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Old 12-14-2012, 01:39 PM   #1
LQ Newbie
Registered: Nov 2012
Posts: 15

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xcompmgr error in Xmonad: No Composite Extension

I have been having a problem with xcompmgr since I moved from Debian 5 to Debian 6. While in Xmonad, if I try to run
xcompmgr -cf
I get the error
No composite extension
xcompmgr runs perfectly while I am running a gnome session - but it does not seem to want to run in a Xmonad Session.

I did not need this for gnome, but I have added the following to /etc/xorg.conf:
Section "Extensions" 
        Option "Composite" "True" 
        Option "RENDER" "True"
I have read that some people have had success with Nvidia cards by adding:
Option "RenderAccel" "on"

but I am using an ATI card - and this seems to be a feature that is particular to Nvidia.
If it matters, I run xcompmgr in my ~/.xsessionrc with the following line:
xcompmgr -cf &
and it definitely is not running in the background since
ps -A | grep xcomp
returns nothing.

I was hoping that someone may have had a similar problem or had some suggestions. Thanks again,

Old 12-14-2012, 01:51 PM   #2
LQ Newbie
Registered: Nov 2012
Posts: 15

Original Poster
Rep: Reputation: Disabled
It seems like the issue is xinerama. Apparently xinerama and xcompmgr do not like playing together...

I don't suppose anyone knows how gnome manages to do this?

Last edited by kaivai; 12-14-2012 at 02:02 PM.
Old 12-14-2012, 04:09 PM   #3
LQ Newbie
Registered: Nov 2012
Posts: 15

Original Poster
Rep: Reputation: Disabled
Nope - I was wrong. I could have sworn it was working in gnome, but xinerama and xcompmgr are incompatible.

I have however read that using the Catalyst drivers instead of the fglrx drivers enable you to do an eyefinity setup, which allows you to use a compositing tool. I need to finish the rest of my 'safe' installation before I break it again - but I'll post again if I can get it running and it works.
Old 12-20-2012, 09:14 AM   #4
LQ Newbie
Registered: Nov 2012
Posts: 15

Original Poster
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Horay! The solution was indeed to use XRANDR. This is how I went about using XRANDR with the FGLRX drivers installed. As a complete side note, this solved my flickering conky as well.

1. use:
sudo amdcccle
to disable xinerama, and disable all but one monitor

2. open /etc/X11/xorg.conf, in the DISPLAY subsection of SCREEN add the heading Virtual; Set the resolution to be the total possible Width and Height of all monitors combined
(I am using 2 1920x1080 monitors)
ex: Virtual 3840 2160

3. restart X or restart

xrandr -q
to list all available displays
xrandr --auto to activate second display
xrandr --output (DisplayName-seen-with xrandr -q) --left-of (Other-DisplayName-seen with xrandr -q)

Play with this until you know which monitor is on which side. Horay! It works for now - until you logout or restart.

Making the changes permanent:

1. open /etc/X11/xorg.conf

2. look for the monitor sections with the names detected by xrandr -q (I had 4 monitors listed - but fglrx only manages 2 of them. I think the ATI driver interacts with a virtual monitor which sends the changes to your actual monitor, but I could be wrong)

Under that heading you are going to add a modeline, and a preferred Mode for your resolution

3. generate a modeline for each "Monitor" section with
cvt width height
. this is the resolution you want per monitor, not combined. ex:
cvt 1920 1080
The second line returned is your modeline
Paste your modeline under each monitor with a name you recognize from xrandr -q

Under your modeline add:
Option "PreferredMode" and then the first section of your modeline that is in quotations
ex: Option "PreferredMode" "1920x1080_60.00"

4. Since this is a multi-display you need to make sure that the monitors are not disabled, and that their position is correct

Check to see if there is a Option "Disable" "True" listed, and if so change it to "false"
For the monitor that you want on the right hand side, set:
Option "Position" "width-of-first-display 0"
ex: Option "Position" "1920 0"

That's it! Restart X (or restart your machine) to see if it worked!


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