| <!DOCTYPE html> |
| <title>Layout Instability: parent (with overflow:hidden) and 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: 200px; height: 200px; |
| border: 50px solid blue; overflow: hidden"> |
| <div id="child" style="width: 400px; height: 400px; background: blue"></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'; |
| |
| // Only the parent area should be reported. |
| const expectedScore = computeExpectedScore(300 * (300 + 100), 100); |
| |
| // Observer fires after the frame is painted. |
| assert_equals(watcher.score, 0); |
| await watcher.promise; |
| assert_equals(watcher.score, expectedScore); |
| }, 'Parent (with overflow:hidden) and child moved together.'); |
| |
| </script> |
