From b190f2e1c92e8a8dd5161c91857e4e2779529e44 Mon Sep 17 00:00:00 2001
From: Andreas Kling <andreas@ladybird.org>
Date: Wed, 9 Apr 2025 20:57:35 +0200
Subject: [PATCH] LibWeb: Make Document::m_shadow_roots an IntrusiveList

This makes unregistering a ShadowRoot O(1) instead of O(n) and erases
a 2.2% item entirely from the Speedometer 2.1 profile.
---
 Libraries/LibWeb/DOM/Document.cpp | 9 ++++-----
 Libraries/LibWeb/DOM/Document.h   | 3 ++-
 Libraries/LibWeb/DOM/ShadowRoot.h | 5 +++++
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/Libraries/LibWeb/DOM/Document.cpp b/Libraries/LibWeb/DOM/Document.cpp
index 759c4dbd891..a159978c1f7 100644
--- a/Libraries/LibWeb/DOM/Document.cpp
+++ b/Libraries/LibWeb/DOM/Document.cpp
@@ -584,7 +584,8 @@ void Document::visit_edges(Cell::Visitor& visitor)
 
     visitor.visit(m_adopted_style_sheets);
 
-    visitor.visit(m_shadow_roots);
+    for (auto& shadow_root : m_shadow_roots)
+        visitor.visit(shadow_root);
 
     visitor.visit(m_top_layer_elements);
     visitor.visit(m_top_layer_pending_removals);
@@ -5953,9 +5954,7 @@ void Document::register_shadow_root(Badge<DOM::ShadowRoot>, DOM::ShadowRoot& sha
 
 void Document::unregister_shadow_root(Badge<DOM::ShadowRoot>, DOM::ShadowRoot& shadow_root)
 {
-    m_shadow_roots.remove_all_matching([&](auto& item) {
-        return item.ptr() == &shadow_root;
-    });
+    m_shadow_roots.remove(shadow_root);
 }
 
 void Document::for_each_shadow_root(Function<void(DOM::ShadowRoot&)>&& callback)
@@ -5967,7 +5966,7 @@ void Document::for_each_shadow_root(Function<void(DOM::ShadowRoot&)>&& callback)
 void Document::for_each_shadow_root(Function<void(DOM::ShadowRoot&)>&& callback) const
 {
     for (auto& shadow_root : m_shadow_roots)
-        callback(shadow_root);
+        callback(const_cast<ShadowRoot&>(shadow_root));
 }
 
 bool Document::is_decoded_svg() const
diff --git a/Libraries/LibWeb/DOM/Document.h b/Libraries/LibWeb/DOM/Document.h
index edd6c9c863a..4a11faaef7a 100644
--- a/Libraries/LibWeb/DOM/Document.h
+++ b/Libraries/LibWeb/DOM/Document.h
@@ -26,6 +26,7 @@
 #include <LibWeb/CSS/StyleSheetList.h>
 #include <LibWeb/Cookie/Cookie.h>
 #include <LibWeb/DOM/ParentNode.h>
+#include <LibWeb/DOM/ShadowRoot.h>
 #include <LibWeb/HTML/BrowsingContext.h>
 #include <LibWeb/HTML/CrossOrigin/OpenerPolicy.h>
 #include <LibWeb/HTML/DocumentReadyState.h>
@@ -1180,7 +1181,7 @@ private:
 
     mutable GC::Ptr<WebIDL::ObservableArray> m_adopted_style_sheets;
 
-    Vector<GC::Ref<DOM::ShadowRoot>> m_shadow_roots;
+    ShadowRoot::DocumentShadowRootList m_shadow_roots;
 
     Optional<Core::DateTime> m_last_modified;
 
diff --git a/Libraries/LibWeb/DOM/ShadowRoot.h b/Libraries/LibWeb/DOM/ShadowRoot.h
index b55b483fd2d..6093bae388b 100644
--- a/Libraries/LibWeb/DOM/ShadowRoot.h
+++ b/Libraries/LibWeb/DOM/ShadowRoot.h
@@ -97,6 +97,11 @@ private:
 
     GC::Ptr<CSS::StyleSheetList> m_style_sheets;
     mutable GC::Ptr<WebIDL::ObservableArray> m_adopted_style_sheets;
+
+    IntrusiveListNode<ShadowRoot> m_list_node;
+
+public:
+    using DocumentShadowRootList = IntrusiveList<&ShadowRoot::m_list_node>;
 };
 
 template<>