[HarfBuzz] Rendering Thai

[Behdad Esfahbod]

On 01/19/2012 03:02 AM, Theppitak Karoonboonyanan wrote:

> PUA shaping can be an option for legacy font support.
> ("Legacy" here means Windows XP, which still dominates the
> market, though.)

Ok, for now lets forget about that.  When Indic and basic Thai is working we
can revisit it :).


>> The hb-view tool included in the HarfBuzz repo under util/.
> 
> It's severely broken in my box. See the attached p.png for the
> output of the command:
> ./hb-view /usr/share/fonts/truetype/tlwg/Loma.ttf
> ป่ำซ้ำพ่อปู่พี่ปี่ฎุฐุญุ > p.png

Quite possibly you didn't have either glib or ICU.  Try with glib available so
HB can pick up Unicode data from glib.  I've attached the output I'm getting.


>> Right, we decompose.  But what's the reordering?  I believe that's where the
>> problem is.
> 
> Yes, it looks like the reordering (or normalization) stage is missing
> after the decomposition stage.

It's not normalization from what I hear from Eric Muller.  This is what he
said, and I'll eventually implement it:

"""
When you have a sara am, decompose it in nikhahit + sara a, *and* mode the
nihkahit backwards over any *tone* mark (0E48-0E4B).

<0E14, 0E4B, 0E33> -> <0E14, 0E4D, 0E4B, 0E32>

This reordering is legit only when the nikhahit comes from a sara am, not when
it's there to start with. The string <0E14, 0E4B, 0E4D> is probably not what a
user wanted, but the rendering is nevertheless nikhahit above chattawa.

Same for Lao.
"""



behdad
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