Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!cs.utexas.edu!uunet!jarthur!wilkins
From: wilkins@jarthur.Claremont.EDU (Mark Wilkins)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Switching video pages on Mac Plus- How?
Keywords: video pages, alternative video page
Message-ID: <2805@jarthur.Claremont.EDU>
Date: 3 Nov 89 23:50:07 GMT
References: <4296@blake.acs.washington.edu>
Reply-To: wilkins@jarthur.UUCP (Mark Wilkins)
Distribution: na
Organization: Harvey Mudd College, Claremont, CA
Lines: 19

In article <4296@blake.acs.washington.edu> busey@blake.UUCP (Thomas Busey) writes:
>Yes, I know it's a no-no, but the psychology lab I work in needs the 
>ability to alternate between two pictures on a mac screen at speeds 
>up to 60 switches a second.

[ stuff deleted ]

>and forth between the two pages.  I need to control this switch with
>the tickcount variable for standardization.

   Don't use tickcount.  Tickcount is often not updated strictly every 1/60
of a second and there can be trouble if you use it for precise timing
because disk accesses and cursor movement can prevent it from being updated
before another vertical retrace interrupt happens.
Using the Time Manager will allow a routine you indicate to be called in an
amount of time which can be specified precisely to the millisecond.  Look
somewhere near the end of IM IV.

      -- Mark Wilkins