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Path: utzoo!linus!philabs!seismo!hao!hplabs!sri-unix!Mackey.PA@PARC-MAXC.ARPA
From: Mackey.PA@PARC-MAXC.ARPA
Newsgroups: net.works
Subject: Re: Track Ball a la Centipede instead of a mouse
Message-ID: <15582@sri-arpa.UUCP>
Date: Mon, 16-Jan-84 18:09:16 EST
Article-I.D.: sri-arpa.15582
Posted: Mon Jan 16 18:09:16 1984
Date-Received: Thu, 19-Jan-84 01:11:46 EST
Lines: 35

From:  Kevin <Mackey.PA@PARC-MAXC.ARPA>

(Reply to Tague%pco@CISL-SERVICE-MULTICS.ARPA message in V4 #7)

I've seen the same idea on April 2, '83 from David Chin
<chin%UCBKIM@Berkeley> on this Digest (don't know the volume or number).

I don't think it's a good idea. I've used trackballs on several video
games, and think they would have problems in the arrangement you
suggest. First, moving it with the thumb would be difficult. The thumb
only moves freely in an arc, so it can only move the ball in 2
directions. You'd have to rotate your hand to get more directions, but
this is awkward. Using both thumbs you'd have four, but that would
require some interesting coordination! Using your palm might be best,
but you'd have to position the ball in such a way that the typist
doesn't accidentally hit it while typing.

Second, if you've ever used a trackball, you know that it has to be
stroked to spin enough, even with some kind of
magnification/acceleration factor in the software. Stroking means moving
your hand and/or arm back and forth rapidly several times, which can be
very tiring. It also requires room around the ball (out of the way of
keys) for the hand to move before and after a stroke.

Finally, you can't spin the ball while holding down the button as easily
as you can with the mouse (need 2 hands, not just one). Why is this so
important? Well, it's used extensively on the Lisa, and is a nice way to
gradually extend a selection. Other selection methods could be used, but
this is a nice one.

More than a little engineering would be required to make a trackball
work as a good pointing device, and even then I don't think it would be
effective, due to it's inherent limitations.

~Kevin