flutter_flutter/engine/platform/scroll/ScrollAnimatorNone.cpp

/*
 * Copyright (c) 2011, Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
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#include "config.h"

#include "platform/scroll/ScrollAnimatorNone.h"

#include <algorithm>
#include "platform/scroll/ScrollableArea.h"
#include "wtf/CurrentTime.h"
#include "wtf/PassOwnPtr.h"

#include "platform/TraceEvent.h"

namespace blink {

const double kFrameRate = 60;
const double kTickTime = 1 / kFrameRate;
const double kMinimumTimerInterval = .001;

PassOwnPtr<ScrollAnimator> ScrollAnimator::create(ScrollableArea* scrollableArea)
{
    if (scrollableArea && scrollableArea->scrollAnimatorEnabled())
        return adoptPtr(new ScrollAnimatorNone(scrollableArea));
    return adoptPtr(new ScrollAnimator(scrollableArea));
}

ScrollAnimatorNone::Parameters::Parameters()
    : m_isEnabled(false)
{
}

ScrollAnimatorNone::Parameters::Parameters(bool isEnabled, double animationTime, double repeatMinimumSustainTime, Curve attackCurve, double attackTime, Curve releaseCurve, double releaseTime, Curve coastTimeCurve, double maximumCoastTime)
    : m_isEnabled(isEnabled)
    , m_animationTime(animationTime)
    , m_repeatMinimumSustainTime(repeatMinimumSustainTime)
    , m_attackCurve(attackCurve)
    , m_attackTime(attackTime)
    , m_releaseCurve(releaseCurve)
    , m_releaseTime(releaseTime)
    , m_coastTimeCurve(coastTimeCurve)
    , m_maximumCoastTime(maximumCoastTime)
{
}

double ScrollAnimatorNone::PerAxisData::curveAt(Curve curve, double t)
{
    switch (curve) {
    case Linear:
        return t;
    case Quadratic:
        return t * t;
    case Cubic:
        return t * t * t;
    case Quartic:
        return t * t * t * t;
    case Bounce:
        // Time base is chosen to keep the bounce points simpler:
        // 1 (half bounce coming in) + 1 + .5 + .25
        const double kTimeBase = 2.75;
        const double kTimeBaseSquared = kTimeBase * kTimeBase;
        if (t < 1 / kTimeBase)
            return kTimeBaseSquared * t * t;
        if (t < 2 / kTimeBase) {
            // Invert a [-.5,.5] quadratic parabola, center it in [1,2].
            double t1 = t - 1.5 / kTimeBase;
            const double kParabolaAtEdge = 1 - .5 * .5;
            return kTimeBaseSquared * t1 * t1 + kParabolaAtEdge;
        }
        if (t < 2.5 / kTimeBase) {
            // Invert a [-.25,.25] quadratic parabola, center it in [2,2.5].
            double t2 = t - 2.25 / kTimeBase;
            const double kParabolaAtEdge = 1 - .25 * .25;
            return kTimeBaseSquared * t2 * t2 + kParabolaAtEdge;
        }
            // Invert a [-.125,.125] quadratic parabola, center it in [2.5,2.75].
        const double kParabolaAtEdge = 1 - .125 * .125;
        t -= 2.625 / kTimeBase;
        return kTimeBaseSquared * t * t + kParabolaAtEdge;
    }
    ASSERT_NOT_REACHED();
    return 0;
}

double ScrollAnimatorNone::PerAxisData::attackCurve(Curve curve, double deltaTime, double curveT, double startPosition, double attackPosition)
{
    double t = deltaTime / curveT;
    double positionFactor = curveAt(curve, t);
    return startPosition + positionFactor * (attackPosition - startPosition);
}

double ScrollAnimatorNone::PerAxisData::releaseCurve(Curve curve, double deltaTime, double curveT, double releasePosition, double desiredPosition)
{
    double t = deltaTime / curveT;
    double positionFactor = 1 - curveAt(curve, 1 - t);
    return releasePosition + (positionFactor * (desiredPosition - releasePosition));
}

