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From: CXT105@psuvm.psu.edu (Christopher Tate)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Animation
Message-ID: <91039.125723CXT105@psuvm.psu.edu>
Date: 8 Feb 91 17:57:23 GMT
References: <9102030634.AA09598@enuxha.eas.asu.edu>
 <1991Feb7.093610.12594@ecmwf.co.uk> <1991Feb7.233344.7781@umiami.ir.miami.edu>
Organization: Penn State University
Lines: 27

[ discussion on using TickCount to synchronize CopyBits to the vertical ]
[ retrace interval, to avoid flicker.                                   ]

Unfortunately, TickCount is only hardwired to the vertical retrace interval
on Mac Plus/SE - type machines (possibly the Classic; I don't know).  On a
Mac II series machine, the problem of multiple monitors rears its ugly
little head -- which monitor's vertical retrace are you synching to?

In fact, on a Mac II series machine, TickCount is anchored to an internal
60.15 Hz (is that right?) clock which has absolutely nothing to do with
the actual vertical retrace interval of any monitor.  In order to genuinely
synchronize your CopyBits (or whatever) to a monitor's vertical flyback,
you need to play some games with slot-based VBL tasks.

The Usenet Mac Programmers' Guide (UMPG) has a good article, with code, on
how to do just this.  As I recall the code is in C, but even if you're not
comfortable with C it's probably a good place to start.

And remember, you only have to monkey with slot VBL routines for this
stuff if you've determined that you're running on a Mac II-series machine.

-------
Christopher Tate                   | "Mr. Churchill, you're drunk!"
                                   |
cxt105@psuvm.psu.edu               | "Yes madam, and you are ugly.  In the
{...}!psuvax1!psuvm.bitnet!cxt105  |  morning, however, I shall be sober."
cxt105@psuvm.bitnet                |