Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!zephyr.ens.tek.com!tektronix!reed!chaffee
From: chaffee@reed.UUCP (Alex Chaffee)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Animation
Message-ID: <16145@reed.UUCP>
Date: 26 Feb 91 06:14:06 GMT
References: <12151@goofy.Apple.COM>
Reply-To: chaffee@reed.UUCP (Alex Chaffee)
Organization: Reed College, Portland OR
Lines: 41

> Baudoin Raoult tells us how to sync to the vertical retrace on
  small-screen Mac's:

  tmp := TickCount;  
  while tmp=Tickcount do { nothing } ;  
  CopyBits(.....)

> Lawson English says:
  [use GetTrapAddress]

> Brent Schorsch says:
  [use the global variable Ticks]

> Rick Holzgrafe replies:
  [it's not safe - Be Compatible!]

I jumped into the middle of this thread, so this might have been addressed
earlier, but if you're going to try to be compatible, why not go whole hog
and be able to work on Mac II's?  Using SlotVInstall, you can set up a VBL
task which is synched to the monitor, regardless of phase or refresh rate.
Then this VBL task will increment a global - call it vCount - every single
screen refresh. Then you can use vCount just like you use Ticks was in the
original code fragment. If you like, I can send (or post) source code that
does just this. By the way, I don't always align my right margins; it just
seemed to work out that way this time.

	/* beginning of program */
	SlotVInstall(...)
	...
		/* middle */
		tmp = vCount; while(tmp==vCount) ;
		CopyBits(...)
	...
	/* end of program	*/
	SlotVRemove(...)

-- 
Alex Chaffee
chaffee@reed.{UUCP,BITNET}
Reed College, Portland OR 97202
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