double ScrollAnimatorNone::PerAxisData::coastCurve(Curve curve, double factor)
{
    return 1 - curveAt(curve, 1 - factor);
}

double ScrollAnimatorNone::PerAxisData::curveIntegralAt(Curve curve, double t)
{
    switch (curve) {
    case Linear:
        return t * t / 2;
    case Quadratic:
        return t * t * t / 3;
    case Cubic:
        return t * t * t * t / 4;
    case Quartic:
        return t * t * t * t * t / 5;
    case Bounce:
        const double kTimeBase = 2.75;
        const double kTimeBaseSquared = kTimeBase * kTimeBase;
        const double kTimeBaseSquaredOverThree = kTimeBaseSquared / 3;
        double area;
        double t1 = std::min(t, 1 / kTimeBase);
        area = kTimeBaseSquaredOverThree * t1 * t1 * t1;
        if (t < 1 / kTimeBase)
            return area;

        t1 = std::min(t - 1 / kTimeBase, 1 / kTimeBase);
        // The integral of kTimeBaseSquared * (t1 - .5 / kTimeBase) * (t1 - .5 / kTimeBase) + kParabolaAtEdge
        const double kSecondInnerOffset = kTimeBaseSquared * .5 / kTimeBase;
        double bounceArea = t1 * (t1 * (kTimeBaseSquaredOverThree * t1 - kSecondInnerOffset) + 1);
        area += bounceArea;
        if (t < 2 / kTimeBase)
            return area;

        t1 = std::min(t - 2 / kTimeBase, 0.5 / kTimeBase);
        // The integral of kTimeBaseSquared * (t1 - .25 / kTimeBase) * (t1 - .25 / kTimeBase) + kParabolaAtEdge
        const double kThirdInnerOffset = kTimeBaseSquared * .25 / kTimeBase;
        bounceArea =  t1 * (t1 * (kTimeBaseSquaredOverThree * t1 - kThirdInnerOffset) + 1);
        area += bounceArea;
        if (t < 2.5 / kTimeBase)
            return area;

        t1 = t - 2.5 / kTimeBase;
        // The integral of kTimeBaseSquared * (t1 - .125 / kTimeBase) * (t1 - .125 / kTimeBase) + kParabolaAtEdge
        const double kFourthInnerOffset = kTimeBaseSquared * .125 / kTimeBase;
        bounceArea = t1 * (t1 * (kTimeBaseSquaredOverThree * t1 - kFourthInnerOffset) + 1);
        area += bounceArea;
        return area;
    }
    ASSERT_NOT_REACHED();
    return 0;
}

double ScrollAnimatorNone::PerAxisData::attackArea(Curve curve, double startT, double endT)
{
    double startValue = curveIntegralAt(curve, startT);
    double endValue = curveIntegralAt(curve, endT);
    return endValue - startValue;
}

double ScrollAnimatorNone::PerAxisData::releaseArea(Curve curve, double startT, double endT)
{
    double startValue = curveIntegralAt(curve, 1 - endT);
    double endValue = curveIntegralAt(curve, 1 - startT);
    return endValue - startValue;
}

ScrollAnimatorNone::PerAxisData::PerAxisData(ScrollAnimatorNone* parent, float* currentPosition, int visibleLength)
    : m_currentPosition(currentPosition)
    , m_visibleLength(visibleLength)
{
    reset();
}

void ScrollAnimatorNone::PerAxisData::reset()
{
    m_currentVelocity = 0;

    m_desiredPosition = 0;
    m_desiredVelocity = 0;

    m_startPosition = 0;
    m_startTime = 0;
    m_startVelocity = 0;

    m_animationTime = 0;
    m_lastAnimationTime = 0;

    m_attackPosition = 0;
    m_attackTime = 0;
    m_attackCurve = Quadratic;

    m_releasePosition = 0;
    m_releaseTime = 0;
    m_releaseCurve = Quadratic;
}


bool ScrollAnimatorNone::PerAxisData::updateDataFromParameters(float step, float delta, float scrollableSize, double currentTime, Parameters* parameters)
{
    float pixelDelta = step * delta;
    if (!m_startTime || !pixelDelta || (pixelDelta < 0) != (m_desiredPosition - *m_currentPosition < 0)) {
        m_desiredPosition = *m_currentPosition;
        m_startTime = 0;
    }
    float newPosition = m_desiredPosition + pixelDelta;

