[HarfBuzz] Itemising Japanese scripts

[Khaled Hosny]

On Mon, Apr 25, 2016 at 08:18:14AM +1000, Simon Cozens wrote:
> On 25/04/2016 08:05, Khaled Hosny wrote:
> > The problem with merging is which script tag to select for the merged run,
> > Kana or Hani or “it depends on the font”.
> 
> Why does it matter what script tag to apply if there are no opentype
> interactions with Japanese?

If that is really the case, then yes it doesn’t matter. I know nearly
nothing about CJK typesetting and fonts, but I see features like “cpct”,
“fwid”, “halt”, “hwid”, etc. I even recall seeing that “kern” and “mark”
used in some fonts as well.

> On the other hand, I have just remembered one interaction: a pan-CJK
> font such as Source Han Sans / Noto Sans CJK will have variant forms of
> the kanji for Chinese, Japanese and Korean. But even then the selection
> should be done on language, not on script - I haven't checked how it works.

Depending on the font, if you didn’t select the right script, selecting
the language will have no effect.

> So if pushed I would say Kana, just in case. But it really shouldn't matter.