observe-css-generated-image.html

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This WPT test may be referenced by the following Test IDs:
- /largest-contentful-paint/observe-css-generated-image.html - WPT Dashboard Interop Dashboard

<!doctype html>

<meta charset=utf-8>

<title>Largest Contentful Paint: observe element with css generated image</title>

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

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

<script src="resources/largest-contentful-paint-helpers.js"></script>

<style>

  #target::before {

    content: url('/images/black-rectangle.png');

</style>

<body>

  <p id="target"></p>

  <script>

  setup({"hide_test_state": true});

  async_test(function (t) {

    assert_implements(window.LargestContentfulPaint, "LargestContentfulPaint is not implemented");

    let beforeLoad = performance.now();

    let observedFirstLetter = false;

    const observer = new PerformanceObserver(

      t.step_func_done(function(entryList) {

        const entry = entryList.getEntries()[entryList.getEntries().length -1];

        const url = window.location.origin + '/images/black-rectangle.png';

        checkImage(entry, url, 'target', 0, beforeLoad, ['sizeLowerBound']);

    }));

    observer.observe({entryTypes: ['largest-contentful-paint']});

  }, 'Largest Contentful Paint: CSS generated image is observable.');

  </script>

</body>