Bug#450851: xserver-xorg-input-evdev: pointer constatntly moves down-right in captured state (most of games) when using evdev
I confirm this bug.
While using evdev, the mouse movement in full-screen games is VERY
sloppy, and constantly jumps to the lower-right corner.
The workaround "export SDL_VIDEO_X11_DGAMOUSE=0" did not work for Doom3,
but it did for Defcon and ScummVM
Maybe (just a stupid guess) two different facilities (evdev and
something else) are caring about the mouse pointer in competition.