GNU bug report logs - #75042
29.4; `backward-delete-char-untabify': active-region behavior

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Asher Copeland <ashercopeland <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 29.4; `backward-delete-char-untabify': active-region behavior
Date: Sun, 22 Dec 2024 17:52:04 -0800

The documentation of `backward-delete-char-untabify' indicates the
following:

 If Transient Mark mode is enabled, the mark is active, and ARG is 1,
 delete the text in the region and deactivate the mark instead.
 To disable this, set option `delete-active-region' to nil.

However, when `backward-delete-char-untabify-method' is set to hungry or
all and point has more than one whitespace character before it
(i.e. that `backward-delete-char-untabify' would delete more than one
character), `backward-delete-char-untabify' ignores the settings of
`transient-mark-mode' and `delete-active-region' and proceeds with its
normal action.

Practically, this means that, in a snippet of text such as the
following (assuming the spacing/newlines don't get messed up):

    line1
    line2
    line3

If point were placed before line2 and the region is active and nonempty,
with `backward-delete-char-untabify-method' set to hungry, the expected
behavior (and the behavior that is currently documented) would be that
the text highlighted by the region would be deleted and that the region
would be deactivated. What the function would instead do is delete the
spaces to the left of point and deactivate the region.

I have found this issue to occur running under `emacs -Q'.

For consistency with the current documentation and other deletion
commands, I believe that the behavior of `backward-delete-char-untabify'
should change to delete the text in the region, under the same
conditions that `backward-delete-char' would do the same.

Here is the last form of the definition of
`backward-delete-char-untabify', from simple.el:6522, for reference:

   (let* ((skip (cond ((eq backward-delete-char-untabify-method 'hungry) " \t")
                      ((eq backward-delete-char-untabify-method 'all)
                       " \t\n\r")))
          (n (if skip
                 (let* ((oldpt (point))
                        (wh (- oldpt (save-excursion
                                       (skip-chars-backward skip)
                                       (constrain-to-field nil oldpt)))))
                   (+ arg (if (zerop wh) 0 (1- wh))))
               arg)))
     ;; Avoid warning about delete-backward-char
     (with-no-warnings (delete-backward-char n killp))))

The issue seems to stem from the last line. In the described conditions,
the symbol `n' would be bound to a value greater than 1. Therefore,
`delete-backward-char' would delete n characters and deactivate the
region, instead of deleting the region.

--
Asher


In GNU Emacs 29.4 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.18.0, Xaw scroll bars) of 2024-10-16 built on asher-v-ubuntu
System Description: Ubuntu 24.04.1 LTS

Configured using:
 'configure --with-x-toolkit=lucid --prefix=/opt/emacs'

Configured features:
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XPM LUCID ZLIB

Important settings:
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Major mode: Fundamental

Minor modes in effect:
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Memory information:
((conses 16 38095 7179)
 (symbols 48 5293 1)
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 (string-bytes 1 379725)
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