From 9a1cd48532322bbbe26990979abfa396a126c5ff Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Thu, 25 Aug 2022 11:06:24 +0100
Subject: [PATCH 01/13] visible widgets

---
 src/textual/_compositor.py    | 17 ++++++++++++++++-
 src/textual/app.py            |  4 ++++
 src/textual/css/stylesheet.py | 18 ++++++++++++++++--
 src/textual/screen.py         | 10 ++++++++++
 src/textual/widget.py         |  2 +-
 5 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/src/textual/_compositor.py b/src/textual/_compositor.py
index 3fab34aeb..f7c5ae757 100644
--- a/src/textual/_compositor.py
+++ b/src/textual/_compositor.py
@@ -183,6 +183,8 @@ class Compositor:
         # Note this may be a superset of self.map.keys() as some widgets may be invisible for various reasons
         self.widgets: set[Widget] = set()
 
+        self._visible_widgets: set[Widget] | None = set()
+
         # The top level widget
         self.root: Widget | None = None
 
@@ -269,6 +271,7 @@ class Compositor:
         # Replace map and widgets
         self.map = map
         self.widgets = widgets
+        self._visible_widgets = None
 
         # Get a map of regions
         self.regions = {
@@ -305,6 +308,17 @@ class Compositor:
             resized=resized_widgets,
         )
 
+    @property
+    def visible_widgets(self) -> set[Widget]:
+        if self._visible_widgets is None:
+            in_screen = self.size.region.__contains__
+            self._visible_widgets = {
+                widget
+                for widget, (region, clip) in self.regions.items()
+                if in_screen(region)
+            }
+        return self._visible_widgets
+
     def _arrange_root(
         self, root: Widget, size: Size
     ) -> tuple[CompositorMap, set[Widget]]:
@@ -467,8 +481,9 @@ class Compositor:
         """Get the widget under the given point or None."""
         # TODO: Optimize with some line based lookup
         contains = Region.contains
+        is_visible = self.visible_widgets.__contains__
         for widget, cropped_region, region, *_ in self:
-            if contains(cropped_region, x, y):
+            if is_visible(widget) and contains(cropped_region, x, y):
                 return widget, region
         raise errors.NoWidget(f"No widget under screen coordinate ({x}, {y})")
 
diff --git a/src/textual/app.py b/src/textual/app.py
index f564ae148..022ac2519 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -723,6 +723,10 @@ class App(Generic[ReturnType], DOMNode):
         self._require_stylesheet_update = True
         self.check_idle()
 
+    def update_visible_styles(self) -> None:
+        """Update visible styles only."""
+        self.stylesheet.update_nodes(self.screen.visible_widgets)
+
     def mount(self, *anon_widgets: Widget, **widgets: Widget) -> None:
         """Mount widgets. Widgets specified as positional args, or keywords args. If supplied
         as keyword args they will be assigned an id of the key.
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index 0ea08020c..834a154c8 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -434,9 +434,23 @@ class Stylesheet:
         node.post_message_no_wait(messages.StylesUpdated(sender=node))
 
     def update(self, root: DOMNode, animate: bool = False) -> None:
-        """Update a node and its children."""
+        """Update styles on node and its children.
+
+        Args:
+            root (DOMNode): Root note to update.
+            animate (bool, optional): Enable CSS animation. Defaults to False.
+        """
+        self.update_nodes(root.walk_children())
+
+    def update_nodes(self, nodes: Iterable[DOMNode], animate: bool = False) -> None:
+        """Update styles for nodes.
+
+        Args:
+            nodes (DOMNode): Nodes to update.
+            animate (bool, optional): Enable CSS animation. Defaults to False.
+        """
         apply = self.apply
-        for node in root.walk_children():
+        for node in nodes:
             apply(node, animate=animate)
             if isinstance(node, Widget) and node.is_scrollable:
                 if node.show_vertical_scrollbar:
diff --git a/src/textual/screen.py b/src/textual/screen.py
index 2cbd12440..c8e886d6e 100644
--- a/src/textual/screen.py
+++ b/src/textual/screen.py
@@ -63,6 +63,16 @@ class Screen(Widget):
             )
         return self._update_timer
 
+    @property
+    def widgets(self) -> list[Widget]:
+        """Get visible widgets."""
+        return list(self._compositor.map.keys())
+
+    @property
+    def visible_widgets(self) -> list[Widget]:
+        """Get visible widgets."""
+        return list(self._compositor.visible_widgets)
+
     def watch_dark(self, dark: bool) -> None:
         pass
 
diff --git a/src/textual/widget.py b/src/textual/widget.py
index 4c23063c0..acad9105f 100644
--- a/src/textual/widget.py
+++ b/src/textual/widget.py
@@ -1225,7 +1225,7 @@ class Widget(DOMNode):
 
     def watch_mouse_over(self, value: bool) -> None:
         """Update from CSS if mouse over state changes."""
-        self.app.update_styles()
+        self.app.update_visible_styles()
 
     def watch_has_focus(self, value: bool) -> None:
         """Update from CSS if has focus state changes."""

