ProccessedRadius constructor

ProccessedRadius(SmoothRadius radius, { required double width, required double height, })

Implementation

factory ProccessedRadius(
  SmoothRadius radius, {
  required double width,
  required double height,
}) {
  final cornerSmoothing = radius.cornerSmoothing;
  var cornerRadius = radius.cornerRadius;

  final maxRadius = math.min(width, height) / 2;
  cornerRadius = math.min(cornerRadius, maxRadius);

  // 12.2 from the article
  final p = math.min((1 + cornerSmoothing) * cornerRadius, maxRadius);

  final double angleAlpha, angleBeta;

  if (cornerRadius <= maxRadius / 2) {
    angleBeta = 90 * (1 - cornerSmoothing);
    angleAlpha = 45 * cornerSmoothing;
  } else {
    // When `cornerRadius` is larger and `maxRadius / 2`,
    // these angles also depend on `cornerRadius` and `maxRadius / 2`
    //
    // I did a few tests in Figma and this code generated similar but not identical results
    // `diffRatio` was called `change_percentage` in the orignal code
    final diffRatio = (cornerRadius - maxRadius / 2) / (maxRadius / 2);

    angleBeta = 90 * (1 - cornerSmoothing * (1 - diffRatio));
    angleAlpha = 45 * cornerSmoothing * (1 - diffRatio);
  }

  final angleTheta = (90 - angleBeta) / 2;

  // This was called `h_longest` in the original code
  // In the article this is the distance between 2 control points: P3 and P4
  final p3ToP4Distance =
      cornerRadius * math.tan(vector.radians(angleTheta / 2));

  // This was called `l` in the original code
  final circularSectionLength =
      math.sin(vector.radians(angleBeta / 2)) * cornerRadius * math.sqrt(2);

  // a, b, c and d are from 11.1 in the article
  final c = p3ToP4Distance * math.cos(vector.radians(angleAlpha));
  final d = c * math.tan(vector.radians(angleAlpha));
  final b = (p - circularSectionLength - c - d) / 3;
  final a = 2 * b;

  return ProccessedRadius._(
    a: a,
    b: b,
    c: c,
    d: d,
    p: p,
    width: width,
    height: height,
    radius: radius,
    circularSectionLength: circularSectionLength,
  );
}