luatex 0.25.3

git-svn-id: svn://tug.org/texlive/trunk@7494 c570f23f-e606-0410-a88d-b1316a301751

3 files changed, 6734 insertions, 0 deletions

diff --git a/Master/texmf-dist/doc/luatex/luatexref-env.tex b/Master/texmf-dist/doc/luatex/luatexref-env.tex
new file mode 100644
index 00000000000..69ddd7496ca
--- /dev/null
+++ b/Master/texmf-dist/doc/luatex/luatexref-env.tex
@@ -0,0 +1,312 @@
+% engine=luatex
+
+\startenvironment luatexref-env
+
+\usemodule[abr-02]
+
+% \tex    : tex command
+% \lua    : native lua code
+% \luatex : lua lib, function, value defined in luatex
+
+\catcode`\_=12 % we will make a nice attribute for this kind of break stuff
+
+\setuptolerance[stretch,tolerant]
+
+\setuptype[lines=hyphenated] \setuptyping[lines=hyphenated]
+
+\let\lua    \type
+\let\luatex \type
+
+\def\|{\string|}
+\def\>{\string>}
+
+\def\showfields#1{\ctxlua
+    {   do
+            local t = string.split('#1',',')
+            local r = { }
+            for _,a in pairs(node.fields(t[1],t[2])) do
+                if not (a == 'id' or a == 'subtype' or a =='next' or a=='prev') then
+                    table.insert(r,'\\type{'.. a .. '}')
+                end
+            end
+            tex.sprint(table.concat(r, ', '))
+        end
+    }%
+}
+
+\def\todo#1%
+  {\dontleavehmode{\bf\red <TODO: #1>}}
+
+\setuplayout
+  [height=middle,
+   width=middle,
+   backspace=2cm,
+   topspace=2cm]
+
+\setuppagenumbering
+  [alternative=doublesided]
+
+\setupitemize[each][packed]
+
+\setupwhitespace[medium]
+
+\preloadtypescripts
+
+\definetypeface[mainfacenormal]  [ss][sans] [iwona]       [default]
+\definetypeface[mainfacenormal]  [rm][serif][palatino]    [default]
+\definetypeface[mainfacenormal]  [tt][mono] [modern]      [default][rscale=1.1]
+\definetypeface[mainfacenormal]  [mm][math] [iwona]       [default][encoding=default]
+
+\definetypeface[mainfacemedium]  [ss][sans] [iwona-medium][default]
+\definetypeface[mainfacenormal]  [rm][serif][palatino]    [default]
+\definetypeface[mainfacemedium]  [tt][mono] [modern]      [default][rscale=1.1]
+\definetypeface[mainfacemedium]  [mm][math] [iwona-medium][default][encoding=default]
+
+\definetypeface[mainfacenarrowtt][tt][mono] [modern] [default][rscale=1.1]
+
+\setupbodyfont[mainfacenormal,11pt]
+
+\definehead
+  [remark]
+  [subsubsubject]
+
+\setuphead [chapter]      [style=\mainfacemedium\bfd,color=blue]
+\setuphead [section]      [style=\mainfacemedium\bfc,color=blue]
+\setuphead [subsection]   [style=\mainfacemedium\bfb,color=blue]
+\setuphead [subsubsection][style=\mainfacemedium\bfa,color=blue]
+
+\setupheadertexts
+  []
+
+\setupcolors
+  [state=start]
+
+\setuptyping
+  [color=blue,
+]%   style=\mainfacenarrowtt]
+
+\definetyping[functioncall]
+
+\setuptype
+  [color=blue,
+]%   style=\mainfacenarrowtt]
+
+\definecolor[blue] [b=.5]
+\definecolor[red]  [r=.5]
+\definecolor[green][g=.5]
+\runMPgraphicstrue
+\startuseMPgraphic{lualogo}
+    color   luaplanetcolor ; luaplanetcolor := .5blue  ;
+    color   luaholecolor   ; luaholecolor   :=   white ;
+    numeric luaextraangle  ; luaextraangle  := 0 ;
+
+    vardef lualogo = image (
+        % Graphic design by A. Nakonechnyj. Copyright (c) 1998, All rights reserved.
+
+        save luaorbitcolor, d, r, p ; color luaorbitcolor ; numeric d, r, p ;
+
+        luaorbitcolor := .5luaholecolor ; d := sqrt(2)/4 ; r := 1/4 ; p := r/8 ;
+
+        fill fullcircle scaled 1 withcolor luaplanetcolor ;
+        draw fullcircle rotated 40.5 scaled (1+r) dashed evenly scaled p withpen pencircle scaled (p/2) withcolor luaorbitcolor ;
+        fill fullcircle scaled r shifted (d+1/8,d+1/8) rotated luaextraangle withcolor luaplanetcolor ;
+        fill fullcircle scaled r shifted (d-1/8,d-1/8) withcolor luaholecolor   ;
+    )  enddef ;
+
+\stopuseMPgraphic
+
+\startuseMPgraphic{luapage}
+    \includeMPgraphic{lualogo}
+
+    StartPage ;
+
+        fill Page withcolor (white-luaplanetcolor) ;
+
+        picture p ; p := lualogo xsized (3PaperWidth/5) ;
+        draw p shifted center Page shifted (0,-ypart center ulcorner p) ;
+
+    StopPage ;
+\stopuseMPgraphic
+
+\startuseMPgraphic{luanumber}
+    \includeMPgraphic{lualogo}
+%     luaextraangle := \realfolio*360/\lastpage ;
+    luaextraangle := 10 * ( (\realfolio-2)*36/(\lastpage-2) ) ;
+    picture p ; p := lualogo ;
+    setbounds p to boundingbox fullcircle ;
+    draw p ysized 1cm ;
+\stopuseMPgraphic
+
+\definelayer
+  [page]
+  [width=\paperwidth,
+   height=\paperheight]
+
+\setupbackgrounds
+  [leftpage]
+  [background=page]
+
+\setupbackgrounds
+  [rightpage]
+  [background=page]
+
+\startsetups pagenumber:right
+  \setlayerframed
+    [page]
+    [preset=rightbottom,offset=1cm]
+    [frame=off,height=1cm,offset=overlay]
+    {\useMPgraphic{luanumber}}
+  \setlayerframed
+    [page]
+    [preset=rightbottom,offset=1cm,x=1.5cm]
+    [frame=off,height=1cm,width=1cm,offset=overlay]
+    {\pagenumber}
+  \setlayerframed
+    [page]
+    [preset=rightbottom,offset=1cm,x=2.5cm]
+    [frame=off,height=1cm,offset=overlay]
+    {\getmarking[chapter]}% Lua\TeX\ Reference Manual}
+\stopsetups
+
+\startsetups pagenumber:left
+  \setlayerframed
+    [page]
+    [preset=leftbottom,offset=1cm,x=2.5cm]
+    [frame=off,height=1cm,offset=overlay]
+    {\getmarking[chapter]}
+  \setlayerframed
+    [page]
+    [preset=leftbottom,offset=1cm,x=1.5cm]
+    [frame=off,height=1cm,width=1cm,offset=overlay]
+    {\pagenumber}
+  \setlayerframed
+    [page]
+    [preset=leftbottom,offset=1cm]
+    [frame=off,height=1cm,offset=overlay]
+    {\useMPgraphic{luanumber}}
+\stopsetups
+
+\startsetups [titlepage]
+
+    \startstandardmakeup
+
+        \switchtobodyfont[mainfacemedium]
+        \definedfont[Bold at .08\paperheight] \setupinterlinespace
+
+        \setlayer[page]{\useMPgraphic{luapage}}
+
+        \setlayerframed
+          [page]
+          [preset=middletop,
+           voffset=.05\paperheight]
+          [align=middle,
+           foregroundcolor=blue,
+           frame=off]
+          {Lua\TeX\\Reference}
+
+        \definedfont[Bold at 24pt] \setupinterlinespace
+
+        \setlayerframed
+          [page]
+          [preset=middletop,
+           voffset=.35\paperheight]
+          [align=middle,
+           foregroundcolor=blue,
+           frame=off]
+          {\doifsomething
+               {\getvariable{document}{snapshot}}
+               {snapshot \getvariable{document}{snapshot}}%
+           \doifsomething
+               {\getvariable{document}{beta}}
+               {beta \getvariable{document}{beta}}%
+            }
+
+    \stopstandardmakeup
+
+    \startstandardmakeup
+
+        \raggedleft
+
+        \definedfont[Bold at 48pt] \setupinterlinespace
+
+        \start \blue Lua\TeX \endgraf Reference \endgraf Manual \stop
+
+        \blank
+
+        \definedfont[Bold at 24pt] \setupinterlinespace
+
+        \blank
+
+        \vfill
+
+        \definedfont[Bold at 12pt] \setupinterlinespace
+
+        copyright: Lua\TeX\ development team \endgraf
+        more info: www.luatex.org \endgraf
+        version: \currentdate \doifsomething{\getvariable{document}{snapshot}}{(snapshot \getvariable{document}{snapshot})} \endgraf
+
+    \stopstandardmakeup
+
+    \setupbackgrounds
+      [leftpage]
+      [setups=pagenumber:left]
+
+    \setupbackgrounds
+      [rightpage]
+      [setups=pagenumber:right]
+
+\stopsetups
+
+\def\nonterminal#1>{\mathematics{\langle\hbox{{\rm #1}}\rangle}}
+
+\ifx\directlua\undefined
+
+  \definetyping[syntax]
+  \definetype[syntax]
+
+\else
+
+    % taco's brainwave -)
+
+    \newcatcodetable\syntaxcodetable
+
+    \def\makesyntaxcodetable
+      {\begingroup
+       \catcode`\<=13 \catcode`\|=12
+       \catcode`\!= 0 \catcode`\\=12
+       \savecatcodetable\syntaxcodetable
+       \endgroup}
+
+    \makesyntaxcodetable
+
+    \def\startsyntax {\begingroup\catcodetable\syntaxcodetable  \dostartsyntax}
+    \def\syntax      {\begingroup\catcodetable\syntaxcodetable  \dosyntax}
+
+    \def\syntaxenvbody#1%
+      {\par
+       \tt
+       \startnarrower
+       {\blue #1}%
+       \stopnarrower
+       \par}
+
+    \def\syntaxbody#1%
+      {{\blue \tt #1}}
+
+    \bgroup \catcodetable\syntaxcodetable
+
+    !gdef!dostartsyntax#1\stopsyntax{!let<!nonterminal!syntaxenvbody{#1}!endgroup}
+    !gdef!dosyntax     #1{!let<!nonterminal!syntaxbody{#1}!endgroup}
+
+    !egroup
+
+\fi
+
+\setupinteraction[state=start]
+\placebookmarks[chapter,section,subsection]
+
+% Hans doesn't like the bookmarks opening by default
+% \setupinteractionscreen[option=bookmark]
+
+\stopenvironment
+
diff --git a/Master/texmf-dist/doc/luatex/luatexref-t.pdf b/Master/texmf-dist/doc/luatex/luatexref-t.pdf
new file mode 100644
index 00000000000..69a6986e78c
--- /dev/null
+++ b/Master/texmf-dist/doc/luatex/luatexref-t.pdf
diff --git a/Master/texmf-dist/doc/luatex/luatexref-t.tex b/Master/texmf-dist/doc/luatex/luatexref-t.tex
new file mode 100644
index 00000000000..b89015a0d56
--- /dev/null
+++ b/Master/texmf-dist/doc/luatex/luatexref-t.tex
@@ -0,0 +1,6422 @@
+% engine=luatex language=uk
+
+% TODO: fix layout of function legend descriptions
+
+\environment luatexref-env
+
+\def\CFF{\kap{cff}}
+\def\PATGEN{\kap{patgen}}
+\def\MP{MetaPost}
+
+\dontcomplain
+
+\catcode`\_=12
+ 
+\setvariables
+  [document]
+  [beta=0.25.3]
+
+\starttext
+
+\setups[titlepage]
+
+\title{Contents}
+
+\placecontent[criterium=text,level=subsection]
+
+\chapter{Introduction}
+
+\startframedtext[framecolor=red,foregroundcolor=red,width=\hsize,font=\tfa]
+
+This book will eventually become the reference manual of \LUATEX. At
+the moment, it simply reports the behavior of the executable
+matching the snapshot or beta release date in the title page.
+
+\blank
+
+Features may come and go. The current version of \LUATEX\ is not meant
+for production and users cannot depend on stability, nor on
+functionality staying the same.
+
+\blank
+
+Nothing is considered stable just yet. This manual
+therefore simply reflects the current state of the executable. {\bs
+Absolutely nothing\/} on the following pages is set in stone. When the
+need arises, anything can (and will) be changed without prior notice.
