gecko-dev/dom/animation/test/testcommon.js

/* Any copyright is dedicated to the Public Domain.
 * http://creativecommons.org/publicdomain/zero/1.0/ */

/**
 * Appends a div to the document body.
 *
 * @param t  The testharness.js Test object. If provided, this will be used
 *           to register a cleanup callback to remove the div when the test
 *           finishes.
 *
 * @param attrs  A dictionary object with attribute names and values to set on
 *               the div.
 */
function addDiv(t, attrs) {
  var div = document.createElement('div');
  if (attrs) {
    for (var attrName in attrs) {
      div.setAttribute(attrName, attrs[attrName]);
    }
  }
  document.body.appendChild(div);
  if (t && typeof t.add_cleanup === 'function') {
    t.add_cleanup(function() {
      if (div.parentNode) {
        div.parentNode.removeChild(div);
      }
    });
  }
  return div;
}

/**
 * Promise wrapper for requestAnimationFrame.
 */
function waitForFrame() {
  return new Promise(function(resolve, reject) {
    window.requestAnimationFrame(resolve);
  });
}

/**
 * Returns a Promise that is resolved after the given number of consecutive
 * animation frames have occured (using requestAnimationFrame callbacks).
 */
function waitForAnimationFrames(frameCount) {
  return new Promise(function(resolve, reject) {
    function handleFrame() {
      if (--frameCount <= 0) {
        resolve();
      } else {
        window.requestAnimationFrame(handleFrame); // wait another frame
      }
    }
    window.requestAnimationFrame(handleFrame);
  });
}

/**
 * Wrapper that takes a sequence of N animations and returns:
 *
 *   Promise.all([animations[0].ready, animations[1].ready, ... animations[N-1].ready]);
 */
function waitForAllAnimations(animations) {
  return Promise.all(animations.map(function(animation) {
    return animation.ready;
  }));
}

/**
 * Flush the computed style for the given element. This is useful, for example,
 * when we are testing a transition and need the initial value of a property
 * to be computed so that when we synchronouslyet set it to a different value
 * we actually get a transition instead of that being the initial value.
 */
function flushComputedStyle(elem) {
  var cs = window.getComputedStyle(elem);
  cs.marginLeft;
}