with my new debugging info, I can answer my own question:

RVLFaceExpression is an enum:
0x0 rvl_FaceNormal
0x1 rvl_FaceSmile
0x2 rvl_FaceAnger
0x3 rvl_FaceSorrow
0x4 rvl_Surprise
0x5 rvl_Blink
0x6 rvl_OpenMouth