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