bug#4136: 23.1; delete-pair

[Juri Linkov]

>> If it's really impossible to delete a pair in text-mode, then better
>> to signal an error.
>
> OK; I've reapplied the patch and fixed the test, and I'm now re-closing
> this bug report.

Thanks.  Every time I delete a pair of quotes in a long string,
or a pair of parens in a long sexp, it makes me feel uneasy since
I worry whether it deleted the intended characters or not.

How about using the same delay blink-matching-delay that is used
after showing a matching paren, but in this case to show
a character at the other end of the pair with a delay
before deleting it?

This is achievable with this patch:

diff --git a/lisp/emacs-lisp/lisp.el b/lisp/emacs-lisp/lisp.el
index ac4ba78897..88e1b26af3 100644
--- a/lisp/emacs-lisp/lisp.el
+++ b/lisp/emacs-lisp/lisp.el
@@ -752,6 +752,8 @@ delete-pair
                                      (if (= (length p) 3) (cdr p) p))
                                    insert-pair-alist))
              (error "Not after matching pair"))
+           (when blink-matching-paren
+             (sit-for blink-matching-delay))
            (delete-char 1)))
        (delete-char -1))
     (save-excursion
@@ -764,6 +766,8 @@ delete-pair
                                    (if (= (length p) 3) (cdr p) p))
                                  insert-pair-alist))
            (error "Not before matching pair"))
+         (when blink-matching-paren
+           (sit-for blink-matching-delay))
          (delete-char -1)))
       (delete-char 1))))