Pseudo update

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 - Added `background-tint` CSS rule https://github.com/Textualize/textual/pull/5117
+- Added `:first-of-type`, `:last-of-type`, `:odd`, and `:even` pseudo classes https://github.com/Textualize/textual/pull/5139
 
 ## [0.83.0] - 2024-10-10
 

docs/guide/CSS.md

@@ -330,10 +330,14 @@ Here are some other pseudo classes:
 - `:dark` Matches widgets in dark mode (where `App.dark == True`).
 - `:disabled` Matches widgets which are in a disabled state.
 - `:enabled` Matches widgets which are in an enabled state.
+- `:even` Matches a widget at an evenly numbered position within its siblings.
+- `:first-of-type` Matches a widget that is the first of its type amongst its siblings.
 - `:focus-within` Matches widgets with a focused child widget.
 - `:focus` Matches widgets which have input focus.
 - `:inline` Matches widgets when the app is running in inline mode.
+- `:last-of-type` Matches a widget that is the last of its type amongst its siblings.
 - `:light` Matches widgets in dark mode (where `App.dark == False`).
+- `:odd` Matches a widget at an oddly numbered position within its siblings.
 
 ## Combinators
 

src/textual/app.py

@@ -487,6 +487,16 @@ class MyApp(App[None]):
     INLINE_PADDING: ClassVar[int] = 1
     """Number of blank lines above an inline app."""
 
+    _PSEUDO_CLASSES: ClassVar[dict[str, Callable[[App], bool]]] = {
+        "focus": lambda app: app.app_focus,
+        "blur": lambda app: not app.app_focus,
+        "dark": lambda app: app.dark,
+        "light": lambda app: not app.dark,
+        "inline": lambda app: app.is_inline,
+        "ansi": lambda app: app.ansi_color,
+        "nocolor": lambda app: app.no_color,
+    }  # type: ignore[assignment]
+
     title: Reactive[str] = Reactive("", compute=False)
     """The title of the app, displayed in the header."""
     sub_title: Reactive[str] = Reactive("", compute=False)
@@ -892,21 +902,6 @@ def _context(self) -> Generator[None, None, None]:
             active_message_pump.reset(message_pump_reset_token)
             active_app.reset(app_reset_token)
 
-    def get_pseudo_classes(self) -> Iterable[str]:
-        """Pseudo classes for a widget.
-
-        Returns:
-            Names of the pseudo classes.
-        """
-        yield "focus" if self.app_focus else "blur"
-        yield "dark" if self.dark else "light"
-        if self.is_inline:
-            yield "inline"
-        if self.ansi_color:
-            yield "ansi"
-        if self.no_color:
-            yield "nocolor"
-
     def _watch_ansi_color(self, ansi_color: bool) -> None:
         """Enable or disable the truecolor filter when the reactive changes"""
         for filter in self._filters:
@@ -3148,17 +3143,21 @@ def _register(
             widget_list = widgets
 
         apply_stylesheet = self.stylesheet.apply
+        new_widgets: list[Widget] = []
+        add_new_widget = new_widgets.append
         for widget in widget_list:
             widget._closing = False
             widget._closed = False
             widget._pruning = False
             if not isinstance(widget, Widget):
                 raise AppError(f"Can't register {widget!r}; expected a Widget instance")
             if widget not in self._registry:
+                add_new_widget(widget)
                 self._register_child(parent, widget, before, after)
                 if widget._nodes:
                     self._register(widget, *widget._nodes, cache=cache)
-                apply_stylesheet(widget, cache=cache)
+        for widget in new_widgets:
+            apply_stylesheet(widget, cache=cache)
 
         if not self._running:
             # If the app is not running, prevent awaiting of the widget tasks

src/textual/css/constants.py

@@ -72,6 +72,10 @@
     "inline",
     "light",
     "nocolor",
+    "first-of-type",
+    "last-of-type",
+    "odd",
+    "even",
 }
 VALID_OVERLAY: Final = {"none", "screen"}
 VALID_CONSTRAIN: Final = {"inflect", "inside", "none"}

src/textual/css/stylesheet.py

@@ -432,6 +432,15 @@ def _check_rule(
             if _check_selectors(selector_set.selectors, css_path_nodes):
                 yield selector_set.specificity
 
