css/cssom-view/Element-currentCSSZoom.html

<!doctype html>
<meta charset="utf-8">
<title>Element.currentCSSZoom</title>
<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/cssom-view/#dom-element-currentcsszoom">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id="unzoomed">
  <div id="unzoomedChild"></div>
</div>
<div style="zoom: 2" id="outer">
  <div style="zoom: 2" id="inner">
    <div id="renderedChild"></div>
    <div style="display: none" id="nonRenderedChild"></div>
  </div>
</div>
<script>
test(() => {
  assert_equals(unzoomed.currentCSSZoom, 1, "Unzoomed content");
  assert_equals(outer.currentCSSZoom, 2, "Zoomed content");
  assert_equals(inner.currentCSSZoom, 4, "Effective zoom gets multiplied properly");
  assert_equals(renderedChild.currentCSSZoom, 4, "Effective zoom gets propagated to children");
  assert_equals(nonRenderedChild.currentCSSZoom, 1, "Non-rendered elements return 1 for currentCSSZoom");
}, "Element.currentCSSZoom basic test");

test(() => {
  unzoomed.style.zoom = 2;
  assert_equals(unzoomed.currentCSSZoom, 2, "currentCSSZoom reacts to style changes");
  assert_equals(unzoomedChild.currentCSSZoom, 2, "currentCSSZoom propagates to descendants after style changes");
}, "Element.currentCSSZoom reacts to style changes");
</script>