DOKK / manpages / debian 12 / libx11-doc / XkbKeyTypeIndex.3.en
XkbKeyTypeIndex(3) XKB FUNCTIONS XkbKeyTypeIndex(3)

XkbKeyTypeIndex - Obtain the index of a key type or the pointer to a key type

int XkbKeyTypeIndex (XkbDescPtr xkb, KeyCode keycode, int group);

Xkb description of interest
keycode of interest
group index

XkbKeyTypeIndex computes an index into the types vector of the client map in xkb from the given keycode and group index.

libX11 1.8.4 X Version 11