add various overlodings for widget::caption()

include/nana/gui/widgets/listbox.hpp

@@ -573,7 +573,8 @@ By \a clicking on one header the list get \a reordered, first up, and then down
 
 		cat_proxy append(nana::string);          ///< Appends a new category at the end
 		void append(std::initializer_list<nana::string>); ///< Appends categories at the end
-		cat_proxy insert(cat_proxy, nana::string);
+
+		cat_proxy insert(cat_proxy, ::std::wstring);
 		cat_proxy at(size_type pos) const;
 
         /// add categories in order when use a key?
@@ -606,7 +607,8 @@ By \a clicking on one header the list get \a reordered, first up, and then down
 
 		item_proxy at(const index_pair &abs_pos) const;
 
-		void insert(const index_pair&, nana::string);         ///<Insert a new item with a text in the first column.
+		void insert(const index_pair&, ::std::string);		///<Insert a new item with a text in the first column.
+		void insert(const index_pair&, ::std::wstring);		///<Insert a new item with a text in the first column.
 
 		void checkable(bool);
 		selection checked() const;                         ///<Returns the items which are checked.                       

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

@@ -42,7 +42,7 @@ namespace nana{ namespace widgets{	namespace skeletons
 	class tokenizer
 	{
 	public:
-		tokenizer(const nana::string& s, bool format_enabled)
+		tokenizer(const std::wstring& s, bool format_enabled)
 			:	iptr_(s.data()),
 				endptr_(s.data() + s.size()),
 				format_enabled_(format_enabled)
@@ -74,7 +74,7 @@ namespace nana{ namespace widgets{	namespace skeletons
 			return _m_token();
 		}
 
-		const nana::string& idstr() const
+		const ::std::wstring& idstr() const
 		{
 			return idstr_;
 		}
@@ -434,7 +434,7 @@ namespace nana{ namespace widgets{	namespace skeletons
 			};
 		};
 
-		::nana::string	font;
+		::std::wstring	font;
 		std::size_t		font_size;
 		bool	bold;
 		bool	bold_empty;	//bold should be ignored if bold_empty is true
@@ -442,8 +442,8 @@ namespace nana{ namespace widgets{	namespace skeletons
 		::nana::color	bgcolor;	//If the color is not specified, it will be ignored, and the system will search for its parent.
 		::nana::color	fgcolor;	//ditto
 
-		::nana::string	target;
-		::nana::string	url;
+		::std::wstring	target;
+		::std::wstring	url;
 
 		fblock * parent;
 	};

include/nana/gui/widgets/widget.hpp

@@ -34,6 +34,11 @@ namespace nana
 		class inner_widget_notifier;
 		typedef void(*dummy_bool_type)(widget* (*)(const widget&));
 	public:
+#if defined(NANA_WINDOWS)
+		using native_string_type = std::wstring;
+#else	//POSIX
+		using native_string_type = std::string;
+#endif
 		virtual ~widget() = default;
 		virtual window handle() const = 0;			///< Returns the handle of window, returns 0 if window is not created.
 		bool empty() const;							///< Determines whether the manipulator is handling a window.
@@ -42,7 +47,11 @@ namespace nana
 		window parent() const;
 
 		::std::string caption() const throw();
-		void caption(std::string utf8);
+		::std::wstring caption_wstring() const throw();
+		native_string_type caption_native() const throw();
+
+		widget& caption(std::string utf8);
+		widget& caption(std::wstring);
 
 		template<typename ...Args>
 		void i18n(std::string msgid, Args&&... args)

source/gui/widgets/label.cpp

@@ -52,8 +52,8 @@ namespace nana
 				struct traceable
 				{
 					nana::rectangle r;
-					nana::string target;
-					nana::string url;
+					std::wstring target;
+					std::wstring url;
 				};
 
 			public:
@@ -148,7 +148,7 @@ namespace nana
 					graph.typeface(ft);
 				}
 
-				bool find(int x, int y, nana::string& target, nana::string& url) const
+				bool find(int x, int y, std::wstring& target, std::wstring& url) const
 				{
 					for (auto & t : traceable_)
 					{

source/gui/widgets/listbox.cpp

@@ -4324,7 +4324,7 @@ namespace nana
 			ess.update();
 		}
 
-		auto listbox::insert(cat_proxy cat, nana::string str) -> cat_proxy
+		auto listbox::insert(cat_proxy cat, std::wstring str) -> cat_proxy
 		{
 			internal_scope_guard lock;
 			auto & ess = _m_ess();
@@ -4358,7 +4358,12 @@ namespace nana
 			return at(pos_abs.cat).at(pos_abs.item);
 		}
 
-		void listbox::insert(const index_pair& pos, nana::string text)
+		void listbox::insert(const index_pair& pos, std::string text)
+		{
+			insert(pos, utf8_cast(text));
+		}
+
+		void listbox::insert(const index_pair& pos, std::wstring text)
 		{
 			internal_scope_guard lock;
 			auto & ess = _m_ess();

source/gui/widgets/widget.cpp

@@ -59,10 +59,31 @@ namespace nana
 			return this->_m_caption();
 		}
 
-		void widget::caption(std::string utf8)
+		std::wstring widget::caption_wstring() const throw()
+		{
+			return utf8_cast(_m_caption());
+		}
+
+		auto widget::caption_native() const throw() -> native_string_type
+		{
+#if defined(NANA_WINDOWS)
+			return caption_wstring();
+#else
+			return caption();
+#endif
+		}
+
+		widget& widget::caption(std::string utf8)
 		{
 			::nana::throw_not_utf8(utf8);
 			_m_caption(std::move(utf8));
+			return *this;
+		}
+
+		widget& widget::caption(std::wstring text)
+		{
+			_m_caption(utf8_cast(text));
+			return *this;
 		}
 
 		void widget::i18n(i18n_eval eval)