Comment 99 for bug 295192

...
> 1. Have only a single monitor enabled.
> 2. Open firefox
> 3. Enable the secondary monitor.
> 4. Move the firefox window to the secondary monitor.
> 5. Open menus/tooltips/etc. They will show up on the primary monitor.

2+ more multi-monitor related long standing "gnome disagrees
with the x11 driver about the monitor order" bugs:

* Have only a single (the internal LVDS notebook) monitor enabled.
* Have a drawer placed on the gnome panel.

* Plug the second monitor, everything looks sane so far:

#xrandr
Screen 0: minimum 320 x 200, current 1280 x 800, maximum 2960 x 1850
VGA connected (normal left inverted right x axis y axis)
   1680x1050 59.9 + 60.0
...
LVDS connected 1280x800+0+0 (normal left inverted right x axis y axis)
331mm x 207mm
   1280x800 60.0*+
...

* Enable the secondary monitor
(e.g. xrandr --output VGA --right-of LVDS --mode 1680x1050).

[1] Both top and bottom gnome panels perform an immediately
jump to the external secondary monitor.

* Don't let it get you down, unlock and drag the panels back to the
primary monitor.

* Click on the drawer on primary monitor.

[2] The the drawer content pops up on secondary monitor.

[+] Almost every splash-window appears horizontal in the middle between
both monitors.

[+] Most OpenGL games smashes a 2 monitor geometry setting so badly,
that the only option left is restart the x11 server.