From 9b8b4db02f93928ce924989367166da71dd43a16 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Thu, 25 Aug 2022 11:20:04 +0100
Subject: [PATCH 02/13] update self

---
 src/textual/dom.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/textual/dom.py b/src/textual/dom.py
index 86a509858..dc8d124b2 100644
--- a/src/textual/dom.py
+++ b/src/textual/dom.py
@@ -699,7 +699,7 @@ class DOMNode(MessagePump):
         if old_classes == self._classes:
             return
         try:
-            self.app.stylesheet.update(self.app, animate=True)
+            self.app.stylesheet.update(self, animate=True)
         except NoActiveAppError:
             pass
 
@@ -715,7 +715,7 @@ class DOMNode(MessagePump):
         if old_classes == self._classes:
             return
         try:
-            self.app.stylesheet.update(self.app, animate=True)
+            self.app.stylesheet.update(self, animate=True)
         except NoActiveAppError:
             pass
 
@@ -731,7 +731,7 @@ class DOMNode(MessagePump):
         if old_classes == self._classes:
             return
         try:
-            self.app.stylesheet.update(self.app, animate=True)
+            self.app.stylesheet.update(self, animate=True)
         except NoActiveAppError:
             pass
 

From 9960bd139a16af7cdec6323923c29e5908e52c7b Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Thu, 25 Aug 2022 11:58:05 +0100
Subject: [PATCH 03/13] narrow updates

---
 src/textual/app.py            |  9 ++++++---
 src/textual/css/stylesheet.py | 10 ++++++++--
 src/textual/widget.py         |  4 ++--
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/textual/app.py b/src/textual/app.py
index 022ac2519..b1a99b0ff 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -714,14 +714,17 @@ class App(Generic[ReturnType], DOMNode):
         """
         return self.screen.get_child(id)
 
-    def update_styles(self) -> None:
+    def update_styles(self, node: DOMNode | None = None) -> None:
         """Request update of styles.
 
         Should be called whenever CSS classes / pseudo classes change.
 
         """
-        self._require_stylesheet_update = True
-        self.check_idle()
+        if node is None:
+            self._require_stylesheet_update = True
+            self.check_idle()
+        else:
+            self.stylesheet.update(node, animate=True)
 
     def update_visible_styles(self) -> None:
         """Update visible styles only."""
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index 834a154c8..da82dec94 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -27,6 +27,8 @@ from .types import Specificity3, Specificity6
 from ..dom import DOMNode
 from .. import messages
 
+from .._profile import timer
+
 
 class StylesheetParseError(StylesheetError):
     def __init__(self, errors: StylesheetErrors) -> None:
@@ -354,7 +356,6 @@ class Stylesheet:
                 for name, specificity_rules in rule_attributes.items()
             },
         )
-
         self.replace_rules(node, node_rules, animate=animate)
 
         node._component_styles.clear()
@@ -433,6 +434,7 @@ class Stylesheet:
 
         node.post_message_no_wait(messages.StylesUpdated(sender=node))
 
+    @timer("update")
     def update(self, root: DOMNode, animate: bool = False) -> None:
         """Update styles on node and its children.
 
@@ -440,8 +442,10 @@ class Stylesheet:
             root (DOMNode): Root note to update.
             animate (bool, optional): Enable CSS animation. Defaults to False.
         """
-        self.update_nodes(root.walk_children())
+        print("update", root)
+        self.update_nodes(root.walk_children(), animate=animate)
 
+    @timer("update_nodes")
     def update_nodes(self, nodes: Iterable[DOMNode], animate: bool = False) -> None:
         """Update styles for nodes.
 
@@ -450,6 +454,8 @@ class Stylesheet:
             animate (bool, optional): Enable CSS animation. Defaults to False.
         """
         apply = self.apply
+        nodes = list(nodes)
+        print(len(nodes), "NODES")
         for node in nodes:
             apply(node, animate=animate)
             if isinstance(node, Widget) and node.is_scrollable:
diff --git a/src/textual/widget.py b/src/textual/widget.py
index 3e0ebcfb3..d5a25df7a 100644
--- a/src/textual/widget.py
+++ b/src/textual/widget.py
@@ -1227,11 +1227,11 @@ class Widget(DOMNode):
 
     def watch_mouse_over(self, value: bool) -> None:
         """Update from CSS if mouse over state changes."""
-        self.app.update_visible_styles()
+        self.app.update_styles(self)
 
     def watch_has_focus(self, value: bool) -> None:
         """Update from CSS if has focus state changes."""
-        self.app.update_styles()
+        self.app.update_styles(self)
 
     def size_updated(
         self, size: Size, virtual_size: Size, container_size: Size

From 6879f91989f578e541083e48b7e2513f335abc12 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Thu, 25 Aug 2022 16:10:40 +0100
Subject: [PATCH 04/13] optimize stylesheet apply

---
 src/textual/css/model.py       | 20 ++++++++++++++--
 src/textual/css/stylesheet.py  | 42 +++++++++++++++++++++++++++-------
 src/textual/devtools/client.py |  1 +
 3 files changed, 53 insertions(+), 10 deletions(-)

diff --git a/src/textual/css/model.py b/src/textual/css/model.py
index cc960eedb..d0ab6a702 100644
--- a/src/textual/css/model.py
+++ b/src/textual/css/model.py
@@ -160,6 +160,8 @@ class RuleSet:
     styles: Styles = field(default_factory=Styles)
     errors: list[tuple[Token, str]] = field(default_factory=list)
     classes: set[str] = field(default_factory=set)
+    pseudo_classes: set[str] = field(default_factory=set)
+    ids: set[str] = field(default_factory=set)
     is_default_rules: bool = False
     tie_breaker: int = 0
 
