inheritance vs composition with gtkmm

[Joe Van Dyk <joevandyk gmail com>]

In most of the gtkmm examples, I notice that inheritance is used for
almost all the GUI objects.

I've always thought that you should favor composition over inheritance.

Anyone have thoughts on the matter?  Does using inheritance make
things easier with gtkmm?  I guess from a readability, testing, speed
of development, and maintance viewpoint.

Thanks,
Joe