[randr 1.2] change mode before start gnome-session make desktop corruption

[Liu, Xinyun]

Hi,

run Xorg and use xrandr to change mode, then run gnome-session and set desktop
from mirror mode to extended desktop mode, the deskop is corrupted. It can be
reproduced both on ati/intel cards. I guess it's randr module bug and maybe have
same root cause as #4707 said. this bug is reported as
https://bugs.freedesktop.org/show_bug.cgi?id=12028.

Note: if you run gnome-session before change one monitor to a new mode, this bug
can't be produced.

Following is the step to reproduce the bug on IBM x60 (GMA950):

1. build X, intel driver, xrandr from git. (2008/8/16)
2. run X
  the log is:
  ...
(II) intel(0): EDID vendor "SAM", prod id 439
(II) intel(0): EDID vendor "LEN", prod id 16384
(II) intel(0): Output VGA connected
(II) intel(0): Output LVDS connected
(II) intel(0): Output TV disconnected
(II) intel(0): Output VGA using initial mode 800x600
(II) intel(0): Output LVDS using initial mode 1024x768
(II) intel(0): Monitoring connected displays enable
 ...
3. set a new mode on CRT connector.
   xrandr --output CRT --mode "640x480"
4. run gnome-session
   gnome-session &
5. change to extended desktop
   xrandr --output CRT --left-of LVDS
6. bug occurs
   open a xterm window and drag it.

can you have a look at it?

-- 
Best Regards,
Liu, Xinyun