third_party/WebKit/Source/platform/scroll/ScrollAnimator.cpp

/*
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#include "platform/scroll/ScrollAnimator.h"

#include "cc/animation/scroll_offset_animation_curve.h"
#include "platform/animation/CompositorAnimation.h"
#include "platform/graphics/GraphicsLayer.h"
#include "platform/scroll/MainThreadScrollingReason.h"
#include "platform/scroll/ScrollableArea.h"
#include "platform/tracing/TraceEvent.h"
#include "public/platform/Platform.h"
#include "public/platform/WebCompositorSupport.h"
#include "wtf/CurrentTime.h"
#include "wtf/PassRefPtr.h"
#include "wtf/PtrUtil.h"
#include <memory>

namespace blink {

namespace {

WebLayer* toWebLayer(GraphicsLayer* layer) {
  return layer ? layer->platformLayer() : nullptr;
}

}  // namespace

ScrollAnimatorBase* ScrollAnimatorBase::create(ScrollableArea* scrollableArea) {
  if (scrollableArea && scrollableArea->scrollAnimatorEnabled())
    return new ScrollAnimator(scrollableArea);
  return new ScrollAnimatorBase(scrollableArea);
}

ScrollAnimator::ScrollAnimator(ScrollableArea* scrollableArea,
                               WTF::TimeFunction timeFunction)
    : ScrollAnimatorBase(scrollableArea),
      m_timeFunction(timeFunction),
      m_lastGranularity(ScrollByPixel) {}

ScrollAnimator::~ScrollAnimator() {}

ScrollOffset ScrollAnimator::desiredTargetOffset() const {
  if (m_runState == RunState::WaitingToCancelOnCompositor)
    return currentOffset();
  return (m_animationCurve || m_runState == RunState::WaitingToSendToCompositor)
             ? m_targetOffset
             : currentOffset();
}

bool ScrollAnimator::hasRunningAnimation() const {
  return m_runState != RunState::PostAnimationCleanup &&
         (m_animationCurve ||
          m_runState == RunState::WaitingToSendToCompositor);
}

ScrollOffset ScrollAnimator::computeDeltaToConsume(
    const ScrollOffset& delta) const {
  ScrollOffset pos = desiredTargetOffset();
  ScrollOffset newPos = m_scrollableArea->clampScrollOffset(pos + delta);
  return newPos - pos;
}

void ScrollAnimator::resetAnimationState() {
  ScrollAnimatorCompositorCoordinator::resetAnimationState();
  if (m_animationCurve)
    m_animationCurve.reset();
  m_startTime = 0.0;
}

ScrollResult ScrollAnimator::userScroll(ScrollGranularity granularity,
                                        const ScrollOffset& delta) {
  if (!m_scrollableArea->scrollAnimatorEnabled())
    return ScrollAnimatorBase::userScroll(granularity, delta);

  TRACE_EVENT0("blink", "ScrollAnimator::scroll");

  if (granularity == ScrollByPrecisePixel) {
    // Cancel scroll animation because asked to instant scroll.
    if (hasRunningAnimation())
      cancelAnimation();
    return ScrollAnimatorBase::userScroll(granularity, delta);
  }

  bool needsPostAnimationCleanup = m_runState == RunState::PostAnimationCleanup;
  if (m_runState == RunState::PostAnimationCleanup)
    resetAnimationState();

  ScrollOffset consumedDelta = computeDeltaToConsume(delta);
  ScrollOffset targetOffset = desiredTargetOffset();
  targetOffset += consumedDelta;

  if (willAnimateToOffset(targetOffset)) {
    m_lastGranularity = granularity;
    // Report unused delta only if there is no animation running. See
    // comment below regarding scroll latching.
    // TODO(bokan): Need to standardize how ScrollAnimators report
    // unusedDelta. This differs from ScrollAnimatorMac currently.
    return ScrollResult(true, true, 0, 0);
  }

