[XeTeX] No (bidi) Arabic with titlesec?

[Juan Acevedo]

Hello everyone,

I wonder if anyone has a solution or workaround for the ongoing bidi--titlesec clash?

I had set a book last year, in English with lots of Arabic, and it was running fine a few months ago. Now titlesec stops working as soon as I load either arabxetex or polyglossia+arabic, so I guess the problem is with bidi. I downloaded v.1.1.6 from Vafa's website, to no avail. Here is a minimal example. As soon as you uncomment one of the highlighted lines, you will see that titlesec stops working (it should make the headings roman, centered and tiny).

%!TEX TS-program = xelatex
%!TEX encoding = UTF-8 Unicode
\documentclass{book}
\usepackage[rm,tiny,center]{titlesec}
%\usepackage{polyglossia}
%	\setdefaultlanguage{british}
%	\setotherlanguage{arabic}% TRY USING ME AND YOU'LL SEE!
%\usepackage{arabxetex}% TRY USING ME AND YOU'LL SEE!
\begin{document}
\chapter{PREFACE}
\end{document} 


Any way around this problem? 
If possible, I would love to stick to using titlesec, as I had fiddled quite a bit with it to get the formatting I wanted.
And I think at this stage (the book being otherwise ready), I must retain bidi.

¡Muchas gracias!
Juan