XtAppPeekEvent()														  XtAppPeekEvent()

Name
  XtAppPeekEvent - return, but do not remove the event at the head of an application's input queue; block if no events are available.

Synopsis
  Boolean XtAppPeekEvent(app_context, event_return)
	 XtAppContext app_context;
	 XEvent *event_return;

Inputs
  app_context
	    Specifies the application context.

Outputs
  event_return
	    Returns the event from the head of the queue, if that event is an X event.

Returns
  True if the event at the head of the queue is an X event; False if it is a timer event or an alternate input source event.

Description
  If  there  are  X  events pending on any of the displays in app_context, XtAppPeekEvent() copies the event from the head of the application
  event queue into event_return (without removing the event from the queue) and returns True.  If there are no events, it flushes the  output
  buffers  of each display and checks again.  If there are still no pending X events on any of the displays, but there are timer or alternate
  input events ready, XtAppPeekEvent() returns False.

  If there are no events of any kind, XtAppPeekEvent() blocks until one occurs, and then if it is an  X  event,  copies  the  event  (without
  removing it from the queue) and returns True or returns False otherwise.  Note that XtAppPeekEvent() never calls background work procedures
  registered with XtAppAddWorkProc() .

Usage
  Programs rarely need this much control over the event dispatching mechanism.	Most programs use XtAppMainLoop().

  If you want to get X events and remove them from the input queue, consider XtAppNextEvent().	 This  function  also  dispatches  timer  and
  alternate input events.

  If  you  want  to check for input events without blocking, use XtAppPending().  This function returns a value that indicates which types of
  events are pending for an application context, or 0 if no events are pending.

See Also
  XtAppMainLoop(1), XtAppNextEvent(1), XtAppPending(1).

Xt - Event Handling														  XtAppPeekEvent()