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 * in the documentation and/or other materials provided with the
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#include "third_party/blink/renderer/core/animation/pending_animations.h"

#include "third_party/blink/renderer/core/animation/document_timeline.h"
#include "third_party/blink/renderer/core/animation/keyframe_effect.h"
#include "third_party/blink/renderer/core/dom/document.h"
#include "third_party/blink/renderer/core/frame/local_frame_view.h"
#include "third_party/blink/renderer/core/page/page.h"
#include "third_party/blink/renderer/platform/instrumentation/tracing/trace_event.h"

namespace blink {

void PendingAnimations::Add(Animation* animation) {
  DCHECK(animation);
  DCHECK_EQ(pending_.Find(animation), kNotFound);
  pending_.push_back(animation);

  Document* document = animation->GetDocument();
  if (document->View())
    document->View()->ScheduleAnimation();

  bool visible = document->GetPage() && document->GetPage()->IsPageVisible();
  if (!visible && !timer_.IsActive() &&
      // TODO(crbug.com/916117): Firing a timer for animations linked to
      // inactive timelines creates an unnecessary cycle of unsuccessfully
      // starting such animations. Instead, let the animation frame call
      // PendingAnimations::Update when the timeline becomes active.
      // Revisit this condition and add a test as part of inactive timeline
      // implementation.
      animation->timeline() && animation->timeline()->IsActive()) {
    timer_.StartOneShot(base::TimeDelta(), FROM_HERE);
  }
}

bool PendingAnimations::Update(
    const PaintArtifactCompositor* paint_artifact_compositor,
    bool start_on_compositor) {
  HeapVector<Member<Animation>> waiting_for_start_time;
  bool started_synchronized_on_compositor = false;

  HeapVector<Member<Animation>> animations;
  HeapVector<Member<Animation>> deferred;
  animations.swap(pending_);
  int compositor_group = NextCompositorGroup();

  for (auto& animation : animations) {
    bool had_compositor_animation =
        animation->HasActiveAnimationsOnCompositor();
    // Animations with a start time do not participate in compositor start-time
    // grouping.
    if (animation->PreCommit(animation->startTime() ? 1 : compositor_group,
                             paint_artifact_compositor, start_on_compositor)) {
      if (animation->HasActiveAnimationsOnCompositor() &&
          !had_compositor_animation && !animation->startTime()) {
        started_synchronized_on_compositor = true;
      }

      // TODO(crbug.com/916117): Revisit this condition as part of handling
      // inactive timelines work.
      if (!animation->timeline() || !animation->timeline()->IsActive()) {
        DCHECK(!animation->timeline() ||
               !animation->timeline()->IsScrollTimeline());
        continue;
      }

      if (animation->Playing() && !animation->startTime()) {
        waiting_for_start_time.push_back(animation.Get());
      } else if (animation->PendingInternal()) {
        // A pending animation that is not waiting on a start time does not need
        // to be synchronized with animations that are starting up. Nonetheless,
        // it needs to notify the animation to resolve the ready promise and
        // commit the pending state.
        animation->NotifyReady(
            animation->timeline()->CurrentTimeSeconds().value_or(0));
      }
    } else {
      deferred.push_back(animation);
    }
  }

  // If any synchronized animations were started on the compositor, all
  // remaining synchronized animations need to wait for the synchronized
  // start time. Otherwise they may start immediately.
  if (started_synchronized_on_compositor) {
    FlushWaitingNonCompositedAnimations();
    waiting_for_compositor_animation_start_.AppendVector(
        waiting_for_start_time);
  } else {
    for (auto& animation : waiting_for_start_time) {
      DCHECK(!animation->startTime());
      // TODO(crbug.com/916117): Handle start time of scroll-linked animations.
      animation->NotifyReady(
          animation->timeline()->CurrentTimeSeconds().value_or(0));
    }
  }

  // FIXME: The postCommit should happen *after* the commit, not before.
  for (auto& animation : animations) {
    // TODO(crbug.com/916117): Handle NaN current time of scroll timeline.
    animation->PostCommit(
        animation->timeline()->CurrentTimeSeconds().value_or(0));
  }

  DCHECK(pending_.IsEmpty());
  for (auto& animation : deferred)
    animation->SetCompositorPending();
  DCHECK_EQ(pending_.size(), deferred.size());

  if (started_synchronized_on_compositor)
    return true;

  if (waiting_for_compositor_animation_start_.IsEmpty())
    return false;

  // Check if we're still waiting for any compositor animations to start.
  for (auto& animation : waiting_for_compositor_animation_start_) {
    if (animation->HasActiveAnimationsOnCompositor())
      return true;
  }

  // If not, go ahead and start any animations that were waiting.
  NotifyCompositorAnimationStarted(
      base::TimeTicks::Now().since_origin().InSecondsF());

  DCHECK_EQ(pending_.size(), deferred.size());
  return false;
}

void PendingAnimations::NotifyCompositorAnimationStarted(
    double monotonic_animation_start_time,
    int compositor_group) {
  TRACE_EVENT0("blink", "PendingAnimations::notifyCompositorAnimationStarted");

  HeapVector<Member<Animation>> animations;
  animations.swap(waiting_for_compositor_animation_start_);

  for (auto animation : animations) {
    if (animation->startTime() || !animation->PendingInternal() ||
        !animation->timeline() || !animation->timeline()->IsActive()) {
      // Already started or no longer relevant.
      continue;
    }
    if (compositor_group && animation->CompositorGroup() != compositor_group) {
      // Still waiting.
      waiting_for_compositor_animation_start_.push_back(animation);
      continue;
    }
    DCHECK(IsA<DocumentTimeline>(animation->timeline()));
    animation->NotifyReady(monotonic_animation_start_time -
                           To<DocumentTimeline>(animation->timeline())
                               ->ZeroTime()
                               .since_origin()
                               .InSecondsF());
  }
}

int PendingAnimations::NextCompositorGroup() {
  do {
    // Wrap around, skipping 0, 1.
    // * 0 is reserved for automatic assignment
    // * 1 is used for animations with a specified start time
    ++compositor_group_;
  } while (compositor_group_ == 0 || compositor_group_ == 1);

  return compositor_group_;
}

void PendingAnimations::FlushWaitingNonCompositedAnimations() {
  if (waiting_for_compositor_animation_start_.IsEmpty())
    return;

  // Start any main thread animations that were scheduled to wait on
  // compositor synchronization from a previous frame. Otherwise, an
  // continuous influx of new composited animations could delay the start
  // of non-composited animations indefinitely (crbug.com/666710).
  HeapVector<Member<Animation>> animations;
  animations.swap(waiting_for_compositor_animation_start_);
  for (auto& animation : animations) {
    if (animation->HasActiveAnimationsOnCompositor()) {
      waiting_for_compositor_animation_start_.push_back(animation);
    } else {
      // TODO(crbug.com/916117): Handle start time of scroll-linked
      // animations.
      animation->NotifyReady(
          animation->timeline()->CurrentTimeSeconds().value_or(0));
    }
  }
}

void PendingAnimations::Trace(Visitor* visitor) {
  visitor->Trace(pending_);
  visitor->Trace(waiting_for_compositor_animation_start_);
}

}  // namespace blink