Add a Windows backend

.gitignore

@@ -3,13 +3,15 @@ __pycache__/
 .coverage
 .coverage.*
 .DS_Store
+.idea/
 .kilo
 .opencode
 .pytest_cache/
 .ruff_cache/
 .rumdl_cache/
 .tox/
 .venv*
+.vscode/
 *.dist-info/
 *.egg-info/
 *.py[cod]

README.md

@@ -1,19 +1,16 @@
 # toga-code-editor
 
-A [Toga](https://toga.beeware.org) widget for editing code, with line numbers and syntax highlighting. `CodeEditor` is a `toga.MultilineTextInput` that colors its text with [Pygments](https://pygments.org) and shows a line-number gutter. It supports macOS, iOS, and Android.
+A [Toga](https://toga.beeware.org) widget for editing code, with line numbers and syntax highlighting. `CodeEditor` is a `toga.MultilineTextInput` that colors its text with [Pygments](https://pygments.org) and shows a line-number gutter. It supports macOS, Windows, iOS, and Android.
 
 ## Installation
 
 ```console
 pip install toga-code-editor
 ```
 
-The package depends on `toga-core` and `pygments`. Your app installs the Toga backend for its platform as usual; `toga-code-editor` contributes its implementation for that backend through entry points, the same way Toga's own widgets are found.
-
 ## Usage
 
 ```python
-import toga
 from toga_code_editor import CodeEditor, language_for_filename
 
 editor = CodeEditor(
@@ -34,11 +31,11 @@ editor.language = language_for_filename(path)
 - `show_line_numbers`: shows or hides the gutter. Default `True`.
 - `theme`: a mapping from `TokenKind` to `Style`. `None` selects the built-in `DEFAULT_THEME`.
 
-Unless you give the widget a font family, it uses a monospace font. Autocorrect, smart quotes, smart dashes, auto-capitalization, and spell checking are always off.
+Unless you give the widget a font family, it uses a monospace font. Autocorrect, smart quotes, smart dashes, smart insert and delete, auto-capitalization, and spell checking are always off.
 
 ### Themes
 
-A theme is a plain mapping. Kinds you leave out are drawn in the widget's normal text color.
+A theme is a Python mapping between "kinds" of content, and a text style definition. The `DEFAULT_THEME` can be customized:
 
 ```python
 from toga_code_editor import DEFAULT_THEME, Style, TokenKind
@@ -51,15 +48,17 @@ theme = {
 editor.theme = theme
 ```
 
-`Style.color` accepts anything Toga's color properties accept. The token kinds are `KEYWORD`, `BUILTIN`, `DEFINITION`, `DECORATOR`, `STRING`, `NUMBER`, `COMMENT`, `OPERATOR`, `PUNCTUATION`, `TAG`, `ATTRIBUTE`, and `VARIABLE`.
+`Style.color` accepts anything Toga's color properties accept. The token kinds are `KEYWORD`, `BUILTIN`, `DEFINITION`, `DECORATOR`, `STRING`, `NUMBER`, `COMMENT`, `OPERATOR`, `PUNCTUATION`, `TAG`, `ATTRIBUTE`, and `VARIABLE`. Everything else, including plain names, uses a kind of `TEXT`, which is never styled.
 
 ## Platform notes
 
 - **macOS** uses an `NSRulerView` for the gutter and the system's adaptive color mapping, so theme colors follow dark mode.
+- **Windows** paints the gutter beside a `RichTextBox` and colors text through RichEdit's character formatting, with undo recording suspended while it paints, so Ctrl+Z still undoes typing. Theme colors do not change with the system appearance; WinForms draws the editor light. Tab inserts a tab, and Ctrl+V pastes plain text.
+- **Android** 12 and later are supported. The example app is checked on Android 12 and Android 15 emulators.
 - **iOS** and **Android** draw the gutter themselves. Theme colors do not change with the system appearance; the default theme is chosen to be legible on both light and dark backgrounds.
 - Highlighting re-lexes the whole buffer after a short pause in typing. Files of a few thousand lines are fine on a desktop; very large files are slower on phones.
 - Some third-party Android keyboards ignore the flag that disables suggestions.
-- On Android, the widget asks the window to shrink its content when the soft keyboard appears, so the editor scrolls internally and the rest of the layout stays put. It only does this when the app has not chosen a soft-input mode itself.
+- On Android, the widget asks the window to shrink its content when the soft keyboard appears, so the editor scrolls internally and the rest of the layout stays put. It only does this when the app has not chosen a soft-input mode itself. Android deprecated that request in API 30 in favour of handling window insets, so a future release may stop honouring it. With Briefcase's current template, which targets SDK 36 and enables edge-to-edge drawing, the layout still shrinks for the keyboard on Android 12 and Android 15 emulators.
 
 ## Developing
 
@@ -69,16 +68,18 @@ uv pip install -e . --group dev
 .venv/bin/tox -m test
 ```
 
