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 XWIN 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 indi-
     cates 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 struc-
     ture.

     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

XWIN 3.0               Last change: 9/1/88                 .ie t

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

XWIN 3.0               Last change: 9/1/88                 .ie t

XWIN 3.0               Last change: 9/1/88                 .ie t