1 files changed, 193 insertions, 0 deletions
diff --git a/dom/animation/PendingAnimationTracker.cpp b/dom/animation/PendingAnimationTracker.cpp
new file mode 100644
index 0000000000..f4c01b8648
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+++ b/dom/animation/PendingAnimationTracker.cpp
@@ -0,0 +1,193 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "PendingAnimationTracker.h"
+
+#include "mozilla/PresShell.h"
+#include "mozilla/dom/AnimationEffect.h"
+#include "mozilla/dom/AnimationTimeline.h"
+#include "mozilla/dom/Nullable.h"
+#include "nsIFrame.h"
+#include "nsTransitionManager.h"  // For CSSTransition
+
+using mozilla::dom::Nullable;
+
+namespace mozilla {
+
+NS_IMPL_CYCLE_COLLECTION(PendingAnimationTracker, mPlayPendingSet,
+                         mPausePendingSet, mDocument)
+
+NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(PendingAnimationTracker, AddRef)
+NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(PendingAnimationTracker, Release)
+
+PendingAnimationTracker::PendingAnimationTracker(dom::Document* aDocument)
+    : mDocument(aDocument) {}
+
+void PendingAnimationTracker::AddPending(dom::Animation& aAnimation,
+                                         AnimationSet& aSet) {
+  aSet.PutEntry(&aAnimation);
+
+  // Schedule a paint. Otherwise animations that don't trigger a paint by
+  // themselves (e.g. CSS animations with an empty keyframes rule) won't
+  // start until something else paints.
+  EnsurePaintIsScheduled();
+}
+
+void PendingAnimationTracker::RemovePending(dom::Animation& aAnimation,
+                                            AnimationSet& aSet) {
+  aSet.RemoveEntry(&aAnimation);
+}
+
+bool PendingAnimationTracker::IsWaiting(const dom::Animation& aAnimation,
+                                        const AnimationSet& aSet) const {
+  return aSet.Contains(const_cast<dom::Animation*>(&aAnimation));
+}
+
+void PendingAnimationTracker::TriggerPendingAnimationsOnNextTick(
+    const TimeStamp& aReadyTime) {
+  auto triggerAnimationsAtReadyTime = [aReadyTime](
+                                          AnimationSet& aAnimationSet) {
+    for (auto iter = aAnimationSet.Iter(); !iter.Done(); iter.Next()) {
+      dom::Animation* animation = iter.Get()->GetKey();
+      dom::AnimationTimeline* timeline = animation->GetTimeline();
+
+      // If the animation does not have a timeline, just drop it from the map.
+      // The animation will detect that it is not being tracked and will trigger
+      // itself on the next tick where it has a timeline.
+      if (!timeline) {
+        iter.Remove();
+        continue;
+      }
+
+      // When the timeline's refresh driver is under test control, its values
+      // have no correspondance to wallclock times so we shouldn't try to
+      // convert aReadyTime (which is a wallclock time) to a timeline value.
+      // Instead, the animation will be started/paused when the refresh driver
+      // is next advanced since this will trigger a call to
+      // TriggerPendingAnimationsNow.
+      if (!timeline->TracksWallclockTime()) {
+        continue;
+      }
+
+      Nullable<TimeDuration> readyTime = timeline->ToTimelineTime(aReadyTime);
+      animation->TriggerOnNextTick(readyTime);
+
+      iter.Remove();
+    }
+  };
+
+  triggerAnimationsAtReadyTime(mPlayPendingSet);
+  triggerAnimationsAtReadyTime(mPausePendingSet);
+
+  mHasPlayPendingGeometricAnimations =
+      mPlayPendingSet.Count() ? CheckState::Indeterminate : CheckState::Absent;
+}
+
+void PendingAnimationTracker::TriggerPendingAnimationsNow() {
+  auto triggerAndClearAnimations = [](AnimationSet& aAnimationSet) {
+    for (auto iter = aAnimationSet.Iter(); !iter.Done(); iter.Next()) {
+      iter.Get()->GetKey()->TriggerNow();
+    }
+    aAnimationSet.Clear();
+  };
+
+  triggerAndClearAnimations(mPlayPendingSet);
+  triggerAndClearAnimations(mPausePendingSet);
+
+  mHasPlayPendingGeometricAnimations = CheckState::Absent;
+}
+
+static bool IsTransition(const dom::Animation& aAnimation) {
+  const dom::CSSTransition* transition = aAnimation.AsCSSTransition();
+  return transition && transition->IsTiedToMarkup();
+}
+
+void PendingAnimationTracker::MarkAnimationsThatMightNeedSynchronization() {
+  // We only set mHasPlayPendingGeometricAnimations to "present" in this method
+  // and nowhere else. After setting the state to "present", if there is any
+  // change to the set of play-pending animations we will reset
+  // mHasPlayPendingGeometricAnimations to either "indeterminate" or "absent".
