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From: hmm@exunido.uucp (Hans-Martin Mosner)
Newsgroups: comp.lang.smalltalk
Subject: Re: Pen (again)
Message-ID: <2761@laura.UUCP>
Date: 2 Nov 90 13:49:28 GMT
References: <Oct.29.17.17.44.1990.23321@caip.rutgers.edu>
Sender: news@laura.UUCP
Reply-To: hmm@exunido.UUCP (Hans-Martin Mosner)
Organization: Georg Heeg Smalltalk-80 Systeme
Lines: 16

When I was at ParcPlace some months ago, I implemented a rudimentary Pen
substitute for release 4.  The problem mainly was that the new SPIM sits
on the host window system which means that window contents are not saved
as they were in 2.5 and before.  So you could just scribble on a window with
a simple Pen implementation, but any pop-up menu or occluding window would
destroy your drawing.  What I did was implement a kind of polyline with width
and color that would accumulate pen commands and be able to reconstruct the
pen drawing when necessary.  I did some quite nice fractal trees (and all of
the old Pen examples, of course).  Alas, due to very tight time constraints
for my flight back I forgot to take this stuff with me.  Anyway, it is rather
simple to implement a mechanism like this.  The hardest part is to make the
graphics interactive in the sense that you see the evolving picture while the
Pen code is running.  In some days I will probably have this stuff and can
post it to the newsgroup.

	Hans-Martin