+On Windows the virtual environment's scripts are in `.venv\Scripts` rather than `.venv/bin`; activate it with `.venv\Scripts\activate` before running `tox` or `briefcase`.
+
 The test suite runs against Toga's dummy backend. Real backends are checked with the example app in `examples/editor`:
 
 ```console
 cd examples/editor
-briefcase dev            # macOS
+briefcase dev            # macOS and Windows
 briefcase run iOS
 briefcase run android
 ```
 
-On macOS and iOS the example installs the widget straight from this repository; add `-r` after changing the widget source so Briefcase reinstalls it. On Android the example installs the widget from a wheel in `dist/`, because Gradle rejects a path requirement whose directory contains the Android build tree. Build the wheel before each Android run that should pick up widget changes:
+On macOS, Windows, and iOS, the example installs the widget straight from this repository; add `-r` after changing the widget source so Briefcase reinstalls it. On Android the example installs the widget from a wheel in `dist/`, because Gradle rejects a path requirement whose directory contains the Android build tree. Build the wheel from the repository root before each Android run that should pick up widget changes:
 
 ```console
 uv build --wheel

changes/5.bugfix.md

@@ -0,0 +1 @@
+Closed the minor findings from the initial review: the editor paints once at construction, re-highlight failures are reported immediately, pasted rich text is stripped on macOS and Android, and the default theme is read-only.

examples/editor/pyproject.toml

@@ -18,9 +18,9 @@ license-files = ["../../LICENSE"]
 author = "Kattni"
 author_email = "hello@kattni.com"
 description = "A code editor demonstrating the toga-code-editor widget."
-# macOS and iOS install the widget from this repository; Android installs it from a
-# built wheel (run `uv build` first), because Gradle rejects a path requirement whose
-# directory contains the Android build tree.
+# macOS, Windows, and iOS install the widget from this repository; Android installs it
+# from a built wheel (run `uv build --wheel` from the repository root first), because
+# Gradle rejects a path requirement whose directory contains the Android build tree.
 requires = []
 
 [tool.briefcase.app.editor]
@@ -31,20 +31,29 @@ sources = ["src/editor"]
 requires = [
     "../..",
     "toga-cocoa ~= 0.5.7",
-    "std-nslog >= 1.0.0",
+    "std-nslog~=2.0.0; python_version < '3.14'",
+]
+
+[tool.briefcase.app.editor.windows]
+requires = [
+    "../..",
+    "toga-winforms ~= 0.5.7",
 ]
 
 [tool.briefcase.app.editor.iOS]
 requires = [
     "../..",
     "toga-iOS ~= 0.5.7",
-    "std-nslog >= 1.0.0",
 ]
 
 [tool.briefcase.app.editor.android]
+requirement_installer_args = [
+    "-f", "../../dist",
+    "--pre",
+]
 requires = [
-    "../../dist/toga_code_editor-0.1.0.dev0-py3-none-any.whl",
-    "toga-android ~= 0.5.7",
+    "toga_code_editor",
+    "toga-android ~= 0.5.7"
 ]
 base_theme = "Theme.MaterialComponents.Light.DarkActionBar"
 build_gradle_dependencies = [

examples/editor/src/editor/app.py

@@ -2,10 +2,12 @@
 
 import toga
 from toga.constants import COLUMN, ROW
+from toga.platform import current_platform
 
 from toga_code_editor import CodeEditor, language_for_filename
 
 SAMPLES = Path(__file__).parent / "resources" / "samples"
+MOBILE = current_platform in {"iOS", "android"}
 NO_LANGUAGE = "none"
 LANGUAGES = ["python", "json", "html", NO_LANGUAGE]
 
@@ -14,7 +16,11 @@ class Editor(toga.App):
     def startup(self):
         self.editor = CodeEditor(flex=1, on_change=self.on_edit)
         self.sample = toga.Selection(
-            items=sorted(path.name for path in SAMPLES.iterdir()),
+            items=sorted(
+                path.name
+                for path in SAMPLES.iterdir()
+                if path.is_file() and not path.name.startswith(".")
