scrollIntoView-align-scrollport-covering-child.html

<!doctype html>
<title>CSSOM View - scrollIntoView aligns scrollport-covering child in both inline and block directions.</title>
<meta charset="utf-8">
<link rel="help" href="https://drafts.csswg.org/cssom-view/#dom-element-scrollintoview">
<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1497677">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  #scroller {
    width: 200px;
    height: 200px;
    background-color: purple;
    overflow: hidden;
    position: relative;
  }
  #child {
    width: 400px;
    height: 400px;
    background-color: green;
    position: absolute;
    left: 0px;
    top: 0px;
  }
</style>
<div id="scroller">
  <div id="space" style="height:400%; width: 400%"></div>
  <div id="child"></div>
</div>
<script>
  const scroller = document.getElementById("scroller");
  const child = document.getElementById("child");

  function test_alignment(alignment, start_offset, expected_offset) {
    scroller.scrollTop = start_offset.top;
    scroller.scrollLeft = start_offset.left;

    child.scrollIntoView({block: alignment, inline: alignment});

    assert_equals(scroller.scrollTop, expected_offset.top,
        `${alignment} sets top`);
    assert_equals(scroller.scrollLeft, expected_offset.left,
        `${alignment} sets left`);
  }

  test(function() {
    // child, being positioned at (0, 0) and having size 400 x 400 covers the
    // scrollport at scroll offsets (0,0) and (100, 100).
    test_alignment("start", {top: 100, left: 100}, {top: 0, left: 0});
    test_alignment("center", {top: 0, left: 0}, {top: 100, left: 100});
    test_alignment("end", {top: 100, left: 100}, {top: 200, left: 200});
  }, "scrollIntoView scrolls scrollport-covering child in both axes");
</script>