[XeTeX] XeTeX maintenance

[Joseph Wright]

On 26/04/2015 12:16, Philip Taylor wrote:
> 
> 
> Joseph Wright wrote:
> 
>> See for example details in
>> http://tex.stackexchange.com/questions/222286/what-are-the-incompatibilities-of-pdftex-xetex-and-luatex
>> for places where there are edge cases. The most obvious would be that
>> XeTeX requires the xdvipdfmx back-end (so differences at the \special
>> level), 
> 
> Yes, I accept that, but to the user (as I have argued elsewhere), XeTeX
> subsumes 'xdvipdfmx' -- the fact that they are, historically, two
> separate pieces of software and are separately maintained is a sad fact
> of life but not one that the user of XeTeX should be required to consider.

Still requires changes in a document, particularly one written for
pdfTeX in PDF mode (certainly for plain: for LaTeX of course this is
more transparent).

> but a simple piece of code
>>
>>     \def\"{0}\expandafter\def\csname^^^^^00022\endcsname{1}
>>     \ifnum\"=0 \message{tex82}\else\message{newstuff}\fi
>>
>> (ConTeXt wiki) gives different results with TeX90 and XeTeX due to
>> different treatment of more than two ^^ (catcode 7) in a row.
> 
> OK, agreed: by adding support for wider characters, some breakages will,
> almost of necessity occur, but I would respectfully argue that these are
> pathological cases that will not impact real-world documents.

My point though is that neither XeTeX nor indeed any other Unicode
TeX-like engine can be used as a direct replacement for an 8-bit engine:
contrast the fact that the standard engine for TeX Live is nowadays
pdfTeX used as a direct drop-in replacement for TeX90 (with the
exception of using "tex", which is Kunth's TeX unaltered). As such,
whilst new documents may be written using a Unicode engine, pdfTeX will
remain vital.

All that said, I am keen that some way is found to continue to work on
XeTeX. The problem is that WEB code is *hard* to work with!
--
Joseph Wright