add a method to show caret for the uneditable textbox

When an uneditable textbox has a caret, user can select the text and copy
it.

include/nana/gui/widgets/skeletons/text_editor.hpp

@@ -118,7 +118,13 @@ namespace nana{	namespace widgets
 
 			const attributes & attr() const;
 			bool multi_lines(bool);
-			void editable(bool);
+
+			/// Enables/disables the editability of text_editor
+			/**
+			 * @param enable Indicates whether to enable or disable the editability
+			 * @param enable_cart Indicates whether to show or hide the caret when the text_editor is not editable. It is ignored if enable is false.
+			 */
+			void editable(bool enable, bool enable_caret);
 			void enable_background(bool);
 			void enable_background_counterpart(bool);
 
@@ -255,6 +261,7 @@ namespace nana{	namespace widgets
 				bool line_wrapped{false};
 				bool multi_lines{true};
 				bool editable{true};
+				bool enable_caret{ true }; ///< Indicates whether to show or hide caret when text_editor is not editable
 				bool enable_background{true};
 			}attributes_;
 

include/nana/gui/widgets/textbox.hpp

@@ -184,6 +184,9 @@ namespace nana
 		bool editable() const;
 		textbox& editable(bool);
 
+		/// Enables the caret if the textbox current is not editable
+		textbox& enable_caret();
+
 		void set_accept(std::function<bool(wchar_t)>);
 
 		textbox& tip_string(::std::string);