[XeTeX] XeTeX maintenance

[Philip Taylor]

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.

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.

** Phil.