<?xml version="1.0"?>
<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
  <style xmlns="http://www.w3.org/1999/xhtml">
    <![CDATA[
      menulist, menuitem, label { font: Menu }
      #measurelabel { color: transparent }
    ]]>
  </style>
  <stack>
    <vbox>
      <menulist>
        <menupopup>
          <menuitem value="1" label="long item" />
          <menuitem value="2" label="short" />
        </menupopup>
      </menulist>
    </vbox>
    <hbox>
      <label id="measurelabel" value="long item" />
      <!-- cover up the right edge of the above -->
      <box flex="1" style="background: white" />
    </hbox>
  </stack>
</window>
