need to rotate a pixmap with smooth filtering

Ok good. Perhaps the pixmap is corrupt, or we just need decent alpha values.

I presume it zooms in and out with the mouse buttons?

Yah, being within its own viewport is basically how the routine currently works. It needs to be turned inside out, to have the source counters made into the For-Next loop counters, and put the X and Y as separate counters with add-variables.