hpux man page for xpeekifevent

XPeekIfEvent()															    XPeekIfEvent()

Name
  XPeekIfEvent - get an event matched by predicate procedure without removing it from the queue.

Synopsis
  XPeekIfEvent(display, event_return, predicate, arg)
	Display *display;
	XEvent *event_return;
	Bool (*predicate)();
	XPointer arg;

Arguments
  display   Specifies a connection to an X server; returned from XOpenDisplay().

  event_return
	    Returns a copy of the matched event.

  predicate Specifies the procedure to be called to determine if each event that arrives in the queue is the desired one.

  arg	    Specifies the user-specified argument that will be passed to the predicate procedure.

Description
  XPeekIfEvent()  returns  an  event  only  when  the  specified  predicate  procedure	returns True for the event.  The event is copied into
  event_return but not removed from the queue.	The specified predicate is called each time an event is added to the queue,  with  the	argu-
  ments display, event_return, and arg.

  XPeekIfEvent() flushes the request buffer if no matching events could be found on the queue, and then waits for the next matching event.

  For more information, see Volume One, Chapter 8, Events.

See Also
  XQLength(),	XAllowEvents(),   XCheckIfEvent(),   XCheckMaskEvent(),  XCheckTypedEvent(),  XCheckTypedWindowEvent(),  XCheckWindowEvent(),
  XEventsQueued(), XGetInputFocus(), XGetMotionEvents(), XIfEvent(), XMaskEvent(), XNextEvent(), XPeekEvent(),	XPending(),  XPutBackEvent(),
  XSelectInput(), XSendEvent(), XSetInputFocus(), XSynchronize(), XWindowEvent().

Xlib - Input Handling														    XPeekIfEvent()