bug#20707: [PROPOSED PATCH] Use curved quoting in C-generated errors

[Alan Mackenzie <acm@muc.de>]

Hello, Paul.

On Sat, Jun 06, 2015 at 11:11:25AM -0700, Paul Eggert wrote:
> Alan Mackenzie wrote:

[ .... ]

> > Linux consoles are not rare

> Well, that depends on one's definition of "rare" :-), ...

If you were to regard the Linux console as too rare to be worth
supporting, you'd effectively be saying that Emacs was now only supported
within GUIs.

> ... but even assuming they're common, curved quotes work on Linux
> consoles, either by default (as on Fedora) or by configuration (needed
> on Arch).  All we need to do is to set you up.

No.  You need to make sure that _everybody_ on a non-unicode terminal is
set up.  After all, you are making a drastic change to the software.  Up
till now, all messages output have been ASCII (with the exception of user
supplied characters and in some other rare instances such as outputting
`sentence-end').  You are now changing the character set to UTF-8.  At
the very least, this warrants an extensive entry in NEWS.

> > On the Linux console, there are a maximum of 256 glyphs which can be
> > displayed

> That's not a problem: we're only talking about two glyphs. and you
> undoubtedly have two to spare (what are you using? CP437? I'll bet you
> never use its U+263B BLACK SMILING FACE ...).

I'm using lat1-16.  Somehow, I'm sure I can find four (not two - there's
the curly double quotes, too) glyphs to sacrifice.

>  > the two varieties of quotes are mapped
> > to the same glyphs in my consolefont.

> I assume this is because you're running bleeding-edge Emacs and have told it 
> that you're in an 8-bit environment that can't display curved quotes.

No.  My environment is set up as UTF-8.  It's lat1-16 that maps the two
characters to the same glyph, something I wasn't aware of until the last
few days.

> This is what commit 496bfe74990d6601d3584cb900643aa77d7b7a78 was about
> (Bug#20545).  The idea is that ordinary users in obsolescent locales
> will just see straight apostrophes instead of curved quotes, which is
> good enough for them.

I don't have a straight apostrophe.  :-)  I haven't looked at that change
in any detail, but I have a question: does the code test the output
display setup to decide what sort of quotes to output (best), or is it up
to some user option (middling) or is it hard coded (worst)?

> But you're not an ordinary user: you're a developer, and would prefer
> to see the the various kinds of quotes when you're writing error
> messages and the like.  So it'd be nice to get that to work for you.

I've an idea that Richard uses a Linux terminal, too, but I'm not sure.

> > But it will not work well on a console, even with the most recent Emacs.

> Sure it will.  It works fine.  I just tried it on my Linux console
> (Ubuntu 15.04).  All you have to do is configure your fonts.  This is
> not too much to ask of an Emacs developer.

Of course not, but could it be too much to ask of an Emacs user?

> We should not have to contort Emacs source code merely to make it fit
> into the character set of a circa-1981 IBM PC.

> So how about trying a font that works?  You're running Arch Linux, ....

Gentoo, actually, and just to pre-empt RMS, we should say GNU/Linux.  ;-)

> .... and an 8-year-old post in the Arch Linux forums
> <https://bbs.archlinux.org/viewtopic.php?id=121633#p954383> says that
> the Debian Lat15-Terminus16 works and looks nice on Arch Linux.  I just
> tried this font on Ubuntu 15.04 and it worked for me too, and displayed
> curved quotes well.  Please give it a try.  You can use the attached
> file (a copy of Ubuntu 15.04
> /usr/share/consolefonts/Lat15-Terminus16.psf.gz), and check out its
> curved quotes.

I don't think that's the font for me.  It has one-pixel thick spidery
characters, rather than the two-pixel thick ones the default fonts have.
I find its @ difficult to make out, and perhaps most critically, there
isn't a big enough difference between ( and { or between ) and }.  Its
apostrophe is a vertical line rather than a top right to bottom left
sloping character, and I find its curly single quotes too indistinct,
each of them being a mere 3 pixels.  Perhaps most seriously, it's missing
an ffdf "character not found" character.  Other than that, it's not too
bad.

It at least gives another idea of which characters are worth including in
the 256 character list.

-- 
Alan Mackenzie (Nuremberg, Germany).