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<!doctype html>
<meta charset=utf-8>
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<link rel="author" title="Mozilla" href="https://mozilla.org/">
<link rel="help" href="https://drafts.csswg.org/css-viewport/">
<title>Dynamic CSS zoom change on iframe</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<iframe srcdoc="Child frame"></iframe>
<script>
const iframe = document.querySelector("iframe");
function promiseDpiChange(win, expected) {
// There might be multiple resize events, wait for the one that changes the device pixel ratio to the expected value.
return new Promise(resolve => {
win.addEventListener("resize", function listener() {
if (win.devicePixelRatio == expected) {
win.removeEventListener("resize", listener);
resolve();
}
});
});
}
promise_test(async function(t) {
if (document.readyState != "complete") {
await new Promise(r => addEventListener("load", r, { once: true }));
}
let parentDpi = window.devicePixelRatio;
let origSize = iframe.getBoundingClientRect();
assert_equals(parentDpi, iframe.contentWindow.devicePixelRatio, "DPI should match between frame and parent");
iframe.style.zoom = 2;
await promiseDpiChange(iframe.contentWindow, 2 * parentDpi);
assert_equals(iframe.contentWindow.devicePixelRatio, 2 * parentDpi, "DPI should have doubled on the frame");
assert_equals(iframe.getBoundingClientRect().width, origSize.width * 2, "Width should have doubled as well");
assert_equals(iframe.getBoundingClientRect().height, origSize.height * 2, "Height should have doubled as well");
});
</script>
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