gio:cancellable-connect (cancellable func)

cancellable -- a g:cancellable object
func -- a g:callback callback function

The ID of the signal handler or 0 if cancellable has already been cancelled.

Convenience function to connect to the "cancelled" signal. Also handles the race condition that may happen if the cancellable is cancelled right before connecting.

The func function is called at most once, either directly at the time of the connect if cancellable is already cancelled, or when cancellable is cancelled in some thread.

See the "cancelled" signal for details on how to use this.