Faster css (#3844)

* faster css

* simplify

* ws

* superfluous function

* simplify selector names, change to set

* changelog

* micro op

* quicken

* Update src/textual/strip.py

Co-authored-by: Rodrigo Girão Serrão <[email protected]>

---------

Co-authored-by: Rodrigo Girão Serrão <[email protected]>

CHANGELOG.md

@@ -15,12 +15,13 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Removed
 
-- Removed renderables/align.py which was no longer used
+- Removed renderables/align.py which was no longer used.
 
 ### Changed
 
 - Dropped ALLOW_CHILDREN flag introduced in 0.43.0 https://github.com/Textualize/textual/pull/3814
 - Widgets with an auto height in an auto height container will now expand if they have no siblings https://github.com/Textualize/textual/pull/3814
+- Breaking change: Removed `limit_rules` from Stylesheet.apply https://github.com/Textualize/textual/pull/3844
 
 ### Added
 

src/textual/app.py

@@ -2246,9 +2246,9 @@ async def invoke_ready_callback() -> None:
 
                     Reactive._initialize_object(self)
 
-                    self.stylesheet.update(self)
+                    self.stylesheet.apply(self)
                     if self.screen is not default_screen:
-                        self.stylesheet.update(default_screen)
+                        self.stylesheet.apply(default_screen)
 
                     await self.animator.start()
 

src/textual/css/model.py

@@ -161,6 +161,7 @@ class RuleSet:
     is_default_rules: bool = False
     tie_breaker: int = 0
     selector_names: set[str] = field(default_factory=set)
+    pseudo_classes: set[str] = field(default_factory=set)
 
     def __hash__(self):
         return id(self)
@@ -205,31 +206,20 @@ def _post_parse(self) -> None:
         type_type = SelectorType.TYPE
         universal_type = SelectorType.UNIVERSAL
 
-        update_selectors = self.selector_names.update
+        add_selector = self.selector_names.add
+        add_pseudo_classes = self.pseudo_classes.update
 
         for selector_set in self.selector_set:
-            update_selectors(
-                "*"
-                for selector in selector_set.selectors
-                if selector.type == universal_type
-            )
-            update_selectors(
-                selector.name
-                for selector in selector_set.selectors
-                if selector.type == type_type
-            )
-            update_selectors(
-                f".{selector.name}"
-                for selector in selector_set.selectors
-                if selector.type == class_type
-            )
-            update_selectors(
-                f"#{selector.name}"
-                for selector in selector_set.selectors
-                if selector.type == id_type
-            )
-            update_selectors(
-                f":{pseudo_class}"
-                for selector in selector_set.selectors
-                for pseudo_class in selector.pseudo_classes
-            )
+            for selector in selector_set.selectors:
+                add_pseudo_classes(selector.pseudo_classes)
+
+            selector = selector_set.selectors[-1]
+            selector_type = selector.type
+            if selector_type == universal_type:
+                add_selector("*")
+            elif selector_type == type_type:
+                add_selector(selector.name)
+            elif selector_type == class_type:
+                add_selector(f".{selector.name}")
+            elif selector_type == id_type:
+                add_selector(f"#{selector.name}")

src/textual/css/styles.py

@@ -757,7 +757,7 @@ def extract_rules(
             A list containing a tuple of <RULE NAME>, <SPECIFICITY> <RULE VALUE>.
         """
         is_important = self.important.__contains__
-        rules = [
+        rules: list[tuple[str, Specificity6, Any]] = [
             (
                 rule_name,
                 (

src/textual/css/stylesheet.py

@@ -335,6 +335,7 @@ def add_source(
             return
         self.source[read_from] = CssSource(css, is_default_css, tie_breaker, scope)
         self._require_parse = True
+        self._rules_map = None
 
     def parse(self) -> None:
         """Parse the source in the stylesheet.
@@ -416,7 +417,6 @@ def apply(
         self,
         node: DOMNode,
         *,
-        limit_rules: set[RuleSet] | None = None,
         animate: bool = False,
     ) -> None:
         """Apply the stylesheet to a DOM node.
@@ -440,15 +440,21 @@ def apply(
         _check_rule = self._check_rule
         css_path_nodes = node.css_path_nodes
 
