subclassing gtkcheckbutton

[Deborah Swayne <dfs research att com>]

I would like a widget that is just like a checkbutton, but with two
checkbox areas for one label.  The left one responds to left button
events, and the right one to middle and right button events.

Would it be a better strategy to subclass the checkbutton
directly, or to start by subclassing the togglebutton, and
then subclassing that subclass?

If you have a better idea for achieving this goal, let me know --
I want two indicators and one label.

Debby