH, height=200),
+        )
+
+    def create_numberinput(self):
+        return toga.Box(
+            children=[
+                toga.NumberInput(
+                    value=2.71818,
+                    step=0.00001,
+                    style=Pack(padding=10, flex=1),
+                )
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_passwordinput(self):
+        return toga.Box(
+            children=[
+                toga.PasswordInput(
+                    value="secret",
+                    style=Pack(padding=10, flex=1),
+                )
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_progressbar(self):
+        return toga.Box(
+            children=[
+                toga.ProgressBar(
+                    value=42,
+                    max=100,
+                    style=Pack(padding=10, flex=1),
+                )
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_selection(self):
+        return toga.Box(
+            children=[
+                toga.Selection(
+                    items=["Titanium", "Yttrium", "Yterbium"],
+                    style=Pack(padding=10, flex=1),
+                )
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_slider(self):
+        return toga.Box(
+            children=[
+                toga.Slider(
+                    value=42,
+                    max=100,
+                    style=Pack(padding=10, flex=1),
+                )
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_switch(self):
+        return toga.Box(
+            children=[
+                toga.Box(style=Pack(flex=1)),
+                toga.Switch(
+                    "Turbo",
+                    value=True,
+                    style=Pack(padding=10),
+                ),
+                toga.Box(style=Pack(flex=1)),
+            ],
+            style=Pack(width=150),
+        )
+
+    def create_table(self):
+        return toga.Table(
+            headings=["Name", "Age", "Planet"],
+            data=[
+                ("Arthur Dent", 42, "Earth"),
+                ("Ford Prefect", 37, "Betelgeuse Five"),
+                ("Tricia McMillan", 38, "Earth"),
+                ("Slartibartfast", 1005, "Magrathea"),
+            ],
+            style=Pack(padding=10, width=self.MAX_WIDTH, height=200),
+        )
+
+    def create_textinput(self):
+        return toga.Box(
+            children=[
+                toga.TextInput(
+                    value="Brutus was here!",
+                    style=Pack(padding=10, flex=1),
+                )
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_timeinput(self):
+        return toga.Box(
+            children=[
+                toga.Box(style=Pack(flex=1)),
+                toga.TimeInput(value=time(9, 7, 37), style=Pack(padding=10)),
+                toga.Box(style=Pack(flex=1)),
+            ],
+            style=Pack(width=300),
+        )
+
+    def create_tree(self):
+        tree = toga.Tree(
+            headings=["Name", "Age", "Status"],
+            data={
+                "Earth": {
+                    ("Arthur Dent", 42, "Anxious"): None,
+                    ("Tricia McMillan", 38, "Overqualified"): None,
+                },
+                "Betelgeuse Five": {
+                    ("Ford Prefect", 37, "Hoopy"): None,
+                },
+                "Magrathea": {
+                    ("Slartibartfast", 1005, "Annoyed"): None,
+                },
+            },
+            style=Pack(padding=10, width=self.MAX_WIDTH, height=200),
+        )
+        tree.expand()
+        return tree
+
+    def create_webview(self):
+        return toga.WebView(
+            url="https://beeware.org",
+            style=Pack(padding=10, width=self.MAX_WIDTH, height=300),
+        )
+
+    def create_optioncontainer(self):
+        container = toga.OptionContainer(
+            content=[
+                (
+                    "Blue",
+                    toga.Box(style=Pack(background_color="cornflowerblue")),
+                ),
+                ("Green", toga.Box()),
+                ("Red", toga.Box()),
+            ],
+            style=Pack(padding=10, width=self.MAX_WIDTH, height=300),
+        )
+
+        return container
+
+    def create_scrollcontainer(self):
+        container = toga.ScrollContainer(
+            content=toga.Box(
+                children=[
+                    toga.Box(
+                        style=Pack(
+                            background_color="cornflowerblue", width=900, height=600
+                        )
+                    ),
+                ],
+                style=Pack(direction=COLUMN),
+            ),
+            style=Pack(padding=10, width=self.MAX_WIDTH, height=300),
+        )
+
+        return container
+
+    def create_splitcontainer(self):
+        container = toga.SplitContainer(
+            content=[
+                toga.Box(style=Pack(background_color="goldenrod")),
+                toga.Box(style=Pack(background_color="cornflowerblue")),
+            ],
+            style=Pack(padding=10, width=self.MAX_WIDTH, height=300),
+        )
+
+        return container
+
+    def create_window(self):
+        if toga.platform.current_platform in {"iOS", "android"}:
+            return None
+
+        return toga.Window(title="Toga", position=(800, 200), size=(300, 250))
+
+    def create_main_window(self):
+        # No widget to create
+        return True
+
+    async def manual_screenshot(self, content=None):
+        loop = asyncio.get_event_loop()
+        future = loop.create_future()
+
+        def proceed(button, **kwargs):
+            future.set_result(True)
+
+        proceed_button = toga.Button(
+            "Done",
+            on_press=proceed,
+            style=Pack(padding=10),
+        )
+
+        if content:
+            self.main_window.content = toga.Box(
+                children=[
+                    content,
+                    toga.Box(style=Pack(flex=1)),
+                    proceed_button,
+                ],
+                style=Pack(direction=COLUMN),
+            )
+        else:
+            self.main_window.content = toga.Box()
+        await future
+
+    async def sequence(self, app, **kwargs):
+        print(f"Saving screenshots to {self.app.paths.data}")
+        self.app.paths.data.mkdir(parents=True, exist_ok=True)
+        for content_type in [
+            "activityindicator",
+            "button",
+            "canvas",
+            "dateinput",
+            "detailedlist",
+            "divider",
+            "label",
+            "multilinetextinput",
+            "numberinput",
+            "passwordinput",
+            "progressbar",
+            "selection",
+            "slider",
+            "switch",
+            "table",
+            "textinput",
+            "timeinput",
+            "tree",
+            "webview",
+            "optioncontainer",
+            "scrollcontainer",
+            "splitcontainer",
+            "window",
+            "main_window",
+        ]:
+            try:
+                content = getattr(self.app, f"create_{content_type}")()
+                if content:
+                    if content_type == "main_window":
+                        # image = self.main_window.screen.as_image()
+                        # cropped = image.crop(... crop to window size ...)
+                        #
+                        # TODO: Crop the desktop image, rather than use a manual screenshot
+                        await self.main_window.info_dialog(
+                            "Manual intervention",
+                            "Screenshot the main window, and then quit the app.",
+                        )
+                        self.main_window.toolbar.add(self.command2, self.command1)
+                        self.main_window.content = toga.Box()
+
+                        cropped = None
+                    elif content_type == "window":
+                        content.show()
+
+                        # image = self.main_window.screen.as_image()
+                        # cropped = image.crop(... crop to window size ...)
+                        #
+                        # TODO: Crop the desktop image, rather than use a manual screenshot
+                        await self.main_window.info_dialog(
+                            "Manual intervention",
+                            "Screenshot the secondary window, then press Done.",
+                        )
+                        await self.manual_screenshot(toga.Box())
+                        cropped = None
+
+                        content.close()
+
+                    elif (
+                        content_type == "webview"
+                        and toga.platform.current_platform == "macOS"
+                    ):
+                        # Manual screenshot required on macOS because webviews aren't
+                        # rendered directly on the Window.
+                        await self.main_window.info_dialog(
+                            "Manual intervention",
+                            "Screenshot the web widget content, then press Done.",
+                        )
+                        await self.manual_screenshot(content)
+                        cropped = None
+                    else:
+                        self.main_window.content = toga.Box(
+                            children=[content],
+                            style=Pack(direction=COLUMN),
+                        )
+
+                        await asyncio.sleep(
+                            {
+                                "webview": 4,
+                            }.get(content_type, 2)
+                        )
+                        image = Image.open(BytesIO(self.main_window.as_image().data))
+
+                        scale_x = (
+                            image.size[0]
+                            / self.main_window.content.layout.content_width
+                        )
+                        scale_y = (
+                            image.size[1]
+                            / self.main_window.content.layout.content_height
+                        )
+
+                        cropped = image.crop(
+                            (
+                                0,
+                                0,
+                                (content.layout.content_width + 20) * scale_x,
+                                (content.layout.content_height + 20) * scale_y,
+                            )
+                        )
+
+                    if cropped:
+                        cropped.save(
+                            self.app.paths.data
+                            / f"{content_type}-{toga.platform.current_platform}.png"
+                        )
+
+            except NotImplementedError:
+                pass
+
+    def startup(self):
+        if toga.platform.current_platform in {"iOS", "android"}:
+            self.MAX_WIDTH = 370
+        else:
+            self.MAX_WIDTH = 450
+
+        # Set up main window
+        self.main_window = toga.MainWindow(title="My Application")
+
+        self.command1 = toga.Command(
+            lambda _: None,
+            text="Twist",
+            icon=toga.Icon.DEFAULT_ICON,
+        )
+        self.command2 = toga.Command(
+            lambda _: None,
+            text="Shout",
+            icon="resources/brutus",
+        )
+
+        # Add the content on the main window
+        self.main_window.content = toga.Box()
+
+        # Show the main window
+        self.main_window.show()
+
+        self.add_background_task(self.sequence)
+
+
+def main():
+    return ScreenshotGeneratorApp("My Application", "org.beeware.widgets.screenshot")
+
+
+if __name__ == "__main__":
+    app = main()
+    app.main_loop()
diff --git a/examples/screenshot/screenshot/canvas.py b/examples/screenshot/screenshot/canvas.py
new file mode 100644
index 0000000000..245e22042a
--- /dev/null
+++ b/examples/screenshot/screenshot/canvas.py
@@ -0,0 +1,103 @@
+import math
+
+from toga.colors import REBECCAPURPLE, WHITE, rgb
+from toga.constants import Baseline
+from toga.fonts import SANS_SERIF, Font
+
+
+def fill_head(canvas):
+    with canvas.Fill(color=rgb(149, 119, 73)) as head_filler:
+        head_filler.move_to(112, 103)
+        head_filler.line_to(112, 113)
+        head_filler.ellipse(73, 114, 39, 47, 0, 0, math.pi)
+        head_filler.line_to(35, 84)
+        head_filler.arc(65, 84, 30, math.pi, 3 * math.pi / 2)
+        head_filler.arc(82, 84, 30, 3 * math.pi / 2, 2 * math.pi)
+
+
+def stroke_head(canvas):
+    with canvas.Stroke(line_width=4.0) as head_stroker:
+        with head_stroker.ClosedPath(112, 103) as closed_head:
+            closed_head.line_to(112, 113)
+            closed_head.ellipse(73, 114, 39, 47, 0, 0, math.pi)
+            closed_head.line_to(35, 84)
+            closed_head.arc(65, 84, 30, math.pi, 3 * math.pi / 2)
+            closed_head.arc(82, 84, 30, 3 * math.pi / 2, 2 * math.pi)
+
+
+def draw_eyes(canvas):
+    with canvas.Fill(color=WHITE) as eye_whites:
+        eye_whites.arc(58, 92, 15)
+        eye_whites.arc(88, 92, 15, math.pi, 3 * math.pi)
+
+    # Draw eyes separately to avoid miter join
+    with canvas.Stroke(line_width=4.0) as eye_outline:
+        eye_outline.arc(58, 92, 15)
+    with canvas.Stroke(line_width=4.0) as eye_outline:
+        eye_outline.arc(88, 92, 15, math.pi, 3 * math.pi)
+
+    with canvas.Fill() as eye_pupils:
+        eye_pupils.arc(58, 97, 3)
+        eye_pupils.arc(88, 97, 3)
+
+
+def draw_horns(canvas):
+    with canvas.Context() as r_horn:
+        with r_horn.Fill(color=rgb(212, 212, 212)) as r_horn_filler:
+            r_horn_filler.move_to(112, 99)
+            r_horn_filler.quadratic_curve_to(145, 65, 139, 36)
+            r_horn_filler.quadratic_curve_to(130, 60, 109, 75)
+        with r_horn.Stroke(line_width=4.0) as r_horn_stroker:
+            r_horn_stroker.move_to(112, 99)
+            r_horn_stroker.quadratic_curve_to(145, 65, 139, 36)
+            r_horn_stroker.quadratic_curve_to(130, 60, 109, 75)
+
+    with canvas.Context() as l_horn:
+        with l_horn.Fill(color=rgb(212, 212, 212)) as l_horn_filler:
+            l_horn_filler.move_to(35, 99)
+            l_horn_filler.quadratic_curve_to(2, 65, 6, 36)
+            l_horn_filler.quadratic_curve_to(17, 60, 37, 75)
+        with l_horn.Stroke(line_width=4.0) as l_horn_stroker:
+            l_horn_stroker.move_to(35, 99)
+            l_horn_stroker.quadratic_curve_to(2, 65, 6, 36)
+            l_horn_stroker.quadratic_curve_to(17, 60, 37, 75)
+
+
+def draw_nostrils(canvas):
+    with canvas.Fill(color=rgb(212, 212, 212)) as nose_filler:
+        nose_filler.move_to(45, 145)
+        nose_filler.bezier_curve_to(51, 123, 96, 123, 102, 145)
+        nose_filler.ellipse(73, 114, 39, 47, 0, math.pi / 4, 3 * math.pi / 4)
+    with canvas.Fill() as nostril_filler:
+        nostril_filler.arc(63, 140, 3)
+        nostril_filler.arc(83, 140, 3)
+    with canvas.Stroke(line_width=4.0) as nose_stroker:
+        nose_stroker.move_to(45, 145)
+        nose_stroker.bezier_curve_to(51, 123, 96, 123, 102, 145)
+
+
+def draw_text(canvas):
+    font = Font(family=SANS_SERIF, size=20)
+    text_width, text_height = canvas.measure_text("Tiberius", font)
+
+    x = (150 - text_width) // 2
+    y = 175
+
+    with canvas.Stroke(color=REBECCAPURPLE, line_width=4.0) as rect_stroker:
+        rect_stroker.rect(
+            x - 5,
+            y - 5,
+            text_width + 10,
+            text_height + 10,
+        )
+    with canvas.Fill(color=rgb(149, 119, 73)) as text_filler:
+        text_filler.write_text("Tiberius", x, y, font, Baseline.TOP)
+
+
+def draw_tiberius(canvas):
+    fill_head(canvas)
+    draw_eyes(canvas)
+    draw_horns(canvas)
+    draw_nostrils(canvas)
+    stroke_head(canvas)
+    draw_text(canvas)
diff --git a/examples/screenshot/screenshot/resources/README b/examples/screenshot/screenshot/resources/README
new file mode 100644
index 0000000000..84f0abfa08
--- /dev/null
+++ b/examples/screenshot/screenshot/resources/README
@@ -0,0 +1 @@
+Put any icons or images in this directory.
diff --git a/examples/screenshot/screenshot/resources/brutus.png b/examples/screenshot/screenshot/resources/brutus.png
new file mode 100644
index 0000000000..39184054eb
Binary files /dev/null and b/examples/screenshot/screenshot/resources/brutus.png differ
diff --git a/examples/screenshot/screenshot/resources/user.png b/examples/screenshot/screenshot/resources/user.png
new file mode 100644
index 0000000000..c8ca465165
Binary files /dev/null and b/examples/screenshot/screenshot/resources/user.png differ
diff --git a/examples/scrollcontainer/scrollcontainer/app.py b/examples/scrollcontainer/scrollcontainer/app.py
index 0a19513bf4..ac050b54a5 100644
--- a/examples/scrollcontainer/scrollcontainer/app.py
+++ b/examples/scrollcontainer/scrollcontainer/app.py
@@ -60,7 +60,7 @@ def startup(self):
         self.scroller.content = self.inner_box
         main_box.add(self.scroller)
 
-        self.main_window = toga.MainWindow(self.name, size=(400, 700))
+        self.main_window = toga.MainWindow(size=(400, 700))
         self.main_window.content = main_box
         self.main_window.show()
 
diff --git a/examples/selection/selection/app.py b/examples/selection/selection/app.py
index 573174fbb5..4d27ecf2df 100644
--- a/examples/selection/selection/app.py
+++ b/examples/selection/selection/app.py
@@ -15,8 +15,7 @@ class SelectionApp(toga.App):
     ]
 
     def startup(self):
-        # Main window of the application with title and size
-        self.main_window = toga.MainWindow(title=self.name, size=(640, 400))
+        self.main_window = toga.MainWindow(size=(640, 400))
 
         # set up common styles
         label_style = Pack(flex=1, padding_right=24)
diff --git a/examples/slider/slider/app.py b/examples/slider/slider/app.py
index fb311c62c3..d099da6d88 100644
--- a/examples/slider/slider/app.py
+++ b/examples/slider/slider/app.py
@@ -8,8 +8,7 @@
 
 class SliderApp(toga.App):
     def startup(self):
-        # Main window of the application with title and size
-        self.main_window = toga.MainWindow(title=self.name, size=(1000, 500))
+        self.main_window = toga.MainWindow(size=(1000, 500))
 
         # set up common styles
         label_style = Pack(flex=1, padding_right=24)
@@ -27,14 +26,16 @@ def startup(self):
         self.discrete_label = toga.Label("Discrete\n(with commands)", style=label_style)
         self.discrete_slider = toga.Slider(
             on_change=self.my_discrete_on_change,
-            range=(MIN_VAL, MAX_VAL),
+            min=MIN_VAL,
+            max=MAX_VAL,
             tick_count=MAX_VAL - MIN_VAL + 1,
             style=slider_style,
         )
 
         self.scared_label = toga.Label("Try to catch me!", style=label_style)
         self.scared_slider = toga.Slider(
-            range=(100, 300.5),
+            min=100,
+            max=300.5,
             value=123.4,
             on_press=self.scared_on_press,
             on_release=self.scared_on_release,
diff --git a/examples/splitcontainer/splitcontainer/app.py b/examples/splitcontainer/splitcontainer/app.py
index b12c5d2670..29bf3da358 100644
--- a/examples/splitcontainer/splitcontainer/app.py
+++ b/examples/splitcontainer/splitcontainer/app.py
@@ -90,7 +90,7 @@ def startup(self):
             ],
         )
 
-        self.main_window = toga.MainWindow(self.name)
+        self.main_window = toga.MainWindow()
         self.main_window.content = main_box
         self.main_window.show()
 
diff --git a/examples/switch_demo/switch_demo/app.py b/examples/switch_demo/switch_demo/app.py
index 673f19cc7c..a5ee5e5d4c 100644
--- a/examples/switch_demo/switch_demo/app.py
+++ b/examples/switch_demo/switch_demo/app.py
@@ -6,9 +6,7 @@
 
 class SwitchApp(toga.App):
     def startup(self):
-        # Window class
-        #   Main window of the application with title and size
-        self.main_window = toga.MainWindow(title=self.name, size=(350, 300))
+        self.main_window = toga.MainWindow(size=(350, 300))
 
         # Add the content on the main window
         self.main_window.content = toga.Box(
diff --git a/examples/table/table/app.py b/examples/table/table/app.py
index 9ef72df62e..95449ec9a3 100644
--- a/examples/table/table/app.py
+++ b/examples/table/table/app.py
@@ -94,7 +94,7 @@ def bottom_handler(self, widget, **kwargs):
         self.table1.scroll_to_bottom()
 
     def startup(self):
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # Label to show which row is currently selected.
         self.label_table1 = toga.Label("Ready.", style=Pack(flex=1, padding_right=5))
diff --git a/examples/table_source/table_source/app.py b/examples/table_source/table_source/app.py
index 9b9577f479..94362548ea 100644
--- a/examples/table_source/table_source/app.py
+++ b/examples/table_source/table_source/app.py
@@ -139,7 +139,7 @@ def clear_handler(self, widget, **kwargs):
         self.table1.data.clear()
 
     def startup(self):
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # Label to show which row is currently selected.
         self.label = toga.Label("Ready.")
diff --git a/examples/textinput/textinput/app.py b/examples/textinput/textinput/app.py
index f30439c4e9..0ecfe70055 100644
--- a/examples/textinput/textinput/app.py
+++ b/examples/textinput/textinput/app.py
@@ -47,7 +47,7 @@ def do_extract_values(self, widget, **kwargs):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
         PADDING = 5
 
         # Labels to show responses.
diff --git a/examples/tree/tree/app.py b/examples/tree/tree/app.py
index 77d6c1d3a9..edc50d8907 100644
--- a/examples/tree/tree/app.py
+++ b/examples/tree/tree/app.py
@@ -89,7 +89,7 @@ def remove_handler(self, widget, **kwargs):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         # Label to show responses.
         self.label = toga.Label("Ready.", style=Pack(padding=10))
diff --git a/examples/tree_source/tree_source/app.py b/examples/tree_source/tree_source/app.py
index 9a0c7f8769..d331495875 100644
--- a/examples/tree_source/tree_source/app.py
+++ b/examples/tree_source/tree_source/app.py
@@ -139,7 +139,7 @@ def activate_handler(self, widget, node):
 
     def startup(self):
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         self.fs_source = FileSystemSource(Path.cwd())
 
diff --git a/examples/tutorial2/tutorial/app.py b/examples/tutorial2/tutorial/app.py
index f78cd285bf..c17d89cf28 100644
--- a/examples/tutorial2/tutorial/app.py
+++ b/examples/tutorial2/tutorial/app.py
@@ -144,7 +144,9 @@ def action4(widget):
         # alter anything. Ordering is defined by the command definitions.
         self.commands.add(cmd1, cmd0, cmd6, cmd4, cmd5, cmd3)
 
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
+        # Command 2 has not been *explicitly* added to the app. Adding it to
+        # a toolbar implicitly adds it to the app.
         self.main_window.toolbar.add(cmd1, cmd3, cmd2, cmd4)
         self.main_window.content = split
 
diff --git a/examples/tutorial3/tutorial/app.py b/examples/tutorial3/tutorial/app.py
index 309cd07655..d6dfa21851 100644
--- a/examples/tutorial3/tutorial/app.py
+++ b/examples/tutorial3/tutorial/app.py
@@ -4,7 +4,7 @@
 
 class Graze(toga.App):
     def startup(self):
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
 
         self.webview = toga.WebView(
             on_webview_load=self.on_webview_loaded, style=Pack(flex=1)
diff --git a/examples/tutorial4/tutorial/app.py b/examples/tutorial4/tutorial/app.py
index 0b3d8c2c9e..5c1752b33a 100644
--- a/examples/tutorial4/tutorial/app.py
+++ b/examples/tutorial4/tutorial/app.py
@@ -9,8 +9,7 @@
 
 class StartApp(toga.App):
     def startup(self):
-        # Main window of the application with title and size
-        self.main_window = toga.MainWindow(title=self.name, size=(150, 250))
+        self.main_window = toga.MainWindow(size=(150, 250))
 
         # Create empty canvas
         self.canvas = toga.Canvas(
@@ -51,9 +50,13 @@ def draw_eyes(self):
         with self.canvas.Fill(color=WHITE) as eye_whites:
             eye_whites.arc(58, 92, 15)
             eye_whites.arc(88, 92, 15, math.pi, 3 * math.pi)
+
+        # Draw eyes separately to avoid miter join
         with self.canvas.Stroke(line_width=4.0) as eye_outline:
             eye_outline.arc(58, 92, 15)
+        with self.canvas.Stroke(line_width=4.0) as eye_outline:
             eye_outline.arc(88, 92, 15, math.pi, 3 * math.pi)
+
         with self.canvas.Fill() as eye_pupils:
             eye_pupils.arc(58, 97, 3)
             eye_pupils.arc(88, 97, 3)
diff --git a/examples/webview/webview/app.py b/examples/webview/webview/app.py
index c7dcfcbf06..a8b0924080 100644
--- a/examples/webview/webview/app.py
+++ b/examples/webview/webview/app.py
@@ -49,7 +49,7 @@ def on_set_agent(self, widget, **kwargs):
         self.webview.user_agent = "Mr Roboto"
 
     def startup(self):
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
         self.label = toga.Label("www is loading |", style=Pack(flex=1, padding=5))
 
         button_box = toga.Box(
diff --git a/examples/window/window/app.py b/examples/window/window/app.py
index 329e2c4d1d..caf84c2811 100644
--- a/examples/window/window/app.py
+++ b/examples/window/window/app.py
@@ -127,7 +127,7 @@ def startup(self):
         self.close_count = 0
 
         # Set up main window
-        self.main_window = toga.MainWindow(title=self.name)
+        self.main_window = toga.MainWindow()
         self.on_exit = self.exit_handler
 
         # Label to show responses.
diff --git a/gtk/setup.cfg b/gtk/setup.cfg
index 23018f1181..cc09df2006 100644
--- a/gtk/setup.cfg
+++ b/gtk/setup.cfg
@@ -12,7 +12,7 @@ author_email = russell@keith-magee.com
 maintainer = BeeWare Team
 maintainer_email = team@beeware.org
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Intended Audience :: Developers
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
diff --git a/gtk/src/toga_gtk/app.py b/gtk/src/toga_gtk/app.py
index 02e0cd2b4a..6fdf4adc02 100644
--- a/gtk/src/toga_gtk/app.py
+++ b/gtk/src/toga_gtk/app.py
@@ -1,9 +1,7 @@
 import asyncio
-import os
-import os.path
 import signal
 import sys
-from urllib.parse import unquote, urlparse
+from pathlib import Path
 
 import gbulb
 
@@ -16,20 +14,9 @@
 from .window import Window
 
 
-def gtk_menu_item_activate(cmd):
-    """Convert a GTK menu item activation into a command invocation."""
-
-    def _handler(action, data):
-        cmd.action(cmd)
-
-    return _handler
-
-
 class MainWindow(Window):
-    _IMPL_CLASS = Gtk.ApplicationWindow
-
     def create(self):
-        super().create()
+        self.native = Gtk.ApplicationWindow()
         self.native.set_role("MainWindow")
         icon_impl = toga_App.app.icon._impl
         self.native.set_icon(icon_impl.native_72)
@@ -42,7 +29,8 @@ def gtk_delete_event(self, *args):
         # closing the window) should be performed; so
         # "should_exit == True" must be converted to a return
         # value of False.
-        return not self.interface.app.exit()
+        self.interface.app.on_exit()
+        return True
 
 
 class App:
@@ -68,6 +56,7 @@ def create(self):
             application_id=self.interface.app_id,
             flags=Gio.ApplicationFlags.FLAGS_NONE,
         )
+        self.native_about_dialog = None
 
         # Connect the GTK signal that will cause app startup to occur
         self.native.connect("startup", self.gtk_startup)
@@ -79,15 +68,15 @@ def gtk_startup(self, data=None):
         # Set up the default commands for the interface.
         self.interface.commands.add(
             Command(
-                lambda _: self.interface.about(),
-                "About " + self.interface.name,
+                self._menu_about,
+                "About " + self.interface.formal_name,
                 group=toga.Group.HELP,
             ),
             Command(None, "Preferences", group=toga.Group.APP),
             # Quit should always be the last item, in a section on its own
             Command(
-                lambda _: self.interface.exit(),
-                "Quit " + self.interface.name,
+                self._menu_quit,
+                "Quit " + self.interface.formal_name,
                 shortcut=toga.Key.MOD_1 + "q",
                 group=toga.Group.APP,
                 section=sys.maxsize,
@@ -125,6 +114,12 @@ def _create_app_commands(self):
     def gtk_activate(self, data=None):
         pass
 
