nUI should reduce active screen area

Background:
It took me some time to figure out, but nUI does not alter the active screen area. In my setup (1280x800 screen), the top 23 lines and the bottom 155 lines of the screen are hidden behind nUI and fubar (font resolution 10). However, there is still a lot of interactive things happening behind the hidden parts.

Temporary solution:
I have used CT_ViewPort to reduce the active screen area.

Suggestion:
This should be handled internally in nUI.