latex的ps宏包中,这到底是什么函数?

代码:

\documentclass{article}
\usepackage{fontspec}
\setmainfont{WenQuanYi Micro Hei}

\begin{document}
Cowards die many times before their deaths.\\

懦夫在未死之前，已身历多次死亡的恐怖了。
\end{document}

代码:

ubuntu@ubuntu:~$ xelatex test1.tex
This is XeTeX, Version 3.1415926-2.2-0.9997.4 (TeX Live 2010)
restricted \write18 enabled.
entering extended mode
(./test1.tex
LaTeX2e <2009/09/24>
Babel <v3.8l> and hyphenation patterns for english, dumylang, nohyphenation, ge
rman-x-2009-06-19, ngerman-x-2009-06-19, basque, catalan, pinyin, ukenglish, us
englishmax, french, galician, german, ngerman, swissgerman, italian, latin, spa
nish, loaded.
(/usr/local/texlive/2010/texmf-dist/tex/latex/base/article.cls
Document Class: article 2007/10/19 v1.4h Standard LaTeX document class
(/usr/local/texlive/2010/texmf-dist/tex/latex/base/size10.clo))
(/usr/local/texlive/2010/texmf-dist/tex/latex/fontspec/fontspec.sty
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/expl3.sty
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3names.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/etex-pkg/etex.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3basics.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3expan.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3tl.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3intexpr.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3quark.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3seq.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3toks.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3int.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3prg.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3clist.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3token.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3prop.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3msg.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3io.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3skip.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3box.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3keyval.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3keys.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3precom.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3xref.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3file.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/expl3/l3fp.sty)
(/usr/local/texlive/2010/texmf-dist/tex/latex/tools/calc.sty))
(/usr/local/texlive/2010/texmf-dist/tex/latex/xpackages/xbase/xparse.sty)
(/usr/local/texlive/2010/texmf-dist/tex/generic/kastrup/binhex.tex)
(/usr/local/texlive/2010/texmf-dist/tex/latex/xkeyval/xkeyval.sty
(/usr/local/texlive/2010/texmf-dist/tex/generic/xkeyval/xkeyval.tex
(/usr/local/texlive/2010/texmf-dist/tex/generic/xkeyval/keyval.tex)))
(/usr/local/texlive/2010/texmf-dist/tex/latex/fontspec/fontspec-patches.sty
(/usr/local/texlive/2010/texmf-dist/tex/latex/base/fixltx2e.sty))
(/usr/local/texlive/2010/texmf-dist/tex/latex/base/fontenc.sty
(/usr/local/texlive/2010/texmf-dist/tex/latex/euenc/eu1enc.def)
(/usr/local/texlive/2010/texmf-dist/tex/latex/euenc/eu1lmr.fd))
fontspec.cfg loaded.
(/usr/local/texlive/2010/texmf-dist/tex/latex/fontspec/fontspec.cfg))
(./test1.aux)
Underfull \hbox (badness 10000) in paragraph at lines 6--7

[1] (./test1.aux) )

** WARNING ** TrueType post table name index 32768 > 32767
(see the transcript file for additional information)
Output written on test1.pdf (1 page).
Transcript written on test1.log.