@@ -195,11 +197,25 @@ class RuleSet:
     def _post_parse(self) -> None:
         """Called after the RuleSet is parsed."""
         # Build a set of the class names that have been updated
-        update = self.classes.update
+        update_classes = self.classes.update
+        update_ids = self.ids.update
+        update_pseudo_classes = self.pseudo_classes.update
         class_type = SelectorType.CLASS
+        id_type = SelectorType.ID
+
         for selector_set in self.selector_set:
-            update(
+            update_classes(
                 selector.name
                 for selector in selector_set.selectors
                 if selector.type == class_type
             )
+            update_ids(
+                selector.name
+                for selector in selector_set.selectors
+                if selector.type == id_type
+            )
+            update_pseudo_classes(
+                pseudo_class
+                for selector in selector_set.selectors
+                for pseudo_class in selector.pseudo_classes
+            )
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index da82dec94..10b0ce301 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -305,9 +305,11 @@ class Stylesheet:
         self.source = stylesheet.source
 
     @classmethod
-    def _check_rule(cls, rule: RuleSet, node: DOMNode) -> Iterable[Specificity3]:
+    def _check_rule(
+        cls, rule: RuleSet, css_path_nodes: list[DOMNode]
+    ) -> Iterable[Specificity3]:
         for selector_set in rule.selector_set:
-            if _check_selectors(selector_set.selectors, node.css_path_nodes):
+            if _check_selectors(selector_set.selectors, css_path_nodes):
                 yield selector_set.specificity
 
     def apply(self, node: DOMNode, animate: bool = False) -> None:
@@ -332,21 +334,47 @@ class Stylesheet:
         # same attribute, then we can choose the most specific rule and use that.
         rule_attributes: dict[str, list[tuple[Specificity6, object]]]
         rule_attributes = {}
+        rule_attributes_setdefault = rule_attributes.setdefault
 
         _check_rule = self._check_rule
 
+        css_path_nodes = node.css_path_nodes
+
+        path_ids = {path_node._id for path_node in css_path_nodes if path_node._id}
+        path_classes = {
+            class_name
+            for path_node in css_path_nodes
+            for class_name in path_node.classes
+        }
+        path_pseudo_classes = {
+            pseudo_class
+            for path_node in css_path_nodes
+            for pseudo_class in path_node.get_pseudo_classes()
+        }
+
         # Collect the rules defined in the stylesheet
         for rule in reversed(self.rules):
+            if rule.ids and not rule.ids.issubset(path_ids):
+                continue
+            if rule.classes and not rule.classes.issubset(path_classes):
+                continue
+            if rule.pseudo_classes and not rule.pseudo_classes.issubset(
+                path_pseudo_classes
+            ):
+                continue
+
             is_default_rules = rule.is_default_rules
             tie_breaker = rule.tie_breaker
-            for base_specificity in _check_rule(rule, node):
+            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
                 ):
-                    rule_attributes.setdefault(key, []).append(
+                    rule_attributes_setdefault(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(
@@ -382,7 +410,7 @@ class Stylesheet:
         base_styles = styles.base
 
         # Styles currently used on new rules
-        modified_rule_keys = {*base_styles.get_rules().keys(), *rules.keys()}
+        modified_rule_keys = base_styles.get_rules().keys() | rules.keys()
         # Current render rules (missing rules are filled with default)
         current_render_rules = styles.get_render_rules()
 
@@ -442,10 +470,9 @@ class Stylesheet:
             root (DOMNode): Root note to update.
             animate (bool, optional): Enable CSS animation. Defaults to False.
         """
-        print("update", root)
+
         self.update_nodes(root.walk_children(), animate=animate)
 
-    @timer("update_nodes")
     def update_nodes(self, nodes: Iterable[DOMNode], animate: bool = False) -> None:
         """Update styles for nodes.
 
@@ -455,7 +482,6 @@ class Stylesheet:
         """
         apply = self.apply
         nodes = list(nodes)
-        print(len(nodes), "NODES")
         for node in nodes:
             apply(node, animate=animate)
             if isinstance(node, Widget) and node.is_scrollable:
diff --git a/src/textual/devtools/client.py b/src/textual/devtools/client.py
index 63c59f3d8..802bd686a 100644
--- a/src/textual/devtools/client.py
+++ b/src/textual/devtools/client.py
@@ -163,6 +163,7 @@ class DevtoolsClient:
                 if isinstance(log, str):
                     await websocket.send_str(log)
                 else:
+                    assert isinstance(log, bytes)
                     await websocket.send_bytes(log)
                 log_queue.task_done()
 

From 8b672e0e8d36cd540b89a8c223305d2764f9c4f5 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Thu, 25 Aug 2022 16:16:45 +0100
Subject: [PATCH 05/13] use defaultdict which is faster

