bug#56952: 29.0.50; Emoji skin-tone modifiers disrupt terminal output

["J.P." <jp@neverwas.me>]

Eli Zaretskii <eliz@gnu.org> writes:

> Can you tell which value of auto-composition-mode did the trick? Or
> what is the value of tty-type on that terminal?

On Alacritty 0.10.1 (with the example configuration loaded) `tty-type'
returns "alacritty". And doing

  (setq-default auto-composition-mode "alacritty")

inhibits auto composition. Similarly, on GNOME Terminal 3.38.3 (as
preconfigured by Debian bullseye) `tty-type' returns "xterm-256color",
and setting `auto-composition-mode' to the latter works as expected.

> And which file in lisp/term/ does Alacritty load when you start the
> -nw session?

It loads lisp/term/xterm.el, I guess because `term-file-aliases' maps
"alacritty" to "xterm". (GNOME Terminal also loads that file.)

> I'm asking because perhaps we should disable auto-composition-mode by
> default on this terminal, like we do for the Linux console.

For the virtual console, that certainly makes sense (bug#50865). As for
which terminal emulators support such composition, that'd likely take
some legwork to determine. (Alacritty, for one, seems to have pegged
this feature as low priority [1].) If special casing seems premature, I
guess there's precedent for describing such issues in etc/PROBLEMS, as
was done with Kitty (bug#50983).

[1] https://github.com/alacritty/alacritty/issues/3975