+
+\blank
+
+\bf If you are not willing to deal with this situation, you should wait 
+for the stable version. Currently we expect the first release to be
+available sometime in the summer of~2008.
+
+\stopframedtext
+
+\blank[2*line]
+
+\LUATEX\ consists of a number of interrelated but (still) distinguishable
+ parts:
+
+\startitemize[packed]
+\item \PDFTEX\ version 1.40.3 % hahe: still 1.40.3?
+\item \ALEPH\ RC4 (from the \TEXLIVE\ repository)
+\item \LUA\ 5.1.2 ($+$ coco 1.1.3) % hahe: still 5.1.2?
+\item Dedicated \LUA\ libraries
+\item Various \TEX\ extensions
+\item Parts of \FONTFORGE\ 2007.06.07
+\item Newly written compiled source code to glue it all together
+\stopitemize
+
+Neither \ALEPH's I/O translation processes, nor tcx files, nor
+\ENCTEX\ can be used, these encoding|-|related functions are
+superseded by a \LUA|-|based solution (reader callbacks).  Also, some
+experimental \PDFTEX\ features are removed. These can be implemented
+in Lua instead.
+
+\chapter{Basic \TEX\ enhancements}
+
+
+\section{Version information}
+
+There are three new primitives to test the version of \LUATEX:
+
+\starttabulate[|l|p|]
+\NC \bf primitive         \NC \bf explanation \NC\NR
+\NC \type{\luatexversion}   \NC A combination of major and minor number, as in pdfTeX. 
+                              Current value: {\bf\the\luatexversion} \NC\NR
+\NC \type{\luatexrevision}  \NC The revision, as in pdfTeX. 
+                              Current value: {\bf\luatexrevision} \NC\NR
+\NC \type{\luatexdatestamp} \NC A combination of the local date and hour when
+                              the current executable was compiled,
+                              the syntax is identical to \tex{luatexrevision}.
+                              Value for the executable that generated this 
+                              document: {\bf\luatexdatestamp}. \NC\NR
+\stoptabulate
+
+Note that the \type{\luatexdatestamp} depends on both the compilation
+time and compilation place of the current executable, it is defined in
+terms of the local time. The purpose of this primitive is solely to be
+an aid in the development process, do not use it for anything besides
+debugging.
+
+\section{\UNICODE\ text support}
+
+Text input and output is now considered to be \UNICODE\ text, so
+input characters can use the full range of \UNICODE\ ($2^{20}+2^{16} =
+\hbox{10FFFF} = 1114111$). % hahe: wrong +/- 1
+
+Later chapters will talk of characters and glyphs. Although these are
+not the interchangeable, they are closely related. During typesetting,
+a character is always converted to a suitable graphic representation
+of that character in a specific font. However, while processing a list
+of to-be-typeset nodes, its contents may still be seen as a character.
+Inside \LUATEX\ there is not yet a clear separation between the two
+concepts. Until this is implemented, please do not be too harsh on
+us if we make errors in the usage of the terms.
+ 
+Note: for now, it only makes sense to use values above the base plane
+(\type{"0xFFFF}) for \tex{mathcode} and \tex{catcode} assignments,
+since the hyphenation patterns are still limited to max.\ 16-bit
+values, so the other commands will not know what to do with those high
+values.
+
+A few primitives are affected by this, all in a similar fashion: each of
+them has to accomodate for a larger range of acceptable numbers.  For
+instance, \tex{char} now accepts values between~0 and 1114111. This
+should not be a problem for well|-|behaved input files, but it could
+create incompatibilities for input that would have generated an error
+when processed by older \TEX|-|based engines. The maximum number of
+allocations is \type {"10FFFF} or $2^{20}+2^{16}$ (21 bits). The % hahe: wrong?
+maximum value that can be assigned are:
+
+% hahe: all below wrong by 1?
+\starttabulate[|l|l|l|l|]
+\NC \bf primitive     \NC \bf bits \NC \bf hex     \NC \bf numeric                     \NC\NR
+\NC \tex{char}        \NC 21       \NC \tt ~10FFFF \NC $2^{20}+2^{16}$                 \NC\NR
+\NC \tex{chardef}     \NC 21       \NC \tt ~10FFFF \NC $2^{20}+2^{16}$                 \NC\NR
+\NC \tex{lccode}      \NC 21       \NC \tt ~10FFFF \NC $2^{20}+2^{16}$                 \NC\NR
+\NC \tex{uccode}      \NC 21       \NC \tt ~10FFFF \NC $2^{20}+2^{16}$                 \NC\NR
+\NC \tex{sfcode}      \NC 15       \NC \tt ~~~7FFF \NC $2^{15}$                        \NC\NR
+\NC \tex{catcode}     \NC ~4       \NC \tt ~~~~~~F \NC $2^{4}$                         \NC\NR
+\stoptabulate
+
+As far as the core engine is concerned, all input and output to text
+files is \UTF-8 encoded. Input files can be pre|-|processed using the
+\luatex{reader} callback. This will be explained in a later chapter.
+
+Output in byte|-|sized chunks can be achieved by using characters just
+outside of the valid unicode range, starting at the value 1.114.112 
+(0x110000). When the times comes to print a character $c>=1.114.112$, \LUATEX\ will
+actually print the single byte corresponding to $c-1.114.112$.
+
+Output to the terminal uses \type{^^} notation for the lower control
+range ($c<32$), with the exception of \type{^^I}, \type{^^J} and
+\type{^^M}.  These are considered \quote{safe} and therefore printed as-is.
+
+Normalization of the \UNICODE\ input can be handled by a macro package
+during callback processing (this will be explained in \in{section}[iocallback]).
+
+\section{Wide math characters}
+
+Text handling is now extended up to the full \UNICODE\ range, but math mode
+deals mostly with glyphs in fonts directly and fonts tend to be 16-bit
+at maximum. The extension from 8-bit to 16-bit was already present in
+\ALEPH\ by means of a set of extra primitives.
+
+Therefore, the math primitives from \TEX\ and \ALEPH\ are kept mostly
+as they are, except for the ones that convert from input to math
+commands like \type{matcode} and \type{omathcode}. The traditional
+\TEX\ primitives are unchanged, their arguments are upscaled from 8~to 
+16~bits internally (as in \ALEPH).
+
+% hahe: again wrong by 1?
+\starttabulate[|l|l|l|l|]
+\NC \bf primitive     \NC \bf max index/bits \NC \bf hex          \NC \bf numeric                       \NC\NR
+\NC \tex{mathchardef} \NC 15             \NC \tt~~~8000           \NC $2^{3}*2^{4}*2^{8}$               \NC\NR
+\NC \tex{mathcode}    \NC 8=15           \NC \tt~~~~~FF = ~~~800  \NC $2^{3}*2^{4}*2^{8}$               \NC\NR
+\NC \tex{delcode}     \NC 8=24           \NC \tt~~~~~FF = ~FFFFF  \NC $2^{4}*2^{8}*2^{4}*2^{8}$         \NC\NR
+\NC \tex{mathchar}    \NC 15             \NC \tt~~~7FFF           \NC $2^{3}*2^{4}*2^{8}$               \NC\NR
+\NC \tex{mathaccent}  \NC 15             \NC \tt~~~7FFF           \NC $2^{3}*2^{4}*2^{8}$               \NC\NR
+\NC \tex{delimiter}   \NC 27             \NC \tt7FFFFFF           \NC $2^{3}*2^{4}*2^{8}*2^{4}*2^{8}$   \NC\NR
+\NC \tex{radical}     \NC 27             \NC \tt7FFFFFF           \NC $2^{3}*2^{4}*2^{8}*2^{4}*2^{8}$   \NC\NR
+\NC \tex{omathchardef}\NC 27             \NC \tt8000000           \NC $2^{3}*2^{8}*2^{16}$              \NC\NR
+\NC \tex{omathcode}   \NC 21=27          \NC \tt~10FFFF = 8000000 \NC $2^{3}*2^{8}*2^{16}$              \NC\NR
+\NC \tex{odelcode}    \NC 21=24+24       \NC \tt~10FFFF = ~FFFFFF \NC $2^{8}*2^{16}$                    \NC\NR
+\NC                   \NC                \NC \tt~~~~~~~ + ~FFFFFF \NC \quad $+ 2^{8}*2^{16}$            \NC\NR
+\NC \tex{omathchar}   \NC 27             \NC \tt7FFFFFF           \NC $2^{3}*2^{8}*2^{18}$              \NC\NR
+\NC \tex{omathaccent} \NC 27             \NC \tt7FFFFFF           \NC $2^{3}*2^{8}*2^{18}$              \NC\NR
+\NC \tex{odelimiter}  \NC 27+24          \NC \tt7FFFFFF + ~FFFFFF \NC $2^{3}*2^{8}*2^{16}+2^{8}*2^{16}$ \NC\NR
+\NC \tex{oradical}    \NC 27+24          \NC \tt7FFFFFF + ~FFFFFF \NC $2^{3}*2^{8}*2^{16}+2^{8}*2^{16}$ \NC\NR
+\stoptabulate
+
+\section{Extended tables}
+
+All traditional \TEX\ and \ETEX\ registers can be 16 bit numbers as in \ALEPH. The affected commands
+are:
+
+\startcolumns[n=4]
+\starttyping
+\count
+\dimen
+\skip
+\muskip
+\marks
+\toks
+\countdef
+\dimendef
+\skipdef
+\muskipdef
+\toksdef
+\box
+\unhbox
+\unvbox
+\copy
+\unhcopy
+\unvcopy
+\wd
+\ht
+\dp
+\setbox
+\vsplit
+\stoptyping
+\stopcolumns
+
+The same is true for the font-related \PDFTEX\ tables like \type{\rpcode} etc.
+
+\section{Attribute registers}
+
+Attributes are a completely new concept in \LUATEX. Syntactically,
+they behave a lot like counters: attributes obey \TEX's nesting stack
+and can be used after \tex{the} etc.\ just like the normal
+\tex{count} registers.
+
+\startsyntax
+\attribute <16-bit number> <optional equals> <31-bit number>!crlf
+\attributedef <csname> <optional equals> <16-bit number>
+\stopsyntax
+
+Conceptually, an attribute is either \quote{set} or \quote{unset}. Set
+attributes can only have values of~0 or more, otherwise they are
+considered unset and automatically remapped to an special negative
+value meaning \quote{unset} (currently that value is $-1$, but please
+test on negativity, not on a specific value).  All attributes start
+out in the \quote{unset} state (in \INITEX). 
+
+Attributes can be used as extra counter values, but their usefulness
+comes mostly from the fact that the numbers and values of all \quote{set}
+attributes are attached to all nodes created in their scope. These can
+then be queried from any \LUA\ code that deals with node
+processing. Future versions of
+\LUATEX\ will probably be using specific negative attribute ids for
+internal use. Further information about how to use attributes for node
+list processing from lua is given in~\in{chapter}[nodes].
+
+\subsection{Box attributes}
+
+Nodes typically receive the list of attributes that is in effect when
+they are created. This moment can be quite asynchronous. For example: in
+paragraph building, the individual line boxes are created after the
+\tex{par} command has been processed, so they will receive the list of
+attributes that is in effect then, not the attributes that were in
+effect in, say, the first or third line of the paragraph. 
+
+Similar situations happen in \LUATEX\ regularly. A few of the more
+obvious problematic cases are dealt with: the attributes for nodes
+that are created during hyphenation and ligaturing borrow their
+attributes from their surrounding glyphs, and it is possible to
+influence box attributes directly. 
+
+But many other inserted nodes, like the nodes resulting from math mode
+and alignments, are processed `out of order', and will have the
+attributes that are in effect at the precise moment of creation (which
+is often later than expected). This area needs studying, and is in
+fact one of the reasons for a beta at this moment.
+
+
+It is possible to fine-tune the list of attributes that are applied
+to a \type{hbox}, \type{vbox} or \type{vtop} by the use of the
+keyword \type{attr}. An example:
+
+\starttyping
+\attribute2=5
+\setbox0=\hbox {Hello}
+\setbox2=\hbox attr1=12 attr2=-1{Hello}
+\stoptyping
+
+This will set the attribute list of the box 2 to $1=12$, and the
+attributes of box 0 will be $2=5$. As you can see, assigning a
+negative value causes an attribute to be ignored.
+
+The \type{attr} keyword(s) should come before a \type{to} or
+\type{spread}, if that is also specified.
+
+\section{\LUA\ related primitives}
+
+In order to merge \LUA\ code with \TEX\ input, a few new primitives are
+needed. \LUATEX\ has support for 65536 separate \LUA\ interpreter
+states. States are automatically created based on the integer argument
+to the primitives \tex{directlua} and \tex{latelua}.