+    def _menu_about(self, app, **kwargs):
+        self.interface.about()
+
+    def _menu_quit(self, app, **kwargs):
+        self.interface.on_exit()
+
     def create_menus(self):
         # Only create the menu if the menu item index has been created.
         self._menu_items = {}
@@ -147,8 +142,7 @@ def create_menus(self):
 
                 cmd_id = "command-%s" % id(cmd)
                 action = Gio.SimpleAction.new(cmd_id, None)
-                if cmd.action:
-                    action.connect("activate", gtk_menu_item_activate(cmd))
+                action.connect("activate", cmd._impl.gtk_activate)
 
                 cmd._impl.native.append(action)
                 cmd._impl.set_enabled(cmd.enabled)
@@ -180,7 +174,7 @@ def _submenu(self, group, menubar):
 
                 text = group.text
                 if text == "*":
-                    text = self.interface.name
+                    text = self.interface.formal_name
 
                 parent_menu.append_submenu(text, submenu)
 
@@ -199,34 +193,36 @@ def set_main_window(self, window):
         pass
 
     def show_about_dialog(self):
-        about = Gtk.AboutDialog()
+        self.native_about_dialog = Gtk.AboutDialog()
+        self.native_about_dialog.set_modal(True)
 
         icon_impl = toga_App.app.icon._impl
-        about.set_logo(icon_impl.native_72)
+        self.native_about_dialog.set_logo(icon_impl.native_72)
 
-        if self.interface.name is not None:
-            about.set_program_name(self.interface.name)
+        self.native_about_dialog.set_program_name(self.interface.formal_name)
         if self.interface.version is not None:
-            about.set_version(self.interface.version)
+            self.native_about_dialog.set_version(self.interface.version)
         if self.interface.author is not None:
-            about.set_authors([self.interface.author])
+            self.native_about_dialog.set_authors([self.interface.author])
         if self.interface.description is not None:
-            about.set_comments(self.interface.description)
+            self.native_about_dialog.set_comments(self.interface.description)
         if self.interface.home_page is not None:
-            about.set_website(self.interface.home_page)
+            self.native_about_dialog.set_website(self.interface.home_page)
 
-        about.run()
-        about.destroy()
+        self.native_about_dialog.show()
+        self.native_about_dialog.connect("close", self._close_about)
+
+    def _close_about(self, dialog):
+        self.native_about_dialog.destroy()
+        self.native_about_dialog = None
 
     def beep(self):
-        Gdk.gdk_beep()
+        Gdk.beep()
 
-    def exit(self):
+    # We can't call this under test conditions, because it would kill the test harness
+    def exit(self):  # pragma: no cover
         self.native.quit()
 
-    def set_on_exit(self, value):
-        pass
-
     def get_current_window(self):
         return self.native.get_active_window()._impl
 
@@ -248,7 +244,7 @@ def hide_cursor(self):
         self.interface.factory.not_implemented("App.hide_cursor()")
 
 
-class DocumentApp(App):
+class DocumentApp(App):  # pragma: no cover
     def _create_app_commands(self):
         self.interface.commands.add(
             toga.Command(
@@ -265,38 +261,24 @@ def gtk_startup(self, data=None):
 
         try:
             # Look for a filename specified on the command line
-            file_name = os.path.abspath(sys.argv[1])
+            self.interface._open(Path(sys.argv[1]))
         except IndexError:
             # Nothing on the command line; open a file dialog instead.
-            # TODO: This causes a blank window to be shown.
-            # Is there a way to open a file dialog without having a window?
+            # Create a temporary window so we have context for the dialog
             m = toga.Window()
-            file_name = m.select_folder_dialog(self.interface.name, None, False)[0]
-
-        self.open_document(file_name)
+            m.open_file_dialog(
+                self.interface.formal_name,
+                file_types=self.interface.document_types.keys(),
+                on_result=lambda dialog, path: self.interface._open(path)
+                if path
+                else self.exit(),
+            )
 
     def open_file(self, widget, **kwargs):
-        # TODO: This causes a blank window to be shown.
-        # Is there a way to open a file dialog without having a window?
+        # Create a temporary window so we have context for the dialog
         m = toga.Window()
-        file_name = m.select_folder_dialog(self.interface.name, None, False)[0]
-
-        self.open_document(file_name)
-
-    def open_document(self, fileURL):
-        """Open a new document in this app.
-
-        Args:
-            fileURL (str): The URL/path to the file to add as a document.
-        """
-        # Convert the fileURL to a file path.
-        fileURL = fileURL.rstrip("/")
-        path = unquote(urlparse(fileURL).path)
-        extension = os.path.splitext(path)[1][1:]
-
-        # Create the document instance
-        DocType = self.interface.document_types[extension]
-        document = DocType(fileURL, self.interface)
-        self.interface._documents.append(document)
-
-        document.show()
+        m.open_file_dialog(
+            self.interface.formal_name,
+            file_types=self.interface.document_types.keys(),
+            on_result=lambda dialog, path: self.interface._open(path) if path else None,
+        )
diff --git a/gtk/src/toga_gtk/command.py b/gtk/src/toga_gtk/command.py
index c8cec0cca7..95d4e0e3e4 100644
--- a/gtk/src/toga_gtk/command.py
+++ b/gtk/src/toga_gtk/command.py
@@ -9,6 +9,12 @@ def __init__(self, interface):
         self.interface = interface
         self.native = []
 
+    def gtk_activate(self, action, data):
+        self.interface.action()
+
+    def gtk_clicked(self, action):
+        self.interface.action()
+
     def set_enabled(self, value):
         enabled = self.interface.enabled
         for widget in self.native:
diff --git a/gtk/src/toga_gtk/dialogs.py b/gtk/src/toga_gtk/dialogs.py
index 7b0395b5ee..0c3b598f3c 100644
--- a/gtk/src/toga_gtk/dialogs.py
+++ b/gtk/src/toga_gtk/dialogs.py
@@ -46,7 +46,7 @@ def gtk_response(self, dialog, response):
         else:
             result = None
 
-        self.on_result(self, result)
+        self.on_result(result)
         self.interface.future.set_result(result)
 
         self.native.destroy()
@@ -218,7 +218,7 @@ def gtk_response(self, dialog, response):
         else:
             result = None
 
-        self.on_result(self, result)
+        self.on_result(result)
         self.interface.future.set_result(result)
 
         self.native.destroy()
diff --git a/gtk/src/toga_gtk/documents.py b/gtk/src/toga_gtk/documents.py
index 6020f29a0b..9000fc5ce5 100644
--- a/gtk/src/toga_gtk/documents.py
+++ b/gtk/src/toga_gtk/documents.py
@@ -1,4 +1,7 @@
-class Document:
+class Document:  # pragma: no cover
+    # GTK has 1-1 correspondence between document and app instances.
+    SINGLE_DOCUMENT_APP = True
+
     def __init__(self, interface):
         self.interface = interface
         self.interface.read()
diff --git a/gtk/src/toga_gtk/images.py b/gtk/src/toga_gtk/images.py
index 32bc735869..cf8534d1d5 100644
--- a/gtk/src/toga_gtk/images.py
+++ b/gtk/src/toga_gtk/images.py
@@ -25,6 +25,14 @@ def get_width(self):
     def get_height(self):
         return self.native.get_height()
 
+    def get_data(self):
+        success, buffer = self.native.save_to_bufferv("png")
+        if success:
+            return buffer
+        else:  # pragma: nocover
+            # This shouldn't ever happen, and it's difficult to manufacture in test conditions
+            raise ValueError("Unable to get PNG data for image")
+
     def save(self, path):
         path = Path(path)
         try:
diff --git a/gtk/src/toga_gtk/keys.py b/gtk/src/toga_gtk/keys.py
index c9628379f8..7c92fab4c4 100644
--- a/gtk/src/toga_gtk/keys.py
+++ b/gtk/src/toga_gtk/keys.py
@@ -215,9 +215,7 @@
 }
 
 GTK_MODIFIER_CODES = {
-    Key.CAPSLOCK: "<CapsLock>",
     Key.SHIFT: "<Shift>",
-    # TODO: Confirm the mapping of Control, Meta and Hyper are correct.
     Key.MOD_1: "<Primary>",
     Key.MOD_2: "<Alt>",
     Key.MOD_3: "<Hyper>",
@@ -226,26 +224,20 @@
 
 def toga_key(event):
     """Convert a GDK Key Event into a Toga key."""
-    try:
-        key = GDK_KEYS[event.keyval]
+    key = GDK_KEYS[event.keyval]
 
-        modifiers = set()
+    modifiers = set()
 
-        # TODO: Confirm the mapping of Control, Meta and Hyper are correct.
-        if event.state & Gdk.ModifierType.LOCK_MASK:
-            modifiers.add(Key.CAPSLOCK)
-        if event.state & Gdk.ModifierType.SHIFT_MASK:
-            modifiers.add(Key.SHIFT)
-        if event.state & Gdk.ModifierType.CONTROL_MASK:
-            modifiers.add(Key.MOD_1)
-        if event.state & Gdk.ModifierType.META_MASK:
-            modifiers.add(Key.MOD_2)
-        if event.state & Gdk.ModifierType.HYPER_MASK:
-            modifiers.add(Key.MOD_3)
+    if event.state & Gdk.ModifierType.SHIFT_MASK:
+        modifiers.add(Key.SHIFT)
+    if event.state & Gdk.ModifierType.CONTROL_MASK:
+        modifiers.add(Key.MOD_1)
+    if event.state & Gdk.ModifierType.META_MASK:
+        modifiers.add(Key.MOD_2)
+    if event.state & Gdk.ModifierType.HYPER_MASK:
+        modifiers.add(Key.MOD_3)
 
-        return {"key": key, "modifiers": modifiers}
-    except KeyError:
-        return None
+    return {"key": key, "modifiers": modifiers}
 
 
 def gtk_accel(shortcut):
@@ -264,6 +256,11 @@ def gtk_accel(shortcut):
             accel = accel.replace(key.value, "")
             modifiers.append(code)
 
+    # If the accelerator text is upper case, add a shift modifier.
+    if accel.isalpha() and accel.isupper():
+        accel = accel.lower()
+        modifiers.append("<Shift>")
+
     # Find the canonical definition of the remaining key.
     for key, code in GTK_KEY_CODES.items():
         if key.value == accel:
diff --git a/gtk/src/toga_gtk/widgets/button.py b/gtk/src/toga_gtk/widgets/button.py
index e5563b804f..4a714e4775 100644
--- a/gtk/src/toga_gtk/widgets/button.py
+++ b/gtk/src/toga_gtk/widgets/button.py
@@ -35,4 +35,4 @@ def rehint(self):
         self.interface.intrinsic.height = height[1]
 
     def gtk_clicked(self, event):
-        self.interface.on_press(None)
+        self.interface.on_press()
diff --git a/gtk/src/toga_gtk/widgets/canvas.py b/gtk/src/toga_gtk/widgets/canvas.py
index 15504e0fcb..534c73e4f9 100644
--- a/gtk/src/toga_gtk/widgets/canvas.py
+++ b/gtk/src/toga_gtk/widgets/canvas.py
@@ -63,31 +63,31 @@ def gtk_draw_callback(self, widget, cairo_context):
     def gtk_on_size_allocate(self, widget, allocation):
         """Called on widget resize, and calls the handler set on the interface, if
         any."""
-        self.interface.on_resize(None, width=allocation.width, height=allocation.height)
+        self.interface.on_resize(width=allocation.width, height=allocation.height)
 
     def mouse_down(self, obj, event):
         if event.button == 1:
             if event.type == Gdk.EventType._2BUTTON_PRESS:
-                self.interface.on_activate(None, event.x, event.y)
+                self.interface.on_activate(event.x, event.y)
             else:
-                self.interface.on_press(None, event.x, event.y)
+                self.interface.on_press(event.x, event.y)
         elif event.button == 3:
-            self.interface.on_alt_press(None, event.x, event.y)
+            self.interface.on_alt_press(event.x, event.y)
         else:  # pragma: no cover
             # Don't handle other button presses
             pass
 
     def mouse_move(self, obj, event):
         if event.state == Gdk.ModifierType.BUTTON1_MASK:
-            self.interface.on_drag(None, event.x, event.y)
+            self.interface.on_drag(event.x, event.y)
         if event.state == Gdk.ModifierType.BUTTON3_MASK:
-            self.interface.on_alt_drag(None, event.x, event.y)
+            self.interface.on_alt_drag(event.x, event.y)
 
     def mouse_up(self, obj, event):
         if event.button == 1:
-            self.interface.on_release(None, event.x, event.y)
+            self.interface.on_release(event.x, event.y)
         elif event.button == 3:
-            self.interface.on_alt_release(None, event.x, event.y)
+            self.interface.on_alt_release(event.x, event.y)
         else:  # pragma: no cover
             # Don't handle other button presses
             pass
diff --git a/gtk/src/toga_gtk/widgets/detailedlist.py b/gtk/src/toga_gtk/widgets/detailedlist.py
index f627e4d5f3..7e47035cea 100644
--- a/gtk/src/toga_gtk/widgets/detailedlist.py
+++ b/gtk/src/toga_gtk/widgets/detailedlist.py
@@ -283,11 +283,11 @@ def gtk_on_value_changed(self, adj):
         self.hide_actions()
 
     def gtk_on_refresh_clicked(self, widget):
-        self.interface.on_refresh(self.interface)
+        self.interface.on_refresh()
 
     def gtk_on_row_selected(self, w: Gtk.ListBox, item_impl: Gtk.ListBoxRow):
         self.hide_actions()
-        self.interface.on_select(self.interface)
+        self.interface.on_select()
 
     def gtk_on_right_click(self, gesture, n_press, x, y):
         rect = Gdk.Rectangle()
@@ -307,11 +307,11 @@ def hide_actions(self):
             self._active_row = None
 
     def gtk_on_primary_clicked(self, widget):
-        self.interface.on_primary_action(None, row=self._active_row.row)
+        self.interface.on_primary_action(row=self._active_row.row)
         self.hide_actions()
 
     def gtk_on_secondary_clicked(self, widget):
-        self.interface.on_secondary_action(None, row=self._active_row.row)
+        self.interface.on_secondary_action(row=self._active_row.row)
         self.hide_actions()
 
     def update_refresh_button(self):
diff --git a/gtk/src/toga_gtk/widgets/multilinetextinput.py b/gtk/src/toga_gtk/widgets/multilinetextinput.py
index 66bdece4fd..35cb86922b 100644
--- a/gtk/src/toga_gtk/widgets/multilinetextinput.py
+++ b/gtk/src/toga_gtk/widgets/multilinetextinput.py
@@ -81,7 +81,7 @@ def set_value(self, value):
             self.native_textview.set_buffer(self.buffer)
         else:
             # See gtk_on_change for why this is needed
-            self.interface.on_change(None)
+            self.interface.on_change()
             if not self.has_focus:
                 self.native_textview.set_buffer(self.placeholder)
             else:
@@ -127,7 +127,7 @@ def gtk_on_changed(self, *args):
         # deliberately cleared, we add an explicit signal handler to set_value()
         # for the empty value case.
         if self.get_value():
-            self.interface.on_change(None)
+            self.interface.on_change()
 
     def gtk_on_focus_in(self, *args):
         # When focus is gained, make sure the content buffer is active.
diff --git a/gtk/src/toga_gtk/widgets/numberinput.py b/gtk/src/toga_gtk/widgets/numberinput.py
index d8100bf728..176825bf3a 100644
--- a/gtk/src/toga_gtk/widgets/numberinput.py
+++ b/gtk/src/toga_gtk/widgets/numberinput.py
@@ -20,7 +20,7 @@ def create(self):
         self.native.connect("changed", self.gtk_on_change)
 
     def gtk_on_change(self, widget):
-        self.interface.on_change(widget)
+        self.interface.on_change()
 
     def get_readonly(self):
         return not self.native.get_property("editable")
@@ -67,5 +67,7 @@ def rehint(self):
         width = self.native.get_preferred_width()
         height = self.native.get_preferred_height()
 
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH + width[1])
+        self.interface.intrinsic.width = at_least(
+            max(self.interface._MIN_WIDTH, width[1])
+        )
         self.interface.intrinsic.height = height[1]
diff --git a/gtk/src/toga_gtk/widgets/optioncontainer.py b/gtk/src/toga_gtk/widgets/optioncontainer.py
index ebf99ed718..6b3f3cba28 100644
--- a/gtk/src/toga_gtk/widgets/optioncontainer.py
+++ b/gtk/src/toga_gtk/widgets/optioncontainer.py
@@ -10,7 +10,7 @@ def create(self):
         self.sub_containers = []
 
     def gtk_on_switch_page(self, widget, page, page_num):
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def add_content(self, index, text, widget):
         sub_container = TogaContainer()
diff --git a/gtk/src/toga_gtk/widgets/scrollcontainer.py b/gtk/src/toga_gtk/widgets/scrollcontainer.py
index 2fbe8538c8..914ab7087b 100644
--- a/gtk/src/toga_gtk/widgets/scrollcontainer.py
+++ b/gtk/src/toga_gtk/widgets/scrollcontainer.py
@@ -23,7 +23,7 @@ def create(self):
         self.native.add(self.document_container)
 
     def gtk_on_changed(self, *args):
-        self.interface.on_scroll(None)
+        self.interface.on_scroll()
 
     def set_content(self, widget):
         self.document_container.content = widget
@@ -54,7 +54,7 @@ def set_horizontal(self, value):
         # Disabling scrolling implies a position reset; that's a scroll event.
         if not value:
             self.native.get_hadjustment().set_value(0)
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
 
     def get_vertical(self):
         return self.native.get_policy()[1] == Gtk.PolicyType.AUTOMATIC
@@ -69,7 +69,7 @@ def set_vertical(self, value):
         # Disabling scrolling implies a position reset; that's a scroll event.
         if not value:
             self.native.get_vadjustment().set_value(0)
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
 
     def get_max_vertical_position(self):
         return max(
@@ -98,4 +98,4 @@ def get_horizontal_position(self):
     def set_position(self, horizontal_position, vertical_position):
         self.native.get_hadjustment().set_value(horizontal_position)
         self.native.get_vadjustment().set_value(vertical_position)
-        self.interface.on_scroll(None)
+        self.interface.on_scroll()
diff --git a/gtk/src/toga_gtk/widgets/selection.py b/gtk/src/toga_gtk/widgets/selection.py
index cd2e3195ff..7ff6ab2330 100644
--- a/gtk/src/toga_gtk/widgets/selection.py
+++ b/gtk/src/toga_gtk/widgets/selection.py
@@ -20,7 +20,7 @@ def suspend_notifications(self):
 
     def gtk_on_changed(self, widget):
         if self._send_notifications:
-            self.interface.on_change(None)
+            self.interface.on_change()
 
     # FIXME: 2023-05-31 Everything I can find in documentation, and every test I
     # do with manual stylesheet in the GTK Inspector, says that `.toga button`
@@ -77,7 +77,7 @@ def remove(self, index, item):
     def clear(self):
         with self.suspend_notifications():
             self.native.remove_all()
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def select_item(self, index, item):
         self.native.set_active(index)
diff --git a/gtk/src/toga_gtk/widgets/slider.py b/gtk/src/toga_gtk/widgets/slider.py
index 36f3cec11d..301cbfa356 100644
--- a/gtk/src/toga_gtk/widgets/slider.py
+++ b/gtk/src/toga_gtk/widgets/slider.py
@@ -23,15 +23,15 @@ def create(self):
 
         self.native.connect(
             "value-changed",
-            lambda native: self.interface.on_change(None),
+            lambda native: self.interface.on_change(),
         )
         self.native.connect(
             "button-press-event",
-            lambda native, event: self.interface.on_press(None),
+            lambda native, event: self.interface.on_press(),
         )
         self.native.connect(
             "button-release-event",
-            lambda native, event: self.interface.on_release(None),
+            lambda native, event: self.interface.on_release(),
         )
 
         # Despite what the set_digits documentation says, set_round_digits has no effect
diff --git a/gtk/src/toga_gtk/widgets/switch.py b/gtk/src/toga_gtk/widgets/switch.py
index 349dc131ff..8c86d2bc1f 100644
--- a/gtk/src/toga_gtk/widgets/switch.py
+++ b/gtk/src/toga_gtk/widgets/switch.py
@@ -24,7 +24,7 @@ def create(self):
         self.native.pack_start(self.native_switch, False, False, 0)
 
     def gtk_notify_active(self, widget, state):
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_enabled(self):
         return self.native_switch.get_sensitive()
diff --git a/gtk/src/toga_gtk/widgets/table.py b/gtk/src/toga_gtk/widgets/table.py
index 6c76e88882..feeb8b8f2b 100644
--- a/gtk/src/toga_gtk/widgets/table.py
+++ b/gtk/src/toga_gtk/widgets/table.py
@@ -90,10 +90,10 @@ def _create_columns(self):
 
     def gtk_on_row_activated(self, widget, path, column):
         row = self.store[path][0].value
-        self.interface.on_activate(None, row=row)
+        self.interface.on_activate(row=row)
 
     def gtk_on_select(self, selection):
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def change_source(self, source):
         # Temporarily disconnecting the TreeStore improves performance for large
diff --git a/gtk/src/toga_gtk/widgets/textinput.py b/gtk/src/toga_gtk/widgets/textinput.py
index 3e3d68c57b..ecce9555d5 100644
--- a/gtk/src/toga_gtk/widgets/textinput.py
+++ b/gtk/src/toga_gtk/widgets/textinput.py
@@ -16,19 +16,19 @@ def create(self):
         self.native.connect("key-press-event", self.gtk_key_press_event)
 
     def gtk_on_change(self, entry):
-        self.interface.on_change(self.interface)
+        self.interface.on_change()
         self.interface._validate()
 
     def gtk_focus_in_event(self, entry, user_data):
-        self.interface.on_gain_focus(self.interface)
+        self.interface.on_gain_focus()
 
     def gtk_focus_out_event(self, entry, user_data):
-        self.interface.on_lose_focus(self.interface)
+        self.interface.on_lose_focus()
 
     def gtk_key_press_event(self, entry, user_data):
         key_pressed = toga_key(user_data)
         if key_pressed and key_pressed["key"] in {Key.ENTER, Key.NUMPAD_ENTER}:
-            self.interface.on_confirm(None)
+            self.interface.on_confirm()
 
     def get_readonly(self):
         return not self.native.get_property("editable")
@@ -59,10 +59,12 @@ def rehint(self):
         #     self._impl.get_preferred_width(), self._impl.get_preferred_height(),
         #     getattr(self, '_fixed_height', False), getattr(self, '_fixed_width', False)
         # )
-        # width = self.native.get_preferred_width()
+        width = self.native.get_preferred_width()
         height = self.native.get_preferred_height()
 
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
+        self.interface.intrinsic.width = at_least(
+            max(self.interface._MIN_WIDTH, width[1])
+        )
         self.interface.intrinsic.height = height[1]
 
     def set_error(self, error_message):
diff --git a/gtk/src/toga_gtk/widgets/tree.py b/gtk/src/toga_gtk/widgets/tree.py
index 3c6e945cce..9a4a645dcd 100644
--- a/gtk/src/toga_gtk/widgets/tree.py
+++ b/gtk/src/toga_gtk/widgets/tree.py
@@ -55,11 +55,11 @@ def _create_columns(self):
             self.native_tree.append_column(column)
 
     def gtk_on_select(self, selection):
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def gtk_on_row_activated(self, widget, path, column):
         node = self.store[path][0].value
-        self.interface.on_activate(None, node=node)
+        self.interface.on_activate(node=node)
 
     def change_source(self, source):
         # Temporarily disconnecting the TreeStore improves performance for large
diff --git a/gtk/src/toga_gtk/widgets/webview.py b/gtk/src/toga_gtk/widgets/webview.py
index 4cb86660e2..3d17b33f71 100644
--- a/gtk/src/toga_gtk/widgets/webview.py
+++ b/gtk/src/toga_gtk/widgets/webview.py
@@ -34,7 +34,7 @@ def create(self):
 
     def gtk_on_load_changed(self, widget, load_event, *args):
         if load_event == WebKit2.LoadEvent.FINISHED:
-            self.interface.on_webview_load(None)
+            self.interface.on_webview_load()
 
             if self.load_future:
                 self.load_future.set_result(None)
diff --git a/gtk/src/toga_gtk/window.py b/gtk/src/toga_gtk/window.py
index 208ee63ffe..0bcea2d8a0 100644
--- a/gtk/src/toga_gtk/window.py
+++ b/gtk/src/toga_gtk/window.py
@@ -1,13 +1,10 @@
 from toga.command import GROUP_BREAK, SECTION_BREAK
-from toga.handlers import wrapped_handler
 
 from .container import TogaContainer
-from .libs import Gtk
+from .libs import Gdk, Gtk
 
 
 class Window:
-    _IMPL_CLASS = Gtk.Window
-
     def __init__(self, interface, title, position, size):
         self.interface = interface
         self.interface._impl = self
@@ -16,7 +13,7 @@ def __init__(self, interface, title, position, size):
 
         self.layout = None
 
-        self.native = self._IMPL_CLASS()
+        self.create()
         self.native._impl = self
 
         self.native.connect("delete-event", self.gtk_delete_event)
@@ -33,20 +30,27 @@ def __init__(self, interface, title, position, size):
         # Window Decorator when resizable == False
         self.native.set_resizable(self.interface.resizable)
 
-        self.toolbar_native = None
-        self.toolbar_items = None
-
         # The GTK window's content is the layout; any user content is placed
         # into the container, which is the bottom widget in the layout. The
         # toolbar (if required) will be added at the top of the layout.
-        #
+        self.layout = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
+
+        self.native_toolbar = Gtk.Toolbar()
+        self.native_toolbar.set_style(Gtk.ToolbarStyle.BOTH)
+        self.native_toolbar.set_visible(False)
+        self.toolbar_items = {}
+        self.layout.pack_start(self.native_toolbar, expand=False, fill=False, padding=0)
+
         # Because expand and fill are True, the container will fill the available
         # space, and will get a size_allocate callback if the window is resized.
-        self.layout = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
         self.container = TogaContainer()
         self.layout.pack_end(self.container, expand=True, fill=True, padding=0)
+
         self.native.add(self.layout)
 
+    def create(self):
+        self.native = Gtk.Window()
+
     def get_title(self):
         return self.native.get_title()
 
@@ -57,18 +61,20 @@ def set_app(self, app):
         app.native.add_window(self.native)
 
     def create_toolbar(self):
-        if self.toolbar_items is None:
-            self.toolbar_native = Gtk.Toolbar()
-            self.toolbar_items = {}
-            self.layout.pack_start(
-                self.toolbar_native, expand=False, fill=False, padding=0
-            )
-        else:
-            for cmd, item_impl in self.toolbar_items.items():
-                self.toolbar_native.remove(item_impl)
+        # Remove any pre-existing toolbar content
+        if self.toolbar_items:
+            self.native_toolbar.set_visible(False)
+
+        for cmd, item_impl in self.toolbar_items.items():
+            self.native_toolbar.remove(item_impl)
+            try:
                 cmd._impl.native.remove(item_impl)
+            except AttributeError:
+                # Breaks don't have _impls, so there's no native to clean up
+                pass
 
