Better factorize by reusing code rather than recreating a combo box
which does basically the same thing. I only added a boolean parameter to
retrieve only the sublist of manual language.
It also takes advantage of the self-translated language names from
initialization.
Improvements:
- setenv/getenv() are not thread-safe, hence they should be run only at
startup before any threading occurs.
- it is counter-productive to load the huge ISO-639 XML file each time
the user opens the Preferences dialog or the text tool options.
Showing the current system locale between square brackets in the
"System Language" item was causing some issues on some systems (showing
some very weird and long value).
This was mostly a cosmetic change anyway with limited gain. Let's
just get rid of it. The main part of the feature (each language
displayed in itself) is still there.
glib's g_getenv() doc says: "The returned string may be overwritten by
the next call to g_getenv(), g_setenv() or g_unsetenv()". And I do
g_setenv() calls just after, while I wish to keep the value intact.
As a consequence, even though the previous commit seemed to work just fine,
I duplicate the return value of g_getenv(), just to be on the safe side.
The trick works by temporarily resetting the current locale to localize
each language label in its own lang.
One exception is English that is equivalent to the "C" code, and we make
also some special exception for Chinese where there are very different
variant depending on the region.
I also ensure the "System Language" string is translated in whatever
language is the system actually set to.
Derive GimpTranslationStore from GimpLanguageStore. It lists the
installed GIMP translations. Also sort the list alphabetically
instead of relying on the XML file being sorted.
