css/css-grid/masonry/tentative/item-placement/masonry-rows-with-grid-width-changed.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<link rel="author" title="Sammy Gill" href="mailto:sammy.gill@apple.com">
<link rel="help" href="https://drafts.csswg.org/css-grid-3">
<link rel="match" href="masonry-rows-with-grid-width-changed-ref.html">
<meta name="assert" content="When the width of the masonry grid changes, items are repositioned with correct offsets and are not overlapping">
<link rel="stylesheet" type="text/css" href="/fonts/ahem.css">
<style>
  grid {
    display: grid;
    grid-template-rows: masonry;
    grid-template-columns: auto;
    grid-gap: 10px;
    font-family: Ahem;
    font-size: 40px;
  }
  item {
    background-color: grey;
  }
</style>
</head>
<body>
  <grid>
    <item>Hello, world!</item>
    <item>2</item>
  </grid>
</body>
<script>
  // Make sure layout occurs and then mutate the style to retrigger it
  document.body.offsetHeight;
  document.querySelector("grid").style["width"] = "1%";
</script>
</html>