getting a scrolled window to be "big enough"

[Paul Barton-Davis <pbd Op Net>]

it seems that whenever i stick a box widget into a scrolled window,
the scrolled window fails to take on the natural size of the box, but
instead seems to shrink to be about as small as it can be.

my normal workaround for this is to use set_usize() to pre-establish
some minimum size. having read havoc's description of why this is a
bad idea, i am trying to figure out how to get a scrolled window to
assume some "natural size".

basically, i am the scrolled window to allow the *possibility* of
scrolling, but only if the user takes actions that add more widgets to
the container within the scroller. when the program starts up, i'd
like the scrolled window to be large enough for its current contents
(which i know will be a reasonable size).

hints ?

--p