Re: ucs-normalize and diacritics

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 25 Jul 2018 05:36:52 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: emacs-devel@gnu.org
> 
> > Would it be worth allowing emacs to change the font of the
> > preceding character to match the diacritic and (re-)attempt
> > composition?
> 
> Theoretically, yes.  But it could mean a serious surgery in how
> character composition is integrated into the display engine, and there
> are also usability and UI aspects that need to be considered, because
> the user might have good reasons to use the font she uses for the base
> character.

I've looked at the related code, and it least the first part doesn't
seem to be too hard: it just needs expanding some APIs.  The relevant
function is autocmp_chars, called from composition_reseat_it, which is
called by the CHAR_COMPOSED_P macro.  The only problem to solve is how
to determine what font to use if the composition includes more than 2
characters, and Emacs selects more than 2 fonts to display them (e.g.,
3-character composition, each character needs a different font).