ultrix man page for xcheckifevent

XIfEvent(3X11)							     MIT X11R4							    XIfEvent(3X11)

Name
       XIfEvent, XCheckIfEvent, XPeekIfEvent - check the event queue with a predicate procedure

Syntax
       XIfEvent(display, event_return, predicate, arg)
	  Display *display;
	  XEvent *event_return;
	  Bool (*predicate)();
	  char *arg;

       Bool XCheckIfEvent(display, event_return, predicate, arg)
	  Display *display;
	  XEvent *event_return;
	  Bool (*predicate)();
	  char *arg;

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

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

       display	 Specifies the connection to the X server.

       event_return
		 Returns either a copy of or  the matched event's associated structure.

       predicate Specifies the procedure that is to be called to determine if the next event in the queue matches what you want.

Description
       The function completes only when the specified predicate procedure returns for an event, which indicates an event in the queue matches.
       flushes the output buffer if it blocks waiting for additional events.  removes the matching event from the queue and copies the structure
       into the client-supplied structure.

       When the predicate procedure finds a match, copies the matched event into the client-supplied structure and returns (This event is removed
       from the queue.)  If the predicate procedure finds no match, returns and the output buffer will have been flushed.  All earlier events
       stored in the queue are not discarded.

       The function returns only when the specified predicate procedure returns for an event.  After the predicate procedure finds a match, copies
       the matched event into the client-supplied structure without removing the event from the queue.	flushes the output buffer if it blocks
       waiting for additional events.

See Also
       XAnyEvent(3X11), XNextEvent(3X11), XPutBackEvent(3X11) XSendEvent(3X11)
       X Window System: The Complete Reference, Second Edition, Robert W. Scheifler and James Gettys

																    XIfEvent(3X11)