<svg xmlns="http://www.w3.org/2000/svg"
     xmlns:h="http://www.w3.org/1999/xhtml"
     xmlns:xlink="http://www.w3.org/1999/xlink"
     width="300" height="200" viewBox="0 0 300 200"
     font-family="sans-serif" font-size="28">
  <metadata>
    <h:link rel="help" href="https://svgwg.org/svg2-draft/paths.html#PathLengthAttribute"/>
    <h:link rel="match" href="pathLength-positive-ref.svg"/>
    <h:meta name="assert" content="pathLength scales distance along the path"/>
  </metadata>

  <defs>
    <path id="track" stroke="lightblue" fill="none" d="M 50 50 h 200" pathLength="2"/>
  </defs>

  <g>
    <use xlink:href="#track"/>
    <text>
      <textPath xlink:href="#track" startOffset="0%">The quick brown fox</textPath>
    </text>
  </g>

  <g transform="translate(0,50)">
    <use xlink:href="#track"/>
    <text>
      <textPath xlink:href="#track" startOffset="50%">The quick brown fox</textPath>
    </text>
  </g>

  <g transform="translate(0,100)">
    <use xlink:href="#track"/>
    <text>
      <textPath xlink:href="#track" startOffset="-50%">The quick brown fox</textPath>
    </text>
  </g>
</svg>