added option jedit_text_overview for visual appearance (not performance, see also 72216713733a);

--- a/NEWS	Thu Jan 31 16:56:31 2019 +0100
+++ b/NEWS	Thu Jan 31 17:18:15 2019 +0100
@@ -53,6 +53,9 @@
 entries are structured according to chapter / session names, the open
 operation is redirected to the session ROOT file.
 
+* System option "jedit_text_overview" allows to disable the text
+overview column.
+
 * Fonts for the text area, gutter, GUI elements etc. use the "Isabelle
 DejaVu" collection by default, which provides uniform rendering quality
 with the usual Isabelle symbols. Line spacing no longer needs to be

--- a/src/Tools/jEdit/etc/options	Thu Jan 31 16:56:31 2019 +0100
+++ b/src/Tools/jEdit/etc/options	Thu Jan 31 17:18:15 2019 +0100
@@ -36,6 +36,9 @@
 public option jedit_timing_threshold : real = 0.1
   -- "default threshold for timing display (seconds)"
 
+public option jedit_text_overview : bool = true
+  -- "paint text overview column"
+
 
 section "Indentation"
 

--- a/src/Tools/jEdit/src/document_view.scala	Thu Jan 31 16:56:31 2019 +0100
+++ b/src/Tools/jEdit/src/document_view.scala	Thu Jan 31 17:18:15 2019 +0100
@@ -196,7 +196,8 @@
 
   /* text status overview left of scrollbar */
 
-  private val text_overview = new Text_Overview(this)
+  private val text_overview: Option[Text_Overview] =
+    if (PIDE.options.bool("jedit_text_overview")) Some(new Text_Overview(this)) else None
 
 
   /* main */
@@ -204,7 +205,7 @@
   private val main =
     Session.Consumer[Any](getClass.getName) {
       case _: Session.Raw_Edits =>
-        text_overview.invoke()
+        text_overview.foreach(_.invoke())
 
       case changed: Session.Commands_Changed =>
         val buffer = model.buffer
@@ -216,7 +217,7 @@
               if (changed.assignment ||
                   (changed.nodes.contains(model.node_name) &&
                    changed.commands.exists(snapshot.node.commands.contains)))
-                text_overview.invoke()
+                text_overview.foreach(_.invoke())
 
               JEdit_Lib.invalidate(text_area)
             }
@@ -236,7 +237,9 @@
     text_area.getGutter.addExtension(gutter_painter)
     text_area.addKeyListener(key_listener)
     text_area.addCaretListener(caret_listener)
-    text_area.addLeftOfScrollBar(text_overview); text_area.revalidate(); text_area.repaint()
+    text_overview.foreach(text_area.addLeftOfScrollBar(_))
+    text_area.revalidate()
+    text_area.repaint()
     Isabelle.structure_matchers(JEdit_Lib.buffer_mode(text_area.getBuffer)).
       foreach(text_area.addStructureMatcher(_))
     session.raw_edits += main
@@ -251,8 +254,10 @@
     session.commands_changed -= main
     Isabelle.structure_matchers(JEdit_Lib.buffer_mode(text_area.getBuffer)).
       foreach(text_area.removeStructureMatcher(_))
-    text_overview.revoke(); text_area.removeLeftOfScrollBar(text_overview)
-    text_area.removeCaretListener(caret_listener); delay_caret_update.revoke()
+    text_overview.foreach(_.revoke())
+    text_overview.foreach(text_area.removeLeftOfScrollBar(_))
+    text_area.removeCaretListener(caret_listener)
+    delay_caret_update.revoke()
     text_area.removeKeyListener(key_listener)
     text_area.getGutter.removeExtension(gutter_painter)
     rich_text_area.deactivate()