  // If the run state when this method was called was PostAnimationCleanup and
  // we're not starting an animation, stay in PostAnimationCleanup state so
  // that the main thread scrolling reason can be removed.
  if (needsPostAnimationCleanup)
    m_runState = RunState::PostAnimationCleanup;

  // Report unused delta only if there is no animation and we are not
  // starting one. This ensures we latch for the duration of the
  // animation rather than animating multiple scrollers at the same time.
  return ScrollResult(false, false, delta.width(), delta.height());
}

bool ScrollAnimator::willAnimateToOffset(const ScrollOffset& targetOffset) {
  if (m_runState == RunState::PostAnimationCleanup)
    resetAnimationState();

  if (m_runState == RunState::WaitingToCancelOnCompositor ||
      m_runState == RunState::WaitingToCancelOnCompositorButNewScroll) {
    ASSERT(m_animationCurve);
    m_targetOffset = targetOffset;
    if (registerAndScheduleAnimation())
      m_runState = RunState::WaitingToCancelOnCompositorButNewScroll;
    return true;
  }

  if (m_animationCurve) {
    if ((targetOffset - m_targetOffset).isZero())
      return true;

    m_targetOffset = targetOffset;
    ASSERT(m_runState == RunState::RunningOnMainThread ||
           m_runState == RunState::RunningOnCompositor ||
           m_runState == RunState::RunningOnCompositorButNeedsUpdate ||
           m_runState == RunState::RunningOnCompositorButNeedsTakeover);

    // Running on the main thread, simply update the target offset instead
    // of sending to the compositor.
    if (m_runState == RunState::RunningOnMainThread) {
      m_animationCurve->updateTarget(
          m_timeFunction() - m_startTime,
          compositorOffsetFromBlinkOffset(targetOffset));
      return true;
    }

    if (registerAndScheduleAnimation())
      m_runState = RunState::RunningOnCompositorButNeedsUpdate;
    return true;
  }

  if ((targetOffset - currentOffset()).isZero())
    return false;

  m_targetOffset = targetOffset;
  m_startTime = m_timeFunction();

  if (registerAndScheduleAnimation())
    m_runState = RunState::WaitingToSendToCompositor;

  return true;
}

void ScrollAnimator::adjustAnimationAndSetScrollOffset(
    const ScrollOffset& offset,
    ScrollType scrollType) {
  IntSize adjustment =
      roundedIntSize(offset) - roundedIntSize(m_scrollableArea->scrollOffset());
  scrollOffsetChanged(offset, scrollType);

  if (m_runState == RunState::Idle) {
    adjustImplOnlyScrollOffsetAnimation(adjustment);
  } else if (hasRunningAnimation()) {
    m_targetOffset += ScrollOffset(adjustment);
    if (m_animationCurve) {
      m_animationCurve->applyAdjustment(adjustment);
      if (m_runState != RunState::RunningOnMainThread &&
          registerAndScheduleAnimation())
        m_runState = RunState::RunningOnCompositorButNeedsAdjustment;
    }
  }
}

void ScrollAnimator::scrollToOffsetWithoutAnimation(
    const ScrollOffset& offset) {
  m_currentOffset = offset;

  resetAnimationState();
  notifyOffsetChanged();
}

void ScrollAnimator::tickAnimation(double monotonicTime) {
  if (m_runState != RunState::RunningOnMainThread)
    return;

  TRACE_EVENT0("blink", "ScrollAnimator::tickAnimation");
  double elapsedTime = monotonicTime - m_startTime;

  bool isFinished = (elapsedTime > m_animationCurve->duration());
  ScrollOffset offset = blinkOffsetFromCompositorOffset(
      isFinished ? m_animationCurve->targetValue()
                 : m_animationCurve->getValue(elapsedTime));

  offset = m_scrollableArea->clampScrollOffset(offset);

  m_currentOffset = offset;

  if (isFinished)
    m_runState = RunState::PostAnimationCleanup;
  else
    getScrollableArea()->scheduleAnimation();

