GNU bug report logs - #49593
Emacs overrides normal-erase-is-backspace

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

From: "Paul W. Rankin" <pwr <at> bydasein.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Emacs overrides normal-erase-is-backspace
Date: Fri, 16 Jul 2021 16:57:49 +1000

Overview:

Emacs overrides user's customization of normal-erase-is-backspace with 
no clear way to set it.

Steps to reproduce:

1. insert into start.el:

    (custom-set-variables '(normal-erase-is-backspace t))

2. emacs -Q -l start.el

3. M-x customize-option RET normal-erase-is-backspace

Expected behaviour:

normal-erase-is-backspace is t.

Actual behaviour:

normal-erase-is-backspace is maybe; marked as "CHANGED outside of 
Customize"

Message #8 received at 49593 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Paul W. Rankin" <pwr <at> bydasein.com>
Cc: 49593 <at> debbugs.gnu.org
Subject: Re: bug#49593: Emacs overrides normal-erase-is-backspace
Date: Fri, 16 Jul 2021 12:04:42 +0200

"Paul W. Rankin" <pwr <at> bydasein.com> writes:

> normal-erase-is-backspace is maybe; marked as "CHANGED outside of
> Customize"

The doc string does say:

Setting this variable with setq doesn't take effect.  Programmatically,
call `normal-erase-is-backspace-mode' (which see) instead.

But setting it with `custom-set-variables' should work, I'd have
thought?  Hm...

(custom-set-variables '(normal-erase-is-backspace t))

sets it to `maybe', so it's not a startup problem (there's been some
with Customize)...

Hm, looking at the code to `normal-erase-is-backspace-mode', I don't see
how that's supposed to work at all.  The value is only used in
`normal-erase-is-backspace-setup-frame', and calling
`normal-erase-is-backspace-mode' doesn't actually change the value of
the variable, which explains why `custom-set-variables' does nothing.

The following change seems to fix the issue:

diff --git a/lisp/simple.el b/lisp/simple.el
index 322693f631..01851e0a0a 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -9505,9 +9505,9 @@ normal-erase-is-backspace
   :set (lambda (symbol value)
 	 ;; The fboundp is because of a problem with :set when
 	 ;; dumping Emacs.  It doesn't really matter.
-	 (if (fboundp 'normal-erase-is-backspace-mode)
-	     (normal-erase-is-backspace-mode (or value 0))
-	   (set-default symbol value))))
+	 (when (fboundp 'normal-erase-is-backspace-mode)
+	   (normal-erase-is-backspace-mode (or value 0)))
+	 (set-default symbol value)))
 
 (defun normal-erase-is-backspace-setup-frame (&optional frame)
   "Set up `normal-erase-is-backspace-mode' on FRAME, if necessary."



But is that the correct fix?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #15 received at 49593 <at> debbugs.gnu.org (full text, mbox):

From: "Paul W. Rankin" <pwr <at> bydasein.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 49593 <at> debbugs.gnu.org
Subject: Re: bug#49593: Emacs overrides normal-erase-is-backspace
Date: Sun, 18 Jul 2021 15:01:39 +1000

Hi Lars,

Thanks for looking into this. Yes after reading through the code of this 
my opinion is that it would be better scrapped and rewritten from 
scratch. (For me the patch did not fix the option persisting after 
restarting Emacs.)

I've managed to resolve my problem via the console itself so I'd rather 
not touch it, but might be worthwhile keeping the issue open if anyone 
else requires the mode/variable.


On 2021-07-16 20:04, Lars Ingebrigtsen wrote:
> 
> Hm, looking at the code to `normal-erase-is-backspace-mode', I don't 
> see
> how that's supposed to work at all.  The value is only used in
> `normal-erase-is-backspace-setup-frame', and calling
> `normal-erase-is-backspace-mode' doesn't actually change the value of
> the variable, which explains why `custom-set-variables' does nothing.

Message #18 received at 49593 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Paul W. Rankin" <pwr <at> bydasein.com>
Cc: 49593 <at> debbugs.gnu.org
Subject: Re: bug#49593: Emacs overrides normal-erase-is-backspace
Date: Sun, 18 Jul 2021 14:08:32 +0200

[Message part 1 (text/plain, inline)]

"Paul W. Rankin" <pwr <at> bydasein.com> writes:

> Thanks for looking into this. Yes after reading through the code of
> this my opinion is that it would be better scrapped and rewritten from
> scratch. (For me the patch did not fix the option persisting after
> restarting Emacs.)

Hm, odd.  I tried your recipe with the patch, and

[Message part 2 (image/png, inline)]

[Message part 3 (text/plain, inline)]

instead of the "changed outside" message you were getting...

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #21 received at 49593 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Paul W. Rankin" <pwr <at> bydasein.com>
Cc: 49593 <at> debbugs.gnu.org
Subject: Re: bug#49593: Emacs overrides normal-erase-is-backspace
Date: Sat, 24 Jul 2021 18:23:42 +0200

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> Hm, odd.  I tried your recipe with the patch, and
>
>
>
> instead of the "changed outside" message you were getting...

I've now pushed the patch, because it seems like the right thing,
anyway.

If you're still seeing the problem (after this update), do you have a
recipe to reproduce it, starting from "emacs -Q"?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #24 received at 49593 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Paul W. Rankin" <pwr <at> bydasein.com>
Cc: 49593 <at> debbugs.gnu.org
Subject: Re: bug#49593: Emacs overrides normal-erase-is-backspace
Date: Sun, 22 Aug 2021 18:03:08 +0200

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

>> instead of the "changed outside" message you were getting...
>
> I've now pushed the patch, because it seems like the right thing,
> anyway.
>
> If you're still seeing the problem (after this update), do you have a
> recipe to reproduce it, starting from "emacs -Q"?

More information was requested, but no response was given within a
month, and since I'm not able to reproduce the problem, I'm closing this
bug report.  If the problem still exists, please respond to this email
and we'll reopen the bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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