[comp.sys.mac.programmer] Wide offscreen bitmap drawing--solved

bwb@andante.UUCP (Bruce Ballard) (08/21/89)

My thanks to Patrick Beard, Greg Marriott, David Phillip Oster,
and Keith Rollin for pointing me to the solution of the wide
offscreen bitmap problem.

The solution was to pay attention to visRgn, not just clipRgn, e.g.

	ClipRect(&g->portRect);
	CopyRgn(g->clipRgn, g->visRgn);

which I might have known to do from the definition of OpenPort given
on IM I-163 which clearly says that visRgn is set to a "rectangular region
coincident with screenBits.bounds. I was in fact misled by a line from
IM I-149, "the visRgn has no effect on images that aren't displayed on the
screen". Perhaps TN-041, "Drawing into an Offscreen bitmap", mention this,
should have mentioned the need to play with visRgn.

Thanks again to people listed above.

-Bruce Ballard
bwb@allegra.att.com