[XeTeX] xdvipdfmx warnings..

[Jjgod Jiang]

Hi Jonathan,

May be I should open a new thread for this, but since it's also related
to xdvipdfmx...

I wondering if you have noticed dvipdfmx (and xdvipdfmx, of course)
has an extension to the orginial DVI opcodes call DIR (defined to 255)
used to specify the writing direction (horizonal/vertical, etc), since xetex
for Linux don't have vertical text layout support currently, I think making
use of this extension might be the quickest way to support this.

>From the documentation (and XeTeX_mac.c) I noticed that xetex
implement this feature throught "/vertical" parameter when specifying
a font, IMHO, it's not the best solution, since in a CJK document which
requires vertical layout support might use horizonal layout text using
the same font, using "/vertical" forced us to create two font instance
for the same font (and increase PDF file size).

I suggest we could add a new XeTeX primitive like \XeTeXwritingmode
to switch between horizonal and vertical layout mode.

(the dvipdfmx WMODE extension don't have many documentation yet,
dpxunicode.pdf might be a point to start..
I guess you can figure out the idea by reading dvi.c and pdfdev.c in
xdvipdfmx, A TeX extension for Japanese "p-TeX" used this feature too.)

J.