changelog

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## Unreleased
+
+### Changed
+
+- Added alternative method of composing Widgets
+
 ## [0.11.1] - 2023-02-17
 
 ### Fixed

examples/code_browser.py

@@ -38,10 +38,9 @@ class CodeBrowser(App):
         """Compose our UI."""
         path = "./" if len(sys.argv) < 2 else sys.argv[1]
         yield Header()
-        yield Container(
+        with Container():
-            DirectoryTree(path, id="tree-view"),
+            yield DirectoryTree(path, id="tree-view")
-            Vertical(Static(id="code", expand=True), id="code-view"),
+            yield Vertical(Static(id="code", expand=True), id="code-view")
-        )
         yield Footer()
 
     def on_mount(self, event: events.Mount) -> None:

src/textual/_compose.py

@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from .app import App
+    from .widget import Widget
+
+
+def compose(node: App | Widget) -> list[Widget]:
+    """Compose child widgets.
+
+    Args:
+        node: The parent node.
+
+    Returns:
+        A list of widgets.
+    """
+    app = node.app
+    nodes: list[Widget] = []
+    for child in node.compose():
+        if app._composed:
+            nodes.extend(app._composed)
+            app._composed.clear()
+        if app._compose_stack:
+            app._compose_stack[-1]._nodes._append(child)
+        else:
+            nodes.append(child)
+    if app._composed:
+        nodes.extend(app._composed)
+        app._composed.clear()
+    return nodes

src/textual/app.py

@@ -46,6 +46,7 @@ from ._animator import DEFAULT_EASING, Animatable, Animator, EasingFunction
 from ._ansi_sequences import SYNC_END, SYNC_START
 from ._asyncio import create_task
 from ._callback import invoke
+from ._compose import compose
 from ._context import active_app
 from ._event_broker import NoHandler, extract_handler_actions
 from ._path import _make_path_object_relative
@@ -388,6 +389,9 @@ class App(Generic[ReturnType], DOMNode):
         self._installed_screens: dict[str, Screen | Callable[[], Screen]] = {}
         self._installed_screens.update(**self.SCREENS)
 
+        self._compose_stack: list[Widget] = []
+        self._composed: list[Widget] = []
+
         self.devtools: DevtoolsClient | None = None
         if "devtools" in self.features:
             try:
@@ -1606,7 +1610,7 @@ class App(Generic[ReturnType], DOMNode):
 
     async def _on_compose(self) -> None:
         try:
-            widgets = list(self.compose())
+            widgets = compose(self)
         except TypeError as error:
             raise TypeError(
                 f"{self!r} compose() returned an invalid response; {error}"

src/textual/cli/previews/colors.py

@@ -41,18 +41,16 @@ class ColorsView(Vertical):
         ]
 
         for color_name in ColorSystem.COLOR_NAMES:
-            items: list[Widget] = [Label(f'"{color_name}"')]
+            with ColorGroup(id=f"group-{color_name}"):
-            for level in LEVELS:
+                yield Label(f'"{color_name}"')
-                color = f"{color_name}-{level}" if level else color_name
+                for level in LEVELS:
-                item = ColorItem(
+                    color = f"{color_name}-{level}" if level else color_name
-                    ColorBar(f"${color}", classes="text label"),
+                    yield ColorItem(
-                    ColorBar("$text-muted", classes="muted"),
+                        ColorBar(f"${color}", classes="text label"),
-                    ColorBar("$text-disabled", classes="disabled"),
+                        ColorBar("$text-muted", classes="muted"),
-                    classes=color,
+                        ColorBar("$text-disabled", classes="disabled"),
-                )
+                        classes=color,
-                items.append(item)
+                    )
-
-            yield ColorGroup(*items, id=f"group-{color_name}")
 
 
 class ColorsApp(App):

src/textual/cli/previews/easing.py

@@ -73,16 +73,15 @@ class EasingApp(App):
         )
 
         yield EasingButtons()
-        yield Vertical(
+        with Vertical():
-            Horizontal(
+            yield Horizontal(
                 Label("Animation Duration:", id="label"), duration_input, id="inputs"
-            ),
+            )
-            Horizontal(
+            yield Horizontal(
                 self.animated_bar,
                 Container(self.opacity_widget, id="other"),
-            ),
+            )
-            Footer(),
+            yield Footer()
-        )
 
     def on_button_pressed(self, event: Button.Pressed) -> None:
         self.bell()

src/textual/dom.py

@@ -134,6 +134,7 @@ class DOMNode(MessagePump):
         self._classes.update(_classes)
 
         self._nodes: NodeList = NodeList()
+        self._composing: bool = False
         self._css_styles: Styles = Styles(self)
         self._inline_styles: Styles = Styles(self)
         self.styles: RenderStyles = RenderStyles(

src/textual/widget.py

@@ -5,6 +5,7 @@ from collections import Counter
 from fractions import Fraction
 from itertools import islice
 from operator import attrgetter
+from types import TracebackType
 from typing import (
     TYPE_CHECKING,
     ClassVar,
@@ -38,6 +39,7 @@ from . import errors, events, messages
 from ._animator import DEFAULT_EASING, Animatable, BoundAnimator, EasingFunction
 from ._arrange import DockArrangeResult, arrange
 from ._asyncio import create_task
+from ._compose import compose
 from ._context import active_app
 from ._easing import DEFAULT_SCROLL_EASING
 from ._layout import Layout
@@ -363,6 +365,22 @@ class Widget(DOMNode):
     def offset(self, offset: Offset) -> None:
         self.styles.offset = ScalarOffset.from_offset(offset)
 
+    def __enter__(self) -> None:
+        self.app._compose_stack.append(self)
+
+    def __exit__(
+        self,
+        exc_type: type[BaseException] | None,
+        exc_val: BaseException | None,
+        exc_tb: TracebackType | None,
+    ) -> None:
+        compose_stack = self.app._compose_stack
+        composed = compose_stack.pop()
+        if compose_stack:
+            compose_stack[-1]._nodes._append(composed)
+        else:
+            self.app._composed.append(composed)
+
     ExpectType = TypeVar("ExpectType", bound="Widget")
 
     @overload
@@ -2444,7 +2462,7 @@ class Widget(DOMNode):
 
     async def _on_compose(self) -> None:
         try:
-            widgets = list(self.compose())
+            widgets = compose(self)
         except TypeError as error:
             raise TypeError(
                 f"{self!r} compose() returned an invalid response; {error}"