CI runs the tests again, and the 19 they hid are fixed (4 were real bugs)

.github/workflows/pythonpackage.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.12", "3.13", "3.14"]
     defaults:
       run:
         shell: bash
@@ -35,18 +35,9 @@ jobs:
           cache: "poetry"
       - name: Install dependencies
         run: poetry install --no-interaction --extras syntax
-        if: ${{ matrix.python-version != '3.9' }}
-      - name: Install dependencies for 3.9
-        run: poetry install --no-interaction
-        if: ${{ matrix.python-version == '3.9' }}
-      - name: Test with pytest (Py310+ - with syntax highlighting)
+      - name: Test with pytest
         run: |
           poetry run pytest tests -v --cov=./src/textual --cov-report=xml:./coverage.xml --cov-report term-missing
-        if: ${{ matrix.python-version != '3.9' }}
-      - name: Test with pytest (Py39 - without syntax highlighting)
-        run: |
-          poetry run pytest tests -v --cov=./src/textual --cov-report=xml:./coverage.xml --cov-report term-missing -m 'not syntax'
-        if: ${{ matrix.python-version == '3.9' }}
       - name: Upload snapshot report
         if: always()
         uses: actions/upload-artifact@v4

docs/examples/guide/widgets/checker01.py

@@ -4,12 +4,13 @@
 from textual.app import App, ComposeResult
 from textual.strip import Strip
 from textual.widget import Widget
+from textual._paint_state import PaintState
 
 
 class CheckerBoard(Widget):
     """Render an 8x8 checkerboard."""
 
-    def render_line(self, y: int) -> Strip:
+    def render_line(self, y: int, paint: PaintState) -> Strip:
         """Render a line of the widget. y is relative to the top of the widget."""
 
         row_index = y // 4  # A checkerboard square consists of 4 rows

docs/examples/guide/widgets/checker02.py

@@ -3,6 +3,7 @@
 from textual.app import App, ComposeResult
 from textual.strip import Strip
 from textual.widget import Widget
+from textual._paint_state import PaintState
 
 
 class CheckerBoard(Widget):
@@ -22,7 +23,7 @@ class CheckerBoard(Widget):
     }
     """
 
-    def render_line(self, y: int) -> Strip:
+    def render_line(self, y: int, paint: PaintState) -> Strip:
         """Render a line of the widget. y is relative to the top of the widget."""
 
         row_index = y // 4  # four lines per row

docs/examples/guide/widgets/checker03.py

@@ -6,6 +6,7 @@
 from textual.scroll_view import ScrollView
 
 from rich.segment import Segment
+from textual._paint_state import PaintState
 
 
 class CheckerBoard(ScrollView):
@@ -29,7 +30,7 @@ def __init__(self, board_size: int) -> None:
         # Each square is 4 rows and 8 columns
         self.virtual_size = Size(board_size * 8, board_size * 4)
 
-    def render_line(self, y: int) -> Strip:
+    def render_line(self, y: int, paint: PaintState) -> Strip:
         """Render a line of the widget. y is relative to the top of the widget."""
 
         scroll_x, scroll_y = self.scroll_offset  # The current scroll position

docs/examples/guide/widgets/checker04.py

@@ -9,6 +9,7 @@
 
 from rich.segment import Segment
 from rich.style import Style
+from textual._paint_state import PaintState
 
 
 class CheckerBoard(ScrollView):
@@ -62,7 +63,7 @@ def get_square_region(square_offset: Offset) -> Region:
         # Refresh the new cursor square
         self.refresh(get_square_region(cursor_square))
 
-    def render_line(self, y: int) -> Strip:
+    def render_line(self, y: int, paint: PaintState) -> Strip:
         """Render a line of the widget. y is relative to the top of the widget."""
 
         scroll_x, scroll_y = self.scroll_offset  # The current scroll position

docs/guide/widgets.md

@@ -404,7 +404,7 @@ Textual offers an alternative API which reduces the amount of work required to r
 
 ### Render Line method
 
-To build a widget with the line API, implement a `render_line` method rather than a `render` method. The `render_line` method takes a single integer argument `y` which is an offset from the top of the widget, and should return a [Strip][textual.strip.Strip] object containing that line's content.
+To build a widget with the line API, implement a `render_line` method rather than a `render` method. The `render_line` method takes an integer `y`, which is an offset from the top of the widget, and the widget's resolved `paint` state (its colors, text style and opacity for this frame), and should return a [Strip][textual.strip.Strip] object containing that line's content.
 Textual will call this method as required to get content for every row of characters in the widget.
 
