src/Tools/jEdit/src/proofdocument/ProofDocument.scala

           last_token = last_added
       }
       else if (after_change != null)
         after_change.prev = before_change
     }
-    
+
+    System.err.println("token_changed: " + before_change + " " + after_change + " " + first_removed)
     token_changed(before_change, after_change, first_removed)
   }