Hi Branden,
All of the terminal output devices groff supports lack overstriking support.
Whoops. I forgot that what I was seeing in less(1) was actually duped using
an underline effect. On that note, am I right to assume that \fI+\fP0 is
equally implausible by virtue of terminals diverging wildly in their
italicisation support? (Underlining, obliquity, ignoring the effect
outright, etc).
The enthusiastic aficionados of the Western Electric/Teletype Corporation
> Model 37, including (it would seem) many less(1) users, could then run wild
> with TERM=tty37.
That reminds me (and I'm being dead serious here), if anybody knows where a
Model 37 can be acquired in 2024, *please* let me know. (I spent all arvo
yesterday searching… seriously).
A new conditional expression operator, "T", would take a delimited argument
> naming an output device capability.
Why stop there? Such a conditional could match against a named field (and
optional value) in an output driver description (DESC) file, whether it's
recognised by Groff or not. Something like:
.if T unicode \{
.if T res > 50 \{
I mean, if we're gonna extend the syntax to include something this niche,
we may as well go all the way.
Regards,
— John
On Fri, 9 Aug 2024 at 16:19, G. Branden Robinson <
g.branden.robin...@gmail.com> wrote:
> Hi John,
>
> At 2024-08-09T15:53:30+1000, John Gardner wrote:
> > Hi Vincent,
>
> Not to horn in, but I think I'm better situated to venture opinions or
> background on implementation decisions taken in groff than Vincent is.
>
> > So ideally, the fallback for "±0" should be "+0 or -0", which is
> > > much more readable and less ambiguous than "+-0" or "+/-0".
> >
> > For approximating ± in ASCII, is there some reason \z_+0 hasn't been
> > considered?
>
> You anticipated the answer.
>
> > I'm asking earnestly, as I'm primed to assume overstriking hacks have
> > already been ruled out (pun intended) as a fallback.
>
> \z _is_ an overstriking hack.
>
> From groff's Texinfo manual (slightly altered):
>
> -- Escape sequence: \o'abc...'
> Overstrike the glyphs of characters A, B, C, ...; the glyphs are
> centered, written, and the drawing position advanced by the widest
> of the glyphs.
>
> -- Escape sequence: \zc
> Format the character C with zero width; that is, without advancing
> the drawing position. Use '\z' to overstrike glyphs aligned to
> their left edges, in contrast to '\o''s centering.
>
> All of the terminal output devices groff supports lack overstriking
> support.
>
> Resolving <https://savannah.gnu.org/bugs/?63583> (waiting on me) is a
> prerequisite to doing anything about that.
>
> We would also need a new "DESC" file keyword to declare overstriking
> support in output devices, and a way to query this parameter from the
> GNU troff language.[1] (This would also be useful for Tektronix 4014
> support.)
>
> The enthusiastic aficionados of the Western Electric/Teletype
> Corporation Model 37, including (it would seem) many less(1) users,
> could then run wild with TERM=tty37.
>
> tty37|model 37 teletype,
> OTbs, hc, os, xon,
> bel=^G, cr=\r, cub1=^H, cud1=\n, cuu1=\E7, hd=\E9, hu=\E8,
> ind=\n,
>
> I'm open to correction by Vincent or anyone else. :)
>
> Regards,
> Branden
>
> [1] Straw man:
>
> A. A new keyword "overstrike" or "has-overstriking" would be
> recognized by libdriver and/or libgroff. (In practice, only
> grotty(1) would need to bother checking for it; any driver for a
> typesetter can assume that overstriking is possible.)
>
> B. A new conditional expression operator, "T", would take a
> delimited argument naming an output device capability.
>
> So you might have something like this:
>
> .ie T'has-overstriking' .fchar \[+-] \o'_+'
> .el .fchar \[+-] +/\-
>
> The feature window for groff 1.24 is closing (maybe in a month?), though
> I still want to get #63583 landed before freezing the formatter, even
> though it's strictly just an output driver change, on the off chance
> that I _have_ to change something in the formatter to support it, and
> because Lennart Jablonka has demonstrated the patience of a saint (as
> have Deri James and TANAKA Takuji_).
>