+
+
+\subsection{\tex{directlua}}
+
+The primitive \tex{directlua} is used to execute \LUA\ code immediately.
+The syntax is
+
+\startsyntax
+\directlua <16-bit number> <general text>
+\stopsyntax
+
+The \syntax{<general text>} is expanded fully, and then fed into the
+\LUA\ interpreter state indicated by the \syntax{<16-bit number>}. 
+If the state does not exist yet, it will be initialized
+automatically. After reading and expansion has been applied to the
+\syntax{<general text>}, the resulting token list is converted to a
+string as if it was displayed using \type{\the\toks}. On the \LUA\
+side, each \type{\directlua} block is treated as a separate chunk. 
+
+The conversion from and to a token list means that you normally can
+not use \LUA\ line comments (starting with \type{--}) within the
+argument, as there typically will be only one \quote{line}, so that comment
+will then run on until the end of the input. You will either need to
+use \TEX-style line comments (starting with \%), or change the \TEX\
+category codes locally.
+
+\startbuffer
+$\pi = \directlua0{tex.print(math.pi)}$
+\stopbuffer
+
+The \type{\directlua} command is expandable: the results of the \LUA\
+code become effective immediately. As an example, the following
+input:
+\typebuffer
+will result in
+\getbuffer
+
+Because the \syntax{<general text>} is a chunk, the normal \LUA\ error
+handling is triggered if there is a problem in the included code. The
+\LUA\ error messages should be clear enough, but the contextual 
+information is still pretty bad. Typically, you will only see the line
+number of the right brace at the end of the code. 
+
+While on the subject of errors: some of the things you can do inside
+\LUA\ code can break up \LUATEX\ pretty bad. If you are not careful
+while working with the node list interface, you may even end up with
+assertion errors from within the \TEX\ portion of the executable.
+
+\subsection{\tex{latelua}}
+
+\tex{latelua} stores \LUA\ code in a whatsit that will be processed
+inside the output routine. Its intended use is very similar to
+\tex{pdfliteral}. Within the \LUA\ code, you can print \PDF\ 
+statements directly to the \PDF\ file.
+
+\startsyntax
+\latelua <16-bit number> <general text>
+\stopsyntax
+
+\subsection{\tex{luaescapestring}}
+
+This primitive converts a \TEX\ token sequence so that it can be
+safely used as the contents of a \LUA\ string: embedded backslashes,
+double and single quotes, and newlines and carriage returns are
+escaped. This is done by prepending an extra token consisting of a
+backslash with category code~12, and for the line endings,
+converting them to \type{n} and \type{r} respectively. The token
+sequence is fully expanded.
+
+\startsyntax
+\luaescapestring <general text>
+\stopsyntax
+
+Most often, this command is not actually the best way to deal with the
+differences between the \TEX\ and \LUA. In very short bits of \LUA\
+code it is often not needed, and for longer stretches of \LUA\ code it
+is easier to keep the code in a separate file and load it using \LUA's
+\type{dofile}:
+\starttyping
+\directlua0 { dofile('mysetups.lua')}
+\stoptyping
+
+\subsection{\tex{closelua}}
+
+This primitive allows you to close a \LUA\ state, freeing all of its
+used memory.
+
+\startsyntax
+\closelua <16-bit number>
+\stopsyntax
+
+You cannot close the initial \LUA\ state~(0), attempts to do so
+will be silently ignored.
+
+States are never closed automatically except when a fatal out of
+memory error occurs, at which point \LUATEX\ will exit anyway.
+
+Also be aware that \LUA\ states are not closed immediately, but only
+when the \tex{output} routine comes into play next (because there may be
+pending \tex{latelua} calls).
+
+\section{New \ETEX\ primitives}
+
+\subsection{\tex{clearmarks}}
+
+This primitive clears a marks class completely, resetting all three
+connected mark texts to empty.
+
+\startsyntax
+\clearmarks <16-bit number>
+\stopsyntax
+
+\subsection{\tex{noligs} and \tex{nokerns}}
+
+These primitives prohibit ligature and kerning insertion at the time
+when the initial node list is built by \LUATEX's main control loop.
+They are part of a temporary trick and will be removed in the near
+future. For now, you need to enable these primitives when you want to
+do node list processing of \quote{characters}, where \TEX's normal
+processing would get in the way.
+
+\startsyntax
+\noligs <integer>!crlf
+\nokerns <integer>
+\stopsyntax
+
+
+\subsection{\tex{formatname}}
+
+\tex{formatname}'s syntax is identical to \tex{jobname}.
+
+In \INITEX, the expansion is empty. Otherwise, the expansion is the
+value that \tex{jobname} had during the \INITEX\ run that dumped the
+currently loaded format.
+
+\subsection{\tex{scantextokens}}
+
+The syntax of \tex{scantextokens} is identical to \tex{scantokens}.
+
+This is a slightly adapted version of \ETEX's \tex{scantokens}. The
+differences are:
+
+\startitemize
+\item The last (and usually only) line does not have a
+      \tex{endlinechar} appended
+\item \tex{scantextokens} never raises an EOF error,
+      and it does not execute \tex{everyeof} tokens.
+\item The \quote{.. while end of file ..} error tests are not executed, allowing
+      the expansion to end on a different grouping level or while a
+      conditional is still incomplete.
+\stopitemize
+
+
+\subsection{Catcode tables}
+
+Catcode tables are a new feature that allows you to switch to a
+predefined catcode regime in a single statement. You can have a
+practically unlimited number of different tables.
+
+The subsystem is backward compatible: if you never use the following
+commands, your document will not notice any difference in behavior
+compared to traditional \TEX.
+
+The contents of each catcode table is independent from any other
+catcode tables, and their contents is stored and retrieved from the
+format file.
+
+\subsubsection{\tex{catcodetable}}
+
+\startsyntax
+\catcodetable <28-bit number>
+\stopsyntax
+
+The \tex{catcodetable} switches to a different catcode table.
+Such a table has to be previously created using one of the two
+primitives below, or it has to be zero (table zero is initialized by
+\INITEX).
+
+\subsubsection{\tex{initcatcodetable}}
+
+\startsyntax
+\initcatcodetable <28-bit number>
+\stopsyntax
+
+The \tex{initcatcodetable} creates a new table with catcodes
+identical to those defined by \INITEX:
+
+\starttabulate[|l|l|l|l|]
+\NC~0\NC \type{_}                  \NC         \NC \tt escape        \NC\NR
+\NC~5\NC \tt\letterhat\letterhat M \NC return  \NC \tt car\_ret      \NC\NR
+\NC~9\NC \tt\letterhat\letterhat @ \NC null    \NC \tt ignore        \NC\NR
+\NC10\NC \tt <space>               \NC space   \NC \tt spacer        \NC\NR
+\NC11\NC {\tt a} -- {\tt z}        \NC         \NC \tt letter        \NC\NR
+\NC11\NC {\tt A} -- {\tt Z}        \NC         \NC \tt letter        \NC\NR
+\NC12\NC everything else           \NC         \NC \tt other         \NC\NR
+\NC14\NC \tt\letterpercent         \NC         \NC \tt comment       \NC\NR
+\NC15\NC \tt\letterhat\letterhat ? \NC delete  \NC \tt invalid\_char \NC\NR
+\stoptabulate
+
+The new catcode table is allocated globally: it will not go away after
+the current group has ended. If the supplied number is identical to
+the currently active table, an error is raised.
+
+\subsubsection{\tex{savecatcodetable}}
+
+\startsyntax
+\savecatcodetable <28-bit number>
+\stopsyntax
+
+\tex{savecatcodetable} copies the current set of catcodes to a
+new table with the requested number. The definitions in this new table
+are all treated as if they were made in the outermost level.
+
+The new table is allocated globally: it will not go away after the
+current group has ended. If the supplied number is the currently
+active table, an error is raised.
+
+\subsection{\tex{suppressfontnotfounderror}}
+
+\startsyntax
+\suppressfontnotfounderror = 1
+\stopsyntax
+
+If this new integer parameter is non-zero, then \LUATEX\ will not
+complain about font metrics that are not found. Instead it will
+silently skip the font assignment, making the requested csname for the
+font \type{\ifx} equal to \type{\nullfont}, so that it can be tested
+against that without bothering the user.
+
+\subsection{Font syntax}
+
+\LUATEX\ will accept a braced argument as a font name:
+
+\starttyping
+\font\myfont = {cmr10}
+\stoptyping
+
+This allows for embedded spaces, without the need for double quotes.
+Macro expansion takes place inside the argument.
+
+\section{Debugging}
+
+If \tex{tracingonline} is larger than 2, the node list display will
+also print the node number of the nodes.
+
+\chapter {\LUA\ general}
+
+\section[init]{Initialization}
+
+\subsection{\LUATEX\ as a \LUA\ interpreter}
+
+There are some situations that make \LUATEX\ behave like it is a \LUA\
+interpreter only:
+\startitemize[packed]
+\item If a \type{--luaonly} option is given on the commandline
+\item If the executable is named \type{texlua} (or \type{luatexlua})
+\item if the only non|-|option argument (file) on the commandline has the extension
+	\type{lua} or \type{luc}.
+\stopitemize
+
+In this mode, it will set \LUA's \type{arg[0]} to the found script
+name, pushing preceding options in negative values and the rest of the
+commandline in the positive values, just like the \LUA\
+interpreter.
+
+\LUATEX\ will exit immediately after executing the specified \LUA\
+script and is, in effect, a somewhat bulky standalone \LUA\
+interpreter with a bunch of extra preloaded libraries.
+
+\subsection{\LUATEX\ as a \LUA\ byte compiler}
+
+There are two situations that make \LUATEX\ behaves like the \LUA\
+byte compiler:
+\startitemize[packed]
+\item If a \type{--luaconly} option is given on the commandline
+\item If the executable is named \type{texluac}
+\stopitemize
+
+In this mode, \LUATEX\ is exactly like \type{luac} from the standalone
+\LUA\ distribution, except that it does not have the \type{-l} switch,
+and that it accepts (but ignores) the \type{--luaconly} switch.
+
+\subsection{Other commandline processing}
+
+When the \LUATEX\ executable starts, it looks for the \type{--lua}
+commandline option. If there is no \type{--lua} option, the
+commandline is interpreted in a similar fashion as in traditional
+\PDFTEX\ and \ALEPH. But if the option is present, \LUATEX\ will enter an
+alternative mode of commandline parsing in comparison to the standard
+web2c programs.
+
+In this mode, a small series of actions is taken in order. At first,
+it will only interpret a small subset of the commandline directly:
+
+\starttabulate[|l|p|]
+\NC \tt --lua=s    \NC load and execute a \LUA\ initialization script      \NC\NR
+\NC \tt --safer    \NC disable easily exploitable \LUA\ commands \NC\NR
+\NC \tt --help     \NC display help and exit                     \NC\NR
+\NC \tt --version  \NC display version and exit                  \NC\NR
+\stoptabulate
+
+Now it searches for the requested \LUA\ initialization script. If it
+can not be found using the actual name given on the commandline, a
+second attempt is made by prepending the value of the environment
+variable \type{LUATEXDIR}, if that variable is defined.
+
+Then it checks the \type{--safer} switch. You can use that to disable
+some \LUA\ commands that can easily be abused by a malicious document. At
+the moment, this switch \type{nil}s the following functions:
+
+\starttabulate[|l|l|]
+\NC \bf library \NC \bf functions                         \NC \NR
+\NC \tt os      \NC \tt execute exec setenv rename remove tmpdir \NC \NR
+\NC \tt io      \NC \tt popen output tmpfile              \NC \NR
+\NC \tt lfs     \NC \tt rmdir mkdir chdir lock touch      \NC \NR
+\stoptabulate
+
+And it makes \lua{io.open()} fail on files that are opened for
+anything besides reading.
+
+Next the initialization script is loaded and executed. From within the
+script, the entire commandline is available in the \LUA\ table
+\lua{arg}, beginning with \lua {arg[0]}, containing the name of the executable.
+
+Commandline processing happens very early on. So early, in fact, that
+none of \TEX's initializations have taken place yet. For that reason,
+the \luatex{tex}, \luatex{token}, \luatex{node} and \luatex{pdf}  tables 
+are off|-|limits during the execution of the startup file (they are
+nilled). Special care is taken that \luatex{texio.write} and
+\luatex{texio.write_nl} function properly, so that you can at least
+report your actions to the log file when (and if) it eventually
+becomes opened (note that \TEX\ does not even know its \tex{jobname}
+yet at this point). See \in{chapter}[libraries] for more information
+about the \LUATEX-specific \LUA\ extension tables. 
