I recently bought a touch screen off ebay. I hooked it up to my laptop and tested it to make sure it works. It does (only one dead pixel)! The next step was to hook it up to my desktop in a dual head configuration. This wasn’t difficult to do by any means, but it was a little bit tricky finding the option to set the screen order in TwinView. I have two monitors (one LCD w/ DVI and the touch screen TFT with VGA). By default, the Nvidia driver sets any VGA connection to screen 0. With a bit of digging, I found the “TwinViewXineramaInfoOrder” option from Appendix D of the Nvidia Linux Driver Readme/Install Guide:

Option "TwinViewXineramaInfoOrder" "string"

When the NVIDIA X driver provides TwinViewXineramaInfo (see the NoTwinViewXineramaInfo X config option), it by default reports the currently enabled display devices in the order “CRT, DFP, TV”. The TwinViewXineramaInfoOrder X config option can be used to override this order.

The option string is a comma-separated list of display device names. The display device names can either be general (e.g, “CRT”, which identifies all CRTs), or specific (e.g., “CRT-1″, which identifies a particular CRT). Not all display devices need to be identified in the option string; display devices that are not listed will be implicitly appended to the end of the list, in their default order.

Note that TwinViewXineramaInfoOrder tracks all display devices that could possibly be connected to the GPU, not just the ones that are currently enabled. When reporting the Xinerama information, the NVIDIA X driver walks through the display devices in the order specified, only reporting enabled display devices.

Examples:
“DFP”
“TV, DFP”
“DFP-1, DFP-0, TV, CRT”

In the first example, any enabled DFPs would be reported first (any enabled CRTs or TVs would be reported afterwards). In the second example, any enabled TVs would be reported first, then any enabled DFPs (any enabled CRTs would be reported last). In the last example, if DFP-1 were enabled, it would be reported first, then DFP-0, then any enabled TVs, and then any enabled CRTs; finally, any other enabled DFPs would be reported.

Default: “CRT, DFP, TV”

So, with that, it’s pretty easy to do. I set it to “DFP” and it now works great! For reference, here’s the device section of my /ect/X11/xorg.conf:

Section "Device"
        Identifier      "Configured Video Device"
        Driver          "nvidia"
        BusID           "PCI:1:0:0"
        Option          "RenderAccel"
        Option          "TwinView"
        Option          "TwinViewOrientation"      "LeftOf"
        Option          "TwinViewXineramaInfoOrder" "DFP"
EndSection