subtree-exclusion.html

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This WPT test may be referenced by the following Test IDs:
- /css/css-scroll-anchoring/subtree-exclusion.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<style>

body { height: 4000px }

#A, #B { width: 100px; background-color: #afa; }

#B { height: 100px; }

#inner { width: 100px; height: 100px; background-color: pink; }

#A { overflow-anchor: none; }

</style>

<div id="changer1"></div>

<div id="A">

  <div id="inner"></div>

  <div id="changer2"></div>

</div>

<div id="B"></div>

<script>

// Tests that an element with overflow-anchor: none is excluded, along with its

// DOM descendants, from the anchor selection algorithm.

test(() => {

  var changer1 = document.querySelector("#changer1");

  var changer2 = document.querySelector("#changer2");

  document.scrollingElement.scrollTop = 50;

  changer1.style.height = "100px";

  changer2.style.height = "50px";

  // We should anchor to #B, not #A or #inner, despite them being visible.

  assert_equals(document.scrollingElement.scrollTop, 200);

  document.querySelector("#A").style.overflowAnchor = "auto";

  document.scrollingElement.scrollTop = 150;

  changer1.style.height = "200px";

  changer2.style.height = "100px";

  // We should now anchor to #inner, which is moved only by #changer1.

  assert_equals(document.scrollingElement.scrollTop, 250);

}, "Subtree exclusion with overflow-anchor.");

</script>