Improved DPI Scaling on Windows and Fixed related Bugs

changes/2155.bugfix.rst

@@ -0,0 +1 @@
+DPI scaling on Windows was improved and related bugs were fixed.

testbed/tests/test_app.py

@@ -1,3 +1,5 @@
+import io
+import traceback
 from unittest.mock import Mock
 
 import pytest
@@ -550,3 +552,148 @@ async def test_beep(app):
     # can be invoked without raising an error, but there's no way to verify that the app
     # actually made a noise.
     app.beep()
+
+
+# This test is windows specific
+if toga.platform.current_platform == "windows":
+
+    async def test_system_dpi_change(
+        monkeypatch, app, app_probe, main_window, main_window_probe
+    ):
+        # For restoring original behavior after completion of test.
+        original_values = dict()
+        # --------------------------------- Set up for testing ---------------------------------
+        # For toolbar
+        main_window.toolbar.add(app.cmd1, app.cmd2)
+        # For stack trace dialog
+        on_result_handler = Mock()
+        stack = io.StringIO()
+        traceback.print_stack(file=stack)
+        dialog_result = main_window.stack_trace_dialog(
+            "Stack Trace",
+            "Some stack trace",
+            stack.getvalue(),
+            retry=True,
+            on_result=on_result_handler,
+        )
+
+        # ----------------------- Setup Mock values for testing -----------------------
+        # For main_window
+        original_values["main_window_update_scale"] = main_window._impl.update_scale
+        main_window_update_scale_mock = Mock()
+        monkeypatch.setattr(
+            main_window._impl, "update_scale", main_window_update_scale_mock
+        )
+        original_values["main_window_resize_content"] = main_window._impl.resize_content
+        main_window_resize_content_mock = Mock()
+        monkeypatch.setattr(
+            main_window._impl, "resize_content", main_window_resize_content_mock
+        )
+
+        window1 = toga.Window("Test Window 1")
+        window1.content = toga.Box()
+        window1_probe = window_probe(app, window1)
+        window1.show()
+        await window1_probe.wait_for_window("Extra windows added")
+
+        # For window1
+        original_values["window1_update_scale"] = window1._impl.update_scale
+        window1_update_scale_mock = Mock()
+        monkeypatch.setattr(window1._impl, "update_scale", window1_update_scale_mock)
+        original_values["window1_resize_content"] = window1._impl.resize_content
+        window1_resize_content_mock = Mock()
+        monkeypatch.setattr(
+            window1._impl, "resize_content", window1_resize_content_mock
+        )
+        original_values[
+            "window1_update_toolbar_font_scale"
+        ] = window1._impl.update_toolbar_font_scale
+        window1_update_toolbar_font_scale_mock = Mock()
+        monkeypatch.setattr(
+            window1._impl,
+            "update_toolbar_font_scale",
+            window1_update_toolbar_font_scale_mock,
+        )
+        # -----------------------------------------------------------------------------
+        # Explicitly set the dpi_scale for testing
+        main_window._impl.dpi_scale = 1.5
+        window1._impl.dpi_scale = 1.5
+        # --------------------------------------------------------------------------------------
+        await main_window_probe.redraw(
+            "Triggering DPI change event for testing property changes"
+        )
+        app_probe.trigger_dpi_change_event()
+
+        # Test out properties which should change on dpi change
+        main_window._impl.update_scale.assert_called_once()
+        window1._impl.update_scale.assert_called_once()
+        assert main_window_probe.has_toolbar()
+        app_probe.assert_main_window_toolbar_font_scale_updated()
+        assert not window1_probe.has_toolbar()
+        window1._impl.update_toolbar_font_scale.assert_not_called()
+        app_probe.assert_main_window_menubar_font_scale_updated()
+        assert not hasattr(window1._impl, "update_menubar_font_scale")
+        app_probe.assert_main_window_widgets_font_scale_updated()
+        main_window._impl.resize_content.assert_called_once()
+        window1._impl.resize_content.assert_called_once()
+        app_probe.assert_main_window_stack_trace_dialog_scale_updated()
+        assert not hasattr(window1._impl, "current_stack_trace_dialog_impl")
+
+        # Test if widget.refresh is called once on each widget
+        for window in app.windows:
+            for widget in window.widgets:
+                original_values[id(widget)] = widget.refresh
+                monkeypatch.setattr(widget, "refresh", Mock())
+
+        await main_window_probe.redraw(
+            "Triggering DPI change event for testing widget refresh calls"
+        )
+        app_probe.trigger_dpi_change_event()
+
+        for window in app.windows:
+            for widget in main_window.widgets:
+                widget.refresh.assert_called_once()
+
+        # Restore original state
+        for window in app.windows:
+            for widget in window.widgets:
+                monkeypatch.setattr(widget, "refresh", original_values[id(widget)])
+        monkeypatch.setattr(
+            window1._impl,
+            "update_toolbar_font_scale",
+            original_values["window1_update_toolbar_font_scale"],
+        )
+        monkeypatch.setattr(
+            window1._impl, "resize_content", original_values["window1_resize_content"]
+        )
+        monkeypatch.setattr(
+            window1._impl, "update_scale", original_values["window1_update_scale"]
+        )
+        monkeypatch.setattr(
+            main_window._impl,
+            "resize_content",
+            original_values["main_window_resize_content"],
+        )
+        monkeypatch.setattr(
+            main_window._impl,
+            "update_scale",
+            original_values["main_window_update_scale"],
+        )
+
+        # When dpi_scale is None then calculated dpi_scale should be equal to
+        # dpi scale of Primary Screen
+        for window in app.windows:
+            window._impl.dpi_scale = None
+            app_probe.assert_dpi_scale_equal_to_primary_screen_dpi_scale(window)
+
+        # Restore original state
+        for window in app.windows:
+            window._impl.dpi_scale = 1.0
+        await main_window_probe.redraw(
+            "Triggering DPI change event for restoring original state"
+        )
+
+        app_probe.trigger_dpi_change_event()
+        await main_window_probe.close_stack_trace_dialog(dialog_result._impl, True)
+        main_window.toolbar.clear()
+        window1.close()