  TRACE_EVENT0("blink", "ScrollAnimator::notifyOffsetChanged");
  notifyOffsetChanged();
}

void ScrollAnimator::postAnimationCleanupAndReset() {
  // Remove the temporary main thread scrolling reason that was added while
  // main thread had scheduled an animation.
  removeMainThreadScrollingReason();

  resetAnimationState();
}

bool ScrollAnimator::sendAnimationToCompositor() {
  if (m_scrollableArea->shouldScrollOnMainThread())
    return false;

  std::unique_ptr<CompositorAnimation> animation = CompositorAnimation::create(
      *m_animationCurve, CompositorTargetProperty::SCROLL_OFFSET, 0, 0);
  // Being here means that either there is an animation that needs
  // to be sent to the compositor, or an animation that needs to
  // be updated (a new scroll event before the previous animation
  // is finished). In either case, the start time is when the
  // first animation was initiated. This re-targets the animation
  // using the current time on main thread.
  animation->setStartTime(m_startTime);

  int animationId = animation->id();
  int animationGroupId = animation->group();

  bool sentToCompositor = addAnimation(std::move(animation));
  if (sentToCompositor) {
    m_runState = RunState::RunningOnCompositor;
    m_compositorAnimationId = animationId;
    m_compositorAnimationGroupId = animationGroupId;
  }

  return sentToCompositor;
}

void ScrollAnimator::createAnimationCurve() {
  DCHECK(!m_animationCurve);
  m_animationCurve = CompositorScrollOffsetAnimationCurve::create(
      compositorOffsetFromBlinkOffset(m_targetOffset),
      m_lastGranularity == ScrollByPixel
          ? CompositorScrollOffsetAnimationCurve::ScrollDurationInverseDelta
          : CompositorScrollOffsetAnimationCurve::ScrollDurationConstant);
  m_animationCurve->setInitialValue(
      compositorOffsetFromBlinkOffset(currentOffset()));
}

void ScrollAnimator::updateCompositorAnimations() {
  ScrollAnimatorCompositorCoordinator::updateCompositorAnimations();

  if (m_runState == RunState::PostAnimationCleanup) {
    postAnimationCleanupAndReset();
    return;
  }

  if (m_runState == RunState::WaitingToCancelOnCompositor) {
    DCHECK(m_compositorAnimationId);
    abortAnimation();
    postAnimationCleanupAndReset();
    return;
  }

  if (m_runState == RunState::RunningOnCompositorButNeedsTakeover) {
    // The call to ::takeOverCompositorAnimation aborted the animation and
    // put us in this state. The assumption is that takeOver is called
    // because a main thread scrolling reason is added, and simply trying
    // to ::sendAnimationToCompositor will fail and we will run on the main
    // thread.
    resetAnimationIds();
    m_runState = RunState::WaitingToSendToCompositor;
  }

  if (m_runState == RunState::RunningOnCompositorButNeedsUpdate ||
      m_runState == RunState::WaitingToCancelOnCompositorButNewScroll ||
      m_runState == RunState::RunningOnCompositorButNeedsAdjustment) {
    // Abort the running animation before a new one with an updated
    // target is added.
    abortAnimation();
    resetAnimationIds();

    if (m_runState != RunState::RunningOnCompositorButNeedsAdjustment) {
      // When in RunningOnCompositorButNeedsAdjustment, the call to
      // ::adjustScrollOffsetAnimation should have made the necessary
      // adjustment to the curve.
      m_animationCurve->updateTarget(
          m_timeFunction() - m_startTime,
          compositorOffsetFromBlinkOffset(m_targetOffset));
    }

    if (m_runState == RunState::WaitingToCancelOnCompositorButNewScroll) {
      m_animationCurve->setInitialValue(
          compositorOffsetFromBlinkOffset(currentOffset()));
    }

