XtCallCallbacks(), XtHasCallbacks() - process callbacks
void XtCallCallbacks (Widget w, String callback_name,
XtPointer call_data)
typedef enum {XtCallbackNoList,
XtCallbackHasNone,
XtCallbackHasSome} XtCallbackStatus
XtCallbackStatus XtHasCallbacks (Widget w, String callback_name)
The XtCallCallbacks(3) function calls each procedure that is registered in the specified widget's callback list.
The XtHasCallbacks(3) function first checks to see if the widget has a callback list identified by callback_name. If the callback list does not exist, XtHasCallbacks(3) returns XtCallbackNoList. If the callback list exists but is empty, it returns XtCallbackHasNone. If the callback list exists and has at least one callback registered, it returns XtCallbackHasSome.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface