XtAppAddSignal
Section: XT FUNCTIONS (3)
Updated: libXt 1.2.0
Page Index
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