[HarfBuzz] Fwd: Properly Rendering (Tamil-)Brahmi Short E/O

[Vinodh Rajan]

Hello,

I would like to know how to properly render/encode ligatures that
result from the following sequences in Brahmi.

CONSONANT + VOWEL-SIGN-E + VIRAMA
CONSONANT + VOWEL-SIGN-O + VIRAMA

>From §14.1 in the UCS:

<< Tamil Brahmi pulli (virama) had two functions: to cancel the inherent
vowel of consonants; and to indicate the short vowels [e] and [o] in
contrast to the long vowels [e:] and [o:] [...]  As a consequence, in Tamil
Brahmi text, the virama is used not only after consonants, but also after
the vowels e (U+1100F, U+11042) and o (U+11011, U+11044). This pulli is
represented using U+11046 brahmi virama >> (Pulli := Dot)

I tried using the 'rlig' feature to represent the sequence and it only
works for standalone syllables. If they are followed by another consonant,
HB recognizes the sequence as illegal and keeps inserting a dotted circle
before the Virama.

[image: 2018-07-19.png]
(𑀓𑁄𑁆    𑀓𑁄𑁆𑀓𑀼 :: KO+Virama and KO+Virama+KU)

As you can see above, while the standalone KO forms the proper ligature, HB
breaks the syllable before the Virama in the second sequence.

I am not sure if this is due to HB doing incorrect clustering of Brahmi
syllables or just incorrect
OT features in my font.  In any case, CONSONANT + VOWEL-SIGN-E/O + VIRAMA
must be recognized as a valid syllable cluster in Brahmi (at least with the
'oty' - Old Tamil locale).

Any help in this regard would be highly appreciated.

(I have also attached the font)

Cheers,

Vinodh Rajan


-- 
http://www.virtualvinodh.com
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