yakindu/de.itemis.xtext.utils/plugins/de.itemis.xtext.utils.jface/plugin.xml

<?xml version="1.0" encoding="UTF-8"?>
<?eclipse version="3.4"?>
<plugin>
   <extension
         point="org.eclipse.ui.handlers">
      <handler
            class="de.itemis.xtext.utils.jface.internal.handlers.ContentAssistHandler"
            commandId="org.eclipse.ui.edit.text.contentAssist.proposals">
         <activeWhen>
            <with
                  variable="activeFocusControlId">
               <equals
                     value="org.eclipse.swt.custom.StyledText">
               </equals>
            </with>
         </activeWhen>
      </handler>
   </extension>

</plugin>