XIfEvent(3X11)                       BSD                        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 XIfEvent function completes only when the specified predicate
     procedure returns True for an event, which indicates an event in the
     queue matches.  XIfEvent flushes the output buffer if it blocks waiting
     for additional events.  XIfEvent removes the matching event from the
     queue and copies the structure into the client-supplied XEvent structure.

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

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

SEE ALSO
     XPutBackEvent(3X11) XNextEvent(3X11), XSendEvent(3X11)
     Xlib - C Language X Interface