Re: How to use "smart kerning" font features in Emacs using composition-function-table

[Eli Zaretskii]

> From: Steve Molitor <stevemolitor@gmail.com>
> Date: Sun, 26 Nov 2023 14:42:36 -0600
> Cc: emacs-devel@gnu.org
> 
> For ligature support, I do need something like this for Commit Mono:
> 
>     (set-char-table-range
>      composition-function-table
>      t
>      `([" [,-.:;A-Z_a-z><=!&|+-?/\\]+" 0 font-shape-gstring]))

Beware: composition-function-table is global, so the above will ligate
characters on the mode line as well, which might not be what you want.

> > Character composition in Emacs was never meant to be used for ASCII
> > characters, nor, more generally, for a significant fraction of buffer
> > text, except in several scripts (such as Arabic) where all the text
> > must be shaped to be legible.
> 
> Does performance suffer a lot in those languages, like Arabic?

It suffers some, yes.