NAME

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

SYNTAX

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

       void XtRemoveSignal(XtSignalId id);

       void XtNoticeSignal(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 handling signals within the context
       of the Intrinsics. Prior to establishing an operating system dependent signal handler 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 specified Intrinsics signal handler.
       The client should disable the source of the signal before calling XtRemoveSignal.

SEE ALSO

       XtAppAddTimeOut(3),XtAppAddInput(3),XtAppAddWorkProc(3)
       X Toolkit Intrinsics - C Language Interface
       Xlib - C Language X Interface