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- This WPT test may be referenced by the following Test IDs:
- /css/css-transitions/changing-while-transition-002.html - WPT Dashboard Interop Dashboard
<!doctype html>
<html>
<head>
<meta charset=utf-8>
<title>CSS Transitions Test: behavior when transition-timing-function changes while transitioning</title>
<meta name="assert" content="Checks a change to the transition-timing-function
property does not affect an in-flight transition">
<link rel="help" title="3. Starting of transitions" href="https://drafts.csswg.org/css-transitions/#starting">
<script src="/resources/testharness.js" type="text/javascript"></script>
<script src="/resources/testharnessreport.js" type="text/javascript"></script>
<script src="./support/helper.js" type="text/javascript"></script>
</head>
<body>
<div id="log"></div>
<script>
promise_test(async t => {
// Start a transition 50% of the way through with a linear timing function
const div = addDiv(t, {
style: 'transition: height 100s -50s linear; height: 0px',
});
getComputedStyle(div).height;
div.style.height = '100px';
assert_equals(
getComputedStyle(div).height,
'50px',
'Transition should be initially 50% complete'
);
// Update the timing function
div.style.transitionTimingFunction = 'steps(1, end)';
// If the change to the transition-timing-function was reflected, the
// computed height would now be '0px'.
assert_equals(
getComputedStyle(div).height,
'50px',
'Even after updating the transition-timing-function, the transition should be 50% complete'
);
// Wait a frame just to be sure that the changed timing function is not later
// updated.
await waitForFrame();
assert_greater_than_equal(
parseInt(getComputedStyle(div).height),
50,
'Even in the next frame the updated transition-timing-function should not apply'
);
}, 'Changes to transition-timing-function should not affect in-flight transitions');
</script>
</body>
</html>