Re: Unicode support for Troff-specific symbols

[G. Branden Robinson]

Hi John,

At 2024-08-14T18:43:44+1000, John Gardner wrote:
> In Unicode 13.0, a new block
> <https://www.unicode.org/charts/PDF/Unicode-13.0/U130-1FB00.pdf> was
> added to support graphical symbols used on legacy systems,[1]
> particularly those represented by obscure character encodings (like
> ATASCII <https://en.wikipedia.org/wiki/ATASCII>).[2]
> 
> I'm wondering if Troff's non-representable symbols (listed below) are
> eligible additions for this block. I'm envisioning their admission to
> use names like:
> 
> \[sqrtex] radical symbol extension[3]

This one had precedent in Adobe Type 1 fonts too.

https://savannah.gnu.org/bugs/?63179

> \(ul      troff under rule

I think we spell it "underrule".

> \(ru      troff baseline rule
> \(bs      troff client logotype[4]

Heh.  Yet another computer science problem solved with a layer of
abstraction.

> Giving these characters a canonical representation in Unicode won't
> benefit documents typeset by older troff(1) implementations, but it
> would simplify documentation of future Groff releases and smooth out
> wrinkles in text copied from gropdf(1) output.

Sure.

> Does this seem realistic to anybody else?

Seems worth a try.  These characters have provenance going back to the
original CSTR #54 in 1976.

>    2. A supplementary block
>    <https://www.unicode.org/charts/PDF/Unicode-16.0/U160-1CC00.pdf>
>    featuring Pac-Man and Space Invaders graphics has also been
>    approved for the upcoming Unicode 16.0 (published next month).

Oh, good, I successfully procrastinated updating for 15.1 for so long
that I won't have to do it.  Just skip ahead to 16.0.

>    4. I'm aware that corporate logos can't be added to the UCD (no
>    matter how well-established they appear to be
>    <https://emojipedia.org/apple-logo>), due to the
>    conflict-of-interest regarding trademarks and brand representation.
>    Hence why a more "diplomatic" name is suggested here, which
>    relegates the exact appearance of \(bs to a font-level concern.

It didn't have a stable meaning even within AT&T troff.  DWB troff, for
instance, rebranded `\(bs` as a name for the backslash glyph--what GNU
troff calls `\(rs`.[1]  Didn't help that Bell changed its logo after
1976 and would change it again when the Labs was sold to Lucent.  But
before that could happen, they killed the DWB product altogether.[2]

Regards,
Branden

[1] https://github.com/n-t-roff/DWB3.3/blob/master/postscript/devpost/R
[2] https://lists.gnu.org/archive/html/groff/2022-12/msg00097.html

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