LibWeb: Add shared layout node storage for Rust

Libraries/LibWeb/CMakeLists.txt

@@ -825,6 +825,7 @@ set(SOURCES
     Layout/ListItemMarkerBox.cpp
     Layout/NavigableContainerViewport.cpp
     Layout/Node.cpp
+    Layout/NodeArena.cpp
     Layout/RadioButton.cpp
     Layout/RangeInputBox.cpp
     Layout/ReplacedBox.cpp

Libraries/LibWeb/DOM/Document.cpp

@@ -188,6 +188,7 @@
 #include <LibWeb/Infra/Strings.h>
 #include <LibWeb/IntersectionObserver/IntersectionObserver.h>
 #include <LibWeb/Layout/BlockFormattingContext.h>
+#include <LibWeb/Layout/NodeArena.h>
 #include <LibWeb/Layout/SVGFormattingContext.h>
 #include <LibWeb/Layout/SVGSVGBox.h>
 #include <LibWeb/Layout/ScrollableOverflow.h>
@@ -619,6 +620,15 @@ Document::Document(JS::Realm& realm, URL::URL const& url)
 
 Document::~Document() = default;
 
+Layout::NodeArena& Document::layout_node_arena()
+{
+    // Created on first layout node so documents that never build a layout tree (e.g. temporary
+    // fragment-parsing documents) skip the Rust arena round-trip entirely.
+    if (!m_layout_node_arena)
+        m_layout_node_arena = make_ref_counted<Layout::NodeArena>();
+    return *m_layout_node_arena;
+}
+
 void Document::set_temporary_document_for_fragment_parsing(Badge<HTML::HTMLParser>)
 {
     // https://html.spec.whatwg.org/multipage/parsing.html#html-fragment-parsing-algorithm

Libraries/LibWeb/DOM/Document.h

@@ -746,6 +746,7 @@ class WEB_API Document
     // one at construction; a full layout pass renumbers the whole tree densely and resets the
     // counter past the dense range.
     [[nodiscard]] u32 allocate_layout_node_index() { return m_next_layout_node_index++; }
+    [[nodiscard]] Layout::NodeArena& layout_node_arena();
     void reset_layout_node_index_counter(u32 next_index)
     {
         m_next_layout_node_index = next_index;
@@ -1422,6 +1423,7 @@ class WEB_API Document
 
     GC::Ptr<HTML::Window> m_window;
 
+    RefPtr<Layout::NodeArena> m_layout_node_arena;
     RefPtr<Layout::Viewport> m_layout_root;
 
     GC::Ptr<Node> m_hovered_node;

Libraries/LibWeb/Forward.h

@@ -986,6 +986,7 @@ class LineBoxFragment;
 class ListItemBox;
 class ListItemMarkerBox;
 class Node;
+class NodeArena;
 class NodeWithStyle;
 class NodeWithStyleAndBoxModelMetrics;
 class RadioButton;

Libraries/LibWeb/Layout/AudioBox.h

@@ -13,8 +13,7 @@
 namespace Web::Layout {
 
 class AudioBox final : public ReplacedBox {
-    GC_CELL(AudioBox, ReplacedBox);
-    GC_DECLARE_ALLOCATOR(AudioBox);
+    LAYOUT_NODE(AudioBox, ReplacedBox);
 
 public:
     AudioBox(DOM::Document&, DOM::Element&, NonnullRefPtr<CSS::ComputedValues const>);

Libraries/LibWeb/Layout/Box.h

@@ -44,8 +44,7 @@ struct IntrinsicSizes {
 };
 
 class WEB_API Box : public NodeWithStyleAndBoxModelMetrics {
-    GC_CELL(Box, NodeWithStyleAndBoxModelMetrics);
-    GC_DECLARE_ALLOCATOR(Box);
+    LAYOUT_NODE(Box, NodeWithStyleAndBoxModelMetrics);
 
 public:
     RefPtr<Painting::Paintable const> paintable_box() const;
@@ -87,18 +86,18 @@ class WEB_API Box : public NodeWithStyleAndBoxModelMetrics {
     // Whether an absolutely or fixed positioned descendant of this box has its containing
     // block outside this box's subtree, so the descendant's layout escapes the subtree.
     // Re-derived whenever containing block pointers are recomputed.
-    bool abspos_descendant_escapes() const { return m_abspos_descendant_escapes; }
-    void set_abspos_descendant_escapes(bool value) { m_abspos_descendant_escapes = value; }
+    bool abspos_descendant_escapes() const { return has_flag(RustFFI::NodeFlag::AbsposDescendantEscapes); }
+    void set_abspos_descendant_escapes(bool value) { set_flag(RustFFI::NodeFlag::AbsposDescendantEscapes, value); }
 
     void set_default_scroll_shift(WeakPtr<Node> anchor, bool compensates_for_horizontal_scroll, bool compensates_for_vertical_scroll)
     {
         m_default_scroll_shift_anchor = move(anchor);
-        m_compensates_for_horizontal_scroll = compensates_for_horizontal_scroll;
-        m_compensates_for_vertical_scroll = compensates_for_vertical_scroll;
+        set_flag(RustFFI::NodeFlag::CompensatesForHorizontalScroll, compensates_for_horizontal_scroll);
+        set_flag(RustFFI::NodeFlag::CompensatesForVerticalScroll, compensates_for_vertical_scroll);
     }
     Node* default_scroll_shift_anchor() const { return m_default_scroll_shift_anchor.ptr(); }
-    bool compensates_for_horizontal_scroll() const { return m_compensates_for_horizontal_scroll; }
-    bool compensates_for_vertical_scroll() const { return m_compensates_for_vertical_scroll; }
+    bool compensates_for_horizontal_scroll() const { return has_flag(RustFFI::NodeFlag::CompensatesForHorizontalScroll); }
+    bool compensates_for_vertical_scroll() const { return has_flag(RustFFI::NodeFlag::CompensatesForVerticalScroll); }
 
     IntrinsicSizes& cached_intrinsic_sizes() const
     {
@@ -119,9 +118,6 @@ class WEB_API Box : public NodeWithStyleAndBoxModelMetrics {
     OwnPtr<AbsposLayoutInputs> m_saved_abspos_layout_inputs;
 
     WeakPtr<Node> m_default_scroll_shift_anchor;
-    bool m_compensates_for_horizontal_scroll { false };
-    bool m_compensates_for_vertical_scroll { false };
-    bool m_abspos_descendant_escapes { false };
 
     OwnPtr<IntrinsicSizes> mutable m_cached_intrinsic_sizes;
 };