implement lazy loading in toga_core

android/src/toga_android/widgets/slider.py

@@ -5,7 +5,7 @@
 from android.widget import SeekBar
 from java import dynamic_proxy
 
-import toga
+from toga.widgets.slider import IntSliderImpl
 
 from .base import Widget
 
@@ -31,7 +31,7 @@ def onStopTrackingTouch(self, native_seekbar):
  self.impl.interface.on_release()
 
 
-class Slider(Widget, toga.widgets.slider.IntSliderImpl):
+class Slider(Widget, IntSliderImpl):
  focusable = False
  TICK_DRAWABLE = None
 

changes/2547.misc.rst

@@ -0,0 +1 @@
+Imports from the ``toga`` core namespace has been modified to use lazy importing.

cocoa/src/toga_cocoa/widgets/slider.py

@@ -1,6 +1,6 @@
 from travertino.size import at_least
 
-import toga
+from toga.widgets.slider import SliderImpl
 from toga_cocoa.libs import (
  SEL,
  NSEventType,
@@ -27,7 +27,7 @@ def onSlide_(self, sender) -> None:
  self.interface.on_change()
 
 
-class Slider(Widget, toga.widgets.slider.SliderImpl):
+class Slider(Widget, SliderImpl):
  def create(self):
  self.native = TogaSlider.alloc().init()
  self.native.interface = self.interface

core/src/toga/__init__.py

@@ -1,54 +1,94 @@
 from __future__ import annotations
 
+import importlib
+import importlib.util
 import warnings
 from pathlib import Path
 
-from .app import App, DocumentApp
-from .colors import hsl, hsla, rgb, rgba
-from .command import Command, Group
-from .dialogs import (
- ConfirmDialog,
- ErrorDialog,
- InfoDialog,
- OpenFileDialog,
- QuestionDialog,
- SaveFileDialog,
- SelectFolderDialog,
- StackTraceDialog,
-)
-from .documents import Document
-from .fonts import Font
-from .icons import Icon
-from .images import Image
-from .keys import Key
-from .types import LatLng, Position, Size
-from .widgets.activityindicator import ActivityIndicator
-from .widgets.base import Widget
-from .widgets.box import Box
-from .widgets.button import Button
-from .widgets.canvas import Canvas
-from .widgets.dateinput import DateInput, DatePicker
-from .widgets.detailedlist import DetailedList
-from .widgets.divider import Divider
-from .widgets.imageview import ImageView
-from .widgets.label import Label
-from .widgets.mapview import MapPin, MapView
-from .widgets.multilinetextinput import MultilineTextInput
-from .widgets.numberinput import NumberInput
-from .widgets.optioncontainer import OptionContainer, OptionItem
-from .widgets.passwordinput import PasswordInput
-from .widgets.progressbar import ProgressBar
-from .widgets.scrollcontainer import ScrollContainer
-from .widgets.selection import Selection
-from .widgets.slider import Slider
-from .widgets.splitcontainer import SplitContainer
-from .widgets.switch import Switch
-from .widgets.table import Table
-from .widgets.textinput import TextInput
-from .widgets.timeinput import TimeInput, TimePicker
-from .widgets.tree import Tree
-from .widgets.webview import WebView
-from .window import DocumentMainWindow, MainWindow, Window
+toga_core_imports = {
+ # toga.app imports
+ "App": "toga.app",
+ "DocumentApp": "toga.app",
+ # toga.colors imports
+ "hsl": "toga.colors",
+ "hsla": "toga.colors",
+ "rgb": "toga.colors",
+ "rgba": "toga.colors",
+ # toga.command imports
+ "Command": "toga.command",
+ "Group": "toga.command",
+ # toga.dialogs imports
+ "ConfirmDialog": "toga.dialogs",
+ "ErrorDialog": "toga.dialogs",
+ "InfoDialog": "toga.dialogs",
+ "OpenFileDialog": "toga.dialogs",
+ "QuestionDialog": "toga.dialogs",
+ "SaveFileDialog": "toga.dialogs",
+ "SelectFolderDialog": "toga.dialogs",
+ "StackTraceDialog": "toga.dialogs",
+ # toga.documents imports
+ "Document": "toga.documents",
+ # toga.fonts imports
+ "Font": "toga.fonts",
+ # toga.icons imports
+ "Icon": "toga.icons",
+ # toga.images imports
+ "Image": "toga.images",
+ # toga.keys imports
+ "Key": "toga.keys",
+ # toga.types imports
+ "LatLng": "toga.types",
+ "Position": "toga.types",
+ "Size": "toga.types",
+ # toga.widgets imports
+ "ActivityIndicator": "toga.widgets.activityindicator",
+ "Widget": "toga.widgets.base",
+ "Box": "toga.widgets.box",
+ "Button": "toga.widgets.button",
+ "Canvas": "toga.widgets.canvas",
+ "DateInput": "toga.widgets.dateinput",
+ "DatePicker": "toga.widgets.dateinput",
+ "DetailedList": "toga.widgets.detailedlist",
+ "Divider": "toga.widgets.divider",
+ "ImageView": "toga.widgets.imageview",
+ "Label": "toga.widgets.label",
+ "MapPin": "toga.widgets.mapview",
+ "MapView": "toga.widgets.mapview",
+ "MultilineTextInput": "toga.widgets.multilinetextinput",
+ "NumberInput": "toga.widgets.numberinput",
+ "OptionContainer": "toga.widgets.optioncontainer",
+ "OptionItem": "toga.widgets.optioncontainer",
+ "PasswordInput": "toga.widgets.passwordinput",
+ "ProgressBar": "toga.widgets.progressbar",
+ "ScrollContainer": "toga.widgets.scrollcontainer",
+ "Selection": "toga.widgets.selection",
+ "Slider": "toga.widgets.slider",
+ "SplitContainer": "toga.widgets.splitcontainer",
+ "Switch": "toga.widgets.switch",
+ "Table": "toga.widgets.table",
+ "TextInput": "toga.widgets.textinput",
+ "TimeInput": "toga.widgets.timeinput",
+ "TimePicker": "toga.widgets.timeinput",
+ "Tree": "toga.widgets.tree",
+ "WebView": "toga.widgets.webview",
+ # toga.window imports
+ "DocumentMainWindow": "toga.window",
+ "MainWindow": "toga.window",
+ "Window": "toga.window",
+}
+__all__ = list(toga_core_imports.keys())
+
+
+def __getattr__(name):
+ try:
+ module_name = toga_core_imports[name]
+ except KeyError:
+ raise AttributeError(f"module '{__name__}' has no attribute '{name}'") from None
+ else:
+ module = importlib.import_module(module_name)
+ value = getattr(module, name)
+ globals()[name] = value
+ return value
 
