position-sticky-in-fixed-container.html

<!DOCTYPE html>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<meta name="fuzzy" content="1;0-50">
<link rel="match" href="position-sticky-in-fixed-container-ref.html">
<link rel="help" href="https://drafts.csswg.org/css-position-3/#sticky-pos">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1854010">
<style>
  .modal {
    bottom: 0;
    left: 0;
    right: 0;
    position: fixed;
  }

  .modal-dialog {
    position: relative;
    overflow: auto;
    max-height: 400px;
    transform: translateY(0);
  }

  .modal-content {
    background-color: purple;
    height: 400px;
  }

  .modal-footer {
    height: 100px;
    background-color: blue;

    position:sticky;
    bottom: 0;
  }
</style>
<div class="modal">
  <div class="modal-dialog">
    <div class="modal-content"></div>
    <div class="modal-footer"></div>
  </div>
</div>

chromium/third_party/blink/web_tests/external/wpt/css/css-position/sticky/position-sticky-in-fixed-container.html