NAME

XtAppNextEvent, XtAppPending, XtAppPeekEvent, XtAppProcessEvent, XtDispatchEvent, XtAppMainLoop - query and process events and input

SYNTAX

void XtAppNextEvent(app_context, event_return)
      XtAppContext app_context;
      XEvent *event_return;

Boolean XtAppPeekEvent(app_context, event_return)
      XtAppContext app_context;
      XEvent *event_return;

XtInputMask XtAppPending(app_context)
      XtAppContext app_context;

void XtAppProcessEvent(app_context, mask)
      XtAppContext app_context;
      XtInputMask mask;

Boolean XtDispatchEvent(event)
      XEvent *event;

void XtAppMainLoop(app_context)
      XtAppContext app_context;

ARGUMENTS

app_context

Specifies the application context that identifies the application .

event     Specifies a pointer to the event structure that is
          to be dispatched to the appropriate event handler.

event_return
          Returns the event information to the specified
          event structure.

mask      Specifies what types of events to process.  The
          mask is the bitwise inclusive OR of any combina-
          tion of XtIMXEvent, XtIMTimer, and XtIMAlterna-
          teInput.  As a convenience, the X Toolkit defines
          the symbolic name XtIMAll to be the bitwise
          inclusive OR of all event types.

DESCRIPTION

If no input is on the X input queue, XtAppNextEvent flushes the X output buffer and waits for an event while looking at the other input sources and timeout values and calling any callback procedures triggered by them. This wait time can be used for background processing (see Section 7.8).

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     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, XtAppPeekEvent 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 pending. The value returned is a bit
     mask that is the OR of XtIMXEvent, XtIMTimer, and XtIMAlter-
     nateInput (see XtAppProcessEvent).  If there are no events
     pending, XtAppPending flushes the output buffer and returns
     zero.

     The XtAppProcessEvent function processes one timer, alter-
     nate input, 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.  Usu-
     ally, this procedure is not called by client applications
     (see XtAppMainLoop).  XtAppProcessEvent processes timer
     events by calling any appropriate timer callbacks, alternate
     input by calling any appropriate alternate input 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 routine.  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 implementing the grab semantics for
     XtAddGrab.

     The XtAppMainLoop function first reads the next incoming X
     event by calling XtAppNextEvent and then it dispatches the
     event to the appropriate registered procedure by calling
     XtDispatchEvent.  This constitutes the main loop of X
     Toolkit applications, and, as such, it does not return.

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     Applications are expected to exit in response to some user
     action.  There is nothing special about XtAppMainLoop; it is
     simply an infinite loop that calls XtAppNextEvent and then
     XtDispatchEvent.

     Applications can provide their own version of this loop,
     which tests some global termination flag or tests that the
     number of top-level widgets is larger than zero before cir-
     cling back to the call to XtAppNextEvent.

SEE ALSO

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

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XWIN 3.0               Last change: 9/1/88                 .ie t