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XtAppNextEvent(3)		 XT FUNCTIONS		     XtAppNextEvent(3)

NAME
       XtAppNextEvent, XtAppPending, XtAppPeekEvent, XtAppProcessEvent,	Xt-
       DispatchEvent, XtAppMainLoop - query and	process	events and input

SYNTAX
       #include	<X11/Intrinsic.h>

       void XtAppNextEvent(XtAppContext	app_context, XEvent *event_return);

       Boolean XtAppPeekEvent(XtAppContext app_context,	XEvent *event_return);

       XtInputMask XtAppPending(XtAppContext app_context);

       void XtAppProcessEvent(XtAppContext app_context,	XtInputMask mask);

       Boolean XtDispatchEvent(XEvent *event);

       void XtAppMainLoop(XtAppContext app_context);

ARGUMENTS
       app_context
		 Specifies the application context that	identifies the appli-
		 cation.

       event	 Specifies a pointer to	the event structure that is to be dis-
		 patched to the	appropriate event handler.

       event_return
		 Returns the event information to the specified	event struc-
		 ture.

       mask	 Specifies what	types of events	to process.  The mask is the
		 bitwise inclusive OR of any combination of XtIMXEvent,	XtIM-
		 Timer,	XtIMAlternateInput, and	XtIMSignal.  As	a convenience,
		 the X Toolkit defines the symbolic name XtIMAll to be the
		 bitwise inclusive OR of all event types.

DESCRIPTION
       If the X	event queue is empty, XtAppNextEvent flushes the X output buf-
       fers of each Display in the application context and waits for an	event
       while looking at	the other input	sources, timeout timeout values, and
       signal handlers and calling any callback	procedures triggered by	them.
       This wait time can be used for background processing (see Section 7.8).

       If there	is an event in the queue, XtAppPeekEvent fills in the event
       and returns a nonzero value.  If	no X input is on the queue, XtAppPeek-
       Event flushes the output	buffer and blocks until	input is available
       (possibly calling some timeout callbacks	in the process).  If the input
       is an event, XtAppPeekEvent fills in the	event and returns a nonzero
       value.  Otherwise, the input is for an alternate	input source, and
       XtAppPeekEvent returns zero.

       The XtAppPending	function returns a nonzero value if there are events
       pending from the	X server, timer	pending, or other input	sources	pend-
       ing.  The value returned	is a bit mask that is the OR of	XtIMXEvent,
       XtIMTimer, XtIMAlternateInput, and XtIMSignal (see XtAppProcessEvent).
       If there	are no events pending, XtAppPending flushes the	output buffer
       and returns zero.

       The XtAppProcessEvent function processes	one timer, alternate input,
       signal source, or X event.  If there is nothing of the appropriate type
       to process, XtAppProcessEvent blocks until there	is.  If	there is more
       than one	type of	thing available	to process, it is undefined which will
       get processed.  Usually,	this procedure is not called by	client appli-
       cations (see XtAppMainLoop).  XtAppProcessEvent processes timer events
       by calling any appropriate timer	callbacks, alternate input by calling
       any appropriate alternate input callbacks, signal source	by calling any
       appropriate signal callbacks, and X events by calling XtDispatchEvent.

       When an X event is received, it is passed to XtDispatchEvent, which
       calls the appropriate event handlers and	passes them the	widget,	the
       event, and client-specific data registered with each procedure.	If
       there are no handlers for that event registered,	the event is ignored
       and the dispatcher simply returns.  The order in	which the handlers are
       called is undefined.

       The XtDispatchEvent function sends those	events to the event handler
       functions that have been	previously registered with the dispatch	rou-
       tine.  XtDispatchEvent returns True if it dispatched the	event to some
       handler and False if it found no	handler	to dispatch the	event to.  The
       most common use of XtDispatchEvent is to	dispatch events	acquired with
       the XtAppNextEvent procedure.  However, it also can be used to dispatch
       user-constructed	events.	 XtDispatchEvent also is responsible for im-
       plementing the grab semantics for XtAddGrab.

       The XtAppMainLoop function processes events using XtAppProcessEvent,
       varying the mask	parameter and using XtAppPending to ensure that	it has
       a chance	to handle events of all	types, i.e., X events, timer events,
       input events and	signal sources.	 This constitutes the main loop	of X
       Toolkit applications, and, as such, it does not return unless XtAppSe-
       tExitFlag is called.  Applications are expected to exit in response to
       some user action.  There	is nothing special about XtAppMainLoop;	it is
       simply an loop that processes events until XtAppGetExitFlag() returns
       true.

       Applications can	provide	their own version of this loop,	which tests
       some global termination flag or tests that the number of	top-level wid-
       gets is larger than zero	before circling	back for the next event.

SEE ALSO
       X Toolkit Intrinsics - C	Language Interface
       Xlib - C	Language X Interface

X Version 11			  libXt	1.2.0		     XtAppNextEvent(3)

NAME | SYNTAX | ARGUMENTS | DESCRIPTION | SEE ALSO

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