image-loading-lazy-base-url.html

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This WPT test may be referenced by the following Test IDs:
- /html/semantics/embedded-content/the-img-element/image-loading-lazy-base-url.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<head>

  <title>Deferred images with loading='lazy' use the original

         base URL specified at parse-time</title>

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

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

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

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

  <base href='/html/semantics/embedded-content/the-img-element/resources/'>

</head>

<script>

  const below_viewport_img = new ElementLoadPromise("below-viewport");

  let has_window_loaded = false;

  async_test(t => {

    // At this point, the below-viewport image's request has been set-up, and

    // its URL is the URL that was parsed relative to the document's base URL

    // at this time. Any changes to the document's base URL from this point

    // forward should not impact the image when we scroll it in-view. This is

    // because the next step in the #updating-the-img-data algorithm is to to

    // fetch the request that has already been set up. Now we'll change the

    // document's base URL, and scroll the image in-view.

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

      const base = document.querySelector('base');

      base.href = '/invalid-url-where-no-subresources-exist/';

      has_window_loaded = true;

      below_viewport_img.element().scrollIntoView();

    }));

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

      assert_true(has_window_loaded,

                  "Below-viewport loading=lazy images do not block the " +

                  "window load event");

    }));

    below_viewport_img.promise.catch(

      t.unreached_func("The image request should not load relative to the " +

                       "current (incorrect) base URL.")

);

  }, "When a loading=lazy image is loaded, it loads relative to the " +

     "document's base URL computed at parse-time.");

</script>

<body>

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

  <img id="below-viewport" src="image.png?base-url" loading="lazy"

       onload="below_viewport_img.resolve()"

       onerror="below_viewport_img.reject()">

</body>