Web Animations CSS: Implement CSS Transitions backed on Web Animations model

Source/core/animation/ActiveAnimations.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 26 matching lines @@
 #include "wtf/RefPtr.h"
 #include "wtf/Vector.h"
 
 namespace WebCore {
 
 class ActiveAnimations {
 public:
     // Animations that are currently active for this element, their effects will be applied
     // during a style recalc.
     AnimationStack* defaultStack() { return &m_defaultStack; }
-    // Tracks the state of active CSS Animations. The individual animations will also be
-    // part of the default stack, but the mapping betwen animation name and player is kept
-    // here.
+    // Tracks the state of active CSS Animations and Transitions. The individual animations
+    // will also be part of the default stack, but the mapping betwen animation name and
+    // player is kept here.
     CSSAnimations* cssAnimations() { return &m_cssAnimations; }

[Steve Block, 2013/10/09 00:57:12]

It sounds like you plan to add a separate stack for transitions, so isn't the
FIXME still valid?

[Timothy Loh, 2013/10/09 07:39:23]

See comment at top of this reply.

-    // FIXME: Add AnimationStack for CSS Transitions
-    // CSS Transitions form a separate animation stack as they apply at a different level of
-    // the style cascade. Active transitions will not be present in the default stack.
     bool isEmpty() const { return m_defaultStack.isEmpty() && m_cssAnimations.isEmpty(); }

[Steve Block, 2013/10/09 00:57:12]

If I understand correctly, m_defaultStack should always contain at least as many
elements as m_cssAnimations, so isn't it sufficient to check
m_defaultStack.isEmpty()?

[Timothy Loh, 2013/10/09 07:39:23]

I'm not sure where this gets called but the CSSAnimations object can be nonempty
due to holding an update object.

 private:
     AnimationStack m_defaultStack;
     CSSAnimations m_cssAnimations;
 };
 
 } // namespace WebCore
 
 #endif