[HarfBuzz] Support for Stylistic Sets

[Eli Zaretskii]

> Date: Sat, 14 Sep 2019 21:33:00 +0100
> From: Richard Wordingham <richard.wordingham at ntlworld.com>
> Cc: harfbuzz at lists.freedesktop.org
> 
> On Sat, 14 Sep 2019 21:15:04 +0300
> Eli Zaretskii <eliz at gnu.org> wrote:
> 
> > > Date: Sat, 14 Sep 2019 18:13:25 +0100
> > > From: Richard Wordingham <richard.wordingham at ntlworld.com>
> > > 
> > > I think it's safe to specify the use of unsupported features, in
> > > which case this is a luxury feature.  
> > 
> > you mean, specifying an unsupported feature will not cause hb_shape to
> > fail, but instead just use the nominal glyphs?
> 
> Essentially yes, i.e. unsupported features will simply be ignored.

Then there's no need to know whether a feature is supported.  Thanks.

> > Emacs currently leaves it to HarfBuzz to guess the language, so I
> > don't think this is an issue.
> 
> Does HarfBuzz guess the language?

Yes.