Path: utzoo!attcan!uunet!husc6!bloom-beacon!bu-cs!dartvax!eleazar.dartmouth.edu!earleh
From: earleh@eleazar.dartmouth.edu (Earle R. Horton)
Newsgroups: comp.sys.mac.programmer
Subject: Re: CopyBits and the Mac II
Message-ID: <10024@dartvax.Dartmouth.EDU>
Date: 7 Sep 88 23:06:25 GMT
References: <51404DN5@PSUVM> <10006@dartvax.Dartmouth.EDU>
Sender: news@dartvax.Dartmouth.EDU
Reply-To: earleh@eleazar.dartmouth.edu (Earle R. Horton)
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In article <10006@dartvax.Dartmouth.EDU> earleh@eleazar.dartmouth.edu (Earle R. Horton) writes:
>In article <51404DN5@PSUVM> DN5@PSUVM.BITNET (D. Jay Newman) writes:
>>Hi out there:
>>
>>I am programming a simple animation on the Mac (a simple polygon rotating
>>around the center), and to make it smoother I used an off-screen bitmap,
>>and I used CopyBits to get it onto the screen (like TechNote 41).
>>
>>This works correctly with a Mac Plus, but the Mac II includes a lot of
>>garbage in the rectangle with the rotating polygon:  I can still see the
>
>I am doing something very similar on the Mac II, a rotating three
>dimensional whatchamacallit.  On the II, I use color windows and
>PixMaps, rather than BitMaps, for the offscreen storage.  This is
>explained in TechNote 120, along with example MPW Pascal source...

The problem turns out to be that on the Mac II, the offscreen BitMap
appears to need its own GrafPort, whether you are using Color
QuickDraw or Vanilla QuickDraw.  I suggested to Jay that he try
attaching his offscreen BitMap to a separate port, opened using
OpenPort.  Then instead of using SetPortBits to switch between
BitMaps, use SetPort to switch between ports.  This cured his problem,
according to mail he sent me today.

The technique described in Technote #41 doesn't appear to work
properly on a Mac II, then.  I would like to see a revised Technote
#41 giving a method of drawing to an offscreen BitMap which is upward
compatible from the Mac Plus and SE to the Mac II.  Then developers
who don't have access to a Mac II and who want to do animation would
have a better chance of being upward compatible...


Earle R. Horton. 23 Fletcher Circle, Hanover, NH 03755
(603) 643-4109