starting with release 304 of the NVIDIA linux driver series, panning no longer works on the NV40 based graphics cards. If I enable panning with the NVIDIA GUI, I do get a larger screen, however, signalling to X11 seems to be somewhat broken in the sense that the additional area that becomes available due to panning is just black and not filled with the background graphics. All X11 operations that work on the root window just seem to see the upper left edge (i.e. the regular area) instead of the full screen. This includes the background wallpaper, but also gksu freezing the root window etc…
The problem does not appear with the older 295.75 where panning was supported “correctly” (i.e. in the sense that the nvidia tool was able to create virtual resolutions with panning enabled.) Unfortunately, the xrandr --panning option does not work with either release.
I would also like to attach a screen shot, but I don’t quite see how to do that here in the forum.