qdeclarativespringanimation.cpp

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#include "private/qdeclarativespringanimation_p.h"

#include "private/qdeclarativeanimation_p_p.h"
#include <qdeclarativeproperty_p.h>

#include <QtCore/qdebug.h>

#include <private/qobject_p.h>

#include <limits.h>
#include <math.h>

QT_BEGIN_NAMESPACE


class QDeclarativeSpringAnimationPrivate : public QDeclarativePropertyAnimationPrivate
{
    Q_DECLARE_PUBLIC(QDeclarativeSpringAnimation)
public:


    struct SpringAnimation {
        SpringAnimation()
            : currentValue(0), to(0), velocity(0), start(0), duration(0) {}
        qreal currentValue;
        qreal to;
        qreal velocity;
        int start;
        int duration;
    };
    QHash<QDeclarativeProperty, SpringAnimation> activeAnimations;

    qreal maxVelocity;
    qreal velocityms;
    int lastTime;
    qreal mass;
    qreal spring;
    qreal damping;
    qreal epsilon;
    qreal modulus;

    bool useMass : 1;
    bool haveModulus : 1;

    enum Mode {
        Track,
        Velocity,
        Spring
    };
    Mode mode;

    QDeclarativeSpringAnimationPrivate()
          : maxVelocity(0), velocityms(0), lastTime(0)
          , mass(1.0), spring(0.), damping(0.), epsilon(0.01)
          , modulus(0.0), useMass(false), haveModulus(false)
          , mode(Track), clock(0)
    { }

    void tick(int time);
    bool animate(const QDeclarativeProperty &property, SpringAnimation &animation, int elapsed);
    void updateMode();

    typedef QTickAnimationProxy<QDeclarativeSpringAnimationPrivate, &QDeclarativeSpringAnimationPrivate::tick> Clock;
    Clock *clock;
};

void QDeclarativeSpringAnimationPrivate::tick(int time)
{
    if (mode == Track) {
        clock->stop();
        return;
    }
    int elapsed = time - lastTime;
    if (!elapsed)
        return;

    if (mode == Spring) {
        if (elapsed < 16) // capped at 62fps.
            return;
        int count = elapsed / 16;
        lastTime = time - (elapsed - count * 16);
    } else {
        lastTime = time;
    }

    QMutableHashIterator<QDeclarativeProperty, SpringAnimation> it(activeAnimations);
    while (it.hasNext()) {
        it.next();
        if (animate(it.key(), it.value(), elapsed))
            it.remove();
    }

    if (activeAnimations.isEmpty())
        clock->stop();
}

bool QDeclarativeSpringAnimationPrivate::animate(const QDeclarativeProperty &property, SpringAnimation &animation, int elapsed)
{
    qreal srcVal = animation.to;

    bool stop = false;

    if (haveModulus) {
        animation.currentValue = fmod(animation.currentValue, modulus);
        srcVal = fmod(srcVal, modulus);
    }
    if (mode == Spring) {
        // Real men solve the spring DEs using RK4.
        // We'll do something much simpler which gives a result that looks fine.
        int count = elapsed / 16;
        for (int i = 0; i < count; ++i) {
            qreal diff = srcVal - animation.currentValue;
            if (haveModulus && qAbs(diff) > modulus / 2) {
                if (diff < 0)
                    diff += modulus;
                else
                    diff -= modulus;
            }
            if (useMass)
                animation.velocity = animation.velocity + (spring * diff - damping * animation.velocity) / mass;
            else
                animation.velocity = animation.velocity + spring * diff - damping * animation.velocity;
            if (maxVelocity > qreal(0.)) {
                // limit velocity
                if (animation.velocity > maxVelocity)
                    animation.velocity = maxVelocity;
                else if (animation.velocity < -maxVelocity)
                    animation.velocity = -maxVelocity;
            }
            animation.currentValue += animation.velocity * qreal(16.0) / qreal(1000.0);
            if (haveModulus) {
                animation.currentValue = fmod(animation.currentValue, modulus);
                if (animation.currentValue < qreal(0.0))
                    animation.currentValue += modulus;
            }
        }
        if (qAbs(animation.velocity) < epsilon && qAbs(srcVal - animation.currentValue) < epsilon) {
            animation.velocity = 0.0;
            animation.currentValue = srcVal;
            stop = true;
        }
    } else {
        qreal moveBy = elapsed * velocityms;
        qreal diff = srcVal - animation.currentValue;
        if (haveModulus && qAbs(diff) > modulus / 2) {
            if (diff < 0)
                diff += modulus;
            else
                diff -= modulus;
        }
        if (diff > 0) {
            animation.currentValue += moveBy;
            if (haveModulus)
                animation.currentValue = fmod(animation.currentValue, modulus);
        } else {
            animation.currentValue -= moveBy;
            if (haveModulus && animation.currentValue < qreal(0.0))
                animation.currentValue = fmod(animation.currentValue, modulus) + modulus;
        }
        if (lastTime - animation.start >= animation.duration) {
            animation.currentValue = animation.to;
            stop = true;
        }
    }

    qreal old_to = animation.to;

