<!doctype html> <meta charset="utf-8"> <title>Tests that after making a scrolling box a containing block, dynamically-inserted abspos boxes still get positioned correctly</title> <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1735533"> <link rel="help" href="https://drafts.csswg.org/css-position/#abspos-insets"> <link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez"> <link rel="author" href="https://mozilla.org" title="Mozilla"> <link rel="match" href="containing-block-change-scrollframe-ref.html"> <style> #container { width: 400px; height: 400px; margin: 100px; background-color: purple; overflow: hidden; } #spacer { height: 700px; } #bottom { height: 100px; background-color: green; } #abspos { position: absolute; width: 100px; height: 100px; background-color: green; top: 400px; left: 0; } </style> <div id="container"> <div id="spacer"></div> <div id="bottom"></div> </div> <script> let container = document.getElementById("container"); container.scrollTop = 400; container.getBoundingClientRect(); container.style.position = "relative"; container.getBoundingClientRect(); let abspos = document.createElement("div"); abspos.id = "abspos"; container.appendChild(abspos); </script>