rules caching (#3880)

* rules caching

* changelog

* docstring

* fix cache

* fix test

* fix test

* remove comment [skip ci]

CHANGELOG.md

@@ -11,6 +11,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Disabled radio buttons could be selected with the keyboard https://github.com/Textualize/textual/issues/3839
 
+## Added
+
+- Added caching of rules attributes and `cache` parameter to Stylesheet.apply https://github.com/Textualize/textual/pull/3880
 
 ## [0.45.1] - 2023-12-12
 

src/textual/app.py

@@ -73,7 +73,7 @@
 from .binding import Binding, BindingType, _Bindings
 from .command import CommandPalette, Provider
 from .css.query import NoMatches
-from .css.stylesheet import Stylesheet
+from .css.stylesheet import RulesMap, Stylesheet
 from .design import ColorSystem
 from .dom import DOMNode
 from .driver import Driver
@@ -2392,6 +2392,7 @@ def _register(
         *widgets: Widget,
         before: int | None = None,
         after: int | None = None,
+        cache: dict[tuple, RulesMap] | None = None,
     ) -> list[Widget]:
         """Register widget(s) so they may receive events.
 
@@ -2400,6 +2401,7 @@ def _register(
             *widgets: The widget(s) to register.
             before: A location to mount before.
             after: A location to mount after.
+            cache: Optional rules map cache.
 
         Returns:
             List of modified widgets.
@@ -2408,6 +2410,8 @@ def _register(
         if not widgets:
             return []
 
+        if cache is None:
+            cache = {}
         widget_list: Iterable[Widget]
         if before is not None or after is not None:
             # There's a before or after, which means there's going to be an
@@ -2424,8 +2428,8 @@ def _register(
             if widget not in self._registry:
                 self._register_child(parent, widget, before, after)
                 if widget._nodes:
-                    self._register(widget, *widget._nodes)
-                apply_stylesheet(widget)
+                    self._register(widget, *widget._nodes, cache=cache)
+                apply_stylesheet(widget, cache=cache)
 
         if not self._running:
             # If the app is not running, prevent awaiting of the widget tasks

src/textual/css/stylesheet.py

@@ -418,6 +418,7 @@ def apply(
         node: DOMNode,
         *,
         animate: bool = False,
+        cache: dict[tuple, RulesMap] | None = None,
     ) -> None:
         """Apply the stylesheet to a DOM node.
 
@@ -428,6 +429,7 @@ def apply(
                 classes modifying the same CSS property), then only the most specific
                 rule will be applied.
             animate: Animate changed rules.
+            cache: An optional cache when applying a group of nodes.
         """
         # Dictionary of rule attribute names e.g. "text_background" to list of tuples.
         # The tuples contain the rule specificity, and the value for that rule.
@@ -437,6 +439,23 @@ def apply(
         rule_attributes: defaultdict[str, list[tuple[Specificity6, object]]]
         rule_attributes = defaultdict(list)
 
+        cache_key: tuple | None
+        if cache is not None:
+            cache_key = (
+                node._parent,
+                node._id,
+                node.classes,
+                node.pseudo_classes,
+                node._css_type_name,
+            )
+            cached_result: RulesMap | None = cache.get(cache_key)
+            if cached_result is not None:
+                self.replace_rules(node, cached_result, animate=animate)
+                self._process_component_classes(node)
+                return
+        else:
+            cache_key = None
+
         _check_rule = self._check_rule
         css_path_nodes = node.css_path_nodes
 
@@ -520,8 +539,18 @@ def apply(
                         rule_value = getattr(_DEFAULT_STYLES, initial_rule_name)
                     node_rules[initial_rule_name] = rule_value  # type: ignore[literal-required]
 
+            if cache is not None:
+                assert cache_key is not None
+                cache[cache_key] = node_rules
             self.replace_rules(node, node_rules, animate=animate)
+        self._process_component_classes(node)
 
+    def _process_component_classes(self, node: DOMNode) -> None:
+        """Process component classes for the given node.
+
+        Args:
+            node: A DOM Node.
+        """
         component_classes = node._get_component_classes()
         if component_classes:
             # Create virtual nodes that exist to extract styles
@@ -628,14 +657,15 @@ def update_nodes(self, nodes: Iterable[DOMNode], animate: bool = False) -> None:
             nodes: Nodes to update.
             animate: Enable CSS animation.
         """
+        cache: dict[tuple, RulesMap] = {}
         apply = self.apply
 
         for node in nodes:
-            apply(node, animate=animate)
+            apply(node, animate=animate, cache=cache)
             if isinstance(node, Widget) and node.is_scrollable:
                 if node.show_vertical_scrollbar:
-                    apply(node.vertical_scrollbar)
+                    apply(node.vertical_scrollbar, cache=cache)
                 if node.show_horizontal_scrollbar:
-                    apply(node.horizontal_scrollbar)
+                    apply(node.horizontal_scrollbar, cache=cache)
                 if node.show_horizontal_scrollbar and node.show_vertical_scrollbar:
-                    apply(node.scrollbar_corner)
+                    apply(node.scrollbar_corner, cache=cache)

src/textual/widgets/_tabs.py

@@ -596,7 +596,7 @@ def animate_underline() -> None:
                     underline.animate("highlight_start", start, duration=0.3)
                     underline.animate("highlight_end", end, duration=0.3)
 
-                self.set_timer(0.01, lambda: self.call_after_refresh(animate_underline))
+                self.set_timer(0.05, animate_underline)
             else:
                 underline.highlight_start = start
                 underline.highlight_end = end