QOpenGLContext window flickers on resize

[Row_Rebel]

Here is a screenshot of the white flickering i'm experiencing while resizing : http://oi63.tinypic.com/11wgi9t.jpg

The code i'm using is exactly the one in this example (apart from few errors):
https://wiki.qt.io/Using-QOpenGLFunctions-and-QOpenGLContext

Since i'm pretty new to the qt-openGL interaction i'm kinda lost and can't figure out where the problem might originate.

I'm not sure which version of qt I downloaded (neither if it really makes any difference) and I read there's a difference between the one which automatically uses openES and the other using opengl desktop, could this be the problem?