Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!ncar!tank!mimsy!mojo!russotto
From: russotto@eng.umd.edu (Matthew T. Russotto)
Newsgroups: comp.sys.mac.programmer
Subject: Re: alternate screen buffer on Mac II
Keywords: alternate screen buffer, Mac II, VIA register
Message-ID: <1990Mar16.040417.2257@eng.umd.edu>
Date: 16 Mar 90 04:04:17 GMT
References: <1990Mar13.040203.6874@Neon.Stanford.EDU> <16691@well.sf.ca.us> <1990Mar15.222250.7763@athena.mit.edu>
Sender: news@eng.umd.edu (The News System)
Organization: Maryversity of Uniland, College Park
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In article <1990Mar15.222250.7763@athena.mit.edu> rsfinn@athena.mit.edu (Russell S. Finn) writes:
>In article <16691@well.sf.ca.us>, brecher@well.sf.ca.us (Steve Brecher) writes:
>> 
>> In article <1990Mar13.040203.6874@Neon.Stanford.EDU>,
>> carter@Neon.Stanford.EDU (Thomas J. Carter) writes:
>> 
>> > ...I'm having trouble finding the alternate screen buffer on a Mac II
>> > with a combination of monitors.  Can this be done?
>> 
>> No.  An alternate screen buffer is not a feature of Mac II video.
>
>Now, far be it for me to contradict one of the Big Names of the
>Macintosh Community, but it *is* possible to do page flipping on (at
>least) a standard Apple Video Card.  The problems are that it's not
>documented very clearly; it's a function of the video card, not the main
>hardware; you have to make calls directly to the video driver (i.e., you
>can't just flip a bit in the VIA); and it's not recommended by Apple. 
>However, if you're really game, it's possible.  You have to go digging
>in the Apple "Designing Cards and Drivers for the SE and II" book, and
>look in the chapter on video drivers; the information is there.  (Sorry
>I can't be more specific, as I don't own this book, or a Mac II; but I
>*have* seen it done.  It should work on any third-party video card that
>supports *all* the standard video driver calls; apparently, few of them do.)
>
>-- Russ
As far as I can tell, you cannot actually do page flipping.  What you can
do is change the area of video card memory that you are actually displaying
It doesn't seem to be possible through the driver calls-- they return
controlErr.
--
Matthew T. Russotto	russotto@eng.umd.edu	russotto@wam.umd.edu
][, ][+, ///, ///+, //e, //c, IIGS, //c+ --- Any questions?