child-shift-with-parent-overflow-hidden.html (1173B)
1 <!DOCTYPE html> 2 <title>Layout Instability: parent (with overflow:hidden) and child moved together</title> 3 <link rel="help" href="https://wicg.github.io/layout-instability/" /> 4 <script src="/resources/testharness.js"></script> 5 <script src="/resources/testharnessreport.js"></script> 6 <script src="resources/util.js"></script> 7 <div id="parent" style="position: relative; width: 200px; height: 200px; 8 border: 50px solid blue; overflow: hidden"> 9 <div id="child" style="width: 400px; height: 400px; background: blue"></div> 10 </div> 11 <script> 12 13 promise_test(async () => { 14 const watcher = new ScoreWatcher; 15 16 // Wait for the initial render to complete. 17 await waitForAnimationFrames(2); 18 19 // Modify the position of the div. 20 const parent = document.querySelector("#parent"); 21 parent.style.top = '100px'; 22 23 // Only the parent area should be reported. 24 const expectedScore = computeExpectedScore(300 * (300 + 100), 100); 25 26 // Observer fires after the frame is painted. 27 assert_equals(watcher.score, 0); 28 await watcher.promise; 29 assert_equals(watcher.score, expectedScore); 30 }, 'Parent (with overflow:hidden) and child moved together.'); 31 32 </script>