Variable Fonts

Hello,

I have another question related to variable fonts.
My current implementation maps a face_id with a font variation defined by
me.
For example,
Bold is a variation with weight axis value 1.0 and SemiBold is a variation
with weight axis value 0.8 and I input a different face_id for each of the
variation when I call  FTC_Manager_LookupFace() function so that it can
cache glyphs of both the variations but I also think that a face_id should
be different only when we are loading a different font file and not when we
are applying different variations. I am a bit confused if my implementation
should cache glyphs of both the variations in the freetype cache manager
without changing the face_id. Please let me know.

FTC_Manager_LookupFace() - here I send different face_id for different
variations though they belong to the same font resource file(I mean the
same .ttf)

Thank You,
Tulsi Amin