Re: offscreen rendering (a hack)

[Steve Williams]

of "done" when rendering and so it's sometimes difficult to catch things 
when it's a good time to take a "snapshot".

You can add some code to nsWindow::OnPaint to register an update 
rectangle. In your snapshot loop, you can iterate through
all nsWindows to see which ones have been updated, do some processing
on the update rectangles to form a dirty rectangle list, then blit
those rectangles to your destination surface. Or something like that ...