Multiple X sessions on dual head?

[yitzhakbg]

We want to run two independent, yet simultaneous X Sessions using a single GeForce4 Ti4200 board. See XFree local multi-user HOWTO at:
http://varna.demon.co.uk/~svetlio/ruby-contrib/how-to/XFree_local_multi-user-HOWTO/index.html.
Question is if it can be done and if so, how?
We have to use two separate XF86Config-4 files in order to bind the input devices to the correct monitor. How would we define the monitors? Can the monitor port be specifically forced to be the first or second port without using the dual "ConnectedMonitor" "crt, crt" notation, since we're not using TwinView? Or, should we use TwinView and define one session using "null, crt" and the other "crt, null"? Would the second instance clobber the first, or will the use of "null" ignore the relevant port?

[Misel]

with the latest NVidia drivers X can handle both screens independently (just like DualView under Windows) by doubling the screen, monitor and device section and adding "screen 0" or "screen 1" respectively to the corrensponding device sections.

Maybe you can use that one.

[yitzhakbg]

I'm afraid that solution won't work, because it's for a single instance of X, which has two screens. We're talking about a solution which has to run a separate instance of X for every monitor, because it has to assign a different keyboard and mouse to each screen. Even if we got the multi-screen in one instance working, how could two (or more) users work simultaneously? They would fight each other over gaining focus for their application.
What I want to know is if there is a way to explicitly assign a monitor to one of the two ports (using two different XF86Config-4 files) without messing up the other X session's assignment?

[Misel]

well, have you tried? :p ;)

[yitzhakbg]

Yes. I have tried what appears at the end of the driver 1.0-4363 README, Appendix F "Configuring Multiple Screens on One Graphics Card". The (two) mice are tied to one screen and the other screen has no client display, only background. I can overcome some of those problems with the Backstreet Ruby multiple console kernel (see URL from my first post). Now I'll try the multi-instance method and will report the results. Problem is, though, I don't know how to write the definitions in XF86Config-4. How should I define "ConnectedMonitor" in one file and how in the other?