Can't get dual screen to work

Marius Gedminas marius at
Mon May 26 11:29:06 UTC 2008

On Mon, May 26, 2008 at 10:47:26AM +0200, pieter557 wrote:
> I'm having a problem with my dual screen setup ( not as easy as in windows
> ).
> I'm trying to have an extended desktop (just like in windows )
> That's the only thing i really miss in ubuntu.
> I have an  Intel Corporation Mobile GM965/GL960 Integrated Graphics
> Controller.
> My laptop is a fujitsu lifebook s6410 and my second display is a samsung
> 2032mw.
> The screen resolution program only gives me a max resolution of 1280*1024
> while i should be able to do 1680x1050.
> My laptop screen does 1280*800.

You are hitting a limitation (read: bug, more specifically in the current video driver
architecture that doesn't allow you to extend the desktop beyond the
initial size.  There's a workaround: edit the /etc/X11/xorg.conf file as
root, find the Screen section, and add

        SubSection "Display"
                Virtual         2048 2048

inside (replace 2048x2048 with whatever *maximum* size of the extended
desktop you want).  Then reboot (or press Ctrl+Alt+Backspace to restart
the X server) and you'll be able to use the Screen Resolution applet to
get the extended desktop you want.

There are two caveats: if you use 3D effects (aka Compiz), and switch
between one display and extended desktop, sometimes part of the screen
stops updating and you have to restart Compiz to unblock it.  (Alt+F2,
type "compiz --replace", press Enter).  It's this bug: (window list in the panel stops
updating) is somewhat related, and fixed with the same workaround.

The other caveat is that if the total size of your desktop exceeds 2048
pixels in any direction, you won't be able to use desktop 3D effects
(part of the desktop beyond the 2048x2048 area will not be drawn).  It's
this bug:

and the workaround is a little bit more complicated (patching and
recompiling Mesa and the intel video driver).

Marius Gedminas
The typewriter was invented by Hungarian immigrant Qwert Yuiop, who left his
"signature" on the keyboard.
        -- "Kim"
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