---
 src/textual/css/stylesheet.py | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index 10b0ce301..30913b419 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -332,9 +332,8 @@ class Stylesheet:
         # We can use this to determine, for a given rule, whether we should apply it
         # or not by examining the specificity. If we have two rules for the
         # same attribute, then we can choose the most specific rule and use that.
-        rule_attributes: dict[str, list[tuple[Specificity6, object]]]
-        rule_attributes = {}
-        rule_attributes_setdefault = rule_attributes.setdefault
+        rule_attributes: defaultdict[str, list[tuple[Specificity6, object]]]
+        rule_attributes = defaultdict(list)
 
         _check_rule = self._check_rule
 
@@ -369,9 +368,7 @@ class Stylesheet:
                 for key, rule_specificity, value in rule.styles.extract_rules(
                     base_specificity, is_default_rules, tie_breaker
                 ):
-                    rule_attributes_setdefault(key, []).append(
-                        (rule_specificity, value)
-                    )
+                    rule_attributes[key].append((rule_specificity, value))
 
         if not rule_attributes:
             return

From 26ff8043b1b9af2715836216f6fc8ad93e06c1be Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Thu, 25 Aug 2022 16:21:14 +0100
Subject: [PATCH 06/13] docstrings

---
 src/textual/_compositor.py    | 5 +++++
 src/textual/css/stylesheet.py | 1 -
 src/textual/screen.py         | 4 ++--
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/textual/_compositor.py b/src/textual/_compositor.py
index f7c5ae757..faf822adc 100644
--- a/src/textual/_compositor.py
+++ b/src/textual/_compositor.py
@@ -310,6 +310,11 @@ class Compositor:
 
     @property
     def visible_widgets(self) -> set[Widget]:
+        """Get a set of visible widgets.
+
+        Returns:
+            set[Widget]: Widgets in the screen.
+        """
         if self._visible_widgets is None:
             in_screen = self.size.region.__contains__
             self._visible_widgets = {
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index 30913b419..bdd3c1c53 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -459,7 +459,6 @@ class Stylesheet:
 
         node.post_message_no_wait(messages.StylesUpdated(sender=node))
 
-    @timer("update")
     def update(self, root: DOMNode, animate: bool = False) -> None:
         """Update styles on node and its children.
 
diff --git a/src/textual/screen.py b/src/textual/screen.py
index c8e886d6e..303c76ea0 100644
--- a/src/textual/screen.py
+++ b/src/textual/screen.py
@@ -65,12 +65,12 @@ class Screen(Widget):
 
     @property
     def widgets(self) -> list[Widget]:
-        """Get visible widgets."""
+        """Get all widgets."""
         return list(self._compositor.map.keys())
 
     @property
     def visible_widgets(self) -> list[Widget]:
-        """Get visible widgets."""
+        """Get a list of visible widgets."""
         return list(self._compositor.visible_widgets)
 
     def watch_dark(self, dark: bool) -> None:

From 520979bfe787f06911cdb885cbb270ae45c206fb Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Thu, 25 Aug 2022 16:22:37 +0100
Subject: [PATCH 07/13] Comment

---
 src/textual/_compositor.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/textual/_compositor.py b/src/textual/_compositor.py
index faf822adc..503706a3a 100644
--- a/src/textual/_compositor.py
+++ b/src/textual/_compositor.py
@@ -183,6 +183,7 @@ class Compositor:
         # Note this may be a superset of self.map.keys() as some widgets may be invisible for various reasons
         self.widgets: set[Widget] = set()
 
+        # A lazy cache of visible (on screen) widgets
         self._visible_widgets: set[Widget] | None = set()
 
         # The top level widget

From c3489f9e35d582ba6005b6871db80f153cd81694 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Thu, 25 Aug 2022 17:14:47 +0100
Subject: [PATCH 08/13] optimization

---
 src/textual/css/model.py      | 22 +++++++++++-----------
 src/textual/css/stylesheet.py | 25 +++----------------------
 src/textual/dom.py            | 20 ++++++++++++++++++++
 3 files changed, 34 insertions(+), 33 deletions(-)

diff --git a/src/textual/css/model.py b/src/textual/css/model.py
index d0ab6a702..7c3440ece 100644
--- a/src/textual/css/model.py
+++ b/src/textual/css/model.py
@@ -159,11 +159,11 @@ class RuleSet:
     selector_set: list[SelectorSet] = field(default_factory=list)
     styles: Styles = field(default_factory=Styles)
     errors: list[tuple[Token, str]] = field(default_factory=list)
-    classes: set[str] = field(default_factory=set)
-    pseudo_classes: set[str] = field(default_factory=set)
+
     ids: set[str] = field(default_factory=set)
     is_default_rules: bool = False
     tie_breaker: int = 0
+    selector_names: set[str] = field(default_factory=set)
 
     @classmethod
     def _selector_to_css(cls, selectors: list[Selector]) -> str:
@@ -197,25 +197,25 @@ class RuleSet:
     def _post_parse(self) -> None:
         """Called after the RuleSet is parsed."""
         # Build a set of the class names that have been updated
-        update_classes = self.classes.update
-        update_ids = self.ids.update
-        update_pseudo_classes = self.pseudo_classes.update
+
         class_type = SelectorType.CLASS
         id_type = SelectorType.ID
 
