QOpenGLWidget is much slower than QGLWidget when used as QGraphicsView viewport

    QGraphicsRectItem *ritem = new QGraphicsRectItem(0, 0, 200, 200);
    QPen pen(Qt::red);
    pen.setWidth(1);
    ritem->setPen(pen);
    gui.scene->addItem(ritem);
    gui.view->setSceneRect(ritem->boundingRect());

    QGLFormat fmt;
      fmt.setVersion(3, 2);
      fmt.setProfile(QGLFormat::CompatibilityProfile);
      gui.glwidget = new QGLWidget(fmt,this);
      gui.view->setViewport(gui.glwidget);

   gui.glwidget = new QOpenGLWidget(this);

   // Format is set on main()
     gui.view->setViewport(gui.glwidget);