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#include "qdeclarativeeasefollow_p.h"

#include "qdeclarativeanimation_p_p.h"

#include <qdeclarativemetaproperty.h>

#include <QtCore/qdebug.h>

#include <math.h>

QT_BEGIN_NAMESPACE



class QDeclarativeEaseFollowPrivate : public QObjectPrivate
{
    Q_DECLARE_PUBLIC(QDeclarativeEaseFollow)
public:
    QDeclarativeEaseFollowPrivate()
        : source(0), velocity(200), duration(-1), maximumEasingTime(-1),
          reversingMode(QDeclarativeEaseFollow::Eased), initialVelocity(0), 
          initialValue(0), invert(false), enabled(true), trackVelocity(0), clockOffset(0),
          lastTick(0), clock(this)
    {} 

    qreal source;
    qreal velocity;
    qreal duration;
    qreal maximumEasingTime;
    QDeclarativeEaseFollow::ReversingMode reversingMode;

    qreal initialVelocity;
    qreal initialValue;
    bool invert;
    bool enabled;

    qreal trackVelocity;

    QDeclarativeMetaProperty target;

    int clockOffset;
    int lastTick;
    void tick(int);
    void clockStart();
    void clockStop();
    QTickAnimationProxy<QDeclarativeEaseFollowPrivate, &QDeclarativeEaseFollowPrivate::tick> clock;

    void restart();

    // Parameters for use in tick()
    qreal a;  // Acceleration
    qreal d;  // Deceleration
    qreal tf; // Total time
    qreal tp; // Time at which peak velocity occurs
    qreal td; // Time at which decelleration begins
    qreal vp; // Velocity at tp
    qreal sp; // Displacement at tp
    qreal sd; // Displacement at td
    qreal vi; // "Normalized" initialvelocity
    bool recalc();
};

bool QDeclarativeEaseFollowPrivate::recalc()
{
    qreal s = source - initialValue;
    vi = initialVelocity;

    s = (invert?-1.0:1.0) * s;
    vi = (invert?-1.0:1.0) * vi;

    if (duration > 0 && velocity > 0) {
        tf = s / velocity;
        if (tf > (duration / 1000.)) tf = (duration / 1000.);
    } else if (duration > 0) {
        tf = duration / 1000.;
    } else if (velocity > 0) {
        tf = s / velocity;
    } else {
        return false;
    }

    if (maximumEasingTime == 0) {
        a = 0;
        d = 0;
        tp = 0;
        td = tf;
        vp = velocity;
        sp = 0;
        sd = s;
    } else if (maximumEasingTime != -1 && tf > (maximumEasingTime / 1000.)) {

        qreal met = maximumEasingTime / 1000.;
        td = tf - met;

        qreal c1 = td;
        qreal c2 = (tf - td) * vi - tf * velocity;
        qreal c3 = -0.5 * (tf - td) * vi * vi;

        qreal vp1 = (-c2 + sqrt(c2 * c2 - 4 * c1 * c3)) / (2. * c1);
        // qreal vp2 = (-c2 - sqrt(c2 * c2 - 4 * c1 * c3)) / (2. * c1);

        vp = vp1;
        a = vp / met;
        d = a;
        tp = (vp - vi) / a;
        sp = vi * tp + 0.5 * a * tp * tp;
        sd = sp + (td - tp) * vp;
    } else {

        qreal c1 = 0.25 * tf * tf;
        qreal c2 = 0.5 * vi * tf - s;
        qreal c3 = -0.25 * vi * vi;

        qreal a1 = (-c2 + sqrt(c2 * c2 - 4 * c1 * c3)) / (2. * c1);
        //qreal a2 = (-c2 - sqrt(c2 * c2 - 4 * c1 * c3)) / (2. * c1);

        qreal tp1 = 0.5 * tf - 0.5 * vi / a1;
        //qreal tp2 = 0.5 * tf - 0.5 * vi / a2;
        qreal vp1 = a1 * tp1 + vi;
        //qreal vp2 = a2 * tp2 + vi;

        qreal sp1 = 0.5 * a1 * tp1 * tp1 + vi * tp1;
        //qreal sp2 = 0.5 * a2 * tp2 * tp2 + vi * tp2;

        a = a1;
        d = a1;
        tp = tp1;
        td = tp1;
        vp = vp1;
        sp = sp1;
        sd = sp1;
    }

