Re: Display of decomposed characters

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Fri, 25 Dec 2020 18:14:31 +0100
> Cc: help-gnu-emacs <help-gnu-emacs@gnu.org>
> 
> > They are (or should be) displayed as a composed glyph if you are using
> > a font that supports both a and COMBINING DIAERESIS.  Emacs cannot
> > compose characters that aren't supported by the same font (because
> > composition processing stops at face boundaries, and each font defines
> > internally a separate face).
> 
> Interesting. Indeed the two glyphs come from different fonts. Is there
> a way to force a single font for both of them?

If the default font supports the diaeresis, that will happen
automatically.  If not, then simply don't choose the default font that
doesn't support accents.

> Or should the algorithm be changed to perform composition before
> font selection?

That's (a) hard, and (b) a bad idea in general, because different
fonts generally have very different sizes of accents, and are
generally incompatible in terms of pixel dimensions of characters vs
accents.