| Steve Kobes | 1a09247 | 2019-11-25 15:54:13 | [diff] [blame] | 1 | <!DOCTYPE html> |
| 2 | <title>Layout Instability: element with compositing layer hint</title> |
| 3 | <link rel="help" href="https://wicg.github.io/layout-instability/" /> |
| 4 | <style> |
| 5 | |
| 6 | #shift { |
| 7 | position: relative; |
| 8 | width: 500px; |
| 9 | height: 200px; |
| 10 | background: yellow; |
| 11 | } |
| 12 | #container { |
| 13 | position: absolute; |
| 14 | width: 350px; |
| 15 | height: 400px; |
| 16 | right: 50px; |
| 17 | top: 100px; |
| 18 | background: #ccc; |
| 19 | } |
| 20 | .promote { will-change: transform; } |
| 21 | |
| 22 | </style> |
| 23 | <div id="container" class="promote"> |
| 24 | <div id="space"></div> |
| 25 | <div id="shift" class="promote"></div> |
| 26 | </div> |
| 27 | <script src="/resources/testharness.js"></script> |
| 28 | <script src="/resources/testharnessreport.js"></script> |
| 29 | <script src="resources/util.js"></script> |
| 30 | <script> |
| 31 | |
| 32 | promise_test(async () => { |
| 33 | const watcher = new ScoreWatcher; |
| 34 | |
| 35 | // Wait for the initial render to complete. |
| 36 | await waitForAnimationFrames(2); |
| 37 | |
| 38 | // Induce a shift. |
| 39 | document.querySelector("#space").style = "height: 100px"; |
| 40 | |
| 41 | // #shift is 400x200 after viewport intersection with correct application of |
| 42 | // composited #container offset, and 100px lower after shifting, so impact |
| 43 | // region is 400 * (200 + 100). |
| 44 | const expectedScore = computeExpectedScore(400 * (200 + 100), 100); |
| 45 | |
| 46 | // Observer fires after the frame is painted. |
| 47 | assert_equals(watcher.score, 0); |
| 48 | await watcher.promise; |
| 49 | assert_equals(watcher.score, expectedScore); |
| 50 | }, "Element with compositing layer hint."); |
| 51 | |
| 52 | </script> |
