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

[Paul Eggert <eggert@cs.ucla.edu>]

Alan Mackenzie wrote:

> My setup couldn't display curly single quotes

Sure it could.  It displayed curved single quotes as curved single quotes.  Your 
objection was that your setup also displayed grave accent and apostrophe as 
curved single quotes (a style you happen to prefer), and you wanted your setup 
to display *different-shaped curves* for curved single quotes.  This will not be 
not a problem to the few ordinary Emacs users who happen to use a similar 
obsolescent environment; they'll merely see nicely curved single quotes and move on.

> none of them that I've
> seen so far have distinct glyphs for the curly quotes.

Again, distinct glyphs are not a requirement for ordinary Emacs users.  That 
being said, for Emacs developers such as yourself, the Lat15-Terminus16 font I 
mentioned earlier has distinct glyphs for curved quotes, as does 
Lat15-TerminusBold16.  You can find them archived at 
<http://bugs.gnu.org/20707>.  There are many other choices in this area.

> That easiness remains controversial.

It's certainly easier to read text quoted ‘like this’ than to read text quoted 
\`like this\'.

> To be useful, it would have to become the standard way of quoting
> symbols.

I doubt whether it'll be the standard.  It's uglier and more complicated than 
the alternative.  Its main advantage is that it's easier to type for users who 
want to type only ASCII.

> Where do you see any portability hassles?

Code might work when running on a typical Emacs system, but might fail on an 
Emacs system configured --without-curved-quotes, because Emacs will generate 
different strings that will be treated differently.

> What exactly do you mean by "display problems fixed"?

On the rare systems that don't display curved quotes as quotes, Emacs should 
display straight quotes as substitutes.  That's good enough for these rare and 
obsolescent systems.

> I don't think it's TRT simply to curlify any quote typed within a string

Electric Quote mode doesn't do that.  If you type an apostrophe, it normally 
leaves the apostrophe alone.  And in the rare cases where one really wants a 
grave accent and not a left single quote, it's easy enough to type C-q `.

> How about only curlifying when
> there's a matched pair of quotes containing exactly a symbol, and
> uncurlifying when that ceases to be the case?

That wouldn't work well; for example, it'd mishandle the common case of "`%s'". 
  Worse, it'd mean that Emacs couldn't curve the open quote until the user types 
the corresponding closed quote.  I experimented with several approaches along 
the lines you're suggesting, and they all had action-at-a-distance problems that 
made for confusing UIs.  It's much better if quotes are curved only when near 
the cursor, so users see them being curved.