effect-value-transformed-distance.html

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This WPT test may be referenced by the following Test IDs:
- /web-animations/animation-model/keyframe-effects/effect-value-transformed-distance.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<meta charset=utf-8>

<title>The effect value of a keyframe effect: Calculating the transformed

  distance between keyframes</title>

<link rel="help" href="https://drafts.csswg.org/web-animations/#the-effect-value-of-a-keyframe-animation-effect">

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

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

<script src="../../testcommon.js"></script>

<script src="../../resources/easing-tests.js"></script>

<body>

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

<script>

'use strict';

// Test that applying easing to keyframes is applied as expected

for (const params of gEasingTests) {

  test(t => {

    const target = createDiv(t);

    const anim   = target.animate([ { width: '0px' },

                                    // We put the easing on the second keyframe

                                    // so we can test that it is only applied

                                    // to the specified keyframe.

                                    { width: '100px', easing: params.easing },

                                    { width: '200px' } ],

                                  { duration: 2000,

                                    fill: 'forwards' });

    for (const sampleTime of [0, 999, 1000, 1100, 1500, 2000]) {

      anim.currentTime = sampleTime;

      const portion = (sampleTime - 1000) / 1000;

      const expectedWidth = sampleTime < 1000

                            ? sampleTime / 10 // first segment is linear

                            : 100 + params.easingFunction(portion) * 100;

      assert_approx_equals(parseFloat(getComputedStyle(target).width),

                           expectedWidth,

                           0.02,

                           'The width should be approximately ' +

                           `${expectedWidth} at ${sampleTime}ms`);

  }, `A ${params.desc} on a keyframe affects the resulting style`);

// Test that a linear-equivalent cubic-bezier easing applied to a keyframe does

// not alter (including clamping) the result.

for (const params of gEasingTests) {

  const linearEquivalentEasings = [ 'cubic-bezier(0, 0, 0, 0)',

                                    'cubic-bezier(1, 1, 1, 1)' ];

  test(t => {

    for (const linearEquivalentEasing of linearEquivalentEasings) {

      const timing = { duration: 1000,

                       fill: 'forwards',

                       easing: params.easing };

      const linearTarget = createDiv(t);

      const linearAnim = linearTarget.animate([ { width: '0px' },

                                                { width: '100px' } ],

                                              timing);

      const equivalentTarget = createDiv(t);

      const equivalentAnim =

        equivalentTarget.animate([ { width: '0px',

                                     easing: linearEquivalentEasing },

                                   { width: '100px' } ],

                                 timing);

      for (const sampleTime of [0, 250, 500, 750, 1000]) {

        linearAnim.currentTime = sampleTime;

        equivalentAnim.currentTime = sampleTime;

        assert_equals(getComputedStyle(linearTarget).width,

                      getComputedStyle(equivalentTarget).width,

                      `The 'width' of the animated elements should be equal ` +

                      `at ${sampleTime}ms`);

  }, 'Linear-equivalent cubic-bezier keyframe easing applied to an effect ' +

     `with a ${params.desc} does not alter the result`);

</script>

</body>