pause gc on scroll

CHANGELOG.md

@@ -5,6 +5,17 @@ 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/).
 
+## [8.1.0] - 2026-03-09 
+
+### Changed
+
+- Replace circuar references in DOM with weak references to improve GC times https://github.com/Textualize/textual/pull/6410
+- When animating an attribute a second time, the original `on_complete` is now called https://github.com/Textualize/textual/pull/6410
+
+### Added
+
+- Added experimental `App.PAUSE_GC_ON_SCROLL_` boolean (disabled by default) https://github.com/Textualize/textual/pull/6410
+
 ## [8.0.2] - 2026-03-03
 
 ### Changed
@@ -3370,6 +3381,7 @@ https://textual.textualize.io/blog/2022/11/08/version-040/#version-040
 - New handler system for messages that doesn't require inheritance
 - Improved traceback handling
 
+[8.1.0]: https://github.com/Textualize/textual/compare/v8.0.2...v8.1.0
 [8.0.2]: https://github.com/Textualize/textual/compare/v8.0.1...v8.0.2
 [8.0.1]: https://github.com/Textualize/textual/compare/v8.0.0...v8.0.1
 [8.0.0]: https://github.com/Textualize/textual/compare/v7.5.0...v8.0.0

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "textual"
-version = "8.0.2"
+version = "8.1.0"
 homepage = "https://github.com/Textualize/textual"
 repository = "https://github.com/Textualize/textual"
 documentation = "https://textual.textualize.io/"

src/textual/_animator.py

@@ -421,9 +421,10 @@ def _animate(
                 )
 
             start_value = getattr(obj, attribute)
-
             if start_value == value:
                 self._animations.pop(animation_key, None)
+                if on_complete is not None:
+                    self.app.call_later(on_complete)
                 return
 
             if duration is not None:
@@ -455,9 +456,12 @@ def _animate(
 
         assert animation is not None, "animation expected to be non-None"
 
-        current_animation = self._animations.get(animation_key)
-        if current_animation is not None and current_animation == animation:
-            return
+        if (current_animation := self._animations.get(animation_key)) is not None:
+            if (on_complete := current_animation.on_complete) is not None:
+                on_complete()
+                self._animations.pop(animation_key)
+            if current_animation == animation:
+                return
 
         self._animations[animation_key] = animation
         self._timer.resume()

src/textual/app.py

@@ -493,7 +493,7 @@ class MyApp(App[None]):
 
     A breakpoint consists of a tuple containing the minimum width where the class should applied, and the name of the class to set.
 
-    Note that only one class name is set, and if you should avoid having more than one breakpoint set for the same size.
+    Note that only one class name is set, and you should avoid having more than one breakpoint set for the same size.
 
     Example:
         ```python
@@ -510,6 +510,10 @@ class MyApp(App[None]):
     Contents are the same as [`HORIZONTAL_BREAKPOINTS`][textual.app.App.HORIZONTAL_BREAKPOINTS], but the integer is compared to the height, rather than the width.
     """
 
+    # TODO: Enable by default after suitable testing period
+    PAUSE_GC_ON_SCROLL: ClassVar[bool] = False
+    """Pause Python GC (Garbage Collection) when scrolling, for potentially smoother scrolling with many widgets (experimental)."""
+
     _PSEUDO_CLASSES: ClassVar[dict[str, Callable[[App[Any]], bool]]] = {
         "focus": lambda app: app.app_focus,
         "blur": lambda app: not app.app_focus,
@@ -838,6 +842,9 @@ def __init__(
         self._compose_screen: Screen | None = None
         """The screen composed by App.compose."""
 
+        self._realtime_animation_count = 0
+        """Number of current realtime animations, such as scrolling."""
+
         if self.ENABLE_COMMAND_PALETTE:
             for _key, binding in self._bindings:
                 if binding.action in {"command_palette", "app.command_palette"}:
@@ -984,6 +991,22 @@ def clipboard(self) -> str:
         """
         return self._clipboard
 
+    def _realtime_animation_begin(self) -> None:
+        """A scroll or other animation that must be smooth has begun."""
+        if self.PAUSE_GC_ON_SCROLL:
+            import gc
+
+            gc.disable()
+        self._realtime_animation_count += 1
+
+    def _realtime_animation_complete(self) -> None:
+        """A scroll or other animation that must be smooth has completed."""
+        self._realtime_animation_count -= 1
+        if self._realtime_animation_count == 0 and self.PAUSE_GC_ON_SCROLL:
+            import gc
+
+            gc.enable()
+
     def format_title(self, title: str, sub_title: str) -> Content:
         """Format the title for display.
 

