Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!pasteur!ucbvax!dewey.soe.berkeley.edu!oster
From: oster@dewey.soe.berkeley.edu (David Phillip Oster)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Wide offscreen bitmap won't receive draw commands
Message-ID: <30803@ucbvax.BERKELEY.EDU>
Date: 22 Aug 89 06:13:46 GMT
References: <22321@andante.UUCP> <30755@ucbvax.BERKELEY.EDU> <34168@apple.Apple.COM>
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Reply-To: oster@dewey.soe.berkeley.edu.UUCP (David Phillip Oster)
Organization: School of Education, UC-Berkeley
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When I tested it in 1987, Inside mac was wrong:
you had to set the visRgn to the portRect, if the the bitmap was bigger
than ScreenBits.bounds. And, it stands to reason that this should be so,
since how would quickdraw know that thePort is just a port and not a
window?

Further, you do a ClipRect(&thePort->portRect) not to clip the image to
the bitmap, QuickDraw will do that anyway, you do it, so if you record a
picture in that port, then do a DrawPicture to some other port, if you
adjust the location, a default clipRgn will overflow into an empty
rectangle.

Also, if you want fast drawing, create a pixMap the same depth as the
destination. Sure Quickdraw will convert it up or down, but it is much
faster to do it right yourself.

Check out my Griffeath color cyclic automata program (freeware, archived
on sumex-aim.stanford.edu) It uses optimized assemply language to diddle
am offscreen 8-bit deep pixmap, then calls CopyBits to display it. Notice
how much slower it runs if you set the screen to 4-bits per pixel instead
of 8.
--- David Phillip Oster      7 line signature follows
Keith Sproul, head of microcomputer support at Union Carbide, NJ, complained
about the poorly digitized fellatio on an IBM porno program. "Mac is better
on everything, and this is no execption."  -- "Computer Porn at the Office"
by Reese Erlich, _This_World_, S.F. Chronicle, p.8, Aug 13, 1989

Arpa: oster@dewey.soe.berkeley.edu
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