bug#30092: Compose key behaviour is incorrect when locale is set to Esperanto

bug#30092: Compose key behaviour is incorrect when locale is set to Esperanto

[Carmen Bianca Bakker]

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Dear Emacs maintainer(s),

I am running into an unusual bug of sorts.  That is:  The behaviour of the
compose key is incorrect when the locale is set to "eo" (Esperanto).  The exact
behaviour is as follows:

- When running `XMODIFIERS="" emacs`, `<MULTI_KEY> a e` does not produce æ.  It
  simply produces nothing.  `<MULTI_KEY> ' e` correctly produces é, however.

- When running `XMODIFIERS=@im=ibus emacs` (my default), simply pressing the
  compose key results in `<MULTI_KEY> is undefined`.

Emacs is (almost) the only program where this happens. The only other program
that reliably fails on the same sequences is xterm.  xterm results in the same
behaviour for both `XMODIFIERS` values.  All other programs (Firefox,
LibreOffice, gedit, Yakuake, etc.) function correctly.

But, when I run `LC_ALL=en_GB.UTF-8 emacs`, the behaviour is as expected:  All
compose key sequences just work.  The same is true for running xterm with the
en_GB.UTF-8 locale.

I am running Debian Buster with GNOME on Wayland.  The bug occurs with a vanilla
.emacs.d/ folder.  I have ibus installed and running, but also without ibus
running, I run into the first of the two items.

Because it happens on both Emacs and xterm, I suspect that this bug may not be
exclusive to Emacs, but I am hoping that someone with a better understanding
than I could point me in the right direction.

Thank you very much.

Yours sincerely,
Carmen

In GNU Emacs 25.2.2 (x86_64-pc-linux-gnu, GTK+ Version 3.22.20)
 of 2017-09-12, modified by Debian built on trouble
Windowing system distributor 'The X.Org Foundation', version 11.0.11905000
System Description:	Debian GNU/Linux testing (buster)

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Important settings:
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  value of $XMODIFIERS: @im=ibus
  locale-coding-system: iso-latin-3-unix

Major mode: Fundamental

Minor modes in effect:
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Recent messages:
Loading debian-ispell...done
Loading /var/cache/dictionaries-common/emacsen-ispell-dicts.el (source)...done
Loading /etc/emacs/site-start.d/50dictionaries-common.el (source)...done
Loading /etc/emacs/site-start.d/50latex-cjk-common.el (source)...
Loading cjk-enc...done
Loading /etc/emacs/site-start.d/50latex-cjk-common.el (source)...done
Loading /etc/emacs/site-start.d/50latex-cjk-thai.el (source)...done
Loading /etc/emacs/site-start.d/50mu4e.el (source)...done
Loading /etc/emacs/site-start.d/50texlive-lang-english.el (source)...done
For information about GNU Emacs and the GNU system, type C-h C-a.
scroll-up-command: End of buffer [2 times]

Load-path shadows:
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bug#30092: Compose key behaviour is incorrect when locale is set to Esperanto

[Lars Ingebrigtsen]

Carmen Bianca Bakker <carmen@carmenbianca.eu> writes:

> I am running into an unusual bug of sorts.  That is: The behaviour of
> the compose key is incorrect when the locale is set to "eo"
> (Esperanto).  The exact behaviour is as follows:
>
> - When running `XMODIFIERS="" emacs`, `<MULTI_KEY> a e` does not produce æ.  It
>   simply produces nothing.  `<MULTI_KEY> ' e` correctly produces é, however.

(I'm going through old bug reports that unfortunately got no response at
the time.)

This bug is still present in Emacs 28 -- I reproduced it with

XMODIFIERS="" LC_ALL=eo ./src/emacs -Q

(after defining the "eo" locale on this laptop).

Before I go poking into this any further -- has anybody else here on the
mailing list encountered this problem before?

> - When running `XMODIFIERS=@im=ibus emacs` (my default), simply pressing the
>   compose key results in `<MULTI_KEY> is undefined`.

This doesn't seem to happen any more, though.

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