fineui/demo/less/color/bezierEasing.less

.bezierEasingMixin() {
@functions: ~`(function() {
  var NEWTON_ITERATIONS = 4;
  var NEWTON_MIN_SLOPE = 0.001;
  var SUBDIVISION_PRECISION = 0.0000001;
  var SUBDIVISION_MAX_ITERATIONS = 10;

  var kSplineTableSize = 11;
  var kSampleStepSize = 1.0 / (kSplineTableSize - 1.0);

  var float32ArraySupported = typeof Float32Array === 'function';

  function A (aA1, aA2) { return 1.0 - 3.0 * aA2 + 3.0 * aA1; }
  function B (aA1, aA2) { return 3.0 * aA2 - 6.0 * aA1; }
  function C (aA1)      { return 3.0 * aA1; }

  // Returns x(t) given t, x1, and x2, or y(t) given t, y1, and y2.
  function calcBezier (aT, aA1, aA2) { return ((A(aA1, aA2) * aT + B(aA1, aA2)) * aT + C(aA1)) * aT; }

  // Returns dx/dt given t, x1, and x2, or dy/dt given t, y1, and y2.
  function getSlope (aT, aA1, aA2) { return 3.0 * A(aA1, aA2) * aT * aT + 2.0 * B(aA1, aA2) * aT + C(aA1); }

  function binarySubdivide (aX, aA, aB, mX1, mX2) {
    var currentX, currentT, i = 0;
    do {
      currentT = aA + (aB - aA) / 2.0;
      currentX = calcBezier(currentT, mX1, mX2) - aX;
      if (currentX > 0.0) {
        aB = currentT;
      } else {
        aA = currentT;
      }
    } while (Math.abs(currentX) > SUBDIVISION_PRECISION && ++i < SUBDIVISION_MAX_ITERATIONS);
    return currentT;
  }

  function newtonRaphsonIterate (aX, aGuessT, mX1, mX2) {
   for (var i = 0; i < NEWTON_ITERATIONS; ++i) {
     var currentSlope = getSlope(aGuessT, mX1, mX2);
     if (currentSlope === 0.0) {
       return aGuessT;
     }
     var currentX = calcBezier(aGuessT, mX1, mX2) - aX;
     aGuessT -= currentX / currentSlope;
   }
   return aGuessT;
  }

  var BezierEasing = function (mX1, mY1, mX2, mY2) {
    if (!(0 <= mX1 && mX1 <= 1 && 0 <= mX2 && mX2 <= 1)) {
      throw new Error('bezier x values must be in [0, 1] range');
    }

    // Precompute samples table
    var sampleValues = float32ArraySupported ? new Float32Array(kSplineTableSize) : new Array(kSplineTableSize);
    if (mX1 !== mY1 || mX2 !== mY2) {
      for (var i = 0; i < kSplineTableSize; ++i) {
        sampleValues[i] = calcBezier(i * kSampleStepSize, mX1, mX2);
      }
    }

    function getTForX (aX) {
      var intervalStart = 0.0;
      var currentSample = 1;
      var lastSample = kSplineTableSize - 1;

      for (; currentSample !== lastSample && sampleValues[currentSample] <= aX; ++currentSample) {
        intervalStart += kSampleStepSize;
      }
      --currentSample;

      // Interpolate to provide an initial guess for t
      var dist = (aX - sampleValues[currentSample]) / (sampleValues[currentSample + 1] - sampleValues[currentSample]);
      var guessForT = intervalStart + dist * kSampleStepSize;

      var initialSlope = getSlope(guessForT, mX1, mX2);
      if (initialSlope >= NEWTON_MIN_SLOPE) {
        return newtonRaphsonIterate(aX, guessForT, mX1, mX2);
      } else if (initialSlope === 0.0) {
        return guessForT;
      } else {
        return binarySubdivide(aX, intervalStart, intervalStart + kSampleStepSize, mX1, mX2);
      }
    }

    return function BezierEasing (x) {
      if (mX1 === mY1 && mX2 === mY2) {
        return x; // linear
      }
      // Because JavaScript number are imprecise, we should guarantee the extremes are right.
      if (x === 0) {
        return 0;
      }
      if (x === 1) {
        return 1;
      }
      return calcBezier(getTForX(x), mY1, mY2);
    };
  };

  this.colorEasing = BezierEasing(0.26, 0.09, 0.37, 0.18);
})()`;
}
// It is hacky way to make this function will be compiled preferentially by less
// resolve error: `ReferenceError: colorPalette is not defined`
// https://github.com/ant-design/ant-motion/issues/44
.bezierEasingMixin();