-        self.toolbar_native.set_style(Gtk.ToolbarStyle.BOTH)
+        # Create the new toolbar items
+        self.toolbar_items = {}
         for cmd in self.interface.toolbar:
             if cmd == GROUP_BREAK:
                 item_impl = Gtk.SeparatorToolItem()
@@ -79,13 +85,20 @@ def create_toolbar(self):
             else:
                 item_impl = Gtk.ToolButton()
                 if cmd.icon:
-                    item_impl.set_icon_widget(cmd.icon._impl.native_32)
+                    item_impl.set_icon_widget(
+                        Gtk.Image.new_from_pixbuf(cmd.icon._impl.native_32)
+                    )
                 item_impl.set_label(cmd.text)
-                item_impl.set_tooltip_text(cmd.tooltip)
-                item_impl.connect("clicked", wrapped_handler(cmd, cmd.action))
+                if cmd.tooltip:
+                    item_impl.set_tooltip_text(cmd.tooltip)
+                item_impl.connect("clicked", cmd._impl.gtk_clicked)
                 cmd._impl.native.append(item_impl)
             self.toolbar_items[cmd] = item_impl
-            self.toolbar_native.insert(item_impl, -1)
+            self.native_toolbar.insert(item_impl, -1)
+
+        if self.toolbar_items:
+            self.native_toolbar.set_visible(True)
+            self.native_toolbar.show_all()
 
     def set_content(self, widget):
         # Set the new widget to be the container's content
@@ -104,7 +117,7 @@ def gtk_delete_event(self, widget, data):
         if self._is_closing:
             should_close = True
         else:
-            should_close = self.interface.on_close(self.interface.app)
+            should_close = self.interface.on_close()
 
         # Return value of the GTK on_close handler indicates
         # whether the event has been fully handled. Returning
@@ -136,3 +149,32 @@ def set_full_screen(self, is_full_screen):
             self.native.fullscreen()
         else:
             self.native.unfullscreen()
+
+    def get_image_data(self):
+        display = self.native.get_display()
+        display.flush()
+
+        # For some reason, converting the *window* to a pixbuf fails. But if you extract
+        # a *part* of the overall screen, that works. So - work out the origin of the
+        # window, then the allocation for the container relative to that window, and
+        # capture that rectangle.
+        window = self.native.get_window()
+        origin = window.get_origin()
+        allocation = self.container.get_allocation()
+
+        screen = display.get_default_screen()
+        root_window = screen.get_root_window()
+        screenshot = Gdk.pixbuf_get_from_window(
+            root_window,
+            origin.x + allocation.x,
+            origin.y + allocation.y,
+            allocation.width,
+            allocation.height,
+        )
+
+        success, buffer = screenshot.save_to_bufferv("png")
+        if success:
+            return buffer
+        else:  # pragma: nocover
+            # This shouldn't ever happen, and it's difficult to manufacture in test conditions
+            raise ValueError(f"Unable to generate screenshot of {self}")
diff --git a/gtk/tests/__init__.py b/gtk/tests/__init__.py
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/gtk/tests/test_implementation.py b/gtk/tests/test_implementation.py
deleted file mode 100644
index 18f301b09f..0000000000
--- a/gtk/tests/test_implementation.py
+++ /dev/null
@@ -1,11 +0,0 @@
-import os
-
-from toga_dummy import test_implementation
-
-globals().update(
-    test_implementation.create_impl_tests(
-        os.path.abspath(
-            os.path.join(os.path.dirname(os.path.dirname(__file__)), "src", "toga_gtk")
-        )
-    )
-)
diff --git a/gtk/tests/widgets/__init__.py b/gtk/tests/widgets/__init__.py
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/gtk/tests_backend/app.py b/gtk/tests_backend/app.py
index 72d677d0c7..bc69ba1089 100644
--- a/gtk/tests_backend/app.py
+++ b/gtk/tests_backend/app.py
@@ -1,11 +1,17 @@
 from pathlib import Path
 
-from toga_gtk.libs import Gtk
+import pytest
+
+from toga_gtk.keys import gtk_accel, toga_key
+from toga_gtk.libs import Gdk, Gtk
 
 from .probe import BaseProbe
 
 
 class AppProbe(BaseProbe):
+    supports_key = True
+    supports_key_mod3 = True
+
     def __init__(self, app):
         super().__init__()
         self.app = app
@@ -26,3 +32,125 @@ def cache_path(self):
     @property
     def logs_path(self):
         return Path.home() / ".local" / "state" / "testbed" / "log"
+
+    @property
+    def is_cursor_visible(self):
+        pytest.skip("Cursor visibility not implemented on GTK")
+
+    def is_full_screen(self, window):
+        return bool(
+            window._impl.native.get_window().get_state() & Gdk.WindowState.FULLSCREEN
+        )
+
+    def content_size(self, window):
+        content_allocation = window._impl.container.get_allocation()
+        return (content_allocation.width, content_allocation.height)
+
+    def _menu_item(self, path):
+        main_menu = self.app._impl.native.get_menubar()
+        menu = main_menu
+        orig_path = path.copy()
+        try:
+            while True:
+                label, path = path[0], path[1:]
+                items = {}
+                for index in range(menu.get_n_items()):
+                    section = menu.get_item_link(index, "section")
+                    if section:
+                        for section_index in range(section.get_n_items()):
+                            items[
+                                section.get_item_attribute_value(
+                                    section_index, "label"
+                                ).get_string()
+                            ] = (section, section_index)
+                    else:
+                        items[
+                            menu.get_item_attribute_value(index, "label").get_string()
+                        ] = (menu, index)
+
+                if label == "*":
+                    item = items[self.app.formal_name]
+                else:
+                    item = items[label]
+
+                menu = item[0].get_item_link(item[1], "submenu")
+        except IndexError:
+            pass
+        except AttributeError:
+            raise AssertionError(f"Menu {' > '.join(orig_path)} not found")
+
+        action_name = item[0].get_item_attribute_value(item[1], "action").get_string()
+        cmd_id = action_name.split(".")[1]
+        action = self.app._impl.native.lookup_action(cmd_id)
+        return action
+
+    def _activate_menu_item(self, path):
+        item = self._menu_item(path)
+        item.emit("activate", None)
+
+    def activate_menu_exit(self):
+        self._activate_menu_item(["*", "Quit Toga Testbed"])
+
+    def activate_menu_about(self):
+        self._activate_menu_item(["Help", "About Toga Testbed"])
+
+    async def close_about_dialog(self):
+        self.app._impl._close_about(self.app._impl.native_about_dialog)
+
+    def activate_menu_visit_homepage(self):
+        # Homepage is a link on the GTK about page.
+        pytest.xfail("GTK doesn't have a visit homepage menu item")
+
+    def assert_system_menus(self):
+        self.assert_menu_item(["*", "Preferences"], enabled=False)
+        self.assert_menu_item(["*", "Quit Toga Testbed"], enabled=True)
+
+        self.assert_menu_item(["Help", "About Toga Testbed"], enabled=True)
+
+    def activate_menu_close_window(self):
+        pytest.xfail("GTK doesn't have a window management menu items")
+
+    def activate_menu_close_all_windows(self):
+        pytest.xfail("GTK doesn't have a window management menu items")
+
+    def activate_menu_minimize(self):
+        pytest.xfail("GTK doesn't have a window management menu items")
+
+    def assert_menu_item(self, path, enabled):
+        item = self._menu_item(path)
+        assert item.get_enabled() == enabled
+
+    def keystroke(self, combination):
+        accel = gtk_accel(combination)
+        state = 0
+
+        if "<Primary>" in accel:
+            state |= Gdk.ModifierType.CONTROL_MASK
+            accel = accel.replace("<Primary>", "")
+        if "<Alt>" in accel:
+            state |= Gdk.ModifierType.META_MASK
+            accel = accel.replace("<Alt>", "")
+        if "<Hyper>" in accel:
+            state |= Gdk.ModifierType.HYPER_MASK
+            accel = accel.replace("<Hyper>", "")
+        if "<Shift>" in accel:
+            state |= Gdk.ModifierType.SHIFT_MASK
+            accel = accel.replace("<Shift>", "")
+
+        keyval = getattr(
+            Gdk,
+            f"KEY_{accel}",
+            {
+                "!": Gdk.KEY_exclam,
+                "<home>": Gdk.KEY_Home,
+                "F5": Gdk.KEY_F5,
+            }.get(accel, None),
+        )
+
+        event = Gdk.Event.new(Gdk.EventType.KEY_PRESS)
+        event.keyval = keyval
+        event.length = 1
+        event.is_modifier = state != 0
+        event.state = state
+
+        return toga_key(event)
diff --git a/gtk/tests_backend/probe.py b/gtk/tests_backend/probe.py
index 597c0a5470..abb09434fd 100644
--- a/gtk/tests_backend/probe.py
+++ b/gtk/tests_backend/probe.py
@@ -20,3 +20,6 @@ async def redraw(self, message=None, delay=None):
 
         if delay:
             await asyncio.sleep(delay)
+
+    def assert_image_size(self, image_size, size):
+        assert image_size == size
diff --git a/gtk/tests_backend/widgets/canvas.py b/gtk/tests_backend/widgets/canvas.py
index 391cdf04ec..81deb6caa9 100644
--- a/gtk/tests_backend/widgets/canvas.py
+++ b/gtk/tests_backend/widgets/canvas.py
@@ -19,10 +19,6 @@ def reference_variant(self, reference):
     def get_image(self):
         return Image.open(BytesIO(self.impl.get_image_data()))
 
-    def assert_image_size(self, image, width, height):
-        assert image.width == width
-        assert image.height == height
-
     async def mouse_press(self, x, y):
         event = Gdk.Event.new(Gdk.EventType.BUTTON_PRESS)
         event.button = 1
diff --git a/gtk/tests_backend/window.py b/gtk/tests_backend/window.py
index 8075343e2f..a90b60f8ef 100644
--- a/gtk/tests_backend/window.py
+++ b/gtk/tests_backend/window.py
@@ -25,7 +25,7 @@ def __init__(self, app, window):
         assert isinstance(self.native, Gtk.Window)
 
     async def wait_for_window(self, message, minimize=False, full_screen=False):
-        await self.redraw(message, delay=0.5 if full_screen or minimize else 0.1)
+        await self.redraw(message, delay=0.5 if (full_screen or minimize) else 0.1)
 
     def close(self):
         if self.is_closable:
@@ -229,3 +229,25 @@ async def close_select_folder_dialog(self, dialog, result, multiple_select):
                 f"({'OPEN' if result else 'CANCEL'}) dismissed"
             ),
         )
+
+    def has_toolbar(self):
+        return self.impl.native_toolbar.get_n_items() > 0
+
+    def assert_is_toolbar_separator(self, index, section=False):
+        item = self.impl.native_toolbar.get_nth_item(index)
+        assert isinstance(item, Gtk.SeparatorToolItem)
+        assert item.get_draw() == (not section)
+
+    def assert_toolbar_item(self, index, label, tooltip, has_icon, enabled):
+        item = self.impl.native_toolbar.get_nth_item(index)
+        assert item.get_label() == label
+        # FIXME: get_tooltip_text() doesn't work. The tooltip can be set, but the
+        # API to return the value just doesn't work. If it is ever fixed, this
+        # is the test for it:
+        # assert (None if item.get_tooltip_text() is None else item.get_tooltip_text()) == tooltip
+        assert (item.get_icon_widget() is not None) == has_icon
+        assert item.get_sensitive() == enabled
+
+    def press_toolbar_button(self, index):
+        item = self.impl.native_toolbar.get_nth_item(index)
+        item.emit("clicked")
diff --git a/iOS/setup.cfg b/iOS/setup.cfg
index 9ec85252d7..18d9fe6002 100644
--- a/iOS/setup.cfg
+++ b/iOS/setup.cfg
@@ -12,7 +12,7 @@ author_email = russell@keith-magee.com
 maintainer = BeeWare Team
 maintainer_email = team@beeware.org
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Intended Audience :: Developers
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
diff --git a/iOS/setup.py b/iOS/setup.py
index f9c2736edd..30217c2e40 100644
--- a/iOS/setup.py
+++ b/iOS/setup.py
@@ -7,7 +7,7 @@
     version=version,
     install_requires=[
         "fonttools >= 4.42.1, < 5.0.0",
-        "rubicon-objc >= 0.4.5rc1, < 0.5.0",
+        "rubicon-objc >= 0.4.7, < 0.5.0",
         f"toga-core == {version}",
     ],
 )
diff --git a/iOS/src/toga_iOS/app.py b/iOS/src/toga_iOS/app.py
index 48c4f7f653..343790c2a1 100644
--- a/iOS/src/toga_iOS/app.py
+++ b/iOS/src/toga_iOS/app.py
@@ -3,7 +3,7 @@
 from rubicon.objc import objc_method
 from rubicon.objc.eventloop import EventLoopPolicy, iOSLifecycle
 
-from toga_iOS.libs import UIResponder
+from toga_iOS.libs import UIResponder, av_foundation
 from toga_iOS.window import Window
 
 
@@ -67,10 +67,14 @@ def create(self):
         """Calls the startup method on the interface."""
         self.interface._startup()
 
-    def open_document(self, fileURL):
+    def open_document(self, fileURL):  # pragma: no cover
         """Add a new document to this app."""
         pass
 
+    def create_menus(self):
+        # No menus on an iOS app (for now)
+        pass
+
     def main_loop(self):
         # Main loop is non-blocking on iOS. The app loop is integrated with the
         # main iOS event loop, so this call will return; however, it will leave
@@ -81,17 +85,38 @@ def main_loop(self):
     def set_main_window(self, window):
         pass
 
+    def get_current_window(self):
+        # iOS only has a main window.
+        return self.interface.main_window._impl
+
+    def set_current_window(self, window):
+        # iOS only has a main window, so this is a no-op
+        pass
+
     def show_about_dialog(self):
         self.interface.factory.not_implemented("App.show_about_dialog()")
 
     def beep(self):
-        self.interface.factory.not_implemented("App.beep()")
+        # 1013 is a magic constant that is the "SMS RECEIVED 5" sound,
+        # sounding like a single strike of a bell.
+        av_foundation.AudioServicesPlayAlertSound(1013)
+
+    def exit(self):  # pragma: no cover
+        # Mobile apps can't be exited, but the entry point needs to exist
+        pass
+
+    def enter_full_screen(self, windows):
+        # No-op; mobile doesn't support full screen
+        pass
 
-    def exit(self):
+    def exit_full_screen(self, windows):
+        # No-op; mobile doesn't support full screen
         pass
 
     def hide_cursor(self):
+        # No-op; mobile doesn't support cursors
         pass
 
     def show_cursor(self):
+        # No-op; mobile doesn't support cursors
         pass
diff --git a/iOS/src/toga_iOS/dialogs.py b/iOS/src/toga_iOS/dialogs.py
index 300a52e76a..9216de940c 100644
--- a/iOS/src/toga_iOS/dialogs.py
+++ b/iOS/src/toga_iOS/dialogs.py
@@ -1,7 +1,6 @@
 from abc import ABC, abstractmethod
 
-from rubicon.objc import Block
-from rubicon.objc.runtime import objc_id
+from rubicon.objc import Block, objc_id
 
 from toga_iOS.libs import (
     UIAlertAction,
@@ -39,7 +38,7 @@ def populate_dialog(self, native):
         ...
 
     def response(self, value):
-        self.on_result(self, value)
+        self.on_result(value)
         self.interface.future.set_result(value)
 
     def null_response(self, action: objc_id) -> None:
diff --git a/iOS/src/toga_iOS/images.py b/iOS/src/toga_iOS/images.py
index c3da2eba8a..2d0c0cbf3e 100644
--- a/iOS/src/toga_iOS/images.py
+++ b/iOS/src/toga_iOS/images.py
@@ -1,3 +1,4 @@
+from ctypes import POINTER, c_char, cast
 from pathlib import Path
 
 from toga_iOS.libs import (
@@ -7,6 +8,15 @@
 )
 
 
+def nsdata_to_bytes(data: NSData) -> bytes:
+    """Convert an NSData into a raw bytes representation"""
+    # data is an NSData object that has .bytes as a c_void_p, and a .length. Cast to
+    # POINTER(c_char) to get an addressable array of bytes, and slice that array to
+    # the known length. We don't use c_char_p because it has handling of NUL
+    # termination, and POINTER(c_char) allows array subscripting.
+    return cast(data.bytes, POINTER(c_char))[: data.length]
+
+
 class Image:
     def __init__(self, interface, path=None, data=None):
         self.interface = interface
@@ -33,6 +43,9 @@ def get_width(self):
     def get_height(self):
         return self.native.size.height
 
+    def get_data(self):
+        return nsdata_to_bytes(NSData(uikit.UIImagePNGRepresentation(self.native)))
+
     def save(self, path):
         path = Path(path)
         try:
diff --git a/iOS/src/toga_iOS/libs/__init__.py b/iOS/src/toga_iOS/libs/__init__.py
index 105a6400a7..50dd37acf7 100644
--- a/iOS/src/toga_iOS/libs/__init__.py
+++ b/iOS/src/toga_iOS/libs/__init__.py
@@ -1,3 +1,4 @@
+from .av_foundation import *  # NOQA
 from .core_graphics import *  # NOQA
 from .foundation import *  # NOQA
 from .uikit import *  # NOQA
diff --git a/iOS/src/toga_iOS/libs/av_foundation.py b/iOS/src/toga_iOS/libs/av_foundation.py
new file mode 100644
index 0000000000..5367d885e5
--- /dev/null
+++ b/iOS/src/toga_iOS/libs/av_foundation.py
@@ -0,0 +1,13 @@
+##########################################################################
+# System/Library/Frameworks/AVFoundation.framework
+##########################################################################
+from ctypes import c_uint32, cdll, util
+
+######################################################################
+av_foundation = cdll.LoadLibrary(util.find_library("AVFoundation"))
+######################################################################
+
+SystemSoundID = c_uint32
+
+av_foundation.AudioServicesPlayAlertSound.restype = None
+av_foundation.AudioServicesPlayAlertSound.argtypes = [SystemSoundID]
diff --git a/iOS/src/toga_iOS/libs/core_graphics.py b/iOS/src/toga_iOS/libs/core_graphics.py
index 929f8f0d52..356fcd2419 100644
--- a/iOS/src/toga_iOS/libs/core_graphics.py
+++ b/iOS/src/toga_iOS/libs/core_graphics.py
@@ -198,3 +198,13 @@ class CGAffineTransform(Structure):
 
 def CGRectMake(x, y, w, h):
     return CGRect(CGPoint(x, y), CGSize(w, h))
+
+
+######################################################################
+# CGImage.h
+
+CGImageRef = c_void_p
+register_preferred_encoding(b"^{CGImage=}", CGImageRef)
+
+core_graphics.CGImageCreateWithImageInRect.argtypes = [CGImageRef, CGRect]
+core_graphics.CGImageCreateWithImageInRect.restype = CGImageRef
diff --git a/iOS/src/toga_iOS/widgets/button.py b/iOS/src/toga_iOS/widgets/button.py
index a3724beeb2..007b2e7792 100644
--- a/iOS/src/toga_iOS/widgets/button.py
+++ b/iOS/src/toga_iOS/widgets/button.py
@@ -19,7 +19,7 @@ class TogaButton(UIButton):
 
     @objc_method
     def onPress_(self, obj) -> None:
-        self.interface.on_press(None)
+        self.interface.on_press()
 
 
 class Button(Widget):
diff --git a/iOS/src/toga_iOS/widgets/canvas.py b/iOS/src/toga_iOS/widgets/canvas.py
index 4ceacc8838..9fc213f304 100644
--- a/iOS/src/toga_iOS/widgets/canvas.py
+++ b/iOS/src/toga_iOS/widgets/canvas.py
@@ -1,4 +1,3 @@
-from ctypes import POINTER, c_char, cast
 from math import ceil
 
 from rubicon.objc import (
@@ -10,15 +9,16 @@
     NSPoint,
     NSRect,
     NSSize,
+    objc_id,
     objc_method,
     objc_property,
 )
-from rubicon.objc.runtime import objc_id
 from travertino.size import at_least
 
 from toga.colors import BLACK, TRANSPARENT, color
 from toga.constants import Baseline, FillRule
 from toga_iOS.colors import native_color
+from toga_iOS.images import nsdata_to_bytes
 from toga_iOS.libs import (
     CGPathDrawingMode,
     CGRectMake,
@@ -51,17 +51,17 @@ def drawRect_(self, rect: CGRect) -> None:
     @objc_method
     def touchesBegan_withEvent_(self, touches, event) -> None:
         position = touches.allObjects()[0].locationInView(self)
-        self.interface.on_press(None, position.x, position.y)
+        self.interface.on_press(position.x, position.y)
 
     @objc_method
     def touchesMoved_withEvent_(self, touches, event) -> None:
         position = touches.allObjects()[0].locationInView(self)
-        self.interface.on_drag(None, position.x, position.y)
+        self.interface.on_drag(position.x, position.y)
 
     @objc_method
     def touchesEnded_withEvent_(self, touches, event) -> None:
         position = touches.allObjects()[0].locationInView(self)
-        self.interface.on_release(None, position.x, position.y)
+        self.interface.on_release(position.x, position.y)
 
 
 class Canvas(Widget):
@@ -75,7 +75,7 @@ def create(self):
 
     def set_bounds(self, x, y, width, height):
         super().set_bounds(x, y, width, height)
-        self.interface.on_resize(None, width=width, height=height)
+        self.interface.on_resize(width=width, height=height)
 
     def redraw(self):
         self.native.setNeedsDisplay()
@@ -311,13 +311,9 @@ def render(context):
                 self.native.bounds, afterScreenUpdates=True
             )
 
-        data = renderer.PNGDataWithActions(Block(render, None, objc_id))
-
-        # data is an NSData object that has .bytes as a c_void_p, and a .length. Cast to
-        # POINTER(c_char) to get an addressable array of bytes, and slice that array to
-        # the known length. We don't use c_char_p because it has handling of NUL
-        # termination, and POINTER(c_char) allows array subscripting.
-        return cast(data.bytes, POINTER(c_char))[: data.length]
+        return nsdata_to_bytes(
+            renderer.PNGDataWithActions(Block(render, None, objc_id))
+        )
 
     # Rehint
     def rehint(self):
diff --git a/iOS/src/toga_iOS/widgets/detailedlist.py b/iOS/src/toga_iOS/widgets/detailedlist.py
index 26a55e71a3..6212de3504 100644
--- a/iOS/src/toga_iOS/widgets/detailedlist.py
+++ b/iOS/src/toga_iOS/widgets/detailedlist.py
@@ -76,7 +76,7 @@ def tableView_cellForRowAtIndexPath_(self, tableView, indexPath):
 
     @objc_method
     def tableView_didSelectRowAtIndexPath_(self, tableView, indexPath):
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     # UITableViewDelegate methods
     @objc_method
@@ -119,7 +119,7 @@ def tableView_leadingSwipeActionsConfigurationForRowAtIndexPath_(
 
     @objc_method
     def refresh(self):
-        self.interface.on_refresh(None)
+        self.interface.on_refresh()
 
 
 class DetailedList(Widget):
@@ -164,7 +164,7 @@ def handle_primary_action(
             actionPerformed: ObjCInstance,
         ) -> None:
             item = self.interface.data[row]
-            self.interface.on_primary_action(self, row=item)
+            self.interface.on_primary_action(row=item)
             ObjCBlock(actionPerformed, None, bool)(True)
 
         return handle_primary_action
@@ -179,7 +179,7 @@ def handle_secondary_action(
             actionPerformed: ObjCInstance,
         ) -> None:
             item = self.interface.data[row]
-            self.interface.on_secondary_action(self, row=item)
+            self.interface.on_secondary_action(row=item)
             ObjCBlock(actionPerformed, None, bool)(True)
 
         return handle_secondary_action
diff --git a/iOS/src/toga_iOS/widgets/multilinetextinput.py b/iOS/src/toga_iOS/widgets/multilinetextinput.py
index 16da6d64f2..600dbfb60d 100644
--- a/iOS/src/toga_iOS/widgets/multilinetextinput.py
+++ b/iOS/src/toga_iOS/widgets/multilinetextinput.py
@@ -51,7 +51,7 @@ def textViewDidEndEditing_(self, text_view):
 
     @objc_method
     def textViewDidChange_(self, text_view):
-        self.interface.on_change(None)
+        self.interface.on_change()
 
 
 class MultilineTextInput(Widget):
@@ -134,7 +134,7 @@ def get_value(self):
     def set_value(self, value):
         self.native.text = value
         self.placeholder_label.setHidden(self.has_focus or len(self.native.text) > 0)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def set_color(self, value):
         color = native_color(value)
diff --git a/iOS/src/toga_iOS/widgets/numberinput.py b/iOS/src/toga_iOS/widgets/numberinput.py
index 9e50d3047d..cbb7ca0b45 100644
--- a/iOS/src/toga_iOS/widgets/numberinput.py
+++ b/iOS/src/toga_iOS/widgets/numberinput.py
@@ -22,7 +22,7 @@ class TogaNumericTextField(UITextField):
 
     @objc_method
     def textFieldDidChange_(self, notification) -> None:
-        self.interface.on_change(self.interface)
+        self.interface.on_change()
 
     @objc_method
     def textField_shouldChangeCharactersInRange_replacementString_(
@@ -106,7 +106,7 @@ def set_value(self, value):
             self.native.text = ""
         else:
             self.native.text = str(value)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def set_alignment(self, value):
         self.native.textAlignment = NSTextAlignment(value)
diff --git a/iOS/src/toga_iOS/widgets/scrollcontainer.py b/iOS/src/toga_iOS/widgets/scrollcontainer.py
index cb32c84c66..8cd35c4cb3 100644
--- a/iOS/src/toga_iOS/widgets/scrollcontainer.py
+++ b/iOS/src/toga_iOS/widgets/scrollcontainer.py
@@ -12,7 +12,7 @@ class TogaScrollView(UIScrollView):
 
     @objc_method
     def scrollViewDidScroll_(self, scrollView) -> None:
-        self.interface.on_scroll(None)
+        self.interface.on_scroll()
 
     @objc_method
     def refreshContent(self):
@@ -85,7 +85,7 @@ def set_vertical(self, value):
 
         # Disabling scrolling implies a position reset; that's a scroll event.
         if not value:
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
 
     def get_horizontal(self):
         return self._allow_horizontal
@@ -99,7 +99,7 @@ def set_horizontal(self, value):
 
