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#include "qdeclarativeflipable_p.h"

#include "qdeclarativeitem_p.h"
#include "qdeclarativeguard_p.h"

#include <qdeclarativeinfo.h>

#include <QtGui/qgraphicstransform.h>

QT_BEGIN_NAMESPACE

class QDeclarativeFlipablePrivate : public QDeclarativeItemPrivate
{
    Q_DECLARE_PUBLIC(QDeclarativeFlipable)
public:
    QDeclarativeFlipablePrivate() : current(QDeclarativeFlipable::Front), front(0), back(0) {}

    void updateSceneTransformFromParent();

    QDeclarativeFlipable::Side current;
    QDeclarativeGuard<QGraphicsObject> front;
    QDeclarativeGuard<QGraphicsObject> back;
};

/*!
    \qmlclass Flipable QDeclarativeFlipable
    \since 4.7
    \brief The Flipable item provides a surface that can be flipped.
    \inherits Item

    Flipable is an item that can be visibly "flipped" between its front and
    back sides. It is used together with Rotation and State/Transition to
    produce a flipping effect.

    Here is a Flipable that flips whenever it is clicked:

    \snippet examples/declarative/flipable/flipable-example.qml 0

    \image flipable.gif

    The Rotation element is used to specify the angle and axis of the flip,
    and the State defines the changes in angle which produce the flipping
    effect. Finally, the Transition creates the animation that changes the
    angle over one second.
*/

/*!
    \internal
    \class QDeclarativeFlipable
    \brief The Flipable item provides a surface that can be flipped.

    \ingroup group_widgets

    Flipable is an item that can be visibly "flipped" between its front and
    back sides.
*/

QDeclarativeFlipable::QDeclarativeFlipable(QDeclarativeItem *parent)
: QDeclarativeItem(*(new QDeclarativeFlipablePrivate), parent)
{
}

QDeclarativeFlipable::~QDeclarativeFlipable()
{
}

/*!
  \qmlproperty Item Flipable::front
  \qmlproperty Item Flipable::back

  The front and back sides of the flipable.
*/

QGraphicsObject *QDeclarativeFlipable::front()
{
    Q_D(const QDeclarativeFlipable);
    return d->front;
}

void QDeclarativeFlipable::setFront(QGraphicsObject *front)
{
    Q_D(QDeclarativeFlipable);
    if (d->front) {
        qmlInfo(this) << tr("front is a write-once property");
        return;
    }
    d->front = front;
    d->front->setParentItem(this);
    if (Back == d->current)
        d->front->setOpacity(0.);
}

QGraphicsObject *QDeclarativeFlipable::back()
{
    Q_D(const QDeclarativeFlipable);
    return d->back;
}

void QDeclarativeFlipable::setBack(QGraphicsObject *back)
{
    Q_D(QDeclarativeFlipable);
    if (d->back) {
        qmlInfo(this) << tr("back is a write-once property");
        return;
    }
    d->back = back;
    d->back->setParentItem(this);
    if (Front == d->current)
        d->back->setOpacity(0.);
}

/*!
  \qmlproperty enumeration Flipable::side

  The side of the Flippable currently visible. Possible values are \c
  Front and \c Back.
*/
QDeclarativeFlipable::Side QDeclarativeFlipable::side() const
{
    Q_D(const QDeclarativeFlipable);
    if (d->dirtySceneTransform)
        const_cast<QDeclarativeFlipablePrivate *>(d)->ensureSceneTransform();

    return d->current;
}

// determination on the currently visible side of the flipable
// has to be done on the complete scene transform to give
// correct results.
void QDeclarativeFlipablePrivate::updateSceneTransformFromParent()
{
    Q_Q(QDeclarativeFlipable);

    QDeclarativeItemPrivate::updateSceneTransformFromParent();
    QPointF p1(0, 0);
    QPointF p2(1, 0);
    QPointF p3(1, 1);

    p1 = sceneTransform.map(p1);
    p2 = sceneTransform.map(p2);
    p3 = sceneTransform.map(p3);

    qreal cross = (p1.x() - p2.x()) * (p3.y() - p2.y()) -
                  (p1.y() - p2.y()) * (p3.x() - p2.x());

    QDeclarativeFlipable::Side newSide;
    if (cross > 0) {
       newSide = QDeclarativeFlipable::Back;
    } else {
        newSide = QDeclarativeFlipable::Front;
    }

    if (newSide != current) {
        current = newSide;
        if (current == QDeclarativeFlipable::Back && back) {
            QTransform mat;
            QGraphicsItemPrivate *dBack = QGraphicsItemPrivate::get(back);
            mat.translate(dBack->width()/2,dBack->height()/2);
            if (dBack->width() && p1.x() >= p2.x())
                mat.rotate(180, Qt::YAxis);
            if (dBack->height() && p2.y() >= p3.y())
                mat.rotate(180, Qt::XAxis);
            mat.translate(-dBack->width()/2,-dBack->height()/2);
            back->setTransform(mat);
        }
        if (front)
            front->setOpacity((current==QDeclarativeFlipable::Front)?1.:0.);
        if (back)
            back->setOpacity((current==QDeclarativeFlipable::Back)?1.:0.);
        emit q->sideChanged();
    }
}

QT_END_NAMESPACE