perform one more check on song formats

it detects something like this: %. (where . doesn't stand for a valid tag type).

src/helpers.cpp

@@ -146,6 +146,8 @@ void ParseArgv(int argc, char **argv)
 			if (Mpd.isPlaying())
 			{
 				if (argc > ++i)
+				{
+					if (MPD::Song::isFormatOk("now-playing format", now_playing_format))
 					{
 						// apply additional pair of braces
 						now_playing_format = "{";
@@ -153,7 +155,7 @@ void ParseArgv(int argc, char **argv)
 						now_playing_format += "}";
 						Replace(now_playing_format, "\\n", "\n");
 						Replace(now_playing_format, "\\t", "\t");
-					MPD::Song::ValidateFormat("now-playing format", now_playing_format);
+					}
 				}
 				std::cout << utf_to_locale_cpy(Mpd.GetCurrentSong().toString(now_playing_format)) << "\n";
 			}

src/settings.cpp

@@ -691,9 +691,8 @@ void NcmpcppConfig::Read()
 			}
 			else if (cl.find("song_list_format") != std::string::npos)
 			{
-				if (!v.empty())
+				if (!v.empty() && MPD::Song::isFormatOk("song_list_format", v))
 				{
-					MPD::Song::ValidateFormat("song_list_format", v);
 					song_list_format = '{';
 					song_list_format += v;
 					song_list_format += '}';
@@ -706,9 +705,8 @@ void NcmpcppConfig::Read()
 			}
 			else if (cl.find("song_status_format") != std::string::npos)
 			{
-				if (!v.empty())
+				if (!v.empty() && MPD::Song::isFormatOk("song_status_format", v))
 				{
-					MPD::Song::ValidateFormat("song_status_format", v);
 					song_status_format = '{';
 					song_status_format += v;
 					song_status_format += '}';
@@ -725,9 +723,8 @@ void NcmpcppConfig::Read()
 			}
 			else if (cl.find("song_library_format") != std::string::npos)
 			{
-				if (!v.empty())
+				if (!v.empty() && MPD::Song::isFormatOk("song_library_format", v))
 				{
-					MPD::Song::ValidateFormat("song_library_format", v);
 					song_library_format = '{';
 					song_library_format += v;
 					song_library_format += '}';
@@ -735,9 +732,8 @@ void NcmpcppConfig::Read()
 			}
 			else if (cl.find("tag_editor_album_format") != std::string::npos)
 			{
-				if (!v.empty())
+				if (!v.empty() && MPD::Song::isFormatOk("tag_editor_album_format", v))
 				{
-					MPD::Song::ValidateFormat("tag_editor_album_format", v);
 					tag_editor_album_format = '{';
 					tag_editor_album_format += v;
 					tag_editor_album_format += '}';
@@ -760,9 +756,8 @@ void NcmpcppConfig::Read()
 			}
 			else if (cl.find("alternative_header_first_line_format") != std::string::npos)
 			{
-				if (!v.empty())
+				if (!v.empty() && MPD::Song::isFormatOk("alternative_header_first_line_format", v))
 				{
-					MPD::Song::ValidateFormat("alternative_header_first_line_format", v);
 					new_header_first_line = '{';
 					new_header_first_line += v;
 					new_header_first_line += '}';
@@ -770,9 +765,8 @@ void NcmpcppConfig::Read()
 			}
 			else if (cl.find("alternative_header_second_line_format") != std::string::npos)
 			{
-				if (!v.empty())
+				if (!v.empty() && MPD::Song::isFormatOk("alternative_header_second_line_format", v))
 				{
-					MPD::Song::ValidateFormat("alternative_header_second_line_format", v);
 					new_header_second_line = '{';
 					new_header_second_line += v;
 					new_header_second_line += '}';
@@ -1096,9 +1090,8 @@ void NcmpcppConfig::Read()
 			}
 			else if (cl.find("song_window_title_format") != std::string::npos)
 			{
-				if (!v.empty())
+				if (!v.empty() && MPD::Song::isFormatOk("song_window_title_format", v))
 				{
-					MPD::Song::ValidateFormat("song_window_title_format", v);
 					song_window_title_format = '{';
 					song_window_title_format += v;
 					song_window_title_format += '}';

src/song.cpp

@@ -25,6 +25,7 @@
 #include <cstdlib>
 #include <cstring>
 #include <iomanip>
+#include <iostream>
 #include <sstream>
 #include <stdexcept>
 
@@ -492,7 +493,7 @@ std::string MPD::Song::ShowTime(int length)
 	return ss.str();
 }
 
-void MPD::Song::ValidateFormat(const std::string &type, const std::string &s)
+bool MPD::Song::isFormatOk(const std::string &type, const std::string &s)
 {
 	int braces = 0;
 	for (std::string::const_iterator it = s.begin(); it != s.end(); ++it)
@@ -503,7 +504,22 @@ void MPD::Song::ValidateFormat(const std::string &type, const std::string &s)
 			--braces;
 	}
 	if (braces)
-		FatalError(type + ": number of opening and closing braces does not equal!");
+	{
+		std::cerr << type << ": number of opening and closing braces does not equal!\n";
+		return false;
+	}
+	
+	for (size_t i = s.find('%'); i != std::string::npos; i = s.find('%', i))
+	{
+		if (isdigit(s[++i]))
+			while (isdigit(s[++i])) { }
+		if (!toGetFunction(s[i]))
+		{
+			std::cerr << type << ": invalid character at position " << IntoStr(s[i]) << ": '" << s[i] << "'\n";
+			return false;
+		}
+	}
+	return true;
 }
 
 void MPD::Song::SetHashAndSlash()

src/song.h

@@ -103,7 +103,7 @@ namespace MPD
 			Song &operator=(const Song &);
 			
 			static std::string ShowTime(int);
-			static void ValidateFormat(const std::string &type, const std::string &format);
+			static bool isFormatOk(const std::string &type, const std::string &format);
 			
 		private:
 			void SetHashAndSlash();