child-shift-with-parent.html

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /layout-instability/child-shift-with-parent.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>Layout Instability: parent/child moved together</title>

<link rel="help" href="https://wicg.github.io/layout-instability/" />

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

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

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

<div id="parent" style="position: relative; width: 100px; height: 100px; border: 100px solid blue">

  <div id="child" style="height: 300px"></div>

</div>

<script>

promise_test(async () => {

  const watcher = new ScoreWatcher;

  // Wait for the initial render to complete.

  await waitForAnimationFrames(2);

  // Modify the position of the div.

  const parent = document.querySelector("#parent");

  parent.style.top = '100px';

  const expectedScore = computeExpectedScore(300 * (400 + 100), 100);

  // Observer fires after the frame is painted.

  assert_equals(watcher.score, 0);

  await watcher.promise;

  assert_equals(watcher.score, expectedScore);

}, 'Parent/child movement.');

</script>