toolbars in small windows

[Bo Majewski <bo majewski com>]

Applications such as gedit have the ability to shrink to a size smaller
than their tool bar. In addition, when the window is too narrow to
display the entire tool bar, an arrow button is shown that when pressed
shows the remaining tool bar buttons.

Somehow I cannot convince my tool bars to behave this way. I was trying
to look into the code of gedit 2.2.2, but I failed to see what they do
that I don't. I would very much appreciate pointers, suggestions or URLs
that explain how to obtain the above described effects.

Bo