I had difficulty following the explanation. Sorry If I misunderstand what you're trying to accomplish, Vincent.
On the drive home I was thinking about this. The following little demo might suit your purpose? http://trollsouttaluckland.googlecode.com/files/subsurf_as_viewport.py It assumes you want to draw only a small portion of a large panning image in a static area of the screen. Ignore the math; it's only there to produce some interesting movement. The relevant parts are the rects, subsurface, and blit. Gumm
