[XeTeX] fontspec_if_current_script or \fontspec_if_script functions of fontspec

[Will Robertson]

On 2011-09-17 18:44:48 +0930, VAFA KHALIGHI 
<vafaklg at gmail.com> said:

> Why this always returns "non-RTL script"?
> 
> \newif\if at Latin
> \fontspec_if_current_script:nTF {arab} {\@Latinfalse} {\@Latintrue}

I wondered if the documentation for this feature needed work, but it 
seems okay if a little terse: "Test whether the currently loaded font 
is using the specified raw OpenType script tag #1."

This is, you have to execute the conditional after you've selected the font:

\documentclass{article}
\usepackage{fontspec}
\ExplSyntaxOn
\def\test{
  \fontspec_if_current_script:nF {arab} {non-}
  RTL~ script
 }
\ExplSyntaxOff
\newfontfamily\rlfont[Script=Arabic]{XB Zar}
\newfontfamily\lrfont[Path,Script=Latin]{lmroman12-regular}
\begin{document}
{\rlfont\test}
{\lrfont\test}
\end{document}

Hope this helps,
Will