chdir to data directory on mac

May change this later if I decide to go back to using objective-c (or swift?) later to reimplement the rest of the mac features

src/PowderToySDL.cpp

@@ -28,6 +28,10 @@
 #ifndef WIN
 #include <unistd.h>
 #endif
+#ifdef MACOSX
+#include <CoreServices/CoreServices.h>
+#include <sys/stat.h>
+#endif
 
 #include "Format.h"
 
@@ -546,6 +550,23 @@ void SigHandler(int signal)
 	}
 }
 
+void ChdirToDataDirectory()
+{
+#ifdef MACOSX
+    FSRef ref;
+    OSType folderType = kApplicationSupportFolderType;
+    char path[PATH_MAX];
+
+    FSFindFolder( kUserDomain, folderType, kCreateFolder, &ref );
+
+    FSRefMakePath( &ref, (UInt8*)&path, PATH_MAX );
+
+    const char *tptPath = (std::string(path) + "/The Powder Toy").c_str();
+    mkdir(tptPath, 0755);
+    chdir(tptPath);
+#endif
+}
+
 int main(int argc, char * argv[])
 {
 #if defined(_DEBUG) && defined(_MSC_VER)
@@ -563,6 +584,8 @@ int main(int argc, char * argv[])
 #else
 		chdir(arguments["ddir"].c_str());
 #endif
+    else
+        ChdirToDataDirectory();
 
 	scale = Client::Ref().GetPrefInteger("Scale", 1);
 	resizable = Client::Ref().GetPrefBool("Resizable", false);