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

[Paul Eggert]

Alan Mackenzie wrote:

> , or even "Parsing `%qs': expected %s `%qs', got `%qs'.", where the q
> means "make the surrounding quote marks display marks".

I'd rather not go that route, as it's more complex to implement and to explain, 
and would mean that we'd have to figure out what happens when someone uses %q 
without surrounding grave accent, and so forth.  Even the unquoted %q would be 
bad enough: WYSIWYH says quotation marks are best represented by using, well, 
quotation marks.

> 8-bit environments may not be all that common any more, at least on a
> desktop machine, but what about over comms links?

I don't see why comms links are relevant.  What matters is what can be 
displayed.  In the old days somm comms links wouldn't transmit 8-bit data, only 
7-bit, but I assume that's not what you're talking about as that didn't support 
even 8-bit charsets.

> Linux consoles are not rare

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

> 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 ...).

> 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.  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.

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.

> 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.  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, 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.

Lat15-Terminus16.psf.gz
Description: application/gzip