+        update_selectors = self.selector_names.update
+
         for selector_set in self.selector_set:
-            update_classes(
-                selector.name
+            update_selectors(
+                f".{selector.name}"
                 for selector in selector_set.selectors
                 if selector.type == class_type
             )
-            update_ids(
-                selector.name
+            update_selectors(
+                f"#{selector.name}"
                 for selector in selector_set.selectors
                 if selector.type == id_type
             )
-            update_pseudo_classes(
-                pseudo_class
+            update_selectors(
+                f":{pseudo_class}"
                 for selector in selector_set.selectors
                 for pseudo_class in selector.pseudo_classes
             )
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index bdd3c1c53..564ec9deb 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -323,10 +323,6 @@ class Stylesheet:
                 rule will be applied.
             animate (bool, optional): Animate changed rules. Defaults to ``False``.
         """
-
-        # TODO: Need to optimize to make applying stylesheet more efficient
-        # I think we can pre-calculate which rules may be applicable to a given node
-
         # 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.
         # We can use this to determine, for a given rule, whether we should apply it
@@ -338,28 +334,13 @@ class Stylesheet:
         _check_rule = self._check_rule
 
         css_path_nodes = node.css_path_nodes
-
-        path_ids = {path_node._id for path_node in css_path_nodes if path_node._id}
-        path_classes = {
-            class_name
-            for path_node in css_path_nodes
-            for class_name in path_node.classes
-        }
-        path_pseudo_classes = {
-            pseudo_class
-            for path_node in css_path_nodes
-            for pseudo_class in path_node.get_pseudo_classes()
+        selector_names = {
+            selector for node in css_path_nodes for selector in node._selector_names
         }
 
         # Collect the rules defined in the stylesheet
         for rule in reversed(self.rules):
-            if rule.ids and not rule.ids.issubset(path_ids):
-                continue
-            if rule.classes and not rule.classes.issubset(path_classes):
-                continue
-            if rule.pseudo_classes and not rule.pseudo_classes.issubset(
-                path_pseudo_classes
-            ):
+            if rule.selector_names and not rule.selector_names.issubset(selector_names):
                 continue
 
             is_default_rules = rule.is_default_rules
diff --git a/src/textual/dom.py b/src/textual/dom.py
index dc8d124b2..e33fa780d 100644
--- a/src/textual/dom.py
+++ b/src/textual/dom.py
@@ -144,6 +144,10 @@ class DOMNode(MessagePump):
         # Node bases are in reversed order so that the base class is lower priority
         return self._css_bases(self.__class__)
 
+    @property
+    def css_types(self) -> set[str]:
+        return {cls.__name__ for cls in self._css_bases(self.__class__)}
+
     @classmethod
     def _css_bases(cls, base: Type[DOMNode]) -> Iterator[Type[DOMNode]]:
         """Get the DOMNode base classes, which inherit CSS.
@@ -311,6 +315,22 @@ class DOMNode(MessagePump):
             append(node)
         return result[::-1]
 
+    @property
+    def _selector_names(self) -> list[str]:
+        """Get a set of selectors applicable to this widget.
+
+        Returns:
+            set[str]: Set of selector names.
+        """
+        selectors: list[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}")
+        return selectors
+
     @property
     def display(self) -> bool:
         """

From e19a0090f7f55565e7b2615a5f4f3e5cea8d2750 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Thu, 25 Aug 2022 17:17:25 +0100
Subject: [PATCH 09/13] further optimizations

---
 src/textual/dom.py | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/src/textual/dom.py b/src/textual/dom.py
index e33fa780d..1218820fd 100644
--- a/src/textual/dom.py
+++ b/src/textual/dom.py
@@ -87,6 +87,7 @@ class DOMNode(MessagePump):
 
         self._auto_refresh: float | None = None
         self._auto_refresh_timer: Timer | None = None
+        self._css_types = {cls.__name__ for cls in self._css_bases(self.__class__)}
 
         super().__init__()
 
@@ -144,10 +145,6 @@ class DOMNode(MessagePump):
         # Node bases are in reversed order so that the base class is lower priority
         return self._css_bases(self.__class__)
 
-    @property
-    def css_types(self) -> set[str]:
-        return {cls.__name__ for cls in self._css_bases(self.__class__)}
-
     @classmethod
     def _css_bases(cls, base: Type[DOMNode]) -> Iterator[Type[DOMNode]]:
         """Get the DOMNode base classes, which inherit CSS.
@@ -325,7 +322,7 @@ class DOMNode(MessagePump):
         selectors: list[str] = [
             *(f".{class_name}" for class_name in self._classes),
             *(f":{class_name}" for class_name in self.get_pseudo_classes()),
-            *self.css_types,
+            *self._css_types,
         ]
         if self._id is not None:
             selectors.append(f"#{self._id}")

From f49b8d2fadc7104e24903156145e7f56d791a4da Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Fri, 26 Aug 2022 10:12:59 +0100
Subject: [PATCH 10/13] narrow down rules

