<!DOCTYPE html>
<meta charset=utf-8>
<title>The effect value of a keyframe effect: Overlapping 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>
<body>
<div id="log"></div>
<div id="target"></div>
<script>
'use strict';

function assert_opacity_value(opacity, expected, description) {
  return assert_approx_equals(parseFloat(opacity), expected, 0.0001, description);
}

test(t => {
  const div = createDiv(t);
  const anim = div.animate([ { offset: 0, opacity: 0 },
                             { offset: 0, opacity: 0.1 },
                             { offset: 0, opacity: 0.2 },
                             { offset: 1, opacity: 0.8 },
                             { offset: 1, opacity: 0.9 },
                             { offset: 1, opacity: 1 } ],
                           { duration: 1000,
                             easing: 'cubic-bezier(0.5, -0.5, 0.5, 1.5)' });
  assert_opacity_value(getComputedStyle(div).opacity, 0.2,
                'When progress is zero the last keyframe with offset 0 should'
                + ' be used');
  // http://cubic-bezier.com/#.5,-0.5,.5,1.5
  // At t=0.15, the progress should be negative
  anim.currentTime = 150;
  assert_equals(getComputedStyle(div).opacity, '0',
                'When progress is negative, the first keyframe with a 0 offset'
                + ' should be used');
  // At t=0.71, the progress should be just less than 1
  anim.currentTime = 710;
  assert_approx_equals(parseFloat(getComputedStyle(div).opacity), 0.8, 0.01,
                'When progress is just less than 1, the first keyframe with an'
                + ' offset of 1 should be used as the interval endpoint');
  // At t=0.85, the progress should be > 1
  anim.currentTime = 850;
  assert_equals(getComputedStyle(div).opacity, '1',
                'When progress is greater than 1.0, the last keyframe with a 1'
                + ' offset should be used');
  anim.finish();
  assert_equals(getComputedStyle(div).opacity, '1',
                'When progress is equal to 1.0, the last keyframe with a 1'
                + ' offset should be used');
}, 'Overlapping keyframes at 0 and 1 use the appropriate value when the'
   + ' progress is outside the range [0, 1]');

test(t => {
  const div = createDiv(t);
  const anim = div.animate([ { offset: 0, opacity: 0 },
                             { offset: 0.5, opacity: 0.3 },
                             { offset: 0.5, opacity: 0.5 },
                             { offset: 0.5, opacity: 0.7 },
                             { offset: 1, opacity: 1 } ], 1000);
  anim.currentTime = 250;
  assert_opacity_value(getComputedStyle(div).opacity, 0.15,
                'Before the overlap point, the first keyframe from the'
                + ' overlap point should be used as interval endpoint');
  anim.currentTime = 500;
  assert_opacity_value(getComputedStyle(div).opacity, 0.7,
                'At the overlap point, the last keyframe from the'
                + ' overlap point should be used as interval startpoint');
  anim.currentTime = 750;
  assert_opacity_value(getComputedStyle(div).opacity, 0.85,
                'After the overlap point, the last keyframe from the'
                + ' overlap point should be used as interval startpoint');
}, 'Overlapping keyframes between 0 and 1 use the appropriate value on each'
   + ' side of the overlap point');

</script>
</body>