         # Disabling scrolling implies a position reset; that's a scroll event.
         if not value:
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
 
     def get_horizontal_position(self):
         if not self.get_horizontal():
@@ -130,7 +130,7 @@ def set_position(self, horizontal_position, vertical_position):
         ):
             # iOS doesn't generate a scroll event unless the position actually changes.
             # Treat all scroll position assignments as a change.
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
         else:
             self.native.setContentOffset(
                 NSMakePoint(horizontal_position, vertical_position), animated=True
diff --git a/iOS/src/toga_iOS/widgets/selection.py b/iOS/src/toga_iOS/widgets/selection.py
index a0fa70439f..52af947f42 100644
--- a/iOS/src/toga_iOS/widgets/selection.py
+++ b/iOS/src/toga_iOS/widgets/selection.py
@@ -48,7 +48,7 @@ def pickerView_didSelectRow_inComponent_(
         item = self.interface.items[row]
         label = self.interface._title_for_item(item)
         self.native.text = label
-        self.interface.on_change(None)
+        self.interface.on_change()
 
 
 class Selection(Widget):
@@ -156,7 +156,7 @@ def select_item(self, index, item):
             self.native_picker.selectRow(index, inComponent=0, animated=False)
         else:
             self.native.text = ""
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_selected_index(self):
         if self._empty:
diff --git a/iOS/src/toga_iOS/widgets/slider.py b/iOS/src/toga_iOS/widgets/slider.py
index a6cec491e5..6db9758378 100644
--- a/iOS/src/toga_iOS/widgets/slider.py
+++ b/iOS/src/toga_iOS/widgets/slider.py
@@ -31,16 +31,16 @@ class TogaSlider(UISlider):
     @objc_method
     def onSlide_(self, obj) -> None:
         self.impl.value = self.interface._round_value(self.value)
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     @objc_method
     def onPress_(self, obj) -> None:
-        self.interface.on_press(None)
+        self.interface.on_press()
 
     @objc_method
     def onRelease_(self, obj) -> None:
         self.impl.set_value(self.impl.value)
-        self.interface.on_release(None)
+        self.interface.on_release()
 
 
 class Slider(Widget):
diff --git a/iOS/src/toga_iOS/widgets/switch.py b/iOS/src/toga_iOS/widgets/switch.py
index f82f02fa2f..9e42c7b016 100644
--- a/iOS/src/toga_iOS/widgets/switch.py
+++ b/iOS/src/toga_iOS/widgets/switch.py
@@ -19,7 +19,7 @@ class TogaSwitch(UISwitch):
 
     @objc_method
     def onPress_(self, obj) -> None:
-        self.interface.on_change(None)
+        self.interface.on_change()
 
 
 class Switch(Widget):
@@ -63,7 +63,7 @@ def set_value(self, value):
         old_value = self.native_switch.isOn()
         self.native_switch.setOn(value, animated=True)
         if value != old_value:
-            self.interface.on_change(None)
+            self.interface.on_change()
 
     def get_enabled(self):
         return self.native_switch.isEnabled()
diff --git a/iOS/src/toga_iOS/widgets/textinput.py b/iOS/src/toga_iOS/widgets/textinput.py
index 91f6649b69..62a080f041 100644
--- a/iOS/src/toga_iOS/widgets/textinput.py
+++ b/iOS/src/toga_iOS/widgets/textinput.py
@@ -25,20 +25,20 @@ class TogaTextField(UITextField):
 
     @objc_method
     def textFieldDidBeginEditing_(self, textField) -> None:
-        self.interface.on_gain_focus(None)
+        self.interface.on_gain_focus()
 
     @objc_method
     def textFieldDidChange_(self, textField) -> None:
-        self.interface.on_change(None)
+        self.interface.on_change()
         self.interface._validate()
 
     @objc_method
     def textFieldDidEndEditing_(self, textField) -> None:
-        self.interface.on_lose_focus(None)
+        self.interface.on_lose_focus()
 
     @objc_method
     def textFieldShouldReturn_(self, textField) -> bool:
-        self.interface.on_confirm(None)
+        self.interface.on_confirm()
         return True
 
 
@@ -127,7 +127,7 @@ def get_value(self):
 
     def set_value(self, value):
         self.native.text = value
-        self.interface.on_change(None)
+        self.interface.on_change()
         self.interface._validate()
 
     def set_alignment(self, value):
diff --git a/iOS/src/toga_iOS/widgets/webview.py b/iOS/src/toga_iOS/widgets/webview.py
index b3b8989dcf..7ef4852485 100644
--- a/iOS/src/toga_iOS/widgets/webview.py
+++ b/iOS/src/toga_iOS/widgets/webview.py
@@ -1,5 +1,4 @@
-from rubicon.objc import objc_method, objc_property, py_from_ns
-from rubicon.objc.runtime import objc_id
+from rubicon.objc import objc_id, objc_method, objc_property, py_from_ns
 from travertino.size import at_least
 
 from toga.widgets.webview import JavaScriptResult
@@ -30,7 +29,7 @@ class TogaWebView(WKWebView):
 
     @objc_method
     def webView_didFinishNavigation_(self, navigation) -> None:
-        self.interface.on_webview_load(self.interface)
+        self.interface.on_webview_load()
 
         if self.impl.loaded_future:
             self.impl.loaded_future.set_result(None)
diff --git a/iOS/src/toga_iOS/window.py b/iOS/src/toga_iOS/window.py
index 24aca68a48..7bd8bda595 100644
--- a/iOS/src/toga_iOS/window.py
+++ b/iOS/src/toga_iOS/window.py
@@ -1,8 +1,22 @@
+from rubicon.objc import (
+    Block,
+    NSPoint,
+    NSRect,
+    NSSize,
+    objc_id,
+)
+
 from toga_iOS.container import RootContainer
+from toga_iOS.images import nsdata_to_bytes
 from toga_iOS.libs import (
+    NSData,
     UIColor,
+    UIGraphicsImageRenderer,
+    UIImage,
     UIScreen,
     UIWindow,
+    core_graphics,
+    uikit,
 )
 
 
@@ -81,7 +95,7 @@ def set_app(self, app):
         pass
 
     def create_toolbar(self):
-        pass
+        pass  # pragma: no cover
 
     def show(self):
         self.native.makeKeyAndVisible()
@@ -100,3 +114,73 @@ def set_full_screen(self, is_full_screen):
 
     def close(self):
         pass
+
+    def get_image_data(self):
+        # This is... baroque.
+        #
+        # The iOS root container has an offset at the top, because the root view
+        # flows *under* the title bar. We don't want this in the screenshot.
+        #
+        # You can render a view using UIView.drawViewHierarchyInRect(), which
+        # takes a rect defining the region to be captured. It needs to be
+        # invoked in a graphics rendering context, which is initialized with a
+        # size. You'd *think* that you could specify the size of the final
+        # output image, and then render a rectangle that has that size at any
+        # position offset you choose... but no. If you do this, you end up with
+        # the *full* view, scaled to fit the provided size of the graphics
+        # context, with the offset being used in reverse to offset the origin of
+        # the scaling function. I'm sure this is useful to someone, but it's not
+        # useful to us.
+        #
+        # So - we capture the *entire* view, then crop to remove the section at
+        # the top of the image.
+        #
+        # Of course, the screenshot functionality uses UIImage, and UIImage has
+        # tooling to convert into PNG format... but doesn't contain *crop*
+        # functionality.
+        #
+        # So, we need to convert from UIImage to CGImage, and use Core Graphics
+        # to crop the image.
+        #
+        # Except that UIImage works in scaled coordinate, and Core Graphics
+        # works in native coordinates, so we need to do a size transformation
+        # along the way.
+        #
+        # I need a drink.
+
+        renderer = UIGraphicsImageRenderer.alloc().initWithSize(
+            self.container.native.bounds.size
+        )
+
+        def render(context):
+            self.container.native.drawViewHierarchyInRect(
+                self.container.native.bounds, afterScreenUpdates=True
+            )
+
+        # Render the full image
+        full_image = UIImage.imageWithData(
+            renderer.PNGDataWithActions(Block(render, None, objc_id))
+        )
+
+        # Get the size of the actual content (offsetting for the header) in raw coordinates.
+        container_bounds = self.container.content.native.bounds
+        image_bounds = NSRect(
+            NSPoint(
+                container_bounds.origin.x * UIScreen.mainScreen.scale,
+                (container_bounds.origin.y + self.container.top_offset)
+                * UIScreen.mainScreen.scale,
+            ),
+            NSSize(
+                container_bounds.size.width * UIScreen.mainScreen.scale,
+                container_bounds.size.height * UIScreen.mainScreen.scale,
+            ),
+        )
+
+        # Crop the image,
+        cropped_image = core_graphics.CGImageCreateWithImageInRect(
+            full_image.CGImage, image_bounds
+        )
+        # Convert back into a UIGraphics
+        final_image = UIImage.imageWithCGImage(cropped_image)
+        # Convert into PNG data.
+        return nsdata_to_bytes(NSData(uikit.UIImagePNGRepresentation(final_image)))
diff --git a/iOS/tests/__init__.py b/iOS/tests/__init__.py
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/iOS/tests/test_implementation.py b/iOS/tests/test_implementation.py
deleted file mode 100644
index bb39231812..0000000000
--- a/iOS/tests/test_implementation.py
+++ /dev/null
@@ -1,11 +0,0 @@
-import os
-
-from toga_dummy import test_implementation
-
-globals().update(
-    test_implementation.create_impl_tests(
-        os.path.abspath(
-            os.path.join(os.path.dirname(os.path.dirname(__file__)), "src", "toga_iOS")
-        )
-    )
-)
diff --git a/iOS/tests_backend/app.py b/iOS/tests_backend/app.py
index ec8a355599..98a4ba0369 100644
--- a/iOS/tests_backend/app.py
+++ b/iOS/tests_backend/app.py
@@ -1,5 +1,7 @@
 from pathlib import Path
 
+import pytest
+
 from toga_iOS.libs import (
     NSFileManager,
     NSSearchPathDirectory,
@@ -11,10 +13,13 @@
 
 
 class AppProbe(BaseProbe):
+    supports_key = False
+
     def __init__(self, app):
         super().__init__()
         self.app = app
-        assert isinstance(self.app._impl.native, UIApplication)
+        self.native = self.app._impl.native
+        assert isinstance(self.native, UIApplication)
 
     def get_path(self, search_path):
         file_manager = NSFileManager.defaultManager
@@ -38,3 +43,29 @@ def cache_path(self):
     @property
     def logs_path(self):
         return self.get_path(NSSearchPathDirectory.ApplicationSupport) / "Logs"
+
+    def assert_system_menus(self):
+        pytest.skip("Menus not implemented on iOS")
+
+    def activate_menu_about(self):
+        pytest.skip("Menus not implemented on iOS")
+
+    def activate_menu_visit_homepage(self):
+        pytest.skip("Menus not implemented on iOS")
+
+    def assert_menu_item(self, path, enabled):
+        pytest.skip("Menus not implemented on iOS")
+
+    def enter_background(self):
+        self.native.delegate.applicationWillResignActive(self.native)
+        self.native.delegate.applicationDidEnterBackground(self.native)
+
+    def enter_foreground(self):
+        self.native.delegate.applicationWillEnterForeground(self.native)
+
+    def terminate(self):
+        self.native.delegate.applicationWillTerminate(self.native)
+
+    def rotate(self):
+        self.native = self.app._impl.native
+        self.native.delegate.application(self.native, didChangeStatusBarOrientation=0)
diff --git a/iOS/tests_backend/probe.py b/iOS/tests_backend/probe.py
index e600fb2e43..c3a4653d11 100644
--- a/iOS/tests_backend/probe.py
+++ b/iOS/tests_backend/probe.py
@@ -1,6 +1,6 @@
 import asyncio
 
-from toga_iOS.libs import NSRunLoop
+from toga_iOS.libs import NSRunLoop, UIScreen
 
 
 class BaseProbe:
@@ -17,3 +17,8 @@ async def redraw(self, message=None, delay=None):
             # Running at "normal" speed, we need to release to the event loop
             # for at least one iteration. `runUntilDate:None` does this.
             NSRunLoop.currentRunLoop.runUntilDate(None)
+
+    def assert_image_size(self, image_size, size):
+        # Retina displays render images at a higher resolution than their reported size.
+        scale = int(UIScreen.mainScreen.scale)
+        assert image_size == (size[0] * scale, size[1] * scale)
diff --git a/iOS/tests_backend/widgets/canvas.py b/iOS/tests_backend/widgets/canvas.py
index 5d233f0862..45de11f784 100644
--- a/iOS/tests_backend/widgets/canvas.py
+++ b/iOS/tests_backend/widgets/canvas.py
@@ -4,7 +4,7 @@
 from PIL import Image
 from rubicon.objc import NSObject, NSPoint, ObjCClass, objc_method
 
-from toga_iOS.libs import UIScreen, UIView
+from toga_iOS.libs import UIView
 
 from .base import SimpleProbe
 
@@ -33,12 +33,6 @@ def reference_variant(self, reference):
     def get_image(self):
         return Image.open(BytesIO(self.impl.get_image_data()))
 
-    def assert_image_size(self, image, width, height):
-        # Retina displays render images at a higher resolution than their reported size.
-        scale = int(UIScreen.mainScreen.scale)
-        assert image.width == width * scale
-        assert image.height == height * scale
-
     async def mouse_press(self, x, y):
         touch = MockTouch.alloc().init()
         touches = NSSet.setWithObject(touch)
diff --git a/iOS/tests_backend/widgets/detailedlist.py b/iOS/tests_backend/widgets/detailedlist.py
index 16d990a507..f397797c9b 100644
--- a/iOS/tests_backend/widgets/detailedlist.py
+++ b/iOS/tests_backend/widgets/detailedlist.py
@@ -1,4 +1,5 @@
 import asyncio
+import platform
 
 from rubicon.objc.api import Block
 
@@ -48,9 +49,13 @@ def assert_cell_content(self, row, title, subtitle, icon=None):
 
     @property
     def max_scroll_position(self):
-        return max(
-            0, int(self.native.contentSize.height - self.native.frame.size.height)
-        )
+        max_value = int(self.native.contentSize.height - self.native.frame.size.height)
+        # The max value is a little higher on iOS 17.
+        # Not sure where the 34 extra pixels are coming from. It appears to be
+        # a constant, independent of the number of rows of data.
+        if int(platform.release().split(".")[0]) >= 17:
+            max_value += 34
+        return max(0, max_value)
 
     @property
     def scroll_position(self):
diff --git a/iOS/tests_backend/window.py b/iOS/tests_backend/window.py
index 199353464c..08f9a34295 100644
--- a/iOS/tests_backend/window.py
+++ b/iOS/tests_backend/window.py
@@ -1,6 +1,6 @@
 import pytest
 
-from toga_iOS.libs import UIWindow
+from toga_iOS.libs import UIApplication, UIWindow
 
 from .probe import BaseProbe
 
@@ -19,9 +19,14 @@ async def wait_for_window(self, message, minimize=False, full_screen=False):
 
     @property
     def content_size(self):
+        # Content height doesn't include the status bar or navigation bar.
         return (
             self.native.contentView.frame.size.width,
-            self.native.contentView.frame.size.height,
+            self.native.contentView.frame.size.height
+            - (
+                UIApplication.sharedApplication.statusBarFrame.size.height
+                + self.native.rootViewController.navigationBar.frame.size.height
+            ),
         )
 
     async def close_info_dialog(self, dialog):
@@ -69,3 +74,6 @@ async def close_open_file_dialog(self, dialog, result, multiple_select):
 
     async def close_select_folder_dialog(self, dialog, result, multiple_select):
         pytest.skip("Select Folder dialog not implemented on iOS")
+
+    def has_toolbar(self):
+        pytest.skip("Toolbars not implemented on iOS")
diff --git a/pyproject.toml b/pyproject.toml
index 2e117a0560..da9145dc6a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,6 +37,9 @@ exclude_lines = [
 profile = "black"
 split_on_trailing_comma = true
 combine_as_imports = true
+known_third_party = [
+    "android",  # isort defaults to making this first-party for some reason.
+]
 known_first_party = [
     "testbed",
     "toga",
@@ -53,7 +56,7 @@ known_first_party = [
 directory = "changes"
 package = "toga"
 package_dir = "core/src"
-filename = "docs/background/releases.rst"
+filename = "docs/background/project/releases.rst"
 title_format = "{version} ({project_date})"
 issue_format = "`#{issue} <https://github.com/beeware/toga/issues/{issue}>`__"
 template = "changes/template.rst"
diff --git a/testbed/src/testbed/app.py b/testbed/src/testbed/app.py
index 20ffd097fe..bddb6e0ac7 100644
--- a/testbed/src/testbed/app.py
+++ b/testbed/src/testbed/app.py
@@ -1,3 +1,5 @@
+from unittest.mock import Mock
+
 import toga
 
 
@@ -8,6 +10,76 @@ def startup(self):
         # suite exiting/crashing.
         self.returncode = -1
 
+        # Commands exist on the app's lifecycle, and the app API isn't designed to deal
+        # with destroying commands, so we create all the commands up front for the app
+        # to use.
+
+        self.cmd_action = Mock()
+        # A command with everything, in a group
+        group = toga.Group("Other")
+        self.cmd1 = toga.Command(
+            self.cmd_action,
+            "Full command",
+            icon=toga.Icon.DEFAULT_ICON,
+            tooltip="A full command definition",
+            shortcut=toga.Key.MOD_1 + "1",
+            group=group,
+        )
+        # A command with no tooltip, in the default group, with a non-printable shortcut
+        self.cmd2 = toga.Command(
+            self.cmd_action,
+            "No Tooltip",
+            icon=toga.Icon.DEFAULT_ICON,
+            shortcut=toga.Key.MOD_1 + toga.Key.DOWN,
+        )
+        # A command without an icon, in the default group
+        self.cmd3 = toga.Command(
+            self.cmd_action,
+            "No Icon",
+            tooltip="A command with no icon",
+            shortcut=toga.Key.MOD_1 + "3",
+        )
+        # A command in another section
+        self.cmd4 = toga.Command(
+            self.cmd_action,
+            "Sectioned",
+            icon=toga.Icon.DEFAULT_ICON,
+            tooltip="I'm in another section",
+            section=2,
+        )
+        # Submenus inside the "other" group
+        subgroup1 = toga.Group("Submenu1", section=2, parent=group)
+        subgroup1_1 = toga.Group("Submenu1 menu1", parent=subgroup1)
+        subgroup2 = toga.Group("Submenu2", section=2, parent=group)
+
+        # Items on submenu1
+        # An item that is disabled by default
+        self.disabled_cmd = toga.Command(
+            self.cmd_action,
+            "Disabled",
+            enabled=False,
+            group=subgroup1,
+        )
+        # An item that has no action
+        self.no_action_cmd = toga.Command(None, "No Action", group=subgroup1)
+        # An item deep in a menu
+        self.deep_cmd = toga.Command(self.cmd_action, "Deep", group=subgroup1_1)
+
+        # Items on submenu2
+        self.cmd5 = toga.Command(self.cmd_action, "Jiggle", group=subgroup2)
+
+        # Add all the commands
+        self.commands.add(
+            self.cmd1,
+            self.cmd2,
+            self.cmd3,
+            self.cmd4,
+            self.disabled_cmd,
+            self.no_action_cmd,
+            self.deep_cmd,
+            self.cmd5,
+        )
+
         self.main_window = toga.MainWindow(title=self.formal_name)
         self.main_window.content = toga.Box(
             children=[
diff --git a/testbed/src/testbed/resources/canvas/ellipse_path.png b/testbed/src/testbed/resources/canvas/ellipse_path.png
new file mode 100644
index 0000000000..cf520147a0
Binary files /dev/null and b/testbed/src/testbed/resources/canvas/ellipse_path.png differ
diff --git a/testbed/tests/conftest.py b/testbed/tests/conftest.py
index b169c0a206..09c442f667 100644
--- a/testbed/tests/conftest.py
+++ b/testbed/tests/conftest.py
@@ -6,6 +6,8 @@
 from pytest import fixture, register_assert_rewrite, skip
 
 import toga
+from toga.colors import GOLDENROD
+from toga.style import Pack
 
 # Ideally, we'd register rewrites for "tests" and get all the submodules
 # recursively; however we've already imported "tests", so that raises a warning.
@@ -50,6 +52,21 @@ def main_window(app):
     return app.main_window
 
