plot(3,5) vs. non-square plot areas

[Henry Spencer]

In the course of some work on our plot(5) filter for the HP 7470A plotter,
we ran across an interesting question:  just what does it mean if you ask
plot(3) for a non-square space?  There are two possible interpretations:

	1. The viewport (physical plot area) remains square, and the
		coordinate scaling is not the same in X and Y.

	2. The viewport is as large as it can be, within the available
		physical space, while preserving the aspect ratio of
		the space() request.  So the X and Y scales are the same.

The Bell documentation strongly implies interpretation (1), and that's
what their plot(5) code seems to do.  Our opinion is that (2) is much more
useful behavior -- in particular, it makes it possible to use the full area
of non-square devices safely -- and is unlikely to break anything.  The
Bell graphics software we've examined invariably uses square spaces, so it
would be unaffected.

Does anybody have any opinions on this?  Anybody know for sure whether
any Bell stuff exploits interpretation (1)?

[Just in case anybody is wondering, the 7470A code we posted to the net
a little while ago went for interpretation (2).]
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry