XFlush(3) XLIB FUNCTIONS 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 dis-
cards all events on the event queue.
display Specifies the connection to the X server.
mode Specifies the mode. You can pass QueuedAlready, QueuedAfter-
Flush, 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, in-
cluding 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 al-
ready 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 re-
turns the number read.
XEventsQueued always returns immediately without I/O if there are events
already in the queue. XEventsQueued with mode QueuedAfterFlush is iden-
tical 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 re-
ceived 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
X Version 11 libX11 1.8.12 XFlush(3)
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