https://bugs.freedesktop.org/show_bug.cgi?id=56405
--- Comment #38 from Michael Dressel mdrslmr@t-online.de --- The distorted graphics problem disappears when setting the option Option "NoAccel" "on". (This may be obvious to the experts.)
In this mode a new phenomenon appears: When moving th mouse to the Activities corner and the "summarizing display" is shown, the background consists of a corrupted image.