Re: What's happened to M-<tab> `completion-at-point'?

[Stefan Monnier]

Yuri Khan [2022-05-05 03:31:24] wrote:
> On Thu, 5 May 2022 at 03:16, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>> AFAIK the `backtab` is usually used for `S-tab` rather than `M-tab`.
>> What do you get if you hit the TAB key together with the Shift modifier?
>> Does Emacs also receive the ESC TAB byte sequence in that (and then maps
>> it back (correctly this time) to `backtab`)?
> On my Ubuntu 22.04 with Linux 5.15.0, in tty, both Shift+Tab and
> Alt+Tab produce an ESC TAB sequence.

Aha!

   Shift+Tab === Linux kernel ===> ESC TAB === ncurses ===> backtab

makes sense.

> So probably the problem on the
> ncurses/terminfo side is induced by a problem on the Linux side.

Indeed, the problem seems to be that both Shift+Tab and Alt+Tab emit the
same byte sequence (the byte sequence historically used for M-Tab) and
are hence indistinguishable :-(

In the mean time we can add a hack in lisp/term/linux.el to remove the
bogus `ESC TAB => backtab` remapping since I suspect that `Alt+Tab` is
used much more often than `Shift+Tab` in Emacs running in the
Linux console.


        Stefan