replace tabs by spaces

modules/viz/doc/viz.rst

@@ -7,5 +7,3 @@ viz. 3D Visualizer
 	
 	viz3d.rst
 	widget.rst
-	types.rst
-	widget_accessor.rst

modules/viz/doc/widget.rst

@@ -63,6 +63,18 @@ Casts a widget to another.
 
 .. ocv:function:: template<typename _W> _W cast()
 
+WidgetAccessor
+--------------
+.. ocv:class:: WidgetAccessor
+
+This class is for users who want to develop their own widgets using VTK library API. ::
+
+    struct CV_EXPORTS WidgetAccessor
+    {
+        static vtkSmartPointer<vtkProp> getProp(const Widget &widget);
+        static void setProp(Widget &widget, vtkSmartPointer<vtkProp> prop);
+    };
+    
 Widget3D
 --------
 .. ocv:class:: Widget3D