freesewing/packages/sandy/src/shared.js

const draftRingSector = (part, rot, an, radIn, radEx, rotate = false) => {
  let { utils, Point, points, Path } = part.shorthand();

  const roundExtended = (radius, angle = 90) => {
    let arg = utils.deg2rad(angle / 2);

    return (radius * 4 * (1 - Math.cos(arg))) / Math.sin(arg) / 3;
  };

  /**
   * Calculates the distance of the control point for the internal
   * and external arcs using bezierCircleExtended
   */
  let distIn = roundExtended(radIn, an / 2);
  let distEx = roundExtended(radEx, an / 2);
  // The centre of the circles
  points.center = new Point(0, 0);

  /**
   * This function is expected to draft ring sectors for
   * angles up to 180%. Since roundExtended works
   * best for angles until 90º, we generate the ring
   * sector using the half angle and then duplicate it
   */

  /**
   * The first point of the internal arc, situated at
   * a radIn distance below the centre
   */
  points.in1 = points.center.shift(-90, radIn);

  /**
   * The control point for 'in1'. It's situated at a
   * distance $distIn calculated with bezierCircleExtended
   * and the line between it and 'in1' is perpendicular to
   * the line between 'in1' and the centre, so it's
   * shifted in the direction 0º
   */
  points.in1C = points.in1.shift(0, distIn);

  /**
   * The second point of the internal arc, situated at
   * a $radIn distance of the centre in the direction
   * $an/2 - 90º
   */
  points.in2 = points.center.shift(an / 2 - 90, radIn);

  /**
   * The control point for 'in2'. It's situated at a
   * distance $distIn calculated with bezierCircleExtended
   * and the line between it and 'in2' is perpendicular to
   * the line between 'in2' and the centre, so it's
   * shifted in the direction $an/2 + 180º
   */
  points.in2C = points.in2.shift(an / 2 + 180, distIn);

  /**
   * The points for the external arc are generated in the
   * same way, using $radEx and $distEx instead
   */
  points.ex1 = points.center.shift(-90, radEx);
  points.ex1C = points.ex1.shift(0, distEx);
  points.ex2 = points.center.shift(an / 2 - 90, radEx);
  points.ex2C = points.ex2.shift(an / 2 + 180, distEx);

  // Flip all the points to generate the full ring sector
  for (let id of ["in2", "in2C", "in1C", "ex1C", "ex2C", "ex2"])
    points[id + "Flipped"] = points[id].flipX();

  // Rotate all the points an angle rot
  for (let id of [
    "in1",
    "in1C",
    "in2",
    "in2C",
    "ex1",
    "ex1C",
    "ex2",
    "ex2C",
    "in2Flipped",
    "in2CFlipped",
    "in1CFlipped",
    "ex1CFlipped",
    "ex2CFlipped",
    "ex2Flipped"
  ])
    points[id + "Rotated"] = points[id].rotate(rot, points.center);

  if (rotate) {
    // Rotate all points so the line from in1Rotated to ex1Rotated is vertical
    let deg = 270 - points.in2Flipped.angle(points.ex2Flipped);
    for (let id in points) {
      points[id] = points[id].rotate(deg, points.in2Flipped);
    }
  }
  // Return the path of the full ring sector
  return new Path()
    .move(points.in2Flipped)
    .curve(points.in2CFlipped, points.in1CFlipped, points.in1)
    .curve(points.in1C, points.in2C, points.in2)
    .line(points.ex2)
    .curve(points.ex2C, points.ex1C, points.ex1)
    .curve(points.ex1CFlipped, points.ex2CFlipped, points.ex2Flipped)
    .close();
};

export default draftRingSector;