 
+@fixture(scope="session")
+async def main_window_probe(app, main_window):
+    old_content = main_window.content
+
+    # Put something in the content window so that we know it's an app test
+    main_window.content = toga.Box(style=Pack(background_color=GOLDENROD))
+
+    module = import_module("tests_backend.window")
+    if app.run_slow:
+        print("\nConstructing Window probe")
+    yield getattr(module, "WindowProbe")(app, main_window)
+
+    main_window.content = old_content
+
+
 # Controls the event loop used by pytest-asyncio.
 @fixture(scope="session")
 def event_loop(app):
diff --git a/testbed/tests/test_app.py b/testbed/tests/test_app.py
new file mode 100644
index 0000000000..326860a6a8
--- /dev/null
+++ b/testbed/tests/test_app.py
@@ -0,0 +1,552 @@
+from unittest.mock import Mock
+
+import pytest
+
+import toga
+from toga.colors import CORNFLOWERBLUE, FIREBRICK, REBECCAPURPLE
+from toga.style.pack import Pack
+
+from .test_window import window_probe
+
+
+@pytest.fixture
+def mock_app_exit(monkeypatch, app):
+    # We can't actually exit during a test, so monkeypatch the exit met"""
+    app_exit = Mock()
+    monkeypatch.setattr(toga.App, "exit", app_exit)
+    return app_exit
+
+
+# Mobile platforms have different windowing characterics, so they have different tests.
+if toga.platform.current_platform in {"iOS", "android"}:
+    ####################################################################################
+    # Mobile platform tests
+    ####################################################################################
+
+    async def test_show_hide_cursor(app):
+        """The app cursor methods can be invoked"""
+        # Invoke the methods to verify the endpoints exist. However, they're no-ops,
+        # so there's nothing to test.
+        app.show_cursor()
+        app.hide_cursor()
+
+    async def test_full_screen(app):
+        """Window can be made full screen"""
+        # Invoke the methods to verify the endpoints exist. However, they're no-ops,
+        # so there's nothing to test.
+        app.set_full_screen(app.current_window)
+        app.exit_full_screen()
+
+    async def test_current_window(app, main_window, main_window_probe):
+        """The current window can be retrieved"""
+        assert app.current_window == main_window
+
+        # Explicitly set the current window
+        app.current_window = main_window
+        await main_window_probe.wait_for_window("Main window is still current")
+        assert app.current_window == main_window
+
+    async def test_app_lifecycle(app, app_probe):
+        """Application lifecycle can be exercised"""
+        app_probe.enter_background()
+        await app_probe.redraw("App pre-background logic has been invoked")
+
+        app_probe.enter_foreground()
+        await app_probe.redraw("App restoration logic has been invoked")
+
+        app_probe.terminate()
+        await app_probe.redraw("App pre-termination logic has been invoked")
+
+    async def test_device_rotation(app, app_probe):
+        """App responds to device rotation"""
+        app_probe.rotate()
+        await app_probe.redraw("Device has been rotated")
+
+else:
+    ####################################################################################
+    # Desktop platform tests
+    ####################################################################################
+
+    async def test_exit_on_close_main_window(app, main_window_probe, mock_app_exit):
+        """An app can be exited by closing the main window"""
+        on_exit_handler = Mock(return_value=False)
+        app.on_exit = on_exit_handler
+
+        # Close the main window
+        main_window_probe.close()
+        await main_window_probe.redraw("Main window close requested, but rejected")
+
+        # on_exit_handler was invoked, rejecting the close; so the app won't be closed
+        on_exit_handler.assert_called_once_with(app)
+        mock_app_exit.assert_not_called()
+
+        # Reset and try again, this time allowing the exit
+        on_exit_handler.reset_mock()
+        on_exit_handler.return_value = True
+        main_window_probe.close()
+        await main_window_probe.redraw("Main window close requested, and accepted")
+
+        # on_exit_handler was invoked and accepted, so the mocked exit() was called.
+        on_exit_handler.assert_called_once_with(app)
+        mock_app_exit.assert_called_once_with()
+
+    async def test_menu_exit(app, app_probe, mock_app_exit):
+        """An app can be exited by using the menu item"""
+        on_exit_handler = Mock(return_value=False)
+        app.on_exit = on_exit_handler
+
+        # Close the main window
+        app_probe.activate_menu_exit()
+        await app_probe.redraw("Exit selected from menu, but rejected")
+
+        # on_exit_handler was invoked, rejecting the close; so the app won't be closed
+        on_exit_handler.assert_called_once_with(app)
+        mock_app_exit.assert_not_called()
+
+        # Reset and try again, this time allowing the exit
+        on_exit_handler.reset_mock()
+        on_exit_handler.return_value = True
+        app_probe.activate_menu_exit()
+        await app_probe.redraw("Exit selected from menu, and accepted")
+
+        # on_exit_handler was invoked and accepted, so the mocked exit() was called.
+        on_exit_handler.assert_called_once_with(app)
+        mock_app_exit.assert_called_once_with()
+
+    async def test_menu_close_windows(monkeypatch, app, app_probe, mock_app_exit):
+        try:
+            window1 = toga.Window("Test Window 1", position=(150, 150), size=(200, 200))
+            window1.content = toga.Box(style=Pack(background_color=REBECCAPURPLE))
+            window2 = toga.Window("Test Window 2", position=(400, 150), size=(200, 200))
+            window2.content = toga.Box(style=Pack(background_color=CORNFLOWERBLUE))
+            window3 = toga.Window("Test Window 3", position=(300, 400), size=(200, 200))
+            window3.content = toga.Box(style=Pack(background_color=FIREBRICK))
+
+            window1.show()
+            window2.show()
+            window3.show()
+
+            app.current_window = window2
+
+            await app_probe.redraw("Extra windows added")
+
+            app_probe.activate_menu_close_window()
+            await app_probe.redraw("Window 2 closed")
+
+            assert window2 not in app.windows
+
+            app_probe.activate_menu_close_all_windows()
+            await app_probe.redraw("All windows closed")
+
+            # Close all windows will attempt to close the main window as well.
+            # This would be an app exit, but we can't allow that; so, the only
+            # window that *actually* remains will be the main window.
+            mock_app_exit.assert_called_once_with()
+            assert window1 not in app.windows
+            assert window2 not in app.windows
+            assert window3 not in app.windows
+
+            await app_probe.redraw("Extra windows closed")
+
+            # Now that we've "closed" all the windows, we're in a state where there
+            # aren't any windows. Patch get_current_window to reflect this.
+            monkeypatch.setattr(
+                app._impl,
+                "get_current_window",
+                Mock(return_value=None),
+            )
+            app_probe.activate_menu_close_window()
+            await app_probe.redraw("No windows; Close Window is a no-op")
+
+            app_probe.activate_menu_minimize()
+            await app_probe.redraw("No windows; Minimize is a no-op")
+
+        finally:
+            if window1 in app.windows:
+                window1.close()
+            if window2 in app.windows:
+                window2.close()
+            if window3 in app.windows:
+                window3.close()
+
+    async def test_menu_minimize(app, app_probe):
+        try:
+            window1 = toga.Window("Test Window 1", position=(150, 150), size=(200, 200))
+            window1.content = toga.Box(style=Pack(background_color=REBECCAPURPLE))
+            window1.show()
+
+            window1_probe = window_probe(app, window1)
+
+            app.current_window = window1
+            await app_probe.redraw("Extra window added")
+
+            app_probe.activate_menu_minimize()
+
+            await window1_probe.wait_for_window("Extra window minimized", minimize=True)
+            assert window1_probe.is_minimized
+        finally:
+            window1.close()
+
+    async def test_full_screen(app, app_probe):
+        """Window can be made full screen"""
+        try:
+            window1 = toga.Window("Test Window 1", position=(150, 150), size=(200, 200))
+            window1.content = toga.Box(style=Pack(background_color=REBECCAPURPLE))
+            window2 = toga.Window("Test Window 2", position=(400, 150), size=(200, 200))
+            window2.content = toga.Box(style=Pack(background_color=CORNFLOWERBLUE))
+            window1_probe = window_probe(app, window1)
+            window2_probe = window_probe(app, window2)
+
+            window1.show()
+            window2.show()
+            await app_probe.redraw("Extra windows are visible")
+
+            assert not app.is_full_screen
+            assert not app_probe.is_full_screen(window1)
+            assert not app_probe.is_full_screen(window2)
+            initial_content1_size = app_probe.content_size(window1)
+            initial_content2_size = app_probe.content_size(window2)
+
+            # Make window 2 full screen via the app
+            app.set_full_screen(window2)
+            await window2_probe.wait_for_window(
+                "Second extra window is full screen",
+                full_screen=True,
+            )
+            assert app.is_full_screen
+
+            assert not app_probe.is_full_screen(window1)
+            assert app_probe.content_size(window1) == initial_content1_size
+
+            assert app_probe.is_full_screen(window2)
+            assert app_probe.content_size(window2)[0] > 1000
+            assert app_probe.content_size(window2)[1] > 700
+
+            # Make window 1 full screen via the app, window 2 no longer full screen
+            app.set_full_screen(window1)
+            await window1_probe.wait_for_window(
+                "First extra window is full screen",
+                full_screen=True,
+            )
+            assert app.is_full_screen
+
+            assert app_probe.is_full_screen(window1)
+            assert app_probe.content_size(window1)[0] > 1000
+            assert app_probe.content_size(window1)[1] > 700
+
+            assert not app_probe.is_full_screen(window2)
+            assert app_probe.content_size(window2) == initial_content2_size
+
+            # Exit full screen
+            app.exit_full_screen()
+            await window1_probe.wait_for_window(
+                "No longer full screen",
+                full_screen=True,
+            )
+
+            assert not app.is_full_screen
+
+            assert not app_probe.is_full_screen(window1)
+            assert app_probe.content_size(window1) == initial_content1_size
+
+            assert not app_probe.is_full_screen(window2)
+            assert app_probe.content_size(window2) == initial_content2_size
+
+            # Go full screen again on window 1
+            app.set_full_screen(window1)
+            # A longer delay to allow for genie animations
+            await window1_probe.wait_for_window(
+                "First extra window is full screen",
+                full_screen=True,
+            )
+            assert app.is_full_screen
+
+            assert app_probe.is_full_screen(window1)
+            assert app_probe.content_size(window1)[0] > 1000
+            assert app_probe.content_size(window1)[1] > 700
+
+            assert not app_probe.is_full_screen(window2)
+            assert app_probe.content_size(window2) == initial_content2_size
+
+            # Exit full screen by passing no windows
+            app.set_full_screen()
+
+            await window1_probe.wait_for_window(
+                "No longer full screen",
+                full_screen=True,
+            )
+            assert not app.is_full_screen
+
+            assert not app_probe.is_full_screen(window1)
+            assert app_probe.content_size(window1) == initial_content1_size
+
+            assert not app_probe.is_full_screen(window2)
+            assert app_probe.content_size(window2) == initial_content2_size
+
+        finally:
+            window1.close()
+            window2.close()
+
+    async def test_show_hide_cursor(app, app_probe):
+        """The app cursor can be hidden and shown"""
+        assert app_probe.is_cursor_visible
+        app.hide_cursor()
+        await app_probe.redraw("Cursor is hidden")
+        assert not app_probe.is_cursor_visible
+
+        # Hiding again can't make it more hidden
+        app.hide_cursor()
+        await app_probe.redraw("Cursor is still hidden")
+        assert not app_probe.is_cursor_visible
+
+        # Show the cursor again
+        app.show_cursor()
+        await app_probe.redraw("Cursor is visible")
+        assert app_probe.is_cursor_visible
+
+        # Showing again can't make it more visible
+        app.show_cursor()
+        await app_probe.redraw("Cursor is still visible")
+        assert app_probe.is_cursor_visible
+
+    async def test_current_window(app, app_probe, main_window):
+        """The current window can be retrieved."""
+        try:
+            assert app.current_window == main_window
+
+            # When all windows are hidden, WinForms and Cocoa return None, while GTK
+            # returns the last active window.
+            main_window.hide()
+            assert app.current_window in [None, main_window]
+
+            main_window.show()
+            assert app.current_window == main_window
+        finally:
+            main_window.show()
+
+        try:
+            window1 = toga.Window("Test Window 1", position=(150, 150), size=(200, 200))
+            window1.content = toga.Box(style=Pack(background_color=REBECCAPURPLE))
+            window2 = toga.Window("Test Window 2", position=(400, 150), size=(200, 200))
+            window2.content = toga.Box(style=Pack(background_color=CORNFLOWERBLUE))
+            window3 = toga.Window("Test Window 3", position=(300, 400), size=(200, 200))
+            window3.content = toga.Box(style=Pack(background_color=FIREBRICK))
+
+            # We don't need to probe anything window specific; we just need
+            # a window probe to enforce appropriate delays.
+            window1_probe = window_probe(app, window1)
+
+            window1.show()
+            window2.show()
+            window3.show()
+
+            await window1_probe.wait_for_window("Extra windows added")
+
+            app.current_window = window2
+            await window1_probe.wait_for_window("Window 2 is current")
+            assert app.current_window == window2
+
+            app.current_window = window3
+            await window1_probe.wait_for_window("Window 3 is current")
+            assert app.current_window == window3
+
+            # app_probe.platform tests?
+        finally:
+            window1.close()
+            window2.close()
+            window3.close()
+
+
+async def test_main_window_toolbar(app, main_window, main_window_probe):
+    """A toolbar can be added to a main window"""
+    # Add some items to show the toolbar
+    assert not main_window_probe.has_toolbar()
+    main_window.toolbar.add(app.cmd1, app.cmd2)
+
+    # Add some more items to an existing toolbar
+    main_window.toolbar.add(app.cmd3, app.cmd4)
+
+    await main_window_probe.redraw("Main window has a toolbar")
+    assert main_window_probe.has_toolbar()
+    # Ordering is lexicographical for cmd 2 and 3.
+    main_window_probe.assert_toolbar_item(
+        0,
+        label="Full command",
+        tooltip="A full command definition",
+        has_icon=True,
+        enabled=True,
+    )
+    main_window_probe.assert_is_toolbar_separator(1)
+    main_window_probe.assert_toolbar_item(
+        2,
+        label="No Icon",
+        tooltip="A command with no icon",
+        has_icon=False,
+        enabled=True,
+    )
+    main_window_probe.assert_toolbar_item(
+        3,
+        label="No Tooltip",
+        tooltip=None,
+        has_icon=True,
+        enabled=True,
+    )
+    main_window_probe.assert_is_toolbar_separator(4, section=True)
+    main_window_probe.assert_toolbar_item(
+        5,
+        label="Sectioned",
+        tooltip="I'm in another section",
+        has_icon=True,
+        enabled=True,
+    )
+
+    # Press the first toolbar button
+    main_window_probe.press_toolbar_button(0)
+    await main_window_probe.redraw("Command 1 invoked")
+    app.cmd_action.assert_called_once_with(app.cmd1)
+    app.cmd_action.reset_mock()
+
+    # Disable the first toolbar button
+    app.cmd1.enabled = False
+    await main_window_probe.redraw("Command 1 disabled")
+    main_window_probe.assert_toolbar_item(
+        0,
+        label="Full command",
+        tooltip="A full command definition",
+        has_icon=True,
+        enabled=False,
+    )
+
+    # Re-enable the first toolbar button
+    app.cmd1.enabled = True
+    await main_window_probe.redraw("Command 1 re-enabled")
+    main_window_probe.assert_toolbar_item(
+        0,
+        label="Full command",
+        tooltip="A full command definition",
+        has_icon=True,
+        enabled=True,
+    )
+
+    # Remove the toolbar
+    main_window.toolbar.clear()
+    await main_window_probe.redraw("Main window has no toolbar")
+    assert not main_window_probe.has_toolbar()
+
+    # Removing it again should have no effect
+    main_window.toolbar.clear()
+    await main_window_probe.redraw("Main window has no toolbar")
+    assert not main_window_probe.has_toolbar()
+
+
+async def test_system_menus(app_probe):
+    """System-specific menus behave as expected"""
+    # Check that the system menus (which can be platform specific) exist.
+    app_probe.assert_system_menus()
+
+
+async def test_menu_about(monkeypatch, app, app_probe):
+    """The about menu can be displayed"""
+    app_probe.activate_menu_about()
+    # When in CI, Cocoa needs a little time to guarantee the dialog is displayed.
+    await app_probe.redraw("About dialog shown", delay=0.1)
+
+    await app_probe.close_about_dialog()
+    await app_probe.redraw("About dialog destroyed")
+
+    # Make the app definition minimal to verify the dialog still displays
+    monkeypatch.setattr(app, "_author", None)
+    monkeypatch.setattr(app, "_version", None)
+    monkeypatch.setattr(app, "_home_page", None)
+    monkeypatch.setattr(app, "_description", None)
+
+    app_probe.activate_menu_about()
+    # When in CI, Cocoa needs a little time to guarantee the dialog is displayed.
+    await app_probe.redraw("About dialog with no details shown", delay=0.1)
+
+    await app_probe.close_about_dialog()
+    await app_probe.redraw("About dialog with no details destroyed")
+
+
+async def test_menu_visit_homepage(monkeypatch, app, app_probe):
+    """The visit homepage menu item can be used"""
+    # We don't actually want to open a web browser; just check that the interface method
+    # was invoked.
+    visit_homepage = Mock()
+    monkeypatch.setattr(app, "visit_homepage", visit_homepage)
+
+    app_probe.activate_menu_visit_homepage()
+
+    # Browser opened
+    visit_homepage.assert_called_once_with()
+
+
+async def test_menu_items(app, app_probe):
+    """Menu items can be created, disabled and invoked"""
+
+    app_probe.assert_menu_item(
+        ["Other", "Full command"],
+        enabled=True,
+    )
+    app_probe.assert_menu_item(
+        ["Other", "Submenu1", "Disabled"],
+        enabled=False,
+    )
+    app_probe.assert_menu_item(
+        ["Other", "Submenu1", "No Action"],
+        enabled=False,
+    )
+    app_probe.assert_menu_item(
+        ["Other", "Submenu1", "Submenu1 menu1", "Deep"],
+        enabled=True,
+    )
+
+    app_probe.assert_menu_item(
+        ["Commands", "No Tooltip"],
+        enabled=True,
+    )
+    app_probe.assert_menu_item(
+        ["Commands", "No Icon"],
+        enabled=True,
+    )
+    app_probe.assert_menu_item(
+        ["Commands", "Sectioned"],
+        enabled=True,
+    )
+
+    # Enabled the disabled items
+    app.disabled_cmd.enabled = True
+    app.no_action_cmd.enabled = True
+    await app_probe.redraw("Menu items enabled")
+
+    app_probe.assert_menu_item(
+        ["Other", "Submenu1", "Disabled"],
+        enabled=True,
+    )
+    # Item has no action - it can't be enabled
+    app_probe.assert_menu_item(
+        ["Other", "Submenu1", "No Action"],
+        enabled=False,
+    )
+
+    # Dislble the items
+    app.disabled_cmd.enabled = False
+    app.no_action_cmd.enabled = False
+
+    await app_probe.redraw("Menu item disabled again")
+    app_probe.assert_menu_item(
+        ["Other", "Submenu1", "Disabled"],
+        enabled=False,
+    )
+    app_probe.assert_menu_item(
+        ["Other", "Submenu1", "No Action"],
+        enabled=False,
+    )
+
+
+async def test_beep(app):
+    """The machine can go Bing!"""
+    # This isn't a very good test. It ensures coverage, which verifies that the method
+    # can be invoked without raising an error, but there's no way to verify that the app
+    # actually made a noise.
+    app.beep()
diff --git a/testbed/tests/test_images.py b/testbed/tests/test_images.py
index 7f9b9717d3..dd38d8e26b 100644
--- a/testbed/tests/test_images.py
+++ b/testbed/tests/test_images.py
@@ -47,6 +47,12 @@ async def test_data_image(app):
     assert image.width == 110
     assert image.height == 30
 
+    # Construct a second image from the first image's data
+    image2 = toga.Image(data=image.data)
+
+    assert image2.width == 110
+    assert image2.height == 30
+
 
 async def test_bad_image_data(app):
     "If data isn't a valid image, an error is raised"
diff --git a/testbed/tests/test_keys.py b/testbed/tests/test_keys.py
new file mode 100644
index 0000000000..76c662f76e
--- /dev/null
+++ b/testbed/tests/test_keys.py
@@ -0,0 +1,49 @@
+import pytest
+
+from toga.keys import Key
+
+
+@pytest.mark.parametrize(
+    "key_combo, key_data",
+    [
+        # lower case
+        ("a", {"key": Key.A, "modifiers": set()}),
+        # upper case
+        ("A", {"key": Key.A, "modifiers": {Key.SHIFT}}),
+        # single modifier
+        (Key.MOD_1 + "a", {"key": Key.A, "modifiers": {Key.MOD_1}}),
+        (Key.MOD_2 + "a", {"key": Key.A, "modifiers": {Key.MOD_2}}),
+        (Key.MOD_3 + "a", {"key": Key.A, "modifiers": {Key.MOD_3}}),
+        # modifier combinations
+        (
+            Key.MOD_1 + Key.MOD_2 + "a",
+            {"key": Key.A, "modifiers": {Key.MOD_1, Key.MOD_2}},
+        ),
+        (
+            Key.MOD_2 + Key.MOD_1 + "a",
+            {"key": Key.A, "modifiers": {Key.MOD_1, Key.MOD_2}},
+        ),
+        (
+            Key.MOD_1 + Key.MOD_2 + Key.MOD_3 + "A",
+            {"key": Key.A, "modifiers": {Key.MOD_1, Key.MOD_2, Key.MOD_3, Key.SHIFT}},
+        ),
+        # A key which is shift modified
+        ("1", {"key": Key._1, "modifiers": set()}),
+        ("!", {"key": Key.EXCLAMATION, "modifiers": set()}),
+        # Special keys
+        (Key.F5, {"key": Key.F5, "modifiers": set()}),
+        (Key.HOME, {"key": Key.HOME, "modifiers": set()}),
+        (Key.HOME + Key.MOD_1, {"key": Key.HOME, "modifiers": {Key.MOD_1}}),
+    ],
+)
+def test_key_combinations(app_probe, key_combo, key_data):
+    """Key combinations can be round tripped"""
+
+    if not app_probe.supports_key:
+        pytest.xfail("This backend doesn't use keyboard shortcuts")
+
+    if (Key.MOD_3 in key_data["modifiers"]) and not app_probe.supports_key_mod3:
+        with pytest.raises(ValueError):
+            app_probe.keystroke(key_combo)
+    else:
+        assert app_probe.keystroke(key_combo) == key_data
diff --git a/testbed/tests/test_window.py b/testbed/tests/test_window.py
index 11acca0453..8b7fe877c0 100644
--- a/testbed/tests/test_window.py
+++ b/testbed/tests/test_window.py
@@ -35,11 +35,6 @@ async def second_window_probe(app, second_window):
         second_window.close()
 
 
-@pytest.fixture
-async def main_window_probe(app, main_window):
-    yield window_probe(app, main_window)
-
-
 async def test_title(main_window, main_window_probe):
     """The title of a window can be changed"""
     original_title = main_window.title
@@ -247,6 +242,20 @@ async def test_secondary_window_cleanup(app_probe):
         assert window_ref() is None
         assert impl_ref() is None
 
+    @pytest.mark.parametrize(
+        "second_window_kwargs",
+        [dict(title="Secondary Window", position=(200, 300), size=(400, 200))],
+    )
+    async def test_secondary_window_toolbar(app, second_window, second_window_probe):
+        """A toolbar can be added to a secondary window"""
+        second_window.toolbar.add(app.cmd1)
+
+        # Window doesn't have content. This is intentional.
+        second_window.show()
+
+        assert second_window_probe.has_toolbar()
+        await second_window_probe.redraw("Secondary window has a toolbar")
+
     @pytest.mark.parametrize(
         "second_window_kwargs",
         [dict(title="Not Resizable", resizable=False, position=(200, 150))],
@@ -471,6 +480,13 @@ async def test_full_screen(second_window, second_window_probe):
         assert second_window_probe.content_size == initial_content_size
 
 
+async def test_as_image(main_window, main_window_probe):
+    """The window can be captured as a screenshot"""
+
+    screenshot = main_window.as_image()
+    main_window_probe.assert_image_size(screenshot.size, main_window_probe.content_size)
+
+
 ########################################################################################
 # Dialog tests
 ########################################################################################
diff --git a/testbed/tests/testbed.py b/testbed/tests/testbed.py
index cc8e0489aa..03f983431e 100644
--- a/testbed/tests/testbed.py
+++ b/testbed/tests/testbed.py
@@ -75,8 +75,8 @@ def run_tests(app, cov, args, report_coverage, run_slow):
                 )
                 if total < 100.0:
                     print("Test coverage is incomplete")
-                    # Uncomment the next line to enforce test coverage
-                    # TODO: app.returncode = 1
+                    app.returncode = 1
+
     except BaseException:
         traceback.print_exc()
         app.returncode = 1
@@ -161,7 +161,10 @@ def get_terminal_size(*args, **kwargs):
             report_coverage=report_coverage,
         )
     )
-    thread.start()
+    # Queue a background task to run that will start the main thread. We do this,
+    # instead of just starting the thread directly, so that we can make sure the App has
+    # been fully initialized, and the event loop is running.
+    app.add_background_task(lambda app, **kwargs: thread.start())
 
     # Start the test app.
     app.main_loop()
diff --git a/testbed/tests/widgets/conftest.py b/testbed/tests/widgets/conftest.py
index f63ef067df..db6a90c3ea 100644
--- a/testbed/tests/widgets/conftest.py
+++ b/testbed/tests/widgets/conftest.py
@@ -20,7 +20,7 @@ async def probe(main_window, widget):
     box = toga.Box(children=[widget])
     main_window.content = box
     probe = get_probe(widget)
-    await probe.redraw(f"Constructing {widget.__class__.__name__} probe")
+    await probe.redraw(f"\nConstructing {widget.__class__.__name__} probe")
     probe.assert_container(box)
     yield probe
 
diff --git a/testbed/tests/widgets/properties.py b/testbed/tests/widgets/properties.py
index 0c7b335cbb..0b376e7862 100644
--- a/testbed/tests/widgets/properties.py
+++ b/testbed/tests/widgets/properties.py
@@ -74,7 +74,7 @@ async def test_focus(widget, probe, other, other_probe, verify_focus_handlers):
     assert not other_probe.has_focus
 
     if verify_focus_handlers:
-        on_gain_handler.assert_called_once()
+        on_gain_handler.assert_called_once_with(widget)
 
         # Reset the mock so it can be tested again
         on_gain_handler.reset_mock()
@@ -93,7 +93,7 @@ async def test_focus(widget, probe, other, other_probe, verify_focus_handlers):
     assert other_probe.has_focus
 
     if verify_focus_handlers:
-        on_lose_handler.assert_called_once()
+        on_lose_handler.assert_called_once_with(widget)
 
 
 async def test_focus_noop(widget, probe, other, other_probe):
diff --git a/testbed/tests/widgets/test_base.py b/testbed/tests/widgets/test_base.py
index 00facca865..67ca42fb06 100644
--- a/testbed/tests/widgets/test_base.py
+++ b/testbed/tests/widgets/test_base.py
@@ -153,3 +153,17 @@ async def test_parenting(widget, probe):
     probe.assert_layout(position=(0, 0), size=(100, 200))
     other_probe.assert_layout(position=(150, 0), size=(100, 200))
     child_probe.assert_layout(position=(100, 0), size=(50, 75))
+
+
+async def test_tab_index(widget, probe, other):
+    if toga.platform.current_platform not in {"windows"}:
+        assert widget.tab_index is None
+        assert other.tab_index is None
+    else:
+        assert widget.tab_index == 1
+        assert other.tab_index == 2
+
+        widget.tab_index = 4
+        other.tab_index = 2
+        assert widget.tab_index == 4
+        assert other.tab_index == 2
diff --git a/testbed/tests/widgets/test_canvas.py b/testbed/tests/widgets/test_canvas.py
index a01b90d280..a7b723ce0c 100644
--- a/testbed/tests/widgets/test_canvas.py
+++ b/testbed/tests/widgets/test_canvas.py
@@ -1,5 +1,5 @@
 import math
-from math import pi
+from math import pi, radians
 from unittest.mock import Mock, call
 
 import pytest
@@ -116,6 +116,7 @@ async def test_resize(widget, probe, on_resize_handler):
     # the most recent of which has a large
     await probe.redraw("Canvas should be full size of window")
     assert on_resize_handler.call_count >= 1
+    assert on_resize_handler.call_args.args == (widget,)
     assert on_resize_handler.call_args.kwargs["width"] > 300
     assert on_resize_handler.call_args.kwargs["height"] > 300
     on_resize_handler.reset()
@@ -123,6 +124,7 @@ async def test_resize(widget, probe, on_resize_handler):
     widget.style.width = 100
     await probe.redraw("Canvas should be tall and narrow")
     assert on_resize_handler.call_count >= 1
+    assert on_resize_handler.call_args.args == (widget,)
     assert on_resize_handler.call_args.kwargs["width"] == 100
     assert on_resize_handler.call_args.kwargs["height"] > 300
     on_resize_handler.reset()
@@ -130,6 +132,7 @@ async def test_resize(widget, probe, on_resize_handler):
     widget.style.height = 100
     await probe.redraw("Canvas should be small")
     assert on_resize_handler.call_count >= 1
+    assert on_resize_handler.call_args.args == (widget,)
     assert on_resize_handler.call_args.kwargs["width"] == 100
     assert on_resize_handler.call_args.kwargs["height"] == 100
     on_resize_handler.reset()
@@ -137,6 +140,7 @@ async def test_resize(widget, probe, on_resize_handler):
     del widget.style.width
     await probe.redraw("Canvas should be width of the screen")
     assert on_resize_handler.call_count >= 1
+    assert on_resize_handler.call_args.args == (widget,)
     assert on_resize_handler.call_args.kwargs["width"] > 300
     assert on_resize_handler.call_args.kwargs["height"] == 100
     on_resize_handler.reset()
@@ -227,7 +231,7 @@ async def test_image_data(canvas, probe):
 
     # Cloned image is the right size. The platform may do DPI scaling;
     # let the probe determine the correct scaled size.
-    probe.assert_image_size(image, 200, 200)
+    probe.assert_image_size(image.size, (200, 200))
 
 
 def assert_reference(probe, reference, threshold=0.0):
@@ -307,6 +311,8 @@ async def test_paths(canvas, probe):
 
     # A stroked path requires an explicit close. For an open stroke, see test_stroke.
     canvas.context.begin_path()
+    # When there are two consecutive move_tos, the first one should leave no trace.
+    canvas.context.move_to(140, 140)
     canvas.context.move_to(180, 180)
     canvas.context.line_to(180, 60)
     canvas.context.line_to(60, 180)
@@ -318,6 +324,12 @@ async def test_paths(canvas, probe):
     canvas.context.close_path()
     canvas.context.stroke(RED)
 
+    # A path containing only move_to commands should not appear.
+    canvas.context.begin_path()
+    canvas.context.move_to(140, 140)
+    canvas.context.move_to(160, 160)
+    canvas.context.stroke(RED)
+
     await probe.redraw("Pair of triangles should be drawn")
     assert_reference(probe, "paths", threshold=0.04)
 
@@ -435,6 +447,37 @@ async def test_ellipse(canvas, probe):
     assert_reference(probe, "ellipse", threshold=0.04)
 
 
+async def test_ellipse_path(canvas, probe):
+    "An elliptical arc can be connected to other segments of a path"
+
+    context = canvas.context
+    ellipse_args = dict(x=100, y=100, radiusx=70, radiusy=40, rotation=radians(30))
+
+    # Start of path -> arc
+    context.ellipse(**ellipse_args, startangle=radians(80), endangle=radians(160))
+    # Arc -> arc
+    context.ellipse(**ellipse_args, startangle=radians(220), endangle=radians(260))
+    context.stroke()
+
+    context.begin_path()
+    context.move_to(120, 20)
+    # Move -> arc
+    context.ellipse(**ellipse_args, startangle=radians(280), endangle=radians(340))
+    # Arc -> line
+    context.line_to(180, 50)
+    context.stroke(RED)
+
+    context.begin_path()
+    context.move_to(180, 180)
+    context.line_to(180, 160)
+    # Line -> arc
+    context.ellipse(**ellipse_args, startangle=radians(10), endangle=radians(60))
+    context.stroke(CORNFLOWERBLUE)
+
+    await probe.redraw("Broken ellipse with connected lines should be drawn")
+    assert_reference(probe, "ellipse_path", threshold=0.04)
+
+
 async def test_rect(canvas, probe):
     "A rectangle can be drawn"
 
diff --git a/testbed/tests/widgets/test_detailedlist.py b/testbed/tests/widgets/test_detailedlist.py
index 60188db317..d729333af0 100644
--- a/testbed/tests/widgets/test_detailedlist.py
+++ b/testbed/tests/widgets/test_detailedlist.py
@@ -248,7 +248,7 @@ def add_row(event_widget, **kwargs):
     await probe.refresh_action()
     # It can take a couple of cycles for the refresh handler to fully execute;
     # impose a small delay to ensure it's been processed.
-    await probe.redraw("A refresh action has occurred")
+    await probe.redraw("A refresh action has occurred", delay=0.2)
     # New data has been added
     assert len(widget.data) == 101
 
diff --git a/testbed/tests/widgets/test_divider.py b/testbed/tests/widgets/test_divider.py
index bf3dc3c41e..ef9afe4848 100644
--- a/testbed/tests/widgets/test_divider.py
+++ b/testbed/tests/widgets/test_divider.py
@@ -13,7 +13,7 @@
 
 @pytest.fixture
 async def widget():
-    skip_on_platforms("android", "iOS")
+    skip_on_platforms("iOS")
     return toga.Divider()
 
 
diff --git a/testbed/tests/widgets/test_scrollcontainer.py b/testbed/tests/widgets/test_scrollcontainer.py
index 635ee25065..c71ee7e84c 100644
--- a/testbed/tests/widgets/test_scrollcontainer.py
+++ b/testbed/tests/widgets/test_scrollcontainer.py
@@ -85,6 +85,12 @@ async def test_clear_content(widget, probe, small_content):
     await probe.redraw("Widget content has been re-cleared")
     assert not probe.has_content
 
