XtAppAddSignal(3Xt)

NAME
       XtAppAddSignal, XtRemoveSignal, XtNoticeSignal - register
       and remove a signal source

SYNTAX
       XtSignalId XtAppAddSignal(app_context, proc, client_data)
             XtAppContext app_context;
             XtSignalCallbackProc proc;
             XtPointer client_data;

       void XtRemoveSignal(id)
             XtSignalId id;

       void XtNoticeSignal(id)
             XtSignalId id)

ARGUMENTS
       app_context
                 Specifies the application context.

       client_data
                 Specifies the argument that is to be passed to
                 the specified procedure when a signal has been
                 raised.

       id        Specifies the ID returned from the corresponding
                 XtAppAddSignal call.

       proc      Specifies the procedure that is to be called
                 when the signal has been raised.

DESCRIPTION
       The XtAppAddSignal function initiates a mechanism for han-
       dling signals within the context of the Intrinsics. Prior
       to establishing an operating system dependent signal han-
       dler the application may call XtAppAddSignal and store the
       returned id in a place accessible to the signal handler.

       Upon receipt of a signal from the operating system, the
       application may call XtNoticeSignal passing the id
       returned by the call to XtAppAddSignal.

       XtNoticeSignal is the only Intrinsics function that can
       safely be called from a signal handler. If XtNoticeSignal
       is called multiple times before the Intrinsics are able to
       invoke the registered callback, the callback is only
       called once. Logically the Intrinsics maintain ``pending''
       for each registered callback. This flag is initially False
       and is set to True by XtNoticeSignal; the Intrinsics
       invoke the callback whenever the flag is True, and the
       flag is set to False just before the callback is invoked.

       The XtRemoveSignal function is called to remove the speci-
       fied Intrinsics signal handler. The client should disable

       the source of the signal before calling XtRemoveSignal.

SEE ALSO
       XtAppAddTimeOut(3Xt)XtAppAddInput(3Xt)XtAppAd- 
       dWorkProc(3Xt) 
       X Toolkit Intrinsics - C Language Interface
       Xlib - C Language X Interface