Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!sun-barr!apple!lsr@Apple.com
From: lsr@Apple.com (Larry Rosenstein)
Newsgroups: comp.sys.mac.programmer
Subject: Re: DragGrayRgn() procedure problem with color.
Message-ID: <13366@goofy.Apple.COM>
Date: 6 May 91 20:36:22 GMT
References: <1CE00001.ei5m1b@tbomb.ice.com> <1991May4.232051.13698@agate.berkeley.edu>
Sender: usenet@Apple.COM
Organization: Apple Computer, Inc.
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In article <1991May4.232051.13698@agate.berkeley.edu>,
deadman@garnet.berkeley.edu (Ben Haller) writes:
> 
> be reversible, i.e. a
xor b xor b must equal a.  When you set the hilite
> bit you mess this up,
since you've told QuickDraw to perform a
> non-reversible operation.  

You
are right about the interaction between hilite mode and regular XOR.  But I
believe that hilite mode is also reversible operation, since it exchanges
the background and hilite colors.  But you can't interleave hilite and XOR
drawing and expect to get the original display.