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/*!
    \class QGraphicsItemAnimation
    \brief The QGraphicsItemAnimation class provides simple animation
    support for QGraphicsItem.
    \since 4.2
    \ingroup multimedia

    The QGraphicsItemAnimation class animates a QGraphicsItem. You can
    schedule changes to the item's transformation matrix at
    specified steps. The QGraphicsItemAnimation class has a 
    current step value. When this value changes the transformations 
    scheduled at that step are performed. The current step of the 
    animation is set with the \c setStep() function.

    QGraphicsItemAnimation will do a simple linear interpolation
    between the nearest adjacent scheduled changes to calculate the 
    matrix. For instance, if you set the position of an item at values
    0.0 and 1.0, the animation will show the item moving in a straight
    line between these positions. The same is true for scaling and 
    rotation.

    It is usual to use the class with a QTimeLine. The timeline's
    \l{QTimeLine::}{valueChanged()} signal is then connected to the 
    \c setStep() slot. For example, you can set up an item for rotation
    by calling \c setRotationAt() for different step values.
    The animations timeline is set with the setTimeLine() function.

    An example animation with a timeline follows:

    \quotefromfile snippets/timeline/main.cpp
    \skipto QGraphicsItem *ball
    \printuntil timer->start();
    
    Note that steps lie between 0.0 and 1.0. It may be necessary to use
    \l{QTimeLine::}{setUpdateInterval()}. The default update interval
    is 40 ms. A scheduled transformation cannot be removed when set,
    so scheduling several transformations of the same kind (e.g.,
    rotations) at the same step is not recommended.

    \sa QTimeLine, {The Graphics View Framework}
*/

#include "qgraphicsitemanimation.h"

#ifndef QT_NO_GRAPHICSVIEW

#include "qgraphicsitem.h"

#include <QtCore/qtimeline.h>
#include <QtCore/qpoint.h>
#include <QtGui/qmatrix.h>

class QGraphicsItemAnimationPrivate
{
public:
    inline QGraphicsItemAnimationPrivate()
        : q(0), timeLine(0), item(0), step(0)
    { }

    QGraphicsItemAnimation *q;

    QTimeLine *timeLine;
    QGraphicsItem *item;

    QPointF startPos;
    QMatrix startMatrix;

    qreal step;

    struct Pair {
        Pair(qreal a, qreal b) : step(a), value(b) {}
        bool operator <(const Pair &other) const
        { return step < other.step; }
        qreal step;
        qreal value;
    };
    QList<Pair> xPosition;
    QList<Pair> yPosition;
    QList<Pair> rotation;
    QList<Pair> verticalScale;
    QList<Pair> horizontalScale;
    QList<Pair> verticalShear;
    QList<Pair> horizontalShear;
    QList<Pair> xTranslation;
    QList<Pair> yTranslation;

    qreal linearValueForStep(qreal step, QList<Pair> *source, qreal defaultValue = 0);
};

qreal QGraphicsItemAnimationPrivate::linearValueForStep(qreal step, QList<Pair> *source, qreal defaultValue)
{
    if (source->isEmpty())
        return defaultValue;
    step = qMin<qreal>(qMax<qreal>(step, 0), 1);

    qreal stepBefore = 0;
    qreal stepAfter = 1;
    qreal valueBefore = source->first().step == 0 ? source->first().value : defaultValue;
    qreal valueAfter = source->last().value;

    // Find the closest step and value before the given step.
    for (int i = 0; i < source->size() && step > source->at(i).step; ++i) {
        stepBefore = source->at(i).step;
        valueBefore = source->at(i).value;
    }

    // Find the closest step and value after the given step.
    for (int j = source->size() - 1; j >= 0 && step < source->at(j).step; --j) {
        stepAfter = source->at(j).step;
        valueAfter = source->at(j).value;
    }

    // Do a simple linear interpolation.
    return valueBefore + (valueAfter - valueBefore) * ((step - stepBefore) / (stepAfter - stepBefore));
}

/*!
  Constructs an animation object with the given \a parent.
*/
QGraphicsItemAnimation::QGraphicsItemAnimation(QObject *parent)
    : QObject(parent), d(new QGraphicsItemAnimationPrivate)
{
    d->q = this;
}

/*!
  Destroys the animation object.
*/
QGraphicsItemAnimation::~QGraphicsItemAnimation()
{
    delete d;
}

/*!
  Returns the item on which the animation object operates.

