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From: thomas@eleazar.dartmouth.edu (Thomas Summerall)
Newsgroups: comp.sys.mac.programmer
Subject: Mac II retrace manager and Tick Counts
Message-ID: <24126@dartvax.Dartmouth.EDU>
Date: 10 Sep 90 18:22:38 GMT
Sender: news@dartvax.Dartmouth.EDU
Organization: Dartmouth College, Hanover, NH
Lines: 19
Originator: thomas@eleazar.dartmouth.edu

In the never ending quest for smooth animation on the mac, Mac Plus
programmers have one friend:  the tick count coincides with the vertical
retrace period so that programmers can use

tickvalue:=TickCount                  {tickvalue is a LongInt}
repeat until (tickvalue<>TickCount)

to tell them when a new blanking period occurs.  This allows them to simulate
an interrupt driven routine without the headaches caused by interrupt routines.
(ie they can't rely on unlocked handles, etc, because they don't know what the
momory manager might have been doing when the interrupt occured)

Is there anyway to simulate this on the Mac II?  Does the apple video card
generate a tick of some kind?  I just don't have enough experience to know what
I can and can't do in an interrupt driven SlotVInstall routine, and I don't
want to find out by trial and error if I don't have to...

Thanks,
Thomas Summerall