Qt GraphicsView stop getting paint event

[karankumar1609]

Hello,

I am working with QGraphicsView and QGraphicsScene for drawing of QPixmap data on QGraphicsItem.
What i am doing is start a QTimer on each timeout of QTimer i draw data on QPixmap via QtConcurrent.

QtConcurrent::run(this, &LinePlotter::plotDataOnImage);

QtConcurrent::run(this, &LinePlotter::plotDataOnImage);

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On plotDataOnImage i call update() after drawing on QPixmap.
It works fine but unfortunatly my QGraphicsView and QGraphicsScene stop getting paint events.
but when i click on window it repaint again but it does not repaint on call of update() method.

customizations for QGraphicsView i have made are:

setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
 
    setRenderHints(QPainter::HighQualityAntialiasing | QPainter::SmoothPixmapTransform | QPainter::TextAntialiasing);
 
    setViewportUpdateMode(QGraphicsView::SmartViewportUpdate);
 
    setCacheMode(QGraphicsView::CacheNone);
 
    setOptimizationFlags(QGraphicsView::DontAdjustForAntialiasing
                         | QGraphicsView::DontClipPainter
                         | QGraphicsView::IndirectPainting);

setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);

    setRenderHints(QPainter::HighQualityAntialiasing | QPainter::SmoothPixmapTransform | QPainter::TextAntialiasing);

    setViewportUpdateMode(QGraphicsView::SmartViewportUpdate);

    setCacheMode(QGraphicsView::CacheNone);

    setOptimizationFlags(QGraphicsView::DontAdjustForAntialiasing
                         | QGraphicsView::DontClipPainter
                         | QGraphicsView::IndirectPainting);

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I have never got this kind of problem before but i dont know why my view not get its paint event properly.
any idea about the problem?


-----------------------------------------------
There is something i have seen i just start my application and keep it opened without any mouse interaction or any other kind of interactions.
Then i start my stop watch and checks the log.

It also got stop painting(stop getting events) when keeping in background (rarely occured)...
What is the issue?
I am using Cent OS 6.4
Qt 5.0

Please tell me what is the issue?