Packing & Selecting Icons/Buttons in a TreeView column

[Robert J Carter <rjc oghma on ca>]

I have an application where I want to place an icon at the start of a column, 
followed by text, in a TreeView.

Because of the way the treeview seems to handle indents, I'm trying to pack a 
pixmap and then the text into a single column using multpile cell renderers - 
THAT part is working fine.

The problem I'm having is this ..... when I click on the column, everything 
gets selected ok, and the the world is as it should be. But if the click is 
over the icon, I want to be able to invoke some code to "do stuff", instead 
of just select the row.

I can't seem to find any way to do that outside of writing my own custom cell 
renderer to impliment a pixmap-type button - any suggestions?