| <!DOCTYPE html> |
| |
| <title>CSS Anchor Positioning: basic last successful position fallback on pseudo-elements</title> |
| <link rel="author" title="Kiet Ho" href="mailto:kiet.ho@apple.com"> |
| |
| <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> |
| #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::before { |
| position-anchor: --a; |
| /* |
| We can't use position-area, since there's no way to access offsetTop of |
| pseudo-elements to check for position. Instead, we have to use anchor() |
| and check the computed inset values. |
| */ |
| bottom: anchor(top); |
| left: anchor(left); |
| position-try-fallbacks: flip-block; |
| position: absolute; |
| width: 100px; |
| height: 200px; |
| background: lime; |
| content: ""; |
| } |
| </style> |
| |
| <div id="container"> |
| <div id="anchor"></div> |
| <div id="anchored"></div> |
| </div> |
| |
| <script> |
| promise_test(async () => { |
| await waitUntilNextAnimationFrame(); |
| await waitUntilNextAnimationFrame(); |
| const anchoredStyle = getComputedStyle(anchored, "::before"); |
| assert_equals(anchoredStyle.top, "200px"); |
| }, "Starts rendering with flip-block"); |
| |
| promise_test(async () => { |
| anchor.style.top = "150px"; |
| await waitUntilNextAnimationFrame(); |
| await waitUntilNextAnimationFrame(); |
| const anchoredStyle = getComputedStyle(anchored, "::before"); |
| assert_equals(anchoredStyle.top, "250px"); |
| }, "No successful position, keep flip-block"); |
| |
| promise_test(async () => { |
| anchor.style.top = "200px"; |
| await waitUntilNextAnimationFrame(); |
| await waitUntilNextAnimationFrame(); |
| const anchoredStyle = getComputedStyle(anchored, "::before"); |
| assert_equals(anchoredStyle.top, "0px"); |
| }, "Base position without fallback now successful"); |
| </script> |
| |
