LibWeb: Only store one DOM pointer per Layout::Node

Instead of storing two JS::Handles into the DOM, we can combine them
into a single one.

If the layout node is anonymous, m_dom_node points to the DOM::Document.
Otherwise, m_dom_node points to the associated DOM node.

The anonymous state is moved to an m_anonymous boolean member.

This cuts the number of JS::Handles created by the layout tree in half
(and shrinks Layout::Node by 8 bytes).

2 files changed, 14 insertions, 10 deletions

diff --git a/Userland/Libraries/LibWeb/Layout/Node.cpp b/Userland/Libraries/LibWeb/Layout/Node.cpp
index bcca562761..4a0838af27 100644
--- a/Userland/Libraries/LibWeb/Layout/Node.cpp
+++ b/Userland/Libraries/LibWeb/Layout/Node.cpp
@@ -20,18 +20,18 @@
 namespace Web::Layout {
 
 Node::Node(DOM::Document& document, DOM::Node* node)
-    : m_document(document)
-    , m_dom_node(node)
+    : m_dom_node(node ? node : &document)
+    , m_anonymous(node == nullptr)
 {
-    m_serial_id = m_document->next_layout_node_serial_id({});
+    m_serial_id = document.next_layout_node_serial_id({});
 
-    if (m_dom_node)
-        m_dom_node->set_layout_node({}, this);
+    if (node)
+        node->set_layout_node({}, this);
 }
 
 Node::~Node()
 {
-    if (m_dom_node && m_dom_node->layout_node() == this)
+    if (!is_anonymous() && m_dom_node->layout_node() == this)
         m_dom_node->set_layout_node({}, nullptr);
 }
 
@@ -625,27 +625,31 @@ RefPtr<Painting::Paintable> Node::create_paintable() const
 
 bool Node::is_anonymous() const
 {
-    return !m_dom_node.ptr();
+    return m_anonymous;
 }
 
 DOM::Node const* Node::dom_node() const
 {
+    if (m_anonymous)
+        return nullptr;
     return m_dom_node.ptr();
 }
 
 DOM::Node* Node::dom_node()
 {
+    if (m_anonymous)
+        return nullptr;
     return m_dom_node.ptr();
 }
 
 DOM::Document& Node::document()
 {
-    return *m_document;
+    return m_dom_node->document();
 }
 
 DOM::Document const& Node::document() const
 {
-    return *m_document;
+    return m_dom_node->document();
 }
 
 }
diff --git a/Userland/Libraries/LibWeb/Layout/Node.h b/Userland/Libraries/LibWeb/Layout/Node.h
index 3a7b9db406..e8ca0bfe1b 100644
--- a/Userland/Libraries/LibWeb/Layout/Node.h
+++ b/Userland/Libraries/LibWeb/Layout/Node.h
@@ -143,12 +143,12 @@ protected:
 private:
     friend class NodeWithStyle;
 
-    JS::Handle<DOM::Document> m_document;
     JS::Handle<DOM::Node> m_dom_node;
     RefPtr<Painting::Paintable> m_paintable;
 
     size_t m_serial_id { 0 };
 
+    bool m_anonymous { false };
     bool m_has_style { false };
     bool m_visible { true };
     bool m_children_are_inline { false };