#include <QGraphicsView>
#include <QGraphicsPixmapItem>
#include <QApplication>

/*
 * Bug: when view has DontSavePainterState optimization and scene has some item for which setPos() is
 * called at some point, then QPainter which is passed to drawForeground() will have translated
 * origin. AND origin will be translated only if view gets large enough size.
 *
 * Try to resize view widget in this example to smaller size and you'll notice that the green
 * square which is drawn in drawForeground() will jump to 0,0 at which it should be.
 *
 * If you resize view back to larger size, you'll observe it jumping to the center of the view -
 * origin of QPainter is shifted.
 *
 * While QPainter passed to drawBackground() still has the right origin (see yellow rectangle which
 * is painted in drawBackground().
 */

class MyScene : public QGraphicsScene
{
public:
    MyScene() {}

    void drawBackground(QPainter *p, const QRectF&)
    {
        QPixmap pix(40,40);
        pix.fill(Qt::yellow);
        p->drawPixmap(0, 0, pix);
    }

    void drawForeground(QPainter *p, const QRectF&)
    {
        QPixmap pix(40,40);
        pix.fill(Qt::green);
        p->drawPixmap(0, 0, pix);
    }

    void initItems()
    {
        setSceneRect(0, 0, 500,500);
        QPixmap pix(20,20);
        pix.fill(Qt::red);
        QGraphicsPixmapItem* item = new QGraphicsPixmapItem(0, this);
        item->setPixmap(pix);

        // THIS line causes QPainter translation in drawForeground() when view gets BIG.
        // And has no effect on QPainter (as it really should) when view size is small

        item->setPos(250,250);
        item->show();
    }
};

int main(int argc, char **argv)
{
    QApplication a(argc,argv);
    MyScene* field = new MyScene();

    QGraphicsView* view = new QGraphicsView(field, 0);

    // Bug happens only when this optimization enabled (obviously)
    view->setOptimizationFlags( QGraphicsView::DontSavePainterState);

    view->show();
    view->resize(600,600);
    field->initItems();

    return a.exec();
}