<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

 <head>

  <title>CSS Reftest Reference</title>

  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/" />

  <meta name="DC.date.created" content="2016-10-04T09:54:03+11:00" scheme="W3CDTF" />
  <meta name="DC.date.modified" content="2017-01-08T09:54:03+11:00" scheme="W3CDTF" />

  <meta content="" name="flags" />

  <style type="text/css"><![CDATA[
  html
    {
      padding: 100px 0px;
      writing-mode: vertical-lr;
    }

  body
    {
      font-size: 16px;
      line-height: 1.25; /* therefore, each line box is 20px tall */
    }

  p
    {
      left: 8px;
      position: absolute;
      writing-mode: horizontal-tb;
    }

  p#sentence-before
    {
      margin-top: 0px;
      top: 100px;
    }

  div
    {
      border: blue solid 3px;
      height: auto;
      left: 8px;
      position: absolute;
      top: 136px;
    }

  p#sentence-after
    {
      padding-bottom: calc(600px - 100px + 16px - 52px - 3px - 15ch - 3px - 52px + 16px);
      /*
      600px
   -
      100px
   +
       16px : margin collapsing of p#sentence-before's margin-top with body's margin-top
   -
       52px
   -
        3px
   -
       15ch
   -
        3px
   -
       52px
   +
       16px : margin collapsing of p#sentence-after's margin-bottom with body's margin-bottom
  ============
   approx. 270px
      */

      top: calc(136px + 3px + 15ch + 3px);
      /*
      15ch means 15 ch unit where each ch is equal to
      the used advance measure of the "0" (ZERO, U+0030) glyph found
      in the font used to render it.
      5.1.1. Font-relative lengths: the em, ex, ch, rem units
      https://www.w3.org/TR/css3-values/#ch
      */
    }
  ]]></style>
 </head>

 <body>

  <p id="sentence-before">Sentence before.</p>

  <div>123456789012345</div>

  <p id="sentence-after">Sentence after.</p>

 </body>
</html>