bug#23450: 24.5; Lossing DECCKM application sequences on "fg"

[Stefan Kangas]

Julien Palard <julien@palard.fr> writes:

> We noticed a bug, we're reproducing it like twice a week but we're still
> unable to reproduce it explicitly, sorry for that.
>
> Bug is: After sending emacs to the background with `C-z` and getting it
> back with `fg`, sometimes, our terminal misses the
> [DECCKM](http://www.vt100.net/docs/vt510-rm/DECCKM.html) flag.
>
> We can easily fix it via `(send-string-to-terminal "\e[?1h")`, so we're
> "sure" that this flag the "missing one", but we have no proof emacs is
> faulty here.
>
> It look like we're not alone:
> http://stackoverflow.com/questions/4548106/screen-somehow-unmaps-my-arrow-keys-in-emacs-after-a-z/37032152
>
> Here, we reproduced it with:
>
>  - urxvt, putty, gnome term
>  - emacs 24.5.1, emacs 24.4.1
>  - GNU screen 4.02.01, 4.03.01, tmux 2.2
>  - Debian GNU/Linux 8.4 (jessie)

This sounds a lot like Bug#2772 which was recently closed as unreproducible:
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=2772

Maybe we'll have better luck here.  One good piece of information that
the old bug lacked is that this is not happening consistently.

Are you still seeing this problem in a more recent version of Emacs,
preferably the latest version 26.2?

If the answer is yes, Eli Zaretskii suggested the following in the
discussion about the old bug report:

> A termscript file with all the keyboard input starting from before the
> suspension, from a system where the problem can be reproduced, could
> give us some hints.  See open-termscript.

Could you please provide us with such a termscript file?

Thanks,
Stefan Kangas