loops, doesn't deal with failure, doesn't present the interface to
drivers that I expected) and instead replace it with a simple fallback
to software when coordinate limits could be violated. Act similarly in
other acceleration cases as well.
The solution I want to see (and intend to do soon) is to (when necessary)
create temporary pictures/pixmaps pointing towards the real ones' bits,
with the offsets adjusted, then render from/to those using adjusted
coordinates.
