bug#33729: 27.0.50; Partial glyphs not rendered for Gujarati with Harfbuzz enabled (renders fine using m17n)

[Eli Zaretskii]

> Date: Sat, 22 Dec 2018 17:15:09 +0200
> From: Khaled Hosny <dr.khaled.hosny@gmail.com>
> Cc: rgm@gnu.org, far.nasiri.m@gmail.com, behdad@behdad.org,
>       33729@debbugs.gnu.org, kaushal.modi@gmail.com
> 
> > There's a FIXME in the change you pushed (which I believe just
> > repeats what was already in the previous version).  Ca you tell more
> > about the problem we need to fix there?
> 
> We need a way to get Unicode composition and decomposition for the
> a given character (implementing the uni_compose and uni_decompose
> functions I deleted).

Yes, but what does that entail?  Are these compositions and
decompositions defined by the Unicode UCD?  And how does Harfbuzz use
the results for a given character?

> I recall you suggested something earlier that I tried but couldn’t
> get to work, the exact detail escapes me.

I probably suggested using the 'decomposition' property of a
character, and perhaps als the facilities in ucs-normalize.el.