src/textual/message_pump.py

@@ -27,7 +27,7 @@
     TypeVar,
     cast,
 )
-from weakref import WeakSet
+from weakref import WeakSet, ref
 
 from textual import Logger, events, log, messages
 from textual._callback import invoke
@@ -143,6 +143,15 @@ def __init__(self, parent: MessagePump | None = None) -> None:
 
         """
 
+    @property
+    def _parent(self) -> MessagePump | None:
+        """The current parent message pump (if set)."""
+        return None if self.__parent is None else self.__parent()
+
+    @_parent.setter
+    def _parent(self, parent: MessagePump | None) -> None:
+        self.__parent = None if parent is None else ref(parent)
+
     @cached_property
     def _message_queue(self) -> Queue[Message | None]:
         return Queue()

src/textual/scrollbar.py

@@ -360,13 +360,15 @@ async def _on_mouse_up(self, event: events.MouseUp) -> None:
         event.stop()
 
     def _on_mouse_capture(self, event: events.MouseCapture) -> None:
+        self.app._realtime_animation_begin()
         self.styles.pointer = "grabbing"
         if isinstance(self._parent, Widget):
             self._parent.release_anchor()
         self.grabbed = event.mouse_position
         self.grabbed_position = self.position
 
     def _on_mouse_release(self, event: events.MouseRelease) -> None:
+        self.app._realtime_animation_complete()
         self.styles.pointer = "default"
         self.grabbed = None
         if self.vertical and isinstance(self.parent, Widget):

src/textual/widget.py

@@ -2722,6 +2722,7 @@ def _scroll_to(
 
         def _animate_on_complete() -> None:
             """set last scroll time, and invoke callback."""
+            self.app._realtime_animation_complete()
             self._last_scroll_time = monotonic()
             if on_complete is not None:
                 self.call_next(on_complete)
@@ -2738,6 +2739,7 @@ def _animate_on_complete() -> None:
                 assert x is not None
                 self.scroll_target_x = x
                 if x != self.scroll_x:
+                    self.app._realtime_animation_begin()
                     self.animate(
                         "scroll_x",
                         self.scroll_target_x,
@@ -2752,6 +2754,7 @@ def _animate_on_complete() -> None:
                 assert y is not None
                 self.scroll_target_y = y
                 if y != self.scroll_y:
+                    self.app._realtime_animation_begin()
                     self.animate(
                         "scroll_y",
                         self.scroll_target_y,

tests/test_animation.py

@@ -211,3 +211,36 @@ async def test_cancel_widget_non_animation() -> None:
         assert not pilot.app.animator.is_being_animated(widget, "counter")
         await widget.stop_animation("counter")
         assert not pilot.app.animator.is_being_animated(widget, "counter")
+
+
+async def test_double_animation_on_complete() -> None:
+    """Test that animating an attribute a second time, fires its `on_complete` callback."""
+
+    complete_count = 0
+
+    class AnimApp(App):
+        x = var(0)
+
+        def on_key(self) -> None:
+
+            def on_complete() -> None:
+                nonlocal complete_count
+                complete_count += 1
+
+            self.animator.animate(
+                self,
+                "x",
+                100 + complete_count,
+                duration=0.1,
+                on_complete=on_complete,
+            )
+
+    app = AnimApp()
+    async with app.run_test() as pilot:
+        # Press space twice to initiate 2 animations
+        await pilot.press("space")
+        await pilot.press("space")
+        # Wait for animations to complete
+        await pilot.wait_for_animation()
+        # Check that on_complete callback was invoked twice
+        assert complete_count == 2

tests/test_arrange.py

@@ -1,6 +1,7 @@
 import pytest
 
 from textual._arrange import TOP_Z, arrange
+from textual._context import active_app
 from textual.app import App
 from textual.geometry import NULL_OFFSET, Region, Size, Spacing
 from textual.layout import WidgetPlacement
@@ -17,7 +18,9 @@ async def test_arrange_empty():
 
 async def test_arrange_dock_top():
     container = Widget(id="container")
-    container._parent = App()
+    app = App()
+    active_app.set(app)
+    container._parent = app
     child = Widget(id="child")
     header = Widget(id="header")
     header.styles.dock = "top"
@@ -63,7 +66,9 @@ async def test_arrange_dock_left():
 
 async def test_arrange_dock_right():
     container = Widget(id="container")
-    container._parent = App()
+    app = App()
+    active_app.set(app)
+    container._parent = app
     child = Widget(id="child")
     header = Widget(id="header")
     header.styles.dock = "right"
@@ -88,7 +93,9 @@ async def test_arrange_dock_right():
 
 async def test_arrange_dock_bottom():
     container = Widget(id="container")
-    container._parent = App()
+    app = App()
+    active_app.set(app)
+    container._parent = app
     child = Widget(id="child")
     header = Widget(id="header")
     header.styles.dock = "bottom"