path: root/src/declarative/util/qdeclarativespringanimation.cpp

/****************************************************************************
**
** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtDeclarative module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

#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){}
        qreal currentValue;
        qreal to;
        qreal velocity;
    };
    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 > 0.) {
                // limit velocity
                if (animation.velocity > maxVelocity)
                    animation.velocity = maxVelocity;
                else if (animation.velocity < -maxVelocity)
                    animation.velocity = -maxVelocity;
            }
            animation.currentValue += animation.velocity * 16.0 / 1000.0;
            if (haveModulus) {
                animation.currentValue = fmod(animation.currentValue, modulus);
                if (animation.currentValue < 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);
            if (animation.currentValue > animation.to) {
                animation.currentValue = animation.to;
                stop = true;
            }
        } else {
            animation.currentValue -= moveBy;
            if (haveModulus && animation.currentValue < 0.0)
                animation.currentValue = fmod(animation.currentValue, modulus) + modulus;
            if (animation.currentValue < animation.to) {
                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;
}

/*!
    \qmlclass SpringAnimation QDeclarativeSpringAnimation
    \inherits Animation
    \since 4.7

    \brief The SpringAnimation element allows a property to track a value in a spring-like motion.

    SpringAnimation mimics the oscillatory behavior of a spring, with the appropriate \l spring constant to
    control the acceleration and the \l damping to control how quickly the effect dies away.

    You can also limit the maximum \l velocity of the animation.

    The following \l Rectangle moves to the position of the mouse using a 
    SpringAnimation when the mouse is clicked. The use of the \l Behavior
    on the \c x and \c y values indicates that whenever these values are 
    changed, a SpringAnimation should be applied.

    \snippet doc/src/snippets/declarative/springanimation.qml 0

    Like any other animation element, a SpringAnimation can be applied in a
    number of ways, including transitions, behaviors and property value 
    sources. The \l {QML Animation} documentation shows a variety of methods
    for creating animations.

    \sa SmoothedAnimation, {QML Animation}, {declarative/animation/basics}{Animation basics example}, {declarative/toys/clocks}{Clocks example}
*/

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

QDeclarativeSpringAnimation::~QDeclarativeSpringAnimation()
{
}

/*!
    \qmlproperty real SpringAnimation::velocity

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

    The default value is 0 (no maximum velocity).
*/

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();
}

/*!
    \qmlproperty real SpringAnimation::spring

    This property describes how strongly the target is pulled towards the
    source. The default value is 0 (that is, the spring-like motion is disabled).
    
    The useful value range is 0 - 5.0.

    When this property is set and the \l velocity value is greater than 0,
    the \l velocity limits the maximum speed.
*/
qreal QDeclarativeSpringAnimation::spring() const
{
    Q_D(const QDeclarativeSpringAnimation);
    return d->spring;
}

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

/*!
    \qmlproperty real SpringAnimation::damping
    This property holds the spring damping value.

    This value describes how quickly the spring-like motion comes to rest.
    The default value is 0.

    The useful value range is 0 - 1.0. The lower the value, the faster it
    comes to rest.
*/
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;
}


/*!
    \qmlproperty real SpringAnimation::epsilon
    This property holds the spring epsilon.

    The epsilon is the rate and amount of change in the value which is close enough
    to 0 to be considered equal to zero. This will depend on the usage of the value.
    For pixel positions, 0.25 would suffice. For scale, 0.005 will suffice.

    The default is 0.01. Tuning this value can provide small performance improvements.
*/
qreal QDeclarativeSpringAnimation::epsilon() const
{
    Q_D(const QDeclarativeSpringAnimation);
    return d->epsilon;
}

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

/*!
    \qmlproperty real SpringAnimation::modulus
    This property holds the modulus value. The default value is 0.

    Setting a \a modulus forces the target value to "wrap around" at the modulus.
    For example, setting the modulus to 360 will cause a value of 370 to wrap around to 10.
*/
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;
        emit modulusChanged();
    }
}

/*!
    \qmlproperty real SpringAnimation::mass
    This property holds the "mass" of the property being moved.

    The value is 1.0 by default. 
    
    A greater mass causes slower movement and a greater spring-like 
    motion when an item comes to rest.
*/
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();
            if (d->fromIsDefined)
                animation.currentValue = d->actions->at(i).fromValue.toReal();
            else
                animation.currentValue = property.read().toReal();
        }
    }
}


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

QT_END_NAMESPACE