observe-mathml.html

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

<!DOCTYPE HTML>

<meta charset=utf-8>

<title>Largest Contentful Paint: observe element rendered by MathML</title>

<body>

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

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

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

<style>

mathml {

  font-size: 12px;

</style>

<script>

  async_test(function (t) {

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

    let beforeLoad;

    const observer = new PerformanceObserver(

      t.step_func_done(function(entryList) {

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

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

        assert_equals(entry.entryType, 'largest-contentful-paint');

        assert_greater_than_equal(entry.renderTime, beforeRender);

        assert_approx_equals(entry.startTime, entry.renderTime, 0.001,

          'startTime should be equal to renderTime to the precision of 1 millisecond.');

        assert_equals(entry.duration, 0);

        // Some lower bound: height of at least 12 px.

        // Width of at least 100 px.

        assert_greater_than(entry.size, 1200);

        assert_equals(entry.loadTime, 0);

        assert_equals(entry.id, 'mathml');

        assert_equals(entry.url, '');

        assert_equals(entry.element, document.getElementById('mathml'));

})

);

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

    beforeRender = performance.now();

  }, 'Element rendered by MathML is observable');

</script>

<math display="block">

  <mrow>

    <msup>

      <mi id="mathml">This is important text! :)</mi>

    </msup>

  </mrow>

</math>

</body>