+
+The \LUA\ initialization script is loaded into \LUA\ state~0, and
+everything you do will remain visible during the rest of the run, with
+the exception of the aforementioned \luatex{tex}, \luatex{token},
+\luatex{node} and \luatex{pdf} tables: those will be initialized 
+to their documented state after the execution of the script. You
+should not store anything in variables or within tables with these
+four global names, as they will be overwritten completely.
+
+We recommend you use the startup file only for your own
+\TEX|-|independent initializations (if you need any), to parse the
+commandline, set values in the \luatex{texconfig} table, and register
+the callbacks you need. \LUATEX\ will fetch some of the other
+commandline options from the \luatex{texconfig} table at the end of
+script execution (see the description of the \luatex{texconfig} table
+later on in this document for more details on which ones exactly).
+
+Unless the \luatex{texconfig} table tells it not to start \KPATHSEA\
+at all (set \luatex{texconfig.kpse_init} to \type{false} for that),
+\LUATEX\ acts on three more commandline options after the
+initialization script is finished:
+
+\starttabulate[|l|l|]
+\NC \bf flag         \NC \bf meaning                           \NC \NR
+\NC \tt --fmt=s      \NC set the format name                   \NC \NR
+\NC \tt --progname=s \NC set the progname (only for \KPATHSEA) \NC \NR
+\NC \tt --ini        \NC enable \INITEX\ mode                  \NC \NR
+\stoptabulate
+
+In order to initialize the built|-|in \KPATHSEA\ library properly,
+\LUATEX\ needs to know the correct \quote{progname} to use, and for that it
+needs to check \type{--progname} (and \type{--ini} and \type{--fmt}, if
+\type{--progname} is missing).
+
+\section{\LUA\ changes}
+
+The C coroutine (COCO) patches from luajit are applied to the Lua core, the used
+version is 1.1.3.  See \hyphenatedurl{http://luajit.org/coco.html} for details.
+
+The \lua{read("*line")} function from the io library has been
+adjusted so that it is line|-|ending neutral: any of \type{LF}, \type
+{CR} or \type{CR+LF} are acceptable line endings.
+
+The \lua{tostring()} printer for numbers has been changed so that it
+returns~\type{0} instead of something like~\hbox{\type{2e-5}} (which confused \TEX\
+enormously) when the value is so small that \TEX\ cannot distinguish
+it from zero.
+
+Dynamic loading of \type{.so} and \type{.dll} files is disabled on
+all platforms.
+
+\lua{luafilesystem} has been extended with two extra boolean functions
+(\luatex{isdir(filename)} and \luatex{isfile(filename)}) and one extra
+string field in its attributes table (\type{permissions}).
+
+The \lua{string} library has an extra function:
+\luatex{string.explode(s[,m])}. This function returns an array containing
+the string argument \type{s} split into substrings based on the value
+of the string argument \type{m}. The second argument is a string that
+is either empty (this splits the string into characters), a single
+character (this splits on each occurrence of that character, possibly
+introducing empty strings), or a single character followed by the plus
+sign \type{+} (this special version does not create empty
+substrings). The default value for \type{m} is \quote{\type{ +}} (multiple
+spaces).
+
+Note: \type{m} is not hidden by surrounding braces (as it would be if
+this function was written in \TEX\ macros).
+
+The \lua{string} library also has six extra iterators that return strings
+piecemeal:
+
+\startitemize
+\item \luatex{string.utfvalues(s)} (returns an integer value in the
+\UNICODE\ range)
+\item \luatex{string.utfcharacters(s)} (returns a string with a single
+\UTF-8 token in it)
+\item \luatex{string.characters(s)} (a string containing one byte)
+\item \luatex{string.characterpairs(s)} (two strings each containing one byte) will
+produce an empty second string in the string length was odd.
+\item \luatex{string.bytes(s)} (a single byte value)
+\item \luatex{string.bytepairs(s)} (two byte values) Will produce nil instead of a
+number as its second return value if the string length was odd.
+\stopitemize
+
+The \luatex{string.characterpairs()} and \luatex{string.bytepairs()}
+are useful especially in the conversion of UTF-16 encoded data into UTF-8.
+
+
+Note: The \lua{string} library functions \luatex{find} etc. are not
+Unicode-aware. In cases where this is required (i.\,e.\ because the
+pattern used for searching contains characters above code point 127),
+the corresponding functions from \lua{unicode.utf8} should be used.
+
+\blank
+
+The \lua{os} library has a few extra functions and variables:
+
+\startitemize
+\item \luatex{os.exec(commandline)} is a variation on \lua{os.execute}.
+
+  The \type{commandline} can be either a single string or a single table. 
+
+  If the argument is a table: \LUATEX\ first checks if there is a value at
+  integer index zero. If there is, this is the command to be executed. Otherwise,
+  it will use the value at integer index one. (if neither are present, nothing 
+  at all happens).
+  
+  The set of consecutive values starting at integer 1 in the table are
+  the arguments that are passed on to the command (the value at index 1 
+  becomes \type{argv[0]}).  The command is searched for in the execution path, 
+  so there is normally no need to pass on a fully qualified pathname.
+
+  If the argument is a string, then it is automatically converted into 
+  a table by splitting on whitespace. In this case, it is impossible
+  for the command and first argument to differ from each other.
+
+  In the string argument format, whitespace can be protected by putting (part
+  of) an argument inside single or double quotes.  One layer of quotes is
+  interpreted by \LUATEX, and all occurences of \type{\"}, \type{\'} or
+  \type{\\} within the quoted text are un-escaped.  In the table format, there
+  is no string handling taking place.
+
+  This function normally does not return control back to the lua script: the
+  command will replace the current process. However, it will return \type{nil, 'error'}
+  if there was a problem while attempting to execute the command.
+
+  On windows, the current process is actually kept in memory until after the
+  execution of the command has finished. This prevents crashes in situations
+  where \TEXLUA\ scripts are run inside integrated \TEX\ environments.
+
+
+  (the original reason for this command is that it cleans out the current
+  process before starting the new one, making it especially useful for
+  use in \TEXLUA.)
+
+\item \luatex{os.spawn(commandline)} is a returning version of \lua{os.exec},
+  with otherwise identical calling conventions.
+ 
+  If the command ran ok, then the return value is the exit status of the
+  command. Otherwise, it will return \type{nil, 'error'}.
+
+\item \luatex{os.setenv('key','value')}
+  This sets a variable in the environment. Passing \lua{nil} instead of a
+  value string will remove the variable.
+
+\item \luatex{os.env}
+  This is a hash table containing a dump of the variables and values
+  in the process environment at the start of the run. It is writeable,
+  but the actual environment is {\it not\/} updated automatically.
+
+\item \luatex{os.gettimeofday()}
+Returns the current `unix time', but as a float. This function is
+not available on the SunOS platforms, so do not use this function
+for portable documents.
+
+\item \luatex{os.times()}
+Returns the current process times cf. the unix C library `times'
+call in seconds. This function is not available on the Windows and SunOS
+platforms, so do not use this function for portable documents.
+
+\item \luatex{os.tmpdir()} This will create a directory in the `current
+directory' with the name \type{luatex.XXXXXX} where the X-es are
+replaced by a unique string. The function also returns this string,
+so you can \type{lfs.chdir()} into it, or \type{nil} if it failed to
+create the directory.  The user is responsible for cleaning up at
+the end of the run, it does not happen automatically. 
+
+\item \luatex{os.type}
+This is a string  that gives a global indication of the class of operating
+system. The possible values are currently \type{windows}, \type{unix}, and
+\type{msdos} (you are unlikely to find this value `in the wild'). 
+
+\item \luatex{os.name}
+This is a string that gives a more precise indication of the operating
+system. These possible values are not yet fixed, and for \type{os.type} values
+\type{windows} and \type{msdos}, the \type{os.name} values are simply 
+\type{windows} and \type{msdos}
+
+The list for the type \type{unix} is more precise: \type{linux}, 
+\type{freebsd}, \type{openbsd}, \type{solaris}, \type{sunos} (pre-solaris), 
+\type{hpux}, \type{irix}, \type{macosx}, \type{bsd} (unknown, but BSD-like), 
+\type{sysv} (unknown, but SYSV-like), \type{generic} (unknown).
+
+(\type{os.version} is planned as a future extension)
+
+\stopitemize
+
+In stock Lua, many things depend on the current locale. In \LUATEX, we can't do
+that, because it makes documents unportable.  While \LUATEX\ is running if
+forces the following locale settings:
+\starttyping
+	LC_CTYPE=C
+	LC_COLLATE=C
+	LC_NUMERIC=C
+\stoptyping
+
+\section {\LUA\ modules}
+
+Some modules that are normally external to Lua are statically linked
+in with \LUATEX, because they offer useful functionality: 
+
+\startitemize
+\item \lua{slnunicode}, from the Selene libraries, \hyphenatedurl{http://luaforge.net/projects/sln}. (version 1.1)
+
+This library has been slightly extended so that the \type{unicode.utf8.*} 
+functions also accept the first 256 values of Plane~18. This is the range \LUATEX\ 
+uses for raw binary output, as explained above,
+
+\item \lua{luazip}, from the kepler project, \hyphenatedurl{http://www.keplerproject.org/luazip/}.  
+  (version 1.2.1, but patched for compilation with lua 5.1)
+\item \lua{luafilesystem}, also from the kepler project, \hyphenatedurl{http://www.keplerproject.org/luafilesystem/}.  
+  (version 1.2, but patched for compilation with lua 5.1)
+\item \lua{lpeg}, by Roberto Ierusalimschy, \hyphenatedurl{http://www.inf.puc-rio.br/~roberto/lpeg.html}. (version 0.8.1)
+
+Note: \lua{lpeg} is not Unicode-aware, but interprets strings on a
+byte-per-byte basis. This mainly means that \luatex{lpeg.S} cannot be
+used with characters above code point 127, since those characters are
+encoded using two bytes, and thus \luatex{lpeg.S} will look for one
+of those two bytes when matching, not the combination of the two.
+
+The same is true for \luatex{lpeg.R}, although the latter will display
+an error message if used with characters above code point 127: I.\,e.\
+\luatex{lpeg.R('aä')} results in the message \type{bad argument #1 to
+'R' (range must have two characters)}, since to \lua{lpeg}, \type{ä}
+is two 'characters' (bytes), so \type{aä} totals three.
+
+\item \lua{lzlib}, by Tiago Dionizio, \hyphenatedurl{http://mega.ist.utl.pt/~tngd/lua/}. (version 0.2)
+\item \lua{md5}, by Roberto Ierusalimschy \hyphenatedurl{http://www.inf.puc-rio.br/~roberto/md5/md5-5/md5.html}.
+\stopitemize
+
+\chapter[libraries]{\LUATEX\ \LUA\ Libraries}
+
+The interfacing between \TEX\ and \LUA\ is facilitated by a set of
+library modules. The \LUA\ libraries in this chapter are all defined and 
+initialized by the \LUATEX\ executable. Together, they allow \LUA\
+scripts to query and change a number of \TEX's internal variables, run
+various internal functions \TEX, and set up \LUATEX's hooks to execute
+\LUA\ code.
+
+\section{The \luatex{tex} library}
+
+The \luatex{tex} table contains a large list of virtual internal \TEX\
+parameters that are partially writable.
+
+The designation \quote{virtual} means that these items are not properly
+defined in \LUA, but are only front\-ends that are handled by a metatable
+that operates on the actual \TEX\ values. As a result, most of the \LUA\
+table operators (like \type{pairs} and \type{#}) do not work on such
+items.
+
+At the moment, it is possible to access almost every parameter
+that has these characteristics:
+
+\startitemize[packed]
+\item You can use it after \tex{the}
+\item It is a single token.
+\stopitemize
+
+This excludes parameters that need extra arguments, like
+\tex{the}\tex{scriptfont}.
+
+The subset comprising simple integer and dimension registers are
+writable as well as readable (stuff like \tex{tracingcommands} and
+\tex{parindent}).
+
+\subsection{Integer parameters}
+
+The integer parameters accept and return \LUA\ numbers.
