One fixed simulation step completed (§10). Fires 0..maximumSubSteps times
per Application.step, after the registered systems ran.
simulationStep/simulationTime describe the step just produced;
interpolationAlpha still holds the previous frame's value and must not be
read here (§42).
The frame's render point (§10). Fires exactly once per step, last.
The variable-rate frame update (§10). Fires exactly once per Application.step, after every fixed step of that call and after world transforms have been resolved (§7).
The §10 main-loop events, as §6b types them.
Every event carries the scheduler's live ReadonlyTimeState — the same object each time, mutated in place by the scheduler (plan D7: the loop allocates nothing per frame). Read what you need during the listener; to retain a frame's values, copy them with
copyTimeStatefrom@fourjs/motion.§10's example listeners destructure
{ fixedDelta }and{ delta, alpha }; those are the pre-1.0 names for §9'sfixedDeltaTime,deltaTime, andinterpolationAlpha, which is what the record actually carries (WP-1.12 decision: one time record, §9's field names, no per-event aliases).