I tried the examples in the readme but the face = newface("hack_regular.ttf") return type is Ptr{FreeType.LibFreeType.FT_FaceRec_} and it's not compatible with renderface/renderstring!, which needs ::FreeTypeAbstraction.FTFont.
As workaround I used face = FreeTypeAbstraction.FTFont(newface("DroidSansMono.ttf"))