[HarfBuzz] Hangul shaping

[suzuki toshiya]

Hi,

Maybe I cannot tell anything you don't know...

The conventional Korean character encodings (like Wansung, Johab and
their extensions) had coded the precomposed Hangul (1 code for 1 syllable).
The coverage of the precomposed Hangul was not complete, it collected
the precomposed Hangul that are used frequently.

In Unicode, for the backward compatibility, the existing precomposed
Hangul were coded, but the possible combinations of Hangul that were
not coded in conventional encodings are decided to be coded as a
combinations of Hangul Jamo (glyphic component for L, V, T). Nothing
to say, a precomposed Hangul can be expressed by the combination of
Hangul Jamo. In the normalized Unicode text, the precomposed Hangul
are expected to be decomposed for disambiguity:
http://www.unicode.org/reports/tr15/#Hangul

> Also, is the preferred way fonts do Hangul as decomposed or composed?  I
> imagine decomposed.

Considering that many Japanese free fonts do not include OpenType feature
to compose Japanese diacritics (Dakuten, Han-Dakuten), I'm questionable
whether most Korean free fonts have OpenType features to render decomposed
text.

Regards,
mpsuzuki

Behdad Esfahbod wrote:
> Hi,
> 
> Can someone please explain Hangul OpenType shaping to me?
> 
> I'm trying to understand the ICU Hangul shaper:
> 
> http://bugs.icu-project.org/trac/browser/icu/trunk/source/layout/HangulLayoutEngine.cpp
> 
> From what I understand, it decomposes, marks for OpenType features, then
> recomposes!  How can that be of any use?
> 
> Also, is the preferred way fonts do Hangul as decomposed or composed?  I
> imagine decomposed.
> 
> Thanks,
> behdad
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