Highlight matching quotes

Question

Is it possible to highlight matching quotes as show-paren-mode does with parentheses? The characters I'm looking to highlight are "dumb" quotes, both single (Unicode: apostrophe, U+0027) and double (Unicode: quotation mark, U+0022).

Sometimes I get lost in Fortran format specifiers, like '("strg1", i2, "strg2", i11)'. Highlighting matching quotes there would help me tell apart the pieces of the specifier.

I'd prefer not to use smartparens. If your solution uses it please provide a set-up that just highlights matching quotes without otherwise altering the pairing or highlighting of matching delimiters.

Answer 1

Of course it is.

(defun show-paren--match-quotes ()
  (let ((ppss (syntax-ppss)))
    ;; In order to distinguish which quote is opening and which is starting,
    ;; check that that point is not within a string (or comment, for that
    ;; matter).  Also ignore escaped quotes.
    (unless (or (nth 8 ppss) (nth 5 ppss))
      (or
       (and (not (bobp))
            (eq 7 (car-safe (syntax-after (1- (point)))))
            (save-excursion
              (let ((end (point))
                    (ppss (syntax-ppss (1- (point)))))
                (when (nth 3 ppss)
                  (let ((beg (nth 8 ppss)))
                    (list beg
                          (1+ beg)
                          (1- end)
                          end))))))
       (and (not (eobp))
            (eq 7 (car-safe (syntax-after (point))))
            (save-excursion
              (let ((beg (point)))
                (condition-case nil
                    (progn
                      (forward-sexp 1)
                      (list beg
                            (1+ beg)
                            (1- (point))
                            (point)))))))))))

(advice-add 'show-paren--default :after-until #'show-paren--match-quotes)