image-loading-lazy-below-viewport-dynamic.html

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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:
- /html/semantics/embedded-content/the-img-element/image-loading-lazy-below-viewport-dynamic.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<head>

  <title>Below viewport images with loading='lazy' and changed to

         loading='eager' load and do not block the window load event</title>

  <link rel="author" title="Rob Buis" href="mailto:rbuis@igalia.com">

  <link rel="help" href="https://github.com/scott-little/lazyload">

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

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

</head>

<script>

  const t = async_test("Test that below viewport images with loading='lazy' " +

                       "and changed to loading='eager' load and do not block " +

                       "the window load event.");

  let has_below_viewport_loaded = false;

  let has_window_loaded = false;

  window.addEventListener("load", t.step_func(function() {

    assert_false(has_window_loaded,

                 "The window load event should only fire once.");

    has_window_loaded = true;

  }));

  const below_viewport_img_onload = t.step_func_done(function() {

    assert_false(has_below_viewport_loaded,

               "The in_viewport element should load only once.");

    assert_true(has_window_loaded,

                "The window load event should have fired before " +

                "below_viewport loaded.");

    has_below_viewport_loaded = true;

});

</script>

<body>

  <div style="height:10000px;"></div>

  <img id="below_viewport" src="resources/image.png?below-viewport-dynamic&pipe=trickle(d2)"

       loading="lazy" onload="below_viewport_img_onload();">

  <script>

    assert_false(has_window_loaded,

                "The window load event should not fire before " +

                "changing below_viewport to loading='eager'.");

    document.getElementById("below_viewport").loading = 'eager';

  </script>

</body>