+
+Read-write:
+
+\startcolumns[n=2]
+\starttyping
+tex.adjdemerits
+tex.binoppenalty
+tex.brokenpenalty
+tex.catcodetable
+tex.clubpenalty
+tex.day
+tex.defaulthyphenchar
+tex.defaultskewchar
+tex.delimiterfactor
+tex.displaywidowpenalty
+tex.doublehyphendemerits
+tex.endlinechar
+tex.errorcontextlines
+tex.escapechar
+tex.exhyphenpenalty
+tex.fam
+tex.finalhyphendemerits
+tex.floatingpenalty
+tex.globaldefs
+tex.hangafter
+tex.hbadness
+tex.holdinginserts
+tex.hyphenpenalty
+tex.interlinepenalty
+tex.language
+tex.lastlinefit
+tex.lefthyphenmin
+tex.linepenalty
+tex.localbrokenpenalty
+tex.localinterlinepenalty
+tex.looseness
+tex.mag
+tex.maxdeadcycles
+tex.month
+tex.newlinechar
+tex.outputpenalty
+tex.pausing
+tex.pdfadjustinterwordglue
+tex.pdfadjustspacing
+tex.pdfappendkern
+tex.pdfcompresslevel
+tex.pdfdecimaldigits
+tex.pdfgamma
+tex.pdfgentounicode
+tex.pdfimageapplygamma
+tex.pdfimagegamma
+tex.pdfimagehicolor
+tex.pdfimageresolution
+tex.pdfinclusionerrorlevel
+tex.pdfminorversion
+tex.pdfobjcompresslevel
+tex.pdfoutput
+tex.pdfpagebox
+tex.pdfpkresolution
+tex.pdfprependkern
+tex.pdfprotrudechars
+tex.pdftracingfonts
+tex.pdfuniqueresname
+tex.postdisplaypenalty
+tex.predisplaydirection
+tex.predisplaypenalty
+tex.pretolerance
+tex.relpenalty
+tex.righthyphenmin
+tex.savinghyphcodes
+tex.savingvdiscards
+tex.showboxbreadth
+tex.showboxdepth
+tex.time
+tex.tolerance
+tex.tracingassigns
+tex.tracingcommands
+tex.tracinggroups
+tex.tracingifs
+tex.tracinglostchars
+tex.tracingmacros
+tex.tracingnesting
+tex.tracingonline
+tex.tracingoutput
+tex.tracingpages
+tex.tracingparagraphs
+tex.tracingrestores
+tex.tracingscantokens
+tex.tracingstats
+tex.uchyph
+tex.vbadness
+tex.widowpenalty
+tex.year
+\stoptyping
+\stopcolumns
+
+Read|-|only:
+
+\startcolumns[n=3]
+\starttyping
+tex.deadcycles
+tex.insertpenalties
+tex.parshape
+tex.prevgraf
+tex.spacefactor
+\stoptyping
+\stopcolumns
+
+\subsection{Dimension parameters}
+
+The dimension parameters accept \LUA\ numbers (signifying scaled points)
+or strings (with included dimension). The result is always a string.
+
+Read-write:
+
+\startcolumns[n=3]
+\starttyping
+tex.boxmaxdepth
+tex.delimitershortfall
+tex.displayindent
+tex.displaywidth
+tex.emergencystretch
+tex.hangindent
+tex.hfuzz
+tex.hoffset
+tex.hsize
+tex.lineskiplimit
+tex.mathsurround
+tex.maxdepth
+tex.nulldelimiterspace
+tex.overfullrule
+tex.pagebottomoffset
+tex.pageheight
+tex.pagerightoffset
+tex.pagewidth
+tex.parindent
+tex.pdfdestmargin
+tex.pdfeachlinedepth
+tex.pdfeachlineheight
+tex.pdffirstlineheight
+tex.pdfhorigin
+tex.pdflastlinedepth
+tex.pdflinkmargin
+tex.pdfpageheight
+tex.pdfpagewidth
+tex.pdfpxdimen
+tex.pdfthreadmargin
+tex.pdfvorigin
+tex.predisplaysize
+tex.scriptspace
+tex.splitmaxdepth
+tex.vfuzz
+tex.voffset
+tex.vsize
+\stoptyping
+\stopcolumns
+
+Read|-|only:
+
+\startcolumns[n=3]
+\starttyping
+tex.pagedepth
+tex.pagefilllstretch
+tex.pagefillstretch
+tex.pagefilstretch
+tex.pagegoal
+tex.pageshrink
+tex.pagestretch
+tex.pagetotal
+tex.prevdepth
+\stoptyping
+\stopcolumns
+
+\subsection{Direction parameters}
+
+The direction parameters are read|-|only and return a \LUA\ string.
+
+\startcolumns[n=3]
+\starttyping
+tex.bodydir
+tex.mathdir
+tex.pagedir
+tex.pardir
+tex.textdir
+\stoptyping
+\stopcolumns
+
+\subsection{Glue parameters}
+
+All glue parameters are read|-|only and return a \LUA\ string.
+
+\startcolumns[n=3]
+\starttyping
+tex.abovedisplayshortskip
+tex.abovedisplayskip
+tex.baselineskip
+tex.belowdisplayshortskip
+tex.belowdisplayskip
+tex.leftskip
+tex.lineskip
+tex.parfillskip
+tex.parskip
+tex.rightskip
+tex.spaceskip
+tex.splittopskip
+tex.tabskip
+tex.topskip
+tex.xspaceskip
+\stoptyping
+\stopcolumns
+
+\subsection{Muglue parameters}
+
+All muglue parameters are read|-|only and return a \LUA\ string.
+
+\startcolumns[n=3]
+\starttyping
+tex.medmuskip
+tex.thickmuskip
+tex.thinmuskip
+\stoptyping
+\stopcolumns
+
+\subsection{Tokenlist parameters}
+
+All tokenlist parameters are read|-|only and return a \LUA\ string.
+
+\startcolumns[n=3]
+\starttyping
+tex.errhelp
+tex.everycr
+tex.everydisplay
+tex.everyeof
+tex.everyhbox
+tex.everyjob
+tex.everymath
+tex.everypar
+tex.everyvbox
+tex.output
+tex.pdfpageattr
+tex.pdfpageresources
+tex.pdfpagesattr
+tex.pdfpkmode
+\stoptyping
+\stopcolumns
+
+\subsection{Convert commands}
+
+The supported commands at this moment are:
+
+\startcolumns[n=3]
+\starttyping
+tex.AlephVersion
+tex.Alephrevision
+tex.OmegaVersion
+tex.Omegarevision
+tex.eTeXVersion
+tex.eTeXrevision
+tex.formatname
+tex.jobname
+tex.luatexrevision
+tex.luatexdatestamp
+tex.pdfnormaldeviate
+tex.pdftexbanner
+tex.pdftexrevision
+\stoptyping
+\stopcolumns
+
+All \quote{convert} commands are read|-|only and return a \LUA\ string.
+
+If you are wondering why this list looks haphazard; these are all the
+cases of the \quote{convert} internal command that do not require an
+argument.
+
+\subsection{Attribute, count, dimension and token registers}
+
+\TEX's attributes (\tex{attribute}), counters (\tex{count}),
+dimensions (\tex{dimen}) and token (\tex{toks}) registers can be
+accessed and written to using four virtual sub|-|tables of the
+\luatex{tex} table:
+
+\startcolumns[n=3]
+\starttyping
+tex.attribute
+tex.count
+tex.dimen
+tex.toks
+\stoptyping
+\stopcolumns
+
+It is possible to use the names of relevant \tex{attributedef}, \tex{countdef},
+\tex{dimendef}, or \tex{toksdef} control sequences as indices
+to these tables:
+
+\starttyping
+tex.count.scratchcounter = 0
+enormous = tex.dimen['maxdimen']
+\stoptyping
+
+In this case, \LUATEX\ looks up the value for you on the fly. You have
+to use a valid \tex{countdef} (or \tex{attributedef}, or
+\tex{dimendef}, or \tex{toksdef}), anything else will generate an error
+(the intent is to eventually also allow \type{<chardef tokens>} and even
+macros that expand into a number).
+
+The attribute and count registers accept and return \LUA\ numbers.
+
+The dimension registers accept \LUA\ numbers (in scaled points) or
+strings (with an included absolute dimension; \type {em} and \type {ex} and \type {px}
+are forbidden). The result is always a number in scaled points.
+
+The token registers accept and return \LUA\ strings. \LUA\ strings are
+converted to and from token lists using \tex{the}\tex{toks} style
+expansion: all category codes are either space (10) or other (12).
+
+As an alternative to array addressing, there are also accessor
+functions defined:
+
+\startfunctioncall
+tex.setdimen(number n, string s)
+tex.setdimen(string s, string s)
+tex.setdimen(number n, number n)
+tex.setdimen(string s, number n)
+number n = tex.getdimen(number n)
+number n = tex.getdimen(string s)
+
+tex.setcount(number n, number n)
+tex.setcount(string s, number n)
+number n = tex.getcount(number n)
+number n = tex.getcount(string s)
+
+tex.settoks (number n, string s)
+tex.settoks (string s, string s)
+string s = tex.gettoks (number n)
+string s = tex.gettoks (string s)
+\stopfunctioncall
+
+\subsection{Box registers}
+
+The current dimensions of \tex{box} registers can be read and
+altered using three other virtual sub|-|tables :
+
+\starttyping
+tex.wd
+tex.ht
+tex.dp
+\stoptyping
+
+These are indexed strictly by number.
+
+The box size registers accept \LUA\ numbers (in scaled points)
+or strings (with included dimension). The result is always a number
+in scaled points.
+
+As an alternative to array addressing, there are also accessor
+functions defined:
+
+\startfunctioncall
+tex.setboxwd(number n, number n)
+number n = tex.getboxwd(number n)
+
+tex.setboxht(number n, number n)
+number n = tex.getboxht(number n)
+
+tex.setboxdp(number n, number n)
+number n = tex.getboxdp(number n)
+\stopfunctioncall
+
+It is also possible to set and query actual boxes, using the node
+interface as defined in the \luatex{node} library:
+
+\starttyping
+tex.box
+\stoptyping
+
+for array access, or
+
+\starttyping
+tex.setbox(number n, <node> s)
+<node> n = tex.getbox(number n)
+\stoptyping
+
+for function|-|based access.
+
+Be warned that an assignment like
+
+\starttyping
+tex.box[0] = tex.box[2]
+\stoptyping
+
+does not copy the node list, it just duplicates a node pointer.  If
+\tex{box2} will be cleared by \TEX\ commands later on, the contents
+of \tex{box0} becomes invalid as well. To prevent this from
+happening, always use \luatex{node.copy_list()} unless you are
+assigning to a temporary variable:
+
+\starttyping
+tex.box[0] = node.copy_list(tex.box[2])
+\stoptyping
+
+\subsection{Print functions}
+
+The \luatex{tex} table also contains the three print functions that
+are the major interface from \LUA\ scripting to \TEX.
+
+The arguments to these three functions are all stored in an in|-|memory
+virtual file that is fed to the \TEX\ scanner as the result of the
+expansion of \tex{directlua}.
+
+The total amount of returnable text from a \tex{directlua} command
+is only limited by available system \RAM. However, each separate
+printed string has to fit completely in \TEX's input buffer.
+
+\subsubsection{\luatex{tex.print}}
+
+\startfunctioncall
+tex.print(string s, ...)
+tex.print(number n, string s, ...)
+\stopfunctioncall
+
+Each string argument is treated by \TEX\ as a separate input line.
+
+The optional parameter can be used to print the strings using the
+catcode regime defined by \tex{catcodetable}~\type{n}. If \type{n} is not
+a valid catcode table, then it is ignored, and the currently
+active catcode regime is used instead.
+
+The very last string of the very last \luatex{tex.print()} command in a
+\tex{directlua} will not have the \tex{endlinechar} appended, all
+others do.
+
+\subsubsection{\luatex{tex.sprint}}
+
+\startfunctioncall
+tex.sprint(string s, ...)
+tex.sprint(number n, string s, ...)
+\stopfunctioncall
+
+Each string argument is treated by \TEX\ as a special kind of input line
+that makes it suitable for use as a partial line input mechanism:
+
+\startitemize[packed]
+\item \TEX\ does not switch to the \quote{new line} state, so
+   that leading spaces are not ignored.
+\item No \tex{endlinechar} is inserted.
+\item Trailing spaces are not removed.
+
+(Note that this does not prevent \TEX\ itself from eating spaces as
+result of interpreting the line. For example, in 
+\starttyping
+before\directlua0{tex.sprint("\\relax")tex.sprint(" inbetween")}after
+\stoptyping
+the space before \type{inbetween} will be gobbled as a result of 
+the \quote{normal} scanning of \type{\relax}).
+\stopitemize
+
+
+\subsubsection{\luatex{tex.write}}
+
+\startfunctioncall
+tex.write(string s, ...)
+\stopfunctioncall
+
+Each string argument is treated by \TEX\ as a special kind of input
+line that makes is suitable for use as a quick way to dump
+information:
+
+\startitemize
+\item All catcodes on that line are either \quote{space} (for '~') or
+     \quote{character} (for all others).
+\item There is no \tex{endlinechar} appended.
+\stopitemize
+
+\subsection{Helper functions}
+
+\subsubsection{\luatex{tex.round}}
+
+\startfunctioncall
+number n =  tex.round(number o)
+\stopfunctioncall
+
+Rounds lua number \type{o}, and returns a number that is in the range
+of a valid \TEX\ register value. If the number starts out of range, it
+generates a \quote{Number to big} error as well.
