css/cssom-view/scrollIntoView-root-overflow-clip.html

<!DOCTYPE html>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1">
<title>scrollIntoView still scrolls the viewport programmatically when overflow-x or overflow-y: clip is applied to the viewport.</title>
<link rel="help" href="https://drafts.csswg.org/css-overflow-3/#overflow-propagation">
<link rel="help" href="https://drafts.csswg.org/cssom-view/#dom-element-scrollintoview">
<meta name="assert" content="When overflow-x or overflow-y: clip is applied to the viewport, it is interpreted as hidden, so scrollIntoView can still scroll the viewport programmatically in that axis.">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
#log { position: fixed; }
html, body { margin: 0; }
body {
  position: relative;
  width: 10000px;
  height: 10000px;
}
.target {
  position: absolute;
  width: 100px;
  height: 100px;
}
#target-x {
  left: 5000px;
  top: 0;
}
#target-y {
  left: 0;
  top: 5000px;
}
</style>

<div id="log"></div>
<div id="target-x" class="target"></div>
<div id="target-y" class="target"></div>

<script>
const targetX = document.getElementById("target-x");
const targetY = document.getElementById("target-y");

function reset() {
  document.documentElement.style.overflowX = "visible";
  document.documentElement.style.overflowY = "visible";
  document.scrollingElement.scrollLeft = 0;
  document.scrollingElement.scrollTop = 0;
  assert_equals(window.scrollX, 0, "Precondition: window.scrollX");
  assert_equals(window.scrollY, 0, "Precondition: window.scrollY");
}

test(() => {
  reset();
  // Use clip + visible so this specifically exercises the viewport rule,
  // not the general overflow-x/overflow-y compute-to-hidden rule.
  document.documentElement.style.overflowX = "clip";
  document.documentElement.style.overflowY = "visible";

  targetX.scrollIntoView({block: "nearest", inline: "start", behavior: 'instant'});

  assert_greater_than(window.scrollX, 0, "scrollIntoView should scroll the viewport horizontally");
  assert_equals(window.scrollY, 0, "scrollIntoView should not scroll the viewport vertically");
}, "scrollIntoView scrolls the viewport when overflow-x: clip is applied to the root element");

test(() => {
  reset();
  // Use visible + clip so this specifically exercises the viewport rule,
  // not the general overflow-x/overflow-y compute-to-hidden rule.
  document.documentElement.style.overflowX = "visible";
  document.documentElement.style.overflowY = "clip";

  targetY.scrollIntoView({block: "start", inline: "nearest", behavior: 'instant'});

  assert_equals(window.scrollX, 0, "scrollIntoView should not scroll the viewport horizontally");
  assert_greater_than(window.scrollY, 0, "scrollIntoView should scroll the viewport vertically");
}, "scrollIntoView scrolls the viewport when overflow-y: clip is applied to the root element");
</script>