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XtAppAddSignal(3)                XT FUNCTIONS                XtAppAddSignal(3)

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

SYNTAX
       #include <X11/Intrinsic.h>

       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

X Version 11                      libXt 1.2.1                XtAppAddSignal(3)