Scrolling QGraphicsView and QGraphicsScene

[freely]

Hi,

I have QGraphicsScene instance set to QGraphicsView on the GUI with scrollbars enabled and full view port update. But when I scroll my graphics view I get the items added to qgraphics scene disappeared on some point,

though they are added in code correctly and are expected to be displayed upon scroll ( custom class inherited from QGraphicsItem ):

class CSquare : public QObject, public QGraphicsItem

class CSquare : public QObject, public QGraphicsItem

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One can see how they disappear on application run on this video screen cast:

https://www.box.com/s/h4h94×1avgay1crzvyzx

Can somebody hint what is the problem, how to resolve so the graphics items will not disappear on the view?

Thanks in advance.