---
 docs/examples/introduction/stopwatch.css |  3 +++
 docs/examples/introduction/stopwatch.py  |  1 +
 src/textual/_compositor.py               |  3 +--
 src/textual/app.py                       | 25 ++++++++++++----------
 src/textual/css/model.py                 | 16 +++++++++++++-
 src/textual/css/stylesheet.py            | 27 ++++++++++++++++++++----
 src/textual/dom.py                       |  7 +++---
 7 files changed, 61 insertions(+), 21 deletions(-)

diff --git a/docs/examples/introduction/stopwatch.css b/docs/examples/introduction/stopwatch.css
index 472dccc89..c7e0fbb92 100644
--- a/docs/examples/introduction/stopwatch.css
+++ b/docs/examples/introduction/stopwatch.css
@@ -52,3 +52,6 @@ Button {
     visibility: hidden
 }
 
+/* #timers:hover {
+    background: blue;
+} */
diff --git a/docs/examples/introduction/stopwatch.py b/docs/examples/introduction/stopwatch.py
index 15dff3a1c..ba31a7e26 100644
--- a/docs/examples/introduction/stopwatch.py
+++ b/docs/examples/introduction/stopwatch.py
@@ -88,6 +88,7 @@ class StopwatchApp(App):
         new_stopwatch = Stopwatch()
         self.query_one("#timers").mount(new_stopwatch)
         new_stopwatch.scroll_visible()
+        self.sub_title = str(len(self.query("Stopwatch")))
 
     def action_remove_stopwatch(self) -> None:
         """Called to remove a timer."""
diff --git a/src/textual/_compositor.py b/src/textual/_compositor.py
index 503706a3a..8d5c299b7 100644
--- a/src/textual/_compositor.py
+++ b/src/textual/_compositor.py
@@ -487,9 +487,8 @@ class Compositor:
         """Get the widget under the given point or None."""
         # TODO: Optimize with some line based lookup
         contains = Region.contains
-        is_visible = self.visible_widgets.__contains__
         for widget, cropped_region, region, *_ in self:
-            if is_visible(widget) and contains(cropped_region, x, y):
+            if contains(cropped_region, x, y):
                 return widget, region
         raise errors.NoWidget(f"No widget under screen coordinate ({x}, {y})")
 
diff --git a/src/textual/app.py b/src/textual/app.py
index b1a99b0ff..0be12cd51 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -224,7 +224,7 @@ class App(Generic[ReturnType], DOMNode):
         self.design = DEFAULT_COLORS
 
         self.stylesheet = Stylesheet(variables=self.get_css_variables())
-        self._require_stylesheet_update = False
+        self._require_stylesheet_update: set[DOMNode] = set()
         self.css_path = css_path or self.CSS_PATH
 
         self._registry: WeakSet[DOMNode] = WeakSet()
@@ -720,15 +720,13 @@ class App(Generic[ReturnType], DOMNode):
         Should be called whenever CSS classes / pseudo classes change.
 
         """
-        if node is None:
-            self._require_stylesheet_update = True
-            self.check_idle()
-        else:
-            self.stylesheet.update(node, animate=True)
+        self._require_stylesheet_update.add(self.screen if node is None else node)
+        self.check_idle()
 
     def update_visible_styles(self) -> None:
         """Update visible styles only."""
-        self.stylesheet.update_nodes(self.screen.visible_widgets)
+        self._require_stylesheet_update.update(self.screen.visible_widgets)
+        self.check_idle()
 
     def mount(self, *anon_widgets: Widget, **widgets: Widget) -> None:
         """Mount widgets. Widgets specified as positional args, or keywords args. If supplied
@@ -1144,16 +1142,21 @@ class App(Generic[ReturnType], DOMNode):
 
         self.set_timer(screenshot_timer, on_screenshot, name="screenshot timer")
 
-    def on_mount(self) -> None:
+    def _on_mount(self) -> None:
         widgets = self.compose()
         if widgets:
             self.mount_all(widgets)
 
-    async def on_idle(self) -> None:
+    def _on_idle(self) -> None:
         """Perform actions when there are no messages in the queue."""
         if self._require_stylesheet_update:
-            self._require_stylesheet_update = False
-            self.stylesheet.update(self, animate=True)
+            nodes: set[DOMNode] = {
+                child
+                for node in self._require_stylesheet_update
+                for child in node.walk_children()
+            }
+            self._require_stylesheet_update.clear()
+            self.stylesheet.update_nodes(nodes, animate=True)
 
     def _register_child(self, parent: DOMNode, child: Widget) -> bool:
         if child not in self._registry:
diff --git a/src/textual/css/model.py b/src/textual/css/model.py
index 7c3440ece..c5efebc15 100644
--- a/src/textual/css/model.py
+++ b/src/textual/css/model.py
@@ -160,11 +160,13 @@ class RuleSet:
     styles: Styles = field(default_factory=Styles)
     errors: list[tuple[Token, str]] = field(default_factory=list)
 
-    ids: set[str] = field(default_factory=set)
     is_default_rules: bool = False
     tie_breaker: int = 0
     selector_names: set[str] = field(default_factory=set)
 
+    def __hash__(self):
+        return id(self)
+
     @classmethod
     def _selector_to_css(cls, selectors: list[Selector]) -> str:
         tokens: list[str] = []
@@ -200,10 +202,22 @@ class RuleSet:
 
         class_type = SelectorType.CLASS
         id_type = SelectorType.ID
+        type_type = SelectorType.TYPE
+        universal_type = SelectorType.UNIVERSAL
 
         update_selectors = self.selector_names.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
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index 564ec9deb..c33600ea4 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -312,7 +312,13 @@ class Stylesheet:
             if _check_selectors(selector_set.selectors, css_path_nodes):
                 yield selector_set.specificity
 
-    def apply(self, node: DOMNode, animate: bool = False) -> None:
+    def apply(
+        self,
+        node: DOMNode,
+        *,
+        limit_rules: set[RuleSet] | None = None,
+        animate: bool = False,
+    ) -> None:
         """Apply the stylesheet to a DOM node.
 
