ok, I understand the "virtual" concept, thanks prplxd. But if you put "virtual 0 0" does it means that it takes the addition of the two values of your metamodes : 2048=1024+1024+0 and 768=768+0?
Other question : do you know if it's possible to have a different virtual screen for each mode of my "Metamodes".
I explain :
in my Device section, I put this line :
Option "MetaModes" "1024x768,1024x768;1024x768,NULL"
doing like this, I have twinview whis the first Metamode and I switch on the second metamode (with Ctrl-Alt-+) to have only one active monitor, for example to play games (on the dual screen, the games were centered on the two monitors, so it was impossible to play).
but the problem is that on this mode I have a 2048x768 screen on one monitor. (in fact, when I put the cursor of my mouse on the right of my monitor, the screen scrolls until 2048 <--scuse me but I haven't the good words to explain this in english ;-)
So, I wonder how to configure that : maybe having in the screen section a line "Virtual 0 0" corresponding to the first metamode and a line "Virtual 1024 768" corresponding to the second metamode...but I tried in vain.
It's a big problem because some games like frozen bubble are not in full screen even if I put the full screen mode...
Does someone know how to do that?