flutter_flutter/engine/platform/scroll/ScrollAnimatorNone.h

/*
 * 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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 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
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#ifndef ScrollAnimatorNone_h
#define ScrollAnimatorNone_h

#include "platform/Timer.h"
#include "platform/geometry/FloatPoint.h"
#include "platform/scroll/ScrollAnimator.h"

class ScrollAnimatorNoneTest;

namespace blink {

class PLATFORM_EXPORT ScrollAnimatorNone : public ScrollAnimator {
public:
    explicit ScrollAnimatorNone(ScrollableArea*);
    virtual ~ScrollAnimatorNone();

    virtual bool scroll(ScrollbarOrientation, ScrollGranularity, float step, float delta) OVERRIDE;
    virtual void scrollToOffsetWithoutAnimation(const FloatPoint&) OVERRIDE;

    virtual void cancelAnimations() OVERRIDE;
    virtual void serviceScrollAnimations() OVERRIDE;

    virtual void willEndLiveResize() OVERRIDE;
    virtual void didAddVerticalScrollbar(Scrollbar*) OVERRIDE;
    virtual void didAddHorizontalScrollbar(Scrollbar*) OVERRIDE;

    enum Curve {
        Linear,
        Quadratic,
        Cubic,
        Quartic,
        Bounce
    };

    struct PLATFORM_EXPORT Parameters {
        Parameters();
        Parameters(bool isEnabled, double animationTime, double repeatMinimumSustainTime, Curve attackCurve, double attackTime, Curve releaseCurve, double releaseTime, Curve coastTimeCurve, double maximumCoastTime);

        // Note that the times can be overspecified such that releaseTime or releaseTime and attackTime are greater
        // than animationTime. animationTime takes priority over releaseTime, capping it. attackTime is capped at
        // whatever time remains, or zero if none.
        bool m_isEnabled;
        double m_animationTime;
        double m_repeatMinimumSustainTime;

        Curve m_attackCurve;
        double m_attackTime;

        Curve m_releaseCurve;
        double m_releaseTime;

        Curve m_coastTimeCurve;
        double m_maximumCoastTime;
    };

protected:
    virtual void animationWillStart() { }
    virtual void animationDidFinish() { }

    Parameters parametersForScrollGranularity(ScrollGranularity) const;

    friend class ::ScrollAnimatorNoneTest;

    struct PLATFORM_EXPORT PerAxisData {
        PerAxisData(ScrollAnimatorNone* parent, float* currentPos, int visibleLength);
        void reset();
        bool updateDataFromParameters(float step, float delta, float scrollableSize, double currentTime, Parameters*);
        bool animateScroll(double currentTime);
        void updateVisibleLength(int visibleLength);

        static double curveAt(Curve, double t);
        static double attackCurve(Curve, double deltaT, double curveT, double startPos, double attackPos);
        static double releaseCurve(Curve, double deltaT, double curveT, double releasePos, double desiredPos);
        static double coastCurve(Curve, double factor);

        static double curveIntegralAt(Curve, double t);
        static double attackArea(Curve, double startT, double endT);
        static double releaseArea(Curve, double startT, double endT);

        double newScrollAnimationPosition(double deltaTime);

        float* m_currentPosition;
        double m_currentVelocity;

        double m_desiredPosition;
        double m_desiredVelocity;

        double m_startPosition;
        double m_startTime;
        double m_startVelocity;

        double m_animationTime;
        double m_lastAnimationTime;

        double m_attackPosition;
        double m_attackTime;
        Curve m_attackCurve;

        double m_releasePosition;
        double m_releaseTime;
        Curve m_releaseCurve;

        int m_visibleLength;
    };

    void startNextTimer();
    void animationTimerFired();

    void stopAnimationTimerIfNeeded();
    bool animationTimerActive();
    void updateVisibleLengths();

    PerAxisData m_horizontalData;
    PerAxisData m_verticalData;

    double m_startTime;
    bool m_animationActive;
};

} // namespace blink

#endif // ScrollAnimatorNone_h