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Path: utzoo!linus!philabs!cmcl2!harvard!seismo!hao!noao!terak!doug
From: doug@terak.UUCP (Doug Pardee)
Newsgroups: net.graphics
Subject: Re: exclusive-ORed cursors
Message-ID: <745@terak.UUCP>
Date: Tue, 1-Oct-85 12:26:50 EDT
Article-I.D.: terak.745
Posted: Tue Oct  1 12:26:50 1985
Date-Received: Fri, 4-Oct-85 05:28:10 EDT
References: <588@stc-b.stc.UUCP> <5988@utzoo.UUCP> <914@turtlevax.UUCP>
Organization: Calcomp Display Products Division, Scottsdale, AZ, USA
Lines: 20

> FLIPping is used mostly for cursors and rubber-band lines; its only
> useful definition is that there is no net change after doing a FLIP
> with both source and destinations the same.  This is usually
> implemented by performing a generalized exclusive-OR of the source with
> the destination.

Just so you'll know...

The use of exclusive-OR to draw and erase cursors, rubber band lines,
etc. is covered by patent number 4,197,590.  The holders of that patent
are, um, "aggressive" about defending their patent.

Nearly as I can tell, the company that holds that patent produces no
products; its only income is from license fees on that patent.

[Don't flame *me* if you think it's not patentable, I agree.  But that
doesn't help any when your company is given the choice: license or
court, where it'd cost more to win the suit than to buy a license.]
-- 
Doug Pardee -- CalComp -- {calcom1,savax,seismo,decvax,ihnp4}!terak!doug


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