Developing and debugging UIs can be a pain. When something
goes wrong, it's not always obvious why. You can waste hours 
writing logging statements only to find out that a widget is
in the wrong container, or an attribute wasn't set correctly.

Developing isn't much better either. Ever spend time writing
temporary code just to test a new feature, code you know you're
going to throw away in an hour, and yet you end up spending the
next 20 minutes debugging your temporary code? Sucks, doesn't
it?

What your program really needs is a good Parasite infestation.

Parasite is a debugging and development tool that runs inside
your GTK+ application's process. It can inspect your application,
giving you detailed information on your UI, such as the hierarchy,
X window IDs, widget properties, and more. You can modify properties
on the fly in order to experiment with the look of your UI. 

WWW: http://chipx86.github.com/gtkparasite/