LibWeb: Move "needs layout update" flag from DOM to layout tree

This is in preparation for allowing anonymous boxes to retain their
intrinsic size cache across layouts.

Libraries/LibWeb/Animations/KeyframeEffect.cpp

@@ -968,8 +968,8 @@ void KeyframeEffect::update_computed_properties()
         }
     }
 
-    if (invalidation.relayout)
-        target->set_needs_layout_update(DOM::SetNeedsLayoutReason::KeyframeEffect);
+    if (invalidation.relayout && target->layout_node())
+        target->layout_node()->set_needs_layout_update(DOM::SetNeedsLayoutReason::KeyframeEffect);
     if (invalidation.rebuild_layout_tree) {
         // We mark layout tree for rebuild starting from parent element to correctly invalidate
         // "display" property change to/from "contents" value.

Libraries/LibWeb/DOM/CharacterData.cpp

@@ -147,7 +147,7 @@ WebIDL::ExceptionOr<void> CharacterData::replace_data(size_t offset, size_t coun
         static_cast<Layout::TextNode&>(*layout_node).invalidate_text_for_rendering();
 
         // We also need to relayout.
-        set_needs_layout_update(SetNeedsLayoutReason::CharacterDataReplaceData);
+        layout_node->set_needs_layout_update(SetNeedsLayoutReason::CharacterDataReplaceData);
     }
 
     document().bump_character_data_version();

Libraries/LibWeb/DOM/Document.cpp

@@ -1293,7 +1293,7 @@ void Document::update_layout(UpdateLayoutReason reason)
 
     update_style();
 
-    if (!m_needs_layout_update && m_layout_root)
+    if (m_layout_root && !m_layout_root->needs_layout_update())
         return;
 
     // NOTE: If this is a document hosting <template> contents, layout is unnecessary.
@@ -1332,8 +1332,7 @@ void Document::update_layout(UpdateLayoutReason reason)
         if (auto dom_node = child.dom_node(); dom_node && dom_node->is_element()) {
             child.set_has_size_containment(as<Element>(*dom_node).has_size_containment());
         }
-        bool needs_layout_update = child.dom_node() && child.dom_node()->needs_layout_update();
-        if (needs_layout_update || child.is_anonymous()) {
+        if (child.needs_layout_update() || child.is_anonymous()) {
             child.reset_cached_intrinsic_sizes();
         }
         child.clear_contained_abspos_children();
@@ -1403,7 +1402,7 @@ void Document::update_layout(UpdateLayoutReason reason)
         paintable()->recompute_selection_states(*range);
     }
 
-    for_each_shadow_including_inclusive_descendant([](auto& node) {
+    m_layout_root->for_each_in_inclusive_subtree([](auto& node) {
         node.reset_needs_layout_update();
         return TraversalDecision::Continue;
     });
@@ -1440,8 +1439,8 @@ void Document::update_layout(UpdateLayoutReason reason)
         }
         is_display_none = static_cast<Element&>(node).computed_properties()->display().is_none();
     }
-    if (node_invalidation.relayout) {
-        node.set_needs_layout_update(SetNeedsLayoutReason::StyleChange);
+    if (node_invalidation.relayout && node.layout_node()) {
+        node.layout_node()->set_needs_layout_update(SetNeedsLayoutReason::StyleChange);
     }
     if (node_invalidation.rebuild_layout_tree) {
         // We mark layout tree for rebuild starting from parent element to correctly invalidate

Libraries/LibWeb/DOM/Node.cpp

@@ -1418,7 +1418,8 @@ void Node::set_needs_layout_tree_update(bool value)
                 break;
             ancestor->m_child_needs_layout_tree_update = true;
         }
-        set_needs_layout_update(SetNeedsLayoutReason::LayoutTreeUpdate);
+        if (auto layout_node = this->layout_node())
+            layout_node->set_needs_layout_update(SetNeedsLayoutReason::LayoutTreeUpdate);
     }
 }
 
