src/Tools/jEdit/src/jedit/Plugin.scala

 import javax.swing.JScrollPane
 
 import scala.collection.mutable
 
 import isabelle.prover.{Prover, Command}
+import isabelle.proofdocument.ProofDocument
 import isabelle.Isabelle_System
 
 import org.gjt.sp.jedit.{jEdit, EBMessage, EBPlugin, Buffer, EditPane, ServiceManager, View}
 import org.gjt.sp.jedit.buffer.JEditBuffer
 import org.gjt.sp.jedit.textarea.JEditTextArea

         Isabelle.system.platform_file("~~/lib/fonts/IsabelleMono.ttf")).
       deriveFont(Font.PLAIN, (size max 1).toFloat)
     font_changed.event(font)
   }
 
+  /* event buses */
+
+  val state_update = new EventBus[Command]
+  val command_change = new EventBus[Command]
+  val document_change = new EventBus[ProofDocument]
 
   /* selected state */
-
-  val state_update = new EventBus[Command]
 
   private var _selected_state: Command = null
   def selected_state = _selected_state
   def selected_state_=(state: Command) { _selected_state = state; state_update.event(state) }