layout/style/nsAnimationManager.cpp
author L. David Baron <dbaron@dbaron.org>
Tue, 17 Feb 2015 11:15:01 +1300
changeset 256494 d5fa940bfd9ccb26df75b4a572094a640b7c90c5
parent 255491 20729b28eb1e1d7f0d9e9e6e2c61e7050f09884f
child 256508 29d623ce3ed29bb43cbd4ec4b868989290588228
permissions -rw-r--r--
Bug 960465 patch 3 - Use style without animation for base values for CSS animations (refixes bug 686656 in the new architecture). r=birtles This is needed to make the tests for bug 686656 in test_animations.html pass. Note that once the rest of bug 960465 happens this will start producing slightly different results in edge cases, since we will only be skipping animation styles for the element itself and not for ancestors. However, both old and new behaviors are incorrect, since per spec we should be updating the base values dynamically (bug 1064915).

/* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsAnimationManager.h"
#include "nsTransitionManager.h"

#include "mozilla/EventDispatcher.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/StyleAnimationValue.h"

#include "nsPresContext.h"
#include "nsStyleSet.h"
#include "nsStyleChangeList.h"
#include "nsCSSRules.h"
#include "RestyleManager.h"
#include "nsLayoutUtils.h"
#include "nsIFrame.h"
#include "nsIDocument.h"
#include <math.h>

using namespace mozilla;
using namespace mozilla::css;
using mozilla::dom::Animation;
using mozilla::dom::AnimationPlayer;
using mozilla::CSSAnimationPlayer;

mozilla::dom::Promise*
CSSAnimationPlayer::GetReady(ErrorResult& aRv)
{
  FlushStyle();
  return AnimationPlayer::GetReady(aRv);
}

void
CSSAnimationPlayer::Play()
{
  mPauseShouldStick = false;
  AnimationPlayer::Play();
}

void
CSSAnimationPlayer::Pause()
{
  mPauseShouldStick = true;
  AnimationPlayer::Pause();
}

mozilla::dom::AnimationPlayState
CSSAnimationPlayer::PlayStateFromJS() const
{
  // Flush style to ensure that any properties controlling animation state
  // (e.g. animation-play-state) are fully updated.
  FlushStyle();
  return AnimationPlayer::PlayStateFromJS();
}

void
CSSAnimationPlayer::PlayFromJS()
{
  // Note that flushing style below might trigger calls to
  // PlayFromStyle()/PauseFromStyle() on this object.
  FlushStyle();
  AnimationPlayer::PlayFromJS();
}

void
CSSAnimationPlayer::PlayFromStyle()
{
  mIsStylePaused = false;
  if (!mPauseShouldStick) {
    DoPlay();
  }
}

void
CSSAnimationPlayer::PauseFromStyle()
{
  // Check if the pause state is being overridden
  if (mIsStylePaused) {
    return;
  }

  mIsStylePaused = true;
  DoPause();
}

void
CSSAnimationPlayer::QueueEvents(EventArray& aEventsToDispatch)
{
  if (!mSource) {
    return;
  }

  ComputedTiming computedTiming = mSource->GetComputedTiming();

  dom::Element* target;
  nsCSSPseudoElements::Type targetPseudoType;
  mSource->GetTarget(target, targetPseudoType);

  switch (computedTiming.mPhase) {
    case ComputedTiming::AnimationPhase_Null:
    case ComputedTiming::AnimationPhase_Before:
      // Do nothing
      break;

    case ComputedTiming::AnimationPhase_Active:
      // Dispatch 'animationstart' or 'animationiteration' when needed.
      if (computedTiming.mCurrentIteration != mLastNotification) {
        // Notify 'animationstart' even if a negative delay puts us
        // past the first iteration.
        // Note that when somebody changes the animation-duration
        // dynamically, this will fire an extra iteration event
        // immediately in many cases.  It's not clear to me if that's the
        // right thing to do.
        uint32_t message = mLastNotification == LAST_NOTIFICATION_NONE
                           ? NS_ANIMATION_START
                           : NS_ANIMATION_ITERATION;
        mLastNotification = computedTiming.mCurrentIteration;
        TimeDuration iterationStart =
          mSource->Timing().mIterationDuration *
          computedTiming.mCurrentIteration;
        TimeDuration elapsedTime =
          std::max(iterationStart, mSource->InitialAdvance());
        AnimationEventInfo ei(target, Name(), message,
                              StickyTimeDuration(elapsedTime),
                              PseudoTypeAsString(targetPseudoType));
        aEventsToDispatch.AppendElement(ei);
      }
      break;

