[XeTeX] A XeTeX bug or a MiKTeX bug?

[Jonathan Kew]

On 27 Apr 2008, at 10:14 am, VAFA KHALIGHI wrote:

> If You use MiKTeX (updated at 2008-02-26) and you typeset persian  
> or arabic where you need to have ZERO WIDTH NON-JOINER between some  
> words, it does the job well. But if you update MiKTeX (let's say  
> today) and do the same as before it makes a gray like vertical line  
> between the words that you used to have ZERO WIDTH NON-JIONER  
> between them. I actually have put an example on the web and you can  
> get it from
> http://tex3.141592.googlepages.com/BeamerPersianPresentation.zip
>
> I have done this by using the newly updated version of MiKTeX and  
> when you look at the pdf file, you will observe the those gray  
> vertical lines that I was talking about.
>
> So is this a XeTeX bug or a MiKTeX bug?
>

The line you are seeing is the glyph provided for U+200C (zero width  
non-joiner) in the Roya font. In earlier versions of the ICU layout  
library, these glyphs were filtered out and never displayed, but as a  
result of some changes in v3.8 they now remain in the text, and so if  
the font has a visible glyph rather than a zero-width, blank one, you  
see it on the page.

http://bugs.icu-project.org/trac/ticket/6023 shows that this is  
considered an ICU layout bug, and the behavior has been changed  
again. I have just applied the patch from that ticket to the xetex  
repository, so when MikTeX (or other distributions) is updated to v. 
0.998.1, the problem should go away.

One possible solution in the meantime is to implement ZWNJ at the  
macro level; a simple version might be

     \catcode"200C=\active
     \def^^^^200c{\hskip0pt\relax}

though if you need it to be "robust" in LaTeX terms, a bit more care  
may be needed.

JK

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