winforms/src/toga_winforms/app.py

@@ -2,11 +2,13 @@
 import re
 import sys
 import threading
-from ctypes import windll
+from ctypes import c_bool, c_void_p, windll
 
 import System.Windows.Forms as WinForms
+from Microsoft.Win32 import SystemEvents
 from System import Environment, Threading
 from System.ComponentModel import InvalidEnumArgumentException
+from System.Drawing import Font as WinFont
 from System.Media import SystemSounds
 from System.Net import SecurityProtocolType, ServicePointManager
 from System.Windows.Threading import Dispatcher
@@ -18,10 +20,20 @@
 from .keys import toga_to_winforms_key
 from .libs.proactor import WinformsProactorEventLoop
 from .libs.wrapper import WeakrefCallable
+from .widgets.base import Scalable
 from .window import Window
 
 
 class MainWindow(Window):
+    def update_menubar_font_scale(self):
+        # Directly using self.native.MainMenuStrip.Font instead of
+        # original_menubar_font makes the menubar font to not scale down.
+        self.native.MainMenuStrip.Font = WinFont(
+            self.original_menubar_font.FontFamily,
+            self.scale_font(self.original_menubar_font.Size),
+            self.original_menubar_font.Style,
+        )
+
     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.
@@ -33,9 +45,36 @@ def winforms_FormClosing(self, sender, event):
             event.Cancel = True
 
