RE: [Indic-computing-devel] Testing OpenType support

[Arun M <ar...@fr...>]

Thanks, Keyur and Andy for valuable comments

> > A1. <C1><virama> will produce Chillu form (if any).
> > A2. <C1><virama><ZWNJ> will produce halant form of C1.
> > A3. <C1><virama><C2> will produce a ligature if <C1> doesn't
> > have chillu form. 
> > A4. <C1><virama><ZWJ><C2> will produce a 
> > ligature if <C1> has chillu form. 
> 
> The problem with A4 here is that the current specification of 'half'
> does not allow a ligatures of C1C2. IMHO a new feature would need to be
> specified. (feature 'cillu' ?).

A4 is not required, based on my understanding of malayalam. 


> Why not just always put a ZWJ whenever a chillu is desired?
> So C1chillu = C1+ZWJ  (always) 

This is what we did with Malayalam pango module with x backend we made
some time back. (following malayalam support in  TeX.)

http://members.tripod.com/~jhellingman/IndianScriptsUnicode.html

> > Approach-2:
> > ----------
> > 
> > B1. <C1><virama><ZWJ> will produce Chillu form (if any).
> > B2. <C1><virama> will produce halant form if <C1> is not part
> > of a ligature. 
> > B3. <C1><virama><ZWNJ> will also produce 
> > halant form of <C1>. 
> > B4. <C1><virama><C2> will produce a 
> > ligature (or consonant conjunct).
> > 
> > The issue here is that people generally believe that ZWJ is
> > used to join the consonant preceding it with the consonant 
> > immediately following ZWJ. Thus, ZWJ virtually becomes part 
> > of the syllable. Here we are using it to terminate the syllable.
> 
> Keyur, I agree with you. Both of the approaches above make sense.
> However, Approach-2 is more compatible with the current state of the
> situation. It would need less work to get it to work and is less likely
> to break any existing implementations (IMHO).
> Approach- 2 does not explain how to create a chillu+consonant conjunct.
> Assuming your answer is <C1><virama><ZWJ><C2>, then again, either a new
> feature definition is required, or the existing feature 'half' will need
> respecifying.


Approach 1 works better in current situation(note that step A4 is not
needed). We will just need to add chillu feature. Also it goes with the
unicode suggestion that <consonant><virama><ZWNJ> will give halant form.
Also what i understand from some language experts is that when we write
NNA(or other consonants having chillu form) with visible halant now
days, it actually represents <NNA><vowel sign U><halant>   
(Vowel A is removed from consonant and U is added)

Approach 2 will be easier to make as we may not need any change in
renderer.

regards
arun