<!DOCTYPE html>
<title>Tests CSS transition of anchor() and anchor-size() functions</title>
<link rel="help" href="https://drafts4.csswg.org/css-anchor-position-1/">
<link rel="help" href="https://github.com/w3c/csswg-drafts/issues/8180"></script>
<link rel="author" href="mailto:xiaochengh@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<style>
body {
  margin: 0;
}

#anchor1 {
  margin-left: 0px;
  margin-top: 0px;
  width: 200px;
  height: 100px;
  background: orange;
  anchor-name: --a1;
}

#anchor2 {
  margin-left: 400px;
  margin-top: 200px;
  width: 100px;
  height: 200px;
  background: orange;
  anchor-name: --a2;
}

#target {
  position: fixed;
  width: 100px;
  height: 100px;
  background-color: lime;
  transition: all 10s -5s linear;
}

#target.before {
  top: anchor(--a1 top);
  left: anchor(--a1 right);
  width: anchor-size(--a1 width);
  height: anchor-size(--a1 height);
}

#target.after {
  top: anchor(--a2 bottom);
  left: anchor(--a2 left);
  width: anchor-size(--a2 width);
  height: anchor-size(--a2 height);
}
</style>

<div id="anchor1"></div>
<div id="anchor2"></div>
<div id="target" class="before"></div>

<script>
setup(() => {
  // Forces layout
  target.offsetLeft;
  // Triggers transition starting at 50% immediately
  target.classList.remove('before');
  target.classList.add('after');
});

test(() => {
  assert_equals(target.offsetLeft, 300);
  assert_equals(target.offsetTop, 250);
}, 'Transition of anchor() when changing target anchor element name');

test(() => {
  assert_equals(target.offsetWidth, 150);
  assert_equals(target.offsetHeight, 150);
}, 'Transition of anchor-size() when changing target anchor element name');
</script>

