bug#54914: 28.1.50; Unable to form Brahmi conjuncts in Emacs

[समीर सिंह Sameer Singh]

Thank you very much for adding support for Brahmi!

I can notice two problems

1. Vowel signs are not attached properly to conjuncts.

    Correct output=hb-conjuncts-maatra.png   Incorrect Output=emacs-conjuncts-maatra.png

2. Conjuncts with more than two consonants are not supported.

    Correct output=hb-tri-conjuncts.png   Incorrect Output=emacs-tri-conjuncts.png

On Sat, Apr 16, 2022 at 3:51 PM Eli Zaretskii <eliz@gnu.org> wrote:

> From: Robert Pluim <rpluim@gmail.com>
> Cc: 54914@debbugs.gnu.org,  lumarzeli30@gmail.com
> Date: Thu, 14 Apr 2022 11:07:23 +0200
>
> >>>>> On Wed, 13 Apr 2022 21:26:55 +0300, Eli Zaretskii <eliz@gnu.org> said:
>
>     >> From: Robert Pluim <rpluim@gmail.com>
>     >> Cc: Eli Zaretskii <eliz@gnu.org>,  54914@debbugs.gnu.org
>     >> Date: Wed, 13 Apr 2022 18:56:21 +0200
>     >>
>     >> A brute-force example of what Eli's talking about would be:
>     >>
>     >> (set-char-table-range composition-function-table
>     >> '(#x11000 . #x1107F)
>     >> (list (vector "[\x11000-\x1107F]+" 0 #'font-shape-gstring)))
>
>     Eli> Does that really work?  I'm not sure it will catch the "consonant,
>     Eli> virama, consonant" rule (because the virama is a nonspacing mark, and
>     Eli> we have a default rule for those in composite.el).
>
> We do indeed. The following handles only Ka through Lla in combination
> with Virama, and seems to do the right thing here with Segoe UI
> Historic (which I donʼt think we can set as default for the Brahmi
> script, since itʼs non-free).
>
> ;; <Consonant, Virama, Consonant>, or <Consonant, Virama>, where the
> ;; latter indicates a vowelless consonant.
> (set-char-table-range composition-function-table
>                     '(#x11013 . #x11034)
>                     (list (vector "[\x11013-\x11034]\x11046[\x11013-\x11034]?"
>                                     0 #'font-shape-gstring)))

I've now added support for the Brahmi script to the master branch;
please test and report any problems you find.

(We cannot advertise Segoe UI Historic, unfortunately, since it is not
a free font, AFAICT.)

emacs-conjuncts-maatra.png
Description: PNG image

hb-conjuncts-maatra.png
Description: PNG image

emacs-tri-conjuncts.png
Description: PNG image

hb-tri-conjuncts.png
Description: PNG image