[XeTeX] Defining ExtGState objects

[Zdenek Wagner]

Hello,
I want to define ExtGState objects via \special{pdf: ...}. The minimal
document is:

\documentclass{article}
\special{pdf: object @opoff << /Type /ExtGState /op false /OP false /OPM 0 >>}
\special{pdf: object @opon << /Type /ExtGState /op true /OP true /OPM 1 >>}
\special{pdf: object @extgs << /GSko @opoff 0 R /GSop @opon 0 R >>}
\special{pdf: put @resources << /ExtGState @extgs 0 R >>}
\begin{document}
A
\end{document}

The requested output (achieved by pdftex) is
% 1 0 obj
<< /Type /ExtGState /op false /OP false /OPM 0 >>
% 3 0 obj
<< /Type /ExtGState /op true /OP true /OPM 1 >>
% 4 0 obj
 << /GSko 1 0 R /GSop 3 0 R >>

However, xdvipdfmx reports this error:
$ xdvipdfmx -vv -z0 test-xetex
<FONTMAP:pdftex.map><FONTMAP:cid-x.map>DVI Comment:  XeTeX output
2011.09.07:1234
test-xetex.xdv -> test-xetex.pdf
<AGL:texglyphlist.txt>[1
** WARNING ** Could not find a name object.
** WARNING ** Could not find a key in dictionary object.
** WARNING ** Could not find an object definition for "extgs".
** WARNING ** Interpreting special command object (pdf:) failed.
** WARNING ** >> at page="1" position="(133.768, 717.088)" (in PDF)
** WARNING ** >> xxx "pdf: object @extgs << /GSko @opoff 0 R /GSop @opon 0 R >>"
** WARNING ** >> Reading special command stopped around >><< /GSko
@opoff 0 R /GSop @opon 0 R >><<

Current input buffer is -->pdf: object @extgs << /GSko @opoff 0 R
/GSop @opon...<--

** WARNING ** Could not find a name object.
** WARNING ** Could not find a key in dictionary object.
** WARNING ** Missing (an) object(s) to put into "resources"!
** WARNING ** Interpreting special command put (pdf:) failed.
** WARNING ** >> at page="1" position="(133.768, 717.088)" (in PDF)
** WARNING ** >> xxx "pdf: put @resources << /ExtGState @extgs 0 R >>"
** WARNING ** >> Reading special command stopped around >><<
/ExtGState @extgs 0 R >><<

Current input buffer is -->pdf: put @resources << /ExtGState @extgs 0 R >><--
<cmr10 at 9.96pt(TFM:cmr10[/usr/local/texlive/2010/texmf-dist/fonts/tfm/public/cm/cmr10.tfm])
fontmap: cmr10 -> cmr10.pfb

pdf_font>> Simple font "cmr10.pfb" enc_id=<builtin,-1> opened at
font_id=<cmr10,0>.
>]
** WARNING ** Unresolved object reference "extgs" found!!!
(cmr10.pfb[CMR10][built-in][Type1][3 glyphs][482 bytes])
1856 bytes written

** WARNING ** 1 memory objects still allocated

The PDF files from pdflatex and xelatex are available from
http://hroch486.icpf.cas.cz/overprint/ (with compresslevel set to
zero).

What am I doing wrong?

-- 
Zdeněk Wagner
http://hroch486.icpf.cas.cz/wagner/
http://icebearsoft.euweb.cz