QGLWidget maximum size

Question

I have a Qt application using OpenGL drawing with QGLWidget, on Mac OS. On my MBP it works well, but when trying on a 30" screen, I noticed that there is a window size limit.
If I increase the window size beyond a certain limit, the QGLWidget's content disappears and only some greyish memory junk is visible.

I changed the code to only put a QGLWidget on the screen. The repaint event is setting the background black in each iteration.
The issue is still visible: when resizing the widget, the black surface disappears and gets replaced by the memory junk, when the size of the widget reaches a certain size.

Interesting facts:

• When I decrease the window size, the GL surface comes back to live again
• I have several other GL applications (not Qt) running in maximized window, so the issue is not with the OpenGL driver/video card
• It seems that the area of the window (nr of pixels) matters, if I make the window very wide, it's height will be limited and vica versa, I if the windoe is maximized in height, the width must be small

Answer 1

I found that while instantiating the QGLWidget using QGLFormat(QGL::NoSampleBuffers) instead of QGLFormat(QGL::SampleBuffers) solves the issue.