add-remove-position-fixed.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/add-remove-position-fixed.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>Layout Instability: no shift for adding/removing position:fixed</title>

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

<div id="target" style="width: 100px; height: 100px; background: green;

                        position: absolute; top: 200px"></div>

<div style="height: 2000px"></div>

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

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

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

<script>

promise_test(async () => {

  const watcher = new ScoreWatcher;

  // Wait for the initial render to complete.

  await waitForAnimationFrames(2);

  window.scrollTo(0, 1000);

  target.style.position = 'fixed';

  target.style.top = 0;

  await waitForAnimationFrames(3);

  assert_equals(watcher.score, 0);

  window.scrollTo(0, 100);

  target.style.position = 'absolute';

  target.style.top = '200px';

  await waitForAnimationFrames(3);

  assert_equals(watcher.score, 0);

}, "No shift for adding/removing position:fixed.");

</script>