 <div class="excalidraw">

src/textual/_compositor.py

@@ -412,9 +412,20 @@ def _spatial_map(self) -> SpatialMap[tuple[int, Widget]]:
         )
         return spatial_map
 
-    @abstractmethod
     def matches(self, key: SubtreeGeometryKey, *, require_complete: bool = False) -> bool:
-        ...
+        """The same arrangement, or a complete one serving a viewport request."""
+        if require_complete and not self.complete:
+            return False
+        mine, wanted = self._comparable(self.key), self._comparable(key)
+        return mine == wanted or (
+            not mine.visible_only and wanted.visible_only
+            and mine._replace(visible_only=True) == wanted
+        )
+
+    @staticmethod
+    @abstractmethod
+    def _comparable(key: SubtreeGeometryKey) -> SubtreeGeometryKey:
+        """The inputs this resource's placements depend on."""
 
     def restore_into(
         self, geometry: CompositorMap, widgets: set[Widget], invisible_widgets: set[Widget],
@@ -515,13 +526,9 @@ def references_retired(self, owner: Widget, retired: set[Widget]) -> bool:
 class PlacedSubtreeGeometry(SubtreeGeometry[MapGeometry]):
     """A culled or screen-dependent arrangement keeps its exact placement."""
 
-    def matches(self, key: SubtreeGeometryKey, *, require_complete: bool = False) -> bool:
-        if require_complete and not self.complete:
-            return False
-        return self.key == key or (
-            not self.key.visible_only and key.visible_only
-            and self.key._replace(visible_only=True) == key
-        )
+    @staticmethod
+    def _comparable(key: SubtreeGeometryKey) -> SubtreeGeometryKey:
+        return key
 
     def _project_entry(self, entry: MapGeometry, key: SubtreeGeometryKey,
                        clip: SceneClip, *, root: bool) -> tuple[MapGeometry, SceneClip]:
@@ -560,10 +567,9 @@ def capture(cls, key, geometry, widgets, invisible_widgets, clips, clip, screen_
         return super().capture(key, intrinsic, widgets, invisible_widgets,
                                clips, clip, screen_coordinates)
 
-    def matches(self, key: SubtreeGeometryKey, *, require_complete: bool = False) -> bool:
-        if require_complete and not self.complete:
-            return False
-        return self.key.intrinsic() == key.intrinsic()
+    @staticmethod
+    def _comparable(key: SubtreeGeometryKey) -> SubtreeGeometryKey:
+        return key.intrinsic()
 
     def _project_entry(self, entry: SubtreeMapGeometry, key: SubtreeGeometryKey,
                        clip: SceneClip, *, root: bool) -> tuple[MapGeometry, SceneClip]:

src/textual/app.py

@@ -2940,6 +2940,10 @@ def _load_screen_css(self, screen: Screen):
         if update:
             self.stylesheet.reparse()
             self.stylesheet.update(self)
+            # The screen was mounted, and styled, before its own CSS was read,
+            # and a pushed screen is not on a stack yet for the source change to
+            # queue it: this screen is the one the new rules are for.
+            self.stylesheet.update(screen)
 
     async def _replace_screen(self, screen: Screen) -> Screen:
         """Handle the replaced screen.
@@ -3649,13 +3653,16 @@ async def _on_compose(self) -> None:
         _rich_traceback_omit = True
         self._compose_screen = self.screen
         try:
-            widgets = [*self.screen._nodes, *await compose_async(self)]
+            widgets = await compose_async(self)
         except TypeError as error:
             raise TypeError(
                 f"{self!r} compose() method returned an invalid result; {error}"
             ) from error
 
-        await self.mount_all(widgets)
+        # The screen's own widgets (tooltip, toasts) are already mounted. The
+        # app's widgets go in front of them, so the app's queries, such as
+        # query_one(Static) in on_mount, find its own widgets first.
+        await self.mount_all(widgets, before=0 if self.screen._nodes else None)
         # The screen resumed before these widgets existed, so its own
         # auto-focus pass found nothing to focus.
         self._compose_screen._update_auto_focus()

src/textual/binding.py

@@ -128,9 +128,18 @@ def command_invocations(self) -> tuple[KeyInvocation, ...]:
     def invocations(self) -> tuple[KeyInvocation, ...]:
         return self.declared_key.invocations(self.command_invocations())
 
+    def shared_identity(self, mode: type[EditingMode]) -> str | None:
+        """The arrow preference this binding's key shares in the mode, if its key is an arrow."""
+        return next((invocation.binding_identity(mode) for invocation in self.invocations()), self.id)
+
+    def preference_identity(self, mode: type[EditingMode]) -> str | None:
+        """A named action keeps the id its author declared; without one it joins its arrow's
+        shared preference, so a keymap for that id replaces every key the author listed."""
+        return self.id if self.id is not None else self.shared_identity(mode)
+
     def for_mode(self, mode: type[EditingMode]) -> tuple[Self, ...]:
         """Give native arrows their shared preference identity in the actual mode."""
-        identity = next((invocation.binding_identity(mode) for invocation in self.invocations()), self.id)
+        identity = self.preference_identity(mode)
         return tuple(
             dataclasses.replace(self, key=spelling, id=identity)
             for spelling in self.declared_key.spellings(mode, self.key)
@@ -293,6 +302,10 @@ def invocation(self) -> KeyInvocation:
     def command_invocations(self) -> tuple[KeyInvocation, ...]:
         return (self.invocation,)
 