+    # Apply a style to guarantee a set_bounds() call has been made
+    # when there is no content.
+    widget.style.padding = 10
+    await probe.redraw("Widget has definitely been refreshed")
+    assert not probe.has_content
+
     widget.content = small_content
     await probe.redraw("Widget content has been restored")
     assert probe.has_content
@@ -475,16 +481,23 @@ async def test_manual_scroll(widget, probe, content, on_scroll):
 
 async def test_no_content(widget, probe, content):
     "The content of the scroll container can be cleared"
+    original_width = probe.width
+    assert original_width > 100
     widget.content = None
     await probe.redraw("Content of the scroll container has been cleared")
+    assert probe.width == original_width
 
-    # Force a refresh to see the impact of a set_bounds() when there's
+    # Force a resize to see the impact of a set_bounds() when there's
     # no inner content.
-    widget.refresh()
-    await probe.redraw("Scroll container layout has been refreshed")
+    widget.parent.add(other := toga.Box(style=Pack(flex=1)))
+    await probe.redraw("Scroll container size has been reduced")
+    reduced_width = probe.width
+    assert reduced_width == approx(original_width / 2, abs=1)
 
     widget.content = content
     await probe.redraw("Content of the scroll container has been restored")
+    assert probe.width == reduced_width
 
-    widget.refresh()
-    await probe.redraw("Scroll container layout has been refreshed")
+    widget.parent.remove(other)
+    await probe.redraw("Scroll container size has been restored")
+    assert probe.width == original_width
diff --git a/testbed/tests/widgets/test_table.py b/testbed/tests/widgets/test_table.py
index 4aefd802e6..10752e90a5 100644
--- a/testbed/tests/widgets/test_table.py
+++ b/testbed/tests/widgets/test_table.py
@@ -487,7 +487,7 @@ async def test_cell_widget(widget, probe):
         warning_check = contextlib.nullcontext()
     else:
         warning_check = pytest.warns(
-            match=".* does not support the use of widgets in cells"
+            match=r".* does not support the use of widgets in cells"
         )
 
     with warning_check:
@@ -499,6 +499,8 @@ async def test_cell_widget(widget, probe):
         probe.assert_cell_content(0, 0, "A0")
         probe.assert_cell_content(0, 1, "B0")
 
+        await probe.redraw("Table row with a widget has been accessed", delay=0.1)
+
     probe.assert_cell_content(1, 0, "A1")
     probe.assert_cell_content(1, 1, "B1")
 
diff --git a/testbed/tests/widgets/test_textinput.py b/testbed/tests/widgets/test_textinput.py
index 26d97d151b..049d23acb3 100644
--- a/testbed/tests/widgets/test_textinput.py
+++ b/testbed/tests/widgets/test_textinput.py
@@ -160,7 +160,7 @@ async def test_on_confirm(widget, probe):
     await probe.redraw("Typed newline")
 
     # The handler has been invoked
-    assert handler.call_count == 1
+    handler.assert_called_once_with(widget)
 
 
 async def test_validation(widget, probe):
diff --git a/testbed/tests/widgets/test_webview.py b/testbed/tests/widgets/test_webview.py
index 10dcb6dd18..4dc852ed45 100644
--- a/testbed/tests/widgets/test_webview.py
+++ b/testbed/tests/widgets/test_webview.py
@@ -111,7 +111,14 @@ async def widget(on_load):
             else:
                 raise
 
-    return widget
+    yield widget
+
+    if toga.platform.current_platform == "linux":
+        # On Gtk, ensure that the WebView is garbage collection before the next test
+        # case. This prevents a segfault at GC time likely coming from the test suite
+        # running in a thread and Gtk WebViews sharing resources between instances.
+        del widget
+        gc.collect()
 
 
 async def test_set_url(widget, probe, on_load):
diff --git a/toga/setup.cfg b/toga/setup.cfg
index 64ca095ad1..47e639c815 100644
--- a/toga/setup.cfg
+++ b/toga/setup.cfg
@@ -12,7 +12,7 @@ author_email = russell@keith-magee.com
 maintainer = BeeWare Team
 maintainer_email = team@beeware.org
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Intended Audience :: Developers
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
diff --git a/tox.ini b/tox.ini
index 308b6dc1f6..f25cf8f399 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,25 +1,14 @@
-# The leading comma generates the "py-..." environments.
-[testenv:py{,38,39,310,311,312}-{android,cocoa,core,gtk,iOS,web,winforms}]
+# The leading comma generates the "py" environment.
+[testenv:py{,38,39,310,311,312}]
 skip_install = True
 setenv =
-    android: subdir = android
-    cocoa: subdir = cocoa
-    core: subdir = core
-    gtk: subdir = gtk
-    iOS: subdir = iOS
-    web: subdir = web
-    winforms: subdir = winforms
-
-    core: TOGA_BACKEND = toga_dummy
-    !core: TOGA_BACKEND = toga_{env:subdir}
-    gtk: test_command_prefix = xvfb-run -a -s "-screen 0 2048x1536x24"
-changedir = {env:subdir}
+    TOGA_BACKEND = toga_dummy
+changedir = core
 allowlist_externals =
     bash
-    gtk: xvfb-run
 commands =
     # TOGA_INSTALL_COMMAND is set to a bash command by the CI workflow.
-    {env:TOGA_INSTALL_COMMAND:python -m pip install ../core[dev] ../dummy .}
+    {env:TOGA_INSTALL_COMMAND:python -m pip install .[dev] ../dummy}
     {env:test_command_prefix:} coverage run -m pytest -vv {posargs}
     coverage combine
     coverage report --rcfile ../pyproject.toml
diff --git a/web/src/toga_web/app.py b/web/src/toga_web/app.py
index fdb71cba10..4d8090c05d 100644
--- a/web/src/toga_web/app.py
+++ b/web/src/toga_web/app.py
@@ -1,4 +1,5 @@
 import toga
+from toga.command import GROUP_BREAK, SECTION_BREAK
 from toga_web.libs import create_element, js
 from toga_web.window import Window
 
@@ -22,7 +23,7 @@ def create(self):
         self.interface.commands.add(
             # ---- Help menu ----------------------------------
             toga.Command(
-                lambda _: self.interface.about(),
+                self._menu_about,
                 "About " + formal_name,
                 group=toga.Group.HELP,
             ),
@@ -33,7 +34,9 @@ def create(self):
             ),
         )
 
-        # Create the menus.
+        # Create the menus. This is done before main window content to ensure
+        # the <header> for the menubar is inserted before the <main> for the
+        # main window.
         self.create_menus()
 
         # Call user code to populate the main window
@@ -63,9 +66,9 @@ def create_menus(self):
         submenu = None
 
         for cmd in self.interface.commands:
-            if cmd == toga.GROUP_BREAK:
+            if cmd == GROUP_BREAK:
                 submenu = None
-            elif cmd == toga.SECTION_BREAK:
+            elif cmd == SECTION_BREAK:
                 # TODO - add a section break
                 pass
             else:
@@ -78,7 +81,7 @@ def create_menus(self):
                     content=cmd.text,
                     disabled=not cmd.enabled,
                 )
-                menu_item.onclick = cmd.action
+                menu_item.onclick = cmd._impl.dom_click
 
                 submenu.append(menu_item)
 
@@ -102,8 +105,10 @@ def create_menus(self):
             else:
                 help_menu_container.appendChild(submenu)
 
+        menubar_id = f"{self.interface.app_id}-header"
         self.menubar = create_element(
             "header",
+            id=menubar_id,
             classes=["toga"],
             children=[
                 create_element(
@@ -123,8 +128,15 @@ def create_menus(self):
             ],
         )
 
-        # Menubar exists at the app level.
-        self.native.appendChild(self.menubar)
+        # If there's an existing menubar, replace it.
+        old_menubar = js.document.getElementById(menubar_id)
+        if old_menubar:
+            old_menubar.replaceWith(self.menubar)
+        else:
+            self.native.append(self.menubar)
+
+    def _menu_about(self, widget, **kwargs):
+        self.interface.about()
 
     def main_loop(self):
         self.create()
diff --git a/web/src/toga_web/command.py b/web/src/toga_web/command.py
index 43dc630c02..3378a4e760 100644
--- a/web/src/toga_web/command.py
+++ b/web/src/toga_web/command.py
@@ -6,6 +6,9 @@ def __init__(self, interface):
         self.interface = interface
         self.native = []
 
+    def dom_click(self, event):
+        self.interface.action()
+
     def set_enabled(self, value):
         pass
         # enabled = self.interface.enabled
diff --git a/web/src/toga_web/dialogs.py b/web/src/toga_web/dialogs.py
index 0e81878a30..2fba1d7cbe 100644
--- a/web/src/toga_web/dialogs.py
+++ b/web/src/toga_web/dialogs.py
@@ -41,7 +41,7 @@ def dialog_close(self, event):
         self.native.hide()
         self.native.parentElement.removeChild(self.native)
 
-        self.on_result(self, None)
+        self.on_result(None)
         self.interface.future.set_result(None)
 
 
@@ -52,7 +52,7 @@ def __init__(self, interface, title, message, on_result=None):
 
         interface.window.factory.not_implemented("Window.question_dialog()")
 
-        self.on_result(self, None)
+        self.on_result(None)
         self.interface.future.set_result(None)
 
 
@@ -63,7 +63,7 @@ def __init__(self, interface, title, message, on_result=None):
 
         interface.window.factory.not_implemented("Window.confirm_dialog()")
 
-        self.on_result(self, None)
+        self.on_result(None)
         self.interface.future.set_result(None)
 
 
@@ -74,7 +74,7 @@ def __init__(self, interface, title, message, on_result=None):
 
         interface.window.factory.not_implemented("Window.error_dialog()")
 
-        self.on_result(self, None)
+        self.on_result(None)
         self.interface.future.set_result(None)
 
 
@@ -85,7 +85,7 @@ def __init__(self, interface, title, message, on_result=None, **kwargs):
 
         interface.window.factory.not_implemented("Window.stack_trace_dialog()")
 
-        self.on_result(self, None)
+        self.on_result(None)
         self.interface.future.set_result(None)
 
 
@@ -104,7 +104,7 @@ def __init__(
 
         interface.window.factory.not_implemented("Window.save_file_dialog()")
 
-        self.on_result(self, None)
+        self.on_result(None)
         self.interface.future.set_result(None)
 
 
@@ -123,7 +123,7 @@ def __init__(
 
         interface.window.factory.not_implemented("Window.open_file_dialog()")
 
-        self.on_result(self, None)
+        self.on_result(None)
         self.interface.future.set_result(None)
 
 
@@ -141,5 +141,5 @@ def __init__(
 
         interface.window.factory.not_implemented("Window.select_folder_dialog()")
 
-        self.on_result(self, None)
+        self.on_result(None)
         self.interface.future.set_result(None)
diff --git a/web/src/toga_web/widgets/button.py b/web/src/toga_web/widgets/button.py
index 6491076fe3..633c27b318 100644
--- a/web/src/toga_web/widgets/button.py
+++ b/web/src/toga_web/widgets/button.py
@@ -7,7 +7,7 @@ def create(self):
         self.native.onclick = self.dom_onclick
 
     def dom_onclick(self, event):
-        self.interface.on_press(None)
+        self.interface.on_press()
 
     def get_text(self):
         return self.native.innerHTML
diff --git a/web/src/toga_web/widgets/switch.py b/web/src/toga_web/widgets/switch.py
index 748ee24ab5..558f837661 100644
--- a/web/src/toga_web/widgets/switch.py
+++ b/web/src/toga_web/widgets/switch.py
@@ -9,7 +9,7 @@ def create(self):
         self.native.addEventListener("sl-change", create_proxy(self.dom_onchange))
 
     def dom_onchange(self, event):
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_text(self):
         return self.native.innerHTML
@@ -24,4 +24,4 @@ def set_value(self, value):
         old_value = self.get_value()
         self.native.checked = value
         if value != old_value:
-            self.interface.on_change(self.interface)
+            self.interface.on_change()
diff --git a/web/src/toga_web/widgets/textinput.py b/web/src/toga_web/widgets/textinput.py
index 638aa9c612..cd63750cf6 100644
--- a/web/src/toga_web/widgets/textinput.py
+++ b/web/src/toga_web/widgets/textinput.py
@@ -9,7 +9,7 @@ def create(self):
 
     def dom_keyup(self, event):
         if event.key == "Enter":
-            self.interface.on_confirm(None)
+            self.interface.on_confirm()
 
     def set_readonly(self, value):
         self.native.readOnly = value
diff --git a/web/tests/__init__.py b/web/tests/__init__.py
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/web/tests/test_implementation.py b/web/tests/test_implementation.py
deleted file mode 100644
index 51631ff090..0000000000
--- a/web/tests/test_implementation.py
+++ /dev/null
@@ -1,11 +0,0 @@
-import os
-
-from toga_dummy import test_implementation
-
-globals().update(
-    test_implementation.create_impl_tests(
-        os.path.abspath(
-            os.path.join(os.path.dirname(os.path.dirname(__file__)), "src", "toga_web")
-        )
-    )
-)
diff --git a/winforms/setup.cfg b/winforms/setup.cfg
index 56967a1644..e4a72d66fa 100644
--- a/winforms/setup.cfg
+++ b/winforms/setup.cfg
@@ -12,7 +12,7 @@ author_email = russell@keith-magee.com
 maintainer = BeeWare Team
 maintainer_email = team@beeware.org
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Intended Audience :: Developers
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
diff --git a/winforms/src/toga_winforms/app.py b/winforms/src/toga_winforms/app.py
index a94c9a7b94..9bca588af9 100644
--- a/winforms/src/toga_winforms/app.py
+++ b/winforms/src/toga_winforms/app.py
@@ -6,12 +6,14 @@
 
 import System.Windows.Forms as WinForms
 from System import Environment, Threading
+from System.ComponentModel import InvalidEnumArgumentException
 from System.Media import SystemSounds
 from System.Net import SecurityProtocolType, ServicePointManager
 from System.Windows.Threading import Dispatcher
 
 import toga
 from toga import Key
+from toga.command import GROUP_BREAK, SECTION_BREAK
 
 from .keys import toga_to_winforms_key
 from .libs.proactor import WinformsProactorEventLoop
@@ -23,13 +25,12 @@ class MainWindow(Window):
     def winforms_FormClosing(self, sender, event):
         # Differentiate between the handling that occurs when the user
         # requests the app to exit, and the actual application exiting.
-        if not self.interface.app._impl._is_exiting:
+        if not self.interface.app._impl._is_exiting:  # pragma: no branch
             # If there's an event handler, process it. The decision to
             # actually exit the app will be processed in the on_exit handler.
             # If there's no exit handler, assume the close/exit can proceed.
-            if self.interface.app.on_exit:
-                self.interface.app.on_exit(self.interface.app)
-                event.Cancel = True
+            self.interface.app.on_exit()
+            event.Cancel = True
 
 
 class App:
@@ -71,7 +72,7 @@ def create(self):
             # SetProcessDpiAwareness(True)
             if (win_version.Major == 6 and win_version.Minor == 3) or (
                 win_version.Major == 10 and win_version.Build < 15063
-            ):
+            ):  # pragma: no cover
                 windll.shcore.SetProcessDpiAwareness(True)
                 print(
                     "WARNING: Your Windows version doesn't support DPI-independent rendering.  "
@@ -82,7 +83,7 @@ def create(self):
             elif win_version.Major == 10 and win_version.Build >= 15063:
                 windll.user32.SetProcessDpiAwarenessContext(-2)
             # Any other version of windows should use SetProcessDPIAware()
-            else:
+            else:  # pragma: no cover
                 windll.user32.SetProcessDPIAware()
 
         self.native.EnableVisualStyles()
@@ -95,84 +96,74 @@ def create(self):
         # encouraged.
         try:
             ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls12
-        except AttributeError:
+        except AttributeError:  # pragma: no cover
             print(
                 "WARNING: Your Windows .NET install does not support TLS1.2. "
                 "You may experience difficulties accessing some web server content."
             )
         try:
             ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls13
-        except AttributeError:
+        except AttributeError:  # pragma: no cover
             print(
                 "WARNING: Your Windows .NET install does not support TLS1.3. "
                 "You may experience difficulties accessing some web server content."
             )
 
-        self.interface.commands.add(
-            toga.Command(
-                lambda _: self.interface.about(),
-                f"About {self.interface.name}",
-                group=toga.Group.HELP,
-            ),
-            toga.Command(None, "Preferences", group=toga.Group.FILE),
-            # Quit should always be the last item, in a section on its own
-            toga.Command(
-                lambda _: self.interface.exit(),
-                "Exit " + self.interface.name,
-                shortcut=Key.MOD_1 + "q",
-                group=toga.Group.FILE,
-                section=sys.maxsize,
-            ),
-            toga.Command(
-                lambda _: self.interface.visit_homepage(),
-                "Visit homepage",
-                enabled=self.interface.home_page is not None,
-                group=toga.Group.HELP,
-            ),
-        )
-        self._create_app_commands()
-
         # Call user code to populate the main window
         self.interface._startup()
+        self._create_app_commands()
         self.create_menus()
         self.interface.main_window._impl.set_app(self)
 
     def create_menus(self):
-        self._menu_items = {}
+        if self.interface.main_window is None:  # pragma: no branch
+            # The startup method may create commands before creating the window, so
+            # we'll call create_menus again after it returns.
+            return
+
+        window = self.interface.main_window._impl
+        menubar = window.native.MainMenuStrip
+        if menubar:
+            menubar.Items.Clear()
+        else:
+            # The menu bar doesn't need to be positioned, because its `Dock` property
+            # defaults to `Top`.
+            menubar = WinForms.MenuStrip()
+            window.native.Controls.Add(menubar)
+            window.native.MainMenuStrip = menubar
+            menubar.SendToBack()  # In a dock, "back" means "top".
+
+        # The File menu should come before all user-created menus.
         self._menu_groups = {}
+        toga.Group.FILE.order = -1
 
-        toga.Group.FILE.order = 0
-        menubar = WinForms.MenuStrip()
         submenu = None
         for cmd in self.interface.commands:
-            if cmd == toga.GROUP_BREAK:
+            if cmd == GROUP_BREAK:
                 submenu = None
-            elif cmd == toga.SECTION_BREAK:
+            elif cmd == SECTION_BREAK:
                 submenu.DropDownItems.Add("-")
             else:
                 submenu = self._submenu(cmd.group, menubar)
-
                 item = WinForms.ToolStripMenuItem(cmd.text)
+                item.Click += WeakrefCallable(cmd._impl.winforms_Click)
+                if cmd.shortcut is not None:
+                    try:
+                        item.ShortcutKeys = toga_to_winforms_key(cmd.shortcut)
+                    except (
+                        ValueError,
+                        InvalidEnumArgumentException,
+                    ) as e:  # pragma: no cover
+                        # Make this a non-fatal warning, because different backends may
+                        # accept different shortcuts.
+                        print(f"WARNING: invalid shortcut {cmd.shortcut!r}: {e}")
 
-                if cmd.action:
-                    item.Click += WeakrefCallable(cmd._impl.winforms_handler)
                 item.Enabled = cmd.enabled
 
-                if cmd.shortcut is not None:
-                    shortcut_keys = toga_to_winforms_key(cmd.shortcut)
-                    item.ShortcutKeys = shortcut_keys
-                    item.ShowShortcutKeys = True
-
                 cmd._impl.native.append(item)
-
-                self._menu_items[item] = cmd
                 submenu.DropDownItems.Add(item)
 
-        # The menu bar doesn't need to be positioned, because its `Dock` property
-        # defaults to `Top`.
-        self.interface.main_window._impl.native.Controls.Add(menubar)
-        self.interface.main_window._impl.native.MainMenuStrip = menubar
-        self.interface.main_window._impl.resize_content()
+        window.resize_content()
 
     def _submenu(self, group, menubar):
         try:
@@ -195,16 +186,36 @@ def _submenu(self, group, menubar):
         return submenu
 
     def _create_app_commands(self):
-        # No extra menus
-        pass
-
-    def open_document(self, fileURL):
-        """Add a new document to this app."""
-        print(
-            "STUB: If you want to handle opening documents, implement App.open_document(fileURL)"
+        self.interface.commands.add(
+            # About should be the last item in the Help menu, in a section on its own.
+            toga.Command(
+                lambda _: self.interface.about(),
+                f"About {self.interface.formal_name}",
+                group=toga.Group.HELP,
+                section=sys.maxsize,
+            ),
+            #
+            toga.Command(None, "Preferences", group=toga.Group.FILE),
+            #
+            # On Windows, the Exit command doesn't usually contain the app name. It
+            # should be the last item in the File menu, in a section on its own.
+            toga.Command(
+                lambda _: self.interface.on_exit(),
+                "Exit",
+                shortcut=Key.MOD_1 + "q",
+                group=toga.Group.FILE,
+                section=sys.maxsize,
+            ),
+            #
+            toga.Command(
+                lambda _: self.interface.visit_homepage(),
+                "Visit homepage",
+                enabled=self.interface.home_page is not None,
+                group=toga.Group.HELP,
+            ),
         )
 
-    def winforms_thread_exception(self, sender, winforms_exc):
+    def winforms_thread_exception(self, sender, winforms_exc):  # pragma: no cover
         # The PythonException returned by Winforms doesn't give us
         # easy access to the underlying Python stacktrace; so we
         # reconstruct it from the string message.
@@ -231,13 +242,13 @@ def winforms_thread_exception(self, sender, winforms_exc):
         print(py_exc.Message)
 
     @classmethod
-    def print_stack_trace(cls, stack_trace_line):
+    def print_stack_trace(cls, stack_trace_line):  # pragma: no cover
         for level in stack_trace_line.split("', '"):
             for line in level.split("\\n"):
                 if line:
                     print(line)
 
-    def run_app(self):
+    def run_app(self):  # pragma: no cover
         # Enable coverage tracing on this non-Python-created thread
         # (https://github.com/nedbat/coveragepy/issues/686).
         if threading._trace_hook:
@@ -270,36 +281,30 @@ def main_loop(self):
         # If it's non-None, raise it, as it indicates the underlying
         # app thread had a problem; this is effectibely a re-raise over
         # a thread boundary.
-        if self._exception:
+        if self._exception:  # pragma: no cover
             raise self._exception
 
     def show_about_dialog(self):
         message_parts = []
-        if self.interface.name is not None:
-            if self.interface.version is not None:
-                message_parts.append(
-                    "{name} v{version}".format(
-                        name=self.interface.name,
-                        version=self.interface.version,
-                    )
-                )
-            else:
-                message_parts.append(f"{self.interface.name}")
-        elif self.interface.version is not None:
-            message_parts.append(f"v{self.interface.version}")
+        if self.interface.version is not None:
+            message_parts.append(
+                f"{self.interface.formal_name} v{self.interface.version}"
+            )
+        else:
+            message_parts.append(self.interface.formal_name)
 
         if self.interface.author is not None:
             message_parts.append(f"Author: {self.interface.author}")
         if self.interface.description is not None:
             message_parts.append(f"\n{self.interface.description}")
         self.interface.main_window.info_dialog(
-            f"About {self.interface.name}", "\n".join(message_parts)
+            f"About {self.interface.formal_name}", "\n".join(message_parts)
         )
 
     def beep(self):
         SystemSounds.Beep.Play()
 
-    def exit(self):
+    def exit(self):  # pragma: no cover
         self._is_exiting = True
         self.native.Exit()
 
@@ -309,7 +314,8 @@ def set_main_window(self, window):
     def get_current_window(self):
         for window in self.interface.windows:
             if WinForms.Form.ActiveForm == window._impl.native:
-                return window._impl.native
+                return window._impl
+        return None
 
     def set_current_window(self, window):
         window._impl.native.Activate()
@@ -333,8 +339,9 @@ def hide_cursor(self):
         self._cursor_visible = False
 
 
-class DocumentApp(App):
+class DocumentApp(App):  # pragma: no cover
     def _create_app_commands(self):
+        super()._create_app_commands()
         self.interface.commands.add(
             toga.Command(
                 lambda w: self.open_file,
@@ -344,11 +351,3 @@ def _create_app_commands(self):
                 section=0,
             ),
         )
-
-    def open_document(self, fileURL):
-        """Open a new document in this app.
-
-        Args:
-            fileURL (str): The URL/path to the file to add as a document.
-        """
-        self.interface.factory.not_implemented("DocumentApp.open_document()")
diff --git a/winforms/src/toga_winforms/colors.py b/winforms/src/toga_winforms/colors.py
index 8609bbebf2..4a7b89d08f 100644
--- a/winforms/src/toga_winforms/colors.py
+++ b/winforms/src/toga_winforms/colors.py
@@ -1,5 +1,5 @@
 from System.Drawing import Color
-from travertino.colors import NAMED_COLOR, TRANSPARENT
+from travertino.colors import TRANSPARENT
 
 CACHE = {TRANSPARENT: Color.Transparent}
 
@@ -8,8 +8,6 @@ def native_color(c):
     try:
         color = CACHE[c]
     except KeyError:
-        if isinstance(c, str):
-            c = NAMED_COLOR[c]
         color = Color.FromArgb(
             int(c.rgba.a * 255), int(c.rgba.r), int(c.rgba.g), int(c.rgba.b)
         )
diff --git a/winforms/src/toga_winforms/command.py b/winforms/src/toga_winforms/command.py
index c06c9f87d9..562eb7fb2e 100644
--- a/winforms/src/toga_winforms/command.py
+++ b/winforms/src/toga_winforms/command.py
@@ -3,10 +3,10 @@ def __init__(self, interface):
         self.interface = interface
         self.native = []
 
+    def winforms_Click(self, sender, event):
+        return self.interface.action()
+
     def set_enabled(self, value):
         if self.native:
             for widget in self.native:
                 widget.Enabled = self.interface.enabled
-
-    def winforms_handler(self, sender, event):
-        return self.interface.action(None)
diff --git a/winforms/src/toga_winforms/container.py b/winforms/src/toga_winforms/container.py
index 061ef38d83..dcddf391f6 100644
--- a/winforms/src/toga_winforms/container.py
+++ b/winforms/src/toga_winforms/container.py
@@ -52,7 +52,7 @@ def apply_layout(self, layout_width, layout_height):
         )
 
     def add_content(self, widget):
-        # The default appears to be to add new controls to the back of the Z-order.
+        # The default is to add new controls to the back of the Z-order.
         self.native_content.Controls.Add(widget.native)
         widget.native.BringToFront()
 
diff --git a/winforms/src/toga_winforms/dialogs.py b/winforms/src/toga_winforms/dialogs.py
index 5b82d9e5ca..5e57104e66 100644
--- a/winforms/src/toga_winforms/dialogs.py
+++ b/winforms/src/toga_winforms/dialogs.py
@@ -26,7 +26,7 @@ def start_inner_loop(self, callback, *args):
         asyncio.get_event_loop().start_inner_loop(callback, *args)
 
     def set_result(self, result):
-        self.on_result(None, result)
+        self.on_result(result)
         self.interface.future.set_result(result)
 
 
diff --git a/winforms/src/toga_winforms/images.py b/winforms/src/toga_winforms/images.py
index 359c760715..9417fc56e1 100644
--- a/winforms/src/toga_winforms/images.py
+++ b/winforms/src/toga_winforms/images.py
@@ -33,6 +33,11 @@ def get_width(self):
     def get_height(self):
         return self.native.Height
 
