LibWeb: Postpone :has() style invalidation until update_style()

This allows to do ancestors traversal only once even if
`invalidate_style()` was called multiple times for the same node.

Libraries/LibWeb/DOM/Document.cpp

@@ -1438,7 +1438,7 @@ void Document::update_style()
     // style change event. [CSS-Transitions-2]
     m_transition_generation++;
 
-    invalidate_elements_affected_by_has_in_non_subject_position();
+    invalidate_style_of_elements_affected_by_has();
 
     if (!needs_full_style_update() && !needs_style_update() && !child_needs_style_update())
         return;
@@ -1659,11 +1659,18 @@ static Node* find_common_ancestor(Node* a, Node* b)
     return nullptr;
 }
 
-void Document::invalidate_elements_affected_by_has_in_non_subject_position()
+void Document::invalidate_style_of_elements_affected_by_has()
 {
-    if (!m_needs_invalidate_elements_affected_by_has_in_non_subject_position)
+    if (m_pending_nodes_for_style_invalidation_due_to_presence_of_has.is_empty()) {
         return;
-    m_needs_invalidate_elements_affected_by_has_in_non_subject_position = false;
+    }
+
+    for (auto const& node : m_pending_nodes_for_style_invalidation_due_to_presence_of_has) {
+        if (node.is_null())
+            continue;
+        node->invalidate_ancestors_affected_by_has_in_subject_position();
+    }
+    m_pending_nodes_for_style_invalidation_due_to_presence_of_has.clear();
 
     // Take care of elements that affected by :has() in non-subject position, i.e., ".a:has(.b) > .c".
     // Elements affected by :has() in subject position, i.e., ".a:has(.b)", are handled by

Libraries/LibWeb/DOM/Document.h

@@ -510,9 +510,6 @@ public:
     [[nodiscard]] bool needs_full_layout_tree_update() const { return m_needs_full_layout_tree_update; }
     void set_needs_full_layout_tree_update(bool b) { m_needs_full_layout_tree_update = b; }
 
-    bool needs_invalidate_elements_affected_by_has_in_non_subject_position() const { return m_needs_invalidate_elements_affected_by_has_in_non_subject_position; }
-    void set_needs_invalidate_elements_affected_by_has_in_non_subject_position(bool b) { m_needs_invalidate_elements_affected_by_has_in_non_subject_position = b; }
-
     void set_needs_to_refresh_scroll_state(bool b);
 
     bool has_active_favicon() const { return m_active_favicon; }
@@ -807,6 +804,11 @@ public:
     void add_render_blocking_element(GC::Ref<Element>);
     void remove_render_blocking_element(GC::Ref<Element>);
 
+    void schedule_ancestors_style_invalidation_due_to_presence_of_has(Node& node)
+    {
+        m_pending_nodes_for_style_invalidation_due_to_presence_of_has.set(node.make_weak_ptr<Node>());
+    }
+
 protected:
     virtual void initialize(JS::Realm&) override;
     virtual void visit_edges(Cell::Visitor&) override;
@@ -817,7 +819,7 @@ private:
     // ^HTML::GlobalEventHandlers
     virtual GC::Ptr<EventTarget> global_event_handlers_to_event_target(FlyString const&) final { return *this; }
 
-    void invalidate_elements_affected_by_has_in_non_subject_position();
+    void invalidate_style_of_elements_affected_by_has();
 
     void tear_down_layout_tree();
 
@@ -961,7 +963,6 @@ private:
 
     bool m_needs_full_style_update { false };
     bool m_needs_full_layout_tree_update { false };
-    bool m_needs_invalidate_elements_affected_by_has_in_non_subject_position { false };
 
     bool m_needs_animated_style_update { false };
 
@@ -1146,6 +1147,8 @@ private:
 
     // https://html.spec.whatwg.org/multipage/dom.html#render-blocking-element-set
     HashTable<GC::Ref<Element>> m_render_blocking_elements;
+
+    HashTable<WeakPtr<Node>> m_pending_nodes_for_style_invalidation_due_to_presence_of_has;
 };
 
 template<>

Libraries/LibWeb/DOM/Node.cpp

@@ -430,8 +430,22 @@ void Node::invalidate_style(StyleInvalidationReason reason)
         return;
 
     if (document().style_computer().may_have_has_selectors()) {
-        invalidate_ancestors_affected_by_has_in_subject_position();
+        if (reason == StyleInvalidationReason::NodeRemove) {
-        document().set_needs_invalidate_elements_affected_by_has_in_non_subject_position(true);
+            for (auto* previous_sibling = this->previous_sibling(); previous_sibling; previous_sibling = previous_sibling->previous_sibling()) {
+                if (!previous_sibling->is_element())
+                    continue;
+                auto& element = static_cast<Element&>(*previous_sibling);
+                if (element.affected_by_has_pseudo_class_with_relative_selector_that_has_sibling_combinator()) {
+                    element.set_needs_style_update(true);
+                }
+            }
+
+            if (auto parent = parent_or_shadow_host(); parent) {
+                document().schedule_ancestors_style_invalidation_due_to_presence_of_has(*parent);
+            }
+        } else {
+            document().schedule_ancestors_style_invalidation_due_to_presence_of_has(*this);
+        }
     }
 
     if (!needs_style_update() && !document().needs_full_style_update()) {
@@ -493,8 +507,7 @@ void Node::invalidate_style(StyleInvalidationReason, Vector<CSS::InvalidationSet
         properties_used_in_has_selectors |= document().style_computer().invalidation_property_used_in_has_selector(property);
     }
     if (properties_used_in_has_selectors) {
-        invalidate_ancestors_affected_by_has_in_subject_position();
+        document().schedule_ancestors_style_invalidation_due_to_presence_of_has(*this);
-        document().set_needs_invalidate_elements_affected_by_has_in_non_subject_position(true);
     }
 
     auto invalidation_set = document().style_computer().invalidation_set_for_properties(properties);