GNU bug report logs - #64121
28.2; C-SPC not working in term char mode

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

From: Al Petrofsky <al <at> petrofsky.org>
To: bug-gnu-emacs <at> gnu.org
Subject: 28.2; C-SPC not working in term char mode
Date: Fri, 16 Jun 2023 20:06:57 -0400

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

   emacs-28.2 -Q
   M-x term RET RET
   C-SPC

This should send an ASCII NUL (a zero byte) to the pty, but instead it
displays "Mark set" in the echo area.

To fix it, C-SPC needs to get special handling akin to the handling of
C-/.  Here's a patch that also makes C-M-SPC and C-M-/ work.

--- term.el 2022-09-06 17:31:54.000000000 -0400
+++ term-c-spc-fixed.el 2023-06-15 11:21:41.780140053 -0400
@@ -916,6 +916,9 @@
     (define-key map [next] 'term-send-next)
     (define-key map [xterm-paste] #'term--xterm-paste)
     (define-key map [?\C-/] #'term-send-C-_)
+    (define-key map [?\C- ] #'term-send-C-@)
+    (define-key map [?\C-\M-/] #'term-send-C-M-_)
+    (define-key map [?\C-\M- ] #'term-send-C-M-@)
     map)
   "Keyboard map for sending characters directly to the inferior process.")

@@ -1359,6 +1362,9 @@
 (defun term-send-del   () (interactive) (term-send-raw-string "\e[3~"))
 (defun term-send-backspace  () (interactive) (term-send-raw-string "\C-?"))
 (defun term-send-C-_  () (interactive) (term-send-raw-string "\C-_"))
+(defun term-send-C-@  () (interactive) (term-send-raw-string "\C-@"))
+(defun term-send-C-M-_  () (interactive) (term-send-raw-string "\e\C-_"))
+(defun term-send-C-M-@  () (interactive) (term-send-raw-string "\e\C-@"))

 (defun term-char-mode ()
   "Switch to char (\"raw\") sub-mode of term mode.

[Message part 2 (text/html, inline)]

Message #8 received at 64121 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Al Petrofsky <al <at> petrofsky.org>
Cc: 64121 <at> debbugs.gnu.org
Subject: Re: bug#64121: 28.2; C-SPC not working in term char mode
Date: Sat, 17 Jun 2023 09:12:25 +0300

> From: Al Petrofsky <al <at> petrofsky.org>
> Date: Fri, 16 Jun 2023 20:06:57 -0400
> 
>    emacs-28.2 -Q
>    M-x term RET RET
>    C-SPC
> 
> This should send an ASCII NUL (a zero byte) to the pty, but instead it
> displays "Mark set" in the echo area.

I cannot reproduce this here: I don't see "Mark set" in the echo area.

Maybe this somehow depends on the terminal emulator?  (I use PuTTY.)

How to verify that the null character is sent to the pty?

Message #11 received at 64121 <at> debbugs.gnu.org (full text, mbox):

From: Al Petrofsky <al <at> petrofsky.org>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 64121 <at> debbugs.gnu.org
Subject: Re: bug#64121: 28.2; C-SPC not working in term char mode
Date: Sat, 17 Jun 2023 02:26:40 -0400

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

On Sat, Jun 17, 2023 at 2:12 AM Eli Zaretskii <eliz <at> gnu.org> wrote:

> > From: Al Petrofsky <al <at> petrofsky.org>
> > Date: Fri, 16 Jun 2023 20:06:57 -0400
> >
> >    emacs-28.2 -Q
> >    M-x term RET RET
> >    C-SPC
> >
> > This should send an ASCII NUL (a zero byte) to the pty, but instead it
> > displays "Mark set" in the echo area.
>
> I cannot reproduce this here: I don't see "Mark set" in the echo area.
>
> Maybe this somehow depends on the terminal emulator?  (I use PuTTY.)
>

I should have mentioned this bug won't show up if emacs is running in a
tty. The bug
stems from the subtle difference between C-SPC and C-@ input events on
graphical
terminals.  On a tty, C-SPC and C-@ become the same thing before they get
to emacs.


> How to verify that the null character is sent to the pty?
>

You can start an emacs -nw inside the term. Then pressing C-SPC should
result in a "Mark set" in the inner emacs's echo area.

[Message part 2 (text/html, inline)]

Message #14 received at 64121 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Al Petrofsky <al <at> petrofsky.org>
Cc: 64121 <at> debbugs.gnu.org
Subject: Re: bug#64121: 28.2; C-SPC not working in term char mode
Date: Sat, 17 Jun 2023 09:40:05 +0300

> From: Al Petrofsky <al <at> petrofsky.org>
> Date: Sat, 17 Jun 2023 02:26:40 -0400
> Cc: 64121 <at> debbugs.gnu.org
> 
> On Sat, Jun 17, 2023 at 2:12 AM Eli Zaretskii <eliz <at> gnu.org> wrote:
> 
>  > From: Al Petrofsky <al <at> petrofsky.org>
>  > Date: Fri, 16 Jun 2023 20:06:57 -0400
>  >
>  >    emacs-28.2 -Q
>  >    M-x term RET RET
>  >    C-SPC
>  >
>  > This should send an ASCII NUL (a zero byte) to the pty, but instead it
>  > displays "Mark set" in the echo area.
> 
>  I cannot reproduce this here: I don't see "Mark set" in the echo area.
> 
>  Maybe this somehow depends on the terminal emulator?  (I use PuTTY.)
> 
> I should have mentioned this bug won't show up if emacs is running in a tty. The bug
> stems from the subtle difference between C-SPC and C-@ input events on graphical
> terminals.  On a tty, C-SPC and C-@ become the same thing before they get to emacs.

Then I'm afraid I cannot evaluate this bug and its proposed solution,
as I don't have access to a platform where I can run a GUI Emacs with
"M-x term" still supported.

Could someone else please reproduce this and review the proposed
changes?  TIA.

Message #17 received at 64121 <at> debbugs.gnu.org (full text, mbox):

From: Gregory Heytings <gregory <at> heytings.org>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: Al Petrofsky <al <at> petrofsky.org>, 64121 <at> debbugs.gnu.org
Subject: Re: bug#64121: 28.2; C-SPC not working in term char mode
Date: Sat, 17 Jun 2023 07:08:25 +0000

>
> Could someone else please reproduce this and review the proposed 
> changes?  TIA.
>

I can reproduce this (with Emacs 29), and the proposed changes LGTM.

Message #22 received at 64121-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Gregory Heytings <gregory <at> heytings.org>
Cc: al <at> petrofsky.org, 64121-done <at> debbugs.gnu.org
Subject: Re: bug#64121: 28.2; C-SPC not working in term char mode
Date: Sun, 18 Jun 2023 09:34:59 +0300

> Date: Sat, 17 Jun 2023 07:08:25 +0000
> From: Gregory Heytings <gregory <at> heytings.org>
> cc: Al Petrofsky <al <at> petrofsky.org>, 64121 <at> debbugs.gnu.org
> 
> > Could someone else please reproduce this and review the proposed 
> > changes?  TIA.
> 
> I can reproduce this (with Emacs 29), and the proposed changes LGTM.

Thanks, installed on the master branch, and closing the bug.

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