loadTime-after-appendChild.html

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This WPT test may be referenced by the following Test IDs:
- /largest-contentful-paint/loadTime-after-appendChild.html - WPT Dashboard Interop Dashboard

<!DOCTYPE HTML>

<meta charset=utf-8>

<title>Largest Contentful Paint: delayed appended image.</title>

<body>

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

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

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

<script>

  setup({"hide_test_state": true});

  async_test(function (t) {

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

    let beforeLoad;

    const observer = new PerformanceObserver(

      t.step_func_done(entryList => {

        assert_equals(entryList.getEntries().length, 1);

        const entry = entryList.getEntries()[0];

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

        // blue.png is 100 by 50.

        const size = 100 * 50;

        checkImage(entry, url, 'image_id', size, beforeLoad);

})

);

    observer.observe({type: 'largest-contentful-paint', buffered: true});

    const img = document.createElement('img');

    img.src = '/images/black-rectangle.png';

    img.id = 'image_id';

    t.step_timeout(() => {

      beforeLoad = performance.now();

      document.getElementById('image_div').appendChild(img);

    }, 200)

  }, 'Image loadTime occurs after appendChild is called.');

</script>

<div id='image_div'></div>

</body>