    case ComputedTiming::AnimationPhase_After:
      // If we skipped the animation interval entirely, dispatch
      // 'animationstart' first
      if (mLastNotification == LAST_NOTIFICATION_NONE) {
        // Notifying for start of 0th iteration.
        // (This is overwritten below but we set it here to maintain
        // internal consistency.)
        mLastNotification = 0;
        StickyTimeDuration elapsedTime =
          std::min(StickyTimeDuration(mSource->InitialAdvance()),
                   computedTiming.mActiveDuration);
        AnimationEventInfo ei(target, Name(), NS_ANIMATION_START,
                              elapsedTime,
                              PseudoTypeAsString(targetPseudoType));
        aEventsToDispatch.AppendElement(ei);
      }
      // Dispatch 'animationend' when needed.
      if (mLastNotification != LAST_NOTIFICATION_END) {
        mLastNotification = LAST_NOTIFICATION_END;
        AnimationEventInfo ei(target, Name(), NS_ANIMATION_END,
                              computedTiming.mActiveDuration,
                              PseudoTypeAsString(targetPseudoType));
        aEventsToDispatch.AppendElement(ei);
      }
      break;
  }
}

CommonAnimationManager*
CSSAnimationPlayer::GetAnimationManager() const
{
  nsPresContext* context = GetPresContext();
  if (!context) {
    return nullptr;
  }

  return context->AnimationManager();
}

/* static */ nsString
CSSAnimationPlayer::PseudoTypeAsString(nsCSSPseudoElements::Type aPseudoType)
{
  switch (aPseudoType) {
    case nsCSSPseudoElements::ePseudo_before:
      return NS_LITERAL_STRING("::before");
    case nsCSSPseudoElements::ePseudo_after:
      return NS_LITERAL_STRING("::after");
    default:
      return EmptyString();
  }
}

void
nsAnimationManager::UpdateStyleAndEvents(AnimationPlayerCollection*
                                           aCollection,
                                         TimeStamp aRefreshTime,
                                         EnsureStyleRuleFlags aFlags)
{
  aCollection->EnsureStyleRuleFor(aRefreshTime, aFlags);
  QueueEvents(aCollection, mPendingEvents);
}

void
nsAnimationManager::QueueEvents(AnimationPlayerCollection* aCollection,
                                EventArray& aEventsToDispatch)
{
  for (size_t playerIdx = aCollection->mPlayers.Length(); playerIdx-- != 0; ) {
    CSSAnimationPlayer* player =
      aCollection->mPlayers[playerIdx]->AsCSSAnimationPlayer();
    MOZ_ASSERT(player, "Expected a collection of CSS Animation players");
    player->QueueEvents(aEventsToDispatch);
  }
}

/* virtual */ size_t
nsAnimationManager::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
{
  return CommonAnimationManager::SizeOfExcludingThis(aMallocSizeOf);

  // Measurement of the following members may be added later if DMD finds it is
  // worthwhile:
  // - mPendingEvents
}

/* virtual */ size_t
nsAnimationManager::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
{
  return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
}

nsIStyleRule*
nsAnimationManager::CheckAnimationRule(nsStyleContext* aStyleContext,
                                       mozilla::dom::Element* aElement)
{
  // FIXME (bug 960465): This test should go away.
  if (!mPresContext->RestyleManager()->IsProcessingAnimationStyleChange()) {
    if (!mPresContext->IsDynamic()) {
      // For print or print preview, ignore animations.
      return nullptr;
    }

