[HarfBuzz] Itemising Japanese scripts

[Khaled Hosny]

On Mon, Apr 25, 2016 at 07:41:39AM +1000, Simon Cozens wrote:
> On 25/04/2016 07:22, Khaled Hosny wrote:
> > This leaves Han which has its own OpenType tag and that is what I have
> > been seeing most. So I wounder what other application do, should I try
> > something clever like see what scripts/features/lookups are in the font
> > and decide to merge the scripts if it is safe (i.e. merging or not should
> > have no effect on features applied), or should I just leave the current
> > behaviour and not worry about it?
> 
> Just merge them. From an OpenType perspective, Japanese is boring.
> Japanese characters are treated as discrete, independent units except in
> extreme cases, (e.g. Kazuraki which uses ligatures to attempt to
> replicate a hand-written look) so there should not be any OpenType
> interactions between characters. I remember Paul Hunt saying that when
> they developed Kazuraki they had to rewrite chunks of their OpenType
> shaper to deal with it, as it was such a special case.
> 
> *Even if* there are OpenType interactions, these should take place
> within the context of a Japanese font which has both kana and kanji
> sets, so merging would be the right thing to do.

The problem with merging is which script tag to select for the merged run,
Kana or Hani or “it depends on the font”.

> The real fun you're going to have is getting the layout correct, but you
> can look at my code for how to implement that. :-)

Will do :)