    if (newPosition < 0 || newPosition > scrollableSize)
        newPosition = std::max(std::min(newPosition, scrollableSize), 0.0f);

    if (newPosition == m_desiredPosition)
        return false;

    m_desiredPosition = newPosition;

    if (!m_startTime) {
        m_attackTime = parameters->m_attackTime;
        m_attackCurve = parameters->m_attackCurve;
    }
    m_animationTime = parameters->m_animationTime;
    m_releaseTime = parameters->m_releaseTime;
    m_releaseCurve = parameters->m_releaseCurve;

    // Prioritize our way out of over constraint.
    if (m_attackTime + m_releaseTime > m_animationTime) {
        if (m_releaseTime > m_animationTime)
            m_releaseTime = m_animationTime;
        m_attackTime = m_animationTime - m_releaseTime;
    }

    if (!m_startTime) {
        // FIXME: This should be the time from the event that got us here.
        m_startTime = currentTime - kTickTime / 2;
        m_startPosition = *m_currentPosition;
        m_lastAnimationTime = m_startTime;
    }
    m_startVelocity = m_currentVelocity;

    double remainingDelta = m_desiredPosition - *m_currentPosition;

    double attackAreaLeft = 0;

    double deltaTime = m_lastAnimationTime - m_startTime;
    double attackTimeLeft = std::max(0., m_attackTime - deltaTime);
    double timeLeft = m_animationTime - deltaTime;
    double minTimeLeft = m_releaseTime + std::min(parameters->m_repeatMinimumSustainTime, m_animationTime - m_releaseTime - attackTimeLeft);
    if (timeLeft < minTimeLeft) {
        m_animationTime = deltaTime + minTimeLeft;
        timeLeft = minTimeLeft;
    }

    if (parameters->m_maximumCoastTime > (parameters->m_repeatMinimumSustainTime + parameters->m_releaseTime)) {
        double targetMaxCoastVelocity = m_visibleLength * .25 * kFrameRate;
        // This needs to be as minimal as possible while not being intrusive to page up/down.
        double minCoastDelta = m_visibleLength;

        if (fabs(remainingDelta) > minCoastDelta) {
            double maxCoastDelta = parameters->m_maximumCoastTime * targetMaxCoastVelocity;
            double coastFactor = std::min(1., (fabs(remainingDelta) - minCoastDelta) / (maxCoastDelta - minCoastDelta));

            // We could play with the curve here - linear seems a little soft. Initial testing makes me want to feed into the sustain time more aggressively.
            double coastMinTimeLeft = std::min(parameters->m_maximumCoastTime, minTimeLeft + coastCurve(parameters->m_coastTimeCurve, coastFactor) * (parameters->m_maximumCoastTime - minTimeLeft));

            double additionalTime = std::max(0., coastMinTimeLeft - minTimeLeft);
            if (additionalTime) {
                double additionalReleaseTime = std::min(additionalTime, parameters->m_releaseTime / (parameters->m_releaseTime + parameters->m_repeatMinimumSustainTime) * additionalTime);
                m_releaseTime = parameters->m_releaseTime + additionalReleaseTime;
                m_animationTime = deltaTime + coastMinTimeLeft;
                timeLeft = coastMinTimeLeft;
            }
        }
    }

    double releaseTimeLeft = std::min(timeLeft, m_releaseTime);
    double sustainTimeLeft = std::max(0., timeLeft - releaseTimeLeft - attackTimeLeft);

    if (attackTimeLeft) {
        double attackSpot = deltaTime / m_attackTime;
        attackAreaLeft = attackArea(m_attackCurve, attackSpot, 1) * m_attackTime;
    }

    double releaseSpot = (m_releaseTime - releaseTimeLeft) / m_releaseTime;
    double releaseAreaLeft  = releaseArea(m_releaseCurve, releaseSpot, 1) * m_releaseTime;