    // Everything that causes our animation data to change triggers a
    // style change, which in turn triggers a non-animation restyle.
    // Likewise, when we initially construct frames, we're not in a
    // style change, but also not in an animation restyle.

    const nsStyleDisplay* disp = aStyleContext->StyleDisplay();
    AnimationPlayerCollection* collection =
      GetAnimationPlayers(aElement, aStyleContext->GetPseudoType(), false);
    if (!collection &&
        disp->mAnimationNameCount == 1 &&
        disp->mAnimations[0].GetName().IsEmpty()) {
      return nullptr;
    }

    // build the animations list
    dom::AnimationTimeline* timeline = aElement->OwnerDoc()->Timeline();
    AnimationPlayerPtrArray newPlayers;
    BuildAnimations(aStyleContext, aElement, timeline, newPlayers);

    if (newPlayers.IsEmpty()) {
      if (collection) {
        collection->Destroy();
      }
      return nullptr;
    }

    if (collection) {
      collection->mStyleRule = nullptr;
      collection->mStyleRuleRefreshTime = TimeStamp();
      collection->UpdateAnimationGeneration(mPresContext);

      // Copy over the start times and (if still paused) pause starts
      // for each animation (matching on name only) that was also in the
      // old list of animations.
      // This means that we honor dynamic changes, which isn't what the
      // spec says to do, but WebKit seems to honor at least some of
      // them.  See
      // http://lists.w3.org/Archives/Public/www-style/2011Apr/0079.html
      // In order to honor what the spec said, we'd copy more data over
      // (or potentially optimize BuildAnimations to avoid rebuilding it
      // in the first place).
      if (!collection->mPlayers.IsEmpty()) {

        for (size_t newIdx = newPlayers.Length(); newIdx-- != 0;) {
          AnimationPlayer* newPlayer = newPlayers[newIdx];

          // Find the matching animation with this name in the old list
          // of animations.  We iterate through both lists in a backwards
          // direction which means that if there are more animations in
          // the new list of animations with a given name than in the old
          // list, it will be the animations towards the of the beginning of
          // the list that do not match and are treated as new animations.
          nsRefPtr<CSSAnimationPlayer> oldPlayer;
          size_t oldIdx = collection->mPlayers.Length();
          while (oldIdx-- != 0) {
            CSSAnimationPlayer* a =
              collection->mPlayers[oldIdx]->AsCSSAnimationPlayer();
            MOZ_ASSERT(a, "All players in the CSS Animation collection should"
                          " be CSSAnimationPlayer objects");
            if (a->Name() == newPlayer->Name()) {
              oldPlayer = a;
              break;
            }
          }
          if (!oldPlayer) {
            continue;
          }

          // Update the old from the new so we can keep the original object
          // identity (and any expando properties attached to it).
          if (oldPlayer->GetSource() && newPlayer->GetSource()) {
            Animation* oldAnim = oldPlayer->GetSource();
            Animation* newAnim = newPlayer->GetSource();
            oldAnim->Timing() = newAnim->Timing();
            oldAnim->Properties() = newAnim->Properties();
          }

          // Reset compositor state so animation will be re-synchronized.
          oldPlayer->ClearIsRunningOnCompositor();

          // Handle changes in play state.
          // CSSAnimationPlayer takes care of override behavior so that,
          // for example, if the author has called pause(), that will
          // override the animation-play-state.
          // (We should check newPlayer->IsStylePaused() but that requires
          //  downcasting to CSSAnimationPlayer and we happen to know that
          //  newPlayer will only ever be paused by calling PauseFromStyle
          //  making IsPaused synonymous in this case.)
          if (!oldPlayer->IsStylePaused() && newPlayer->IsPaused()) {
            oldPlayer->PauseFromStyle();
          } else if (oldPlayer->IsStylePaused() && !newPlayer->IsPaused()) {
            oldPlayer->PlayFromStyle();
          }

