The example below is pretty useless however it shows how contextual menus can be implemented. It displays a special popup menu when some text is selected and the normal Edit popup menu otherwise.

  <command name="contextualMenu">
    <macro>
      <choice>
        <sequence>
          <test expression="$selectedChars != ''" />
          <command name="contextualMenu1" />
        </sequence>
        
        <command name="editMenu" />
      </choice>
    </macro>
  </command>

  <command name="contextualMenu1">
    <menu>
      <item label="To Upper Case"
            icon="contextualmenus_icons/to_upper_case.gif"
            command="convertCase" parameter="upper" />
      <item label="To Lower Case"
            icon="contextualmenus_icons/to_lower_case.gif"
            command="convertCase" parameter="lower" />
      <item label="Capitalize Words" 
            command="convertCase" parameter="capital" />

      <editMenu />
    </menu>
  </command>

  <binding>
    <mousePressed button="3"/>
    <command name="contextualMenu" />
  </binding>