sourceNew

Creates a source that triggers if @cancellable is cancelled and calls its callback of type #GCancellableSourceFunc. This is primarily useful for attaching to another (non-cancellable) source with g_source_add_child_source() to add cancellability to it.

For convenience, you can call this with a null #GCancellable, in which case the source will never trigger.

The new #GSource will hold a reference to the #GCancellable.