[HarfBuzz] Support for Stylistic Sets

[Eli Zaretskii]

> From: Nikolay Sivov <bunglehead at gmail.com>
> Date: Sun, 15 Sep 2019 10:03:01 +0300
> Cc: Richard Wordingham <richard.wordingham at ntlworld.com>, 
> 	Harfbuzz <harfbuzz at lists.freedesktop.org>
> 
>  > Essentially yes, i.e. unsupported features will simply be ignored.
> 
>  Then there's no need to know whether a feature is supported.  Thanks.
> 
> MS Word for example shows a preview for each support ssXX feature, and user can select one they want.
> 
> I don't know how (or why) you plan to use that for emacs, but you'll need to have some logic to figure out
> which one to enable.

I think this should be up to the user and/or the application,
i.e. Lisp program that wants to take advantage of these features.

Or maybe I misunderstand what you mean by "figure out which one to
enable"?  Can you elaborate on the potential pitfalls?