    /*
    qWarning() << "a:" << a << "tf:" << tf << "tp:" << tp << "vp:" 
               << vp << "sp:" << sp << "vi:" << vi << "invert:" << invert;
    */
    return true;
}

void QDeclarativeEaseFollowPrivate::clockStart()
{
    if (clock.state() == QAbstractAnimation::Running) {
        clockOffset = lastTick;
        return;
    } else {
        clockOffset = 0;
        lastTick = 0;
        clock.start();
    }
}

void QDeclarativeEaseFollowPrivate::clockStop()
{
    clockOffset = 0;
    lastTick = 0;
    clock.stop();
}

void QDeclarativeEaseFollowPrivate::tick(int t)
{
    lastTick = t;
    t -= clockOffset;

    qreal time_seconds = qreal(t) / 1000.;

    qreal out = 0;
    if (time_seconds < tp) {

        trackVelocity = vi + time_seconds * a;
        trackVelocity = (invert?-1.0:1.0) * trackVelocity;

        qreal value = 0.5 * a * time_seconds * time_seconds + vi * time_seconds;
        value = (invert?-1.0:1.0) * value;
        target.write(initialValue + value);
        out = initialValue + value;
    } else if (time_seconds < td) {

        time_seconds -= tp;
        trackVelocity = (invert?-1.0:1.0) * vp;
        qreal value = sp + time_seconds * vp;
        value = (invert?-1.0:1.0) * value;

        target.write(initialValue + value);

        out = initialValue + value;
    } else if (time_seconds < tf) {

        time_seconds -= td;

        trackVelocity = vp - time_seconds * a;
        trackVelocity = (invert?-1.0:1.0) * trackVelocity;

        qreal value = sd - 0.5 * d * time_seconds * time_seconds + vp * time_seconds;
        value = (invert?-1.0:1.0) * value;

        target.write(initialValue + value);

        out = initialValue + value;
    } else {

        clock.stop();

        trackVelocity = 0;
        target.write(source);
    }

    //qWarning() << out << trackVelocity << t << a;
}

/*!
    \qmlclass EaseFollow QDeclarativeEaseFollow
    \brief The EaseFollow element allows a property to smoothly track a value.

    The EaseFollow smoothly animates a property's value to a set target value 
    using an ease in/out quad easing curve.  If the target value changes while
    the animation is in progress, the easing curves used to animate to the old 
    and the new target values are spliced together to avoid any obvious visual
    glitches.

    The property animation is configured by setting the velocity at which the
    animation should occur, or the duration that the animation should take.  
    If both a velocity and a duration are specified, the one that results in
    the quickest animation is chosen for each change in the target value.

    For example, animating from 0 to 800 will take 4 seconds if a velocity
    of 200 is set, will take 8 seconds with a duration of 8000 set, and will 
    take 4 seconds with both a velocity of 200 and a duration of 8000 set.
    Animating from 0 to 20000 will take 10 seconds if a velocity of 200 is set,
    will take 8 seconds with a duration of 8000 set, and will take 8 seconds
    with both a velocity of 200 and a duration of 8000 set.

    The follow example shows one rectangle tracking the position of another.
\code
import Qt 4.6

Rectangle {
    width: 800; height: 600; color: "blue"

    Rectangle {
        color: "green"
        width: 60; height: 60;
        x: -5; y: -5;
        x: EaseFollow { source: rect1.x - 5; velocity: 200 }
        y: EaseFollow { source: rect1.y - 5; velocity: 200 }
    }

    Rectangle {
        id: rect1
        color: "red"
        width: 50; height: 50;
    }

    focus: true
    Keys.onRightPressed: rect1.x = rect1.x + 100
    Keys.onLeftPressed: rect1.x = rect1.x - 100
    Keys.onUpPressed: rect1.y = rect1.y - 100
    Keys.onDownPressed: rect1.y = rect1.y + 100
}
\endcode

    The default velocity of EaseFollow is 200 units/second.  Note that if the range of the
    value being animated is small, then the velocity will need to be adjusted
    appropriately.  For example, the opacity of an item ranges from 0 - 1.0.
    To enable a smooth animation in this range the velocity will need to be
    set to a value such as 0.5 units/second.  Animating from 0 to 1.0 with a velocity
    of 0.5 will take 2000 ms to complete.

    \sa SpringFollow
*/

QDeclarativeEaseFollow::QDeclarativeEaseFollow(QObject *parent)
: QObject(*(new QDeclarativeEaseFollowPrivate), parent)
{
}

QDeclarativeEaseFollow::~QDeclarativeEaseFollow()
{
}

/*!
    \qmlproperty qreal EaseFollow::source
    This property holds the source value which will be tracked.

    Bind to a property in order to track its changes.
*/
qreal QDeclarativeEaseFollow::sourceValue() const
{
    Q_D(const QDeclarativeEaseFollow);
    return d->source;
}

/*!
    \qmlproperty enumeration EaseFollow::reversingMode

    Sets how the EaseFollow behaves if an animation direction is reversed.

