Anyways, I'm currently running xorg in Xinerama mode using two different video cards. My window manager (kwin) thankfully detects that and acts accordingly (i.e. when asked to center stuff centers them on the current active monitor, etc).
My question is, under ati big desktop and nvidia twinview, are the two monitors also "visible" for the window manager to act like this? I saw kde open windows in the middle of the two screens on a linux computer the other day, and while I didn't find out if it was nvidia/ati or something else, i'm interested in finding it out, because i'm thinking of dumping these two old graphics cards and buying a decent one with dual vga.
Can anyone share some experiences?
Also, does anyone know what's the current status of Xgl + dual monitors?
Can't comment on Xgl with dual monitors, but I do have some experience with twinview.
As long as your apps are compiled with support for Xinerama they should properly detect the boundaries of your monitors with respect to the whole desktop. nvidia also has a utility (nvidia-settings) which lets you synch xv video output to the monitor of your choice (very convenient for LCDs at the least).
I presume it should work with the Ati drivers because if they support twinview/xinerama extensions then it should be ok. Before you could only run Xgl/Compiz on one monitor because compiz didn't use the xinerama extension but now it does...