Web Animations: Fix CSS events to handle animations with very short durations

Source/core/animation/TimedItem.cpp

 /*
  * 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 23 matching lines @@
 
 namespace WebCore {
 
 TimedItem::TimedItem(const Timing& timing, PassOwnPtr<TimedItemEventDelegate> eventDelegate)
     : m_parent(0)
     , m_player(0)
     , m_startTime(0)
     , m_specified(timing)
     , m_calculated()
     , m_eventDelegate(eventDelegate)
+    , m_isFirstSample(true)
 {
     timing.assertValid();
 }
 
 void TimedItem::updateInheritedTime(double inheritedTime) const
 {
     const double localTime = inheritedTime - m_startTime;
     const double iterationDuration = m_specified.hasIterationDuration
         ? m_specified.iterationDuration
         : intrinsicIterationDuration();
@@ skipping 25 matching lines @@
         const double newLocalTime = localTime < m_specified.startDelay ? m_specified.startDelay - 1 : activeDuration + m_specified.startDelay;
         const TimedItem::Phase phase = calculatePhase(activeDuration, newLocalTime, m_specified);
         const double activeTime = calculateActiveTime(activeDuration, newLocalTime, parentPhase, phase, m_specified);
         const double startOffset = m_specified.iterationStart * iterationDuration;
         const double scaledActiveTime = calculateScaledActiveTime(activeDuration, activeTime, startOffset, m_specified);
         const double iterationTime = calculateIterationTime(iterationDuration, repeatedDuration, scaledActiveTime, startOffset, m_specified);
 
         currentIteration = calculateCurrentIteration(iterationDuration, iterationTime, scaledActiveTime, m_specified);
         timeFraction = calculateTransformedTime(currentIteration, iterationDuration, iterationTime, m_specified);
     }
-
-    const double lastIteration = m_calculated.currentIteration;
-    m_calculated.currentIteration = currentIteration;
     m_calculated.activeDuration = activeDuration;
     m_calculated.timeFraction = timeFraction;
 
+    const bool newIsInPlay = phase == PhaseActive && (!m_parent || m_parent->isInPlay());
+    const bool newIsCurrent = phase == PhaseBefore || newIsInPlay || (m_parent && m_parent->isCurrent());
+
     const bool wasInEffect = m_calculated.isInEffect;
-    const bool wasInPlay = m_calculated.isInPlay;
     m_calculated.isInEffect = !isNull(activeTime);
-    m_calculated.isInPlay = phase == PhaseActive && (!m_parent || m_parent->isInPlay());
-    m_calculated.isCurrent = phase == PhaseBefore || isInPlay() || (m_parent && m_parent->isCurrent());
 
     // This logic is specific to CSS events and assumes that all animations
     // start after the DocumentTimeline has started.
-    if (m_eventDelegate && (isInPlay() != wasInPlay || (isInPlay() && lastIteration != currentIteration)))
-        m_eventDelegate->onEventCondition(wasInPlay, isInPlay(), lastIteration, currentIteration);
+
+    // If this is the first sample, fake the values for the previous sample to
+    // avoid spurious events.
+    const double lastIteration = m_isFirstSample ? currentIteration : m_calculated.currentIteration;
+    const bool wasInPlay = m_isFirstSample ? newIsInPlay : m_calculated.isInPlay;
+    const bool wasCurrent = m_isFirstSample ? newIsCurrent : m_calculated.isCurrent;
+    m_isFirstSample = false;
+
+    m_calculated.currentIteration = currentIteration;
+    m_calculated.isInPlay = newIsInPlay;
+    m_calculated.isCurrent = newIsCurrent;
+
+    if (m_eventDelegate && (isInPlay() != wasInPlay || isCurrent() != wasCurrent || (wasInPlay && isInPlay() && lastIteration != currentIteration)))

[dstockwell, 2013/08/21 02:29:44]

This is getting complicated. I wonder if instead of looking at a change to
isCurrent (and perhaps even isInPlay) whether we can get by just looking at
changes to the phase (and iteration)? This might also avoid needing that first
forced sample.

I think None -> !None = started. !After -> After = finished.

[dstockwell, 2013/08/21 04:37:36]

Oops, I guess that's: None -> (Active | After) = started

+        m_eventDelegate->onEventCondition(wasInPlay, isInPlay(), wasCurrent, isCurrent(), lastIteration, currentIteration);
 
     // FIXME: This probably shouldn't be recursive.
     updateChildrenAndEffects(wasInEffect);
 }
 
-TimedItem::CalculatedTiming::CalculatedTiming()
-    : activeDuration(nullValue())
-    , currentIteration(nullValue())
-    , timeFraction(nullValue())
-    , isCurrent(false)
-    , isInEffect(false)
-    , isInPlay(false)
-{
-}
-
 } // namespace WebCore