    m_runState = RunState::WaitingToSendToCompositor;
  }

  if (m_runState == RunState::WaitingToSendToCompositor) {
    if (!m_compositorAnimationAttachedToElementId)
      reattachCompositorPlayerIfNeeded(
          getScrollableArea()->compositorAnimationTimeline());

    if (!m_animationCurve)
      createAnimationCurve();

    bool runningOnMainThread = false;
    bool sentToCompositor = sendAnimationToCompositor();
    if (!sentToCompositor) {
      runningOnMainThread = registerAndScheduleAnimation();
      if (runningOnMainThread)
        m_runState = RunState::RunningOnMainThread;
    }

    // Main thread should deal with the scroll animations it started.
    if (sentToCompositor || runningOnMainThread)
      addMainThreadScrollingReason();
    else
      removeMainThreadScrollingReason();
  }
}

void ScrollAnimator::addMainThreadScrollingReason() {
  if (WebLayer* scrollLayer =
          toWebLayer(getScrollableArea()->layerForScrolling())) {
    scrollLayer->addMainThreadScrollingReasons(
        MainThreadScrollingReason::kHandlingScrollFromMainThread);
  }
}

void ScrollAnimator::removeMainThreadScrollingReason() {
  if (WebLayer* scrollLayer =
          toWebLayer(getScrollableArea()->layerForScrolling())) {
    scrollLayer->clearMainThreadScrollingReasons(
        MainThreadScrollingReason::kHandlingScrollFromMainThread);
  }
}

void ScrollAnimator::notifyCompositorAnimationAborted(int groupId) {
  // An animation aborted by the compositor is treated as a finished
  // animation.
  ScrollAnimatorCompositorCoordinator::compositorAnimationFinished(groupId);
}

void ScrollAnimator::notifyCompositorAnimationFinished(int groupId) {
  ScrollAnimatorCompositorCoordinator::compositorAnimationFinished(groupId);
}

void ScrollAnimator::notifyAnimationTakeover(
    double monotonicTime,
    double animationStartTime,
    std::unique_ptr<cc::AnimationCurve> curve) {
  // If there is already an animation running and the compositor asks to take
  // over an animation, do nothing to avoid judder.
  if (hasRunningAnimation())
    return;

  cc::ScrollOffsetAnimationCurve* scrollOffsetAnimationCurve =
      curve->ToScrollOffsetAnimationCurve();
  ScrollOffset targetValue(scrollOffsetAnimationCurve->target_value().x(),
                           scrollOffsetAnimationCurve->target_value().y());
  if (willAnimateToOffset(targetValue)) {
    m_animationCurve = CompositorScrollOffsetAnimationCurve::create(
        std::move(scrollOffsetAnimationCurve));
    m_startTime = animationStartTime;
  }
}

void ScrollAnimator::cancelAnimation() {
  ScrollAnimatorCompositorCoordinator::cancelAnimation();
}

void ScrollAnimator::takeOverCompositorAnimation() {
  if (m_runState == RunState::RunningOnCompositor ||
      m_runState == RunState::RunningOnCompositorButNeedsUpdate)
    removeMainThreadScrollingReason();

  ScrollAnimatorCompositorCoordinator::takeOverCompositorAnimation();
}

void ScrollAnimator::layerForCompositedScrollingDidChange(
    CompositorAnimationTimeline* timeline) {
  if (reattachCompositorPlayerIfNeeded(timeline) && m_animationCurve)
    addMainThreadScrollingReason();
}

bool ScrollAnimator::registerAndScheduleAnimation() {
  getScrollableArea()->registerForAnimation();
  if (!m_scrollableArea->scheduleAnimation()) {
    scrollToOffsetWithoutAnimation(m_targetOffset);
    resetAnimationState();
    return false;
  }
  return true;
}

DEFINE_TRACE(ScrollAnimator) {
  ScrollAnimatorBase::trace(visitor);
}

}  // namespace blink