src/Tools/jEdit/src/jedit/isabelle_markup.scala

   val message: Markup_Tree.Select[Color] =
   {
     case Text.Info(_, XML.Elem(Markup(Markup.WRITELN, _), _)) => regular_color
     case Text.Info(_, XML.Elem(Markup(Markup.WARNING, _), _)) => warning_color
     case Text.Info(_, XML.Elem(Markup(Markup.ERROR, _), _)) => error_color
+  }
+
+  val popup: Markup_Tree.Select[XML.Tree] =
+  {
+    case Text.Info(_, msg @ XML.Elem(Markup(markup, _), _))
+    if markup == Markup.WRITELN || markup == Markup.WARNING || markup == Markup.ERROR => msg
   }
 
   val gutter_message: Markup_Tree.Select[Icon] =
   {
     case Text.Info(_, XML.Elem(Markup(Markup.WARNING, _), _)) => warning_icon