XIfEvent(3X)                                         XIfEvent(3X)



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

SYNOPSIS
     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;

DESCRIPTION
     The XIfEvent function checks the event queue for the speci-
     fied event and 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.

     The XCheckIfEvent function checks the event queue for the
     specified event.  When the predicate procedure finds a
     match, XCheckIfEvent copies the matched event into the
     client-supplied XEvent structure, returns nonzero (TRUE) and
     removes the event from the queue.  If the predicate pro-
     cedure finds no match, XCheckIfEvent returns FALSE, and the
     output buffer is flushed. All earlier events stored in the
     queue are not discarded.

     The XPeekIfEvent function returns only when the specified
     predicate procedure returns nonzero (TRUE) for the next
     event in the queue that matches the specified 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 addition-
     al events.






November, 1990                                                  1

XIfEvent(3X)                                         XIfEvent(3X)



   Arguments
     These functions accept the following 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
             Specifies a structure into which the matched event's
             associated structure is copied.

     predicate
             Specifies the procedure that is to be called to
             determine if the next event in the queue matches the
             one specified by the event argument.

SEE ALSO
     XAnyEvent(3X), XNextEvent(3X), XPutBackEvent(3X),
     XSendEvent(3X)

     Xlib - C Language Interface


































2                                                  November, 1990