Re: character sets as they relate to “Raw” string literals for elisp

[Alan Mackenzie]

Hello, Eli.

On Sat, Oct 09, 2021 at 16:15:50 +0300, Eli Zaretskii wrote:
> > Date: Sat, 9 Oct 2021 13:08:35 +0000
> > Cc: emacs-devel@gnu.org, rms@gnu.org, juri@linkov.net, db48x@db48x.net,
> >   stefankangas@gmail.com, yuri.v.khan@gmail.com, monnier@iro.umontreal.ca
> > From: Alan Mackenzie <acm@muc.de>

> > > > --- (EM DASH) appears as an inverse question mark on my screen.  So do
> > > > several other punctuation marks, I think.

> > > That means the display-time replacement doesn't happen, I think.  What
> > > is your terminal-coding-system?

> > M-: default-terminal-coding-system says utf-8-unix.  I haven't set this
> > in my site-start.el or .emacs.

> That explains it, I think: info.el thinks your console can display
> those characters.

I vaguely remember looking into this before.  I think the problem was
that there was no facility in Linux for determining whether a particular
character could be displayed on its console.  The low level interface
simply wasn't there.

> > I have my font set to Latin-1.  More precisely,

> >     consolefont="lat1-16"

> > in my /etc/conf.d/consolefont.

> Are there any other possible values that will cause these characters
> display correctly?  Or is the Linux console unable to display them no
> matter what?

The Linux console is limited to 256 glyphs, some of which are used by two
or several Unicode characters.  It would be possible but time consuming
to amend the font to display the EM-DASH as, say, a minus sign.

> Regardless, we could have a customizable option in info.el to force
> display of the Unicode punctuation as their ASCII equivalents, even if
> the terminal seems capable of the Unicode display.

Again, this would only solve half of the problem, the display half, but
might be worthwhile.  I would prefer, though, to find a way of preventing
these awkward Unicode punctuation charaacters from being in info buffers
in the first place.

-- 
Alan Mackenzie (Nuremberg, Germany).