From 37505d9746439c4b44f61566bbab899ddce64ee0 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 19 Nov 2023 20:20:34 +0100
Subject: [PATCH] LibWeb: Allocate storage for pseudo element custom properties
 on demand

Most elements don't have pseudo elements with CSS custom properties.
By only allocating this data structure when it's used, we can shrink
most elements by 208 bytes each. :^)
---
 Userland/Libraries/LibWeb/DOM/Element.cpp | 11 +++++++++--
 Userland/Libraries/LibWeb/DOM/Element.h   |  5 ++++-
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/Userland/Libraries/LibWeb/DOM/Element.cpp b/Userland/Libraries/LibWeb/DOM/Element.cpp
index 6ebe538322..a9be123ef1 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Element.cpp
@@ -2050,20 +2050,27 @@ void Element::set_computed_css_values(RefPtr<CSS::StyleProperties> style)
     m_computed_css_values = move(style);
 }
 
+auto Element::pseudo_element_custom_properties() const -> PseudoElementCustomProperties&
+{
+    if (!m_pseudo_element_custom_properties)
+        m_pseudo_element_custom_properties = make<PseudoElementCustomProperties>();
+    return *m_pseudo_element_custom_properties;
+}
+
 void Element::set_custom_properties(Optional<CSS::Selector::PseudoElement> pseudo_element, HashMap<FlyString, CSS::StyleProperty> custom_properties)
 {
     if (!pseudo_element.has_value()) {
         m_custom_properties = move(custom_properties);
         return;
     }
-    m_pseudo_element_custom_properties[to_underlying(pseudo_element.value())] = move(custom_properties);
+    pseudo_element_custom_properties()[to_underlying(pseudo_element.value())] = move(custom_properties);
 }
 
 HashMap<FlyString, CSS::StyleProperty> const& Element::custom_properties(Optional<CSS::Selector::PseudoElement> pseudo_element) const
 {
     if (!pseudo_element.has_value())
         return m_custom_properties;
-    return m_pseudo_element_custom_properties[to_underlying(pseudo_element.value())];
+    return pseudo_element_custom_properties()[to_underlying(pseudo_element.value())];
 }
 
 // https://drafts.csswg.org/cssom-view/#dom-element-scroll
diff --git a/Userland/Libraries/LibWeb/DOM/Element.h b/Userland/Libraries/LibWeb/DOM/Element.h
index 9948d396e1..1375a66246 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.h
+++ b/Userland/Libraries/LibWeb/DOM/Element.h
@@ -402,7 +402,10 @@ private:
 
     RefPtr<CSS::StyleProperties> m_computed_css_values;
     HashMap<FlyString, CSS::StyleProperty> m_custom_properties;
-    Array<HashMap<FlyString, CSS::StyleProperty>, to_underlying(CSS::Selector::PseudoElement::PseudoElementCount)> m_pseudo_element_custom_properties;
+
+    using PseudoElementCustomProperties = Array<HashMap<FlyString, CSS::StyleProperty>, to_underlying(CSS::Selector::PseudoElement::PseudoElementCount)>;
+    mutable OwnPtr<PseudoElementCustomProperties> m_pseudo_element_custom_properties;
+    PseudoElementCustomProperties& pseudo_element_custom_properties() const;
 
     Vector<FlyString> m_classes;
     Optional<Dir> m_dir;