Fixing size of window containing 2 buttons

[Jeffrey Barish <jeff_barish earthlink net>]

I am just starting with GTK, so no doubt I am missing something basic.  I
have a window with a buttonbox with 2 buttons.  I use size_allocate on the
buttons to position them.  One of the buttons starts hidden.  I would like
to size the window so that it will accommodate both buttons, but I keep
getting a window wide enough only for the one visible button.  I have tried
set_size_request on the window.  I tried catching size-request on the
window to confirm that the requisition is correct.  It is.  I also have
set_size_request on the buttonbox, which I believe should not be necessary
(and seems to do nothing).  What am I missing?
-- 
Jeffrey Barish