OptionalonOptionalonRender callback (§10 render).
OptionalonVariable-step callback (§10 update).
Unconsumed simulation time in seconds (diagnostics; interpolationAlpha is its normalized form).
Fixed simulation step in seconds. Immutable: changing it mid-run would break replay.
Fixed steps executed by the most recent step call (§10 clamp diagnostics, §34 replay).
Substep clamp (§10). Immutable for the same reason.
Pause flag (§10). Equivalent to timeScale = 0 while set, without clobbering timeScale.
The live time record (§9). The same object is handed to every callback;
copy it with copyTimeState to retain a frame's values.
Simulation time scale (§9). Preserved across pause and resume (§10).
Advances the loop by elapsedRealSeconds of injected wall-clock time.
One call is one frame: frame increments, the accumulator absorbs the
scaled delta, up to maximumSubSteps fixed steps run (each invoking
onFixedStep), the clamp drops any remaining excess into droppedTime,
interpolationAlpha is recomputed, and finally onUpdate then onRender
are invoked. That ordering — onFixedStep* → onUpdate → onRender — is
the §10 contract and holds even when zero fixed steps run.
simulationStep and simulationTime are advanced before each
onFixedStep invocation, so inside the callback they describe the state
the step is producing (WP-1.9 decision). interpolationAlpha is only
meaningful in onUpdate/onRender; during a fixed step it still holds the
previous frame's value and must not be read (§42: interpolation never feeds
back into simulation).
Fixed-step callback (§10
fixedUpdate). Assignable after construction so a composition root can attach the §39 system registry (plan D5) to an already-built scheduler; nothing else about the loop is configurable.