XFlush(3) XLIB FUNCTIONS XFlush(3)NAME
XFlush, XSync, XEventsQueued, XPending - handle output buffer or event
int XFlush(Display *display);
int XSync(Display *display, Bool discard);
int XEventsQueued(Display *display, int mode);
int XPending(Display *display);
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.
The XFlush function flushes the output buffer. Most client applica‐
tions need not use this function because the output buffer is automati‐
cally flushed as needed by calls to XPending, XNextEvent, and XWindow‐
Event. 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 han‐
dling 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
SEE ALSOAllPlanes(3), XIfEvent(3), XNextEvent(3), XPutBackEvent(3)
Xlib - C Language X Interface
X Version 11 libX11 1.3.5 XFlush(3)