Subject: Re: bug#79279: 28.2; Combining characters cause formatting problems when showing CAP candidates

From: Eli Zaretskii <[email-masked]>
Date: Thu, 21 Aug 2025 08:04:06 +0300

> From: Dmitry Safronov <[email-masked]>
> Date: Wed, 20 Aug 2025 17:44:12 +0200
> 
> When triggering completion-at-point for a Unicode symbol in Julia
> mode, description
> strings for some completion candidates in the minibuffer appear
> misaligned, when the first character in a description string is a
> combining diacritical mark (see the
> attached screenshot). This is apparently because the space character immediately
> preseeding the combining diacritical mark gets "consumed", that is, combined
> with the diacritical mark. This issue is not specific to Julia mode,
> but appears to be a more general problem of presenting text containing
> leading combining characters.

Thanks.  However, I'm not sure I understand which part of Emacs or of
some add-on package produces this display, so it is hard to guess
where to look for code which needs to be fixed to avoid this problem.
And you haven't provided a recipe for reproducing the issue, which
makes it harder yet.

Presenting text which starts with a combining character indeed needs
some special code, but that code should be in the Lisp program which
creates the text.  And given what you tell, I don't yet have an idea
where that Lisp program is: in Emacs core, in Julia, somewhere else?

Could you show a recipe for reproducing the problem?  Preferably, such
a recipe should start from "emacs -Q" and turn on any optional
features needed to show the problem.  If possible, the recipe should
not include any third-party packages if you can demonstrate the
problematic completion buffer display without those packages.  E.g.,
if the problem is in completion-at-point, can you show which commands
to invoke to produce display such as in your screenshot, preferably
without involving Julia?