Switching between virtual desktops

[Quinn Harris]

Luca,

X windows systems have a display for each desktop environment (KDE, Gnome).  
All X windows applications look for a display server usually specified by the 
DISPLAY environment variable then connect to that server via local mechanism 
or a network socket.  Go to a terminal and type "echo $DISPLAY" you will 
probably get ":0.0" that number specifies what local display to use.  If your 
system is setup for multiple simultaneous X logins (newer distros) each login 
will have a different xserver and display, the environment variable is how 
processes launched in each environment know what xserver to connect to.  Only 
one xserver process can use a video card at one time, though they can hand off 
control from one server to another and the text console typically using the 
Ctrl+Alt+Fx keys.  Until the recent xrandr 1.2 implementation, if an xserver 
was setup to use two monitors it would create two displays one for each 
monitor unless the Xinerama option was on.  In this case a different desktop 
environment could be run on each display with a common keyboard and mouse 
which I think is what you are asking.

If you have two separate video cards, it is possible (though there can be 
issues) to run a different xserver instance for each card with an independent 
mouse and keyboard.  So one computer with two sets of video, keyboard and 
mouse could act like two different computers.  This can also be done with one 
dual headed video card using Xephyr, but lacks some features (3D) and will be 
a little slower.  Check out
http://www.x.org/wiki/Development/Documentation/Multiseat

Why do you need to switch between virtual desktops rapidly from a script?  Are 
you sure this is the right solution to your problem?


Quinn