LibWeb: Fire slotchange events when a slot is changed

Author: https://github.com/shannonbooth
Commit: b543523717
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3871
Reviewed-by: https://github.com/trflynn89 ✅

Libraries/LibWeb/Bindings/MainThreadVM.cpp

@@ -28,6 +28,7 @@
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/HTML/CustomElements/CustomElementDefinition.h>
 #include <LibWeb/HTML/EventNames.h>
+#include <LibWeb/HTML/HTMLSlotElement.h>
 #include <LibWeb/HTML/Location.h>
 #include <LibWeb/HTML/PromiseRejectionEvent.h>
 #include <LibWeb/HTML/Scripting/Agent.h>
@@ -677,9 +678,9 @@ void queue_mutation_observer_microtask(DOM::Document const& document)
         for (auto& observer : surrounding_agent.mutation_observers)
             notify_set.append(&observer);
 
-        // FIXME: 3. Let signalSet be a clone of the surrounding agent’s signal slots.
-
-        // FIXME: 4. Empty the surrounding agent’s signal slots.
+        // 3. Let signalSet be a clone of the surrounding agent’s signal slots.
+        // 4. Empty the surrounding agent’s signal slots.
+        auto signal_set = move(surrounding_agent.signal_slots);
 
         // 5. For each mo of notifySet:
         for (auto& mutation_observer : notify_set) {
@@ -716,7 +717,12 @@ void queue_mutation_observer_microtask(DOM::Document const& document)
             }
         }
 
-        // FIXME: 6. For each slot of signalSet, fire an event named slotchange, with its bubbles attribute set to true, at slot.
+        // 6. For each slot of signalSet, fire an event named slotchange, with its bubbles attribute set to true, at slot.
+        for (auto& slot : signal_set) {
+            DOM::EventInit event_init;
+            event_init.bubbles = true;
+            slot->dispatch_event(DOM::Event::create(slot->realm(), HTML::EventNames::slotchange, event_init));
+        }
     }));
 }
 

Libraries/LibWeb/DOM/Slottable.cpp

@@ -206,7 +206,8 @@ void assign_a_slot(Slottable const& slottable)
 // https://dom.spec.whatwg.org/#signal-a-slot-change
 void signal_a_slot_change(GC::Ref<HTML::HTMLSlotElement> slottable)
 {
-    // FIXME: 1. Append slot to slot’s relevant agent’s signal slots.
+    // 1. Append slot to slot’s relevant agent’s signal slots.
+    HTML::relevant_agent(slottable).signal_slots.append(slottable);
 
     // 2. Queue a mutation observer microtask.
     Bindings::queue_mutation_observer_microtask(slottable->document());

Libraries/LibWeb/HTML/Scripting/Agent.h

@@ -32,6 +32,10 @@ struct Agent {
     // Each similar-origin window agent has a custom element reactions stack, which is initially empty.
     CustomElementReactionsStack custom_element_reactions_stack {};
 
+    // https://dom.spec.whatwg.org/#signal-slot-list
+    // Each similar-origin window agent has signal slots (a set of slots), which is initially empty. [HTML]
+    Vector<GC::Root<HTML::HTMLSlotElement>> signal_slots;
+
     // https://html.spec.whatwg.org/multipage/custom-elements.html#current-element-queue
     // A similar-origin window agent's current element queue is the element queue at the top of its custom element reactions stack.
     Vector<GC::Root<DOM::Element>>& current_element_queue() { return custom_element_reactions_stack.element_queue_stack.last(); }