  \sa setItem()
*/
QGraphicsItem *QGraphicsItemAnimation::item() const
{
    return d->item;
}

/*!
  Sets the specified \a item to be used in the animation.

  \sa item()
*/
void QGraphicsItemAnimation::setItem(QGraphicsItem *item)
{
    d->item = item;
    d->startPos = d->item->pos();
}

/*!
  Returns the timeline object used to control the rate at which the animation
  occurs.

  \sa setTimeLine()
*/
QTimeLine *QGraphicsItemAnimation::timeLine() const
{
    return d->timeLine;
}

/*!
  Sets the timeline object used to control the rate of animation to the \a timeLine
  specified.

  \sa timeLine()
*/
void QGraphicsItemAnimation::setTimeLine(QTimeLine *timeLine)
{
    d->timeLine = timeLine;
    connect(timeLine, SIGNAL(valueChanged(qreal)), this, SLOT(setStep(qreal)));
}

/*!
  Returns the position of the item at the given \a step value.

  \sa setPosAt()
*/
QPointF QGraphicsItemAnimation::posAt(qreal step) const
{
    if (step < 0.0 || step > 1.0)
        qWarning("QGraphicsItemAnimation::posAt: invalid step = %f", step);

    return QPointF(d->linearValueForStep(step, &d->xPosition, d->startPos.x()),
                   d->linearValueForStep(step, &d->yPosition, d->startPos.y()));
}

/*!
  \fn void QGraphicsItemAnimation::setPosAt(qreal step, const QPointF &point)

  Sets the position of the item at the given \a step value to the \a point specified.

  \sa posAt()
*/
void QGraphicsItemAnimation::setPosAt(qreal step, const QPointF &pos)
{
    if (step < 0.0 || step > 1.0) {
        qWarning("QGraphicsItemAnimation::setPosAt: invalid step = %f", step);
        return;
    }

    d->xPosition << QGraphicsItemAnimationPrivate::Pair(step, pos.x());
    d->yPosition << QGraphicsItemAnimationPrivate::Pair(step, pos.y());
    qSort(d->xPosition.begin(), d->xPosition.end());
    qSort(d->yPosition.begin(), d->yPosition.end());
}

/*!
  Returns the matrix used to transform the item at the specified \a step value.
*/
QMatrix QGraphicsItemAnimation::matrixAt(qreal step) const
{
    if (step < 0.0 || step > 1.0)
        qWarning("QGraphicsItemAnimation::matrixAt: invalid step = %f", step);

    QMatrix matrix;
    if (!d->rotation.isEmpty())
        matrix.rotate(rotationAt(step));
    if (!d->verticalScale.isEmpty())
        matrix.scale(horizontalScaleAt(step), verticalScaleAt(step));
    if (!d->verticalShear.isEmpty())
        matrix.shear(horizontalShearAt(step), verticalShearAt(step));
    if (!d->xTranslation.isEmpty())
        matrix.translate(xTranslationAt(step), yTranslationAt(step));
    return matrix;
}

/*!
  Returns the angle at which the item is rotated at the specified \a step value.

  \sa setRotationAt()
*/
qreal QGraphicsItemAnimation::rotationAt(qreal step) const
{
    if (step < 0.0 || step > 1.0)
        qWarning("QGraphicsItemAnimation::rotationAt: invalid step = %f", step);

    return d->linearValueForStep(step, &d->rotation);
}

/*!
  Sets the rotation of the item at the given \a step value to the \a angle specified.

