@mrjj Thank you sir for helping me and direction. I am able to solve this issue by setting the clipping area properly on graph. Use QWidget::update() instead of QWidget::repaint().

Ahh I see. I'll check it out! Thanks for the suggestion. If you have any other ideas please let me know.

Hi @sol_aries Just read about QMouseEvent

@Ramin Actually I have never seen such a library. What I have done in the past (3 years ago) was to draw some elements connected to each other using Qt Quick (QML) and it worked pretty good. Another option is to look at the new modelling plugin that will be part of Qt Creator 3.6. And since Qt Creator is open source, you can look at how it is done and perhaps use that as a starting point.

@alex_malyu Thank you very much alex. I just tried what you suggested and it works perfectly. @SGaist I thought about slots and timer too, as suggested in the examples on qt's site, but it requires subclassing a QGraphicsItem for each item in the QGraphicsView. The problem is, I don't know the number of items that will be generated until runtime, and apart from this, creating 10.000 classes (one for each item) would be very resource intensive, I think. Anyway, the method above, the one with QCoreApplication::processEvents () ; works perfectly for my purpose. So thanks both for your politeness: it is very nice to see such a great community :)

@vishnu The control will go ahead if and only if both properties are initialized. Its a normal & operation.

Hi @Pheelbert, Make use of QQuickWindow::beforeRendering signal to draw the OpenGL stuff beneath QML scene. Have a look at this flow for more info, especially Pt. no. 8 and the example suggested by @SGaist.

@Chris-Kawa Sorry that was my problem didn't have seen the comment^^ Thank you :)