css/css-flexbox/dynamic-isize-change-004.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Flexbox Test: Dynamic change to the inline-size of a row flex container</title>
<link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
<link rel="author" title="Mozilla" href="https://www.mozilla.org/">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1700580">
<link rel="stylesheet" href="/fonts/ahem.css">
<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
<meta name="assert" content="This test verifies that the dynamic change to the flex container's inline-size triggers the reflow for flex items with percentage padding.">

<style>
#flexbox {
  display: flex;
  inline-size: 100px;
  block-size: 100px;
  font: 50px/1 Ahem;
  color: green;
  word-break: break-all;
}

#flexbox > div {
  /* The following flex-basis and padding will give our flex item a border-box
     inline-size of 100px, both before and after this test's dynamic
     modification. */
  flex-basis: 50%;
  padding-right: calc(100px - 50%);
  background: red;
}
</style>

<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<div id="flexbox">
  <div>XXXX</div>
</div>

<script>
/* Make sure the layout is up-to-date, which is essential to trigger the bug. */
document.documentElement.offsetHeight;

/* Change the flexbox's inline-size to trigger incremental reflow. */
document.getElementById("flexbox").style.inlineSize = "200px";
</script>