I would like to make the visible workspace of my desktop fill up less space than the entire monitor while keeping image fidelity constant. Presumably, any solution would leave a black border around the new, smaller main window. I am pretty sure this involves making some tweaks to xorg.conf (like changing the DisplaySize and X and Y position of the root window or something), but nothing has worked for me. I am running Debian "Squeeze".
Launch a second X server, using XNest, and position it within the real root window. This has several advantages over messing with xorg.conf files:
you can still put extra stuff in the black border (or not make it black, etc.) (might be cool remove the frame and see "joejoejoe wuz here" down the side)
you can position it exactly where you want just using mouse (XNest is an X server that looks like a client to the root X Server)
and uh, you don't have to futz with xorg.conf files
Look into the Xrandr man page xrandr. If I am reading into your question correctly, I have achieved this on a few occasions by messing different options (see below). It can be done per-session, without having to change xorg.conf
From the man page:
If invoked without any option, it will dump the state of the outputs, showing the existing modes for each of them, with a '+' after the pre- ferred mode and a '*' after the current mode.
After you list all outputs and available modes, and depending on what modes your Video Display supports, you can run the following for example. The man page lists other examples and features such as panning, rotating, hsync &c.
# xrandr --output VGA --newmode 800x600
xrandr -s 800x600
xrandr -s 640x480
I have some old desktop-crt combinations from the late 1990's running NetBSD and I use that to size X nicely onto the screen. If you type
at the terminal prompt it will give you what your card and screen supports or if you type
you will get a list of options to use with xrandr