Qt5 on Ubuntu 14.10 : screen becomes full black when showing a QWidget

[P.Petitprez]

Hello,

I'm fairly new to Qt (less than 6 months using it) and also new to Linux programming. I'm stuck with a problem when porting our software running on Qt 4 to Qt 5. While eveything runs fine with Qt4, the version running on Qt5 has a strange behaviour: everytime I try launching the software, my monitor becomes fully black but there is no crash/freeze : the app runs and even the keyboard works (shortcut key to shutdown the app works and I get back the desktop).
Also, the Qt5 version shows randomly some errors like "Xlib: extension "NV-GLX" missing on display ":0.0"." while Qt4 version shows nothing.

Does somebody know how to solve this ?

Notes:

• using Ubuntu 14.10, everything up to date.

• using Qt 5 from the package repository (no custom compilation from the Qt5 sources due to the policy of our project)

• the exact same code / compilation / run tests on a Linux Mint work perfectly.

• I cannot test on other Ubuntu computer for the moment but I will do it as soon as I can.

Thanks in advance.