bug#4136: 23.1; delete-pair

[Juri Linkov]

>> 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?
>
> Makes sense to me, but I'm not a regular user of delete-pair, so I don't
> know whether that'd be annoying or reassuring...

After a month of using it the following patch proved to be useful.
It adds anew new defcustom delete-pair-blink-delay based on the default
value of blink-matching-delay.  Exactly the same defcustom is also
added copy-region-blink-delay for the feature request in bug#42865
not to blink when copying a region:

diff --git a/lisp/emacs-lisp/lisp.el b/lisp/emacs-lisp/lisp.el
index 35590123ee..be2adfa848 100644
--- a/lisp/emacs-lisp/lisp.el
+++ b/lisp/emacs-lisp/lisp.el
@@ -784,9 +784,17 @@ insert-parentheses
   (interactive "P")
   (insert-pair arg ?\( ?\)))
 
+(defcustom delete-pair-blink-delay blink-matching-delay
+  "Time in seconds to delay after showing a pair character to delete.
+No timeout in case of 0."
+  :type 'number
+  :group 'lisp
+  :version "28.1")
+
 (defun delete-pair (&optional arg)
   "Delete a pair of characters enclosing ARG sexps that follow point.
-A negative ARG deletes a pair around the preceding ARG sexps instead."
+A negative ARG deletes a pair around the preceding ARG sexps instead.
+The option `delete-pair-blink-delay' can disable blinking."
   (interactive "P")
   (if arg
       (setq arg (prefix-numeric-value arg))
@@ -802,6 +810,9 @@ delete-pair
                                      (if (= (length p) 3) (cdr p) p))
                                    insert-pair-alist))
              (error "Not after matching pair"))
+           (when (and (natnump delete-pair-blink-delay)
+                      (> delete-pair-blink-delay 0))
+             (sit-for delete-pair-blink-delay))
            (delete-char 1)))
        (delete-char -1))
     (save-excursion
@@ -814,6 +825,9 @@ delete-pair
                                    (if (= (length p) 3) (cdr p) p))
                                  insert-pair-alist))
            (error "Not before matching pair"))
+         (when (and (natnump delete-pair-blink-delay)
+                    (> delete-pair-blink-delay 0))
+           (sit-for delete-pair-blink-delay))
          (delete-char -1)))
       (delete-char 1))))
 
diff --git a/lisp/simple.el b/lisp/simple.el
index e96c7c9a6e..3d18909f2c 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -5089,9 +5089,9 @@ kill-ring-save
 
 (defun indicate-copied-region (&optional message-len)
   "Indicate that the region text has been copied interactively.
-If the mark is visible in the selected window, blink the cursor
-between point and mark if there is currently no active region
-highlighting.
+If the mark is visible in the selected window, blink the cursor between
+point and mark if there is currently no active region highlighting.
+The option `copy-region-blink-delay' can disable blinking.
 
 If the mark lies outside the selected window, display an
 informative message containing a sample of the copied text.  The
@@ -5106,11 +5106,13 @@ indicate-copied-region
        ;; Swap point-and-mark quickly so as to show the region that
        ;; was selected.  Don't do it if the region is highlighted.
        (unless (and (region-active-p)
-                    (face-background 'region nil t))
+                    (face-background 'region nil t)
+                    (natnump copy-region-blink-delay)
+                    (> copy-region-blink-delay 0))
          ;; Swap point and mark.
          (set-marker (mark-marker) (point) (current-buffer))
          (goto-char mark)
-         (sit-for blink-matching-delay)
+         (sit-for copy-region-blink-delay)
          ;; Swap back.
          (set-marker (mark-marker) mark (current-buffer))
          (goto-char point)
@@ -8135,6 +8139,13 @@ blink-paren-post-self-insert-function
           ;; `sit-for'. That's also the reason it get a `priority' prop
           ;; of 100.
           'append)
+
+(defcustom copy-region-blink-delay blink-matching-delay
+  "Time in seconds to delay after showing a pair character to delete.
+No timeout in case of 0."
+  :type 'number
+  :group 'killing
+  :version "28.1")
 
 ;; This executes C-g typed while Emacs is waiting for a command.
 ;; Quitting out of a program does not go through here;