+
+\subsubsection{\luatex{tex.scale}}
+
+\startfunctioncall
+number n =  tex.scale(number o, number delta)
+table n  =  tex.scale(table o, number delta)
+\stopfunctioncall
+
+Multiplies the lua numbers \type{o} and \type{delta}, and returns a
+rounded number that is in the range of a valid \TEX\ register value.
+In the table version, it creates a copy of the table with all numeric
+top||level values scaled in that manner. If the multiplied number(s) are
+of range, it generates \quote{Number to big} error(s) as well.
+
+\section{The \luatex{token} library}
+
+The \luatex{token} table contains interface functions to \TEX's
+handling of tokens. These functions are most useful when combined with
+the \luatex{token_filter} callback, but they could be used standalone as
+well.
+
+A token is represented in \LUA\ as a small table. For the moment, this
+table consists of three numeric entries:
+
+\starttabulate[|l|l|p|]
+\NC \bf no.\NC \bf meaning         \NC \bf description \NC \NR
+\NC 1      \NC command code        \NC this is a value between~$0$ and~$130$ (approximately)\NC \NR
+\NC 2      \NC command modifier    \NC this is a value between~$0$ and~$2^{21}$ \NC \NR
+\NC 3      \NC control sequence id \NC for commands that are not the result of control
+                                       sequences, like letters and characters, it is zero,
+                                       otherwise, it is a number pointing into the \quote
+                                       {equivalence table} \NC \NR
+\stoptabulate
+
+\subsection{\luatex{token.get_next}}
+
+\startfunctioncall
+token t = token.get_next()
+\stopfunctioncall
+
+This fetches the next input token from the current input source,
+without expansion.
+
+\subsection{\luatex{token.is_expandable}}
+
+\startfunctioncall
+boolean b = token.is_expandable(token t)
+\stopfunctioncall
+
+This tests if the token \type{t} could be expanded.
+
+\subsection{\luatex{token.expand}}
+
+\startfunctioncall
+token.expand()
+\stopfunctioncall
+
+If a token is expandable, this will expand one level of it, so that
+the first token of the expansion will now be the next token to be read
+by \luatex{tex.get_next()}.
+
+\subsection{\luatex{token.is_activechar}}
+
+\startfunctioncall
+boolean b = token.is_activechar(token t)
+\stopfunctioncall
+
+This is a special test that is sometimes handy. Discovering whether
+some token is the result of an active character turned out to be very
+hard otherwise.
+
+\subsection{\luatex{token.create}}
+
+\startfunctioncall
+token t = token.create(string csname)
+token t = token.create(number charcode)
+token t = token.create(number charcode, number catcode)
+\stopfunctioncall
+
+This is the token factory. If you feed it a string, then it is the
+name of a control sequence (without leading backslash), and it will be
+looked up in the equivalence table.
+
+If you feed it number, then this is assumed to be an input character,
+and an optional second number gives its category code.  This means it
+is possible to overrule a character's category code, with a few
+exceptions: the category codes~0 (escape), 9~(ignored), 13~(active),
+14~(comment), and 15 (invalid) cannot occur inside a token. The values~0, 9, 14
+and~15 are therefore illegal as input to \luatex{token.create()}, and
+active characters will be resolved immediately.
+
+Note: unknown string sequences and never defined active characters
+will result in a token representing an \quote{undefined control sequence}
+with a near|-|random name. It is {\it not\/} possible to define brand
+new control sequences using \luatex{token.create}!
+
+\subsection{\luatex{token.command_name}}
+
+\startfunctioncall
+string commandname = token.command_name(token t)
+\stopfunctioncall
+
+This returns the name associated with the \quote{command} value of the token
+in \LUATEX. There is not always a direct connection between these names and
+primitives. For instance, all \tex{ifxxx} tests are grouped under
+\type {if_fest}, and the \quote{command modifier} defines which test is to be run.
+
+\subsection{\luatex{token.command_id}}
+
+\startfunctioncall
+number i = token.command_idtring commandname)
+\stopfunctioncall
+
+This returns a number that is the inverse operation of the previous
+command, to be used as the first item in a token table.
+
+\subsection{\luatex{token.csname_name}}
+
+\startfunctioncall
+string csname = token.csname_name(token t)
+\stopfunctioncall
+
+This returns the name associated with the \quote{equivalence table} value of
+the token in \LUATEX. It returns the string value of the command used
+to create the current token, or an empty string if there is no
+associated control sequence.
+
+\subsection{\luatex{token.csname_id}}
+
+\startfunctioncall
+number i = token.csname_id(string csname)
+\stopfunctioncall
+
+This returns a number that is the inverse operation of the previous
+command, to be used as the third item in a token table.
+
+\section{The \luatex{node} library}
+
+The \luatex{node} library contains functions that facilitate dealing
+with (lists of) nodes and their values. They allow you to create, alter,
+copy, delete, and insert \LUATEX\ node objects, the core
+objects within the typesetter.
+
+\LUATEX\ nodes are represented in \LUA\ as userdata with
+the metadata type \luatex{luatex.node}. The various parts within
+a node can be accessed using named fields.
+
+Each node has at least the three fields \type{next}, \type{id}, and
+\type{subtype}:
+
+\startitemize[intro]
+
+\item The \type{next} field returns the userdata
+object for the next node in a linked list of nodes, or
+nil, if there is no next node.
+
+\item The \type{id} indicates \TEX's \quote{node type}. The field \type{id}
+has a numeric value for efficiency reasons, but some of the library
+functions also accept a string value instead of \type{id}.
+
+\item The \type{subtype} is another number. It often gives further information
+about a node of a particular \type{id}, but it is most important when dealing
+with \quote{whatsits}, because they are differentiated solely based on their
+\type{subtype}.
+\stopitemize
+
+The other available fields depend on the \type{id} (and for \quote{whatsits}, the
+\type{subtype}) of the node. Further details on the various fields and their
+meanings are given in~\in{chapter}[nodes].
+
+\TEX's math nodes are not yet supported: there is not yet an interface
+to the internals of the math list and it is not possible to create
+them from \LUA. Support for \type{unset} (alignment) nodes is partial:
+they can be queried and modified from \LUA\ code, but not created.
+
+Nodes can be compared to each other, but: you are actually comparing
+indices into the node memory. This means that equality tests can only
+be trusted under very limited conditions. It will not work correctly
+in any situation where one of the two nodes has been freed and|/|or
+reallocated: in that case, there will be false positives.
+
+At the moment, memory management of nodes should still be done
+explicitly by the user.  Nodes are not \quote{seen} by the \LUA\
+garbage collector, so you have to call the node free-ing functions
+yourself when you are no longer in need of a node (list). Nodes form
+linked lists without reference counting, so you have to be careful
+that when control returns back to \LUATEX\ itself, you have not
+deleted nodes that are still referenced from a \type{next} pointer
+elsewhere, and that you did not create nodes that are referenced more
+than once.
+
+\subsection{Node handling functions}
+
+\subsubsection{\luatex{node.types}}
+
+\startfunctioncall
+table t = node.types()
+\stopfunctioncall
+
+This function returns an array that maps node id numbers to node type
+strings, providing an overview of the possible top|-|level \type{id}
+types.
+
+\subsubsection{\luatex{node.whatsits}}
+
+\startfunctioncall
+table t = node.whatsits()
+\stopfunctioncall
+
+\TEX's \quote{whatsits} all have the same \type{id}. The various subtypes
+are defined by their \type{subtype}. The function is much like
+\luatex{node.types}, except that it provides an array of \type{subtype}
+mappings.
+
+\subsubsection{\luatex{node.id}}
+
+\startfunctioncall
+number id = node.id(string type)
+\stopfunctioncall
+
+This converts a single type name to its internal numeric
+representation.
+
+\subsubsection{\luatex{node.subtype}}
+
+\startfunctioncall
+number subtype = node.subtype(string type)
+\stopfunctioncall
+
+This converts a single whatsit name to its internal numeric
+representation (\type{subtype}).
+
+\subsubsection{\luatex{node.type}}
+
+\startfunctioncall
+string type = node.type(number id)
+\stopfunctioncall
+
+This converts a internal numeric representation to an external string
+representation.
+
+\subsubsection{\luatex{node.fields}}
+
+\startfunctioncall
+table t = node.fields(number id)
+table t = node.fields(number id, number subtype)
+\stopfunctioncall
+
+This function returns an array of valid field names for a particular
+type of node. If you want to get the valid fields for a
+\quote{whatsit}, you have to supply the second argument also. In other
+cases, any given second argument will be silently ignored.
+
+This function accepts string \type{id} and \type{subtype} values as
+well.
+
+\subsubsection{\luatex{node.has_field}}
+
+\startfunctioncall
+boolean t = node.has_field(<node> n, string field)
+\stopfunctioncall
+
+This function returns a boolean that is only true if \type{n} is
+actually a node, and it has the field. 
+
+
+\subsubsection{\luatex{node.new}}
+
+\startfunctioncall
+<node> n = node.new(number id)
+<node> n = node.new(number id, number subtype)
+\stopfunctioncall
+
+Creates a new node. All of the new node's fields are initialized to
+either zero or nil except for \type{id} and \type{subtype} (if
+supplied). If you want to create a new whatsit, then the second
+argument is required, otherwise it need not be present. As with all
+node functions, this function creates a node on the \TEX\ level.
+
+This function accepts string \type{id} and \type{subtype} values as
+well.
+
+\subsubsection{\luatex{node.free}}
+
+\startfunctioncall
+node.free(<node> n)
+\stopfunctioncall
+
+Removes the node \type{n} from \TEX's memory. Be careful: no checks
+are done on whether this node is still pointed to from a register or some
+\type{next} field: it is up to you to make sure that the internal data
+structures remain correct.
+
+\subsubsection{\luatex{node.flush_list}}
+
+\startfunctioncall
+node.flush_list(<node> n)
+\stopfunctioncall
+
+Removes the node list \type{n} and the complete node list following
+\type{n} from \TEX's memory. Be careful: no checks are done on whether
+any of these nodes is still pointed to from a register or some
+\type{next} field: it is up to you to make sure that the internal data
+structures remain correct.
+
+\subsubsection{\luatex{node.copy}}
+
+\startfunctioncall
+<node> m = node.copy(<node> n)
+\stopfunctioncall
+
+Creates a deep copy of node \type{n}, including all nested lists as in
+the case of a hlist or vlist node. Only the \type{next} field is not
+copied.
+
+\subsubsection{\luatex{node.copy_list}}
+
+\startfunctioncall
+<node> m = node.copy_list(<node> n)
+\stopfunctioncall
+
+Creates a deep copy of the node list that starts at \type{n}.
+
+\subsubsection{\luatex{node.hpack}}
+
+\startfunctioncall
+<node> h = node.hpack(<node> n)
+<node> h = node.hpack(<node> n, number w, string info)
+\stopfunctioncall
+
+This function creates a new hlist by packaging the list that begins at  node
+\type{n} into a horizontal box. With only a single argument, this box 
+is created using the natural width of its components. In the three
+argument form, \type{info} must be either \type{additional} or
+\type{exactly}, and \type{w} is the additional (\type{\hbox spread})
+or exact (\type{\hbox to}) width to be used.
+
+Caveat: at this moment, there can be unexpected side|-|effects to this
+function, like updating some of the \type{\marks} and \type{\inserts}.
+
+\subsubsection{\luatex{node.slide}}
+
+\startfunctioncall
+<node> m = node.slide(<node> n)
+\stopfunctioncall
+
+Returns the last node of the node list that starts at \type{n}. As a
+side|-|effect, it also creates a reverse chain of \type{prev} pointers
+between nodes.
+
+\subsubsection{\luatex{node.length}}
+
+\startfunctioncall
+number i = node.length(<node> n)
+number i = node.length(<node> n, <node> m)
+\stopfunctioncall
+
+Returns the number of nodes contained in the node list that starts at
+\type{n}. If \type{m} is also supplied it stops at \type{m} instead of
+at the end of the list. The node \type{m} is not counted.
+
+\subsubsection{\luatex{node.count}}
+
+\startfunctioncall
+number i = node.count(number id, <node> n)
+number i = node.count(number id, <node> n, <node> m)
+\stopfunctioncall
+
+Returns the number of nodes contained in the node list that starts at
+\type{n} that have an matching \type{id} field.
+If \type{m} is also supplied, counting stops at \type{m} instead of at
+the end of the list. The node \type{m} is not counted.
+
+This function also accept string \type{id}'s.
+
+\subsubsection{\luatex{node.traverse}}
+
+\startfunctioncall
+<node> t = node.traverse(<node> n)
+\stopfunctioncall
+
+This is an iterator that loops over the node list that starts at \type{n}.
