problem with QPixmap in setCacheMode

hi friends,
im trying to add thousands of pixmap items in the QGraphicsView so i tried to use cache method for the pixmap Item

Code:

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Qpixmap pxm;
setCacheMode(QGraphicsItem::ItemCoordinateCache,QSize(pxm.width(),pxm.height()));

---

im adding the pixmap item in QGraphicsLinearlayout


my problem is when i set to use the viewport as opengl the pixmaps are rendered properly ..but if i remove the opengl viewport property it is not showing the pixmaps and only borders are visible with partial pixmap display .
:(
Please help me .. thx in advance ..
Note: same thing happens for QGraphicsProxyWidget with QLabel with that pixmap ..