LaTeX-like symbol substitution: Combining characters cause formatting problems

[saf-dmitry]

When performing a LaTeX-like symbol substiution, description strings for some completion candidates in the "*Completions*" buffer appear misaligned, when the first character in a description string is a combining diacritical mark:

The same issue when using Company completion framework with the CAPF frontend enabled. Here, the description strings even appear in wrong color:

This is apparently because the space character immediately preceding the combining diacritical mark gets "consumed", that is, combined with the diacritical mark.

Emacs version: 30.2
Julia mode version: From GitHub on 2025-08-21

Experimenting with different fonts has shown that the formatting issue manifests itself if and only if a font does not support proper rendering of combined characters. Ironically, the JuliaMono font (among some others) does support it and it causes the formatting problem.

Suggested solution: Adding a zero-width space character (U+200B) before completions starting with a combining diacritical mark (or, for that matter, all completions) when defining :annotation-function property in the julia--latexsub-capf-list function:

(defun julia--latexsub-capf-list (beg end pred)
  "Return list suitable for use in `completion-at-point-functions' of latexsubs."
  (list beg end julia-mode-latexsubs :exclusive 'no
        :annotation-function (lambda (s)
                               (concat " \u200b" (gethash s julia-mode-latexsubs)))
        :exit-function (julia--latexsub-exit-function beg)
        :predicate pred))