How to make roster collapsable?

Hi! I try customize the Tkabber for LAN usage. I want to make roster collapsable. It should work like this: user click a button(or dbl-click on the splitter's square) and the roster's width will change to 0. And when user will do that action again, roster restore its width.

I'm going to learn tcl/tk, and now i'm beginner. I think that it is not hard thing for prof-programmers. =)

And little questions, that can help me to do collapsable roster myself...

1. How to change geometrical propertions of the window's frames. (Roster, MUC Contacts, InputText and other). How do that from plugin.

2. How add button somewhere on the window. And is it possible to do that from plugin too.

3. How "learn" the button from item2 to do action from item1... =)

I think, there are absolutely lamer-questions, but I am only at the start of understanding how works anything in tcl/tk... =)