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<!DOCTYPE html>
<head>
<title>Images with loading='lazy' defers images in a hidden area as a result
of negative margins</title>
<link rel="author" title="Dom Farolino" href="mailto:dom@chromium.org">
<link rel="help" href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#lazy-loading-attributes">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
</head>
<body>
<script>
window.negative_margin_test =
async_test("A loading=lazy image that is pulled into an `overflow: hidden` " +
"area by a negative margin will not load because " +
"IntersectionObserver sees it as non-intersecting");
// If the `negative_margin` image in the DOM loads, the test should fail
// immediately.
window.negative_margin_onload =
negative_margin_test.step_func_done(
negative_margin_test.unreached_func("The image with a negative margin " +
"should never load"));
</script>
<div style="width: 200px; height: 200px; overflow: hidden;">
<img id="negative_margin" width="5px"; style="margin-left: -10000vw;"
loading="lazy" src="resources/image.png?loading-lazy-negative-margin"
onload="window.negative_margin_onload()">
</div>
<script>
const intersection_observer_promise = new Promise(resolve => {
function io_callback(entries) {
assert_equals(entries.length, 1);
resolve(entries[0].isIntersecting);
}
const options = {
root: document,
rootMargin: '0px',
threshold: 1.0,
}
const observer = new IntersectionObserver(io_callback, options);
observer.observe(document.querySelector('#negative_margin'));
});
const timeout_promise = new Promise(resolve => {
window.negative_margin_test.step_timeout(resolve, 500);
});
Promise.all([intersection_observer_promise, timeout_promise]).then(
window.negative_margin_test.step_func_done(values => {
assert_equals(values.length, 2);
assert_equals(values[0], false, "The IntersectionObserver sees that " +
"the image does not intersect the " +
"viewport");
}));
</script>
</body>
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