offer_focus man page
offer_focus — Offers the input focus to a particular object. Allegro game programming library.
int offer_focus(DIALOG *dialog, int obj, int *focus_obj, int force);
Offers the input focus to a particular object. Normally the function sends the MSG_WANTFOCUS message to query whether the object is willing to accept the focus. However, passing any non-zero value as force argument instructs the function to authoritatively set the focus to the object.