X Version 11 (1 September 1988) XFlush(XS)
NAME
XFlush, XSync, XEventsQueued, XPending - handle output
buffer or event queue
SYNTAX
XFlush(display)
Display *display;
XSync(display, discard)
Display *display;
Bool discard;
int XEventsQueued(display, mode)
Display *display;
int mode;
int XPending(display)
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 error event received by Xlib, XSync calls
the client application's error handling routine (see section
8.12.2). 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
XIfEvent(XS), XNextEvent(XS), XPutBackEvent(XS)
Xlib - C Language X Interface
(printed 2/12/90) (1 September 1988) XFlush(XS)