testing/web-platform/tests/css/css-animations/animation-change-underlying-value-changed-in-flight.html


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<!doctype html>
<meta charset=utf-8>
<title>Changing the underlying value of an animated property with implicit keyframes</title>
<link rel="help" href="https://drafts.csswg.org/css-animations/">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/testcommon.js"></script>
<style>

@keyframes implicit-from {
  to { margin-left: 100px }
}

@keyframes implicit-to {
  from { margin-left: 100px }
}

</style>
<div id="log"></div>
<script>
'use strict';

const implicit_keyframe_test = (animationName, offset) => {
    test(t => {
      const div = addDiv(t);

      // Set up animation to be paused and be at its mid-way point through easing.
      div.style.animation = `${animationName} 10s paused steps(2, start)`;
      const animation = div.getAnimations()[0];

      assert_equals(getComputedStyle(div).marginLeft, "50px", "Computed style before changing the underlying style");

      // Change the underlying value.
      div.style.marginLeft = "200px";
      assert_equals(getComputedStyle(div).marginLeft, "150px", "Computed style after changing the underlying style");
    }, `Changing the underlying value of an animated property with an implicit ${offset}% keyframe`);
};

implicit_keyframe_test("implicit-from", "0");
implicit_keyframe_test("implicit-to", "100");

</script>