[HarfBuzz] question about indic matra group rule

[Richard Wordingham]

On Mon, 17 Jun 2013 12:06:43 +0800
datao zhang <dataozhang at hotmail.com> wrote:
 
> I feel confuse for the syllable rule in
> hb-ot-shape-complex-indic-machine.rl: halant_or_matra_group =
> (final_halant_group | (h.ZWJ)? matra_group{0,4}); 
> I can't image there any case for indic script which 4 matra followed.

I take it that by 'Indic script' you mean 'Indian Indic script'.  There
are many words with 3 matras in Tibetan, and 4 different matras can
occur with simple monosyllables in Tai Tham.  These, however, happen not
to use the generic Indic shaper in HarfBuzz.

Informal Malayalam, however, does double some two-part vowels.

> Another issue is caused that you decompose matra before syllable
> analysis and allow more than one matra followed. ex: if we have two
> matras: (0xDD9,0xDD9). They will be treated as one syllable. I don't
> know what benefit we can get from such rule.

Decomposition is usually easier than composition, and the two-part
vowels need to be decomposed at some stage - consonant vowel ligatures
generally work with parts rather than with whole vowels.

Richard.