XtInsertEventTypeHandler(3Xt)

     NAME
          XtInsertEventTypeHandler, XtRemoveEventTypeHandler,
          XtRegisterExtensionSelector, XtSetEventDispatcher,
          XtDispatchEventToWidget - extension event handling

     SYNTAX
          void XtInsertEventTypeHandler(widget, event_type,
          select_data, proc, client_data, position)
                Widget wdget;
                int event_type;
                XtPointer select_data;
                XtEventHandler proc;
                XtPointer client_data;
                XtListPosition position;

          void XtRemoveEventTypeHandler(widget, event_type,
          select_data, proc, client_data)
                Widget wdget;
                int event_type;
                XtPointer select_data;
                XtEventHandler proc;
                XtPointer client_data;

          void XtRegisterExtensionSelector(display, min_event_type,
          max_event_type, proc, client_data)
                Display* display;
                int min_event_type;
                int max_event_type;
                XtExtensionSelectProc proc;
                XtPointer client_data;

          XtEventDispatchProc XtSetEventDispatcher(display,
          event_type, proc)
                Widget widget;
                int event_type;
                XtEventDispatchProc proc;

          Boolean XtDispatchEventToWidget(widget, event)
                Widget widget;
                XEvent* event;

     ARGUMENTS
          widget    Specifies the widget for this event handler.  Must
                    be of class Core or any subclass thereof.

          event_type
                    Specifies the event type.

          select_data
                    Specifies data used to select or deselect events
                    from the server.

          proc      Specifies the proc.

          client_data
                    Specifies additional data to be passed to the
                    event handler.

          position  Specifies when the event handler is to be called
                    relative to other previously registered handlers.

          display   Specifies the display.

          min_event_type, max_event_type
                    Specifies the range of event types for this
                    extension.

          event     Specifies a pointer to the event to be dispatched.

     DESCRIPTION
          The XtInsertEventTypeHandler function registeres a procedure
          with the dispatch mechanism that is to be called when an
          event that matches the specified event_type is dispatched to
          the specified widget.

          If event_type is one of the core X protocol events then
          select_data must be a pointer to a value of type EventMask,
          indicating the event mask to be used to select for the
          desired event.  This event mask will be included in the
          value returned by XtBuildEventMask.  If the widget is
          realized XtInsertEventTypeHandler calls XSelectInput if
          necessary. Specifying NULL for select_data is equivalent to
          specifying a pointer to an event mask containing 0. This is
          similar to the XtInsertRawEventHandler function.

          If event_type specifies an extension event type then the
          semantics of the data pointed to by select_data are defined
          by the extension selector registered for the specified event
          type.

          In either case the Intrinsics are not required to copy the
          data pointed to by select_data, so the caller must ensure
          that it remains valid as long as the event handler remains
          registered with this value of select_data.

          The position argument allows the client to control the order
          of the invocation of event handlers registered for the same
          event type. If the client does not care about the order, it
          should normally specify XtListTail, which registers this
          event handler after any previously registered handlers for
          this event type.

          The XtRemoveEventTypeHandler function unregisters an even
          handler registered with XtInsertEventTypeHandler for the
          specified event type. The request is ignored if client_data
          does not match the value given with the handler was
          registered.

          If event_type specifies on of the core X protocol events,
          select_data must be a pointer to a value of type EventMask,
          indicating the mask to be used to deselect for the
          appropriate event.  If the widget is realized,
          XtRemoveEventTypeHandler calls XSelectInput if necessary.
          Specifying NULL for select_data is equivalent to specifying
          a pointer to an event mask containing 0. This is similar to
          the XtRemoveRawEventHandler function.

          If event_type specifies an extension event type then the
          semantics of the data pointed to by select_data are defined
          by the extension selector registered for the specified event
          type.

          The XtRegisterExtensionSelector function registers a
          procedure to arrange for the delivery of extension events to
          widgets.

          If min_event_type and max_event_type match the parameters to
          a previous call to XtRegisterExtensionSelector for the same
          display, the proc and client_data replace the previously
          registered values. If the range specified by min_event_type
          and max_event_type overlaps the range of the parameters to a
          previous call for the same display in any other way, an
          error results.

          The XtSetEventDispatcher function registes the event
          dispatcher procedure specified by proc for event swith the
          type event_type. The previously registered dispatcher (or
          the default dispatcher if there was no previousl registered
          dispatcher) is returned. If proc is NULL, the default
          procedure is restored for the specified type.

          In the future, when XtDispatchEvent is called with an event
          of event_type, the specified proc (or the default
          dispatcher) will be invoked to determine a widget ot which
          to dispatch the event.

          The XtDispatchEventToWidget function scans the list of
          registered event handlers for the specified widget and calls
          each handler that has been registered for the specified
          event type, subject to the continue_to_dispatch value
          returned by each handler. The Intrinsics behave as if event
          handlers were registered at the head of the list for Expose,
          NoExpose, GraphicsExpose, and VisibilityNotify events to
          invoke the widget's expose procedure according to the
          exposure compression rules and to update the widget's
          visible field if visible_interest is True.  These internal
          event handlers never set continue_to_dispatch to False.

          XtDispatchEventToWidget returns True if any event handler
          was called and False otherwise.

     SEE ALSO
          XtGetKeyboardFocusWidget(3Xt)
          X Toolkit Intrinsics - C Language Interface
          Xlib - C Language X Interface