+            ),
             on_change=self.load_sample,
         )
         self.language = toga.Selection(items=LANGUAGES, on_change=self.set_language)
@@ -23,21 +29,15 @@ def startup(self):
         )
         self.status = toga.Label("", flex=1)
 
-        # Two rows so the controls fit a phone's width.
+        # Two rows on mobile, so the controls fit a narrow screen.
+        if MOBILE:
+            rows = [[self.sample, self.language], [self.line_numbers, self.status]]
+        else:
+            rows = [[self.sample, self.language, self.line_numbers, self.status]]
         toolbar = toga.Box(
             children=[
-                toga.Box(
-                    children=[self.sample, self.language],
-                    direction=ROW,
-                    align_items="center",
-                    gap=5,
-                ),
-                toga.Box(
-                    children=[self.line_numbers, self.status],
-                    direction=ROW,
-                    align_items="center",
-                    gap=5,
-                ),
+                toga.Box(children=row, direction=ROW, align_items="center", gap=5)
+                for row in rows
             ],
             direction=COLUMN,
             margin=5,

pyproject.toml

@@ -30,7 +30,7 @@ classifiers = [
     "Topic :: Software Development :: Widget Sets",
 ]
 dependencies = [
-    "toga-core >= 0.5.7",
+    "toga-core >= 0.5.7, < 0.6",
     "pygments >= 2.19",
 ]
 
@@ -46,6 +46,9 @@ CodeEditor = "toga_code_editor.platforms.iOS:CodeEditor"
 [project.entry-points."toga_code_editor.backend.toga_android"]
 CodeEditor = "toga_code_editor.platforms.android:CodeEditor"
 
+[project.entry-points."toga_code_editor.backend.toga_winforms"]
+CodeEditor = "toga_code_editor.platforms.winforms:CodeEditor"
+
 [dependency-groups]
 # Extras used by developers *of* briefcase are pinned to specific versions to
 # ensure environment consistency.
@@ -92,6 +95,7 @@ omit = [
     "*/toga_code_editor/platforms/cocoa.py",
     "*/toga_code_editor/platforms/iOS.py",
     "*/toga_code_editor/platforms/android.py",
+    "*/toga_code_editor/platforms/winforms.py",
 ]
 
 [tool.coverage.paths]

src/toga_code_editor/code_editor.py

@@ -13,7 +13,6 @@
 
 from .highlighting import (
     DEFAULT_THEME,
-    Highlighter,
     NullHighlighter,
     PygmentsHighlighter,
     Theme,
@@ -23,6 +22,19 @@
 """Seconds to wait after the last native edit before re-highlighting."""
 
 
+def _report_rehighlight_failure(task: asyncio.Task) -> None:
+    # Hand a failure to the loop's exception handler as soon as the task finishes.
+    # Otherwise asyncio only reports it when the task object is garbage collected.
+    if not task.cancelled() and (exc := task.exception()) is not None:
+        task.get_loop().call_exception_handler(
+            {
+                "message": "Re-highlighting the code editor failed",
+                "exception": exc,
+                "task": task,
+            }
+        )
+
+
 class CodeEditor(toga.MultilineTextInput):
     def __init__(
         self,
@@ -48,25 +60,25 @@ def __init__(
             user content to display.
         :param on_change: A handler that will be invoked when the value of the widget
             changes.
-        :param language: A Pygments lexer alias such as ``"python"``, or ``None`` for
+        :param language: A Pygments lexer alias such as `"python"`, or `None` for
             no highlighting.
         :param show_line_numbers: Whether to show the line-number gutter.
-        :param theme: A mapping from :class:`TokenKind` to :class:`Style`, or ``None``
+        :param theme: A mapping from :class:`TokenKind` to :class:`Style`, or `None`
             for the default theme.
         :param kwargs: Initial style properties. Unless a font family is given here or
