From 37ea9a4ce3fda051dd991f84a79ebc47fef5da52 Mon Sep 17 00:00:00 2001
From: Sam Atkins <sam@ladybird.org>
Date: Wed, 13 Aug 2025 13:07:28 +0100
Subject: [PATCH] LibWeb/CSS: Add `has_property()` to CSSStyleDeclaration

This isn't part of the CSSOM API directly, but will be used by
StylePropertyMapReadOnly.has() to avoid doing the work to serialize a
string version of the property's value, just to throw it away again.
---
 Libraries/LibWeb/CSS/CSSDescriptors.cpp     | 8 ++++++++
 Libraries/LibWeb/CSS/CSSDescriptors.h       | 2 ++
 Libraries/LibWeb/CSS/CSSStyleDeclaration.h  | 2 ++
 Libraries/LibWeb/CSS/CSSStyleProperties.cpp | 8 ++++++++
 Libraries/LibWeb/CSS/CSSStyleProperties.h   | 2 ++
 5 files changed, 22 insertions(+)

diff --git a/Libraries/LibWeb/CSS/CSSDescriptors.cpp b/Libraries/LibWeb/CSS/CSSDescriptors.cpp
index 425003c9845..e7415a93bee 100644
--- a/Libraries/LibWeb/CSS/CSSDescriptors.cpp
+++ b/Libraries/LibWeb/CSS/CSSDescriptors.cpp
@@ -281,6 +281,14 @@ RefPtr<StyleValue const> CSSDescriptors::descriptor_or_initial_value(DescriptorI
     return descriptor_initial_value(m_at_rule_id, descriptor_id);
 }
 
+bool CSSDescriptors::has_property(StringView property_name) const
+{
+    auto descriptor_id = descriptor_id_from_string(m_at_rule_id, property_name);
+    if (!descriptor_id.has_value())
+        return false;
+    return descriptor(*descriptor_id) != nullptr;
+}
+
 bool is_shorthand(AtRuleID at_rule, DescriptorID descriptor)
 {
     if (at_rule == AtRuleID::Page && descriptor == DescriptorID::Margin)
diff --git a/Libraries/LibWeb/CSS/CSSDescriptors.h b/Libraries/LibWeb/CSS/CSSDescriptors.h
index 3749465a9ae..1da05ad8ddb 100644
--- a/Libraries/LibWeb/CSS/CSSDescriptors.h
+++ b/Libraries/LibWeb/CSS/CSSDescriptors.h
@@ -33,6 +33,8 @@ public:
 
     virtual WebIDL::ExceptionOr<void> set_css_text(StringView) override;
 
+    virtual bool has_property(StringView property_name) const override;
+
 protected:
     CSSDescriptors(JS::Realm&, AtRuleID, Vector<Descriptor>);
 
diff --git a/Libraries/LibWeb/CSS/CSSStyleDeclaration.h b/Libraries/LibWeb/CSS/CSSStyleDeclaration.h
index 6bcb8ee322e..8f29294e46e 100644
--- a/Libraries/LibWeb/CSS/CSSStyleDeclaration.h
+++ b/Libraries/LibWeb/CSS/CSSStyleDeclaration.h
@@ -57,6 +57,8 @@ public:
     [[nodiscard]] bool is_updating() const { return m_updating; }
     void set_is_updating(bool value) { m_updating = value; }
 
+    virtual bool has_property(StringView property_name) const = 0;
+
 protected:
     enum class Computed : u8 {
         No,
diff --git a/Libraries/LibWeb/CSS/CSSStyleProperties.cpp b/Libraries/LibWeb/CSS/CSSStyleProperties.cpp
index 16b938fd24f..a03bf863c8d 100644
--- a/Libraries/LibWeb/CSS/CSSStyleProperties.cpp
+++ b/Libraries/LibWeb/CSS/CSSStyleProperties.cpp
@@ -426,6 +426,14 @@ StringView CSSStyleProperties::get_property_priority(StringView property_name) c
     return maybe_property->important == Important::Yes ? "important"sv : ""sv;
 }
 
+bool CSSStyleProperties::has_property(StringView property_name) const
+{
+    auto property_id = property_id_from_string(property_name);
+    if (!property_id.has_value())
+        return false;
+    return get_property_internal(*property_id).has_value();
+}
+
 // https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-getpropertyvalue
 Optional<StyleProperty> CSSStyleProperties::get_property_internal(PropertyID property_id) const
 {
diff --git a/Libraries/LibWeb/CSS/CSSStyleProperties.h b/Libraries/LibWeb/CSS/CSSStyleProperties.h
index 1d6c8050b35..22f9be74f5b 100644
--- a/Libraries/LibWeb/CSS/CSSStyleProperties.h
+++ b/Libraries/LibWeb/CSS/CSSStyleProperties.h
@@ -49,6 +49,8 @@ public:
 
     size_t custom_property_count() const { return m_custom_properties.size(); }
 
+    virtual bool has_property(StringView property_name) const override;
+
     String css_float() const;
     WebIDL::ExceptionOr<void> set_css_float(StringView);