#include <QtGui/QApplication>

#include <QtWidgets/QGraphicsView>
#include <QtGui/QGraphicsScene>
#include <QtGui/QGraphicsObject>
#include <QtGui/QDrag>
#include <QtCore/QMimeData>
#include <QtGui/QGraphicsSceneMouseEvent>
#include <QtGui/QImage>
#include <QtGui/QPixmap>

class DragTestObject : public QGraphicsObject
{
public:
    DragTestObject(int position)
    {
        setX(10);
        setY(110 * position);
    }

    virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
    {
        painter->fillRect(0, 0, 100, 100, QBrush(Qt::black));
    }

    virtual QRectF boundingRect() const
    {
        return QRectF(0, 0, 100, 100);
    }

protected:
    virtual void mousePressEvent(QGraphicsSceneMouseEvent *event)
    {
        event->accept();

        if(event->buttons() == Qt::LeftButton)
        {// buttons confirms that left button is the only button pressed
            setCursor(Qt::ClosedHandCursor);
        }
    }

    virtual void mouseMoveEvent(QGraphicsSceneMouseEvent *event)
    {
        if(event->buttons() == Qt::LeftButton)
        {
            int dist = QLineF(event->screenPos(), event->buttonDownScreenPos(Qt::LeftButton)).length();
            if(dist >= QApplication::startDragDistance())
            {
                performDrag();
            }
        }
    }

private:
    void performDrag()
    {
        QMimeData *mimeData = new QMimeData();// deleted by Qt after the drag exec

        QDrag *drag = new QDrag(this);//deleted by Qt after exec
        drag->setMimeData(mimeData);

        QImage image(40, 40, QImage::Format_RGB32);
        image.fill(Qt::blue);

        drag->setPixmap(QPixmap::fromImage(image));
        drag->exec();
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QGraphicsView view;

    QGraphicsScene scene;

    view.setScene(&scene);

    for(int i = 0; i < 10; ++i)
    {
        scene.addItem(new DragTestObject(i));
    }

    view.fitInView(0, 0, 150, 150, Qt::KeepAspectRatio);

    view.show();

    return a.exec();
}