Thursday, January 29, 2009

KDE 4.2 with Dual Monitor

I just upgraded to KDE4.2 today on Kubuntu Interpid. One of the first items I am testing is the ability to use the display on my laptop and the monitor/projector at the same time. This is known as multihead and previously the Xinerama was used to have two different screens with one X server (the engine behind the graphics display on Linux).

The KDE 4.2 Plasma control (top right corner of the screen) Zoom Out function allowed the laptop screen to have a different background and widget from the monitor/projector. This really made an impressive environment for customisation.

This is great for presentation as the 3 have full capability to show the slides on one screen while previewing on another screen. The KDE4.2 provided the variable KDE_MULTIHEAD=false that allowed the same display for both the displays. Initially I changed this environment variable to true, but nothing happened.

The Intel site gave some good tips to get what I was looking for. The steps below allowed the multihead function to work when the VGA cable is plugged at the Login screen. To revert back to the dual head (where both laptop and monitor/projector displayed the same output), return to the Login screen and unplug the VGA cable. The X server should be restarted.

Step 1: Backup the /etc/X11/xorg.conf

Step 2: Replace the xorg.conf with the following

Section "Device"
Identifier "Configured Video Device"
Driver "intel"
Option "FramebufferCompression" "off"
Option "monitor-LVDS" "internal"
Option "monitor-VGA" "external"

Section "Monitor"
Identifier "internal"

Section "Monitor"
Identifier "external"
Option "RightOf" "internal"

Section "Screen"
Identifier "Default Screen"
Monitor "internal"
Device "Configured Video Device"
SubSection "Display"
Virtual 2560 1024

Section "ServerFlags"
Option "AIGLX" "false"

Step 3: Reset the X server
Logout and restart the X by pressing Alt+e
Login again and you should have the new setting applied.

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