From cd4ea67706ea5cec24affea90eafed43c4013c1e Mon Sep 17 00:00:00 2001
From: Sam Atkins <sam@ladybird.org>
Date: Thu, 19 Jun 2025 15:03:50 +0100
Subject: [PATCH] LibWeb/DOM: Add custom-property helpers to AbstractElement

---
 Libraries/LibWeb/DOM/AbstractElement.cpp | 29 ++++++++++++++++++++++++
 Libraries/LibWeb/DOM/AbstractElement.h   |  4 ++++
 2 files changed, 33 insertions(+)

diff --git a/Libraries/LibWeb/DOM/AbstractElement.cpp b/Libraries/LibWeb/DOM/AbstractElement.cpp
index ad5143ddc17..54b5139d4eb 100644
--- a/Libraries/LibWeb/DOM/AbstractElement.cpp
+++ b/Libraries/LibWeb/DOM/AbstractElement.cpp
@@ -75,6 +75,35 @@ GC::Ptr<CSS::ComputedProperties const> AbstractElement::computed_properties() co
     return m_element->computed_properties();
 }
 
+HashMap<FlyString, CSS::StyleProperty> const& AbstractElement::custom_properties() const
+{
+    return m_element->custom_properties(m_pseudo_element);
+}
+
+void AbstractElement::set_custom_properties(HashMap<FlyString, CSS::StyleProperty>&& custom_properties)
+{
+    m_element->set_custom_properties(m_pseudo_element, move(custom_properties));
+}
+
+RefPtr<CSS::CSSStyleValue const> AbstractElement::get_custom_property(FlyString const& name) const
+{
+    // FIXME: We should be producing computed values for custom properties, just like regular properties.
+    if (m_pseudo_element.has_value()) {
+        auto const& custom_properties = m_element->custom_properties(*m_pseudo_element);
+        if (auto it = custom_properties.find(name); it != custom_properties.end()) {
+            return it->value.value;
+        }
+    }
+
+    for (auto const* current_element = m_element.ptr(); current_element; current_element = current_element->parent_or_shadow_host_element()) {
+        auto const& custom_properties = current_element->custom_properties({});
+        if (auto it = custom_properties.find(name); it != custom_properties.end()) {
+            return it->value.value;
+        }
+    }
+    return nullptr;
+}
+
 bool AbstractElement::has_non_empty_counters_set() const
 {
     if (m_pseudo_element.has_value())
diff --git a/Libraries/LibWeb/DOM/AbstractElement.h b/Libraries/LibWeb/DOM/AbstractElement.h
index b8b1e1bfa7c..f5076ece11f 100644
--- a/Libraries/LibWeb/DOM/AbstractElement.h
+++ b/Libraries/LibWeb/DOM/AbstractElement.h
@@ -31,6 +31,10 @@ public:
 
     GC::Ptr<CSS::ComputedProperties const> computed_properties() const;
 
+    void set_custom_properties(HashMap<FlyString, CSS::StyleProperty>&& custom_properties);
+    [[nodiscard]] HashMap<FlyString, CSS::StyleProperty> const& custom_properties() const;
+    RefPtr<CSS::CSSStyleValue const> get_custom_property(FlyString const& name) const;
+
     bool has_non_empty_counters_set() const;
     Optional<CSS::CountersSet const&> counters_set() const;
     CSS::CountersSet& ensure_counters_set();