Subject: emacs terminal escape command error
From: modem <[email-masked]>
To: [email-masked]
Date: Mon, 1 Aug 2016 16:34:43 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi,

I am facing a problem with emacs inside tmux.
The problem can be reproduced easily.

Emacs seems to have an terminal issue when being back from background
mode on shell.

Let me explain:
When I put emacs in background (^z) and then in foreground again ("fg",
bash) sometime emacs will not reset properly the terminal and I won't be
able to scroll up (using PageUp/PageDown).

After debugging the issue with a tmux developer, we tracked it down to
emacs and believe this is an emacs issue with terminal handling when
going back from background mode.

I am attaching a snippet of the technical detail about this issue :

>  When you ^Z, tmux gets 112 bytes in all cases:
>
>  input_parse: %0 ground, 40 bytes:
\n\n\033[K\033[?1l\033>\033[34h\033[?25h\033[?1049l\033[39;49m\r
>  input_parse: %0 ground, 72 bytes: \r\n[1]+  Stopped
emacs large_text_file.txt\r\nroot@milu:~#
>
>  \033[?1049l is rmcup which exits cursor positioning (alternate
screen) mode.
>
>  Then when you type fg, it gets:
>
>  input_parse: %0 ground, 694 bytes:
\033[?1049h\033[34l\033[?1h\033=\033[24;1H\033[K\033[H\033[?25l\033[3mFile
Edit Options Buffers ...
>
>  \033[?1049h is smcup which turns it on again.
>
>  But sometimes, it gets:
>
>  input_parse: %0 ground, 674 bytes:
\033[24;1H\033[K\033[H\033[?25l\033[3mFile Edit Options Buffers ...
>
>  Where emacs is not sending \033[1049h, or in fact any of the smcup,
>  cvvis, smkx sequence it normally sends.

This can be reproduced by hitting ^z and then "fg" in a loop for a
couples of minutes. If you run tmux with "tmux -vvvv" you will be able
to obtain the logs mentionned above. To observe the problem you can just
press PageUp each time you are back in emacs, when the bug will
reproduce you won't pageUp inside emacs but enter the tmux's copy-mode.
My ~/.tmux.conf only has 1 line:
bind-key -T root PPage if-shell -F "#{alternate_on}" "send-keys PPage"
"copy-mode -e -u"

If you need me to apply some patch and/or reproduce just let me know I
will happily helps.

Thanks a lot,

-- modem