CSSTransition-currentTime.tentative.html

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This WPT test may be referenced by the following Test IDs:
- /css/css-transitions/CSSTransition-currentTime.tentative.html - WPT Dashboard Interop Dashboard

<!doctype html>

<meta charset=utf-8>

<title>CSSTransition.currentTime</title>

<!-- TODO: Add a more specific link for this once it is specified. -->

<link rel="help" href="https://drafts.csswg.org/css-transitions-2/#csstransition">

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<script src="support/helper.js"></script>

<div id="log"></div>

<script>

'use strict';

const marginLeft = div => parseFloat(getComputedStyle(div).marginLeft);

promise_test(async t => {

  const div = addDiv(t, {

    style: 'margin-left: 100px; transition: margin-left 100s linear 100s',

});

  getComputedStyle(div).marginLeft;

  div.style.marginLeft = '200px';

  const animation = div.getAnimations()[0];

  assert_equals(

    animation.currentTime,

0,

    'currentTime should initially be zero'

);

  await animation.ready;

  const seekTime = 150 * MS_PER_SEC;

  animation.currentTime = seekTime;

  assert_time_equals_literal(

    animation.currentTime,

    seekTime,

    'currentTime is updated'

);

  assert_equals(getComputedStyle(div).marginLeft, '150px');

}, 'currentTime can be used to seek a CSS transition');

promise_test(async t => {

  const div = addDiv(t, {

    style: 'margin-left: 100px; transition: margin-left 100s linear 100s',

});

  const eventWatcher = new EventWatcher(t, div, 'transitionend');

  getComputedStyle(div).marginLeft;

  div.style.marginLeft = '200px';

  const animation = div.getAnimations()[0];

  await animation.ready;

  const marginLeft = () => parseFloat(getComputedStyle(div).marginLeft);

  assert_equals(marginLeft(div), 100);

  animation.currentTime = 100 * MS_PER_SEC;

  assert_equals(marginLeft(div), 100);

  animation.currentTime = 150 * MS_PER_SEC;

  assert_equals(marginLeft(div), 150);

  animation.currentTime = 200 * MS_PER_SEC;

  await eventWatcher.wait_for('transitionend');

  assert_equals(marginLeft(div), 200);

}, 'Skipping forwards through transition');

promise_test(async t => {

  const div = addDiv(t, {

    style: 'margin-left: 100px; transition: margin-left 100s linear 100s',

});

  const eventWatcher = new EventWatcher(t, div, 'transitionend');

  getComputedStyle(div).marginLeft;

  div.style.marginLeft = '200px';

  const animation = div.getAnimations()[0];

  await animation.ready;

  // Unlike in the case of CSS animations, we cannot skip to the end and skip

  // backwards since when we reach the end the transition effect is removed and

  // changes to the Animation object no longer affect the element. For

  // this reason we only skip forwards as far as the 50% through point.

  animation.currentTime = 150 * MS_PER_SEC;

  assert_equals(marginLeft(div), 150);

  animation.currentTime = 100 * MS_PER_SEC;

  assert_equals(marginLeft(div), 100);

}, 'Skipping backwards through transition');

promise_test(async t => {

  const div = addDiv(t, {

    style: 'margin-left: 100px; transition: margin-left 100s linear 100s',

});

  getComputedStyle(div).marginLeft;

  div.style.marginLeft = '200px';

  const animation = div.getAnimations()[0];

  await animation.ready;

  assert_throws_js(

    TypeError,

    () => {

      animation.currentTime = null;

},

    'Expect TypeError exception on trying to set Animation.currentTime to null'

);

}, 'Setting currentTime to null on a CSS transition throws');

test(t => {

  const div = addDiv(t);

  div.style.left = '0px';

  getComputedStyle(div).transitionProperty;

  div.style.transition = 'left 100s ease-in';

  div.style.left = '100px';

  const transition = div.getAnimations()[0];

  // Seek to the middle. Note, this is not equivalent to 50% progress since the

  // timing-function is non-linear.

  transition.currentTime = 50 * MS_PER_SEC;

  const portion = transition.effect.getComputedTiming().progress;

  // Reverse the transition.

  div.style.left = '0px';

  const reversedTransition = div.getAnimations()[0];

  // If the transition reversing behavior does not advance the previous

  // transition to the time set by currentTime, start and end values will both

  // be 0px and no transition will be produced.

  assert_not_equals(reversedTransition, undefined,

                    "A reversed transition is produced");

  const expectedDuration = 100 * MS_PER_SEC * portion;

  assert_approx_equals(

    reversedTransition.effect.getComputedTiming().activeDuration,

    expectedDuration,

1,

    "The reversed transition has correctly reduced duration"

);

}, "Transition reversing behavior respects currentTime and uses the " +

   "transition's current position.");

</script>