[HarfBuzz] 'vert' substitutions in CJK fonts

[Grigori Goronzy]

On 02/05/2013 01:50 AM, suzuki toshiya wrote:
> Hi,
> 
> Thank you for opening the interesting discussion.
> I think, the script names in OpenType spec are not identical with the
> block names in Unicode; "kana" does not specify the small group of katakana
> and hiragana, but also specify the group including katakana, hiragana,
> CJK ideographs, CJK punctuations, CJK symbols etc etc.
>

They are not identical to Unicode, but "kana" indeed means just Katakana
and Hiragana in OpenType, at least according to the specification:

https://www.microsoft.com/typography/otspec/scripttags.htm

The lack of detail in the OpenType specification is really bad... in
this case it just says it's not always similar to Unicode but doesn't
explain how it differs from it either. :(

> When I worked for poppler (PDF rendering library), I got similar problem;
> http://lists.freedesktop.org/archives/poppler/2012-March/008860.html
> I should note that the default language system strategy would not work
> well with (old versions of?) Batang font (a Korean font bundled to Microsoft
> Windows).
>

Hmm, interesting... but lack of language-specific matching is not the
problem here.

> when vertical text is requested without embedded font, how OpenType layout
> feature should be configured; I used the combinations CHN/hani for Chinese
> Simplified or Traditional, JAN/kana for Japanese, KOR/hang for Korean.
> But it was designed to fit the internal design of the poppler, more
> comprehensive consideration would be expected for real i18n software.
>

So you use a fixed script for a given language? I don't know, but this
seems to be quite hacky. Often you don't even know what language you're
going to display. This might work in poppler's case, but in my case
(render some line of Unicode text with arbitrary languages) it does not.

Best regards
Grigori