#include <fontconfig/fontconfig.h> FcStrSet * FcGetDefaultLangs (voidls);
Returns a string set of the default languages according to the environment variables on the system. This function looks for them in order of FC_LANG, LC_ALL, LC_CTYPE and LANG then. If there are no valid values in those environment variables, "en" will be set as fallback.
Fontconfig version 2.11.0