In answering this question: Change language by clicking a button. It was necessary to obtain a list of languages for which translations were available (i.e. their po/mo files were present in
So how can you obtain that list?
Clearly by 'available' we can only mean that their
po/mo files are present - and it's not a concern if every plug-in also provides a translation for that language (interesting to see how you might do this though).
The list was originally intended for us in a drop-down, whereby a user could select from a list of (available) languages. So the human readable form of the language as well would be a bonus. But I think this is probably not possible.
View the question linked to above for demonstration of the current method used.