         Args:
@@ -334,12 +340,18 @@ class Stylesheet:
         _check_rule = self._check_rule
 
         css_path_nodes = node.css_path_nodes
+
         selector_names = {
             selector for node in css_path_nodes for selector in node._selector_names
         }
 
+        rules: Iterable[RuleSet]
+        if limit_rules:
+            rules = [rule for rule in reversed(self.rules) if rule in limit_rules]
+        else:
+            rules = reversed(self.rules)
         # Collect the rules defined in the stylesheet
-        for rule in reversed(self.rules):
+        for rule in rules:
             if rule.selector_names and not rule.selector_names.issubset(selector_names):
                 continue
 
@@ -457,10 +469,17 @@ class Stylesheet:
             nodes (DOMNode): Nodes to update.
             animate (bool, optional): Enable CSS animation. Defaults to False.
         """
+
+        rules_map: defaultdict[str, list[RuleSet]] = defaultdict(list)
+        for rule in self.rules:
+            for name in rule.selector_names:
+                rules_map[name].append(rule)
+
         apply = self.apply
-        nodes = list(nodes)
+
         for node in nodes:
-            apply(node, animate=animate)
+            rules = {rule for name in node._selector_names for rule in rules_map[name]}
+            apply(node, limit_rules=rules, animate=animate)
             if isinstance(node, Widget) and node.is_scrollable:
                 if node.show_vertical_scrollbar:
                     apply(node.vertical_scrollbar)
diff --git a/src/textual/dom.py b/src/textual/dom.py
index 1218820fd..babc62f2b 100644
--- a/src/textual/dom.py
+++ b/src/textual/dom.py
@@ -320,6 +320,7 @@ class DOMNode(MessagePump):
             set[str]: Set of selector names.
         """
         selectors: list[str] = [
+            "*",
             *(f".{class_name}" for class_name in self._classes),
             *(f":{class_name}" for class_name in self.get_pseudo_classes()),
             *self._css_types,
@@ -716,7 +717,7 @@ class DOMNode(MessagePump):
         if old_classes == self._classes:
             return
         try:
-            self.app.stylesheet.update(self, animate=True)
+            self.app.update_styles(self)
         except NoActiveAppError:
             pass
 
@@ -732,7 +733,7 @@ class DOMNode(MessagePump):
         if old_classes == self._classes:
             return
         try:
-            self.app.stylesheet.update(self, animate=True)
+            self.app.update_styles(self)
         except NoActiveAppError:
             pass
 
@@ -748,7 +749,7 @@ class DOMNode(MessagePump):
         if old_classes == self._classes:
             return
         try:
-            self.app.stylesheet.update(self, animate=True)
+            self.app.update_styles(self)
         except NoActiveAppError:
             pass
 

From 6e01d46b40b432c70ea4ee6cf402355adcb36538 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Fri, 26 Aug 2022 10:13:49 +0100
Subject: [PATCH 11/13] remove debug

---
 docs/examples/introduction/stopwatch.css | 4 ----
 docs/examples/introduction/stopwatch.py  | 1 -
 2 files changed, 5 deletions(-)

diff --git a/docs/examples/introduction/stopwatch.css b/docs/examples/introduction/stopwatch.css
index c7e0fbb92..93678369c 100644
--- a/docs/examples/introduction/stopwatch.css
+++ b/docs/examples/introduction/stopwatch.css
@@ -51,7 +51,3 @@ Button {
 .started #reset {
     visibility: hidden
 }
-
-/* #timers:hover {
-    background: blue;
-} */
diff --git a/docs/examples/introduction/stopwatch.py b/docs/examples/introduction/stopwatch.py
index ba31a7e26..15dff3a1c 100644
--- a/docs/examples/introduction/stopwatch.py
+++ b/docs/examples/introduction/stopwatch.py
@@ -88,7 +88,6 @@ class StopwatchApp(App):
         new_stopwatch = Stopwatch()
         self.query_one("#timers").mount(new_stopwatch)
         new_stopwatch.scroll_visible()
-        self.sub_title = str(len(self.query("Stopwatch")))
 
     def action_remove_stopwatch(self) -> None:
         """Called to remove a timer."""

