hpux man page for xfilterevent

XFilterEvent()															    XFilterEvent()

Name
  XFilterEvent - filter X events for an input method.

Synopsis
  Bool XFilterEvent(event, w)
	XEvent *event;
	Window w;

Arguments
  event     Specifies the event to filter.

  w	    Specifies the window for which the filter is to be applied.

Returns
  True if the event was filtered, else False.

Availability
  Release 5 and later.

Description
  XFilterEvent() passes the specified event to any event filters registered for the specified window.  This allows input methods to intercept
  and respond to events that they are interested in.  Internationalized clients should call XFilterEvent() from their event loops,  generally
  directly  after calling XNextEvent().  If XFilterEvent() returns True, then some input method has filtered the event, and the client should
  not dispatch it any further.	If XFilterEvent() returns False, the client should continue processing it.

  If the window argument is None, XFilterEvent() applies the filter to the window specified in the XEvent structure.  The window argument  is
  provided so that layers above Xlib that do event redirection can indicate to which window an event has been redirected.

  If a grab has occurred in the client, and XFilterEvent() returns True, the client should ungrab the keyboard.

  Input methods register event filters using a non-public mechanism internal to Xlib.

See Also
  XNextEvent().

Xlib - Text Input														    XFilterEvent()