+    def preference_identity(self, mode: type[EditingMode]) -> str | None:
+        """Native commands on an arrow always share its preference, whatever id they carry."""
+        return self.shared_identity(mode)
+
     def key_identity(self) -> str:
         return self.qualified(self.action)
 

src/textual/containers.py

@@ -7,6 +7,7 @@
 
 from __future__ import annotations
 
+from textual.layouts.vertical import VerticalLayout
 from textual.layout import Layout
 from textual.navigation import ScrollCommand
 from textual.layouts.grid import GridLayout
@@ -18,6 +19,8 @@
 class Container(Widget):
     """Simple container widget, with vertical layout."""
 
+    DEFAULT_LAYOUT = VerticalLayout
+
     DEFAULT_CSS = """
     Container {
         width: 1fr;
@@ -30,6 +33,8 @@ class Container(Widget):
 class ScrollableContainer(Widget, can_focus=True, key_families=(ScrollCommand,)):
     """A scrollable container with vertical layout, and auto scrollbars on both axis."""
 
+    DEFAULT_LAYOUT = VerticalLayout
+
     # We don't typically want to maximize scrollable containers,
     # since the user can easily navigate the contents
     ALLOW_MAXIMIZE = False
@@ -90,6 +95,8 @@ def allow_maximize(self) -> bool:
 class Vertical(Widget):
     """An expanding container with vertical layout and no scrollbars."""
 
+    DEFAULT_LAYOUT = VerticalLayout
+
     DEFAULT_CSS = """
     Vertical {
         width: 1fr;
@@ -102,6 +109,8 @@ class Vertical(Widget):
 class VerticalGroup(Widget):
     """A non-expanding container with vertical layout and no scrollbars."""
 
+    DEFAULT_LAYOUT = VerticalLayout
+
     DEFAULT_CSS = """
     VerticalGroup {
         width: 1fr;
@@ -166,6 +175,8 @@ class HorizontalScroll(ScrollableContainer):
 class Center(Widget):
     """A container which aligns children on the X axis."""
 
+    DEFAULT_LAYOUT = VerticalLayout
+
     DEFAULT_CSS = """
     Center {
         align-horizontal: center;
@@ -178,6 +189,8 @@ class Center(Widget):
 class Right(Widget):
     """A container which aligns children on the X axis."""
 
+    DEFAULT_LAYOUT = VerticalLayout
+
     DEFAULT_CSS = """
     Right {
         align-horizontal: right;
@@ -190,6 +203,8 @@ class Right(Widget):
 class Middle(Widget):
     """A container which aligns children on the Y axis."""
 
+    DEFAULT_LAYOUT = VerticalLayout
+
     DEFAULT_CSS = """
     Middle {
         align-vertical: middle;
@@ -202,6 +217,8 @@ class Middle(Widget):
 class CenterMiddle(Widget):
     """A container which aligns its children on both axis."""
 
+    DEFAULT_LAYOUT = VerticalLayout
+
     DEFAULT_CSS = """
     CenterMiddle {
         align: center middle;

src/textual/css/_style_properties.py

@@ -86,8 +86,15 @@ def __get__(self, obj: None, objtype: type[StylesBase] | None = None) -> Self: .
     def __get__(self, obj: StylesBase, objtype: type[StylesBase] | None = None) -> PropertyGetType: ...
 
     def __get__(self, obj: StylesBase | None, objtype: type[StylesBase] | None = None):
-        """Read the rule, or the declared default when it is unset."""
-        return self if obj is None else obj.get_rule(self.name, self.default)
+        """Read the rule, or the declared default when it is unset or `initial`.
+
+        The builder stores `initial` as None so it still overrides less specific
+        rules; reading it answers the default, never None.
+        """
+        if obj is None:
+            return self
+        value = obj.get_rule(self.name)
+        return self.default if value is None else value
 
     def __set_name__(self, owner: type[StylesBase], name: str) -> None:
         self.name = name

src/textual/dom.py

@@ -352,7 +352,7 @@ def _render_container(self):
         """Native container paint, shared independently of scene custody."""
         from textual.renderables.blank import Blank
 
-        if self.geometry.child_layout and self.geometry.keyline[0] != "none":
+        if self.is_container and self.geometry.keyline[0] != "none":
             return self.layout.render_keyline(self)
         return Blank(self.background_colors[1])
 

src/textual/layout.py

@@ -259,6 +259,8 @@ class Layout(ABC):
     """Base class of the object responsible for arranging Widgets within a container."""
 
     name: ClassVar[str] = ""
+    holds_children: ClassVar[bool] = True
+    """A declared layout makes its widget a container, with or without children."""
     _content_width_dependency: ClassVar[HeightDependency]
     _content_height_dependency: ClassVar[HeightDependency]
     _arrangement_height_dependency: ClassVar[HeightDependency]