[HarfBuzz] Selecting fonts for HarfBuzz

[Eli Zaretskii]

> From: Behdad Esfahbod <behdad at behdad.org>
> Date: Wed, 5 Jun 2019 12:45:00 -0700
> Cc: "harfbuzz at lists.freedesktop.org" <harfbuzz at lists.freedesktop.org>
> 
> HarfBuzz handles everything it understands.  It was designed, in fact, such that when combined with
> FreeType or other external font funcs implementation, it even "handles" font formats it does not understand. 
> Eg. HarfBuzz doesn't understand BDF, PCF, etc, but if you use hb-ft, you can use hb-ft for everything, and
> BDF, PCF etc also magically work because HarfBuzz defers to FreeType for glyph access, and simply
> "passes through" for the rest.  It was designed such that you can keep one shaping code path.

We don't currently use hb-ft on Windows.  But thanks, I think I
understand.