fix anchor

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
+
+### Fixed
+
+- Fixed infinite loop in `Widget.anchor` https://github.com/Textualize/textual/pull/5290
+
 ## [0.87.1] - 2024-11-24
 
 ## Fixed

src/textual/widget.py

@@ -593,7 +593,7 @@ def opacity(self) -> float:
     @property
     def is_anchored(self) -> bool:
         """Is this widget anchored?"""
-        return self._parent is not None and self._parent is self
+        return isinstance(self._parent, Widget) and self._parent._anchored is self
 
     @property
     def is_mouse_over(self) -> bool:
@@ -4080,9 +4080,7 @@ async def _on_idle(self, event: events.Idle) -> None:
         self._check_refresh()
 
         if self.is_anchored:
-            self.scroll_visible(animate=self._anchor_animate)
-        if self._anchored:
-            self._anchored.scroll_visible(animate=self._anchor_animate)
+            self.scroll_visible(animate=self._anchor_animate, immediate=True)
 
     def _check_refresh(self) -> None:
         """Check if a refresh was requested."""