> My first attempt at implementing a bit-grabber was based on this
> assumption. When I tried this first implementation, the image would go
> into infinite debug-box loop whenever I moved my mouse cursor over one
> of my test images. It must therefore be the case that "pixelValueAt:" is
> a well-used subsidiary of Morphic and hence it's performance directly
> impacts the user experience.

That is quite unlikely. What you're seeing is a single hit-detection test
when you move the mouse and that's it (sketches use #pixelAt: for
hit-detection).

> I _THINK_ I have a working non-bitBlit implementation...

I would advise STRONGLY against a non-bitBlt implementation in the general
case (e.g., "improving" pixelAt: so that it doesn't use BitBlt). The reason
being that BitBlt can deal with "forms" that don't even live in the Squeak
universe (e.g., bitmaps on your native OS) that BitBlt will deal with lots
of varying color formats, little endian forms and lots of other things.

Cheers,
  - Andreas