CallbacksCallbacks

Callbacks are definition members that run synchronously at fixed points of each playback. Await Completion shows one in use.

Members

Each callback receives the playback’s TweenInstance<TTarget, TValue> handle; OnUpdate also receives the value it wrote. All default to null.

Member	Runs
OnAdd	At activation, after the start value is captured
OnStart	Once, when the delay ends and playback begins
OnUpdate	After each write
OnEnd	On natural completion
OnCancel	When playback stops early: cancelled, target freed, owner exited, or runner disposed
OnFinally	Last, in every case, including faults

Suppressing callbacks

When ending callbacks touch the target, skip them once it’s gone:

Member	Type	Default	Meaning
SuppressCallbacksWhenTargetInvalid	bool	false	Skip OnEnd, OnCancel, and OnFinally when the target or owner is gone, or playback ended with TargetFreed or OwnerExited

Callback order

1. OnAdd, at activation after capture.
2. OnUpdate with From, only when the fill mode applies it during the delay.
3. OnStart, once, when the delay ends and playback begins.
4. OnUpdate at each sampled timeline boundary and eligible update, plus once more when completion restores the initial value.
5. OnEnd on natural completion, or OnCancel when playback stops early.
6. OnFinally, in every case.

Rules

• The handle’s terminal state is visible before the terminal callbacks run, and each runs at most once.
• A tween cancelled before activation, or whose preparation failed, runs no callbacks.
• A long frame doesn’t replay the callbacks of the cycles it skipped.
• An exception in a callback faults the tween; OnFinally still runs.
• Tweens started in a callback or after an await are independent: they begin on the next eligible update, with no inherited frame time. A Chain links timing instead.