+    # pseudo classes which iterate over many nodes
+    # these have the potential to be slow, and shouldn't be used in a cache key
+    EXPENSIVE_PSEUDO_CLASSES = {
+        "first-of-type",
+        "last-of_type",
+        "odd",
+        "even",
+    }
+
     def apply(
         self,
         node: DOMNode,
@@ -467,14 +476,18 @@ def apply(
             for rule in rules_map[name]
         }
         rules = list(filter(limit_rules.__contains__, reversed(self.rules)))
-
-        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
+        all_pseudo_classes = set().union(*[rule.pseudo_classes for rule in rules])
+        node._has_hover_style = "hover" in all_pseudo_classes
+        node._has_focus_within = "focus-within" in all_pseudo_classes
+        node._has_order_style = not all_pseudo_classes.isdisjoint(
+            {"first-of-type", "last-of-type", "odd", "even"}
         )
 
-        cache_key: tuple | None
-        if cache is not None:
+        cache_key: tuple | None = None
+
+        if cache is not None and all_pseudo_classes.isdisjoint(
+            self.EXPENSIVE_PSEUDO_CLASSES
+        ):
             cache_key = (
                 node._parent,
                 (
@@ -483,16 +496,14 @@ def apply(
                     else (node._id if f"#{node._id}" in rules_map else None)
                 ),
                 node.classes,
-                node.pseudo_classes,
+                node._pseudo_classes_cache_key,
                 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
@@ -561,8 +572,7 @@ 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
+            if cache_key is not None:
                 cache[cache_key] = node_rules
             self.replace_rules(node, node_rules, animate=animate)
         self._process_component_classes(node)

src/textual/dom.py

@@ -180,6 +180,9 @@ class DOMNode(MessagePump):
     # Names of potential computed reactives
     _computes: ClassVar[frozenset[str]]
 
+    _PSEUDO_CLASSES: ClassVar[dict[str, Callable[[object], bool]]] = {}
+    """Pseudo class checks."""
+
     def __init__(
         self,
         *,
@@ -217,6 +220,8 @@ def __init__(
         )
         self._has_hover_style: bool = False
         self._has_focus_within: bool = False
+        self._has_order_style: bool = False
+        """The node has an ordered dependent pseudo-style (`:odd`, `:even`, `:first-of-type`, `:last-of-type`)"""
         self._reactive_connect: (
             dict[str, tuple[MessagePump, Reactive[object] | object]] | None
         ) = None
@@ -1228,13 +1233,18 @@ def on_dark_change(old_value:bool, new_value:bool) -> None:
         """
         _watch(self, obj, attribute_name, callback, init=init)
 
-    def get_pseudo_classes(self) -> Iterable[str]:
-        """Get any pseudo classes applicable to this Node, e.g. hover, focus.
+    def get_pseudo_classes(self) -> set[str]:
+        """Pseudo classes for a widget.
 
         Returns:
-            Iterable of strings, such as a generator.
+            Names of the pseudo classes.
         """
-        return ()
+
+        return {
+            name
+            for name, check_class in self._PSEUDO_CLASSES.items()
+            if check_class(self)
+        }
 
     def reset_styles(self) -> None:
         """Reset styles back to their initial state."""
@@ -1658,7 +1668,10 @@ def has_pseudo_class(self, class_name: str) -> bool:
         Returns:
             `True` if the DOM node has the pseudo class, `False` if not.
         """
-        return class_name in self.get_pseudo_classes()
+        try:
+            return self._PSEUDO_CLASSES[class_name](self)
+        except KeyError:
+            return False
 
     def has_pseudo_classes(self, class_names: set[str]) -> bool:
         """Check the node has all the given pseudo classes.
@@ -1669,7 +1682,16 @@ def has_pseudo_classes(self, class_names: set[str]) -> bool:
         Returns:
             `True` if all pseudo class names are present.
         """
-        return class_names.issubset(self.get_pseudo_classes())
+        PSEUDO_CLASSES = self._PSEUDO_CLASSES
+        try:
+            return all(PSEUDO_CLASSES[name](self) for name in class_names)
+        except KeyError:
+            return False
+
+    @property
+    def _pseudo_classes_cache_key(self) -> tuple[int, ...]:
+        """A cache key used when updating a number of nodes from the stylesheet."""
+        return ()
 
     def refresh(
         self, *, repaint: bool = True, layout: bool = False, recompose: bool = False