    m_desiredVelocity = remainingDelta / (attackAreaLeft + sustainTimeLeft + releaseAreaLeft);
    m_releasePosition = m_desiredPosition - m_desiredVelocity * releaseAreaLeft;
    if (attackAreaLeft)
        m_attackPosition = m_startPosition + m_desiredVelocity * attackAreaLeft;
    else
        m_attackPosition = m_releasePosition - (m_animationTime - m_releaseTime - m_attackTime) * m_desiredVelocity;

    if (sustainTimeLeft) {
        double roundOff = m_releasePosition - ((attackAreaLeft ? m_attackPosition : *m_currentPosition) + m_desiredVelocity * sustainTimeLeft);
        m_desiredVelocity += roundOff / sustainTimeLeft;
    }

    return true;
}

inline double ScrollAnimatorNone::PerAxisData::newScrollAnimationPosition(double deltaTime)
{
    if (deltaTime < m_attackTime)
        return attackCurve(m_attackCurve, deltaTime, m_attackTime, m_startPosition, m_attackPosition);
    if (deltaTime < (m_animationTime - m_releaseTime))
        return m_attackPosition + (deltaTime - m_attackTime) * m_desiredVelocity;
    // release is based on targeting the exact final position.
    double releaseDeltaT = deltaTime - (m_animationTime - m_releaseTime);
    return releaseCurve(m_releaseCurve, releaseDeltaT, m_releaseTime, m_releasePosition, m_desiredPosition);
}

// FIXME: Add in jank detection trace events into this function.
bool ScrollAnimatorNone::PerAxisData::animateScroll(double currentTime)
{
    double lastScrollInterval = currentTime - m_lastAnimationTime;
    if (lastScrollInterval < kMinimumTimerInterval)
        return true;

    m_lastAnimationTime = currentTime;

    double deltaTime = currentTime - m_startTime;

    if (deltaTime > m_animationTime) {
        *m_currentPosition = m_desiredPosition;
        reset();
        return false;
    }
    double newPosition = newScrollAnimationPosition(deltaTime);
    // Normalize velocity to a per second amount. Could be used to check for jank.
    if (lastScrollInterval > 0)
        m_currentVelocity = (newPosition - *m_currentPosition) / lastScrollInterval;
    *m_currentPosition = newPosition;

    return true;
}

void ScrollAnimatorNone::PerAxisData::updateVisibleLength(int visibleLength)
{
    m_visibleLength = visibleLength;
}

ScrollAnimatorNone::ScrollAnimatorNone(ScrollableArea* scrollableArea)
    : ScrollAnimator(scrollableArea)
    , m_horizontalData(this, &m_currentPosX, scrollableArea->visibleWidth())
    , m_verticalData(this, &m_currentPosY, scrollableArea->visibleHeight())
    , m_startTime(0)
    , m_animationActive(false)
{
}

ScrollAnimatorNone::~ScrollAnimatorNone()
{
    stopAnimationTimerIfNeeded();
}

ScrollAnimatorNone::Parameters ScrollAnimatorNone::parametersForScrollGranularity(ScrollGranularity granularity) const
{
    switch (granularity) {
    case ScrollByDocument:
        return Parameters(true, 20 * kTickTime, 10 * kTickTime, Cubic, 10 * kTickTime, Cubic, 10 * kTickTime, Linear, 1);
    case ScrollByLine:
        return Parameters(true, 10 * kTickTime, 7 * kTickTime, Cubic, 3 * kTickTime, Cubic, 3 * kTickTime, Linear, 1);
    case ScrollByPage:
        return Parameters(true, 15 * kTickTime, 10 * kTickTime, Cubic, 5 * kTickTime, Cubic, 5 * kTickTime, Linear, 1);
    case ScrollByPixel:
        return Parameters(true, 11 * kTickTime, 2 * kTickTime, Cubic, 3 * kTickTime, Cubic, 3 * kTickTime, Quadratic, 1.25);
    default:
        ASSERT_NOT_REACHED();
    }
    return Parameters();
}

bool ScrollAnimatorNone::scroll(ScrollbarOrientation orientation, ScrollGranularity granularity, float step, float delta)
{
    if (!m_scrollableArea->scrollAnimatorEnabled())
        return ScrollAnimator::scroll(orientation, granularity, step, delta);

