LibWeb: Correctly sort animations returned by getAnimations()

Author: https://github.com/Psychpsyo
Commit: b7a71ca950
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6777
Reviewed-by: https://github.com/gmta ✅

Libraries/LibWeb/Animations/KeyframeEffect.cpp

@@ -627,11 +627,12 @@ void KeyframeEffect::generate_initial_and_final_frames(RefPtr<KeyFrameSet> keyfr
 // https://www.w3.org/TR/web-animations-1/#animation-composite-order
 int KeyframeEffect::composite_order(GC::Ref<KeyframeEffect> a, GC::Ref<KeyframeEffect> b)
 {
-    // 1. Let the associated animation of an animation effect be the animation associated with the animation effect.
+    // The relative composite order of any two keyframe effects A and B within an effect stack is established by
+    // comparing their properties as follows:
     auto a_animation = a->associated_animation();
     auto b_animation = b->associated_animation();
 
-    // 2. Sort A and B by applying the following conditions in turn until the order is resolved,
+    // 1. Sort A and B by applying the following conditions in turn until the order is resolved,
 
     //    1. If A and B’s associated animations differ by class, sort by any inter-class composite order defined for
     //       the corresponding classes.

Libraries/LibWeb/DOM/Document.cpp

@@ -5472,12 +5472,7 @@ void Document::remove_replaced_animations()
 
 WebIDL::ExceptionOr<Vector<GC::Ref<Animations::Animation>>> Document::get_animations()
 {
-    Vector<GC::Ref<Animations::Animation>> relevant_animations;
-    TRY(for_each_child_of_type_fallible<Element>([&](auto& child) -> WebIDL::ExceptionOr<IterationDecision> {
-        relevant_animations.extend(TRY(child.get_animations(Animations::GetAnimationsOptions { .subtree = true })));
-        return IterationDecision::Continue;
-    }));
-    return relevant_animations;
+    return calculate_get_animations(*this);
 }
 
 // https://html.spec.whatwg.org/multipage/dom.html#dom-document-nameditem-filter

Libraries/LibWeb/DOM/DocumentOrShadowRoot.h

@@ -7,6 +7,7 @@
 
 #pragma once
 
+#include <LibWeb/Animations/Animation.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Utils.h>
 
@@ -47,4 +48,32 @@ GC::Ptr<Element> calculate_active_element(T& self)
     return nullptr;
 }
 
+// https://drafts.csswg.org/web-animations-1/#dom-documentorshadowroot-getanimations
+template<DocumentOrShadowRoot T>
+WebIDL::ExceptionOr<Vector<GC::Ref<Animations::Animation>>> calculate_get_animations(T& self)
+{
+    // Returns the set of relevant animations for a subtree for the document or shadow root on which this
+    // method is called.
+    Vector<GC::Ref<Animations::Animation>> relevant_animations;
+    TRY(self.template for_each_child_of_type_fallible<Element>([&](auto& child) -> WebIDL::ExceptionOr<IterationDecision> {
+        relevant_animations.extend(TRY(child.get_animations(Animations::GetAnimationsOptions { .subtree = true })));
+        return IterationDecision::Continue;
+    }));
+
+    // The returned list is sorted using the composite order described for the associated animations of
+    // effects in § 5.4.2 The effect stack.
+    quick_sort(relevant_animations, [](GC::Ref<Animations::Animation>& a, GC::Ref<Animations::Animation>& b) {
+        auto& a_effect = as<Animations::KeyframeEffect>(*a->effect());
+        auto& b_effect = as<Animations::KeyframeEffect>(*b->effect());
+        return Animations::KeyframeEffect::composite_order(a_effect, b_effect) < 0;
+    });
+
+    // Calling this method triggers a style change event for the document. As a result, the returned list
+    // reflects the state after applying any pending style changes to animation such as changes to
+    // animation-related style properties that have yet to be processed.
+    // FIXME: Implement this.
+
+    return relevant_animations;
+}
+
 }

Libraries/LibWeb/DOM/ShadowRoot.cpp

@@ -198,12 +198,7 @@ void ShadowRoot::for_each_css_style_sheet(Function<void(CSS::CSSStyleSheet&)>&&
 
 WebIDL::ExceptionOr<Vector<GC::Ref<Animations::Animation>>> ShadowRoot::get_animations()
 {
-    Vector<GC::Ref<Animations::Animation>> relevant_animations;
-    TRY(for_each_child_of_type_fallible<Element>([&](auto& child) -> WebIDL::ExceptionOr<IterationDecision> {
-        relevant_animations.extend(TRY(child.get_animations(Animations::GetAnimationsOptions { .subtree = true })));
-        return IterationDecision::Continue;
-    }));
-    return relevant_animations;
+    return calculate_get_animations(*this);
 }
 
 ElementByIdMap& ShadowRoot::element_by_id() const