gtktree signal question

[Michael Lausch <mla gams co at>]

I looked at the FAQ and the source but can't resolve what signals a
gtktree widget emits under which cicumstances. I also recognized that
a tree item can be in one of 3 states, unselected, selected1 (with a
blue background), and selected2 (with a box drawn around it). How do i 
skip one of this states (the one with the box is unnecessary for my
planed application.