+
+\subsubsection{\luatex{node.traverse_id}}
+
+\startfunctioncall
+<node> t = node.traverse_id(number id, <node> n)
+\stopfunctioncall
+
+This is an iterator that loops over all the nodes in the list that
+starts at \type{n} that have a matching \type{id} field. 
+
+\subsubsection{\luatex{node.remove}}
+
+\startfunctioncall
+<node> head, current = node.remove(<node> head, <node> current)
+\stopfunctioncall
+
+This function removes the node \type{current} from the list following
+\type{head}. It is your responsibility to make sure it is really part
+of that list. The return values are the new \type{head} and
+\type{current} nodes. The returned \type{current} is the 
+node in the calling argument, and is only passed back as a convenience
+(its \type{next} field will be cleared). The returned \type{head} is
+more important, because if the function is called with \type{current}
+equal to \type{head}, it will be changed.
+
+
+\subsubsection{\luatex{node.insert_before}}
+
+\startfunctioncall
+<node> head, new = node.insert_before(<node> head, <node> current, <node> new)
+\stopfunctioncall
+
+This function inserts the node \type{new} before \type{current} into
+the list following \type{head}. It is your responsibility to make sure
+that \type{current} is really part of that list. The return values are
+the (potentially mutated) \type{head} and the \type{new}, set up to
+be part of the list (with correct \type{next} field). If \type{head}
+is initially \type{nil}, it will become \type{new}.
+
+
+\subsubsection{\luatex{node.insert_after}}
+
+\startfunctioncall
+<node> head, new = node.insert_after(<node> head, <node> current, <node> new)
+\stopfunctioncall
+
+This function inserts the node \type{new} after \type{current} into
+the list following \type{head}. It is your responsibility to make sure
+that \type{current} is really part of that list. The return values are
+the \type{head} and the \type{new}, set up to be part of the list
+(with correct \type{next} field). If \type{head} is initially
+\type{nil}, it will become \type{new}.
+
+\subsubsection{\luatex{node.first_character}}
+
+\startfunctioncall
+<node> n = node.first_character(<node> n)
+<node> n = node.first_character(<node> n, <node> m)
+\stopfunctioncall
+
+Returns the first node that is a glyph node with a subtype indicating
+it is a character, or \type{nil}. 
+
+\subsubsection{\luatex{node.ligaturing}}
+
+\startfunctioncall
+<node> h, <node> t, <boolean> success = node.ligaturing(<node> n)
+<node> h, <node> t, <boolean> success = node.ligaturing(<node> n, <node> m)
+\stopfunctioncall
+
+Apply \TEX-style ligaturing to the specified nodelist. The tail node
+\type{m} is optional. The two returned nodes \type{h} and \type{t} are
+the new head and tail (both \type{n} and \type{m} can change into 
+a new ligature).
+
+\subsubsection{\luatex{node.kerning}}
+
+\startfunctioncall
+<node> h, <node> t, <boolean> success = node.kerning(<node> n)
+<node> h, <node> t, <boolean> success = node.kerning(<node> n, <node> m)
+\stopfunctioncall
+
+Apply \TEX-style kerning to the specified nodelist. The tail node
+\type{m} is optional. The two returned nodes \type{h} and \type{t} are
+the head and tail (either one of these can be an inserted kern node,
+because special kernings with word boundaries are possible).
+
+
+
+
+\subsubsection{\luatex{node.unprotect_glyphs}}
+
+\startfunctioncall
+node.unprotect_glyphs(<node> n)
+\stopfunctioncall
+
+Substracts 256 from all glyph node subtypes. This and the next
+function are helpers to convert from \type{characters} to
+\type{glyphs} during node processing.
+
+
+\subsubsection{\luatex{node.protect_glyphs}}
+
+\startfunctioncall
+node.protect_glyphs(<node> n)
+\stopfunctioncall
+
+Adds 256 to all glyph node subtypes in the node list starting at
+\type{n}, except that if the value is 1, it adds only 255. The special
+handling of 1 means that \type{characters} will become \type{glyphs}
+after substraction of 256.
+
+\subsubsection{\luatex{node.last_node}}
+
+\startfunctioncall
+<node> n = node.last_node()
+\stopfunctioncall
+
+This function pops the last node from \TEX's `current list'. 
+It returns that node, or \type{nil} if the current list is empty.
+
+\subsubsection{\luatex{node.write}}
+
+\startfunctioncall
+node.write(<node> n)
+\stopfunctioncall
+
+This is an experimental function that will append a node list to 
+\TEX's `current list'. There is no error checking yet!
+
+
+
+\subsection{Attribute handling}
+
+Attributes appear as linked list of userdata objects in the
+\type{attr} field of individual nodes. They can be handled
+individually, but it is much safer and more efficient to use the
+dedicated functions associated with them.
+
+\subsubsection{\luatex{node.has_attribute}}
+
+\startfunctioncall
+number v = node.has_attribute(<node> n, number id)
+number v = node.has_attribute(<node> n, number id, number val)
+\stopfunctioncall
+
+Tests if a node has the attribute with number \type{id} set. If
+\type{val} is also supplied, also tests if the value matches \type{val}.
+It returns the value, or, if no match is found, nil.
+
+\subsubsection{\luatex{node.set_attribute}}
+
+\startfunctioncall
+node.set_attribute(<node> n, number id, number val)
+\stopfunctioncall
+
+Sets the attribute with number \type{id} to the value
+\type{val}. Duplicate assignments are ignored.
+
+\subsubsection{\luatex{node.unset_attribute}}
+
+\startfunctioncall
+number v = node.unset_attribute(<node> n, number id, number val)
+number v = node.unset_attribute(<node> n, number id)
+\stopfunctioncall
+
+Unsets the attribute with number \type{id}. If \type{val} is also supplied,
+it will only perform this operation if the value matches \type{val}.
+Missing attributes or attribute|-|value pairs are ignored.
+
+If the attribute was actually deleted, returns its old
+value. Otherwise, returns nil.
+
+\section{The \luatex{texio} library}
+
+This library takes care of the low|-|level I/O interface.
+
+\subsection{Printing functions}
+
+\subsubsection{\luatex{texio.write}}
+
+\startfunctioncall
+texio.write(string target, string s, ...)
+texio.write(string s, ...)
+\stopfunctioncall
+
+Without the \type{target} argument, writes all given strings to the same
+location(s) \TEX\ writes messages to at this moment. If
+\tex{batchmode} is in effect, it writes only to the log,
+otherwise  it writes to the log and the terminal.
+
+The optional \type{target} can be one of three possibilities:
+\type{term}, \type{log} or \type {term and log}.
+
+Note: If several strings are given, and if the first of these strings
+is or might be one of the targets above, the \type{target} must be
+specified explicitely to prevent \LUA\ from interpreting the first
+string as the target.
+
+\subsubsection{\luatex{texio.write_nl}}
+
+\startfunctioncall
+texio.write_nl(string target, string s, ...)
+texio.write_nl(string s, ...)
+\stopfunctioncall
+
+Like \luatex{texio.write}, but make sure that the given strings will
+appear at the beginning of a new line. You can pass a single empty string
+if you only want to move to the next line.
+
+\section{The \luatex{pdf} library}
+
+This table contains the current \type{h} and \type{v} values that
+define the location on the output page. The values can be queried
+and set using scaled points as units.
+
+\starttyping
+pdf.v
+pdf.h
+\stoptyping
+
+The associated function calls are
+
+\startfunctioncall
+pdf.setv(number n)
+number n = pdf.getv()
+pdf.seth(number n)
+number n = pdf.geth()
+\stopfunctioncall
+
+
+It also holds a print function to write stuff to the \PDF\ document
+that can be used from within a \tex{latelua} argument. This function
+is not to be used inside \tex{directlua} unless you know {\it
+exactly} what you are doing.
+
+\subsubsubject{\luatex{pdf.print}}
+
+\startfunctioncall
+pdf.print(string s)
+pdf.print(string type, string s)
+\stopfunctioncall
+
+The optional parameter can be used to mimic the behavior of
+\tex{pdfliteral}: the \type{type} is \type{direct} or \type{page}.
+
+\section{The \luatex{img} library}
+
+The \type{img} library can be used as an alternative to
+\tex{pdfximage} and \tex{pdfrefximage}, and the associated `satellite'
+commands like \tex{pdfximagebbox}.
+
+\subsubsubject{\luatex{img.new}}
+
+\startfunctioncall
+<image> var = img.new()
+<image> var = img.new(image_spec) 
+\stopfunctioncall
+
+This function creates a userdata object of type `image'. The 
+\type{image_spec} argument is optional. If it is given, it must be
+a table, and that table must contain a \type{filename} key.  A number of
+other keys can also be useful, these are explained below.
+
+You can either say
+\starttyping
+a=img.new()
+\stoptyping 
+followed by 
+\starttyping
+a.filename="foo.png"
+\stoptyping 
+or you can put the file name (and some or all of the other keys)
+into a table directly, like so:
+\starttyping
+a=img.new{filename='foo.pdf',page=1}
+\stoptyping
+
+The generated \type{<image>} userdata object allows access to a set of
+user-specified values as well as a set of values that are normally
+filled in and updated automatically by \LUATEX\ itself. Some of those
+are derived from the actual image file, others are updated to reflect 
+the PDF output status of the object.
+
+There is one required user-specified field: the file name
+(\type{filename}).  It can optionally be augmented by the requested
+image dimensions (\type{width}, \type{depth}, \type{height}),
+user-specified image attributes (\type{attr}), the requested PDF page
+identifier (\type{page}), the requested boundingbox (\type{pagebox})
+for PDF inclusion, the requested color space object (\type{colorspace}).
+
+The function \type{img.new} does not access the actual image file, it
+just creates the \type{<image>} userdata object and initializes some
+memory structures. The \type{<image>} object and its internal
+structures are automatically garbage collected.
+
+Once the image is scanned, all the values in the 
+\type{<image>} become frozen, and you cannot change them any more.
+
+\subsubsubject{\luatex{img.keys}}
+
+\startfunctioncall
+<table> keys = img.keys()
+\stopfunctioncall
+
+This function returns a list of all the possible \type{image_spec}
+keys, both user-supplied and automatic ones. 
+
+% hahe: i need to add r/w ro column...
+\starttabulate[|l|l|p|] 
+\NC Field name    \NC Type     \NC Description \NC \NR
+\NC depth         \NC number   \NC Image depth for \LUATEX\ (in scaled points)\NC \NR
+\NC height        \NC number   \NC Image height for \LUATEX\ (in scaled points)\NC \NR
+\NC width         \NC number   \NC Image width for \LUATEX\  (in scaled points)\NC \NR
+\NC transform     \NC number   \NC Image transform, integer number 0..7\NC \NR
+\NC attr          \NC string   \NC Image attributes for \LUATEX \NC \NR
+\NC filename      \NC string   \NC Image file name \NC \NR
+\NC page          \NC ??       \NC Identifier for the requested image
+                                   page (type is number or string,
+                                   default is the number 1)\NC \NR
+\NC pagebox       \NC string   \NC Requested bounding box. 
+                                   One of "none", "media", "crop", "bleed", "trim", "art" \NC \NR
+\NC filepath      \NC string   \NC Full (expanded) file name of the image \NC \NR
+\NC colordepth    \NC number   \NC Number of bits used by the color space \NC \NR
+\NC colorspace    \NC number   \NC Color space object number \NC \NR
+\NC imagetype     \NC string   \NC One of "pdf", "png", "jpg", "jbig2", or \type{nil} \NC \NR
+\NC objnum        \NC number   \NC PDF image object number \NC \NR
+\NC index         \NC number   \NC PDF image name suffix \NC \NR
+\NC pages         \NC number   \NC Total number of available pages \NC \NR
+\NC xsize         \NC number   \NC Natural image width \NC \NR
+\NC ysize         \NC number   \NC Natural image height \NC \NR
+\NC xres          \NC number   \NC Horizontal natural image resolution (dpi) \NC \NR
+\NC yres          \NC number   \NC Vertical natural image resolution (dpi) \NC \NR
+\stoptabulate
+
+A running (undefined) dimension in \type{width}, \type{height}, or \type{depth} is
+represented as \type{nil} in Lua, so if you want to load an image at
+its `natural' size, you do not have to specify any of those three fields.
+
+The \type{transform} allows to mirror and rotate the image in steps of 90~deg.
+The default value~0 gives an unmirrored, unrotated image.
+Values 1..3 give counterclockwise rotation by 90, 180, or 270~deg.,
+whereas with values 4..7 the image is first mirrored
+and then rotated counterclockwise by 90, 180, or 270~deg.
