qt5 showFullScreen

I launch a qt app directly from startx customizing .xinitrc with something like this:

exec /path/to/myqtapp

I want to display this app fullscreen so inside the app I use showFullScreen() method.

This works perfectly using qt 4.8.x but fails qt 5.x: the app is not fullscreen

After observing the issue in my custom qt 5.7.0 compilation I tryed the offline installer for versions 5.6.1.1 and 5.7.0 and they give the same result.

If I run the same app inside gnome showFullScreen works as expected,

so seems I have to stay on qt4 for now

please fix this regression

thanks!