some general questions regarding gnustep-gui programming

[Sebastian Reitenbach]

Hi,

I've started with GUI programming, and now after a while I have some 
questions, where I did not found an easy answer.

I created a little application in PC and Gorm, which now just a main window, 
and a PreferencesController. I have two Interfaces one for the main 
application, and one for the PreferencesController.

I got the PreferencesController to work so that when I change there sth. the 
Default is changed persistently too, so thats fine. My immediate question 
here is just, how do I get sth. in the main window updated immediately, when 
I change sth. in the PreferencesController.
A pointer to some example source, to what look for, would be fine enough I 
think. A pointer to what to look for in the source, would be great, The 
basics of how do I get a PreferencesController to work I took from 
SimpleAgenda, but I did not found sth. yet, that helped me to understand how 
that could work. 
Also in SimpleAgenda, the Preferences controllers window is just only a 
NSPanel, whereas I use a NSWindow. Both work fine, I see no obvious 
differences, so here is a second question, what are reasons to choose 
NSWindow, or  NSPanel to implement any window besides the main app window?

Also in SimpleAgenda, but in other apps too, I've seen, they use 
multiple .gorm interfaces that then build the complete application. Therefore 
the reason that I also created a second .gorm interface for the 
PreferencesController window. On the other side, I've seen, I could also have 
done everything with one .gorm interface. So I also wonder here what could be 
reasons to choose one or the other way?

cheers
Sebastian