[XeTeX] XeTeX, \XeTeXprotrudechars, \rpcode, etc.

[Philip Taylor]

Good morning Thành  --

I have for some time been trying to get to the bottom of the mysterious
new primitives in XeTeX that include \XeTeXprotrudechars, \rpcode, etc.
The only "documentation" of these is a brief e-mail from JK dated
Mon May 3 01:12:46 CEST 2010 :

	http://tug.org/pipermail/xetex/2010-May/016465.html

in which he mentions that they have been added.  Despite the fact that
they have therefore been around for about four years, they are still
not documented in /The XƎTEX reference guide/, and Khaled today wrote :

>  From me: simply because I know near nothing about them.

Vafa then noted :

> If I recall correctly, Hàn Thế Thành added these primitives to XeTeX;
> therefore he knows them best.

and so I am pursuing it with you.

Are you able to point me at any formal documentation for this set of
primitives to which I can refer Khaled, Will et al., in the hopes
that they will finally be documented for TeX Live 2014, and are
you also aware of any documentation discussing how hyperlinks
can be embedded using XeTeX, another apparently undocumented feature
that is successfully exploited by "hyperref", "eplain", etc., yet
for which no primitive-level documentation seems to exist.

** Phil.