palemoon-dev/platform/layout/reftests/xul/text-crop.xul

<?xml version="1.0"?>
<window class="reftest-wait"
        align="left"
        xmlns:html="http://www.w3.org/1999/xhtml"
        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
  <html:style type="text/css">
    @font-face {
      font-family: firasans;
      src: url(../fonts/fira/FiraSans-Regular.otf);
    }
    vbox {
      font-family: firasans;
      font-size: 40px;
    }
  </html:style>
<vbox width="230">
  <label id="start" value="" crop="start" />
  <label id="end" value="" crop="end" />
  <label id="center" value="" crop="center" />
</vbox>
<script>
<![CDATA[
function text(n) {
  return "\u{1F310}".repeat(n);
}
document.getElementById("start").value = text(10);
document.getElementById("end").value = text(10);
document.getElementById("center").value = text(10);
document.documentElement.className = "";
]]>
</script>
</window>