How to use the "opengl" qt rendering backend instead of "raster"?

[Clemens Eisserer]

Hi Rene,

> No wonder they have no effect if you use a KDE5/Plasma5 desktop nowadays. Do you? In that case, have you tinkered with the various options of the kwincompositing KCM?

Kwin is already set to OpenGL compositing - however window content
painting and compositing are two separate steps.
So while I am happy with kwin's compositor performance, I am rather
dissatisfied with the performance the window content itself is drawn.

Is there any option to instruct QT5 to use the OpenGL graphics backend?

Best regards, Clemens