previewEffectTiming method
Live timing change for an effect overlay; commit with saveState.
Implementation
void previewEffectTiming(String id, Duration start, Duration end) {
final s = start < Duration.zero ? Duration.zero : start;
final e = end - s < const Duration(milliseconds: 200)
? s + const Duration(milliseconds: 200)
: end;
effectController.updateEffectPosition(id, s, e);
notifyListeners();
}