>When I use the custom function FN SetCPixel  (Not the toolbox call, but the
>very quick  one that uses an array of pixel row addresses calculated at the
>startup to poke values directly into the PixMap) is it necessary to leave the
>PixMap that I'm using locked? Throughout the entire length of the program?
>Will the row addresses change, and will I get garbage? And will it then crash?

If you are addressing a GWORLD then you'll need to LOCKPIXELS.

If it's the screen that you're writing to (as in my original posting of FN
SetCPixel), you don't lock it. But beware of a variety of disasters that
can befall you: the user may move the window, change the screen pixel
depth, change monitor size...

Robert Purves