content-visibility-auto-offscreen.html

<!DOCTYPE html>
<title>Layout Instability: off-screen content-visibility:auto content</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/util.js"></script>
<script>
// These scripts need to be before the contents because we need to ensure no
// layout shifts during page load.
promise_test(async () => {
  const watcher = new ScoreWatcher;

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

  window.scrollTo(0, 100000 + 100);
  await waitForAnimationFrames(2);

  assert_equals(watcher.score, 0);

  // This should report a layout shift as target is now visible.
  target.style.top = '100100px';

  await watcher.promise;
  const expectedScore = computeExpectedScore(100 * 100, 1);
  assert_approx_equals(watcher.score, expectedScore, 1e-8, "before scroll to top");

  // No new layout shift should be reported when target is scrolled out of screen.
  window.scrollTo(0, 0);
  await waitForAnimationFrames(2);

  assert_approx_equals(watcher.score, expectedScore, 1e-8, "after scroll to top");
}, 'off-screen content-visibility:auto');
</script>
<style>
  .auto {
    content-visibility: auto;
    contain-intrinsic-size: 1px;
    width: 100px;
  }
</style>
<div class=auto>
  <div style="width: 100px; height: 100px; background: blue"></div>
</div>
<div id="target" class=auto style="position: relative; top: 100000px">
  <div style="width: 100px; height: 100px; background: blue"></div>
</div>
chromium/third_party/blink/web_tests/external/wpt/layout-instability/content-visibility-auto-offscreen.html
