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

[René J.V. Bertin]

On Monday May 21 2018 09:37:32 Clemens Eisserer wrote:

Hi,

>Kwin is already set to OpenGL compositing - however window content
>painting and compositing are two separate steps.

Window content and window decoration are things under control of 2 different applications, either can do compositing or not. I am however under the impression that KWin (v5.x) somehow influences the way window content is drawn. Depending on its settings fullscreen video could become unwatchable for instance. I've stopped using KWin for that reason - and I have ony a 1366x768 screen on a "Cherryview" GPU (sounds opposite but in terms of pixel-pushing power it is maybe comparable).

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

To my knowledge there is no such thing; Qt5 uses OpenGL underneath. You may discover options when you follow the path through which the functions you mentioned are called, but you should probably ask this question on the Plasma and/or Qt mailing lists.

BTW, what kind of drawing operations are affected? Qt4 had several internal animation/effect settings that could be controlled through qtconfig. I never looked if Qt5 has something similar, but those are probably largely handled through the widget style. If you haven't yet, assess your issue using different widget styles (easiest via the -style option launching the application from a commandline) and widget style settings (probably accessible through the Style KCM).

R.