 
 class NotImplementedWarning(RuntimeWarning):
@@ -61,78 +101,6 @@ def warn(cls, platform: str, feature: str) -> None:
  warnings.warn(NotImplementedWarning(f"[{platform}] Not implemented: {feature}"))
 
 
-__all__ = [
- "NotImplementedWarning",
- # Applications
- "App",
- "DocumentApp",
- # Commands
- "Command",
- "Group",
- # Documents
- "Document",
- # Dialogs
- "ConfirmDialog",
- "ErrorDialog",
- "InfoDialog",
- "OpenFileDialog",
- "QuestionDialog",
- "SaveFileDialog",
- "SelectFolderDialog",
- "StackTraceDialog",
- # Keys
- "Key",
- # Resources
- "hsl",
- "hsla",
- "rgb",
- "rgba",
- "Font",
- "Icon",
- "Image",
- # Types
- "LatLng",
- "Position",
- "Size",
- # Widgets
- "ActivityIndicator",
- "Box",
- "Button",
- "Canvas",
- "DateInput",
- "DetailedList",
- "Divider",
- "ImageView",
- "Label",
- "MapPin",
- "MapView",
- "MultilineTextInput",
- "NumberInput",
- "OptionContainer",
- "OptionItem",
- "PasswordInput",
- "ProgressBar",
- "ScrollContainer",
- "Selection",
- "Slider",
- "SplitContainer",
- "Switch",
- "Table",
- "TextInput",
- "TimeInput",
- "Tree",
- "WebView",
- "Widget",
- # Windows
- "DocumentMainWindow",
- "MainWindow",
- "Window",
- # Deprecated widget names
- "DatePicker",
- "TimePicker",
-]
-
-
 def _package_version(file: Path | str | None, name: str) -> str:
  try:
  # Read version from SCM metadata

dummy/src/toga_dummy/widgets/slider.py

@@ -1,9 +1,9 @@
-import toga
+from toga.widgets.slider import SliderImpl
 
 from .base import Widget
 
 
-class Slider(Widget, toga.widgets.slider.SliderImpl):
+class Slider(Widget, SliderImpl):
  def create(self):
  self._action("create Slider")
 

gtk/src/toga_gtk/widgets/slider.py

@@ -1,6 +1,6 @@
 from travertino.size import at_least
 
-import toga
+from toga.widgets.slider import SliderImpl
 
 from ..libs import Gtk
 from .base import Widget
@@ -16,7 +16,7 @@
 # to line up at the same values.
 
 
-class Slider(Widget, toga.widgets.slider.SliderImpl):
+class Slider(Widget, SliderImpl):
  def create(self):
  self.adj = Gtk.Adjustment()
  self.native = Gtk.Scale.new(Gtk.Orientation.HORIZONTAL, self.adj)