Re: Display of decomposed characters

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Wed, 23 Dec 2020 11:05:13 +0100
> 
> Before filing a bug, I wanted to ask whether the following Emacs
> behavior is intentional: Even with Cairo and Harfbuzz, Emacs displays
> decomposed Unicode characters (e.g. "a" followed by U+0308 COMBINING
> DIAERESIS) as separate glyphs. While that's not technically wrong, I
> think it would be better to display them as a single glyph, in other
> words, not distinguish between canonically equivalent Unicode strings.

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).