code: function () {
      var mX1 = this._p[0],
        mY1 = this._p[1],
        mX2 = this._p[2],
        mY2 = this._p[3];
      this._precomputed = true;
      if (mX1 !== mY1 || mX2 !== mY2)
        this._calcSampleValues();
    }
docs: Private part