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From: barmar@think.COM (Barry Margolin)
Newsgroups: comp.sys.mac
Subject: Re: Inverse video/text
Message-ID: <38395@think.UUCP>
Date: 3 Apr 89 04:11:25 GMT
References: <6806@saturn.ucsc.edu> <141200011@cdp> <5894@pdn.paradyne.com>
Sender: news@think.UUCP
Reply-To: barmar@kulla.think.com.UUCP (Barry Margolin)
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 19

Actually, I believe that what was patented was the use of XOR to
display a movable cursor on a raster display.  This technique allows a
cursor to be displayed over existing portions of the display without
requiring additional storage for the old contents of the overlaid
area.  When the cursor moves you simply XOR it again in the old
location to restore the original contents.

It may also cover things like blinking block cursors.  I suspect it
DOESN'T cover the standard Macintosh arrow mouse cursor, since that
displays a black arrow, rather than an inverted arrow.  However, it
inverts the border, so that the arrow is still visible on a black
background; I don't know whether this hybrid scheme is covered by the
patent.

Barry Margolin
Thinking Machines Corp.

barmar@think.com
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