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path.js 4.08 KiB
var pi = Math.PI,
    tau = 2 * pi,
    epsilon = 1e-6,
    tauEpsilon = tau - epsilon;
function Path() {
  this._x0 = this._y0 = // start of current subpath
  this._x1 = this._y1 = null; // end of current subpath
  this._ = "";
function path() {
  return new Path;
Path.prototype = path.prototype = {
  constructor: Path,
  moveTo: function(x, y) {
    this._ += "M" + (this._x0 = this._x1 = +x) + "," + (this._y0 = this._y1 = +y);
  closePath: function() {
    if (this._x1 !== null) {
      this._x1 = this._x0, this._y1 = this._y0;
      this._ += "Z";
  lineTo: function(x, y) {
    this._ += "L" + (this._x1 = +x) + "," + (this._y1 = +y);
  quadraticCurveTo: function(x1, y1, x, y) {
    this._ += "Q" + (+x1) + "," + (+y1) + "," + (this._x1 = +x) + "," + (this._y1 = +y);
  bezierCurveTo: function(x1, y1, x2, y2, x, y) {
    this._ += "C" + (+x1) + "," + (+y1) + "," + (+x2) + "," + (+y2) + "," + (this._x1 = +x) + "," + (this._y1 = +y);
  arcTo: function(x1, y1, x2, y2, r) {
    x1 = +x1, y1 = +y1, x2 = +x2, y2 = +y2, r = +r;
    var x0 = this._x1,
        y0 = this._y1,
        x21 = x2 - x1,
        y21 = y2 - y1,
        x01 = x0 - x1,
        y01 = y0 - y1,
        l01_2 = x01 * x01 + y01 * y01;
    // Is the radius negative? Error.
    if (r < 0) throw new Error("negative radius: " + r);
    // Is this path empty? Move to (x1,y1).
    if (this._x1 === null) {
      this._ += "M" + (this._x1 = x1) + "," + (this._y1 = y1);
    // Or, is (x1,y1) coincident with (x0,y0)? Do nothing.
    else if (!(l01_2 > epsilon)) {}
    // Or, are (x0,y0), (x1,y1) and (x2,y2) collinear?
    // Equivalently, is (x1,y1) coincident with (x2,y2)?
    // Or, is the radius zero? Line to (x1,y1).
    else if (!(Math.abs(y01 * x21 - y21 * x01) > epsilon) || !r) {
      this._ += "L" + (this._x1 = x1) + "," + (this._y1 = y1);
    // Otherwise, draw an arc!
    else {
      var x20 = x2 - x0,
          y20 = y2 - y0,
          l21_2 = x21 * x21 + y21 * y21,
          l20_2 = x20 * x20 + y20 * y20,
          l21 = Math.sqrt(l21_2),
l01 = Math.sqrt(l01_2), l = r * Math.tan((pi - Math.acos((l21_2 + l01_2 - l20_2) / (2 * l21 * l01))) / 2), t01 = l / l01, t21 = l / l21; // If the start tangent is not coincident with (x0,y0), line to. if (Math.abs(t01 - 1) > epsilon) { this._ += "L" + (x1 + t01 * x01) + "," + (y1 + t01 * y01); } this._ += "A" + r + "," + r + ",0,0," + (+(y01 * x20 > x01 * y20)) + "," + (this._x1 = x1 + t21 * x21) + "," + (this._y1 = y1 + t21 * y21); } }, arc: function(x, y, r, a0, a1, ccw) { x = +x, y = +y, r = +r; var dx = r * Math.cos(a0), dy = r * Math.sin(a0), x0 = x + dx, y0 = y + dy, cw = 1 ^ ccw, da = ccw ? a0 - a1 : a1 - a0; // Is the radius negative? Error. if (r < 0) throw new Error("negative radius: " + r); // Is this path empty? Move to (x0,y0). if (this._x1 === null) { this._ += "M" + x0 + "," + y0; } // Or, is (x0,y0) not coincident with the previous point? Line to (x0,y0). else if (Math.abs(this._x1 - x0) > epsilon || Math.abs(this._y1 - y0) > epsilon) { this._ += "L" + x0 + "," + y0; } // Is this arc empty? We’re done. if (!r) return; // Does the angle go the wrong way? Flip the direction. if (da < 0) da = da % tau + tau; // Is this a complete circle? Draw two arcs to complete the circle. if (da > tauEpsilon) { this._ += "A" + r + "," + r + ",0,1," + cw + "," + (x - dx) + "," + (y - dy) + "A" + r + "," + r + ",0,1," + cw + "," + (this._x1 = x0) + "," + (this._y1 = y0); } // Is this arc non-empty? Draw an arc! else if (da > epsilon) { this._ += "A" + r + "," + r + ",0," + (+(da >= pi)) + "," + cw + "," + (this._x1 = x + r * Math.cos(a1)) + "," + (this._y1 = y + r * Math.sin(a1)); } }, rect: function(x, y, w, h) { this._ += "M" + (this._x0 = this._x1 = +x) + "," + (this._y0 = this._y1 = +y) + "h" + (+w) + "v" + (+h) + "h" + (-w) + "Z"; }, toString: function() { return this._; } }; export default path;