onRetracted<T extends BusEvent> method

@override Registration onRetracted<T extends BusEvent>(String label, EventHandler<T> handler)

Calls handler on the frame channel for every T that was shown for a step and not produced when the step was run again — a rollback took it back. A frame subscriber that started something for it (a sound, a burst of particles) may stop it here.

A registry that never runs a step again retracts nothing; the default registers nothing to call.

Implementation

@override
Registration onRetracted<T extends BusEvent>(
  String label,
  EventHandler<T> handler,
) => _subscribe<T>(label, BusChannel.frame, handler, retracted: true);