Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!ames!amdahl!nsc!voder!apple!darin
From: darin@Apple.COM (Darin Adler)
Newsgroups: comp.sys.mac.programmer
Subject: Re: flicker-free drawing
Message-ID: <14772@apple.Apple.COM>
Date: 27 Jul 88 04:57:47 GMT
References: <5727@orstcs.CS.ORST.EDU> <12549@agate.BERKELEY.EDU> <424@umn-d-ub.D.UMN.EDU>
Reply-To: darin@apple.apple.com.UUCP (Darin Adler)
Organization: Apple
Lines: 20

In article <424@umn-d-ub.D.UMN.EDU> gandreas@ub.d.umn.edu.UUCP writes:
> In article <12549@agate.BERKELEY.EDU> lippin@math.berkeley.edu writes:
> >Recently jasmerb@orstcs.CS.ORST.EDU (Bryce Jasmer) said:
> > >I am writing a DA that needs to have flicker free drawing...
> >A better way to avoid flicker is to skip the erasing that causes it,
> There are more problems than that.  When you (or at least when I) use
> srcCopy for text, it will often erase more than just to the end of the last
> letter.  It seems that it erases up to the next byte/word boundary (?), ...

This extra erasing is actually related to the italic and bold styles (believe
it or not). I do agree with the main point of this discussion, which is that
the way to avoid flicker is by avoiding erasing before drawing something in.
Off-screen bitmaps are often the best way.

Note that the TickCount method that was mentioned in the message that started
this chain is not valid on modern Macs (Mac IIs) that have screens with refresh
rates other than 60Hz. TickCount stays at 60Hz no matter what.
--
Darin Adler					       AppleLink: Adler4
UUCP: {sun,voder,nsc,mtxinu,dual}!apple!darin	  CSNET: darin@Apple.com