void XtCallCallbacks(w, callback_name, call_data) Widget w; String callback_name; XtPointer call_data;typedef enum {XtCallbackNoList, XtCallbackHasNone, XtCallbackHasSome} XtCallbackStatus;
void XtCallCallbackList(w, callbacks, call_data) Widget w; XtCallbackList callbacks; XtPointer call_data;
XtCallbackStatus XtHasCallbacks(w, callback_name) Widget w; String callback_name;
If callbacks is not NULL, XtCallCallbackList calls each of the callback procedures in the list, passing client data and call_data. The callbacks parameter must specify the contents of a widget or object resource declared with representation type XtRCallback .
The XtHasCallbacks function first checks to see if the widget
has a callback list identified by callback_name.
If the callback list does not exist, XtHasCallbacks 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