<!DOCTYPE html>
<html>
<title>
  Resnap when the current snap position is no longer a valid snap target.
</title>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap-1/#snap-scope"/>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/css/css-scroll-snap/support/common.js"></script>
<style>
  html {
    scroll-snap-type: y mandatory;
  }
  body {
    margin:  0;
  }
  .snap {
    scroll-snap-align: center;
    height: 100vh;
    margin:  0;
  }
</style>
<body onload = "runTest()">
<div id = "card1" class="snap">ONE</div>
<div id = "card2" class="snap">TWO</div>
<div id = "card3" class="snap">THREE</div>
</body>
<script type="text/javascript">
  function runTest() {
    promise_test(async t => {
      const scroller = document.scrollingElement;
      // scroll to card THREE
      let expectedSnapPosition = card3.offsetTop;
      scroller.scrollTo(0, expectedSnapPosition);
      assert_equals(scroller.scrollTop, expectedSnapPosition,
                    'Aligned with card THREE before style change');

      // Snap to card TWO after invalidating card THREE as a snap target.
      card3.style.scrollSnapAlign = 'none center';
      await waitForNextFrame();
      expectedSnapPosition = card2.offsetTop;
      assert_equals(scroller.scrollTop, expectedSnapPosition,
                    'Aligned with card TWO after style change');
    }, 'Resnap when the current snap position is no longer a valid snap target');
  }
</script>
</html>
