Comment 5 for bug 277948

I also have this problem.

Whatever underlying problem there has various misbehaviors as results. Here is just one example.

I just tried to set the desktop image to a 3080x1050 image which exactly fits my dual-monitor screen area (LVDS 1400x1050 and DVI-0 1680x1050). The image would not display correctly using any of the "Style" settings on "Appearance Preferences | Background | Wallpaper". Then I used "System | Screen Resolution" to move the DVI to the left of LVDS; then back to the right, restoring the original situation. Then with "Style" set to "Fill screen" the desktop background displayed correctly.

This suggests to me that nautilus's understanding of the screen dimensions is not correctly synced with X's understanding of the screen dimensions.

Another example: Sometimes after logging in the desktop comes up on both monitors but I cannot move the mouse outside the LVDS. Grabbing the title bar I can move about 90% of a window onto the DVI-0 monitor.

Another bug which may or may not be related: The window list applet in the LVDS doesn't show windows on the DVI-0 unless "Window List Content" is set to "Show windows from all workspaces".

$ xrandr
Screen 0: minimum 320 x 200, current 1400 x 1050, maximum 3080 x 1050
VGA-0 disconnected (normal left inverted right x axis y axis)
DVI-0 connected 1680x1050+1400+0 (normal left inverted right x axis y axis) 474mm x 296mm
   1680x1050 59.9*+
   1600x1024 60.2
   1400x1050 60.0
[...]
LVDS connected 1400x1050+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1400x1050 50.0*+
S-video disconnected (normal left inverted right x axis y axis)

$ cat /etc/X11/xorg.conf
# xorg.conf (X.Org X Window System server configuration file)
[...]
Section "Monitor"
 Identifier "Configured Monitor"
EndSection
Section "Screen"
 Identifier "Default Screen"
 Monitor "Configured Monitor"
 Device "Configured Video Device"
 Defaultdepth 16
 SubSection "Display"
  Depth 16
  Virtual 3080 1050
 EndSubSection
EndSection
Section "Device"
 Identifier "Configured Video Device"
EndSection

$ lspci -v -s 01:00.0
01:00.0 VGA compatible controller: ATI Technologies Inc Radeon Mobility M7 LW [Radeon Mobility 7500]
 Subsystem: IBM Device 0517
 Flags: bus master, stepping, fast Back2Back, 66MHz, medium devsel, latency 66, IRQ 11
 Memory at e8000000 (32-bit, prefetchable) [size=128M]
 I/O ports at 3000 [size=256]
 Memory at d0100000 (32-bit, non-prefetchable) [size=64K]
 [virtual] Expansion ROM at d0120000 [disabled] [size=128K]
 Capabilities: <access denied>
 Kernel modules: radeonfb