  \sa rotationAt()
*/
void QGraphicsItemAnimation::setRotationAt(qreal step, qreal angle)
{
    if (step < 0.0 || step > 1.0) {
        qWarning("QGraphicsItemAnimation::setRotationAt: invalid step = %f", step);
        return;
    }

    d->rotation << QGraphicsItemAnimationPrivate::Pair(step, angle);
    qSort(d->rotation.begin(), d->rotation.end());
}

/*!
  Returns the horizontal translation of the item at the specified \a step value.

  \sa setTranslationAt()
*/
qreal QGraphicsItemAnimation::xTranslationAt(qreal step) const
{
    if (step < 0.0 || step > 1.0)
        qWarning("QGraphicsItemAnimation::xTranslationAt: invalid step = %f", step);

    return d->linearValueForStep(step, &d->xTranslation);
}

/*!
  Returns the vertical translation of the item at the specified \a step value.

  \sa setTranslationAt()
*/
qreal QGraphicsItemAnimation::yTranslationAt(qreal step) const
{
    if (step < 0.0 || step > 1.0)
        qWarning("QGraphicsItemAnimation::yTranslationAt: invalid step = %f", step);

    return d->linearValueForStep(step, &d->yTranslation);
}

/*!
  Sets the translation of the item at the given \a step value using the horizontal
  and vertical coordinates specified by \a dx and \a dy.

  \sa xTranslationAt(), yTranslationAt()
*/
void QGraphicsItemAnimation::setTranslationAt(qreal step, qreal dx, qreal dy)
{
    if (step < 0.0 || step > 1.0) {
        qWarning("QGraphicsItemAnimation::setTranslationAt: invalid step = %f", step);
        return;
    }

    d->xTranslation << QGraphicsItemAnimationPrivate::Pair(step, dx);
    d->yTranslation << QGraphicsItemAnimationPrivate::Pair(step, dy);
    qSort(d->xTranslation.begin(), d->xTranslation.end());
    qSort(d->yTranslation.begin(), d->yTranslation.end());
}

/*!
  Returns the vertical scale for the item at the specified \a step value.

  \sa setScaleAt()
*/
qreal QGraphicsItemAnimation::verticalScaleAt(qreal step) const
{
    if (step < 0.0 || step > 1.0)
        qWarning("QGraphicsItemAnimation::verticalScaleAt: invalid step = %f", step);

    return d->linearValueForStep(step, &d->verticalScale, 1);
}

/*!
  Returns the horizontal scale for the item at the specified \a step value.

  \sa setScaleAt()
*/
qreal QGraphicsItemAnimation::horizontalScaleAt(qreal step) const
{
    if (step < 0.0 || step > 1.0)
        qWarning("QGraphicsItemAnimation::horizontalScaleAt: invalid step = %f", step);

    return d->linearValueForStep(step, &d->horizontalScale, 1);
}

/*!
  Sets the scale of the item at the given \a step value using the horizontal and
  vertical scale factors specified by \a sx and \a sy.

  \sa verticalScaleAt(), horizontalScaleAt()
*/
void QGraphicsItemAnimation::setScaleAt(qreal step, qreal sx, qreal sy)
{
    if (step < 0.0 || step > 1.0) {
        qWarning("QGraphicsItemAnimation::setScaleAt: invalid step = %f", step);
        return;
    }

    d->horizontalScale << QGraphicsItemAnimationPrivate::Pair(step, sx);
    d->verticalScale<< QGraphicsItemAnimationPrivate::Pair(step, sy);
    qSort(d->horizontalScale.begin(), d->horizontalScale.end());
    qSort(d->verticalScale.begin(), d->verticalScale.end());
}

/*!
  Returns the vertical shear for the item at the specified \a step value.