+    def get_data(self):
+        stream = MemoryStream()
+        self.native.Save(stream, ImageFormat.Png)
+        return stream.ToArray()
+
     def save(self, path):
         path = Path(path)
         try:
diff --git a/winforms/src/toga_winforms/keys.py b/winforms/src/toga_winforms/keys.py
index 5fabd663f0..33208d0657 100644
--- a/winforms/src/toga_winforms/keys.py
+++ b/winforms/src/toga_winforms/keys.py
@@ -1,72 +1,87 @@
 import operator
+import re
 from functools import reduce
-from string import ascii_uppercase
+from string import ascii_lowercase
 
 import System.Windows.Forms as WinForms
 
 from toga.keys import Key
 
-WINFORMS_NON_PRINTABLES_MAP = {
+WINFORMS_MODIFIERS = {
     Key.MOD_1: WinForms.Keys.Control,
     Key.MOD_2: WinForms.Keys.Alt,
+    Key.SHIFT: WinForms.Keys.Shift,
 }
-WINFORMS_NON_PRINTABLES_MAP.update(
-    {
-        getattr(Key, modifier.upper()): getattr(WinForms.Keys, modifier.title())
-        for modifier in ["shift", "up", "down", "left", "right", "home"]
-    }
-)
 
-WINFORMS_KEYS_MAP = {
-    Key.PLUS.value: WinForms.Keys.Oemplus,
-    Key.MINUS.value: WinForms.Keys.OemMinus,
+WINFORMS_KEYS = {
+    "+": WinForms.Keys.Oemplus,
+    "-": WinForms.Keys.OemMinus,
 }
-WINFORMS_KEYS_MAP.update(
-    {
-        getattr(Key, letter).value: getattr(WinForms.Keys, letter)
-        for letter in ascii_uppercase
-    }
+WINFORMS_KEYS.update(
+    {str(digit): getattr(WinForms.Keys, f"D{digit}") for digit in range(10)}
+)
+
+SHIFTED_KEYS = {symbol: number for symbol, number in zip("!@#$%^&*()", "1234567890")}
+SHIFTED_KEYS.update(
+    {lower.upper(): lower for lower in ascii_lowercase},
 )
 
 
 def toga_to_winforms_key(key):
+    # Convert a Key object into string form.
+    try:
+        key = key.value
+    except AttributeError:
+        pass
+
     codes = []
-    for modifier, modifier_code in WINFORMS_NON_PRINTABLES_MAP.items():
+    for modifier, modifier_code in WINFORMS_MODIFIERS.items():
         if modifier.value in key:
             codes.append(modifier_code)
             key = key.replace(modifier.value, "")
-    key_code = WINFORMS_KEYS_MAP.get(key, None)
-    if key_code is not None:
-        codes.append(key_code)
-    return reduce(operator.or_, codes)
-
-
-TOGA_KEYS_MAP = {w: t for t, w in WINFORMS_KEYS_MAP.items()}
-TOGA_KEYS_MAP.update(
-    {
-        getattr(WinForms.Keys, modifier.title()): getattr(Key, modifier.upper())
-        for modifier in ["shift", "up", "down", "left", "right", "home"]
-    }
-)
 
+    if lower := SHIFTED_KEYS.get(key):
+        key = lower
+        codes.append(WinForms.Keys.Shift)
 
-def toga_key(event):
-    """Convert a Cocoa NSKeyEvent into a Toga event."""
     try:
-        key = TOGA_KEYS_MAP[event.KeyCode]
+        codes.append(WINFORMS_KEYS[key])
     except KeyError:
-        key = WINFORMS_NON_PRINTABLES_MAP
+        if match := re.fullmatch(r"<(.+)>", key):
+            key = match[1]
+        try:
+            codes.append(getattr(WinForms.Keys, key.title()))
+        except AttributeError:  # pragma: no cover
+            raise ValueError(f"unknown key: {key!r}") from None
+
+    return reduce(operator.or_, codes)
+
+
+def winforms_to_toga_key(code):
     modifiers = set()
 
-    # if event.Capslock?:
-    #     modifiers.add(Key.CAPSLOCK)
-    if event.Shift:
-        modifiers.add(Key.SHIFT)
-    if event.Control:
-        modifiers.add(Key.MOD_1)
-    if event.Alt:
-        modifiers.add(Key.MOD_2)
-    # if event.Windows?:
-    # modifiers.add(Key.MOD_3)
-
-    return {"key": key, "modifiers": modifiers}
+    code_names = str(code).split(", ")
+    for toga_mod, code in WINFORMS_MODIFIERS.items():
+        try:
+            code_names.remove(str(code))
+        except ValueError:
+            pass
+        else:
+            modifiers.add(toga_mod)
+
+    assert len(code_names) == 1
+    for toga_value, code in WINFORMS_KEYS.items():
+        if str(code) == code_names[0]:
+            break
+    else:
+        toga_value = code_names[0].lower()
+        if len(toga_value) > 1:
+            toga_value = f"<{toga_value}>"
+
+    if (Key.SHIFT in modifiers) and (toga_value not in ascii_lowercase):
+        for symbol, number in SHIFTED_KEYS.items():
+            if toga_value == number:
+                toga_value = symbol
+                modifiers.remove(Key.SHIFT)
+
+    return {"key": Key(toga_value), "modifiers": modifiers}
diff --git a/winforms/src/toga_winforms/libs/proactor.py b/winforms/src/toga_winforms/libs/proactor.py
index 1aa868baca..4cf3a25176 100644
--- a/winforms/src/toga_winforms/libs/proactor.py
+++ b/winforms/src/toga_winforms/libs/proactor.py
@@ -38,9 +38,9 @@ def run_forever(self, app):
         # in Lib/ascynio/base_events.py)
         # === START BaseEventLoop.run_forever() setup ===
         self._check_closed()
-        if self.is_running():
+        if self.is_running():  # pragma: no cover
             raise RuntimeError("This event loop is already running")
-        if events._get_running_loop() is not None:
+        if events._get_running_loop() is not None:  # pragma: no cover
             raise RuntimeError(
                 "Cannot run the event loop while another loop is running"
             )
@@ -71,13 +71,17 @@ def run_forever(self, app):
 
     def enqueue_tick(self):
         # Queue a call to tick in 5ms.
-        if not self.app._is_exiting:
+        if not self.app._is_exiting:  # pragma: no branch
             self.task = Action[Task](self.tick)
             Task.Delay(5).ContinueWith(self.task)
 
     def tick(self, *args, **kwargs):
         """Cause a single iteration of the event loop to run on the main GUI thread."""
-        if not self.app._is_exiting:
+
+        # This function doesn't report as covered, probably because it runs on a
+        # non-Python-created thread (see App.run_app). But it must actually be covered,
+        # otherwise nothing would work.
+        if not self.app._is_exiting:  # pragma: no cover
             action = Action(self.run_once_recurring)
             self.app.app_dispatcher.Invoke(action)
 
@@ -99,7 +103,7 @@ def run_once_recurring(self):
             # Perform one tick of the event loop.
             self._run_once()
 
-            if self._stopping:
+            if self._stopping:  # pragma: no cover
                 # If we're stopping, we can do the "finally" handling from
                 # the BaseEventLoop run_forever().
                 # === START BaseEventLoop.run_forever() finally handling ===
@@ -123,5 +127,5 @@ def run_once_recurring(self):
                     callback(*args)
 
         # Exceptions thrown by this method will be silently ignored.
-        except BaseException:
+        except BaseException:  # pragma: no cover
             traceback.print_exc()
diff --git a/winforms/src/toga_winforms/libs/wrapper.py b/winforms/src/toga_winforms/libs/wrapper.py
index 958db4cc66..4ad877d3a4 100644
--- a/winforms/src/toga_winforms/libs/wrapper.py
+++ b/winforms/src/toga_winforms/libs/wrapper.py
@@ -13,10 +13,10 @@ class WeakrefCallable:
     def __init__(self, function):
         try:
             self.ref = weakref.WeakMethod(function)
-        except TypeError:
+        except TypeError:  # pragma: no cover
             self.ref = weakref.ref(function)
 
     def __call__(self, *args, **kwargs):
         function = self.ref()
-        if function:
+        if function:  # pragma: no branch
             return function(*args, **kwargs)
diff --git a/winforms/src/toga_winforms/widgets/base.py b/winforms/src/toga_winforms/widgets/base.py
index b4c8068aae..c966dfd219 100644
--- a/winforms/src/toga_winforms/widgets/base.py
+++ b/winforms/src/toga_winforms/widgets/base.py
@@ -1,5 +1,5 @@
 from abc import ABC, abstractmethod
-from decimal import ROUND_HALF_EVEN, ROUND_UP, Decimal
+from decimal import ROUND_HALF_EVEN, Decimal
 
 from System.Drawing import (
     Color,
@@ -144,15 +144,10 @@ def remove_child(self, child):
         child.container = None
 
     def refresh(self):
-        intrinsic = self.interface.intrinsic
-        intrinsic.width = intrinsic.height = None
+        # Default values; may be overwritten by rehint().
+        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
+        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
         self.rehint()
-        assert intrinsic.width is not None
-        assert intrinsic.height is not None
 
-        intrinsic.width = self.scale_out(intrinsic.width, ROUND_UP)
-        intrinsic.height = self.scale_out(intrinsic.height, ROUND_UP)
-
-    @abstractmethod
     def rehint(self):
-        ...
+        pass
diff --git a/winforms/src/toga_winforms/widgets/box.py b/winforms/src/toga_winforms/widgets/box.py
index 6025c443a8..44321cfdc7 100644
--- a/winforms/src/toga_winforms/widgets/box.py
+++ b/winforms/src/toga_winforms/widgets/box.py
@@ -1,5 +1,4 @@
 import System.Windows.Forms as WinForms
-from travertino.size import at_least
 
 from .base import Widget
 
@@ -7,7 +6,3 @@
 class Box(Widget):
     def create(self):
         self.native = WinForms.Panel()
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(0)
-        self.interface.intrinsic.height = at_least(0)
diff --git a/winforms/src/toga_winforms/widgets/button.py b/winforms/src/toga_winforms/widgets/button.py
index 372a2c06b5..c1c59ae416 100644
--- a/winforms/src/toga_winforms/widgets/button.py
+++ b/winforms/src/toga_winforms/widgets/button.py
@@ -1,3 +1,5 @@
+from decimal import ROUND_UP
+
 import System.Windows.Forms as WinForms
 from travertino.size import at_least
 
@@ -14,7 +16,7 @@ def create(self):
         self.native.Click += WeakrefCallable(self.winforms_click)
 
     def winforms_click(self, sender, event):
-        self.interface.on_press(None)
+        self.interface.on_press()
 
     def get_text(self):
         value = self.native.Text
@@ -31,7 +33,9 @@ def set_text(self, text):
         self.native.Text = text
 
     def rehint(self):
-        # self.native.Size = Size(0, 0)
-        # print("REHINT Button", self, self.native.PreferredSize)
-        self.interface.intrinsic.width = at_least(self.native.PreferredSize.Width)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.width = self.scale_out(
+            at_least(self.native.PreferredSize.Width), ROUND_UP
+        )
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
diff --git a/winforms/src/toga_winforms/widgets/canvas.py b/winforms/src/toga_winforms/widgets/canvas.py
index 1d8d6ba8ab..3f4576655e 100644
--- a/winforms/src/toga_winforms/widgets/canvas.py
+++ b/winforms/src/toga_winforms/widgets/canvas.py
@@ -1,6 +1,7 @@
-from math import degrees, pi
+from math import degrees
 
 import System.Windows.Forms as WinForms
+from System import Array
 from System.Drawing import (
     Bitmap,
     Graphics,
@@ -21,7 +22,7 @@
 from System.Drawing.Imaging import ImageFormat
 from System.IO import MemoryStream
 
-from toga.widgets.canvas import Baseline, FillRule
+from toga.widgets.canvas import Baseline, FillRule, arc_to_bezier, sweepangle
 from toga_winforms.colors import native_color
 
 from ..libs.wrapper import WeakrefCallable
@@ -37,35 +38,39 @@ def __init__(self):
 
     def clear_paths(self):
         self.paths = []
-        self.start_point = None
-        self.at_start_point = False
+        self.add_path()
 
     @property
     def current_path(self):
-        if len(self.paths) == 0:
-            self.add_path()
         return self.paths[-1]
 
-    def add_path(self):
+    def add_path(self, start_point=None):
         self.paths.append(GraphicsPath())
+        self.start_point = start_point
 
     # Because the GraphicsPath API works in terms of segments rather than points, it has
-    # nowhere to save the starting point of each figure before we use it. In all other
+    # no equivalent to move_to, and we must save that point manually. In all other
     # situations, we can get the last point from the GraphicsPath itself.
     #
     # default_x and default_y should be set as described in the HTML spec under "ensure
     # there is a subpath".
     def get_last_point(self, default_x, default_y):
-        if self.at_start_point:
-            self.at_start_point = False
-            return self.start_point
-        elif self.current_path.PointCount:
+        if self.current_path.PointCount:
             return self.current_path.GetLastPoint()
-        else:
-            # Since we're returning start_point for immediate use, we don't set
-            # at_start_point here.
-            self.start_point = PointF(default_x, default_y)
+        elif self.start_point:
             return self.start_point
+        else:
+            return PointF(default_x, default_y)
+
+    def print_path(self, path=None):  # pragma: no cover
+        if path is None:
+            path = self.current_path
+        print(
+            "\n".join(
+                str((ptype, point.X, point.Y))
+                for ptype, point in zip(path.PathTypes, path.PathPoints)
+            )
+        )
 
 
 class Canvas(Box):
@@ -94,7 +99,6 @@ def winforms_paint(self, panel, event, *args):
 
     def winforms_resize(self, *args):
         self.interface.on_resize(
-            None,
             width=self.scale_out(self.native.Width),
             height=self.scale_out(self.native.Height),
         )
@@ -103,12 +107,12 @@ def winforms_mouse_down(self, obj, mouse_event):
         x, y = map(self.scale_out, (mouse_event.X, mouse_event.Y))
         if mouse_event.Button == WinForms.MouseButtons.Left:
             if mouse_event.Clicks == 2:
-                self.interface.on_activate(None, x, y)
+                self.interface.on_activate(x, y)
             else:
-                self.interface.on_press(None, x, y)
+                self.interface.on_press(x, y)
                 self.dragging = True
         elif mouse_event.Button == WinForms.MouseButtons.Right:
-            self.interface.on_alt_press(None, x, y)
+            self.interface.on_alt_press(x, y)
             self.dragging = True
         else:  # pragma: no cover
             pass
@@ -118,9 +122,9 @@ def winforms_mouse_move(self, obj, mouse_event):
             return
         x, y = map(self.scale_out, (mouse_event.X, mouse_event.Y))
         if mouse_event.Button == WinForms.MouseButtons.Left:
-            self.interface.on_drag(None, x, y)
+            self.interface.on_drag(x, y)
         elif mouse_event.Button == WinForms.MouseButtons.Right:
-            self.interface.on_alt_drag(None, x, y)
+            self.interface.on_alt_drag(x, y)
         else:  # pragma: no cover
             pass
 
@@ -128,9 +132,9 @@ def winforms_mouse_up(self, obj, mouse_event):
         self.dragging = False
         x, y = map(self.scale_out, (mouse_event.X, mouse_event.Y))
         if mouse_event.Button == WinForms.MouseButtons.Left:
-            self.interface.on_release(None, x, y)
+            self.interface.on_release(x, y)
         elif mouse_event.Button == WinForms.MouseButtons.Right:
-            self.interface.on_alt_release(None, x, y)
+            self.interface.on_alt_release(x, y)
         else:  # pragma: no cover
             pass
 
@@ -154,17 +158,15 @@ def begin_path(self, draw_context, **kwargs):
     # We don't use current_path.CloseFigure, because that causes the dash pattern to
     # start on the last segment of the path rather than the first one.
     def close_path(self, draw_context, **kwargs):
-        start = draw_context.start_point
-        if start:
+        if draw_context.current_path.PointCount:
+            start = draw_context.current_path.PathPoints[0]
             draw_context.current_path.AddLine(
-                draw_context.get_last_point(start.X, start.Y), start
+                draw_context.current_path.GetLastPoint(), start
             )
             self.move_to(start.X, start.Y, draw_context)
 
     def move_to(self, x, y, draw_context, **kwargs):
-        draw_context.current_path.StartFigure()
-        draw_context.start_point = PointF(x, y)
-        draw_context.at_start_point = True
+        draw_context.add_path(PointF(x, y))
 
     def line_to(self, x, y, draw_context, **kwargs):
         draw_context.current_path.AddLine(
@@ -203,16 +205,18 @@ def quadratic_curve_to(self, cpx, cpy, x, y, draw_context, **kwargs):
     def arc(
         self, x, y, radius, startangle, endangle, anticlockwise, draw_context, **kwargs
     ):
-        sweepangle = endangle - startangle
-        if anticlockwise:
-            if sweepangle > 0:
-                sweepangle -= 2 * pi
-        else:
-            if sweepangle < 0:
-                sweepangle += 2 * pi
-
-        rect = RectangleF(x - radius, y - radius, 2 * radius, 2 * radius)
-        draw_context.current_path.AddArc(rect, degrees(startangle), degrees(sweepangle))
+        self.ellipse(
+            x,
+            y,
+            radius,
+            radius,
+            0,
+            startangle,
+            endangle,
+            anticlockwise,
+            draw_context,
+            **kwargs,
+        )
 
     def ellipse(
         self,
@@ -227,33 +231,32 @@ def ellipse(
         draw_context,
         **kwargs,
     ):
-        # Transformations apply not to individual points, but to entire GraphicsPath
-        # objects, so we must create a separate one for this shape.
-        draw_context.add_path()
-
-        # The current transform will be applied when the path is filled or stroked, so
-        # make sure we don't apply it now.
-        self.push_context(draw_context)
-        draw_context.matrix.Reset()
-
-        self.translate(x, y, draw_context)
-        self.rotate(rotation, draw_context)
-        if radiusx >= radiusy:
-            self.scale(1, radiusy / radiusx, draw_context)
-            self.arc(0, 0, radiusx, startangle, endangle, anticlockwise, draw_context)
-        else:
-            self.scale(radiusx / radiusy, 1, draw_context)
-            self.arc(0, 0, radiusy, startangle, endangle, anticlockwise, draw_context)
-
-        draw_context.current_path.Transform(draw_context.matrix)
+        matrix = Matrix()
+        matrix.Translate(x, y)
+        matrix.Rotate(degrees(rotation))
+        matrix.Scale(radiusx, radiusy)
+        matrix.Rotate(degrees(startangle))
+
+        points = Array[PointF](
+            [
+                PointF(x, y)
+                for x, y in arc_to_bezier(
+                    sweepangle(startangle, endangle, anticlockwise)
+                )
+            ]
+        )
+        matrix.TransformPoints(points)
 
-        # Set up a fresh GraphicsPath for the next operation.
-        self.pop_context(draw_context)
-        draw_context.add_path()
+        start = draw_context.start_point
+        if start and not draw_context.current_path.PointCount:
+            draw_context.current_path.AddLine(start, start)
+        draw_context.current_path.AddBeziers(points)
 
     def rect(self, x, y, width, height, draw_context, **kwargs):
+        draw_context.add_path()
         rect = RectangleF(x, y, width, height)
         draw_context.current_path.AddRectangle(rect)
+        draw_context.add_path()
 
     # Drawing Paths
 
@@ -266,7 +269,7 @@ def fill(self, color, fill_rule, draw_context, **kwargs):
                 path.FillMode = FillMode.Winding
             path.Transform(draw_context.matrix)
             draw_context.graphics.FillPath(brush, path)
-        draw_context.paths.clear()
+        draw_context.clear_paths()
 
     def stroke(self, color, line_width, line_dash, draw_context, **kwargs):
         pen = Pen(native_color(color), self.scale_in(line_width, rounding=None))
@@ -276,7 +279,7 @@ def stroke(self, color, line_width, line_dash, draw_context, **kwargs):
         for path in draw_context.paths:
             path.Transform(draw_context.matrix)
             draw_context.graphics.DrawPath(pen, path)
-        draw_context.paths.clear()
+        draw_context.clear_paths()
 
     # Transformations
 
diff --git a/winforms/src/toga_winforms/widgets/dateinput.py b/winforms/src/toga_winforms/widgets/dateinput.py
index adb5077d00..4567889ea2 100644
--- a/winforms/src/toga_winforms/widgets/dateinput.py
+++ b/winforms/src/toga_winforms/widgets/dateinput.py
@@ -1,8 +1,8 @@
 import datetime
+from decimal import ROUND_UP
 
 import System.Windows.Forms as WinForms
 from System import DateTime as WinDateTime
-from travertino.size import at_least
 
 from ..libs.wrapper import WeakrefCallable
 from .base import Widget
@@ -42,8 +42,9 @@ def set_max_date(self, value):
         self.native.MaxDate = native_date(value)
 
     def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
 
     def winforms_value_changed(self, sender, event):
-        self.interface.on_change(self.interface)
+        self.interface.on_change()
diff --git a/winforms/src/toga_winforms/widgets/divider.py b/winforms/src/toga_winforms/widgets/divider.py
index 0fa666c9aa..86379a121a 100644
--- a/winforms/src/toga_winforms/widgets/divider.py
+++ b/winforms/src/toga_winforms/widgets/divider.py
@@ -1,3 +1,5 @@
+from decimal import ROUND_UP
+
 import System.Windows.Forms as WinForms
 from travertino.size import at_least
 
@@ -26,8 +28,14 @@ def set_direction(self, value):
 
     def rehint(self):
         if self.get_direction() == self.interface.HORIZONTAL:
-            self.interface.intrinsic.width = at_least(self.native.Width)
-            self.interface.intrinsic.height = self.native.Height
+            self.interface.intrinsic.width = self.scale_out(
+                at_least(self.native.Width), ROUND_UP
+            )
+            self.interface.intrinsic.height = self.scale_out(
+                self.native.Height, ROUND_UP
+            )
         else:
-            self.interface.intrinsic.width = self.native.Width
-            self.interface.intrinsic.height = at_least(self.native.Height)
+            self.interface.intrinsic.width = self.scale_out(self.native.Width, ROUND_UP)
+            self.interface.intrinsic.height = self.scale_out(
+                at_least(self.native.Height), ROUND_UP
+            )
diff --git a/winforms/src/toga_winforms/widgets/imageview.py b/winforms/src/toga_winforms/widgets/imageview.py
index 4795c1daf4..99b11f688d 100644
--- a/winforms/src/toga_winforms/widgets/imageview.py
+++ b/winforms/src/toga_winforms/widgets/imageview.py
@@ -1,3 +1,5 @@
+from decimal import ROUND_UP
+
 import System.Windows.Forms as WinForms
 from System.Drawing import Bitmap
 
@@ -32,8 +34,8 @@ def rehint(self):
         width, height, aspect_ratio = rehint_imageview(
             self.interface.image, self.interface.style, self.dpi_scale
         )
-        self.interface.intrinsic.width = width
-        self.interface.intrinsic.height = height
+        self.interface.intrinsic.width = self.scale_out(width, ROUND_UP)
+        self.interface.intrinsic.height = self.scale_out(height, ROUND_UP)
         if aspect_ratio is not None:
             self.native.SizeMode = WinForms.PictureBoxSizeMode.Zoom
         else:
diff --git a/winforms/src/toga_winforms/widgets/label.py b/winforms/src/toga_winforms/widgets/label.py
index 66c0702ae0..c50f59b5ae 100644
--- a/winforms/src/toga_winforms/widgets/label.py
+++ b/winforms/src/toga_winforms/widgets/label.py
@@ -1,3 +1,5 @@
+from decimal import ROUND_UP
+
 import System.Windows.Forms as WinForms
 from travertino.size import at_least
 
@@ -21,8 +23,9 @@ def set_text(self, value):
         self.native.Text = value
 
     def rehint(self):
-        # Width & height of a label is known and fixed.
-        # self.native.Size = Size(0, 0)
-        # print("REHINT label", self, self.native.PreferredSize)
-        self.interface.intrinsic.width = at_least(self.native.PreferredSize.Width)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.width = self.scale_out(
+            at_least(self.native.PreferredSize.Width), ROUND_UP
+        )
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
diff --git a/winforms/src/toga_winforms/widgets/multilinetextinput.py b/winforms/src/toga_winforms/widgets/multilinetextinput.py
index 681e99a2ac..7111d47c1e 100644
--- a/winforms/src/toga_winforms/widgets/multilinetextinput.py
+++ b/winforms/src/toga_winforms/widgets/multilinetextinput.py
@@ -61,6 +61,7 @@ def set_value(self, value):
             self._set_placeholder_visible(False)
             self.native.Text = value
 
+    # This method is necessary to override the TextInput base class.
     def rehint(self):
         self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
         self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
@@ -68,7 +69,7 @@ def rehint(self):
     def winforms_text_changed(self, sender, event):
         # Showing and hiding the placeholder should not cause an interface event.
         if not self._placeholder_visible:
-            self.interface.on_change(None)
+            self.interface.on_change()
 
     def _set_placeholder_visible(self, visible):
         # Changing ForeColor causes a native TextChanged event, so the order of these
diff --git a/winforms/src/toga_winforms/widgets/numberinput.py b/winforms/src/toga_winforms/widgets/numberinput.py
index 9b677d2d60..a2246af087 100644
--- a/winforms/src/toga_winforms/widgets/numberinput.py
+++ b/winforms/src/toga_winforms/widgets/numberinput.py
@@ -1,9 +1,8 @@
 import sys
-from decimal import Decimal, InvalidOperation
+from decimal import ROUND_UP, Decimal, InvalidOperation
 
 import System.Windows.Forms as WinForms
 from System import Convert, String
-from travertino.size import at_least
 
 from toga.widgets.numberinput import _clean_decimal
 from toga_winforms.libs.fonts import HorizontalTextAlignment
@@ -30,7 +29,7 @@ def create(self):
         self.native.TextChanged += WeakrefCallable(self.winforms_text_changed)
 
     def winforms_text_changed(self, sender, event):
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_readonly(self):
         return self.native.ReadOnly
@@ -68,5 +67,6 @@ def set_alignment(self, value):
         self.native.TextAlign = HorizontalTextAlignment(value)
 
     def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
diff --git a/winforms/src/toga_winforms/widgets/optioncontainer.py b/winforms/src/toga_winforms/widgets/optioncontainer.py
index 15bc0e5813..a6137949bc 100644
--- a/winforms/src/toga_winforms/widgets/optioncontainer.py
+++ b/winforms/src/toga_winforms/widgets/optioncontainer.py
@@ -1,5 +1,4 @@
 from System.Windows.Forms import TabControl, TabPage
-from travertino.size import at_least
 
 from ..container import Container
 from ..libs.wrapper import WeakrefCallable
@@ -58,7 +57,7 @@ def set_current_tab_index(self, current_tab_index):
         self.native.SelectedIndex = current_tab_index
 
     def winforms_selected(self, sender, event):
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def winforms_client_size_changed(self, sender, event):
         for panel in self.panels:
@@ -67,7 +66,3 @@ def winforms_client_size_changed(self, sender, event):
     def resize_content(self, panel):
         size = panel.native_parent.ClientSize
         panel.resize_content(size.Width, size.Height)
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
diff --git a/winforms/src/toga_winforms/widgets/progressbar.py b/winforms/src/toga_winforms/widgets/progressbar.py
index 40628875db..40efc73221 100644
--- a/winforms/src/toga_winforms/widgets/progressbar.py
+++ b/winforms/src/toga_winforms/widgets/progressbar.py
@@ -1,5 +1,6 @@
+from decimal import ROUND_UP
+
 import System.Windows.Forms as WinForms
-from travertino.size import at_least
 
 from .base import Widget
 
@@ -78,7 +79,6 @@ def set_value(self, value):
         self.native.Value = int(value * self.TOGA_SCALE)
 
     def rehint(self):
-        # Height must be non-zero
-        # Set a sensible min-width
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
diff --git a/winforms/src/toga_winforms/widgets/scrollcontainer.py b/winforms/src/toga_winforms/widgets/scrollcontainer.py
index fc7c88b61a..66bf51fc21 100644
--- a/winforms/src/toga_winforms/widgets/scrollcontainer.py
+++ b/winforms/src/toga_winforms/widgets/scrollcontainer.py
@@ -3,7 +3,6 @@
 from System.Drawing import Point
 from System.Windows.Forms import Panel, SystemInformation
 from travertino.node import Node
-from travertino.size import at_least
 
 from toga_winforms.container import Container
 
@@ -41,7 +40,7 @@ def create(self):
         self.native.MouseWheel += WeakrefCallable(self.winforms_scroll)
 
     def winforms_scroll(self, sender, event):
-        self.interface.on_scroll(None)
+        self.interface.on_scroll()
 
     def set_bounds(self, x, y, width, height):
         super().set_bounds(x, y, width, height)
@@ -92,7 +91,7 @@ def get_horizontal(self):
     def set_horizontal(self, value):
         self.horizontal = value
         if not value:
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
         if self.interface.content:
             self.interface.content.refresh()
 
