Re: U+25CA LOZENGE - why is it in the "Mac OS Roman" character set (and therefore widespread in current fonts)?

On 8/13/2012 10:11 AM, Peter Edberg wrote:
> I do not believe it was for accounting, logic, or mathematical use. It was included in the original "Macintosh" character set as shown in Figure 2 of the Font Manager chapter of Inside Macintosh, volume I (1985), but was not included in the shaded "mathematical" set in that figure. At that time it was shown with a shape more akin to that of U+25C7 WHITE DIAMOND. I think it may have been intended as an unfilled complement to the BLACK DIAMOND used as one of the Menu Manager user-interface elements at 0x11-0x14 in that figure. However, by the time of Inside Macintosh: Text in 1993, the character was shown with a shape more akin to that of U+25CA LOZENGE (see Figure 1-36, "The Standard Roman character set").
>
> I do not have any definitive word on this since I was not involved in the creation of the original Macintosh character set.

Adding on to Peter's information, in an attempt to be slightly more
definitive...

People are missing the fact that the lozenge as encoded at D7 in MacRoman,
but *also* was E0 in the Symbol set for the Mac. And E0 in the Symbol set
was mapped to "lozenge" in PostScript. So the proximate reason why
U+25CA LOZENGE
appeared in the Macintosh character sets can be laid at the feet of
LaserWriter
PostScript support, I suspect.

We did consider, back in 1990, whether the MacRoman D7 should be mapped
to U+25C7 WHITE DIAMOND, instead, but the decision, for whatever reason,
it was decided that MacRoman D7 and MacSymbol E0 were both lozenge. That
may account
for the shape change that Peter mentions in documentation from 1993.

There is some early font information which suggests that the original
intent,
however, may have been to have an open diamond. If you look at high quality
font documentation, e.g., the HP Book of Characters from 1992, the "MC Text
Symbol Set (12J)" shows an open diamond shape at D7, instead of the lozenge.
But the confusion regarding the identity of this character can be
illustrated by
comparing the "MS: PS Math Symbol Set (15M)", which shows an open diamond
at E0, versus the "AS: 'Symbol" Symbol Set (19M)", which shows a lozenge
shape
at the same position. Both of those fonts are clearly intended to cover the
same set, although the glyphs are all separately designed. Settling on
the lozenge
may have had more to do with Adobe designs winning out, rather than anything
else.

An open diamond is also rather common in various mathematical pi fonts from
the era, including Ventura Math, which was also closely related to the Adobe
symbol encoding.

Of course, it is a separate question as to why lozenge (or open diamond)
was added
to the MacRoman set in the first place, as well as the Symbol set --
that may
have something to do with early notions
about user-interface elements, as Peter surmises, but the fact that it
wasn't carried
over into most of the early non-Roman character sets for the Mac would
indicate that
even if it had been intended as a user-interface character of some sort,
that was
dropped in international usage.

I agree with Peter that the choice probably had nothing much to do with
accounting, logic,
or math per se, except insofar as one of those usages may have figured
into the choice
of elements for the original PostScript symbol set.

I can trace it back to a 1985 edition of the PostScript Language
Reference Manual.
If people *really* want to know what it was "for", I would suggest
starting there and
digging back further into the documentation trail at Adobe Systems prior
to 1985.
John Warnock is still around -- somebody who knows him could presumably just
ask him. ;-)

Regarding another stray comment in this thread, Michael Everson said:

"The LOZENGE is also found in DOS code page 437."

That is definitely not true. Michael may be misremembering the diamond
from the
set of 4 card suit symbols, which definitely are in DOS CP437.

--Ken
Received on Mon Aug 13 2012 - 14:27:00 CDT