-        rules: Iterable[RuleSet]
-        if limit_rules is not None:
-            rules = [rule for rule in reversed(self.rules) if rule in limit_rules]
-        else:
-            rules = reversed(self.rules)
+        rules_map = self.rules_map
+
+        # Discard rules which are not applicable early
+        limit_rules = {
+            rule
+            for name in rules_map.keys() & node._selector_names
+            for rule in rules_map[name]
+        }
+        rules = [rule for rule in reversed(self.rules) if rule in limit_rules]
 
         # Collect the rules defined in the stylesheet
-        node._has_hover_style = False
-        node._has_focus_within = False
+        node._has_hover_style = any("hover" in rule.pseudo_classes for rule in rules)
+        node._has_focus_within = any(
+            "focus-within" in rule.pseudo_classes for rule in rules
+        )
 
         # Rules that may be set to the special value `initial`
         initial: set[str] = set()
@@ -458,10 +464,6 @@ def apply(
         for rule in rules:
             is_default_rules = rule.is_default_rules
             tie_breaker = rule.tie_breaker
-            if ":hover" in rule.selector_names:
-                node._has_hover_style = True
-            if ":focus-within" in rule.selector_names:
-                node._has_focus_within = True
             for base_specificity in _check_rule(rule, css_path_nodes):
                 for key, rule_specificity, value in rule.styles.extract_rules(
                     base_specificity, is_default_rules, tie_breaker
@@ -473,52 +475,52 @@ def apply(
                             initial.add(key)
                     rule_attributes[key].append((rule_specificity, value))
 
-        if not rule_attributes:
-            return
-
-        # For each rule declared for this node, keep only the most specific one
-        get_first_item = itemgetter(0)
-        node_rules: RulesMap = cast(
-            RulesMap,
-            {
-                name: max(specificity_rules, key=get_first_item)[1]
-                for name, specificity_rules in rule_attributes.items()
-            },
-        )
+        if rule_attributes:
+            # For each rule declared for this node, keep only the most specific one
+            get_first_item = itemgetter(0)
+            node_rules: RulesMap = cast(
+                RulesMap,
+                {
+                    name: max(specificity_rules, key=get_first_item)[1]
+                    for name, specificity_rules in rule_attributes.items()
+                },
+            )
 
-        # Set initial values
-        for initial_rule_name in initial:
-            # Rules with a value of None should be set to the default value
-            if node_rules[initial_rule_name] is None:  # type: ignore[literal-required]
-                # Exclude non default values
-                # rule[0] is the specificity, rule[0][0] is 0 for default rules
-                default_rules = [
-                    rule
-                    for rule in rule_attributes[initial_rule_name]
-                    if not rule[0][0]
-                ]
-                if default_rules:
-                    # There is a default value
-                    new_value = max(default_rules, key=get_first_item)[1]
-                    node_rules[initial_rule_name] = new_value  # type: ignore[literal-required]
-                else:
-                    # No default value
-                    initial_defaults.add(initial_rule_name)
-
-        # Rules in DEFAULT_CSS set to initial
-        for initial_rule_name in initial_defaults:
-            if node_rules[initial_rule_name] is None:  # type: ignore[literal-required]
-                default_rules = [
-                    rule for rule in rule_attributes[initial_rule_name] if rule[0][0]
-                ]
-                if default_rules:
-                    # There is a default value
-                    rule_value = max(default_rules, key=get_first_item)[1]
-                else:
-                    rule_value = getattr(_DEFAULT_STYLES, initial_rule_name)
-                node_rules[initial_rule_name] = rule_value  # type: ignore[literal-required]
-
-        self.replace_rules(node, node_rules, animate=animate)
+            # Set initial values
+            for initial_rule_name in initial:
+                # Rules with a value of None should be set to the default value
+                if node_rules[initial_rule_name] is None:  # type: ignore[literal-required]
+                    # Exclude non default values
+                    # rule[0] is the specificity, rule[0][0] is 0 for default rules
+                    default_rules = [
+                        rule
+                        for rule in rule_attributes[initial_rule_name]
+                        if not rule[0][0]
+                    ]
+                    if default_rules:
+                        # There is a default value
+                        new_value = max(default_rules, key=get_first_item)[1]
+                        node_rules[initial_rule_name] = new_value  # type: ignore[literal-required]
+                    else:
+                        # No default value
+                        initial_defaults.add(initial_rule_name)
+
+            # Rules in DEFAULT_CSS set to initial
+            for initial_rule_name in initial_defaults:
+                if node_rules[initial_rule_name] is None:  # type: ignore[literal-required]
+                    default_rules = [
+                        rule
+                        for rule in rule_attributes[initial_rule_name]
+                        if rule[0][0]
+                    ]
+                    if default_rules:
+                        # There is a default value
+                        rule_value = max(default_rules, key=get_first_item)[1]
+                    else:
+                        rule_value = getattr(_DEFAULT_STYLES, initial_rule_name)
+                    node_rules[initial_rule_name] = rule_value  # type: ignore[literal-required]
+
+            self.replace_rules(node, node_rules, animate=animate)
 
