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XFlush(3)


NAME

   XFlush, XSync, XEventsQueued, XPending - handle output buffer or event
   queue

SYNTAX

   int XFlush(Display *display);

   int XSync(Display *display, Bool discard);

   int XEventsQueued(Display *display, int mode);

   int XPending(Display *display);

ARGUMENTS

   discard   Specifies a Boolean value that indicates whether XSync
             discards all events on the event queue.

   display   Specifies the connection to the X server.

   mode      Specifies the mode.  You can pass QueuedAlready,
             QueuedAfterFlush, or QueuedAfterReading.

DESCRIPTION

   The XFlush function flushes the output buffer.  Most client
   applications need not use this function because the output buffer is
   automatically flushed as needed by calls to XPending, XNextEvent, and
   XWindowEvent.  Events generated by the server may be enqueued into the
   library's event queue.

   The XSync function flushes the output buffer and then waits until all
   requests have been received and processed by the X server.  Any errors
   generated must be handled by the error handler.  For each protocol
   error received by Xlib, XSync calls the client application's error
   handling routine (see section 11.8.2).  Any events generated by the
   server are enqueued into the library's event queue.

   Finally, if you passed False, XSync does not discard the events in the
   queue.  If you passed True, XSync discards all events in the queue,
   including those events that were on the queue before XSync was called.
   Client applications seldom need to call XSync.

   If mode is QueuedAlready, XEventsQueued returns the number of events
   already in the event queue (and never performs a system call).  If mode
   is QueuedAfterFlush, XEventsQueued returns the number of events already
   in the queue if the number is nonzero.  If there are no events in the
   queue, XEventsQueued flushes the output buffer, attempts to read more
   events out of the application's connection, and returns the number
   read.  If mode is QueuedAfterReading, XEventsQueued returns the number
   of events already in the queue if the number is nonzero.  If there are
   no events in the queue, XEventsQueued attempts to read more events out
   of the application's connection without flushing the output buffer and
   returns the number read.

   XEventsQueued always returns immediately without I/O if there are
   events already in the queue.  XEventsQueued with mode QueuedAfterFlush
   is identical in behavior to XPending.  XEventsQueued with mode
   QueuedAlready is identical to the XQLength function.

   The XPending function returns the number of events that have been
   received from the X server but have not been removed from the event
   queue.  XPending is identical to XEventsQueued with the mode
   QueuedAfterFlush specified.

SEE ALSO

   AllPlanes(3), XIfEvent(3), XNextEvent(3), XPutBackEvent(3)
   Xlib - C Language X Interface



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