MaterialPointArcTween({@required Point begin, @required Point end })

Creates a Tween for animating Points along a circular arc.

The begin and end points are required, cannot be null, and are immutable.

Source 

MaterialPointArcTween({
  @required Point begin,
  @required Point end
}) : super(begin: begin, end: end) {
  assert(begin != null);
  assert(end != null);
  // An explanation with a diagram can be found at https://goo.gl/vMSdRg
  final Offset delta = end - begin;
  final double deltaX = delta.dx.abs();
  final double deltaY = delta.dy.abs();
  final double distanceFromAtoB = delta.distance;
  final Point c = new Point(end.x, begin.y);

  double sweepAngle() => 2.0 * math.asin(distanceFromAtoB / (2.0 * _radius));

  if (deltaX > _kOnAxisDelta && deltaY > _kOnAxisDelta) {
    if (deltaX < deltaY) {
      _radius = distanceFromAtoB * distanceFromAtoB / (c - begin).distance / 2.0;
      _center = new Point(end.x + _radius * (begin.x - end.x).sign, end.y);
      if (begin.x < end.x) {
        _beginAngle = sweepAngle() * (begin.y - end.y).sign;
        _endAngle = 0.0;
      } else {
        _beginAngle = math.PI + sweepAngle() * (end.y - begin.y).sign;
        _endAngle = math.PI;
      }
    } else {
      _radius = distanceFromAtoB * distanceFromAtoB / (c - end).distance / 2.0;
      _center = new Point(begin.x, begin.y + (end.y - begin.y).sign * _radius);
      if (begin.y < end.y) {
        _beginAngle = -math.PI / 2.0;
        _endAngle = _beginAngle + sweepAngle() * (end.x - begin.x).sign;
      } else {
        _beginAngle = math.PI / 2.0;
        _endAngle = _beginAngle + sweepAngle() * (begin.x - end.x).sign;
      }
    }
  }
}