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From: gus@Shasta.ARPA
Newsgroups: net.micro.mac
Subject: Re: Grow Regions
Message-ID: <1575@Shasta.ARPA>
Date: Fri, 6-Dec-85 13:12:56 EST
Article-I.D.: Shasta.1575
Posted: Fri Dec  6 13:12:56 1985
Date-Received: Mon, 9-Dec-85 04:02:00 EST
References: <8512060411.AA13585@kim>
Organization: Stanford University
Lines: 9

> this has got to be a non-trivial operation, saving the bits under the outline,
> writing the outline, then restoring the saved bits after the outline moves.
> Do we mortals have access to some semi-highlevel routine which does this for
> us?  Or am I going to have to kludge something up?  Many thanks in advance.
> 
> Steve Upstill

It's called XOR. Try it some time. XORing a line on a background puts
it there, drawing the same line again in XOR puts takes it away.