          // Replace new animation with the (updated) old one and remove the
          // old one from the array so we don't try to match it any more.
          //
          // Although we're doing this while iterating this is safe because
          // we're not changing the length of newPlayers and we've finished
          // iterating over the list of old iterations.
          newPlayer->Cancel();
          newPlayer = nullptr;
          newPlayers.ReplaceElementAt(newIdx, oldPlayer);
          collection->mPlayers.RemoveElementAt(oldIdx);
        }
      }
    } else {
      collection =
        GetAnimationPlayers(aElement, aStyleContext->GetPseudoType(), true);
    }
    collection->mPlayers.SwapElements(newPlayers);
    collection->mNeedsRefreshes = true;
    collection->Tick();

    // Cancel removed animations
    for (size_t newPlayerIdx = newPlayers.Length(); newPlayerIdx-- != 0; ) {
      newPlayers[newPlayerIdx]->Cancel();
    }

    TimeStamp refreshTime = mPresContext->RefreshDriver()->MostRecentRefresh();
    UpdateStyleAndEvents(collection, refreshTime,
                         EnsureStyleRule_IsNotThrottled);
    // We don't actually dispatch the mPendingEvents now.  We'll either
    // dispatch them the next time we get a refresh driver notification
    // or the next time somebody calls
    // nsPresShell::FlushPendingNotifications.
    if (!mPendingEvents.IsEmpty()) {
      mPresContext->Document()->SetNeedStyleFlush();
    }
  }

  return GetAnimationRule(aElement, aStyleContext->GetPseudoType());
}

struct KeyframeData {
  float mKey;
  uint32_t mIndex; // store original order since sort algorithm is not stable
  nsCSSKeyframeRule *mRule;
};

struct KeyframeDataComparator {
  bool Equals(const KeyframeData& A, const KeyframeData& B) const {
    return A.mKey == B.mKey && A.mIndex == B.mIndex;
  }
  bool LessThan(const KeyframeData& A, const KeyframeData& B) const {
    return A.mKey < B.mKey || (A.mKey == B.mKey && A.mIndex < B.mIndex);
  }
};

class ResolvedStyleCache {
public:
  ResolvedStyleCache() : mCache() {}
  nsStyleContext* Get(nsPresContext *aPresContext,
                      nsStyleContext *aParentStyleContext,
                      nsCSSKeyframeRule *aKeyframe);

private:
  nsRefPtrHashtable<nsPtrHashKey<nsCSSKeyframeRule>, nsStyleContext> mCache;
};

nsStyleContext*
ResolvedStyleCache::Get(nsPresContext *aPresContext,
                        nsStyleContext *aParentStyleContext,
                        nsCSSKeyframeRule *aKeyframe)
{
  // FIXME (spec):  The css3-animations spec isn't very clear about how
  // properties are resolved when they have values that depend on other
  // properties (e.g., values in 'em').  I presume that they're resolved
  // relative to the other styles of the element.  The question is
  // whether they are resolved relative to other animations:  I assume
  // that they're not, since that would prevent us from caching a lot of
  // data that we'd really like to cache (in particular, the
  // StyleAnimationValue values in AnimationPropertySegment).
  nsStyleContext *result = mCache.GetWeak(aKeyframe);
  if (!result) {
    nsCOMArray<nsIStyleRule> rules;
    rules.AppendObject(aKeyframe);
    nsRefPtr<nsStyleContext> resultStrong = aPresContext->StyleSet()->
      ResolveStyleByAddingRules(aParentStyleContext, rules);
    mCache.Put(aKeyframe, resultStrong);
    result = resultStrong;
  }
  return result;
}

void
nsAnimationManager::BuildAnimations(nsStyleContext* aStyleContext,
                                    dom::Element* aTarget,
                                    dom::AnimationTimeline* aTimeline,
                                    AnimationPlayerPtrArray& aPlayers)
{
  MOZ_ASSERT(aPlayers.IsEmpty(), "expect empty array");

  ResolvedStyleCache resolvedStyles;

  const nsStyleDisplay *disp = aStyleContext->StyleDisplay();

  nsRefPtr<nsStyleContext> styleWithoutAnimation;

  for (size_t animIdx = 0, animEnd = disp->mAnimationNameCount;
       animIdx != animEnd; ++animIdx) {
    const StyleAnimation& src = disp->mAnimations[animIdx];

