[XeTeX] xetex arabic fonts issue

[Khaled Hosny]

On Sat, Jun 26, 2010 at 07:58:13PM -0700, Jonathan Kew wrote:
> On 26 Jun 2010, at 16:46, Khaled Hosny wrote:
> 
> > On Sat, Jun 26, 2010 at 03:04:05PM -0700, wodzicki at math.berkeley.edu wrote:
> >> 
> >>> My guess is that you have an old version of the font installed somewhere.
> >>> Having to different version of the same font installed is known to cause
> >>> this kind of issues with xetex, deleting the old version(s) is enough
> >>> to solve this issue.
> >>> 
> >>> Regards,
> >>> Khaled
> >> 
> >> "an old version" should not be understood literally. Two identical copies
> >> of the exactly same font: one, say, in the system fonts directory, and
> >> another one in the TeX distribution tree -- will cause this behavior.
> 
> I have not seen any evidence that this is so, and would be very surprised if this happens.
> 
> >> This
> >> is a very frustrating and well attested bug in XeTeX (which for some
> >> reason has been ignored so far by the XeTeX creator and maintainer).
> > 
> > Theoretically, if my previous "analysis" of this issue was correct, two
> > identical copies should not cause any problems, since both will have
> > the same glyph IDs. I should have said a different instead of old copy,
> > though.
> 
> Indeed. The problem may occur if two *different* versions of the "same" font (i.e., with the same font names, but different versions or different formats -- e.g., type 1 vs truetype) are installed. As I believe I have explained previously, it's possible that xetex will find one font during formatting, but then xdvipdfmx finds the other at PDF generation time, and the glyph IDs don't match.
> 
> Obviously, it would be better if the two programs were guaranteed to always find the same font for a given name, but ensuring this for all configurations and environments may not be as simple as it sounds. For now, at least, the *strong* recommendation is to have only ONE version of any given font installed.

I was thinking that xetex should always pass the full path to xdvipdfmx,
instead of relaying on the later finding the fonts on it own. But now I
think this would break xdv2pdf which can not load fonts by file path,
right?

Regards,
 Khaled

-- 
 Khaled Hosny
 Arabic localiser and member of Arabeyes.org team
 Free font developer