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KWin render backend and window content


Does anyone on this list know answers to the following?

The "tearing prevention" option in KWin's Compositor setting has a large effect on video playback on my system. The only way I seem to be able to avoid tears and partial screen updates are

OpenGL + fullscreen repaints tearing prevention
XRender (+ Automatic tearing prevention)

I presume that "fullscreen repaints" corresponds to the good approach where you update an offscreen framebuffer and then swap that with the onscreen buffer just before the screen starts to repaint. Normally you shouldn't notice that screen refresh rates of 60Hz or better but with KWin there are some artefacts.

I've now gone back to using the XRender backend but I do wonder if that means OpenGL isn't being used for anything anymore unless the application asks for it explicitly?