Enforce stricter world names using a blacklist

Blacklisted characters are: / \

src/guiMainMenu.cpp

@@ -39,6 +39,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "tile.h" // getTexturePath
 #include "filesys.h"
 #include "util/string.h"
+#include "subgame.h"
 
 struct CreateWorldDestMainMenu : public CreateWorldDest
 {
@@ -47,7 +48,10 @@ struct CreateWorldDestMainMenu : public CreateWorldDest
 	{}
 	void accepted(std::wstring name, std::string gameid)
 	{
-		m_menu->createNewWorld(name, gameid);
+		if(!string_allowed_blacklist(wide_to_narrow(name), WORLDNAME_BLACKLISTED_CHARS))
+			m_menu->displayMessageMenu(wgettext("Cannot create world: Name contains invalid characters"));
+		else
+			m_menu->createNewWorld(name, gameid);
 	}
 	GUIMainMenu *m_menu;
 };
@@ -929,3 +933,7 @@ int GUIMainMenu::getTab()
 	return TAB_SINGLEPLAYER; // Default
 }
 
+void GUIMainMenu::displayMessageMenu(std::wstring msg)
+{
+	(new GUIMessageMenu(env, parent, -1, menumgr, msg))->drop();
+}

src/guiMainMenu.h

@@ -92,6 +92,7 @@ public:
 	void createNewWorld(std::wstring name, std::string gameid);
 	void deleteWorld(const std::vector<std::string> &paths);
 	int getTab();
+	void displayMessageMenu(std::wstring msg);
 	
 private:
 	MainMenuData *m_data;

src/subgame.h

@@ -24,6 +24,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include <set>
 #include <vector>
 
+#define WORLDNAME_BLACKLISTED_CHARS "/\\"
+
 struct SubgameSpec
 {
 	std::string id; // "" = game does not exist

src/util/string.h

@@ -242,6 +242,29 @@ inline bool string_allowed(const std::string &s, const std::string &allowed_char
 	return true;
 }
 
+/*
+	Checks if a string contains no blacklisted characters (opposite
+	function of string_allowed())
+*/
+inline bool string_allowed_blacklist(const std::string & s, const std::string & blacklisted_chars)
+{
+	for(unsigned int i = 0; i < s.length(); i++)
+	{
+		bool invalid = false;
+		for(unsigned int j = 0; j < blacklisted_chars.length(); j++)
+		{
+			if(s[i] == blacklisted_chars[j])
+			{
+				invalid = true;
+				break;
+			}
+		}
+		if(invalid)
+			return false;
+	}
+	return true;
+}
+
 /*
 	Forcefully wraps string into rows using \n
 	(no word wrap, used for showing paths in gui)