Xorg and purposefully odd monitor geometry
 

I'm working on building an LCD projector. I have 15" Fresnel lenses, which would ideally be pushing light through a 15" monitor. However, I have a spare 17" monitor here, and would like to be able to use that (save some money).

So heres my question:
Is it possible to tell Xorg (and KDE/WMs/etc) to use a selective portion of the screen? The monitor supports 1024x768, is there a way to say "work in 800x600, over this area here..." Where it would go over either the middle of the screen... or along two edges? I've seen laptops that do it, when they don't actually adjust screen resolution, just use fewer pixels.

Anyone have any ideas/pointers?

You could dive into the X configuration, something like reducing the visible area on your screen. Google for "xfree86 timing modeline calculate" (without quotes)

or...

you could run a vncserver on your box in 800x600, and open a vncviewer on another desktop of the same computer. There you have 800x600 and you even can move it around :)

jlinkels