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Keyboard layout in a X-desktop
'setxkbmap' allows to set multiple keyboard layout together with a switching mechanism. The Archlinux-wiki Write provides excellent information about this subject.
For example, making the US-American and the Swiss keyboard layout available and having Alt+Caps switch between them, the following is written into '~/.X.d/setxkbmap'.
setxkbmap us,ch -option grp:alt_caps_toggle
Alternative approach
The same can be achieved by use of an Xorg-configuration file as described in a forum entry.