below-viewport-image-loading-lazy-load-event.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/below-viewport-image-loading-lazy-load-event.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<head>

  <title>Below-viewport loading=lazy images do not block the window load event

         when scrolled into viewport</title>

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

  <link rel="author" title="Dom Farolino" href="mailto:dom@chromium.org">

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

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

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

</head>

<body>

  <!-- When this image loads, we will scroll the below-viewport loading=lazy

       images into the viewport. This happens before the window load event is

       fired -->

  <img id="scroll_trigger"

       src="resources/image.png?scroll-trigger&pipe=trickle(d1)"

       onload="scroll_trigger_img.resolve();" onerror="scroll_trigger_img.reject();">

  <!-- This image blocks the window load event for 2 seconds -->

  <img src="resources/image.png?window-load-blocking&pipe=trickle(d2)">

  <div style="height:1000vh"></div>

  <!-- These images must load because they intersect the viewport, but they must

       not block the window load event, because they are loading=lazy -->

  <img id="visible"

       src="resources/image.png?visible&pipe=trickle(d3)" loading="lazy"

       onload="visible_img.resolve();" onerror="visible_img.reject();">

  <img id="visibility_hidden" style="visibility:hidden;"

       src="resources/image.png?visibility_hidden&pipe=trickle(d3)" loading="lazy"

       onload="visibility_hidden_img.resolve();" onerror="visibility_hidden_img.reject();">

</body>

<script>

  const scroll_trigger_img = new ElementLoadPromise("visible");

  const visible_img = new ElementLoadPromise("visible");

  const visibility_hidden_img = new ElementLoadPromise("visibility_hidden");

  async_test(t => {

    let has_window_loaded = false;

    scroll_trigger_img.promise

      .then(t.step_func(() => {

        assert_false(has_window_loaded,

                     "The scroll_trigger image should load before the window " +

                     "load event fires");

        visibility_hidden_img.element().scrollIntoView();

}))

    .catch(t.unreached_func("The scroll_trigger image should load"));

    window.addEventListener("load", t.step_func(() => {

      has_window_loaded = true;

    }));

    Promise.all([visible_img.promise, visibility_hidden_img.promise])

      .then(t.step_func_done(() => {

        assert_true(has_window_loaded,

                    "The window load event should fire before the " +

                    "below-viewport loading=lazy images load");

        assert_true(visible_img.element().complete,

                    "The below-viewport loading=lazy visible image is complete");

        assert_true(visibility_hidden_img.element().complete,

                    "The below-viewport loading=lazy visibility:hidden image is complete");

}))

      .catch(t.unreached_func("The images should load successfully"));

  }, "Below-viewport loading=lazy images do not block the window load event when " +

     "scrolled into viewport");

</script>