@@ -1438,27 +1439,6 @@ void Node::set_needs_style_update(bool value)
     }
 }
 
-void Node::set_needs_layout_update(SetNeedsLayoutReason reason)
-{
-    if (m_needs_layout_update)
-        return;
-
-    if constexpr (UPDATE_LAYOUT_DEBUG) {
-        // NOTE: We check some conditions here to avoid debug spam in documents that don't do layout.
-        auto navigable = this->navigable();
-        if (navigable && navigable->active_document() == &document())
-            dbgln_if(UPDATE_LAYOUT_DEBUG, "NEED LAYOUT {}", to_string(reason));
-    }
-
-    m_needs_layout_update = true;
-
-    for (auto* ancestor = parent_or_shadow_host(); ancestor; ancestor = ancestor->parent_or_shadow_host()) {
-        if (ancestor->m_needs_layout_update)
-            break;
-        ancestor->m_needs_layout_update = true;
-    }
-}
-
 void Node::post_connection()
 {
 }

Libraries/LibWeb/DOM/Node.h

@@ -316,10 +316,6 @@ public:
     void set_needs_style_update(bool);
     void set_needs_style_update_internal(bool) { m_needs_style_update = true; }
 
-    bool needs_layout_update() const { return m_needs_layout_update; }
-    void set_needs_layout_update(SetNeedsLayoutReason);
-    void reset_needs_layout_update() { m_needs_layout_update = false; }
-
     bool child_needs_style_update() const { return m_child_needs_style_update; }
     void set_child_needs_style_update(bool b) { m_child_needs_style_update = b; }
 
@@ -557,8 +553,6 @@ protected:
     bool m_child_needs_style_update { false };
     bool m_entire_subtree_needs_style_update { false };
 
-    bool m_needs_layout_update { false };
-
     UniqueNodeID m_unique_id;
 
     // https://dom.spec.whatwg.org/#registered-observer-list

Libraries/LibWeb/HTML/HTMLImageElement.cpp

@@ -763,7 +763,8 @@ void HTMLImageElement::add_callbacks_to_image_request(GC::Ref<ImageRequest> imag
                 document().list_of_available_images().add(key, *image_data, true);
 
                 set_needs_style_update(true);
-                set_needs_layout_update(DOM::SetNeedsLayoutReason::HTMLImageElementUpdateTheImageData);
+                if (auto layout_node = this->layout_node())
+                    layout_node->set_needs_layout_update(DOM::SetNeedsLayoutReason::HTMLImageElementUpdateTheImageData);
 
                 // 4. If maybe omit events is not set or previousURL is not equal to urlString, then fire an event named load at the img element.
                 if (!maybe_omit_events || previous_url != url_string.serialize())
@@ -903,7 +904,8 @@ void HTMLImageElement::react_to_changes_in_the_environment()
             image_request->prepare_for_presentation(*this);
             // FIXME: This is ad-hoc, updating the layout here should probably be handled by prepare_for_presentation().
             set_needs_style_update(true);
-            set_needs_layout_update(DOM::SetNeedsLayoutReason::HTMLImageElementReactToChangesInTheEnvironment);
+            if (auto layout_node = this->layout_node())
+                layout_node->set_needs_layout_update(DOM::SetNeedsLayoutReason::HTMLImageElementReactToChangesInTheEnvironment);
 
             // 7. Fire an event named load at the img element.
             dispatch_event(DOM::Event::create(realm(), HTML::EventNames::load));

Libraries/LibWeb/HTML/HTMLVideoElement.cpp

@@ -112,7 +112,8 @@ u32 HTMLVideoElement::video_height() const
 void HTMLVideoElement::set_video_track(GC::Ptr<HTML::VideoTrack> video_track)
 {
     set_needs_style_update(true);
-    set_needs_layout_update(DOM::SetNeedsLayoutReason::HTMLVideoElementSetVideoTrack);
+    if (auto layout_node = this->layout_node())
+        layout_node->set_needs_layout_update(DOM::SetNeedsLayoutReason::HTMLVideoElementSetVideoTrack);
 
     if (m_video_track)
         m_video_track->pause_video({});

