<!DOCTYPE html> <title>Layout Instability: movement of fixed position</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="target" style="position: fixed; top: 100px; width: 300px; height: 200px; background: yellow"> </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. target.style.top = '200px'; const expectedScore = computeExpectedScore(300 * (200 + 100), 100); // Observer fires after the frame is painted. assert_equals(watcher.score, 0); await watcher.promise; assert_equals(watcher.score, expectedScore); }, 'Movement of fixed position'); </script>