reverse method
Starts animating backward (toward lowerBound).
Returns a Cmd that schedules the first animation frame tick.
Implementation
Cmd reverse({double? from, Curve curve = Curves.linear}) {
if (from != null) _value = from.clamp(lowerBound, upperBound);
_targetValue = lowerBound;
_startValue = _value;
_curve = curve;
_status = AnimationStatus.reverse;
_startTime = null;
_repeating = false;
_notifyStatusListeners();
return _scheduleTick();
}