<!DOCTYPE html>
<!--
 | The user agent should use the font face within a given font family
 | that most closely matches the specified weight and style.
 |   https://www.w3.org/TR/css3-ui/#propdef-text-overflow
 | One should be able to specify transform functions via rotate functions.
 | When the "text-overflow" property is set to "ellipsis" an ellipsis
 | character is rendered to represent clipped inline content.
 | "Ellipsing occurs after relative positioning and other graphical
 | transformations."
 |   https://www.w3.org/TR/css3-ui/#propdef-text-overflow
 -->
<html>
<head>
  <style>
    body {
      margin: 0px;
      font-family: Roboto;
      font-size: 16px;
    }
    .transformed {
      transform: rotate(45deg);

      width: 100px;
      height: 50px;
      background-color: rgb(255, 100, 100);
    }
    .orientation-marker {
      position: absolute;
      right: 0;
      width: 25px;
      height: 100%;
      background-color: rgb(100, 100, 255);
      overflow: hidden;
      text-overflow: ellipsis;
    }
  </style>
</head>

<body>
  <div class="transformed">
    <div dir="ltr" class="orientation-marker">testing</div>
  </div>
  <div class="transformed">
    <div dir="rtl" class="orientation-marker">testing</div>
  </div>
</body>

</html>