    // CSS Animations whose animation-name does not match a @keyframes rule do
    // not generate animation events. This includes when the animation-name is
    // "none" which is represented by an empty name in the StyleAnimation.
    // Since such animations neither affect style nor dispatch events, we do
    // not generate a corresponding AnimationPlayer for them.
    nsCSSKeyframesRule* rule =
      src.GetName().IsEmpty()
      ? nullptr
      : mPresContext->StyleSet()->KeyframesRuleForName(mPresContext,
                                                       src.GetName());
    if (!rule) {
      continue;
    }

    nsRefPtr<CSSAnimationPlayer> dest = new CSSAnimationPlayer(aTimeline);
    aPlayers.AppendElement(dest);

    AnimationTiming timing;
    timing.mIterationDuration =
      TimeDuration::FromMilliseconds(src.GetDuration());
    timing.mDelay = TimeDuration::FromMilliseconds(src.GetDelay());
    timing.mIterationCount = src.GetIterationCount();
    timing.mDirection = src.GetDirection();
    timing.mFillMode = src.GetFillMode();

    nsRefPtr<Animation> destAnim =
      new Animation(mPresContext->Document(), aTarget,
                    aStyleContext->GetPseudoType(), timing, src.GetName());
    dest->SetSource(destAnim);

    // Even in the case where we call PauseFromStyle below, we still need to
    // call PlayFromStyle first. This is because a newly-created player is idle
    // and has no effect until it is played (or otherwise given a start time).
    dest->PlayFromStyle();

    if (src.GetPlayState() == NS_STYLE_ANIMATION_PLAY_STATE_PAUSED) {
      dest->PauseFromStyle();
    }

    // While current drafts of css3-animations say that later keyframes
    // with the same key entirely replace earlier ones (no cascading),
    // this is a bad idea and contradictory to the rest of CSS.  So
    // we're going to keep all the keyframes for each key and then do
    // the replacement on a per-property basis rather than a per-rule
    // basis, just like everything else in CSS.

    AutoInfallibleTArray<KeyframeData, 16> sortedKeyframes;

    for (uint32_t ruleIdx = 0, ruleEnd = rule->StyleRuleCount();
         ruleIdx != ruleEnd; ++ruleIdx) {
      css::Rule* cssRule = rule->GetStyleRuleAt(ruleIdx);
      MOZ_ASSERT(cssRule, "must have rule");
      MOZ_ASSERT(cssRule->GetType() == css::Rule::KEYFRAME_RULE,
                 "must be keyframe rule");
      nsCSSKeyframeRule *kfRule = static_cast<nsCSSKeyframeRule*>(cssRule);

      const nsTArray<float> &keys = kfRule->GetKeys();
      for (uint32_t keyIdx = 0, keyEnd = keys.Length();
           keyIdx != keyEnd; ++keyIdx) {
        float key = keys[keyIdx];
        // FIXME (spec):  The spec doesn't say what to do with
        // out-of-range keyframes.  We'll ignore them.
        if (0.0f <= key && key <= 1.0f) {
          KeyframeData *data = sortedKeyframes.AppendElement();
          data->mKey = key;
          data->mIndex = ruleIdx;
          data->mRule = kfRule;
        }
      }
    }

    sortedKeyframes.Sort(KeyframeDataComparator());

    if (sortedKeyframes.Length() == 0) {
      // no segments
      continue;
    }

    // Record the properties that are present in any keyframe rules we
    // are using.
    nsCSSPropertySet properties;

    for (uint32_t kfIdx = 0, kfEnd = sortedKeyframes.Length();
         kfIdx != kfEnd; ++kfIdx) {
      css::Declaration *decl = sortedKeyframes[kfIdx].mRule->Declaration();
      for (uint32_t propIdx = 0, propEnd = decl->Count();
           propIdx != propEnd; ++propIdx) {
        nsCSSProperty prop = decl->GetPropertyAt(propIdx);
        if (prop != eCSSPropertyExtra_variable) {
          // CSS Variables are not animatable
          properties.AddProperty(prop);
        }
      }
    }

    for (nsCSSProperty prop = nsCSSProperty(0);
         prop < eCSSProperty_COUNT_no_shorthands;
         prop = nsCSSProperty(prop + 1)) {
      if (!properties.HasProperty(prop) ||
          nsCSSProps::kAnimTypeTable[prop] == eStyleAnimType_None) {
        continue;
      }

