QMdiArea: Maximaized SubWindow in background?

[JohnnyRep]

Ah perfect! Thanks wysota!
It seems to work fine when I used a QTreeWidget (just for testing), but the QGLWidget gets reduced to 50x100pixel.
I would have thought that the viewport-widget always takes the maximum space available (= the full QMdiArea). setMinimumSize() etc. did not work!
Do you know, if I have to set a QSize somewhere to resize the GLWidget?

[wysota]

The viewport occupies the whole visible area of the scroll area (apart the scrollbars). Maybe it's not the GL widget that is so small but rather you don't initialize the projection matrix of the GL widget properly?

[JohnnyRep]

I must have done something wrong. When I am using the QGLWidget as a QMdiArea Subwindows it works fine (it always has the full size of the subwindow and I can resize and maximize it).
By adding a QMenu to my QGLWidget and set it as viewport it seems that just the QMenu is drawn. Is there any difference between a widget used in a subwindow and one used as a viewport? For me it looks like the QGLWidget does not take its space by the default when it is set as a viewport, when I am using a different Widget, such as the QTableWidget it'll take as much space as needed.