         component_classes = node._get_component_classes()
         if component_classes:
@@ -634,31 +636,14 @@ def update_nodes(self, nodes: Iterable[DOMNode], animate: bool = False) -> None:
             nodes: Nodes to update.
             animate: Enable CSS animation.
         """
-        rules_map = self.rules_map
         apply = self.apply
 
-        def get_rules(node: DOMNode) -> set[RuleSet]:
-            """Get set of rules for the given node."""
-            return {
-                rule
-                for name in rules_map.keys() & node._selector_names
-                for rule in rules_map[name]
-            }
-
         for node in nodes:
-            rules = get_rules(node)
-            if rules:
-                apply(node, limit_rules=rules, animate=animate)
+            apply(node, animate=animate)
             if isinstance(node, Widget) and node.is_scrollable:
                 if node.show_vertical_scrollbar:
-                    rules = get_rules(node.vertical_scrollbar)
-                    if rules:
-                        apply(node.vertical_scrollbar, limit_rules=rules)
+                    apply(node.vertical_scrollbar)
                 if node.show_horizontal_scrollbar:
-                    rules = get_rules(node.horizontal_scrollbar)
-                    if rules:
-                        apply(node.horizontal_scrollbar, limit_rules=rules)
+                    apply(node.horizontal_scrollbar)
                 if node.show_horizontal_scrollbar and node.show_vertical_scrollbar:
-                    rules = get_rules(node.scrollbar_corner)
-                    if rules:
-                        apply(node.scrollbar_corner, limit_rules=rules)
+                    apply(node.scrollbar_corner)

src/textual/dom.py

@@ -595,20 +595,19 @@ def css_path_nodes(self) -> list[DOMNode]:
         return result[::-1]
 
     @property
-    def _selector_names(self) -> list[str]:
+    def _selector_names(self) -> set[str]:
         """Get a set of selectors applicable to this widget.
 
         Returns:
             Set of selector names.
         """
-        selectors: list[str] = [
+        selectors: set[str] = {
             "*",
             *(f".{class_name}" for class_name in self._classes),
-            *(f":{class_name}" for class_name in self.get_pseudo_classes()),
             *self._css_types,
-        ]
+        }
         if self._id is not None:
-            selectors.append(f"#{self._id}")
+            selectors.add(f"#{self._id}")
         return selectors
 
     @property

src/textual/strip.py

@@ -199,7 +199,7 @@ def join(cls, strips: Iterable[Strip | None]) -> Strip:
         return strip
 
     def __bool__(self) -> bool:
-        return bool(self._segments)
+        return not not self._segments  # faster than bool(...)
 
     def __iter__(self) -> Iterator[Segment]:
         return iter(self._segments)