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<!DOCTYPE html>
<head>
<title>A loading=lazy image in a below-viewport cross-origin iframe loads only
when the cross-origin iframe is scrolled into view</title>
<link rel="help" href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#lazy-loading-attributes">
<link rel="author" title="Dom Farolino" href="mailto:dom@chromium.org">
<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="/common/get-host-info.sub.js"></script>
</head>
<div style="height:1000vh;"></div>
<iframe id="iframe" width="500px" height="500px"></iframe>
<script>
promise_test(t => {
iframe.src =
get_host_info().HTTP_NOTSAMESITE_ORIGIN +
new URL("resources/", self.location).pathname +
"image-loading-lazy-in-viewport.html";
// Wait for the frame to report that its window load event fired.
return new Promise(resolve => {
window.addEventListener("message",
event => resolve(event.data), {once: true});
}).then(iframe_message => {
assert_equals(iframe_message, "window_loaded",
"The loading=lazy image should not block the iframe's load " +
"event");
// Scroll the iframe into view, which also puts the image into view.
iframe.scrollIntoView();
return new Promise(resolve => {
window.addEventListener("message", event => resolve(event.data));
});
}).then(iframe_message => {
assert_equals(iframe_message, "image_loaded",
"The below-viewport loading=lazy image should load only " +
"once scrolled into the viewport");
}); // new Promise().
}); // promise_test().
</script>
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