Thanx for the answer, lucamar
I've searched my known sources but did not find anything.
But now I know something useless:
How to prohibit that the user of your app does not change this virtual screen.
Very simple:
screen.MoveFormToZFront(self);
My hope was that the app would appear on the virt screen I just changed to.
But - buff - I was sent back to the virt screen I came from.
Must have a deeper look.
If that does not help I will have a look to the KDE interface.
Winni