Electric quotes: Improve support for Markdown mode (Bug#24709)

Introduce a new user option 'electric-quote-context-sensitive'.  If
non-nil, have ' insert an opening quote if sensible.

Also introduce a new variable 'electric-quote-code-faces'.  Major
modes such as 'markdown-mode' can add faces to this list to treat text
as inline code and disable electric quoting.

* lisp/electric.el (electric-quote-context-sensitive): New user
option.
(electric-quote-code-faces): New variable.
(electric-quote-post-self-insert-function): Treat ' as ` if
desired and applicable; disable electric quoting for given faces.

* test/lisp/electric-tests.el (electric-quote-opening-single)
(electric-quote-closing-single, electric-quote-opening-double)
(electric-quote-closing-double)
(electric-quote-context-sensitive-backtick)
(electric-quote-context-sensitive-bob-single)
(electric-quote-context-sensitive-bob-double)
(electric-quote-context-sensitive-bol-single)
(electric-quote-context-sensitive-bol-double)
(electric-quote-context-sensitive-after-space-single)
(electric-quote-context-sensitive-after-space-double)
(electric-quote-context-sensitive-after-letter-single)
(electric-quote-context-sensitive-after-letter-double)
(electric-quote-context-sensitive-after-paren-single)
(electric-quote-context-sensitive-after-paren-double)
(electric-quote-markdown-in-text)
(electric-quote-markdown-in-code): New unit tests.

1 files changed, 16 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index b9a492cb5ce..3f6811198d1 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -129,6 +129,22 @@ given file is on a case-insensitive filesystem.
 of curved quotes for 'electric-quote-mode', allowing user to choose
 the types of quotes to be used.
 
+** The new user option 'electric-quote-context-sensitive' makes
+'electric-quote-mode' context sensitive.  If it is non-nil, you can
+type an ASCII apostrophe to insert an opening or closing quote,
+depending on context.  Emacs will replace the apostrophe by an opening
+quote character at the beginning of the buffer, the beginning of a
+line, after a whitespace character, and after an opening parenthesis;
+and it will replace the apostrophe by a closing quote character in all
+other cases.
+
+** The new variable 'electric-quote-code-faces' controls when to
+disable electric quoting in text modes.  Major modes can add faces to
+this list; Emacs will temporarily disable 'electric-quote-mode'
+whenever point is before a character having such a face.  This is
+intended for major modes that derive from 'text-mode' but allow inline
+code segments, such as 'markdown-mode'.
+
 +++
 ** The new user variable 'dired-omit-case-fold' allows the user to
 customize the case-sensitivity of dired-omit-mode.  It defaults to