picture.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:
- /element-timing/picture.html - WPT Dashboard Interop Dashboard

<!DOCTYPE HTML>

<head>

<meta charset=utf-8>

<title>Element Timing: observe an image rendering an alternate picture source</title>

<style>

body {

  margin: 20px;

#square20 {

  width: 80px;

  height: 40px;

</style>

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

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

<script src="resources/element-timing-helpers.js"></script>

<script>

  async_test(function (t) {

    let beforeRender;

    let img;

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

    const observer = new PerformanceObserver(

      t.step_func_done(function(entryList) {

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

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

        // The reported element is the image node, but the image is the

        // alternate source.

        const pathname = window.location.origin + '/images/green-100x50.png';

        checkElement(entry, pathname, 'my_image', 'square20', beforeRender, img);

        // As we use a smaller viewport, the intersection size is smaller

        checkRect(entry, [20, 100, 20, 60]);

        checkNaturalSize(entry, 100, 50);

})

);

    observer.observe({entryTypes: ['element']});

    // We add the image during onload to be sure that the observer is registered

    // in time for it to observe the element timing.

    window.onload = () => {

      // Add image of width equal to 100 and height equal to 50. Use a different

      // color to verify the painted image is the alternate one.

      picture = document.createElement('picture');

      picture.id = 'rectangle';

      picture.setAttribute('elementtiming', 'my_picture');

      source = document.createElement('source');

      source.srcset = '/images/green-100x50.png'

      source.type = 'image/png';

      picture.appendChild(source);

      img = document.createElement('img');

      img.setAttribute('elementtiming', 'my_image');

      img.src = 'resources/square20.jpg'

      img.id = 'square20';

      picture.appendChild(img);

      document.body.appendChild(picture);

      beforeRender = performance.now();

};

  }, 'Element with a rectangular image and an alternate picture image with precedence reports the correct image.');

</script>

</head>