Method arc

external/.d3.js:6138–6176

(x, y, r, a0, a1, ccw)

    }
  }
  arc(x, y, r, a0, a1, ccw) {
    x = +x, y = +y, r = +r, ccw = !!ccw;

    // Is the radius negative? Error.
    if (r < 0) throw new Error(`negative radius: ${r}`);

    let 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 this path empty? Move to (x0,y0).
    if (this._x1 === null) {
      this._append`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$4 || Math.abs(this._y1 - y0) > epsilon$4) {
      this._append`L${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$3 + tau$3;

    // Is this a complete circle? Draw two arcs to complete the circle.
    if (da > tauEpsilon) {
      this._append`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$4) {
      this._append`A${r},${r},0,${+(da >= pi$2)},${cw},${this._x1 = x + r * Math.cos(a1)},${this._y1 = y + r * Math.sin(a1)}`;
    }
  }
  rect(x, y, w, h) {
    this._append`M${this._x0 = this._x1 = +x},${this._y0 = this._y1 = +y}h${w = +w}v${+h}h${-w}Z`;
  }