From f794c85b2fcfeb16c6451fa8fa0df5e9375632d6 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Fri, 26 Aug 2022 12:44:29 +0100
Subject: [PATCH 12/13] precalculate rules_map

---
 src/textual/css/stylesheet.py | 50 +++++++++++++++++++++++++----------
 1 file changed, 36 insertions(+), 14 deletions(-)

diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index c33600ea4..b705d0f50 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -4,10 +4,10 @@ import os
 from collections import defaultdict
 from operator import itemgetter
 from pathlib import Path, PurePath
-from typing import cast, Iterable, NamedTuple
+from typing import Iterable, NamedTuple, cast
 
 import rich.repr
-from rich.console import RenderableType, RenderResult, Console, ConsoleOptions
+from rich.console import Console, ConsoleOptions, RenderableType, RenderResult
 from rich.markup import render
 from rich.padding import Padding
 from rich.panel import Panel
@@ -15,19 +15,18 @@ from rich.style import Style
 from rich.syntax import Syntax
 from rich.text import Text
 
-from textual.widget import Widget
+from .. import messages
+from .._profile import timer
+from ..dom import DOMNode
+from ..widget import Widget
 from .errors import StylesheetError
 from .match import _check_selectors
 from .model import RuleSet
 from .parse import parse
 from .styles import RulesMap, Styles
-from .tokenize import tokenize_values, Token
+from .tokenize import Token, tokenize_values
 from .tokenizer import TokenError
 from .types import Specificity3, Specificity6
-from ..dom import DOMNode
-from .. import messages
-
-from .._profile import timer
 
 
 class StylesheetParseError(StylesheetError):
@@ -137,6 +136,7 @@ class CssSource(NamedTuple):
 class Stylesheet:
     def __init__(self, *, variables: dict[str, str] | None = None) -> None:
         self._rules: list[RuleSet] = []
+        self._rules_map: dict[str, list[RuleSet]] | None = None
         self.variables = variables or {}
         self.source: dict[str, CssSource] = {}
         self._require_parse = False
@@ -146,12 +146,32 @@ class Stylesheet:
 
     @property
     def rules(self) -> list[RuleSet]:
+        """List of rule sets.
+
+        Returns:
+            list[RuleSet]: List of rules sets for this stylesheet.
+        """
         if self._require_parse:
             self.parse()
             self._require_parse = False
         assert self._rules is not None
         return self._rules
 
+    @property
+    def rules_map(self) -> dict[str, list[RuleSet]]:
+        """Structure that maps a selector on to a list of rules.
+
+        Returns:
+            dict[str, list[RuleSet]]: Mapping of selector to rule sets.
+        """
+        if self._rules_map is None:
+            rules_map: dict[str, list[RuleSet]] = defaultdict(list)
+            for rule in self.rules:
+                for name in rule.selector_names:
+                    rules_map[name].append(rule)
+            self._rules_map = dict(rules_map)
+        return self._rules_map
+
     @property
     def css(self) -> str:
         return "\n\n".join(rule_set.css for rule_set in self.rules)
@@ -285,6 +305,7 @@ class Stylesheet:
             add_rules(css_rules)
         self._rules = rules
         self._require_parse = False
+        self._rules_map = None
 
     def reparse(self) -> None:
         """Re-parse source, applying new variables.
@@ -302,6 +323,7 @@ class Stylesheet:
             )
         stylesheet.parse()
         self._rules = stylesheet.rules
+        self._rules_map = None
         self.source = stylesheet.source
 
     @classmethod
@@ -470,15 +492,15 @@ class Stylesheet:
             animate (bool, optional): Enable CSS animation. Defaults to False.
         """
 
-        rules_map: defaultdict[str, list[RuleSet]] = defaultdict(list)
-        for rule in self.rules:
-            for name in rule.selector_names:
-                rules_map[name].append(rule)
-
+        rules_map = self.rules_map
         apply = self.apply
 
         for node in nodes:
-            rules = {rule for name in node._selector_names for rule in rules_map[name]}
+            rules = {
+                rule
+                for name in node._selector_names
+                for rule in rules_map.get(name, [])
+            }
             apply(node, limit_rules=rules, animate=animate)
             if isinstance(node, Widget) and node.is_scrollable:
                 if node.show_vertical_scrollbar:

From 46ee74848cbed486b82075296e3d4f8de4463c82 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Fri, 26 Aug 2022 12:52:07 +0100
Subject: [PATCH 13/13] simplify

---
 src/textual/css/stylesheet.py | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index b705d0f50..849688c42 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -360,13 +360,8 @@ class Stylesheet:
         rule_attributes = defaultdict(list)
 
         _check_rule = self._check_rule
-
         css_path_nodes = node.css_path_nodes
 
-        selector_names = {
-            selector for node in css_path_nodes for selector in node._selector_names
-        }
-
         rules: Iterable[RuleSet]
         if limit_rules:
             rules = [rule for rule in reversed(self.rules) if rule in limit_rules]
@@ -374,9 +369,6 @@ class Stylesheet:
             rules = reversed(self.rules)
         # Collect the rules defined in the stylesheet
         for rule in rules:
-            if rule.selector_names and not rule.selector_names.issubset(selector_names):
-                continue
-
             is_default_rules = rule.is_default_rules
             tie_breaker = rule.tie_breaker
             for base_specificity in _check_rule(rule, css_path_nodes):
@@ -499,7 +491,8 @@ class Stylesheet:
             rules = {
                 rule
                 for name in node._selector_names
-                for rule in rules_map.get(name, [])
+                if name in rules_map
+                for rule in rules_map[name]
             }
             apply(node, limit_rules=rules, animate=animate)
             if isinstance(node, Widget) and node.is_scrollable: