hpux man page for xflush

XFlush()																  XFlush()

Name
  XFlush - send all queued requests to the server.

Synopsis
  XFlush(display)
	Display *display;

Arguments
  display   Specifies a connection to an X server; returned from XOpenDisplay().

Description
  XFlush() sends to the server ("flushes") all requests that have been buffered but not yet sent.

  Flushing  is	done  automatically  when input is read if no matching events are in Xlib's queue (with XPending(), XNextEvent(), or XWindow-
  Event(), etc.), or when a call is made that gets information from the server (such as XQueryPointer(), XGetFontInfo) so XFlush() is  seldom
  needed.  It is used when the buffer must be flushed before any of these calls are reached.

  For more information, see Volume One, Chapter 2, X Concepts, and Chapter 3, Basic Window Program.

See Also
  XSync().

Xlib - Output Buffer															  XFlush()