utf8Casefold
Converts a string into a form that is independent of case. The result will not correspond to any particular case, but can be compared for equality or ordered with the results of calling g_utf8_casefold() on other strings.
Note that calling g_utf8_casefold() followed by g_utf8_collate() is only an approximation to the correct linguistic case insensitive ordering, though it is a fairly good one. Getting this exactly right would require a more sophisticated collation function that takes case sensitivity into account. GLib does not currently provide such a function.
Return
a newly allocated string, that is a case independent form of @str.
Parameters
str
a UTF-8 encoded string
len
length of @str, in bytes, or -1 if @str is nul-terminated.