GNU bug report logs - #13255
24.2.50; output in nonvisible shell buffer changes prompt

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

From: Richard Stallman <rms <at> gnu.org>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.2.50; output in nonvisible shell buffer changes prompt
Date: Sat, 22 Dec 2012 17:45:00 -0500

I have a shell buffer with a program sending lots of output.
That buffer is not currently displayed.  I type C-h, and it prompts.
So far, so good.

The bug is that the prompt changes repeatedly.  A space gets added at
the beginning and the hyphen disappears at the end.  Then the space
disappears and the hyphen reappears.  This oscillation continues
indefinitely at the rate of 3 or 4 changes per second.



In GNU Emacs 24.2.50.1 (mips64el-unknown-linux-gnu, GTK+ Version 2.12.12)
 of 2012-10-20 on chiefs-gnewsense
Bzr revision: 110610 rgm <at> gnu.org-20121021013546-97l6862aw3mmsbd4
System Description:	gNewSense mipsel-l

Configured using:
 `configure 'CFLAGS=-O0 -g' '--with-gif=no' '--with-tiff=no''

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: RMAIL

Minor modes in effect:
  diff-auto-refine-mode: t
  shell-dirtrack-mode: t
  gpm-mouse-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Recent input:
o g r a m s SPC s u c h SPC a s SPC s i c DEL DEL o 
c i a l SPC s e c u r i t y , SPC c u t s SPC t h a 
t ESC d ESC q C-p C-p C-p C-p ESC ^ ESC b ESC b ESC 
b ESC b i m a g i n a r y SPC ESC f ESC f C-f C-b C-k 
C-n C-n C-a C-n C-n i s SPC ESC q C-n C-e SPC SPC O 
b a m a SPC i s SPC a SPC c e n t e r - r i g h t RET 
p o l i t i c i a n SPC t h a t SPC f a v o r s SPC 
ESC DEL ESC DEL a n d SPC f a v o r s SPC s u c h SPC 
c u t s ; SPC i f SPC h e SPC d i d n ' t , SPC h e 
SPC w o u l d SPC n o t SPC g o SPC a l o n g RET w 
i t h SPC t h e SPC p r e t e n s e . C-c C-c C-d x 
C-d C-d x C-d x C-x C-s C-x b * s c TAB DEL ESC DEL 
s h TAB RET C-x b RET SPC SPC ESC v SPC SPC C-d C-d 
C-d C-d x C-x C-s n SPC C-d C-d C-d SPC SPC C-d C-d 
x C-x C-s C-x b RET C-x b RET C-h C-h ESC x r e p o 
r t SPC e m a c s SPC b u g RET

Recent messages:
Saving file /home/rms/RMAIL...
Wrote /home/rms/RMAIL [2 times]
Expunging deleted messages...done
Saving file /home/rms/RMAIL...
Wrote /home/rms/RMAIL [2 times]
No following nondeleted message
Expunging deleted messages...done
Saving file /home/rms/RMAIL...
Wrote /home/rms/RMAIL [2 times]
Quit
Quit

Load-path shadows:
None found.

Features:
(pcmpl-unix two-column debug unrmail diff ispell mail-extr shadow
emacsbug cc-langs cl cl-lib cc-mode cc-fonts cc-guess cc-menus cc-cmds
cc-styles cc-align cc-engine cc-vars cc-defs bug-reference apropos
time-stamp vc-arch vc-mtn vc-hg vc-git vc-sccs vc-svn vc-rcs utf-7
ind-util vc-bzr texinfo etags rmailsum jka-compr diff-mode log-edit
easy-mmode pcvs-util add-log vc vc-dispatcher parse-time vc-cvs
sgml-mode epa-mail epa derived epg epg-config shell pcomplete grep
compile comint ansi-color ring dired-aux novice quail help-mode
rmailout dabbrev misearch multi-isearch mule-util cal-move cal-menu
calendar cal-loaddefs qp mailalias rmailmm message sendmail
format-spec rfc822 mml easymenu mml-sec mm-decode mm-bodies mm-encode
mailabbrev gmm-utils mailheader mail-parse rfc2231 dired t-mouse
time-date rmailedit rmail rfc2047 rfc2045 ietf-drums mm-util
mail-prsvr mail-utils paren cus-start cus-load advice help-fns
advice-preload tooltip ediff-hook vc-hooks lisp-float-type mwheel
x-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list newcomment lisp-mode register page menu-bar rfn-eshadow
timer select scroll-bar mouse jit-lock font-lock syntax facemenu
font-core frame cham georgian utf-8-lang misc-lang vietnamese tibetan
thai tai-viet lao korean japanese hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese case-table epa-hook
jka-cmpr-hook help simple abbrev minibuffer loaddefs button faces
cus-face macroexp files text-properties overlay sha1 md5 base64 format
env code-pages mule custom widget hashtable-print-readable backquote
make-network-process dbusbind dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

-- 
Dr Richard Stallman
President, Free Software Foundation
51 Franklin St
Boston MA 02110
USA
www.fsf.org  www.gnu.org
Skype: No way! That's nonfree (freedom-denying) software.
  Use Ekiga or an ordinary phone call

Message #8 received at 13255 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: rms <at> gnu.org
Cc: 13255 <at> debbugs.gnu.org
Subject: Re: bug#13255: 24.2.50;
	output in nonvisible shell buffer changes prompt
Date: Sat, 22 Dec 2012 22:33:29 -0500

Richard Stallman wrote:

> I have a shell buffer with a program sending lots of output.
> That buffer is not currently displayed.  I type C-h, and it prompts.
> So far, so good.
>
> The bug is that the prompt changes repeatedly.  A space gets added at
> the beginning and the hyphen disappears at the end.  Then the space
> disappears and the hyphen reappears.  This oscillation continues
> indefinitely at the rate of 3 or 4 changes per second.

