XIfEvent(3X11)                SDK X11 R4.11MU05               XIfEvent(3X11)


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

SYNTAX
       XIfEvent(display, eventreturn, predicate, arg)
             Display *display;
             XEvent *eventreturn;
             Bool (*predicate)();
             XPointer arg;

       Bool XCheckIfEvent(display, eventreturn, predicate, arg)
             Display *display;
             XEvent *eventreturn;
             Bool (*predicate)();
             XPointer arg;

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

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

       display   Specifies the connection to the X server.

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


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