[HarfBuzz] an issue regarding discrepancy between Korean and Unicode standards

[Behdad Esfahbod]

Hi,

Can you please tell me what the desired rendering of that sequence with malgun
is?  With Uniscribe I get three disjoint glyphs.  Is *that* the desired rendering?

behdad

On 13-03-20 11:03 PM, Dohyun Kim wrote:
> Hi,
> 
> When a sample input string, say "U+1100 U+1161 U+11F0", is processed
> by current version of harfbuzz with some fonts, eg. malgun.ttf bundled
> with windows 8, we get something like "U+AC00 U+11F0", which is not
> good in its visual result.
> 
> The reason is that there is discrepancy between Korean industrial
> standad (KS X 1026-1: 2007) and Unicode normalization rule.
> Malgun.ttf observes Korean standard only and does not care about
> international unicode standard for normalizaiton.  FYI, an English
> translation of KS X 1026-1 is available at
> ftp://std.dkuug.dk/ftp.anonymous/JTC1/SC2/WG2/docs/n3422.pdf.
> 
> Normalization done by current harfbuzz is of course compliant with
> unicode standard.  "U+AC00 U+11F0", ie. precomposed character in
> Hangul syllable block followed by trailing consonant Jamo letter, is
> perfectly legal and is canonically identical to "U+1100 U+1161
> U+11F0".  According to KS X 1026-1, however, this should not occur.
> Section 5.3 of the Korean standard says: "A Wanseong syllable
> block(U+AC00..U+D7A3) cannot be recomposed with Johab Hangul
> letters(U+1100..U+11FF U+A960..U+A97C U+D7B0..U+D7FB) to represent
> another Hangul syllable block."  See also section 6.4 of this
> standard.
> 
> I have hesitated about posting this issue as harfbuzz is observing
> unicode normalization rule.  We cannot say it is a bug, and many other
> libraries including glib and icu is doing the same as harfbuzz.  I
> believe that font developers should care about unicode standard as
> well, which some fonts (jieupsida and hcr-lvt) are already supporting.
>  But as there are other fonts (malgun.ttf and unbatang.ttf) which do
> not give us good result with current harfbuzz, I am now raising this
> issue.  Above all, malgun.ttf is now the default Hangul font for the
> most widely used OS here in Korea.  I have little knowledge about
> programming languages, but the Korean standard mentioned above has
> some sample code in its appendix.
> 
> Best,
> --
> Dohyun Kim
> College of Law, Dongguk University
> Seoul, Republic of Korea
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-- 
behdad
http://behdad.org/