transform.html - mozsearch

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /layout-instability/transform.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>Layout Instability: shift inside a transformed container</title>

<link rel="help" href="https://wicg.github.io/layout-instability/" />

<style>

body { margin: 0; }

#container { transform: translateX(-300px) translateY(-40px); }

#shifter { position: relative; width: 600px; height: 140px; background: blue; }

</style>

<div id="container">

  <div id="shifter"></div>

</div>

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<script src="resources/util.js"></script>

<script>

promise_test(async () => {

  const watcher = new ScoreWatcher;

  // Wait for the initial render to complete.

  await waitForAnimationFrames(2);

  // Modify the position of the div.

  document.querySelector("#shifter").style = "top: 60px";

  // The shifter has size 600 x 140, but the container's transform

  // reduces its viewport overlap.

  const expectedScore = computeExpectedScore(

      (600 - 300) * (140 - 40 + 60), 60);

  await watcher.promise;

  assert_equals(watcher.score, expectedScore);

}, 'Transformed container.');

</script>