servo/tests/wpt/web-platform-tests/web-animations/testcommon.js

/*
Distributed under both the W3C Test Suite License [1] and the W3C
3-clause BSD License [2]. To contribute to a W3C Test Suite, see the
policies and contribution forms [3].

[1] http://www.w3.org/Consortium/Legal/2008/04-testsuite-license
[2] http://www.w3.org/Consortium/Legal/2008/03-bsd-license
[3] http://www.w3.org/2004/10/27-testcases
 */

"use strict";

var ANIMATION_END_TIME = 1000;
var ANIMATION_TOP_DEFAULT = 300;
var ANIMATION_TOP_0 = 10;
var ANIMATION_TOP_0_5 = 100;
var ANIMATION_TOP_1 = 200;

var KEYFRAMES = [ {
  top : ANIMATION_TOP_0 + 'px',
  offset : 0
}, {
  top : ANIMATION_TOP_0_5 + 'px',
  offset : 1 / 2
}, {
  top : ANIMATION_TOP_1 + 'px',
  offset : 1
} ];

// creates new animation for given target
function newAnimation(animationTarget) {
  animationTarget.style.top = ANIMATION_TOP_DEFAULT + 'px';
  return new Animation(animationTarget, KEYFRAMES, ANIMATION_END_TIME);
}

// creates div element, appends it to the document body and
// removes the created element during test cleanup
function createDiv(test, doc) {
  if (!doc) {
    doc = document;
  }
  var div = doc.createElement('div');
  doc.body.appendChild(div);
  test.add_cleanup(function() {
    removeElement(div);
  });
  return div;
}

// Removes element
function removeElement(element) {
  element.parentNode.removeChild(element);
}

// Returns the type name of given object
function type(object) {
  return Object.prototype.toString.call(object).slice(8, -1);
}

// Convert px unit value to a Number
function pxToNum(str) {
  return Number(String(str).match(/^(-?[\d.]+)px$/)[1]);
}

// Cubic bezier with control points (0, 0), (x1, y1), (x2, y2), and (1, 1).
function cubicBezier(x1, y1, x2, y2) {
  function xForT(t) {
    var omt = 1-t;
    return 3 * omt * omt * t * x1 + 3 * omt * t * t * x2 + t * t * t;
  }

  function yForT(t) {
    var omt = 1-t;
    return 3 * omt * omt * t * y1 + 3 * omt * t * t * y2 + t * t * t;
  }

  function tForX(x) {
    // Binary subdivision.
    var mint = 0, maxt = 1;
    for (var i = 0; i < 30; ++i) {
      var guesst = (mint + maxt) / 2;
      var guessx = xForT(guesst);
      if (x < guessx) {
        maxt = guesst;
      } else {
        mint = guesst;
      }
    }
    return (mint + maxt) / 2;
  }

  return function bezierClosure(x) {
    if (x == 0) {
      return 0;
    }
    if (x == 1) {
      return 1;
    }
    return yForT(tForX(x));
  }
}

function stepEnd(nsteps) {
  return function stepEndClosure(x) {
    return Math.floor(x * nsteps) / nsteps;
  }
}

function stepStart(nsteps) {
  return function stepStartClosure(x) {
    var result = Math.floor(x * nsteps + 1.0) / nsteps;
    return (result > 1.0) ? 1.0 : result;
  }
}