connect

Convenience function to connect to the cancelled signal.

Also handles the race condition that may happen if the cancellable is cancelled right before connecting.

callback is called at most once, either directly at the time of the connect if this is already cancelled, or when this is cancelled in some thread.

data_destroy_func will be called when the handler is disconnected, or immediately if the cancellable is already cancelled.

See cancelled for details on how to use this.

Since GLib 2.40, the lock protecting this is not held when callback is invoked. This lifts a restriction in place for earlier GLib versions which now makes it easier to write cleanup code that unconditionally invokes e.g. cancel.

Parameters:

this	A Cancellable.
callback	The ObjectConstructorFunc to connect.
data	Data to pass to callback.
data_destroy_func	Free function for data or null.

Returns:

The id of the signal handler or 0 if this has already been cancelled.