testing/web-platform/tests/html/semantics/embedded-content/the-img-element/image-loading-lazy-load-event.html

   1 <!DOCTYPE html>
   2 <head>
   3   <title>In-viewport loading=lazy images do not block the window load event</title>
   4   <link rel="author" title="Rob Buis" href="mailto:rbuis@igalia.com">
   5   <link rel="author" title="Dom Farolino" href="mailto:dom@chromium.org">
   6   <script src="/resources/testharness.js"></script>
   7   <script src="/resources/testharnessreport.js"></script>
   8   <script src="common.js"></script>
   9 </head>
  10
  11 <body>
  12   <!-- This image blocks the window load event for 1 second -->
  13   <img src="resources/image.png?window-load-blocking&pipe=trickle(d1)">
  14
  15   <!-- These images must load because they intersect the viewport, but they must
  16        not block the window load event, because they are loading=lazy -->
  17   <img id="visible"
  18        src="resources/image.png?visible&pipe=trickle(d3)" loading="lazy"
  19        onload="visible_img.resolve();" onerror="visible_img.reject();">
  20   <img id="visibility_hidden" style="visibility:hidden;"
  21        src="resources/image.png?visibility_hidden&pipe=trickle(d3)" loading="lazy"
  22        onload="visibility_hidden_img.resolve();" onerror="visibility_hidden_img.reject();">
  23 </body>
  24
  25 <script>
  26   const visible_img = new ElementLoadPromise("visible");
  27   const visibility_hidden_img = new ElementLoadPromise("visibility_hidden");
  28
  29   async_test(t => {
  30
  31     let has_window_loaded = false;
  32     window.addEventListener("load", t.step_func(() => {
  33       has_window_loaded = true;
  34     }));
  35
  36     Promise.all([visible_img.promise, visibility_hidden_img.promise])
  37       .then(t.step_func_done(() => {
  38         assert_true(has_window_loaded,
  39                     "The window load event should fire before the " +
  40                     "in-viewport loading=lazy images load");
  41         assert_true(visible_img.element().complete,
  42                     "The in-viewport loading=lazy visible image is complete");
  43         assert_true(visibility_hidden_img.element().complete,
  44                     "The in-viewport loading=lazy visibility:hidden image is " +
  45                     "complete");
  46       }))
  47       .catch(t.unreached_func("The images should load successfully"));
  48
  49   }, "In-viewport loading=lazy images do not block the window load event");
  50 </script>
  51