Forcing size_allocate?

[The Surprises <thesurprises1 attbi com>]

I have a gnome_canvas packed into a vbox.  The drawing inside the canvas
is handled during a size_allocate event because I need to know the
width/height before I draw.  This works well when I resize, however upon
startup, the drawing is blank until I manually do a resize.  How do I
force a size_allocate event to get the initial graphics drawn?

Thanks
Jason