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From: chavez@quorum.com (R. Martin Chavez)
Newsgroups: comp.sys.next
Subject: Re: Instance dwg & the Draw app
Message-ID: <1990Aug22.080946.15806@quorum.com>
Date: 22 Aug 90 08:09:46 GMT
References: <0aoJMxC00WBLE1L0gM@andrew.cmu.edu>
Organization: Quorum Software Systems, Inc.
Lines: 16

cc3z+@andrew.cmu.edu (Christopher N. Carlson) writes:

>Can anyone explain why the Draw app doesn't use the instance drawing
>mechanism?  Is this purely for pedagogical reasons?  Or is instance
>drawing somehow inappropriate in this context?

Instance drawing, though extremely fast, leaves a noticeable flicker
on the screen (even with buffered windows).  The compositing algorihm
used by the Draw app provides for a much smoother rubberbanding effect.
TopDraw employs a similar mechanism.

In general, I'd recommend that you break out the Draw app's compositing
and offscreen-window code for most rubberbanding applications.

R. Martin Chavez
Quorum Software Systems, Inc.