[HarfBuzz] kaithi & arabic : glyphs that span number

[Madhu]

In April 2002, Sameer Singh posted a message on emacs-devel where he
demonstrated the use of harfbuzz numerals with the kaithi script

https://lists.gnu.org/archive/html/emacs-devel/2022-04/msg01297.html
to yield this image:

[1] https://lists.gnu.org/archive/html/emacs-devel/2022-04/png4ClBZc1zV4.png

There the first glyph spans the remaining chacracters when composed.

I tried to reproduce it and showed my work on this message

https://lists.gnu.org/archive/html/emacs-devel/2022-05/msg00341.html

but I only get

[2] https://lists.gnu.org/archive/html/emacs-devel/2022-05/pngTFsflcCrfU.png
The first character does not span the remaining digit characters.

Can anyone tell me what I might be missing?

1. 2.txt has code points 0x110BC 0x0967 0x0966 0x096E
2. hb-view --font-file=$HOME/.fonts/NotoSansKaithi-Regular.ttf --text-file=2.txt > 2.png

This produces the image in the above mentioned url [2] . I believe it should look like [1].

Similar tests for arabic numbers
a text file arabic-num.txt with code points 0x0600 0x31 0x32 0x33
and a command
hb-view --font-file=$HOME/.fonts/NotoSansArabic-Regular.ttf --text-file=arabic-num.txt --output-file=arabic-num.png

produces a file where the first character does not span the remaining
characters.

I believe I used the same font-files as Sameer did:

-rw-r--r-- 1 madhu users 260740 Mar 24  2020 NotoSansArabic-Regular.ttf
-rw-r--r-- 1 madhu users  87260 Mar 24  2020 NotoSansKaithi-Regular.ttf

---Madhu