registry key to allow to show gutter separator in distraction free mode

platform/platform-impl/src/com/intellij/openapi/editor/impl/EditorGutterComponentImpl.java

@@ -1073,14 +1073,16 @@ class EditorGutterComponentImpl extends EditorGutterComponentEx implements Mouse
   }
 
   private void paintFoldingLines(final Graphics2D g, final Rectangle clip) {
-    if (!isFoldingOutlineShown()) return;
+    boolean shown = isFoldingOutlineShown();
 
-    if (myPaintBackground) {
+    if ((shown || (myEditor.isInDistractionFreeMode() && Registry.is("editor.distraction.gutter.separator"))) && myPaintBackground) {
       g.setColor(getOutlineColor(false));
       int x = getWhitespaceSeparatorOffset();
       UIUtil.drawLine(g, x, clip.y, x, clip.y + clip.height);
     }
 
+    if (!shown) return;
+
     final int anchorX = getFoldingAreaOffset();
     final int width = getFoldingAnchorWidth();
 

platform/util/resources/misc/registry.properties

@@ -924,6 +924,9 @@ editor.transparent.scrollbar.description=Don't paint background for editor scrol
 editor.full.width.scrollbar=false
 editor.full.width.scrollbar.description=Increase width of the vertical scrollbar to fit marks width
 
+editor.distraction.gutter.separator=false
+editor.distraction.gutter.separator.description=Show vertical line separating gutter area in distraction free mode
+
 editor.scale.gutter.icons=true
 editor.scale.gutter.icons.description=Scale gutter icons to fit line height
 editor.scale.completion.icons=false