fix for virtual nodes css

src/textual/css/stylesheet.py

@@ -28,6 +28,25 @@ from .tokenizer import TokenError
 from .types import Specificity3, Specificity6
 
 
+class _VirtualDOMNode(DOMNode):
+    """A DOM node that exists only to gether styles."""
+
+    def __init__(
+        self,
+        parent: DOMNode,
+        *,
+        name: str | None = None,
+        id: str | None = None,
+        classes: str | None = None,
+    ) -> None:
+        self._virtual_parent = parent
+        super().__init__(name=name, id=id, classes=classes)
+
+    def refresh(self, *, repaint: bool = True, layout: bool = False) -> None:
+        """Pass the refresh up to the parent, because this object will not exist during render."""
+        self._virtual_parent.refresh(repaint=repaint, layout=layout)
+
+
 class StylesheetParseError(StylesheetError):
     def __init__(self, errors: StylesheetErrors) -> None:
         self.errors = errors
@@ -408,7 +427,7 @@ class Stylesheet:
 
         node._component_styles.clear()
         for component in node._get_component_classes():
-            virtual_node = DOMNode(classes=component)
+            virtual_node = _VirtualDOMNode(node, classes=component)
             virtual_node._attach(node)
             self.apply(virtual_node, animate=False)
             node._component_styles[component] = virtual_node.styles

src/textual/dom.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import re
+from functools import cache
 from inspect import getfile
 from typing import (
     TYPE_CHECKING,
@@ -314,7 +315,9 @@ class DOMNode(MessagePump):
 
         return css_stack
 
-    def _get_component_classes(self) -> set[str]:
+    @classmethod
+    @cache
+    def _get_component_classes(cls) -> set[str]:
         """Gets the component classes for this class and inherited from bases.
 
         Component classes are inherited from base classes, unless
@@ -323,14 +326,13 @@ class DOMNode(MessagePump):
         Returns:
             A set with all the component classes available.
         """
-
         component_classes: set[str] = set()
-        for base in self._node_bases:
+        for base in cls._css_bases(cls):
             component_classes.update(base.__dict__.get("COMPONENT_CLASSES", set()))
             if not base.__dict__.get("_inherit_component_classes", True):
                 break
 
-        return component_classes
+        return frozenset(component_classes)
 
     @property
     def parent(self) -> DOMNode | None: