[XeTeX] a package for transition ryles based on unicode block (allowing amongst other things automatic font switching between languages)

[Michiel Kamermans]

Vafa Khalighi wrote:
>
> Thanks heaps for your quck answer.
>
> This is something I tried but still typesets the Persian sentense from 
> left to Right instead Right to left.
I shall have a look at this. Environments may need some protected to 
prevent things from going screwy, but I also see the following:

...
\setTransitionsForArabic{\setRTL\fontspec[Script=Arabic]{Arial}}{\setLTR}
\begin{document}
این یک آزمایش است.
...

yields a PDF with:

نﯾا ﮏﯾ شﯾﺎﻣزآ .تﺳ

The reason for this is that the space is a character from the Basic 
Latin block. As already pointed out in the documentation, ucharclasses 
will produce questionable results when using languages that overlap with 
others in the document, such as Vietnamese, or in this case Arabic.

In order for ucharclasses to be genuinely useful in these settings, it 
may need some kind of command for temporarily reassigning overlap 
punctuation to a specific class or informal group... but that's going to 
need a bit more thinking.

- Mike