LibWeb: Give Element a CustomStateSet, exposed by ElementInternals

Author: https://github.com/AtkinsSJ
Commit: b6ffea8990
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5302
Reviewed-by: https://github.com/tcl3 ✅

Libraries/LibWeb/DOM/Element.cpp

@@ -46,6 +46,7 @@
 #include <LibWeb/HTML/CustomElements/CustomElementName.h>
 #include <LibWeb/HTML/CustomElements/CustomElementReactionNames.h>
 #include <LibWeb/HTML/CustomElements/CustomElementRegistry.h>
+#include <LibWeb/HTML/CustomElements/CustomStateSet.h>
 #include <LibWeb/HTML/EventLoop/EventLoop.h>
 #include <LibWeb/HTML/HTMLAnchorElement.h>
 #include <LibWeb/HTML/HTMLAreaElement.h>
@@ -118,6 +119,7 @@ void Element::visit_edges(Cell::Visitor& visitor)
     visitor.visit(m_class_list);
     visitor.visit(m_shadow_root);
     visitor.visit(m_custom_element_definition);
+    visitor.visit(m_custom_state_set);
     visitor.visit(m_cascaded_properties);
     visitor.visit(m_computed_properties);
     if (m_pseudo_element_data) {
@@ -3824,6 +3826,13 @@ auto Element::ensure_custom_element_reaction_queue() -> CustomElementReactionQue
     return *m_custom_element_reaction_queue;
 }
 
+HTML::CustomStateSet& Element::ensure_custom_state_set()
+{
+    if (!m_custom_state_set)
+        m_custom_state_set = HTML::CustomStateSet::create(realm(), *this);
+    return *m_custom_state_set;
+}
+
 CSS::StyleSheetList& Element::document_or_shadow_root_style_sheets()
 {
     auto& root_node = root();

Libraries/LibWeb/DOM/Element.h

@@ -351,6 +351,9 @@ public:
     CustomElementReactionQueue const* custom_element_reaction_queue() const { return m_custom_element_reaction_queue; }
     CustomElementReactionQueue& ensure_custom_element_reaction_queue();
 
+    HTML::CustomStateSet const* custom_state_set() const { return m_custom_state_set; }
+    HTML::CustomStateSet& ensure_custom_state_set();
+
     JS::ThrowCompletionOr<void> upgrade_element(GC::Ref<HTML::CustomElementDefinition> custom_element_definition);
     void try_to_upgrade();
 
@@ -587,6 +590,9 @@ private:
     // https://dom.spec.whatwg.org/#concept-element-is-value
     Optional<String> m_is_value;
 
+    // https://html.spec.whatwg.org/multipage/custom-elements.html#states-set
+    GC::Ptr<HTML::CustomStateSet> m_custom_state_set;
+
     // https://www.w3.org/TR/intersection-observer/#dom-element-registeredintersectionobservers-slot
     // Element objects have an internal [[RegisteredIntersectionObservers]] slot, which is initialized to an empty list.
     OwnPtr<Vector<IntersectionObserver::IntersectionObserverRegistration>> m_registered_intersection_observers;

Libraries/LibWeb/HTML/ElementInternals.cpp

@@ -208,6 +208,13 @@ WebIDL::ExceptionOr<GC::Ptr<DOM::NodeList>> ElementInternals::labels()
     return WebIDL::NotSupportedError::create(realm(), "FIXME: ElementInternals::labels()"_string);
 }
 
+// https://html.spec.whatwg.org/multipage/custom-elements.html#dom-elementinternals-states
+GC::Ptr<CustomStateSet> ElementInternals::states()
+{
+    // The states getter steps are to return this's target element's states set.
+    return m_target_element->ensure_custom_state_set();
+}
+
 void ElementInternals::initialize(JS::Realm& realm)
 {
     WEB_SET_PROTOTYPE_FOR_INTERFACE(ElementInternals);

Libraries/LibWeb/HTML/ElementInternals.h

@@ -57,6 +57,7 @@ public:
     WebIDL::ExceptionOr<bool> report_validity() const;
 
     WebIDL::ExceptionOr<GC::Ptr<DOM::NodeList>> labels();
+    GC::Ptr<CustomStateSet> states();
 
 private:
     explicit ElementInternals(JS::Realm&, HTMLElement& target_element);

Libraries/LibWeb/HTML/ElementInternals.idl

@@ -1,4 +1,5 @@
 #import <DOM/ShadowRoot.idl>
+#import <HTML/CustomElements/CustomStateSet.idl>
 
 // https://html.spec.whatwg.org/multipage/custom-elements.html#elementinternals
 [Exposed=Window]
@@ -24,7 +25,7 @@ interface ElementInternals {
     readonly attribute NodeList labels;
 
     // Custom state pseudo-class
-    [FIXME, SameObject] readonly attribute CustomStateSet states;
+    [SameObject] readonly attribute CustomStateSet states;
 };
 
 // Accessibility semantics