XtAppNextEvent(3Xt)           X11 SDE 5.4R3.00           XtAppNextEvent(3Xt)


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

SYNTAX
       void XtAppNextEvent(appcontext, eventreturn)
             XtAppContext appcontext;
             XEvent *eventreturn;

       Boolean XtAppPeekEvent(appcontext, eventreturn)
             XtAppContext appcontext;
             XEvent *eventreturn;

       XtInputMask XtAppPending(appcontext)
             XtAppContext appcontext;

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

       Boolean XtDispatchEvent(event)
             XEvent *event;

       void XtAppMainLoop(appcontext)
             XtAppContext appcontext;

ARGUMENTS
       appcontext
                 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.

       eventreturn
                 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 combination of XtIMXEvent,
                 XtIMTimer, and XtIMAlternateInput.  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).

       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



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XtAppNextEvent(3Xt)           X11 SDE 5.4R3.00           XtAppNextEvent(3Xt)


       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 XtIMAlternateInput (see
       XtAppProcessEvent).  If there are no events pending, XtAppPending
       flushes the output buffer and returns zero.

       The XtAppProcessEvent function processes one timer, alternate 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.  Usually, 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.  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 circling back to the call to
       XtAppNextEvent.

SEE ALSO
       X Toolkit Intrinsics - C Language Interface



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XtAppNextEvent(3Xt)           X11 SDE 5.4R3.00           XtAppNextEvent(3Xt)


       Xlib - C Language X Interface
























































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