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52 lines
2.1 KiB
HTML
52 lines
2.1 KiB
HTML
<!DOCTYPE html>
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<head>
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<title>Images with loading='lazy' load only when in the viewport</title>
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<link rel="author" title="Scott Little" href="mailto:sclittle@chromium.org">
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<link rel="author" title="Dom Farolino" href="mailto:dom@chromium.org">
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<link rel="help" href="https://github.com/scott-little/lazyload">
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<script src="/resources/testharness.js"></script>
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<script src="/resources/testharnessreport.js"></script>
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</head>
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<!--
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Marked as tentative until https://github.com/whatwg/html/pull/3752 is landed.
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-->
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<script>
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const t = async_test("Images with loading='lazy' load only when in the viewport");
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let has_in_viewport_loaded = false;
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let has_window_load_fired = false;
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const in_viewport_img_onload = t.step_func(() => {
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assert_false(has_in_viewport_loaded,
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"The in_viewport element should load only once.");
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has_in_viewport_loaded = true;
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assert_true(document.getElementById("in_viewport").complete);
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document.getElementById("below_viewport").scrollIntoView();
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});
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window.addEventListener("load", t.step_func(() => {
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has_window_load_fired = true;
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}));
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const below_viewport_img_onload = t.step_func_done(() => {
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assert_true(has_in_viewport_loaded,
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"The below-viewport image should not load until it has been " +
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"scrolled into viewport, after the in-viewport image loads");
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assert_true(has_window_load_fired,
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"Below-viewport loading=lazy images should not block the " +
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"window load event from firing");
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});
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</script>
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<body>
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<!-- |in_viewport| takes 2 seconds to load, so that in browsers that don't
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support lazy loading, |below_viewport| finishes before |in_viewport|, and
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the test will dependably fail without relying on a timeout. -->
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<img id="in_viewport" loading="lazy" src="resources/image.png?first&pipe=trickle(d2)"
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onload="in_viewport_img_onload();">
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<div style="height:1000vh;"></div>
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<img id="below_viewport" loading="lazy" src="resources/image.png?second"
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onload="below_viewport_img_onload();">
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</body>
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