haikuwebkit/Source/WebCore/platform/ScrollSnapAnimatorState.cpp

/*
 * Copyright (C) 2014-2015 Apple Inc. All rights reserved.
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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
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 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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#include "config.h"
#include "ScrollSnapAnimatorState.h"

#include <wtf/MathExtras.h>
#include <wtf/text/TextStream.h>

namespace WebCore {

void ScrollSnapAnimatorState::transitionToSnapAnimationState(const FloatSize& contentSize, const FloatSize& viewportSize, float pageScale, const FloatPoint& initialOffset)
{
    setupAnimationForState(ScrollSnapState::Snapping, contentSize, viewportSize, pageScale, initialOffset, { }, { });
}

void ScrollSnapAnimatorState::transitionToGlideAnimationState(const FloatSize& contentSize, const FloatSize& viewportSize, float pageScale, const FloatPoint& initialOffset, const FloatSize& initialVelocity, const FloatSize& initialDelta)
{
    setupAnimationForState(ScrollSnapState::Gliding, contentSize, viewportSize, pageScale, initialOffset, initialVelocity, initialDelta);
}

void ScrollSnapAnimatorState::setupAnimationForState(ScrollSnapState state, const FloatSize& contentSize, const FloatSize& viewportSize, float pageScale, const FloatPoint& initialOffset, const FloatSize& initialVelocity, const FloatSize& initialDelta)
{
    ASSERT(state == ScrollSnapState::Snapping || state == ScrollSnapState::Gliding);
    if (m_currentState == state)
        return;

    m_momentumCalculator = ScrollingMomentumCalculator::create(viewportSize, contentSize, initialOffset, initialDelta, initialVelocity);
    FloatPoint predictedScrollTarget { m_momentumCalculator->predictedDestinationOffset() };

    float targetOffsetX, targetOffsetY;
    std::tie(targetOffsetX, m_activeSnapIndexX) = targetOffsetForStartOffset(ScrollEventAxis::Horizontal, viewportSize, contentSize.width() - viewportSize.width(), initialOffset.x(), predictedScrollTarget, pageScale, initialDelta.width());
    std::tie(targetOffsetY, m_activeSnapIndexY) = targetOffsetForStartOffset(ScrollEventAxis::Vertical, viewportSize, contentSize.height() - viewportSize.height(), initialOffset.y(), predictedScrollTarget, pageScale, initialDelta.height());
    m_momentumCalculator->setRetargetedScrollOffset({ targetOffsetX, targetOffsetY });
    m_startTime = MonotonicTime::now();
    m_currentState = state;
}

void ScrollSnapAnimatorState::transitionToUserInteractionState()
{
    teardownAnimationForState(ScrollSnapState::UserInteraction);
}

void ScrollSnapAnimatorState::transitionToDestinationReachedState()
{
    teardownAnimationForState(ScrollSnapState::DestinationReached);
}

void ScrollSnapAnimatorState::teardownAnimationForState(ScrollSnapState state)
{
    ASSERT(state == ScrollSnapState::UserInteraction || state == ScrollSnapState::DestinationReached);
    if (m_currentState == state)
        return;

    m_momentumCalculator = nullptr;
    m_startTime = MonotonicTime();
    m_currentState = state;
}

FloatPoint ScrollSnapAnimatorState::currentAnimatedScrollOffset(MonotonicTime currentTime, bool& isAnimationComplete) const
{
    if (!m_momentumCalculator) {
        isAnimationComplete = true;
        return { };
    }

    Seconds elapsedTime = currentTime - m_startTime;
    isAnimationComplete = elapsedTime >= m_momentumCalculator->animationDuration();
    return m_momentumCalculator->scrollOffsetAfterElapsedTime(elapsedTime);
}

std::pair<float, std::optional<unsigned>> ScrollSnapAnimatorState::targetOffsetForStartOffset(ScrollEventAxis axis, const FloatSize& viewportSize, float maxScrollOffset, float startOffset, FloatPoint predictedOffset, float pageScale, float initialDelta) const
{
    const auto& snapOffsets = m_snapOffsetsInfo.offsetsForAxis(axis);
    if (snapOffsets.isEmpty())
        return std::make_pair(clampTo<float>(axis == ScrollEventAxis::Horizontal ? predictedOffset.x() : predictedOffset.y(), 0, maxScrollOffset), std::nullopt);

    LayoutPoint predictedLayoutOffset(predictedOffset.x() / pageScale, predictedOffset.y() / pageScale);
    auto [targetOffset, snapIndex] = m_snapOffsetsInfo.closestSnapOffset(axis, LayoutSize { viewportSize }, predictedLayoutOffset, initialDelta, LayoutUnit(startOffset / pageScale));
    return std::make_pair(pageScale * clampTo<float>(float { targetOffset }, 0, maxScrollOffset), snapIndex);
}

TextStream& operator<<(TextStream& ts, const ScrollSnapAnimatorState& state)
{
    ts << "ScrollSnapAnimatorState";
    ts.dumpProperty("snap offsets x", state.snapOffsetsForAxis(ScrollEventAxis::Horizontal));
    ts.dumpProperty("snap offsets y", state.snapOffsetsForAxis(ScrollEventAxis::Vertical));

    ts.dumpProperty("active snap index x", state.activeSnapIndexForAxis(ScrollEventAxis::Horizontal));
    ts.dumpProperty("active snap index y", state.activeSnapIndexForAxis(ScrollEventAxis::Vertical));

    return ts;
}

} // namespace WebCore