Configuring X for two possible screens

["Moore, Paul" <Paul.Moore@uk.origin-it.com>]

Hi,
I have a laptop which I can run either using the internal 800x600 screen, or
an external monitor which will run at 1024x768. I'd like to be able to set
up the system so that I can start X to run on whichever is connected (eg, I
could have aliases startx-internal and startx-monitor).

I can set up an XF86Config file which includes monitor definitions for both
monitors. The vide card is the same in both cases. What I don't know, and
can't find in the online docs, is how to run startx to tell it which monitor
is currently plugged in... I guess I may need to add more stuff to my
XF86Config - I just don't know what!

Any hints, pointers to relevant documentation or preferably complete
solutions (:-)) gratefully accepted.
Paul.