https://invisible-island.net/xterm/xtoolkit/
XtCallCallbacks, XtCallCallbackList, XtHasCallbacks - process callbacks
#include <X11/Intrinsic.h>
void XtCallCallbacks(Widget w, const char *callback_name, XtPointer
call_data);
void XtCallCallbackList(Widget w, XtCallbackList callbacks, XtPointer
call_data);
typedef enum {XtCallbackNoList, XtCallbackHasNone, XtCallbackHasSome}
XtCallbackStatus;
XtCallbackStatus XtHasCallbacks(Widget w, const char *callback_name);
callback_name
Specifies the callback list to be executed or checked.
call_data Specifies a callback-list specific data value to pass to each
of the callback procedure in the list.
callbacks Specifies the callback list to be executed.
w Specifies the widget.
The XtCallCallbacks function calls each procedure that is registered in
the specified widget's callback list.
If callbacks is not NULL, XtCallCallbackList calls each of the callback
procedures in the list, passing client data and call_data. The call-
backs 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 call-
back list exists and has at least one callback registered, it returns
XtCallbackHasSome.
XtAddCallback(3)
X Toolkit Intrinsics – C Language Interface
Xlib - C Language X Interface
X Version 11 libXt 1.1.5.2 XtCallCallbacks(3)