      // Build a list of the keyframes to use for this property.  This
      // means we need every keyframe with the property in it, except
      // for those keyframes where a later keyframe with the *same key*
      // also has the property.
      AutoInfallibleTArray<uint32_t, 16> keyframesWithProperty;
      float lastKey = 100.0f; // an invalid key
      for (uint32_t kfIdx = 0, kfEnd = sortedKeyframes.Length();
           kfIdx != kfEnd; ++kfIdx) {
        KeyframeData &kf = sortedKeyframes[kfIdx];
        if (!kf.mRule->Declaration()->HasProperty(prop)) {
          continue;
        }
        if (kf.mKey == lastKey) {
          // Replace previous occurrence of same key.
          keyframesWithProperty[keyframesWithProperty.Length() - 1] = kfIdx;
        } else {
          keyframesWithProperty.AppendElement(kfIdx);
        }
        lastKey = kf.mKey;
      }

      AnimationProperty &propData = *destAnim->Properties().AppendElement();
      propData.mProperty = prop;

      KeyframeData *fromKeyframe = nullptr;
      nsRefPtr<nsStyleContext> fromContext;
      bool interpolated = true;
      for (uint32_t wpIdx = 0, wpEnd = keyframesWithProperty.Length();
           wpIdx != wpEnd; ++wpIdx) {
        uint32_t kfIdx = keyframesWithProperty[wpIdx];
        KeyframeData &toKeyframe = sortedKeyframes[kfIdx];

        nsRefPtr<nsStyleContext> toContext =
          resolvedStyles.Get(mPresContext, aStyleContext, toKeyframe.mRule);

        if (fromKeyframe) {
          interpolated = interpolated &&
            BuildSegment(propData.mSegments, prop, src,
                         fromKeyframe->mKey, fromContext,
                         fromKeyframe->mRule->Declaration(),
                         toKeyframe.mKey, toContext);
        } else {
          if (toKeyframe.mKey != 0.0f) {
            // There's no data for this property at 0%, so use the
            // cascaded value above us.
            if (!styleWithoutAnimation) {
              styleWithoutAnimation = mPresContext->StyleSet()->
                ResolveStyleWithoutAnimation(aTarget, aStyleContext,
                                             eRestyle_ChangeAnimationPhase);
            }
            interpolated = interpolated &&
              BuildSegment(propData.mSegments, prop, src,
                           0.0f, styleWithoutAnimation, nullptr,
                           toKeyframe.mKey, toContext);
          }
        }

        fromContext = toContext;
        fromKeyframe = &toKeyframe;
      }

      if (fromKeyframe->mKey != 1.0f) {
        // There's no data for this property at 100%, so use the
        // cascaded value above us.
        if (!styleWithoutAnimation) {
          styleWithoutAnimation = mPresContext->StyleSet()->
            ResolveStyleWithoutAnimation(aTarget, aStyleContext,
                                         eRestyle_ChangeAnimationPhase);
        }
        interpolated = interpolated &&
          BuildSegment(propData.mSegments, prop, src,
                       fromKeyframe->mKey, fromContext,
                       fromKeyframe->mRule->Declaration(),
                       1.0f, styleWithoutAnimation);
      }