Libraries/LibWeb/HTML/Navigable.cpp

@@ -42,6 +42,7 @@
 #include <LibWeb/HTML/WindowProxy.h>
 #include <LibWeb/Infra/Strings.h>
 #include <LibWeb/Layout/Node.h>
+#include <LibWeb/Layout/Viewport.h>
 #include <LibWeb/Loader/GeneratedPagesLoader.h>
 #include <LibWeb/Page/Page.h>
 #include <LibWeb/Painting/Paintable.h>
@@ -2165,7 +2166,8 @@ void finalize_a_cross_document_navigation(GC::Ref<Navigable> navigable, HistoryH
     // AD-HOC: If we're inside a navigable container, let's trigger a relayout in the container document.
     //         This allows size negotiation between the containing document and SVG documents to happen.
     if (auto container = navigable->container()) {
-        container->set_needs_layout_update(DOM::SetNeedsLayoutReason::FinalizeACrossDocumentNavigation);
+        if (auto layout_node = container->layout_node())
+            layout_node->set_needs_layout_update(DOM::SetNeedsLayoutReason::FinalizeACrossDocumentNavigation);
     }
 }
 
@@ -2288,7 +2290,8 @@ void Navigable::set_viewport_size(CSSPixelSize size)
     if (auto document = active_document()) {
         // NOTE: Resizing the viewport changes the reference value for viewport-relative CSS lengths.
         document->invalidate_style(DOM::StyleInvalidationReason::NavigableSetViewportSize);
-        document->set_needs_layout_update(DOM::SetNeedsLayoutReason::NavigableSetViewportSize);
+        if (auto layout_node = document->layout_node())
+            layout_node->set_needs_layout_update(DOM::SetNeedsLayoutReason::NavigableSetViewportSize);
     }
 
     if (auto document = active_document()) {

Libraries/LibWeb/Layout/Node.cpp

@@ -1281,4 +1281,25 @@ void NodeWithStyleAndBoxModelMetrics::visit_edges(Cell::Visitor& visitor)
     visitor.visit(m_continuation_of_node);
 }
 
+void Node::set_needs_layout_update(DOM::SetNeedsLayoutReason reason)
+{
+    if (m_needs_layout_update)
+        return;
+
+    if constexpr (UPDATE_LAYOUT_DEBUG) {
+        // NOTE: We check some conditions here to avoid debug spam in documents that don't do layout.
+        auto navigable = this->navigable();
+        if (navigable && navigable->active_document() == &document())
+            dbgln_if(UPDATE_LAYOUT_DEBUG, "NEED LAYOUT {}", DOM::to_string(reason));
+    }
+
+    m_needs_layout_update = true;
+
+    for (auto* ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
+        if (ancestor->m_needs_layout_update)
+            break;
+        ancestor->m_needs_layout_update = true;
+    }
+}
+
 }

Libraries/LibWeb/Layout/Node.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2023, Andreas Kling <andreas@ladybird.org>
+ * Copyright (c) 2018-2025, Andreas Kling <andreas@ladybird.org>
  * Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
@@ -45,6 +45,10 @@ public:
     DOM::Element const* pseudo_element_generator() const;
     DOM::Element* pseudo_element_generator();
 
+    bool needs_layout_update() const { return m_needs_layout_update; }
+    void set_needs_layout_update(DOM::SetNeedsLayoutReason);
+    void reset_needs_layout_update() { m_needs_layout_update = false; }
+
     bool is_generated() const { return m_generated_for.has_value(); }
     bool is_generated_for_before_pseudo_element() const { return m_generated_for == CSS::GeneratedPseudoElement::Before; }
     bool is_generated_for_after_pseudo_element() const { return m_generated_for == CSS::GeneratedPseudoElement::After; }
@@ -215,6 +219,8 @@ private:
 
     bool m_has_been_wrapped_in_table_wrapper { false };
 
+    bool m_needs_layout_update { false };
+
     Optional<CSS::GeneratedPseudoElement> m_generated_for {};
 
     u32 m_initial_quote_nesting_level { 0 };

Libraries/LibWeb/SVG/SVGImageElement.cpp

@@ -168,7 +168,8 @@ void SVGImageElement::fetch_the_document(URL::URL const& url)
                 m_animation_timer->start();
             }
             set_needs_style_update(true);
-            set_needs_layout_update(DOM::SetNeedsLayoutReason::SVGImageElementFetchTheDocument);
+            if (auto layout_node = this->layout_node())
+                layout_node->set_needs_layout_update(DOM::SetNeedsLayoutReason::SVGImageElementFetchTheDocument);
 
             dispatch_event(DOM::Event::create(realm(), HTML::EventNames::load));
         },