Provided by: libx11-doc_1.6.2-1ubuntu2.1_all 

NAME
XkbSASetGroup - Sets the group_XXX field of act from the group index grp
SYNOPSIS
void XkbSASetGroup (XkbAction act, int grp);
ARGUMENTS
- act action from which to set group
- grp group index to set in group_XXX
DESCRIPTION
XkbSASetGroup sets the group_XXX field of act from the group index grp.
STRUCTURE
Actions associated with the XkbGroupAction structure change the current group state when keys are pressed
and released:
typedef struct _XkbGroupAction {
unsigned char type; /∗ XkbSA_{Set|Latch|Lock}Group */
unsigned char flags; /∗ with type, controls the effect on groups */
char group_XXX; /∗ represents a group index or delta */
} XkbGroupAction;
WARNING
This manpage seems to be incomplete
X Version 11 libX11 1.6.2 XkbSASetGroup(3)