diff --git a/src/Tools/jEdit/src/info_dockable.scala b/src/Tools/jEdit/src/info_dockable.scala
--- a/src/Tools/jEdit/src/info_dockable.scala
+++ b/src/Tools/jEdit/src/info_dockable.scala
@@ -1,115 +1,115 @@
 /*  Title:      Tools/jEdit/src/info_dockable.scala
     Author:     Makarius
 
 Dockable window with info text.
 */
 
 package isabelle.jedit
 
 
 import isabelle._
 
 import java.awt.BorderLayout
 import java.awt.event.{ComponentEvent, ComponentAdapter, WindowFocusListener, WindowEvent}
 
 import org.gjt.sp.jedit.View
 
 
 object Info_Dockable {
   /* implicit arguments -- owned by GUI thread */
 
   private var implicit_snapshot = Document.Snapshot.init
   private var implicit_results = Command.Results.empty
   private var implicit_info: XML.Body = Nil
 
   private def set_implicit(
     snapshot: Document.Snapshot,
     results: Command.Results,
     info: XML.Body
   ): Unit = {
     GUI_Thread.require {}
 
     implicit_snapshot = snapshot
     implicit_results = results
     implicit_info = info
   }
 
   private def reset_implicit(): Unit =
     set_implicit(Document.Snapshot.init, Command.Results.empty, Nil)
 
   def apply(
     view: View,
     snapshot: Document.Snapshot,
     results: Command.Results,
     info: XML.Body
   ): Unit = {
     set_implicit(snapshot, results, info)
     view.getDockableWindowManager.floatDockableWindow("isabelle-info")
   }
 }
 
 
 class Info_Dockable(view: View, position: String) extends Dockable(view, position) {
   /* component state -- owned by GUI thread */
 
   private val snapshot = Info_Dockable.implicit_snapshot
   private val results = Info_Dockable.implicit_results
   private val info = Info_Dockable.implicit_info
 
   private val window_focus_listener =
     new WindowFocusListener {
       def windowGainedFocus(e: WindowEvent): Unit =
         Info_Dockable.set_implicit(snapshot, results, info)
       def windowLostFocus(e: WindowEvent): Unit =
         Info_Dockable.reset_implicit()
     }
 
 
   /* pretty text area */
 
   private val pretty_text_area = new Pretty_Text_Area(view)
   set_content(pretty_text_area)
 
   pretty_text_area.update(snapshot, results, info)
 
   private val zoom = new Font_Info.Zoom_Box { def changed(): Unit = handle_resize() }
 
   private def handle_resize(): Unit =
     GUI_Thread.require { pretty_text_area.zoom(zoom.factor) }
 
 
   /* resize */
 
   private val delay_resize =
     Delay.first(PIDE.options.seconds("editor_update_delay"), gui = true) { handle_resize() }
 
   addComponentListener(new ComponentAdapter {
     override def componentResized(e: ComponentEvent): Unit = delay_resize.invoke()
     override def componentShown(e: ComponentEvent): Unit = delay_resize.invoke()
   })
 
   private val controls =
     Wrap_Panel(List(pretty_text_area.search_label, pretty_text_area.search_field, zoom))
 
   add(controls.peer, BorderLayout.NORTH)
 
 
   /* main */
 
   private val main =
     Session.Consumer[Session.Global_Options](getClass.getName) {
       case _: Session.Global_Options => GUI_Thread.later { handle_resize() }
     }
 
   override def init(): Unit = {
-    GUI.parent_window(this).map(_.addWindowFocusListener(window_focus_listener))
+    GUI.parent_window(this).foreach(_.addWindowFocusListener(window_focus_listener))
     PIDE.session.global_options += main
     handle_resize()
   }
 
   override def exit(): Unit = {
-    GUI.parent_window(this).map(_.removeWindowFocusListener(window_focus_listener))
+    GUI.parent_window(this).foreach(_.removeWindowFocusListener(window_focus_listener))
     PIDE.session.global_options -= main
     delay_resize.revoke()
   }
 }