[HarfBuzz] Retrieving optical size info?

[Khaled Hosny]

Is there is a way in Harfbuzz to get optical size info from the ‘size’
feature (searching the code, I could’t find any)? If not, is there any
plans in doing so?

Logically, this belongs to FontConfig or FreeType, but the awkward
choice of implementing it as a GPOS feature (that is not really a
feature) makes HarfBuzz the most practical place, or so I think.

(Background: I’m almost done with porting XeTeX from ICU LayoutEngine to
HarfBuzz, one of the few things remaining is getting optical size. The
current code uses some internal LE API and I want to move away from this
as possible).

Regards,
 Khaled