Perform the action, usually on a worker thread associated with this
notifier.
Perform the action, usually on a worker thread associated with this
notifier. Results may be posted back to the calling thread, viz.
the conventions documented in org.positronicnet.notifications.Actions.
Synchronously fetch the value being monitored by this Notifier.
Synchronously fetch the value being monitored by this Notifier.
Perform the action, synchronously on the calling thread.
Perform the action, synchronously on the calling thread.
Trait providing common machinery for all library Notifier classes.