advance method Null safety

bool advance(double elapsedSeconds)

Implementation

bool advance(double elapsedSeconds) {
  var deltaSeconds = elapsedSeconds * animation.speed * _direction;
  _lastTotalTime = _totalTime;
  _totalTime += deltaSeconds;
  _time += deltaSeconds;

  double frames = _time * animation.fps;

  var start = animation.enableWorkArea ? animation.workStart : 0;
  var end = animation.enableWorkArea ? animation.workEnd : animation.duration;
  var range = end - start;

  bool keepGoing = true;
  _didLoop = false;
  _spilledTime = 0;

  switch (animation.loop) {
    case Loop.oneShot:
      if (frames > end) {
        keepGoing = false;
        _spilledTime = (frames - end) / animation.fps;
        frames = end.toDouble();
        _time = frames / animation.fps;
        _didLoop = true;
      }
      break;
    case Loop.loop:
      if (frames >= end) {
        _spilledTime = (frames - end) / animation.fps;
        frames = _time * animation.fps;
        frames = start + (frames - start) % range;
        _time = frames / animation.fps;
        _didLoop = true;
      }
      break;
    case Loop.pingPong:
      // ignore: literal_only_boolean_expressions
      while (true) {
        if (_direction == 1 && frames >= end) {
          _spilledTime = (frames - end) / animation.fps;
          _direction = -1;
          frames = end + (end - frames);
          _time = frames / animation.fps;
          _didLoop = true;
        } else if (_direction == -1 && frames < start) {
          _spilledTime = (start - frames) / animation.fps;
          _direction = 1;
          frames = start + (start - frames);
          _time = frames / animation.fps;
          _didLoop = true;
        } else {
          // we're within the range, we can stop fixing. We do this in a
          // loop to fix conditions when time has advanced so far that we've
          // ping-ponged back and forth a few times in a single frame. We
          // want to accomodate for this in cases where animations are not
          // advanced on regular intervals.
          break;
        }
      }
      break;
  }
  return keepGoing;
}