Quote Originally Posted by high_flyer View Post
yes I must use Xinerama - if I want the desktop to span on all my screens.
I think you could have two separate screens (not combined into one).

I can't really say if other applications behave the same way - or let me put it this way - I haven't notices other applications to open windows not on the same screen...
Try running gimp, move it to the second screen and open some dialog from it. This will be one test. But then make another test - move the child dialog to the first screen and open a child dialog from the child dialog. Of course you'll need to find a proper set of dialogs to do that