Re: text-quoting-style

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

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Alan Mackenzie wrote:
>> It's what Emacs does now, and it works well enough.  And the basic idea
>> >isn't a new principle: Emacs has done it for decades for many ASCII
>> >characters, e.g., HT.  So it is not a problem in practice.
> It will be a problem in practice.  It will by lying about what character
> in the buffer the glyph on the screen represents.

Again, there's nothing new here: Emacs has been "lying" in that way for decades 
for HT and for several other ASCII characters, and it works in practice.

>   It will be ambiguous:

That's easily enough fixed.  I installed the attached patch, which uses shadow 
glyphs for quote substitutions in ASCII-only displays.  If you prefer underline 
or some other glyph face on your console please feel free to change the code.

>> text-quoting-style doesn't do anything for info files, or
>> for other text files containing curved quotes.
>
> That's an argument for an additional facility for Info

The additional facility I proposed would work for info, and would also work for 
*Help* buffers and diagnostics and would render text-quoting-style unnecessary.

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From 1a3518e7c361a9ceaa017c1334a83d14e0651a4e Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 1 Sep 2015 09:18:12 -0700
Subject: [PATCH] Display replacement quotes with shadow glyphs

* lisp/startup.el (command-line): When displaying ASCII
replacements for curved quotes, use a shadow glyph instead of a
regular one, to avoid ambiguity.
---
 lisp/startup.el | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lisp/startup.el b/lisp/startup.el
index 8c63ed2..3e29739 100644
--- a/lisp/startup.el
+++ b/lisp/startup.el
@@ -1018,11 +1018,12 @@ please check its value")
     (setq no-blinking-cursor t))
 
   ;; If curved quotes don't work, display ASCII approximations.
-  (dolist (char-repl '((?‘ . [?\`]) (?’ . [?\']) (?“ . [?\"]) (?” . [?\"])))
+  (dolist (char-repl '((?‘ . ?\`) (?’ . ?\') (?“ . ?\") (?” . ?\")))
     (when (not (char-displayable-p (car char-repl)))
       (or standard-display-table
           (setq standard-display-table (make-display-table)))
-      (aset standard-display-table (car char-repl) (cdr char-repl))))
+      (aset standard-display-table (car char-repl)
+            (vector (make-glyph-code (cdr char-repl) 'shadow)))))
   (setq internal--text-quoting-flag t)
 
   ;; Re-evaluate predefined variables whose initial value depends on
-- 
2.1.4