seth@CS.UCLA.EDU (12/18/87)
Well it's time for another naive mac programming question. I'm trying to do
following:
Set up two offscreen bitmaps A and B. Do all my drawing on A and B
(rectangles, lines, and text) and then bitblt from A and B onto the
window I've created on the screen W. I want the images in A and B to
persist so that if W gets messed up I can update it just by blitting
from A and B. I'm using Allegro CommonLisp but have access to the
entire toolbox as needed. I'm confused about whether A and B can
just be bitmaps or need to be full-fledged grafports in their own
right. I've checked IM and it talks about using SetPortBits to draw
to offscreen bitmaps and then using CopyBits to update the screen
but I can't figure it out and there are no examples.
I would greatly appreciate it if someone could take a little time and
explain it to me. I have various versions of my code which behave
strangely but the one where I thought I had it right resulting in nothing
being drawn. How do I create a real offscreen bitmap? What are the
bounds for that bitmap (i.e. off the screen?). What is the portrect
if the offscreen bitmap needs to be a grafport?
Thanks,
Seth Goldman
ARPA: seth@CS.UCLA.EDU
UUCP: ...!{ihnp4,cepu,trwspp,sdcrdcf,ucbvax}!ucla-cs!seth
USMail: A.I. Lab, 3531 Boelter Hall, UCLA, Los Angeles, CA 90024
MaBell: (213) 825-5199