How can I retrieve (and conditionally act on) the language of my document?

Question

I have a collection of documents that share a common style file that has all the functions and templating shared by this particular collection. The majority of these are all in the same language, but o handful of them are actually translations of the others. I would like to keep using the same style include file, but a few tidbits (for example in the footer and title sheet) need to be adjusted per-language.

I'm using polyglossia¹, and each document has its own language declaration using \setmainlanguage{} (in my case, mostly to Turkish). Is there some way to retrieve what language has been set and conditional output different strings based on which language is the document default?

¹ _{Actually for some reason my style file also has \usepackage[turkish]{babel}, which seems to be should be redundant and potentially a conflict with polyglossia; maybe I should sort out why that got in there while I'm messing with this!}

Answer 1

polyglossia stores the main language name in the macro \xpg@main@language, so it's easy to achieve what you want.

Example:

\documentclass{article}

\usepackage{xstring}

\usepackage{fontspec}

\usepackage{polyglossia}
\setmainlanguage{turkish}

\makeatletter
\newcommand{\mainlanguage}{\xpg@main@language}
\makeatother

\begin{document}

This document is written in \mainlanguage.

\IfStrEq{\mainlanguage}{turkish}{Yes, it's Turkish!}{No, it's not Turkish!}

\end{document}

Output:

As a side note, don't use babel if you're using polyglossia already...