<parameter>lang</parameter> should be of the form Ll-Tt where Ll is a
two or three letter language from ISO 639 and Tt is a territory from ISO
3166.
+@SINCE@ 2.9.0
@@
@RET@ FcLangSet *
@PURPOSE@ Add langsets
@DESC@
Returns a set including only those languages found in either <parameter>ls_a</parameter> or <parameter>ls_b</parameter>.
+@SINCE@ 2.9.0
@@
@RET@ FcLangSet *
@PURPOSE@ Subtract langsets
@DESC@
Returns a set including only those languages found in <parameter>ls_a</parameter> but not in <parameter>ls_b</parameter>.
+@SINCE@ 2.9.0
@@
@RET@ FcLangResult
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.
+@SINCE@ 2.9.91
+@@
@RET@ FcStrSet *
@FUNC@ FcLangSetGetLangs
@PURPOSE@ Normalize the language string
@DESC@
Returns a string to make <parameter>lang</parameter> suitable on fontconfig.
+@SINCE@ 2.10.91
@@
@RET@ const FcCharSet *