Comment 84 for bug 296167

some further information for yall:

setup:
2 x nvidia 8600gts vid cards
3 x screens, all separate X screens, merged with xinerama
Arranged as GPU0S0 - GPU1S0 - GPU1S1
ubuntu 8.10, gnome, metacity

I've setup a xev process in the same location on each screen (so 3 xev instances), when i trigger the bug using the GPU0S0/GPU1S0 boundary moving the mouse in the xev session on screen GPU0S0(left) triggers events in the xev process running on screen GPU1S0(middle). moving the mouse within xev processes on the other 2 screens (middle and right) causes no events to be registered anywhere.

The frequency of the bug's occurrence is definitely tied to system / graphical load. With nvidia cards a few firefox windows (or anything with heavy xrender use) and/or a few open windowed opengl apps and the bug happens about 50% of the time when changing screens and happens much more frequently when moving over the boundary between GPU's than it does moving over the boundary between x sessions that are running on the same GPU.

To "reset" the bug without rebooting the x server you can do the following:

alt-tab to a window (firefox is the one i usually use)
alt-space to bring up the window options menu (metacity)
select move (this binds the cursor to the center of the window)
use the arrow keys to move the window to another X session window
move the mouse
the bug should now be gone

i'm happy to run some other tests if theres anything that would be useful

cheers,

x