DrawingArea in ScrolledWindow

["Mark Tilford" <ralphmerridew gmail com>]

I have large DrawingArea contained within a ScrolledWindow.

1)  If I don't disable double-buffering, how much memory will the
buffering pixmaps use: the size of full DrawingArea, or just the part
that's visible through the viewport?

2)  How can I get the dimensions of the visible part?  (I tried
manually adding the Viewport, then calling
get_window()->get_geometry(), but that gave a value slightly too
large; that seems to track things unnecessarily and I'm not sure
exactly how much I need to deduct.)

3)  How do I change the apparent dimensions of the contained widget?