XIfEvent(3X11)      X Version 11 (Release 4)       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


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  XIfEvent(3X11)      X Version 11 (Release 4)       XIfEvent(3X11)



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
















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