Path: utzoo!attcan!uunet!munnari!murtoa.cs.mu.oz.au!news
From: news@cs.mu.oz.au (news)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Smoothly dragging small pictures
Keywords: drag smooth copybits offscreen
Message-ID: <1488@murtoa.cs.mu.oz.au>
Date: 12 May 89 08:21:31 GMT
References: <12492910881010@osu-20.ircc.ohio-state.edu> <1065@umn-d-ub.D.UMN.EDU>
Reply-To: jkjl@munmurra.UUCP (John Lim)
Organization: University of Melbourne, Comp Sci Dept
Lines: 22

From: jkjl@munnari.oz (John Lim)
Path: munnari.oz!jkjl

Why not simply  do

do {
	doCopyBits(); /* from offscreen to screen BitMap */
	ticker = TickCount();
	while (ticker == TickCount) /* do some background processing */;
} while (ContinueCopyBits);

The rationale behind it is that the value returned by TickCount() only
changes when the screen refreshing task is moving back to the top
of the screen and not redrawing the screen. Refer to Knaster's first book
(cant remember its title at the moment).

The advantage of this method is that you have time to do some
background processing, and you don't waste memory in allocating a 
second offscreen BitMap (which looks like a bit of a kludge to me).


	john lim