Re: [Indic-computing-standards] Re: Malayalam Half-U: how

[Keyur S. <key...@ya...>]

--- "Dr. U.B. Pavanaja" <pav...@vi...> wrote:
> From these discussions I can infer one thing: We need a 
> mechanism of choosing one of the many possible display forms for 
> a particular combination. 
> 
> We are having a similar requirement for Kannada for the case of 
> "arkavattu" (reph) and "half ra". Both forms of display are 
> possible and both are correct. I had mentioned this to the 
> people responsible for OpenType specifications of Indic scripts. 
> Currently they don't have any plans to do this changes.

Can't it be done using Zero Width Joiner (U+200D)? ZWJ is used to produce
half forms of consonant/ligature in Indic scripts.

(Ra Halant ZWJ) sequence will produce desired half form of Ra.

> 
> Another point I would like mention here: The sorting rule in 
> Unicode has got nothing to do with the character code pages. 
> They are different. Unicode has two charts -character chart and 
> the collation table. Details of collation are available at 
> www.unicode.org/tr10

Yes, separate algorithm is required. Otherwise it will lead to wrong
sorting sequence. I'll try to explain this by giving simple example.

Consider the following sequences:
1. Ka Nukta
2. Qa
3. Ka Halant
4. Kha
5. Ka

If you simply sort these sequences acording to their relative position in
Unicode chart (i.e., simple string matching operation), you get the
following sequence.

1) Ka
2) Ka Nukta
3) Ka Halant
4) Kha
5) Qa

Clearly, this is wrong because "Ka Nukta" is equivallent to "Qa" in
rendering. Correct order is as below:

(1) Ka
(2) Ka Nukta (or Qa)
(3) Qa       (or Ka Nukta)
(4) Ka Halant
(5) Kha

In short, normalization is needed before we sort the sequences. I am still
not happy about the position of "Ka Halant" in the sorting order.
Conceptually it should precede Ka because Ka is formed after adding vowel A
to pure form of Ka. So in sorting also pure Ka should precede full Ka.

- Keyur





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