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<!doctype html>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>Scrollport is used rather than content rect to compute intersection ratio</title>
<link rel="author" href="" title="Emilio Cobos Álvarez">
<link rel="author" href="" title="Mozilla">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
#root {
overflow: hidden;
position: relative;
box-sizing: border-box;
width: 100px;
height: 100px;
padding: 10px;
#target {
width: 100px;
height: 100px;
background-color: green;
/* Shift into the padding area */
position: relative;
left: -10px;
top: -10px;
<div id="root">
<div id="target"></div>
promise_test(async function(t) {
const target = document.getElementById("target");
assert_true(!!target, "target exists");
const root = document.getElementById("root");
assert_true(!!root, "root exists");
const entries = await new Promise(resolve => {
const observer = new IntersectionObserver(resolve, { root });
assert_equals(entries.length, 1, "Should have one entry.");
assert_equals(entries[0].intersectionRatio, 1, "Should be completely visible.");