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

    // FIXME: get the type passed in. MouseWheel could also be by line, but should still have different
    // animation parameters than the keyboard.
    Parameters parameters;
    switch (granularity) {
    case ScrollByDocument:
    case ScrollByLine:
    case ScrollByPage:
    case ScrollByPixel:
        parameters = parametersForScrollGranularity(granularity);
        break;
    case ScrollByPrecisePixel:
        return ScrollAnimator::scroll(orientation, granularity, step, delta);
    }

    // If the individual input setting is disabled, bail.
    if (!parameters.m_isEnabled)
        return ScrollAnimator::scroll(orientation, granularity, step, delta);

    // This is an animatable scroll. Set the animation in motion using the appropriate parameters.
    float scrollableSize = static_cast<float>(m_scrollableArea->scrollSize(orientation));

    PerAxisData& data = (orientation == VerticalScrollbar) ? m_verticalData : m_horizontalData;
    bool needToScroll = data.updateDataFromParameters(step, delta, scrollableSize, WTF::monotonicallyIncreasingTime(), &parameters);
    if (needToScroll && !animationTimerActive()) {
        m_startTime = data.m_startTime;
        animationWillStart();
        animationTimerFired();
    }
    return needToScroll;
}

void ScrollAnimatorNone::scrollToOffsetWithoutAnimation(const FloatPoint& offset)
{
    stopAnimationTimerIfNeeded();

    m_horizontalData.reset();
    *m_horizontalData.m_currentPosition = offset.x();
    m_horizontalData.m_desiredPosition = offset.x();
    m_currentPosX = offset.x();

    m_verticalData.reset();
    *m_verticalData.m_currentPosition = offset.y();
    m_verticalData.m_desiredPosition = offset.y();
    m_currentPosY = offset.y();

    notifyPositionChanged();
}

void ScrollAnimatorNone::cancelAnimations()
{
    m_animationActive = false;
}

void ScrollAnimatorNone::serviceScrollAnimations()
{
    if (m_animationActive)
        animationTimerFired();
}

void ScrollAnimatorNone::willEndLiveResize()
{
    updateVisibleLengths();
}

void ScrollAnimatorNone::didAddVerticalScrollbar(Scrollbar*)
{
    updateVisibleLengths();
}

void ScrollAnimatorNone::didAddHorizontalScrollbar(Scrollbar*)
{
    updateVisibleLengths();
}

void ScrollAnimatorNone::updateVisibleLengths()
{
    m_horizontalData.updateVisibleLength(scrollableArea()->visibleWidth());
    m_verticalData.updateVisibleLength(scrollableArea()->visibleHeight());
}

void ScrollAnimatorNone::animationTimerFired()
{
    TRACE_EVENT0("blink", "ScrollAnimatorNone::animationTimerFired");

    double currentTime = WTF::monotonicallyIncreasingTime();

    bool continueAnimation = false;
    if (m_horizontalData.m_startTime && m_horizontalData.animateScroll(currentTime))
        continueAnimation = true;
    if (m_verticalData.m_startTime && m_verticalData.animateScroll(currentTime))
        continueAnimation = true;

    if (continueAnimation)
        startNextTimer();
    else
        m_animationActive = false;

    TRACE_EVENT0("blink", "ScrollAnimatorNone::notifyPositionChanged");
    notifyPositionChanged();

    if (!continueAnimation)
        animationDidFinish();
}

void ScrollAnimatorNone::startNextTimer()
{
    if (scrollableArea()->scheduleAnimation())
        m_animationActive = true;
}

bool ScrollAnimatorNone::animationTimerActive()
{
    return m_animationActive;
}

void ScrollAnimatorNone::stopAnimationTimerIfNeeded()
{
    if (animationTimerActive())
        m_animationActive = false;
}

} // namespace blink