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XtAppNextEvent(3)                               XT FUNCTIONS                               XtAppNextEvent(3)



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

SYNTAX
       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 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
                 combination of XtIMXEvent, XtIMTimer, XtIMAlternateInput, and XtIMSignal.  As a conve-nience, convenience,
                 nience, 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 buffers 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, XtAppPeekEvent flushes the output buffer and blocks until input is avail-able available
       able (possibly calling some timeout callbacks in the process).  If the input is an event, XtAppPeek-Event XtAppPeekEvent
       Event 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, 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 applications (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 han-dlers handlers
       dlers 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 previ-ously previously
       ously 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 implement-ing implementing
       ing 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 unless XtAppSe-tExitFlag XtAppSetExitFlag
       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 calls XtAppNextEvent and then Xt-DispatchEvent, XtDispatchEvent,
       DispatchEvent, 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 widgets is larger than zero before circling back to the call to
       XtAppNextEvent.

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



X Version 11                                     libXt 1.0.5                               XtAppNextEvent(3)