      // If we failed to build any segments due to inability to
      // interpolate, remove the property from the animation.  (It's not
      // clear if this is the right thing to do -- we could run some of
      // the segments, but it's really not clear whether we should skip
      // values (which?) or skip segments, so best to skip the whole
      // thing for now.)
      if (!interpolated) {
        destAnim->Properties().RemoveElementAt(
          destAnim->Properties().Length() - 1);
      }
    }
  }
}

bool
nsAnimationManager::BuildSegment(InfallibleTArray<AnimationPropertySegment>&
                                   aSegments,
                                 nsCSSProperty aProperty,
                                 const StyleAnimation& aAnimation,
                                 float aFromKey, nsStyleContext* aFromContext,
                                 mozilla::css::Declaration* aFromDeclaration,
                                 float aToKey, nsStyleContext* aToContext)
{
  StyleAnimationValue fromValue, toValue, dummyValue;
  if (!ExtractComputedValueForTransition(aProperty, aFromContext, fromValue) ||
      !ExtractComputedValueForTransition(aProperty, aToContext, toValue) ||
      // Check that we can interpolate between these values
      // (If this is ever a performance problem, we could add a
      // CanInterpolate method, but it seems fine for now.)
      !StyleAnimationValue::Interpolate(aProperty, fromValue, toValue,
                                        0.5, dummyValue)) {
    return false;
  }

  AnimationPropertySegment &segment = *aSegments.AppendElement();

  segment.mFromValue = fromValue;
  segment.mToValue = toValue;
  segment.mFromKey = aFromKey;
  segment.mToKey = aToKey;
  const nsTimingFunction *tf;
  if (aFromDeclaration &&
      aFromDeclaration->HasProperty(eCSSProperty_animation_timing_function)) {
    tf = &aFromContext->StyleDisplay()->mAnimations[0].GetTimingFunction();
  } else {
    tf = &aAnimation.GetTimingFunction();
  }
  segment.mTimingFunction.Init(*tf);

  return true;
}

/* virtual */ void
nsAnimationManager::WillRefresh(mozilla::TimeStamp aTime)
{
  MOZ_ASSERT(mPresContext,
             "refresh driver should not notify additional observers "
             "after pres context has been destroyed");
  if (!mPresContext->GetPresShell()) {
    // Someone might be keeping mPresContext alive past the point
    // where it has been torn down; don't bother doing anything in
    // this case.  But do get rid of all our transitions so we stop
    // triggering refreshes.
    RemoveAllElementCollections();
    return;
  }

  FlushAnimations(Can_Throttle);
}

void
nsAnimationManager::FlushAnimations(FlushFlags aFlags)
{
  // FIXME: check that there's at least one style rule that's not
  // in its "done" state, and if there isn't, remove ourselves from
  // the refresh driver (but leave the animations!).
  TimeStamp now = mPresContext->RefreshDriver()->MostRecentRefresh();
  bool didThrottle = false;
  for (PRCList *l = PR_LIST_HEAD(&mElementCollections);
       l != &mElementCollections;
       l = PR_NEXT_LINK(l)) {
    AnimationPlayerCollection* collection =
      static_cast<AnimationPlayerCollection*>(l);
    collection->Tick();
    bool canThrottleTick = aFlags == Can_Throttle &&
      collection->CanPerformOnCompositorThread(
        AnimationPlayerCollection::CanAnimateFlags(0)) &&
      collection->CanThrottleAnimation(now);

    nsRefPtr<css::AnimValuesStyleRule> oldStyleRule = collection->mStyleRule;
    UpdateStyleAndEvents(collection, now, canThrottleTick
                                          ? EnsureStyleRule_IsThrottled
                                          : EnsureStyleRule_IsNotThrottled);
    if (oldStyleRule != collection->mStyleRule) {
      collection->PostRestyleForAnimation(mPresContext);
    } else {
      didThrottle = true;
    }
  }

  if (didThrottle) {
    mPresContext->Document()->SetNeedStyleFlush();
  }

  DispatchEvents(); // may destroy us
}

void
nsAnimationManager::DoDispatchEvents()
{
  EventArray events;
  mPendingEvents.SwapElements(events);
  for (uint32_t i = 0, i_end = events.Length(); i < i_end; ++i) {
    AnimationEventInfo &info = events[i];
    EventDispatcher::Dispatch(info.mElement, mPresContext, &info.mEvent);

    if (!mPresContext) {
      break;
    }
  }
}