| <!DOCTYPE html> |
| <title>CSS Anchor Positioning: changing @position-try rules invalidates last successful position fallback</title> |
| <link rel="help" href="https://drafts.csswg.org/css-anchor-position/#last-successful-position-fallback"> |
| <script src="/resources/testharness.js"></script> |
| <script src="/resources/testharnessreport.js"></script> |
| <script src="support/test-common.js"></script> |
| <style id="anchor_sheet"> |
| #container { |
| position: relative; |
| width: 400px; |
| height: 400px; |
| background: teal; |
| } |
| #anchor { |
| position: relative; |
| top: 100px; |
| left: 100px; |
| width: 100px; |
| height: 100px; |
| background: red; |
| anchor-name: --a; |
| } |
| #anchored { |
| position-anchor: --a; |
| position-try-fallbacks: --try; |
| position: absolute; |
| width: 100px; |
| height: 200px; |
| position-area: top center; |
| background: lime; |
| } |
| @position-try --try { |
| position-area: bottom center; |
| } |
| </style> |
| <div id="container"> |
| <div id="anchor"></div> |
| <div id="anchored"></div> |
| </div> |
| <script> |
| promise_test(async () => { |
| await waitUntilNextAnimationFrame(); |
| await waitUntilNextAnimationFrame(); |
| assert_equals(anchored.offsetTop, 200); |
| }, "Starts rendering with --try"); |
| |
| promise_test(async () => { |
| anchor.style.top = "150px"; |
| await waitUntilNextAnimationFrame(); |
| await waitUntilNextAnimationFrame(); |
| assert_equals(anchored.offsetTop, 250); |
| }, "No successful position, keep --try"); |
| |
| promise_test(async () => { |
| // Changing @position-try --try {} |
| anchor_sheet.sheet.cssRules[3].style.positionArea = "bottom"; |
| await waitUntilNextAnimationFrame(); |
| await waitUntilNextAnimationFrame(); |
| assert_equals(anchored.offsetTop, -50); |
| }, "No successful position, last successful invalidated by @position-try change"); |
| </script> |
