angleTo method

double angleTo(Vector2 target)

Returns the angle formed by component's orientation vector and a vector starting at component's absolute position and ending at target. I.e. how much the current component need to rotate to face the target. This angle is measured in clockwise direction. target should be in absolute/world coordinate system.

Uses nativeAngle to decide the orientation direction of the component. See lookAt to make the component instantly rotate towards target.

Note: If target coincides with the current component's position, then it is treated as being north.

Implementation

double angleTo(Vector2 target) {
  final direction = target - absolutePosition;
  if (direction.isZero()) {
    // If the target coincides with the component's position, we treat it as
    // being north.
    return -nativeAngle % tau;
  }

  final parentAbsoluteScale = _parentAbsoluteScale;
  final targetAngle = math.atan2(
    direction.x * scale.x.sign,
    -direction.y * scale.y.sign,
  );
  final angleDifference = targetAngle - absoluteAngle - nativeAngle;

  final hasOddFlips = parentAbsoluteScale.x.isNegative ^
      parentAbsoluteScale.y.isNegative ^
      scale.x.isNegative ^
      scale.y.isNegative;
  final hasSelfYFlip =
      !parentAbsoluteScale.y.isNegative && scale.y.isNegative;

  final result = (hasOddFlips ? -1 : 1) * angleDifference +
      (hasSelfYFlip ? 1 : 0) * math.pi;
  return result.toNormalizedAngle();
}