A nobserver to handle “out of band” reset events sent between layers. When the triggering event is detected, a resetattime event is sent to targets; the relevant time is extracted from a sync object.

some_rno add_target target

Add target as a layer to be reset when a trigger event occurs.

some_rno add_sync sync

Set sync as the layer whose current time should be conveyed as the appropriate time for reset to target layers. Under normal circumstances, this should be the layer providing the trigger pattern.