[HarfBuzz] Itemising Japanese scripts

[Khaled Hosny]

On Mon, Apr 25, 2016 at 12:46:21AM +0900, suzuki toshiya wrote:
> Hi,
> 
> I will try to contact with W3C JLREQ experts to ask some
> recommended reference.  Before it, I list a few points;
> 
> * it is not rare to assign a font for Han character and
> different font for kana (I'm unfamiliar with the case
> 3 fonts for Han/Hiragana/Katakana are assigned in parallel).
> the most popular case would be the texts in the comic books.
> also, there are many kana-only font.
>
> * however, for PostScript-based systems, making a composite
> font (rearranged font) from multiple fonts might be popular
> technology. in the other words, the people using such technology
> did not split the text into Han-run & Kana-run. they use
> same text run including both character, and the font was
> switched by the codepoints of the character.

Script itemisation does not affect font selection in my case, the
application (Scribus) does not even do any font fallback and all font
selection is controlled by the user (for better or worth) and selecting
different fonts will split the runs.

> * it is difficult to handle the Latin characters in Japanese
> text schematically. Sometimes, they are expected to be rendered
> as Latin texts, but in other cases, the consisting Latin
> characters are dealt as Han/Kana characters. It is very
> confusing when we are trying to render vertical writing mode.

Fortunately (for me at least) I’m not doing vertical text at this
point, so it is not a concern. I’m mostly worried about efficiency and
whether there need to be any OpenType interaction between the different
scripts which would not be allowed due to the run splitting.

Regards,
Khaled