 
-class App:
+class App(Scalable):
     _MAIN_WINDOW_CLASS = MainWindow
 
+    # ------------------- Set the DPI Awareness mode for the process -------------------
+    # This needs to be done at the earliest and doing this in __init__() or
+    # in create() doesn't work
+    #
+    # Check the version of windows and make sure we are setting the DPI mode
+    # with the most up to date API
+    # Windows Versioning Check Sources : https://www.lifewire.com/windows-version-numbers-2625171
+    # and https://docs.microsoft.com/en-us/windows/release-information/
+    win_version = Environment.OSVersion.Version
+    # Represents Windows 10 Build 1703 and beyond which should use
+    # SetProcessDpiAwarenessContext(-4) for DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2
+    # Valid values: https://learn.microsoft.com/en-us/windows/win32/hidpi/dpi-awareness-context
+    if (win_version.Major > 10) or (
+        win_version.Major == 10 and win_version.Build >= 15063
+    ):
+        windll.user32.SetProcessDpiAwarenessContext.restype = c_bool
+        windll.user32.SetProcessDpiAwarenessContext.argtypes = [c_void_p]
+        # SetProcessDpiAwarenessContext returns False on Failure
+        if not windll.user32.SetProcessDpiAwarenessContext(-4):  # pragma: no cover
+            print("WARNING: Failed to set the DPI Awareness mode for the app.")
+    else:  # pragma: no cover
+        print(
+            "WARNING: Your Windows version doesn't support DPI Awareness setting.  "
+            "We recommend you upgrade to at least Windows 10 Build 1703."
+        )
+    # ----------------------------------------------------------------------------------
+
     def __init__(self, interface):
         self.interface = interface
         self.interface._impl = self
@@ -62,33 +101,15 @@ def create(self):
         self.app_context = WinForms.ApplicationContext()
         self.app_dispatcher = Dispatcher.CurrentDispatcher
 
-        # Check the version of windows and make sure we are setting the DPI mode
-        # with the most up to date API
-        # Windows Versioning Check Sources : https://www.lifewire.com/windows-version-numbers-2625171
-        # and https://docs.microsoft.com/en-us/windows/release-information/
-        win_version = Environment.OSVersion.Version
-        if win_version.Major >= 6:  # Checks for Windows Vista or later
-            # Represents Windows 8.1 up to Windows 10 before Build 1703 which should use
-            # 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.  "
-                    "We recommend you upgrade to at least Windows 10 Build 1703."
-                )
-            # Represents Windows 10 Build 1703 and beyond which should use
-            # SetProcessDpiAwarenessContext(-2)
-            elif win_version.Major == 10 and win_version.Build >= 15063:
-                windll.user32.SetProcessDpiAwarenessContext(-2)
-            # Any other version of windows should use SetProcessDPIAware()
-            else:  # pragma: no cover
-                windll.user32.SetProcessDPIAware()
-
+        # These are required for properly setting up DPI mode
         self.native.EnableVisualStyles()
         self.native.SetCompatibleTextRenderingDefault(False)
 
+        # Register the DisplaySettingsChanged event handler
+        SystemEvents.DisplaySettingsChanged += WeakrefCallable(
+            self.winforms_DisplaySettingsChanged
+        )
+
         # Ensure that TLS1.2 and TLS1.3 are enabled for HTTPS connections.
         # For some reason, some Windows installs have these protocols
         # turned off by default. SSL3, TLS1.0 and TLS1.1 are *not* enabled
@@ -163,6 +184,8 @@ def create_menus(self):
                 cmd._impl.native.append(item)
                 submenu.DropDownItems.Add(item)
 
+        # Required for font scaling on DPI changes
+        window.original_menubar_font = menubar.Font
         window.resize_content()
 
     def _submenu(self, group, menubar):
@@ -338,6 +361,21 @@ def hide_cursor(self):
             WinForms.Cursor.Hide()
         self._cursor_visible = False
 
+    def winforms_DisplaySettingsChanged(self, sender, event):
+        for window in self.interface.windows:
+            window._impl.update_scale(
+                screen=WinForms.Screen.FromControl(window._impl.native)
+            )
+            if window._impl.toolbar_native is not None:
+                window._impl.update_toolbar_font_scale()
+            if isinstance(window._impl, MainWindow):
+                window._impl.update_menubar_font_scale()
+            for widget in window.widgets:
+                widget.refresh()
+            window._impl.resize_content()
+            if hasattr(window._impl, "current_stack_trace_dialog_impl"):
+                window._impl.current_stack_trace_dialog_impl.resize_content()
+
 
 class DocumentApp(App):  # pragma: no cover
     def _create_app_commands(self):

winforms/src/toga_winforms/container.py

@@ -6,7 +6,6 @@
 
 class Container(Scalable):
     def __init__(self, native_parent):
-        self.init_scale(native_parent)
         self.native_parent = native_parent
         self.native_width = self.native_height = 0
         self.content = None