bug#55692: 29.0.50; delete-selection-mode: Replace region only if set using the mouse

[Visuwesh <visuweshm@gmail.com>]

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Tags: patch

Motivation: I often find myself annoyed by `delete-selection-mode' when
using the keyboard since the region in Emacs does not translate to text
selections in other applications.  On the contrary, I find myself
wanting the behaviour of `delete-selection-mode' for regions set using
the mouse.  Attached patch adds an user option to do that.


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From 3db630457b46bb25514a8041eeb80f35e73ef40c Mon Sep 17 00:00:00 2001
From: Visuwesh <visuweshm@gmail.com>
Date: Sat, 28 May 2022 22:52:19 +0530
Subject: [PATCH] delete-selection-mode: Add user option to delete mouse
 regions only

* lisp/delsel.el (delete-selection-mouse-selection-only): Add new user option.
(delete-selection-pre-hook): Respect it.
* etc/NEWS: Announce the new user option.
---
 etc/NEWS       | 4 ++++
 lisp/delsel.el | 9 +++++++++
 2 files changed, 13 insertions(+)

diff --git a/etc/NEWS b/etc/NEWS
index 3065fa85d3..100be767b3 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -265,6 +265,10 @@ startup.  Previously, these functions ignored
 * Changes in Emacs 29.1
 
 +++
+** New user option 'delete-selection-mouse-selection-only'.
+When non-nil, 'delete-selection-mode' will only delete the active
+region if it was set using the mouse.
+
 ** New user option 'switch-to-prev-buffer-skip-regexp'.
 This should be a regexp or a list of regexps; buffers whose names
 match those regexps will be ignored by 'switch-to-prev-buffer' and
diff --git a/lisp/delsel.el b/lisp/delsel.el
index f5fe7cf793..a011be9ede 100644
--- a/lisp/delsel.el
+++ b/lisp/delsel.el
@@ -64,6 +64,12 @@ delete-selection-save-to-register
   "If non-nil, deleted region text is stored in this register.
 Value must be the register (key) to use.")
 
+(defcustom delete-selection-mouse-selection-only nil
+  "If non-nil, delete the region only if set using the mouse."
+  :version "29.1"
+  :group 'editing-basics
+  :type 'boolean)
+
 ;;;###autoload
 (defalias 'pending-delete-mode 'delete-selection-mode)
 
@@ -251,6 +257,9 @@ delete-selection-pre-hook
 have this property won't delete the selection.
 See `delete-selection-helper'."
   (when (and delete-selection-mode (use-region-p)
+             (if delete-selection-mouse-selection-only
+                 (mouse-region-match)
+               t)
 	     (not buffer-read-only))
     (delete-selection-helper (and (symbolp this-command)
                                   (get this-command 'delete-selection)))))
-- 
2.33.1