https://invisible-island.net/xterm/xtoolkit/
XtCallActionProc - invoke an action procedure directly
#include <X11/Intrinsic.h>
void XtCallActionProc(Widget widget, const char *action, XEvent *event,
String *params, Cardinal num_params);
widget Specifies the widget in which the action is to be invoked.
Must be of class core of any subclass thereof.
action Specifies the name of the action routine.
event Specifies the contents of the event passed to the action rou-
tine.
params Specifies the contents of the params passed to the action
routine.
num_params
Specifies the num of entries in params.
XtCallActionProc searches for the named action routine in the same man-
ner and order as translation tables are bound. If found, the action
routine is invoked with the specified widget, event pointer, and param-
eters. It is the responsibility of the caller to ensure that the con-
tents of event, params, and num_params arguments are appropriate for
the specified routine, and if necessary, that the specified widget is
realized or sensitive. If the named action routine cannot be found,
XtCallActionProc generates a warning message and returns.
X Toolkit Intrinsics – C Language Interface
Xlib - C Language X Interface
X Version 11 libXt 1.1.5.2 XtCallActionProc(3)