MirOS Manual: XtAppMainLoop(3), XtAppNextEvent(3), XtAppPeekEvent(3), XtAppPending(3), XtAppProcessEvent(3), XtDispatchEvent(3)


XtAppNextEvent(3Xt)       XT FUNCTIONS        XtAppNextEvent(3Xt)

NAME

     XtAppNextEvent, XtAppPending, XtAppPeekEvent, XtAppProcess-
     Event, XtDispatchEvent, XtAppMainLoop - 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 combina-
               tion of XtIMXEvent, XtIMTimer, XtIMAlternateInput,
               and XtIMSignal. As a convenience, the X Toolkit
               defines the symbolic name XtIMAll to be the bit-
               wise 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

XFree86                   Version 4.5.0                         1

XtAppNextEvent(3Xt)       XT FUNCTIONS        XtAppNextEvent(3Xt)

     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, XtIMAlterna-
     teInput, and XtIMSignal (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, 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 pro-
     cessed. 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 alter-
     nate input callbacks, signal source by calling any appropri-
     ate signal callbacks, and X events by calling XtDispatch-
     Event.

     When an X event is received, it is passed to XtDispatch-
     Event, 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 unless
     XtAppSetExitFlag is called. Applications are expected to

XFree86                   Version 4.5.0                         2

XtAppNextEvent(3Xt)       XT FUNCTIONS        XtAppNextEvent(3Xt)

     exit in response to some user action. There is nothing spe-
     cial about XtAppMainLoop; it is simply an loop that calls
     XtAppNextEvent and then XtDispatchEvent, until XtAppGetExit-
     Flag() 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 cir-
     cling back to the call to XtAppNextEvent.

SEE ALSO

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

XFree86                   Version 4.5.0                         3

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