+  //
+  // As a result, if mHasPlayPendingGeometricAnimations is "present", we can
+  // assume that this method has already been called for the current set of
+  // play-pending animations and it is not necessary to run this method again.
+  //
+  // If mHasPlayPendingGeometricAnimations is "absent", then we can also skip
+  // the body of this method since there are no notifications to be sent.
+  //
+  // Therefore, the only case we need to be concerned about is the
+  // "indeterminate" case. For all other cases we can return early.
+  //
+  // Note that *without* this optimization, starting animations would become
+  // O(n^2) in the case where each animation is on a different element and
+  // contains a compositor-animatable property since we would end up iterating
+  // over all animations in the play-pending set for each target element.
+  if (mHasPlayPendingGeometricAnimations != CheckState::Indeterminate) {
+    return;
+  }
+
+  // We only synchronize CSS transitions with other CSS transitions (and we only
+  // synchronize non-transition animations with non-transition animations)
+  // since typically the author will not trigger both CSS animations and
+  // CSS transitions simultaneously and expect them to be synchronized.
+  //
+  // If we try to synchronize CSS transitions with non-transitions then for some
+  // content we will end up degrading performance by forcing animations to run
+  // on the main thread that really don't need to.
+
+  mHasPlayPendingGeometricAnimations = CheckState::Absent;
+  for (auto iter = mPlayPendingSet.ConstIter(); !iter.Done(); iter.Next()) {
+    auto animation = iter.Get()->GetKey();
+    if (animation->GetEffect() && animation->GetEffect()->AffectsGeometry()) {
+      mHasPlayPendingGeometricAnimations &= ~CheckState::Absent;
+      mHasPlayPendingGeometricAnimations |= IsTransition(*animation)
+                                                ? CheckState::TransitionsPresent
+                                                : CheckState::AnimationsPresent;
+
+      // If we have both transitions and animations we don't need to look any
+      // further.
+      if (mHasPlayPendingGeometricAnimations ==
+          (CheckState::TransitionsPresent | CheckState::AnimationsPresent)) {
+        break;
+      }
+    }
+  }
+
+  if (mHasPlayPendingGeometricAnimations == CheckState::Absent) {
+    return;
+  }
+
+  for (auto iter = mPlayPendingSet.Iter(); !iter.Done(); iter.Next()) {
+    auto animation = iter.Get()->GetKey();
+    bool isTransition = IsTransition(*animation);
+    if ((isTransition &&
+         mHasPlayPendingGeometricAnimations & CheckState::TransitionsPresent) ||
+        (!isTransition &&
+         mHasPlayPendingGeometricAnimations & CheckState::AnimationsPresent)) {
+      animation->NotifyGeometricAnimationsStartingThisFrame();
+    }
+  }
+}
+
+void PendingAnimationTracker::EnsurePaintIsScheduled() {
+  if (!mDocument) {
+    return;
+  }
+
+  PresShell* presShell = mDocument->GetPresShell();
+  if (!presShell) {
+    return;
+  }
+
+  nsIFrame* rootFrame = presShell->GetRootFrame();
+  if (!rootFrame) {
+    return;
+  }
+
+  rootFrame->SchedulePaintWithoutInvalidatingObservers();
+}
+
+}  // namespace mozilla