Artifacts with QGraphicsDropShadowEffect on a QGraphicsItem with children.

        QGraphicsScene* gs = new QGraphicsScene();
	QGraphicsView* gv = new QGraphicsView(gs, 0);
	QGraphicsRectItem* ri = new QGraphicsRectItem(0, 0, 200, 100, 0, gs);
	ri->setFlag(QGraphicsItem::ItemIsMovable);
	QGraphicsDropShadowEffect* shadow = new QGraphicsDropShadowEffect();
	ri->setGraphicsEffect(shadow);
	QGraphicsEllipseItem* ei = new QGraphicsEllipseItem(QRectF(-10, -10, 20, 20), ri);
	gv->resize(640, 480);
	gv->show();