@@ -102,7 +101,7 @@ def get_vertical(self):
     def set_vertical(self, value):
         self.vertical = value
         if not value:
-            self.interface.on_scroll(None)
+            self.interface.on_scroll()
         if self.interface.content:
             self.interface.content.refresh()
 
@@ -127,8 +126,4 @@ def set_position(self, horizontal_position, vertical_position):
             self.scale_in(horizontal_position),
             self.scale_in(vertical_position),
         )
-        self.interface.on_scroll(None)
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
+        self.interface.on_scroll()
diff --git a/winforms/src/toga_winforms/widgets/selection.py b/winforms/src/toga_winforms/widgets/selection.py
index 76453965eb..432cabbc2a 100644
--- a/winforms/src/toga_winforms/widgets/selection.py
+++ b/winforms/src/toga_winforms/widgets/selection.py
@@ -1,7 +1,7 @@
 from contextlib import contextmanager
+from decimal import ROUND_UP
 
 import System.Windows.Forms as WinForms
-from travertino.size import at_least
 
 from ..libs.wrapper import WeakrefCallable
 from .base import Widget
@@ -35,7 +35,7 @@ def suspend_notifications(self):
 
     def on_change(self):
         if self._send_notifications:
-            self.interface.on_change(None)
+            self.interface.on_change()
 
     def clear(self):
         self.native.Items.Clear()
@@ -77,5 +77,6 @@ def get_selected_index(self):
         return None if index == -1 else index
 
     def rehint(self):
-        self.interface.intrinsic.width = at_least(self.native.PreferredSize.Width)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
diff --git a/winforms/src/toga_winforms/widgets/slider.py b/winforms/src/toga_winforms/widgets/slider.py
index 0d5c0cd547..7d6c3481f1 100644
--- a/winforms/src/toga_winforms/widgets/slider.py
+++ b/winforms/src/toga_winforms/widgets/slider.py
@@ -1,5 +1,6 @@
+from decimal import ROUND_UP
+
 import System.Windows.Forms as WinForms
-from travertino.size import at_least
 
 from toga.widgets.slider import IntSliderImpl
 
@@ -34,10 +35,10 @@ def winforms_value_chaned(self, sender, event):
         self.on_change()
 
     def winforms_mouse_down(self, sender, event):
-        self.interface.on_press(None)
+        self.interface.on_press()
 
     def winforms_mouse_up(self, sender, event):
-        self.interface.on_release(None)
+        self.interface.on_release()
 
     def get_int_value(self):
         return self.native.Value
@@ -55,5 +56,6 @@ def set_ticks_visible(self, visible):
         self.native.TickStyle = BOTTOM_RIGHT_TICK_STYLE if visible else NONE_TICK_STYLE
 
     def rehint(self):
-        self.interface.intrinsic.width = at_least(self.native.PreferredSize.Width)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
diff --git a/winforms/src/toga_winforms/widgets/splitcontainer.py b/winforms/src/toga_winforms/widgets/splitcontainer.py
index f2605fd539..812ef3aebe 100644
--- a/winforms/src/toga_winforms/widgets/splitcontainer.py
+++ b/winforms/src/toga_winforms/widgets/splitcontainer.py
@@ -3,7 +3,6 @@
     Orientation,
     SplitContainer as NativeSplitContainer,
 )
-from travertino.size import at_least
 
 from toga.constants import Direction
 
@@ -82,7 +81,3 @@ def resize_content(self, **kwargs):
         for panel in self.panels:
             size = panel.native_parent.ClientSize
             panel.resize_content(size.Width, size.Height, **kwargs)
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
diff --git a/winforms/src/toga_winforms/widgets/switch.py b/winforms/src/toga_winforms/widgets/switch.py
index 33f6702d62..16792bb01e 100644
--- a/winforms/src/toga_winforms/widgets/switch.py
+++ b/winforms/src/toga_winforms/widgets/switch.py
@@ -1,3 +1,5 @@
+from decimal import ROUND_UP
+
 import System.Windows.Forms as WinForms
 from travertino.size import at_least
 
@@ -11,7 +13,7 @@ def create(self):
         self.native.CheckedChanged += WeakrefCallable(self.winforms_checked_changed)
 
     def winforms_checked_changed(self, sender, event):
-        self.interface.on_change(None)
+        self.interface.on_change()
 
     def get_text(self):
         value = self.native.Text
@@ -34,5 +36,9 @@ def set_value(self, value):
         self.native.Checked = value
 
     def rehint(self):
-        self.interface.intrinsic.width = at_least(self.native.PreferredSize.Width)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.width = self.scale_out(
+            at_least(self.native.PreferredSize.Width), ROUND_UP
+        )
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
diff --git a/winforms/src/toga_winforms/widgets/table.py b/winforms/src/toga_winforms/widgets/table.py
index 5b8c1a9b43..bb4689f7d1 100644
--- a/winforms/src/toga_winforms/widgets/table.py
+++ b/winforms/src/toga_winforms/widgets/table.py
@@ -1,7 +1,6 @@
 from warnings import warn
 
 import System.Windows.Forms as WinForms
-from travertino.size import at_least
 
 import toga
 
@@ -110,13 +109,13 @@ def winforms_cache_virtual_items(self, sender, e):
             self._cache.append(self._new_item(i + self._first_item))
 
     def winforms_item_selection_changed(self, sender, e):
-        self.interface.on_select(None)
+        self.interface.on_select()
 
     def winforms_double_click(self, sender, e):
         hit_test = self.native.HitTest(e.X, e.Y)
         item = hit_test.Item
         if item is not None:
-            self.interface.on_activate(None, row=self._data[item.Index])
+            self.interface.on_activate(row=self._data[item.Index])
         else:  # pragma: no cover
             # Double clicking outside of an item apparently doesn't raise the event, but
             # that isn't guaranteed by the documentation.
@@ -160,7 +159,7 @@ def icon(attr):
         def text(attr):
             val = getattr(item, attr, None)
             if isinstance(val, toga.Widget):
-                warn("This backend does not support the use of widgets in cells")
+                warn("Winforms does not support the use of widgets in cells")
                 val = None
             if isinstance(val, tuple):
                 val = val[1]
@@ -217,10 +216,6 @@ def get_selection(self):
     def scroll_to_row(self, index):
         self.native.EnsureVisible(index)
 
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
-
     def remove_column(self, index):
         self.native.Columns.RemoveAt(index)
         self.update_data()
diff --git a/winforms/src/toga_winforms/widgets/textinput.py b/winforms/src/toga_winforms/widgets/textinput.py
index 08ea69b593..68654f3c46 100644
--- a/winforms/src/toga_winforms/widgets/textinput.py
+++ b/winforms/src/toga_winforms/widgets/textinput.py
@@ -1,8 +1,8 @@
 from ctypes import c_uint, windll
 from ctypes.wintypes import HWND, WPARAM
+from decimal import ROUND_UP
 
 import System.Windows.Forms as WinForms
-from travertino.size import at_least
 
 from toga_winforms.colors import native_color
 from toga_winforms.libs.fonts import HorizontalTextAlignment
@@ -71,25 +71,23 @@ def set_color(self, color):
             self.native.ForeColor = self.native.DefaultForeColor
 
     def rehint(self):
-        # Height of a text input is known and fixed.
-        # Width must be > 100
-        # print("REHINT TextInput", self, self.native.PreferredSize)
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
 
     def winforms_text_changed(self, sender, event):
-        self.interface.on_change(self.interface)
+        self.interface.on_change()
         self.interface._validate()
 
     def winforms_key_press(self, sender, event):
         if ord(event.KeyChar) == int(WinForms.Keys.Enter):
-            self.interface.on_confirm(self.interface)
+            self.interface.on_confirm()
 
     def winforms_got_focus(self, sender, event):
-        self.interface.on_gain_focus(self.interface)
+        self.interface.on_gain_focus()
 
     def winforms_lost_focus(self, sender, event):
-        self.interface.on_lose_focus(self.interface)
+        self.interface.on_lose_focus()
 
     def is_valid(self):
         return self.error_provider.GetError(self.native) == ""
diff --git a/winforms/src/toga_winforms/widgets/timeinput.py b/winforms/src/toga_winforms/widgets/timeinput.py
index eb28fb3d58..3f37853eb1 100644
--- a/winforms/src/toga_winforms/widgets/timeinput.py
+++ b/winforms/src/toga_winforms/widgets/timeinput.py
@@ -1,8 +1,8 @@
 import datetime
+from decimal import ROUND_UP
 
 import System.Windows.Forms as WinForms
 from System import DateTime as WinDateTime
-from travertino.size import at_least
 
 from ..libs.wrapper import WeakrefCallable
 from .base import Widget
@@ -46,8 +46,9 @@ def set_max_time(self, value):
         self.native.MaxDate = native_time(value)
 
     def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = self.native.PreferredSize.Height
+        self.interface.intrinsic.height = self.scale_out(
+            self.native.PreferredSize.Height, ROUND_UP
+        )
 
     def winforms_value_changed(self, sender, event):
-        self.interface.on_change(self.interface)
+        self.interface.on_change()
diff --git a/winforms/src/toga_winforms/widgets/webview.py b/winforms/src/toga_winforms/widgets/webview.py
index 9f38f225a5..99a480fb09 100644
--- a/winforms/src/toga_winforms/widgets/webview.py
+++ b/winforms/src/toga_winforms/widgets/webview.py
@@ -9,7 +9,6 @@
 )
 from System.Drawing import Color
 from System.Threading.Tasks import Task, TaskScheduler
-from travertino.size import at_least
 
 import toga
 from toga.widgets.webview import JavaScriptResult
@@ -116,7 +115,7 @@ def winforms_initialization_completed(self, sender, args):
             raise RuntimeError(args.InitializationException)
 
     def winforms_navigation_completed(self, sender, args):
-        self.interface.on_webview_load(self.interface)
+        self.interface.on_webview_load()
 
         if self.loaded_future:
             self.loaded_future.set_result(None)
@@ -174,7 +173,3 @@ def execute():
 
         self.run_after_initialization(execute)
         return result
-
-    def rehint(self):
-        self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
-        self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
diff --git a/winforms/src/toga_winforms/window.py b/winforms/src/toga_winforms/window.py
index e887613531..b76b36a66a 100644
--- a/winforms/src/toga_winforms/window.py
+++ b/winforms/src/toga_winforms/window.py
@@ -1,7 +1,9 @@
 import System.Windows.Forms as WinForms
-from System.Drawing import Point, Size
+from System.Drawing import Bitmap, Graphics, Point, Size
+from System.Drawing.Imaging import ImageFormat
+from System.IO import MemoryStream
 
-from toga import GROUP_BREAK, SECTION_BREAK
+from toga.command import GROUP_BREAK, SECTION_BREAK
 
 from .container import Container
 from .libs.wrapper import WeakrefCallable
@@ -47,6 +49,7 @@ def create_toolbar(self):
                 # defaults to `Top`.
                 self.toolbar_native = WinForms.ToolStrip()
                 self.native.Controls.Add(self.toolbar_native)
+                self.toolbar_native.BringToFront()  # In a dock, "front" means "bottom".
 
             for cmd in self.interface.toolbar:
                 if cmd == GROUP_BREAK:
@@ -54,14 +57,13 @@ def create_toolbar(self):
                 elif cmd == SECTION_BREAK:
                     item = WinForms.ToolStripSeparator()
                 else:
+                    item = WinForms.ToolStripMenuItem(cmd.text)
+                    if cmd.tooltip is not None:
+                        item.ToolTipText = cmd.tooltip
                     if cmd.icon is not None:
-                        native_icon = cmd.icon._impl.native
-                        item = WinForms.ToolStripMenuItem(
-                            cmd.text, native_icon.ToBitmap()
-                        )
-                    else:
-                        item = WinForms.ToolStripMenuItem(cmd.text)
-                    item.Click += WeakrefCallable(cmd._impl.winforms_handler)
+                        item.Image = cmd.icon._impl.native.ToBitmap()
+                    item.Enabled = cmd.enabled
+                    item.Click += WeakrefCallable(cmd._impl.winforms_Click)
                     cmd._impl.native.append(item)
                 self.toolbar_native.Items.Add(item)
 
@@ -80,10 +82,17 @@ def set_position(self, position):
 
     def get_size(self):
         size = self.native.Size
-        return tuple(map(self.scale_out, (size.Width, size.Height)))
+        return (
+            self.scale_out(size.Width - self.decor_width()),
+            self.scale_out(size.Height - self.decor_height()),
+        )
 
     def set_size(self, size):
-        self.native.Size = Size(*map(self.scale_in, size))
+        width, height = size
+        self.native.Size = Size(
+            self.scale_in(width) + self.decor_width(),
+            self.scale_in(height) + self.decor_height(),
+        )
 
     def set_app(self, app):
         icon_impl = app.interface.icon._impl
@@ -97,16 +106,13 @@ def set_title(self, title):
 
     def refreshed(self):
         super().refreshed()
-
-        # Enforce a minimum window size. This takes into account the title bar and
-        # borders, which are included in Size but not in ClientSize.
-        decor_size = self.native.Size - self.native.ClientSize
         layout = self.interface.content.layout
-        min_client_size = Size(
-            self.scale_in(layout.min_width),
-            self.scale_in(layout.min_height) + self.top_bars_height(),
+        self.native.MinimumSize = Size(
+            self.scale_in(layout.min_width) + self.decor_width(),
+            self.scale_in(layout.min_height)
+            + self.top_bars_height()
+            + self.decor_height(),
         )
-        self.native.MinimumSize = decor_size + min_client_size
 
     def show(self):
         if self.interface.content is not None:
@@ -133,7 +139,7 @@ def winforms_FormClosing(self, sender, event):
                 event.Cancel = True
             else:
                 # See _is_closing comment in __init__.
-                self.interface.on_close(None)
+                self.interface.on_close()
                 event.Cancel = True
 
     def set_full_screen(self, is_full_screen):
@@ -151,6 +157,15 @@ def close(self):
         self._is_closing = True
         self.native.Close()
 
+    # "Decor" includes the title bar and the (usually invisible) resize borders. It does
+    # not include the menu bar and toolbar, which are included in the ClientSize (see
+    # top_bars_height).
+    def decor_width(self):
+        return self.native.Size.Width - self.native.ClientSize.Width
+
+    def decor_height(self):
+        return self.native.Size.Height - self.native.ClientSize.Height
+
     def top_bars_height(self):
         vertical_shift = 0
         if self.toolbar_native:
@@ -166,3 +181,18 @@ def resize_content(self):
             self.native.ClientSize.Width,
             self.native.ClientSize.Height - vertical_shift,
         )
+
+    def get_image_data(self):
+        size = Size(self.native_content.Size.Width, self.native_content.Size.Height)
+        bitmap = Bitmap(size.Width, size.Height)
+        graphics = Graphics.FromImage(bitmap)
+
+        graphics.CopyFromScreen(
+            self.native_content.PointToScreen(Point.Empty),
+            Point(0, 0),
+            size,
+        )
+
+        stream = MemoryStream()
+        bitmap.Save(stream, ImageFormat.Png)
+        return stream.ToArray()
diff --git a/winforms/tests/__init__.py b/winforms/tests/__init__.py
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/winforms/tests/test_implementation.py b/winforms/tests/test_implementation.py
deleted file mode 100644
index e8df0c4e38..0000000000
--- a/winforms/tests/test_implementation.py
+++ /dev/null
@@ -1,13 +0,0 @@
-import os
-
-from toga_dummy import test_implementation
-
-globals().update(
-    test_implementation.create_impl_tests(
-        os.path.abspath(
-            os.path.join(
-                os.path.dirname(os.path.dirname(__file__)), "src", "toga_winforms"
-            )
-        )
-    )
-)
diff --git a/winforms/tests_backend/app.py b/winforms/tests_backend/app.py
index 6059da9865..6813613105 100644
--- a/winforms/tests_backend/app.py
+++ b/winforms/tests_backend/app.py
@@ -1,16 +1,28 @@
+import ctypes
 from pathlib import Path
+from time import sleep
 
-import System.Windows.Forms as WinForms
+import pytest
+from System import EventArgs
+from System.Drawing import Point
+from System.Windows.Forms import Application, Cursor
+
+from toga_winforms.keys import toga_to_winforms_key, winforms_to_toga_key
 
 from .probe import BaseProbe
+from .window import WindowProbe
 
 
 class AppProbe(BaseProbe):
+    supports_key = True
+    supports_key_mod3 = False
+
     def __init__(self, app):
         super().__init__()
         self.app = app
+        self.main_window = app.main_window
         # The Winforms Application class is a singleton instance
-        assert self.app._impl.native == WinForms.Application
+        assert self.app._impl.native == Application
 
     @property
     def config_path(self):
@@ -45,3 +57,104 @@ def logs_path(self):
         return (
             Path.home() / "AppData" / "Local" / "Tiberius Yak" / "Toga Testbed" / "Logs"
         )
+
+    @property
+    def is_cursor_visible(self):
+        # Despite what the documentation says, Cursor.Current never returns null in
+        # Windows 10, whether the cursor is over the window or not.
+        #
+        # The following code is based on https://stackoverflow.com/a/12467292, but it
+        # only works when the cursor is over the window.
+        form = self.main_window._impl.native
+        Cursor.Position = Point(
+            form.Location.X + (form.Size.Width // 2),
+            form.Location.Y + (form.Size.Height // 2),
+        )
+
+        # A small delay is apparently required for the new position to take effect.
+        sleep(0.1)
+
+        class POINT(ctypes.Structure):
+            _fields_ = [
+                ("x", ctypes.c_long),
+                ("y", ctypes.c_long),
+            ]
+
+        class CURSORINFO(ctypes.Structure):
+            _fields_ = [
+                ("cbSize", ctypes.c_uint32),
+                ("flags", ctypes.c_uint32),
+                ("hCursor", ctypes.c_void_p),
+                ("ptScreenPos", POINT),
+            ]
+
+        GetCursorInfo = ctypes.windll.user32.GetCursorInfo
+        GetCursorInfo.argtypes = [ctypes.POINTER(CURSORINFO)]
+
+        info = CURSORINFO()
+        info.cbSize = ctypes.sizeof(info)
+        if not GetCursorInfo(ctypes.byref(info)):
+            raise RuntimeError("GetCursorInfo failed")
+
+        # `flags` is 0 or 1 in local testing, but the GitHub Actions runner always
+        # returns 2 ("the system is not drawing the cursor because the user is providing
+        # input through touch or pen instead of the mouse"). hCursor is more reliable.
+        return info.hCursor is not None
+
+    def is_full_screen(self, window):
+        return WindowProbe(self.app, window).is_full_screen
+
+    def content_size(self, window):
+        return WindowProbe(self.app, window).content_size
+
+    def _menu_item(self, path):
+        item = self.main_window._impl.native.MainMenuStrip
+        for i, label in enumerate(path):
+            children = getattr(item, "Items" if i == 0 else "DropDownItems")
+            child_labels = [child.Text for child in children]
+            try:
+                child_index = child_labels.index(label)
+            except ValueError:
+                raise AssertionError(
+                    f"no item named {path[:i+1]}; options are {child_labels}"
+                ) from None
+            item = children[child_index]
+
+        return item
+
+    def _activate_menu_item(self, path):
+        self._menu_item(path).OnClick(EventArgs.Empty)
+
+    def activate_menu_exit(self):
+        self._activate_menu_item(["File", "Exit"])
+
+    def activate_menu_about(self):
+        self._activate_menu_item(["Help", "About Toga Testbed"])
+
+    async def close_about_dialog(self):
+        await WindowProbe(self.app, self.main_window)._close_dialog("\n")
+
+    def activate_menu_visit_homepage(self):
+        self._activate_menu_item(["Help", "Visit homepage"])
+
+    def assert_menu_item(self, path, *, enabled=True):
+        assert self._menu_item(path).Enabled == enabled
+
+    def assert_system_menus(self):
+        self.assert_menu_item(["File", "Preferences"], enabled=False)
+        self.assert_menu_item(["File", "Exit"])
+
+        self.assert_menu_item(["Help", "Visit homepage"])
+        self.assert_menu_item(["Help", "About Toga Testbed"])
+
+    def activate_menu_close_window(self):
+        pytest.xfail("This platform doesn't have a window management menu")
+
+    def activate_menu_close_all_windows(self):
+        pytest.xfail("This platform doesn't have a window management menu")
+
+    def activate_menu_minimize(self):
+        pytest.xfail("This platform doesn't have a window management menu")
+
+    def keystroke(self, combination):
+        return winforms_to_toga_key(toga_to_winforms_key(combination))
diff --git a/winforms/tests_backend/probe.py b/winforms/tests_backend/probe.py
index 6f39139f2b..bc02d4bba2 100644
--- a/winforms/tests_backend/probe.py
+++ b/winforms/tests_backend/probe.py
@@ -48,3 +48,6 @@ async def type_character(self, char, *, shift=False, ctrl=False, alt=False):
         # same app. Unfortunately that makes it difficult to run tests in the
         # background.
         SendKeys.SendWait(key_code)
+
+    def assert_image_size(self, image_size, size):
+        assert image_size == (size[0] * self.scale_factor, size[1] * self.scale_factor)
diff --git a/winforms/tests_backend/widgets/canvas.py b/winforms/tests_backend/widgets/canvas.py
index 43b84bfe21..c102b7d8f3 100644
--- a/winforms/tests_backend/widgets/canvas.py
+++ b/winforms/tests_backend/widgets/canvas.py
@@ -17,10 +17,6 @@ def reference_variant(self, reference):
     def get_image(self):
         return Image.open(BytesIO(self.impl.get_image_data()))
 
-    def assert_image_size(self, image, width, height):
-        assert image.width == width * self.scale_factor
-        assert image.height == height * self.scale_factor
-
     async def mouse_press(self, x, y, **kwargs):
         self.native.OnMouseDown(self.mouse_event(x, y, **kwargs))
         self.native.OnMouseUp(self.mouse_event(x, y, **kwargs))
@@ -32,10 +28,12 @@ async def mouse_activate(self, x, y, **kwargs):
         self.native.OnMouseUp(self.mouse_event(x, y, clicks=2, **kwargs))
 
     async def mouse_drag(self, x1, y1, x2, y2, **kwargs):
+        # Without a mouse button pressed, a move event should be ignored.
+        move_event = self.mouse_event((x1 + x2) // 2, (y1 + y2) // 2, **kwargs)
+        self.native.OnMouseMove(move_event)
+
         self.native.OnMouseDown(self.mouse_event(x1, y1, **kwargs))
-        self.native.OnMouseMove(
-            self.mouse_event((x1 + x2) // 2, (y1 + y2) // 2, **kwargs)
-        )
+        self.native.OnMouseMove(move_event)
         self.native.OnMouseUp(self.mouse_event(x2, y2, **kwargs))
 
     async def alt_mouse_press(self, x, y):
diff --git a/winforms/tests_backend/window.py b/winforms/tests_backend/window.py
index f560aca484..5fc6ae3c94 100644
--- a/winforms/tests_backend/window.py
+++ b/winforms/tests_backend/window.py
@@ -1,7 +1,15 @@
 import asyncio
 from unittest.mock import Mock
 
-from System.Windows.Forms import Form, FormBorderStyle, FormWindowState
+from System import EventArgs
+from System.Windows.Forms import (
+    Form,
+    FormBorderStyle,
+    FormWindowState,
+    MenuStrip,
+    ToolStrip,
+    ToolStripSeparator,
+)
 
 from .probe import BaseProbe
 
@@ -33,8 +41,11 @@ def close(self):
     @property
     def content_size(self):
         return (
-            self.native.ClientSize.Width / self.scale_factor,
-            self.native.ClientSize.Height / self.scale_factor,
+            (self.native.ClientSize.Width) / self.scale_factor,
+            (
+                (self.native.ClientSize.Height - self.impl.top_bars_height())
+                / self.scale_factor
+            ),
         )
 
     @property
@@ -111,3 +122,29 @@ async def close_select_folder_dialog(self, dialog, result, multiple_select):
         else:
             dialog.native.SelectedPath = str(result[-1] if multiple_select else result)
             await self._close_dialog("\n")
+
+    def _native_toolbar(self):
+        for control in self.native.Controls:
+            if isinstance(control, ToolStrip) and not isinstance(control, MenuStrip):
+                return control
+        else:
+            return None
+
+    def has_toolbar(self):
+        return self._native_toolbar() is not None
+
+    def _native_toolbar_item(self, index):
+        return self._native_toolbar().Items[index]
+
+    def assert_is_toolbar_separator(self, index, section=False):
+        assert isinstance(self._native_toolbar_item(index), ToolStripSeparator)
+
+    def assert_toolbar_item(self, index, label, tooltip, has_icon, enabled):
+        item = self._native_toolbar_item(index)
+        assert item.Text == label
+        assert item.ToolTipText == tooltip
+        assert (item.Image is not None) == has_icon
+        assert item.Enabled == enabled
+
+    def press_toolbar_button(self, index):
+        self._native_toolbar_item(index).OnClick(EventArgs.Empty)