-            on ``style``, the editor uses a monospace font.
+            on `style`, the editor uses a monospace font.
         """
         if "font_family" not in kwargs and (
             style is None or "font_family" not in style
         ):
             kwargs["font_family"] = MONOSPACE
 
-        # State the inherited value setter needs before super().__init__() runs.
-        self._highlighter: Highlighter = NullHighlighter()
-        self._language: str | None = None
-        self._theme: Theme = DEFAULT_THEME
+        # Prime the initial state of the widget.
+        self._language = None
+        self._highlighter = NullHighlighter()
+        self._theme = DEFAULT_THEME
         self._show_line_numbers = True
-        self._pending_rehighlight = None
+        self._pending_rehighlight: asyncio.Task | None = None
 
         super().__init__(
             id=id,
@@ -78,9 +90,9 @@ def __init__(
             **kwargs,
         )
 
+        self.show_line_numbers = show_line_numbers
         self.theme = theme
         self.language = language
-        self.show_line_numbers = show_line_numbers
 
     @cached_property
     def factory(self):
@@ -97,7 +109,8 @@ def factory(self):
             return get_factory("toga_code_editor")
 
     def _create(self) -> Any:
-        return self.factory.CodeEditor(interface=self)
+        impl = self.factory.CodeEditor(interface=self)
+        return impl
 
     @toga.MultilineTextInput.value.setter
     def value(self, value: object) -> None:
@@ -106,23 +119,25 @@ def value(self, value: object) -> None:
 
     @property
     def language(self) -> str | None:
-        """The Pygments lexer alias used for highlighting, or ``None`` for none.
+        """The Pygments lexer alias used for highlighting, or `None` for none.
 
-        Setting an alias Pygments does not know raises :exc:`ValueError` and leaves
-        the previous language in place.
+        :raises ValueError: if an unknown language is specified.
         """
         return self._language
 
     @language.setter
     def language(self, value: str | None) -> None:
-        highlighter = NullHighlighter() if value is None else PygmentsHighlighter(value)
+        # Define the highlighter first - this will raise an error if the
+        # language is not recognized.
+        self._highlighter = (
+            NullHighlighter() if value is None else PygmentsHighlighter(value)
+        )
         self._language = value
-        self._highlighter = highlighter
         self._rehighlight()
 
     @property
     def theme(self) -> Theme:
-        """The mapping from token kind to style; ``None`` restores the default."""
+        """The mapping from token kind to style; `None` restores the default."""
         return self._theme
 
     @theme.setter
@@ -149,14 +164,14 @@ def _schedule_rehighlight(self) -> None:
         """Called by the backend when the user edits the text.
 
         Re-lexing on every keystroke would be wasteful, so wait for a short pause.
-        This is a task rather than a bare ``call_later`` because Toga's Android event
-        loop only arms its next wakeup for work scheduled through ``call_soon``; a
+        This is a task rather than a bare `call_later` because Toga's Android event
+        loop only arms its next wakeup for work scheduled through `call_soon`; a
         timer added from a native callback would otherwise never fire.
         """
         self._cancel_pending_rehighlight()
-        self._pending_rehighlight = toga.App.app.loop.create_task(
-            self._rehighlight_after_delay()
-        )
+        task = toga.App.app.loop.create_task(self._rehighlight_after_delay())
+        task.add_done_callback(_report_rehighlight_failure)
+        self._pending_rehighlight = task
 
     async def _rehighlight_after_delay(self) -> None:
         await asyncio.sleep(REHIGHLIGHT_DELAY)