tor-browser

The Tor Browser
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last-successful-pseudo-element-basic.html (2162B)

      1 <!DOCTYPE html>
      2 
      3 <title>CSS Anchor Positioning: basic last successful position fallback on pseudo-elements</title>
      4 <link rel="author" title="Kiet Ho" href="mailto:kiet.ho@apple.com">
      5 
      6 <link rel="help" href="https://drafts.csswg.org/css-anchor-position/#last-successful-position-fallback">
      7 
      8 <script src="/resources/testharness.js"></script>
      9 <script src="/resources/testharnessreport.js"></script>
     10 <script src="support/test-common.js"></script>
     11 
     12 <style>
     13  #container {
     14    position: relative;
     15    width: 400px;
     16    height: 400px;
     17    background: teal;
     18  }
     19  #anchor {
     20    position: relative;
     21    top: 100px;
     22    left: 100px;
     23    width: 100px;
     24    height: 100px;
     25    background: red;
     26    anchor-name: --a;
     27  }
     28  #anchored::before {
     29    position-anchor: --a;
     30    /*
     31        We can't use position-area, since there's no way to access offsetTop of
     32        pseudo-elements to check for position. Instead, we have to use anchor()
     33        and check the computed inset values.
     34    */
     35    bottom: anchor(top);
     36    left: anchor(left);
     37    position-try-fallbacks: flip-block;
     38    position: absolute;
     39    width: 100px;
     40    height: 200px;
     41    background: lime;
     42    content: "";
     43  }
     44 </style>
     45 
     46 <div id="container">
     47  <div id="anchor"></div>
     48  <div id="anchored"></div>
     49 </div>
     50 
     51 <script>
     52  promise_test(async () => {
     53    await waitUntilNextAnimationFrame();
     54    await waitUntilNextAnimationFrame();
     55    const anchoredStyle = getComputedStyle(anchored, "::before");
     56    assert_equals(anchoredStyle.top, "200px");
     57  }, "Starts rendering with flip-block");
     58 
     59  promise_test(async () => {
     60    anchor.style.top = "150px";
     61    await waitUntilNextAnimationFrame();
     62    await waitUntilNextAnimationFrame();
     63    const anchoredStyle = getComputedStyle(anchored, "::before");
     64    assert_equals(anchoredStyle.top, "250px");
     65  }, "No successful position, keep flip-block");
     66 
     67  promise_test(async () => {
     68    anchor.style.top = "200px";
     69    await waitUntilNextAnimationFrame();
     70    await waitUntilNextAnimationFrame();
     71    const anchoredStyle = getComputedStyle(anchored, "::before");
     72    assert_equals(anchoredStyle.top, "0px");
     73  }, "Base position without fallback now successful");
     74 </script>