    If reversing mode is \c Eased, the animation will smoothly decelerate, and
    then reverse direction.  If the reversing mode is \c Immediate, the 
    animation will immediately begin accelerating in the reverse direction, 
    begining with a velocity of 0.  If the reversing mode is \c Sync, the
    property is immediately set to the target value.
*/
QDeclarativeEaseFollow::ReversingMode QDeclarativeEaseFollow::reversingMode() const
{
    Q_D(const QDeclarativeEaseFollow);
    return d->reversingMode;
}

void QDeclarativeEaseFollow::setReversingMode(ReversingMode m)
{
    Q_D(QDeclarativeEaseFollow);
    if (d->reversingMode == m)
        return;

    d->reversingMode = m;
    emit reversingModeChanged();
}

void QDeclarativeEaseFollowPrivate::restart()
{
    if (!enabled || velocity == 0) {
        clockStop();
        return;
    }

    initialValue = target.read().toReal();

    if (source == initialValue) {
        clockStop();
        return;
    }

    bool hasReversed = trackVelocity != 0. && 
                      ((trackVelocity > 0) == ((initialValue - source) > 0));

    if (hasReversed) {
        switch (reversingMode) {
            default:
            case QDeclarativeEaseFollow::Eased:
                break;
            case QDeclarativeEaseFollow::Sync:
                target.write(source);
                return;
            case QDeclarativeEaseFollow::Immediate:
                initialVelocity = 0;
                clockStop();
                break;
        }
    }

    trackVelocity = initialVelocity;

    invert = (source < initialValue);

    if (!recalc()) {
        target.write(source);
        clockStop();
        return;
    }

    clockStart();
}

void QDeclarativeEaseFollow::setSourceValue(qreal s)
{
    Q_D(QDeclarativeEaseFollow);

    if (d->clock.state() == QAbstractAnimation::Running && d->source == s)
        return;

    d->source = s;
    d->initialVelocity = d->trackVelocity;
    d->restart();

    emit sourceChanged();
}

/*!
    \qmlproperty qreal EaseFollow::duration

    This property holds the animation duration used when tracking the source.

    Setting this to -1 (the default) disables the duration value.
*/
qreal QDeclarativeEaseFollow::duration() const
{
    Q_D(const QDeclarativeEaseFollow);
    return d->duration;
}

void QDeclarativeEaseFollow::setDuration(qreal v)
{
    Q_D(QDeclarativeEaseFollow);
    if (d->duration == v)
        return;

    d->duration = v;
    d->trackVelocity = 0;

    if (d->clock.state() == QAbstractAnimation::Running) 
        d->restart();

    emit durationChanged();
}

qreal QDeclarativeEaseFollow::velocity() const
{
    Q_D(const QDeclarativeEaseFollow);
    return d->velocity;
}

/*!
    \qmlproperty qreal EaseFollow::velocity

    This property holds the average velocity allowed when tracking the source.

    The default velocity of EaseFollow is 200 units/second.

    Setting this to -1 disables the velocity value.
*/
void QDeclarativeEaseFollow::setVelocity(qreal v)
{
    Q_D(QDeclarativeEaseFollow);
    if (d->velocity == v)
        return;

    d->velocity = v;
    d->trackVelocity = 0;

    if (d->clock.state() == QAbstractAnimation::Running) 
        d->restart();

    emit velocityChanged();
}

/*!
    \qmlproperty bool EaseFollow::enabled
    This property holds whether the target will track the source.
*/
bool QDeclarativeEaseFollow::enabled() const
{
    Q_D(const QDeclarativeEaseFollow);
    return d->enabled;
}

void QDeclarativeEaseFollow::setEnabled(bool enabled)
{
    Q_D(QDeclarativeEaseFollow);
    if (d->enabled == enabled)
        return;

    d->enabled = enabled;
    if (enabled)
        d->restart();
    else
        d->clockStop();

    emit enabledChanged();
}

void QDeclarativeEaseFollow::setTarget(const QDeclarativeMetaProperty &t)
{
    Q_D(QDeclarativeEaseFollow);
    d->target = t;
}

/*!
\qmlproperty qreal EaseFollow::maximumEasingTime

This property specifies the maximum time an "eases" during the follow should take.
Setting this property causes the velocity to "level out" after at a time.  Setting 
a negative value reverts to the normal mode of easing over the entire animation 
duration.

The default value is -1.
*/
qreal QDeclarativeEaseFollow::maximumEasingTime() const
{
    Q_D(const QDeclarativeEaseFollow);
    return d->maximumEasingTime;
}

void QDeclarativeEaseFollow::setMaximumEasingTime(qreal v)
{
    Q_D(QDeclarativeEaseFollow);
    d->maximumEasingTime = v;

    if (d->clock.state() == QAbstractAnimation::Running) 
        d->restart();

    emit maximumEasingTimeChanged();
}

QT_END_NAMESPACE