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<!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>