[XeTeX] Issue with Arabic Typography

[وفا خلیقی]

Sorry for repeating the same question again, but since I did not get
any response, I will repeat it gain. The answer does not need to be
detailed, it can be either "yes, you can do this in xetex" or "no, you
can not do it in xetex".



Hi

I recieved this email from one of the users and he believes that is a bug.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Dear Mr. Khalighi

   This is Massoud Babaie-Zadeh. I was one of the people active in preparing
FarsiTeX.

   First of all, thank you very much for your efforts in preparing XePersian
package. I hope that with your efforts, we will have finally a complete
Persian typesetting system compatible with all latex packages.

   I send you this email to inform you about (according me) a very important
bug in XePersian. This bug existed also in the very early versions of
FarsiTeX.   I think that correcting it in XePersian should not be difficult
for you, and needs just that someone signals the existence of this bug.

    This bug is related to the difference between Persian and English in
adjusting the end of lines. In English, for stretching a line, some spaces
(glue) are added between the words. In Persian, however, some letters inside
the words are stretched (what is called in Persian calligraphy a
"KESHIDEH"). Adding spaces between words to adjust a Persian line produces
less beautiful documents (and I guess that for this reason you have disabled
it in XePersian). However, the "Keshideh" system does not exist in
XePersian. (In MS-Word this system existed even in its very old versions on
Win3.1, and without implementing it in FarsiTeX, the output was less
beautiful even than those old MS-Word outputs).

    As a demonstration, please find attached 2 examples prepared by FarsiTeX
and XePersian. For FarsiTeX, I prefer that you look at the .ps output,
because the pdf version is not very well displayed, but in .ps and also in
print it has no problem.

    Just as a note: I don't remember, but I think that tex can itself
support such a thing (changing its default glue system), and adding some
kind of `rule' between the letters of the words. In first implementation
FarsiTeX, it had been used. But since such a system does not work for
outlined fonts ("Font-hayeh too-khaali"), in the late versions of FarsiTeX
the team has added a special character to each font for doing this task.
Since you use standard fonts, maybe the second one is not very easy (I am
not sure however), but even adding the first system solves the problem in
99% of cases. I think that for more details, it would be very nice if you
contact Roozbeh Pournader (I think also that some part of this job is done
in Farsitex during the conversion from ftx to tex, but I don't know how much
it is essential).

    Another note: When you see some discontinuity between the letters in the
pdf (or dvi) of the output of FarsiTeX, it is not a bug:  it is in fact this
stretching character which has been added between almost any two letters of
the words to adjust the line.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


So is this the XePersian's bug or it has got to be fixed inside the xetex
engine?

and How can I fix it?

-- 
VK
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