  \sa setShearAt()
*/
qreal QGraphicsItemAnimation::verticalShearAt(qreal step) const
{
    if (step < 0.0 || step > 1.0)
        qWarning("QGraphicsItemAnimation::verticalShearAt: invalid step = %f", step);

    return d->linearValueForStep(step, &d->verticalShear, 0);
}

/*!
  Returns the horizontal shear for the item at the specified \a step value.

  \sa setShearAt()
*/
qreal QGraphicsItemAnimation::horizontalShearAt(qreal step) const
{
    if (step < 0.0 || step > 1.0)
        qWarning("QGraphicsItemAnimation::horizontalShearAt: invalid step = %f", step);

    return d->linearValueForStep(step, &d->horizontalShear, 0);
}

/*!
  Sets the shear of the item at the given \a step value using the horizontal and
  vertical shear factors specified by \a sh and \a sv.

  \sa verticalShearAt(), horizontalShearAt()
*/
void QGraphicsItemAnimation::setShearAt(qreal step, qreal sh, qreal sv)
{
    if (step < 0.0 || step > 1.0) {
        qWarning("QGraphicsItemAnimation::setShearAt: invalid step = %f", step);
        return;
    }

    d->horizontalShear << QGraphicsItemAnimationPrivate::Pair(step, sh);
    d->verticalShear << QGraphicsItemAnimationPrivate::Pair(step, sv);
    qSort(d->horizontalShear.begin(), d->horizontalShear.end());
    qSort(d->verticalShear.begin(), d->verticalShear.end());
}

/*!
  Clears the scheduled transformations used for the animation, but
  retains the item and timeline.
*/
void QGraphicsItemAnimation::clear()
{
    d->xPosition.clear();
    d->yPosition.clear();
    d->rotation.clear();
    d->verticalScale.clear();
    d->horizontalScale.clear();
    d->verticalShear.clear();
    d->horizontalShear.clear();
    d->xTranslation.clear();
    d->yTranslation.clear();
}

/*!
  \fn void QGraphicsItemAnimation::setStep(qreal step)

  Sets the current \a step value for the animation, causing the
  transformations scheduled at this step to be performed.
*/
void QGraphicsItemAnimation::setStep(qreal x)
{
    if (x < 0.0 || x > 1.0) {
        qWarning("QGraphicsItemAnimation::setStep: invalid step = %f", x);
        return;
    }

    beforeAnimationStep(x);

    d->step = x;
    if (d->item) {
        if (!d->xPosition.isEmpty() || !d->yPosition.isEmpty())
            d->item->setPos(posAt(x));
        if (!d->rotation.isEmpty()
            || !d->verticalScale.isEmpty()
            || !d->horizontalScale.isEmpty()
            || !d->verticalShear.isEmpty()
            || !d->horizontalShear.isEmpty()
            || !d->xTranslation.isEmpty()
            || !d->yTranslation.isEmpty()) {
            d->item->setMatrix(d->startMatrix * matrixAt(x));
        }
    }

    afterAnimationStep(x);
}

/*!
Resets the item to its starting position and transformation.
*/
void QGraphicsItemAnimation::reset()
{
    if (!d->item)
        return;
    d->startPos = d->item->pos();
    d->startMatrix = d->item->matrix();
}

/*!
  \fn void QGraphicsItemAnimation::beforeAnimationStep(qreal step)

  This method is meant to be overridden by subclassed that needs to
  execute additional code before a new step takes place. The
  animation \a step is provided for use in cases where the action
  depends on its value.
*/
void QGraphicsItemAnimation::beforeAnimationStep(qreal step)
{
    Q_UNUSED(step);
}

/*!
  \fn void QGraphicsItemAnimation::afterAnimationStep(qreal step)

  This method is meant to be overridden in subclasses that need to
  execute additional code after a new step has taken place. The
  animation \a step is provided for use in cases where the action
  depends on its value.
*/
void QGraphicsItemAnimation::afterAnimationStep(qreal step)
{
    Q_UNUSED(step);
}

#endif // QT_NO_GRAPHICSVIEW
