layout-instability/sources-maximpact.html

<!DOCTYPE html>
<title>Layout Instability: source attribution prioritization</title>
<link rel="help" href="https://wicg.github.io/layout-instability/" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/test-adapter.js"></script>
<script src="resources/util.js"></script>
<style>
body { margin: 0; }
#a, #b, #c, #d, #e, #f {
  display: inline-block;
  background: gray;
  min-width: 10px;
  min-height: 10px;
  vertical-align: top;
}
#a { width: 30px; height: 30px; }
#b { width: 20px; height: 20px; }
#c { height: 50px; }
#d { width: 50px; }
#e { width: 40px; height: 30px; }
#f { width: 30px; height: 40px; }
</style>
<div id="grow"></div>
<div id="a"></div
><div id="b"></div
><div id="c"></div
><div id="d"></div
><div id="e"></div
><div id="f"></div>
<script>

let $ = id => document.querySelector(id);

promise_test(async () => {
  const watcher = new ScoreWatcher;

  // Wait for the initial render to complete.
  await waitForAnimationFrames(2);

  $("#grow").style.height = "50px";
  await watcher.promise;

  cls_expect(watcher, {sources: [
    {
      node: $("#a"),
      previousRect: [0, 0, 30, 30],
      currentRect: [0, 50, 30, 30]
    },
    {
      node: $("#f"),
      previousRect: [150, 0, 30, 40],
      currentRect: [150, 50, 30, 40]
    },
    {
      node: $("#c"),
      previousRect: [50, 0, 10, 50],
      currentRect: [50, 50, 10, 50]
    },
    {
      node: $("#d"),
      previousRect: [60, 0, 50, 10],
      currentRect: [60, 50, 50, 10]
    },
    {
      node: $("#e"),
      previousRect: [110, 0, 40, 30],
      currentRect: [110, 50, 40, 30]
    }
  ]});
}, "Source attribution prioritizes by impact.");

</script>