qdeclarativeflipable.cpp

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#include "private/qdeclarativeflipable_p.h"

#include "private/qdeclarativeitem_p.h"
#include "private/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();
    void setBackTransform();

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

    bool wantBackXFlipped;
    bool wantBackYFlipped;
};

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

QDeclarativeFlipable::~QDeclarativeFlipable()
{
}

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.);
    emit frontChanged();
}

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.);
    connect(back, SIGNAL(widthChanged()),
            this, SLOT(retransformBack()));
    connect(back, SIGNAL(heightChanged()),
            this, SLOT(retransformBack()));
    emit backChanged();
}

void QDeclarativeFlipable::retransformBack()
{
    Q_D(QDeclarativeFlipable);
    if (d->current == QDeclarativeFlipable::Back && d->back)
        d->setBackTransform();
}

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);

    QPointF scenep1 = sceneTransform.map(p1);
    QPointF scenep2 = sceneTransform.map(p2);
    QPointF scenep3 = sceneTransform.map(p3);
    p1 = q->mapToParent(p1);
    p2 = q->mapToParent(p2);
    p3 = q->mapToParent(p3);

    qreal cross = (scenep1.x() - scenep2.x()) * (scenep3.y() - scenep2.y()) -
                  (scenep1.y() - scenep2.y()) * (scenep3.x() - scenep2.x());

    wantBackYFlipped = p1.x() >= p2.x();
    wantBackXFlipped = p2.y() >= p3.y();

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

    if (newSide != current) {
        current = newSide;
        if (current == QDeclarativeFlipable::Back && back)
            setBackTransform();
        if (front)
            front->setOpacity((current==QDeclarativeFlipable::Front)?qreal(1.):qreal(0.));
        if (back)
            back->setOpacity((current==QDeclarativeFlipable::Back)?qreal(1.):qreal(0.));
        emit q->sideChanged();
    }
}

/* Depends on the width/height of the back item, and so needs reevaulating
   if those change.
*/
void QDeclarativeFlipablePrivate::setBackTransform()
{
    QTransform mat;
    QGraphicsItemPrivate *dBack = QGraphicsItemPrivate::get(back);
    mat.translate(dBack->width()/2,dBack->height()/2);
    if (dBack->width() && wantBackYFlipped)
        mat.rotate(180, Qt::YAxis);
    if (dBack->height() && wantBackXFlipped)
        mat.rotate(180, Qt::XAxis);
    mat.translate(-dBack->width()/2,-dBack->height()/2);
    back->setTransform(mat);
}

QT_END_NAMESPACE