KDE 4.1 with Multi-Head

Just a short note: If you plan to use KDE 4.1 with Multi-Head, make sure you do *not* do it using xrandr, otherwise KDE gets confused and messes up your screen. So set up your xorg.conf statically.

Intel put up a short howto, but it shouldn't be that different for other drivers. The important part goes like this:

Section "Device"
Identifier "Configured Video Device"
Driver "intel"
Option "FramebufferCompression" "off" # on for battery, off for multi-display
Option "monitor-LVDS" "internal"
Option "monitor-VGA" "external"
EndSection

Section "Monitor"
Identifier "internal"
EndSection

Section "Monitor"
Identifier "external"
Option "RightOf" "internal" #the left display is the primary one
EndSection

Section "Screen"
Identifier "Default Screen"
Monitor "internal"
Device "Configured Video Device"
SubSection "Display"
Virtual 2560 1024
# this should be as large as both displays next to each other
EndSubSection
EndSection

Section "ServerFlags"
# Option "Xinerama" "true" # crashes
Option "AIGLX" "false" # crashes multi-head
EndSection

After doing that, (instead of crashes and frustration) you're rewarded with very nice customization options in KDE 4.1.2: You can set the wallpaper for each screen, put different plasma applets at different locations, etc.

If you're using the intel driver I can also recommend disabling AIGLX in the ServerFlags Section of your xorg.conf to make the setup more stable. After supend/resume I regularly have to set reconfigure the screen setup with xrandr and then switch back and forth between X and the console to turn my external monitor back on.

I wonder how the new X server version in Kubuntu 8.10 will be.