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Old 08-10-2008, 01:51 PM   #1
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Registered: Oct 2005
Location: UK
Distribution: Slackware
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How to enable extended desktop on second monitor?

I've just bought a new monitor, whose maximum resolution is 1440x900. If I plug it in to my ThinkPad T40's dock and boot, X picks it up and applies the correct resolution. However, the image is a duplicate of the image on the laptop's screen. I've managed to set all the panels to fit the external monitor, so it all looks OK, except if I maximise a window, it maximises to 1024x768 (the laptop's resolution), not to 1440x900 (the external monitor resolution).

I've been googling, and people mention xrandr a lot with respect to configuring dual screen. So I tried all the relevant commands posted on the ThinkWiki article, for example, but I can't get an extended desktop, that is where I can scroll from the edge of one monitor into the appropriate edge of the next.

I'm aware of Xinerama, whose job it is to do this sort of thing, but according to wikipedia (source of all knowledge! ) the project is being phased out in favour of xrandr. However, I can't find anything on google about how to configure an extended desktop.

Does anyone have any experience with Xinerama? Is that even the appropriate tool? Or can this be done with xrandr?


Mods: I was torn between the Hardware and Software forums, but the monitor works, so the problem is software based, as far as I can determine.
Old 08-10-2008, 02:16 PM   #2
Registered: Aug 2006
Location: London
Distribution: Debian, Kubuntu
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What desktop environment are you using? I have this setup in KDE 3.5 - all configured through KDE control centre -> 'Monitor & Display' -> tick 'Second screen' -> select 'Dual Screen'. Admittedly on Kubuntu I had resolution issues with this - at first it was defaulting to a very low resolution on one of the monitors. At the same time on my work laptop (SUSE) I didn't have any issues whatsoever.
Old 08-10-2008, 05:47 PM   #3
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I got it working in the end by adding

Virtual 2464 900

to my xorg.conf Screen section. Then using the following xrandr commands:
xrandr -q # to identify the screen names (LVDS for the laptop screen and VGA-0 for the external monitor)
xrandr --output VGA-0 --pos 1024x0 # to move the VGA screen 1024 pixels to the right.
This page was the most useful in the end:

Last edited by pwc101; 08-11-2008 at 03:32 AM. Reason: corrected syntax on second xrandr command
Old 12-16-2016, 05:44 AM   #4
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Registered: Dec 2016
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thx pwc101,

I just did :
xrandr --output DVI-I-1 --pos 1920x1080
Then I had 2 screen not displaying the same image but it was impossible to move the mouse cursor to the second screen.
I re-opened Display configuration and I recovered the possibility to set the disposition.


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