[plt-scheme] texpict: show-pict for big pictures

I'm running some prototype code to generate pictures using texpict;
right now I'm using show-pict to view the images.  Some of them are
too large for my screen and show-pict isn't putting in any helpful
scrollbars.  Is there a quick and easy way to throw together an image
viewer with scrollbars?  I'm hoping to avoid delving deep into the
MrEd documentation for combinations of controls, canvases, and
callbacks since my ultimate goal is output to postscript (but these
initial images are also too big for a page).  Anyone have a good
scrollbarred-image recipe on hand?

--Carl