[HarfBuzz] Dotted Circles in Tai Tham

Richard Wordingham richard.wordingham at ntlworld.com
Tue Feb 24 05:03:18 PST 2015


On Mon, 23 Feb 2015 17:59:44 -0800
Roozbeh Pournader <roozbeh at google.com> wrote:

> Richard,
> 
> I am working on a new update of InSC for Unicode 8.0, which is
> available at https://github.com/roozbehp/unicode-data.
> 
> After that, we'll push that into HarfBuzz.
> 
> It would be best if you suggest updates to the Unicode property
> instead, including potentially subdividing a property value. In this
> way, users of all implementations (including Microsoft's Universal
> Shaping Engine) would benefit.

Are we still left with IndicSyllabicCategory.txt as the only
functional definition of the properties?  I have a few real questions
affecting the categorisation of U+1A55 TAI THAM CONSONANT SIGN
MEDIAL RA and U+1A56 TAI THAM CONSONANT SIGN MEDIAL LA.

1. Is <consonant><dependent_vowel>_<dependent_vowel> an allowed context
for a 'Consonant_Medial' if it is allowed for an invisible stacker plus
consonant?

2. Is <consonant><dependent_vowel>_# an allowed context for a
'Consonant_Medial' if it is allowed for an invisible stacker plus
consonant?

3. Are they allowed contexts for 'Consonant_Subjoined' if they are
allowed for an invisible stacker plus consonant? 

HarfBuzz has very liberal rules for the ordering of the constituents of
a Tai Tham syllable once one views the invisible stacker as a control
character to convert a character to 'consonant subjoined'.  I'm not
sure that the Universal Shaping Engine will - I am eagerly awaiting its
publication.

Correction: I checked as I wrote and see that the USE specification was
released yesterday.  If the blog page is correct, the Universal Shaping
Engine rejects the phonetic ordering of the Tai Tham encoding model.
The word /pɛːt/ 'eight' must be encoded <PA, SAKOT, DA, SIGN AE>!  I
shall be studying the specification today.  At first sight the USE
appears to reject the current encoding system.

An important question for U+1A7A, U+1A7B and U+1A7C is:

4. May a 'syllable modifier' be followed by something other than a
syllable modifier?  The description implies not, which reduces the
useful of what could have been a useful waste bin taxon, sweeping up
all the pure killers.  


> Please take a look and send me or UTC your suggestions (or file bugs
> at https://github.com/roozbehp/unicode-data/issues). If there was
> still a need to change something in HarfBuzz, we can do that too.

By 'sending to the UTC', are you suggesting anything more than a bug
report or document submission?

Richard.


More information about the HarfBuzz mailing list