src/Tools/jEdit/src/jedit_editor.scala

   /* hyperlinks */
 
   def hyperlink_url(name: String): Hyperlink =
     new Hyperlink {
       val external = true
-      def follow(view: View) =
-        default_thread_pool.submit(() =>
+      def follow(view: View): Unit =
+        Future.fork {
           try { Isabelle_System.open(name) }
           catch {
             case exn: Throwable =>
               GUI.error_dialog(view, "System error", GUI.scrollable_text(Exn.message(exn)))
-          })
+          }
+        }
       override def toString: String = "URL " + quote(name)
     }
 
   def hyperlink_file(name: String, line: Int = 0, column: Int = 0): Hyperlink =
     new Hyperlink {
       val external = false
-      def follow(view: View) = goto_file(view, name, line, column)
+      def follow(view: View): Unit = goto_file(view, name, line, column)
       override def toString: String = "file " + quote(name)
     }
 
   def hyperlink_source_file(source_name: String, line: Int, offset: Symbol.Offset)
     : Option[Hyperlink] =