XkbFindOverlayForKey - Man Page

char * XkbFindOverlayForKey (XkbGeometryPtr geom, XkbSectionPtr section, _Xconst char *under);

geom

geometry that contains the section

section

section to be searched for matching keys

under

primary name of the key to be considered

Keys that can generate multiple keycodes may be associated with multiple names.  Such keys have a primary name and an alternate name.

XkbFindOverlayForKey uses the primary name of the key, under, to look up the alternate name, which it returns.