> Is there any other function to switch the face_index when a font > contains multiple fonts, besides specifying the face_index when > creating the face?
It depends. In TrueType Collections, fonts with different font
indices might be really completely different fonts, so you can't avoid
creating another `FT_Face` object.
However, if you are referring to named instances of Variation Fonts
you can use function `FT_Set_Named_Instance`.
Werner
