Re: Ligature support

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: emacs-devel@gnu.org
> Date: Fri, 05 Nov 2021 16:56:00 +0100
> 
> I see that the harfbuzz people say that we should just run all the text
> through hb_shape instead of doing it selectively like we do it now:
> 
> ---
> Full text shaping is the only way to get this right. Everything else
> is a hack, and piling hacks on top of hacks is just storing
> maintenance problems up for yourself.
> ---

Yes, I know.  But how large chunk of the text they need to see to do
the job?  Emacs's display engine examines the text one character at a
time, so passing large chunks through the shaping engine is out of the
question.  The want at least words, possibly complete lines.

> How big a performance issue would it be to just run all the text through
> hb_shape?

You can try it by setting composition-function-table slots for every
character.  E.g., start by doing that for all ASCII and see what
happens.