improve filebox appearance on Linux

source/detail/posix/theme.hpp

@@ -0,0 +1,31 @@
+#ifndef NANA_DETAIL_THEME_INCLUDED
+#define NANA_DETAIL_THEME_INCLUDED
+
+#include <string>
+#include <map>
+#include <vector>
+#include <fstream>
+
+namespace nana
+{
+	namespace detail
+	{
+		class theme
+		{
+		public:
+			theme();
+
+			std::string cursor(const std::string& name) const;
+			std::string icon(const std::string& name, std::size_t size_wanted) const;
+		private:
+			std::string path_;
+			mutable std::ifstream ifs_;
+
+			mutable std::map<std::string, std::vector<std::pair<std::size_t, std::string>>> iconcache_;
+		};
+
+	}//end namespace detail
+
+}//end namespace nana
+
+#endif