containertiming-two-overlapping-imgs.html

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<!DOCTYPE HTML>

<meta charset=utf-8>

<title>Container Timing: observe containertiming in a containertiming tree overlapping image children</title>

<body>

<style>

body {

  margin: 0;

</style>

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

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

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

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

<script>

  let beforeRender;

  async_test(function (t) {

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

    const observer = new PerformanceObserver(

      t.step_func_done(function(entryList) {

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

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

        checkContainerEntry(entry, 'div_ct', null, beforeRender)

        checkRect(entry, [0, 150, 0, 150])

        // size is the total area that has been painted, so the more intersection, the less area painted.

        checkContainerSize(entry, 17500);

})

);

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

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

    // in time.

    window.onload = () => {

      // Add a div that is the container timing root

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

      div.setAttribute('containertiming', 'div_ct');

      document.body.appendChild(div);

      // Add two overlapping images

      const img1 = document.createElement('img');

      img1.src = '/container-timing/resources/square100.png';

      img1.setAttribute('id', 'img1_id');

      img1.style.position = 'absolute';

      div.appendChild(img1);

      const img2 = document.createElement('img');

      img2.src = '/container-timing/resources/square100.png';

      img2.setAttribute('id', 'img2_id');

      img2.style.marginLeft = '50px';

      img2.style.marginTop = '50px';

      img2.style.position = 'absolute';

      div.appendChild(img2);

      beforeRender = performance.now();

};

  }, 'Overlapping images report to containertiming.');

</script>

</body>