I don't see this. What I see (24.2.91) is:

emacs -Q -f shell

;; run this in shell buffer
while : ; do
 sleep 0.5
 echo hi
done

C-x b *scratch* RET
C-h

So long as the shell is looping, I get no C-h prompt at all.
If I interrupt the loop, I get the intended:

C-h (Type ? for further options)-

Message #11 received at 13255 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 13255 <at> debbugs.gnu.org, rms <at> gnu.org
Subject: Re: bug#13255: 24.2.50;
	output in nonvisible shell buffer changes prompt
Date: Sun, 23 Dec 2012 13:54:22 +0100

On Sat, 22 Dec 2012 22:33:29 -0500 Glenn Morris <rgm <at> gnu.org> wrote:

> Richard Stallman wrote:
>
>> I have a shell buffer with a program sending lots of output.
>> That buffer is not currently displayed.  I type C-h, and it prompts.
>> So far, so good.
>>
>> The bug is that the prompt changes repeatedly.  A space gets added at
>> the beginning and the hyphen disappears at the end.  Then the space
>> disappears and the hyphen reappears.  This oscillation continues
>> indefinitely at the rate of 3 or 4 changes per second.
>
> I don't see this. What I see (24.2.91) is:
>
> emacs -Q -f shell
>
> ;; run this in shell buffer
> while : ; do
>  sleep 0.5
>  echo hi
> done
>
> C-x b *scratch* RET
> C-h
>
> So long as the shell is looping, I get no C-h prompt at all.
> If I interrupt the loop, I get the intended:
>
> C-h (Type ? for further options)-


When I repeat Glenn's recipe in GNU Emacs 24.3.50.2
(x86_64-suse-linux-gnu, GTK+ Version 3.4.4) of 2012-12-23 on rosalinde,
revision 111308 jan.h.d <at> swipnet.se-20121223123537-gfe4g8dbhcckdj6e, I
also get no prompt on typing `C-h'; but if I uncheck "Blink Cursor" in
the Options menu and again type `C-h', then I see exactly what rms
reported.

Steve Berman

Message #14 received at 13255 <at> debbugs.gnu.org (full text, mbox):

From: Chong Yidong <cyd <at> gnu.org>
To: Stephen Berman <stephen.berman <at> gmx.net>
Cc: Glenn Morris <rgm <at> gnu.org>, 13255 <at> debbugs.gnu.org, rms <at> gnu.org
Subject: Re: bug#13255: 24.2.50;
	output in nonvisible shell buffer changes prompt
Date: Sun, 06 Jan 2013 10:38:20 +0800

Stephen Berman <stephen.berman <at> gmx.net> writes:

>> emacs -Q -f shell
>>
>> ;; run this in shell buffer
>> while : ; do
>>  sleep 0.5
>>  echo hi
>> done
>>
>> C-x b *scratch* RET
>> C-h
>
> I also get no prompt on typing `C-h'; but if I uncheck "Blink Cursor"
> in the Options menu and again type `C-h', then I see exactly what rms
> reported.

I've made a commit to trunk which should fix this.

Message #19 received at 13255 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Chong Yidong <cyd <at> gnu.org>
Cc: Glenn Morris <rgm <at> gnu.org>, 13255 <at> debbugs.gnu.org, rms <at> gnu.org
Subject: Re: bug#13255: 24.2.50;
	output in nonvisible shell buffer changes prompt
Date: Sun, 06 Jan 2013 20:49:41 +0100

On Sun, 06 Jan 2013 10:38:20 +0800 Chong Yidong <cyd <at> gnu.org> wrote:

> Stephen Berman <stephen.berman <at> gmx.net> writes:
>
>>> emacs -Q -f shell
>>>
>>> ;; run this in shell buffer
>>> while : ; do
>>>  sleep 0.5
>>>  echo hi
>>> done
>>>
>>> C-x b *scratch* RET
>>> C-h
>>
>> I also get no prompt on typing `C-h'; but if I uncheck "Blink Cursor"
>> in the Options menu and again type `C-h', then I see exactly what rms
>> reported.
>
> I've made a commit to trunk which should fix this.

I updated to trunk revno 111429 and confirm the oscillating dash/space
problem in the OP, which occurs when the blinking cursor is disabled, is
now fixed; thanks.  However, when the blinking cursor is enabled and the
above recipe is repeated, `C-h' is still not echoed (nor is any prefix
key).

Steve Berman

Message #24 received at 13255 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 13255 <at> debbugs.gnu.org, rms <at> gnu.org
Subject: Re: bug#13255: 24.2.50; output in nonvisible shell buffer changes
 prompt
Date: Sat, 04 Dec 2021 05:15:26 +0100

Glenn Morris <rgm <at> gnu.org> writes:

> emacs -Q -f shell
>
> ;; run this in shell buffer
> while : ; do
>  sleep 0.5
>  echo hi
> done
>
> C-x b *scratch* RET
> C-h
>
> So long as the shell is looping, I get no C-h prompt at all.
> If I interrupt the loop, I get the intended:
>
> C-h (Type ? for further options)-

This problem is still present in Emacs 29 (whether blink-cursor-mode is
enabled or not (it was reported that switching it off would mitigate the
problem)).

So I guess process output makes the thing that displays `C-x -' (or `C-h
-') short-circuits a timeout somewhere?  Hm...  this sounds familiar; I
feel I've seen a discussion of this somewhere semi-recently.  Anybody
remember?

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

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