    QDeclarativePropertyPrivate::write(property, animation.currentValue,
                                       QDeclarativePropertyPrivate::BypassInterceptor |
                                       QDeclarativePropertyPrivate::DontRemoveBinding);

    return (stop && old_to == animation.to); // do not stop if we got restarted
}

void QDeclarativeSpringAnimationPrivate::updateMode()
{
    if (spring == 0. && maxVelocity == 0.)
        mode = Track;
    else if (spring > 0.)
        mode = Spring;
    else {
        mode = Velocity;
        QHash<QDeclarativeProperty, SpringAnimation>::iterator it;
        for (it = activeAnimations.begin(); it != activeAnimations.end(); ++it) {
            SpringAnimation &animation = *it;
            animation.start = lastTime;
            qreal dist = qAbs(animation.currentValue - animation.to);
            if (haveModulus && dist > modulus / 2)
                dist = modulus - fmod(dist, modulus);
            animation.duration = dist / velocityms;
        }
    }
}

QDeclarativeSpringAnimation::QDeclarativeSpringAnimation(QObject *parent)
: QDeclarativeNumberAnimation(*(new QDeclarativeSpringAnimationPrivate),parent)
{
    Q_D(QDeclarativeSpringAnimation);
    d->clock = new QDeclarativeSpringAnimationPrivate::Clock(d, this);
}

QDeclarativeSpringAnimation::~QDeclarativeSpringAnimation()
{
}

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

void QDeclarativeSpringAnimation::setVelocity(qreal velocity)
{
    Q_D(QDeclarativeSpringAnimation);
    d->maxVelocity = velocity;
    d->velocityms = velocity / 1000.0;
    d->updateMode();
}

qreal QDeclarativeSpringAnimation::spring() const
{
    Q_D(const QDeclarativeSpringAnimation);
    return d->spring;
}

void QDeclarativeSpringAnimation::setSpring(qreal spring)
{
    Q_D(QDeclarativeSpringAnimation);
    d->spring = spring;
    d->updateMode();
}

qreal QDeclarativeSpringAnimation::damping() const
{
    Q_D(const QDeclarativeSpringAnimation);
    return d->damping;
}

void QDeclarativeSpringAnimation::setDamping(qreal damping)
{
    Q_D(QDeclarativeSpringAnimation);
    if (damping > 1.)
        damping = 1.;

    d->damping = damping;
}


qreal QDeclarativeSpringAnimation::epsilon() const
{
    Q_D(const QDeclarativeSpringAnimation);
    return d->epsilon;
}

void QDeclarativeSpringAnimation::setEpsilon(qreal epsilon)
{
    Q_D(QDeclarativeSpringAnimation);
    d->epsilon = epsilon;
}

qreal QDeclarativeSpringAnimation::modulus() const
{
    Q_D(const QDeclarativeSpringAnimation);
    return d->modulus;
}

void QDeclarativeSpringAnimation::setModulus(qreal modulus)
{
    Q_D(QDeclarativeSpringAnimation);
    if (d->modulus != modulus) {
        d->haveModulus = modulus != 0.0;
        d->modulus = modulus;
        d->updateMode();
        emit modulusChanged();
    }
}

qreal QDeclarativeSpringAnimation::mass() const
{
    Q_D(const QDeclarativeSpringAnimation);
    return d->mass;
}

void QDeclarativeSpringAnimation::setMass(qreal mass)
{
    Q_D(QDeclarativeSpringAnimation);
    if (d->mass != mass && mass > 0.0) {
        d->useMass = mass != 1.0;
        d->mass = mass;
        emit massChanged();
    }
}

void QDeclarativeSpringAnimation::transition(QDeclarativeStateActions &actions,
                                             QDeclarativeProperties &modified,
                                             TransitionDirection direction)
{
    Q_D(QDeclarativeSpringAnimation);
    Q_UNUSED(direction);

    if (d->clock->state() != QAbstractAnimation::Running) {
        d->lastTime = 0;
    }

    QDeclarativeNumberAnimation::transition(actions, modified, direction);

    if (!d->actions)
        return;

    if (!d->actions->isEmpty()) {
        for (int i = 0; i < d->actions->size(); ++i) {
            const QDeclarativeProperty &property = d->actions->at(i).property;
            QDeclarativeSpringAnimationPrivate::SpringAnimation &animation
                    = d->activeAnimations[property];
            animation.to = d->actions->at(i).toValue.toReal();
            animation.start = d->lastTime;
            if (d->fromIsDefined)
                animation.currentValue = d->actions->at(i).fromValue.toReal();
            else
                animation.currentValue = property.read().toReal();
            if (d->mode == QDeclarativeSpringAnimationPrivate::Velocity) {
                qreal dist = qAbs(animation.currentValue - animation.to);
                if (d->haveModulus && dist > d->modulus / 2)
                    dist = d->modulus - fmod(dist, d->modulus);
                animation.duration = dist / d->velocityms;
            }
        }
    }
}


QAbstractAnimation *QDeclarativeSpringAnimation::qtAnimation()
{
    Q_D(QDeclarativeSpringAnimation);
    return d->clock;
}

QT_END_NAMESPACE