+The \type{transform} operation gives the same visual result
+as if you would externally preprocess the image by a graphics tool
+and then use it by \LUATEX.
+
+\subsubsubject{\luatex{img.scan}}
+
+\startfunctioncall
+<image> var = img.scan(<image> var) 
+<image> var = img.scan(image_spec)
+\stopfunctioncall
+
+When you say \type{img.scan(a)} for a new image, the file is scanned,
+and variables such as \type{xsize}, \type{ysize}, image \type{type}, number of
+\type{pages}, and the resolution are extracted. Each of the \type{width},
+\type{height}, \type{depth} fields are set up according to the image dimensions,
+if they were not given an explicit value already.
+An image file will never be scanned more than once for a given image variable.
+With all subsequent \type{img.scan(a)} calls only the dimensions are again
+set up (if they have been changed by the user in the meantime).
+
+For ease of use, you can do right-away a 
+\starttyping
+a=img.scan{filename="foo.png"} 
+\stoptyping
+without a prior \type{img.new}.
+
+Nothing is written yet at this point, so you can do \type{a=img.scan},
+retrieve the available info like image width and height, and then
+throw away \type{a} again by saying \type{a=nil}.  In that case no
+image object will be reserved in the PDF, and the used memory will be
+cleaned up automatically.
+
+\subsubsubject{\luatex{img.copy}}
+
+\startfunctioncall
+<image> var = img.copy(<image> var) 
+<image> var = img.copy(image_spec)
+\stopfunctioncall
+
+If you say \type{a = b}, then both variables point to the same
+\type{<image>} object. if you want to write out an image with
+different sizes, you can do a \type{b=img.copy(a)}. 
+
+Afterwards, \type{a} and \type{b} still reference the same actual
+image dictionary, but the dimensions for \type{b} can now be changed
+from their initial values that were just copies from \type{a}.
+
+% Hartmut, I don't know if this makes sense. An example of what
+% can, and what cannot be changed would be helpful.
+% -- will think about it...
+
+\subsubsubject{\luatex{img.write}}
+
+\startfunctioncall
+<image> var = img.write(<image> var)
+<image> var = img.write(image_spec)
+\stopfunctioncall
+
+By \type{img.write(a)} a \PDF\ object number is allocated,
+and a whatsit node of subtype \type{pdf_refximage} is generated
+and put into the output list.
+By this the image \type{a} is placed into the \PDF\ page stream,
+and the image file is written out into an image stream object
+after the shipping of the current page is finished.
+
+Again you can do a terse call like
+
+\starttyping
+img.write{filename="foo.png"}
+\stoptyping
+
+The \type{<image>} variable is returned in case you want it for later
+processing.
+
+\subsubsubject{\luatex{img.immediatewrite}}
+
+\startfunctioncall
+<image> var = img.immediatewrite(<image> var)
+<image> var = img.immediatewrite(image_spec)
+\stopfunctioncall
+
+By \type{img.immediatewrite(a)} a \PDF\ object number is allocated,
+and the image file for image \type{a} is written out immediately
+into the \PDF\ file as an image stream object
+(like with \type{\immediate\pdfximage}).
+The object number of the image stream dictionary is then available
+by the \type{objnum} key.
+No \type{pdf_refximage} whatsit node is generated.
+You will need a \luatex{img.write(a)} or \luatex{img.node(a)} call
+to let the image appear on the page,
+or reference it by another trick;
+else you will have a dangling image object in the \PDF\ file.
+
+Also here you can do a terse call like
+
+\starttyping
+a = img.immediatewrite{filename="foo.png"}
+\stoptyping
+
+The \type{<image>} variable is returned; you will most likely need it.
+
+\subsubsubject{\luatex{img.node}}
+
+\startfunctioncall
+<node> n = img.node(<image> var)
+<node> n = img.node(image_spec)
+\stopfunctioncall
+
+This function allocates a \PDF\ object number
+and returns a whatsit node of subtype \type{pdf_refximage},
+filled with the image parameters \type{width}, \type{height},
+\type{depth}, and \type{objnum}.
+Also here you can do a terse call like:
+
+\starttyping
+n = img.node{filename="foo.png"}
+\stoptyping
+
+This example outputs an image:
+
+\starttyping
+node.write(img.node{filename="foo.png"})
+\stoptyping
+
+\subsubsubject{\luatex{img.types}}
+
+\startfunctioncall
+<table> types = img.types()
+\stopfunctioncall
+
+This function returns a list with the supported image file type names,
+currently these are `pdf', `png', `jpg', and `jbig2'.
+
+\subsubsubject{\luatex{img.boxes}}
+
+\startfunctioncall
+<table> boxes = img.boxes()
+\stopfunctioncall
+
+This function returns a list with the supported \PDF\ page box names,
+currently these are `media', `crop', `bleed', `trim', and `art'
+(all in lowercase letters).
+
+
+\section{The \luatex{mplib} library}
+
+The \MP\ library interface registers itself in the table \type{mplib}. It
+is based on the MPlib beta version 0.40 (based on \MP\ 1.003).
+
+\subsection{\luatex{mplib.new}}
+
+To create a new metapost instance, call 
+
+\startfunctioncall
+   mp = mplib.new({...})
+\stopfunctioncall
+
+This creates the \type{mp} instance object. The argument hash can have a number of
+different fields,  as follows:
+
+\starttabulate[|l|l|p|p|]
+\NC name       \NC         type   \NC description \NC default \NC\NR
+\NC error_line \NC         number \NC line width for terminal and log \NC 79 \NC\NR 
+\NC half_error_line \NC    number \NC ``half'' of line width \NC 50 \NC\NR 
+\NC max_print_line \NC     number \NC line length in ps output\NC 100\NC\NR 
+\NC main_memory \NC        number \NC total memory size \NC 5000\NC\NR 
+\NC hash_size \NC          number \NC hash size\NC 9500 \NC\NR 
+\NC hash_prime \NC         number \NC prime number for hashing\NC 7919\NC\NR 
+\NC param_size \NC         number \NC max. simultaneous macro parameters\NC 150\NC\NR 
+\NC max_in_open \NC        number \NC max. input file nestings \NC 10\NC\NR 
+\NC random_seed \NC        number \NC the initial random seed \NC variable\NC\NR 
+\NC interaction \NC        string \NC the interaction mode, one of
+"batch", "nonstop", "scroll", "errorstop"\NC "errorstop"\NC\NR
+\NC ini_version \NC        boolean \NC the --ini switch\NC false \NC\NR 
+\NC troff_mode \NC         boolean \NC the -T switch \NC false \NC\NR 
+\NC print_found_names \NC  boolean \NC whether long file names 
+                 should be printed to the log and terminal streams\NC false \NC\NR 
+\NC mem_name \NC           string \NC --mem\NC plain.mem\NC\NR 
+\NC job_name \NC           string \NC --jobname\NC mpout \NC\NR 
+\NC find_file \NC          function \NC a function to find files \NC only local files\NC\NR 
+\stoptabulate
+
+The \type{find_file} function should be of this form:
+
+\starttyping
+   string found = finder (string name, string mode, string type)
+\stoptyping
+
+\starttabulate[|l|l|p|]
+\NC name       \NC   the requested file \NC   \NR
+\NC mode       \NC   the file mode: 'r' or 'w' \NC \NR
+\NC type       \NC   the kind of file, one of: 
+                    "mp", "mem", "tfm", "map", "pfb", "enc" \NC \NR
+\stoptabulate
+
+Return either the full pathname of the found file, or \type{nil} if
+the file cannot be found.
+
+\subsection{\luatex{mp:statistics}}
+
+\startfunctioncall
+   table stats = mp:statistics()
+\stopfunctioncall
+
+Returns the vital statistics for an MPlib instance. There are four
+fields, giving the maximum number of used items in each of the four
+statically allocated object classes:
+
+\starttabulate[|l|l|p|]
+\NC main_memory \NC        number \NC memory size \NC\NR 
+\NC hash_size   \NC        number \NC hash size\NC\NR 
+\NC param_size  \NC        number \NC simultaneous macro parameters\NC\NR 
+\NC max_in_open \NC        number \NC input file nesting levels\NC\NR 
+\stoptabulate
+
+\subsection{\luatex{mp:execute}}
+
+You can ask the MP interpreter to run a bit of code by calling
+
+\startfunctioncall
+   local rettable = mp:execute('metapost language chunk')
+\stopfunctioncall
+
+for various bits of Metapost language input. 
+
+Be sure to check the \type{rettable.status} (see below) because when a
+fatal Metapost error occurs the MPlib instance will become unusable
+thereafter.
+
+Generally speaking, it is best to keep your chunks small, but beware
+that all chunks have to obey proper syntax, like each of them is a
+small file. For instance, you cannot split a single statement over
+multiple chunks.
+
+\subsection{\luatex{mp:finish}}
+
+\startfunctioncall
+   local rettable = mp:finish()
+\stopfunctioncall
+
+If for some reason you want to stop using an MPlib instance
+while processing is not yet actually done, you can call
+\type{mp:finish}.  Memory and files can be closed by the 
+Lua garbage collector, but an explicit \type{mp:finish} is
+the only way to capture the final part of the output streams.
+
+\subsection{Result table}
+
+The return value of \type{mp:execute} and \type{mp:finish} is a table
+with a few possible keys (only `status' is always guaranteed to be present).
+
+\starttabulate[|l|l|p|]
+\NC log    \NC string \NC output to the 'log' stream \NC \NR
+\NC term   \NC string \NC output to the 'term' stream \NC \NR
+\NC error  \NC string \NC output to the 'error' stream (only used for
+`Out Of Memory')\NC \NR
+\NC status \NC number \NC the return value. 0 = good, 1 = warning, 2 = errors, 
+                         3 = fatal error \NC \NR
+\NC fig    \NC table \NC An array of generated figures (if any)\NC \NR
+\stoptabulate
+
+When \type{status} equals 3, you should stop using this MPlib instance
+immediately, it is no longer capable of processing input. 
+
+If it is present, each of the entries in the \type{fig} array is a
+userdata representing a figure object, and each of those has a number of
+object methods you can call:
+
+\starttabulate[|l|l|p|]
+\NC boundingbox  \NC function \NC returns the bounding box, as an array of 4 values\NC \NR
+\NC postscript   \NC function \NC return a string that is the ps output of the \type{fig} \NC \NR
+\NC objects      \NC function \NC returns the actual array of graphic objects in this \type{fig} \NC \NR
+\NC copy_objects \NC function \NC returns a deep copy of the array of graphic objects in this \type{fig} \NC \NR
+\NC filename     \NC function \NC the filename this \type{fig}'s PostScript output
+                                  would have written to in standalone mode\NC \NR
+\stoptabulate
+
+{\bf NOTE:} you can call \type{fig:objects()} only once for any one \type{fig} object!
+
+When the boundingbox represents a `negated rectangle' (i.w. the first set
+of coordinates is larger than the second set), the picture is empty.
+
+Graphical objects come in various types that each have a different list of
+accessible values. The types are: 'fill', 'outline', 'text',
+'start_clip', 'stop_clip', 'start_bounds', 'stop_bounds', 'special'.
+
+There is helper function (\type{mplib.fields(obj)}) to get the list of
+accessible values for a particular object, but you can just as easily
+use the tables given below.
+
+All graphical objects have a field \type{type} that gives the object
+type as a string value, that not explicit mentioned in the tables.  In
+the following, \type{number}s are PostScript points represented as
+a floating point number, unless stated otherwise. Field values that
+are of \type{table} are explained in the next section.
+
+\subsubsection{fill}
+
+\starttabulate[|l|l|p|]
+\NC path       \NC table \NC the list of knots \NC \NR
+\NC htap       \NC table \NC the list of knots for the reversed trajectory \NC \NR
+\NC pen        \NC table \NC knots of the pen \NC \NR
+\NC color      \NC table \NC the object's color \NC \NR
+\NC linejoin   \NC number \NC line join style (bare number)\NC \NR
+\NC miterlimit \NC number \NC miterlimit\NC \NR
+\NC prescript  \NC string \NC the prescript text \NC \NR
+\NC postscript \NC string \NC the postscript text \NC \NR
+\stoptabulate
+
+The entries \type{htap} and \type{pen} are optional.
+
+\subsubsection{outline}
+
+\starttabulate[|l|l|p|]
+\NC path \NC table \NC the list of knots \NC \NR
+\NC pen \NC table \NC knots of the pen \NC \NR
+\NC color \NC table \NC the object's color \NC \NR
+\NC linejoin \NC number \NC line join style (bare number)\NC \NR
+\NC miterlimit \NC number \NC miterlimit \NC \NR
+\NC linecap \NC number \NC line cap style (bare number)\NC \NR
+\NC dash \NC table \NC representation of a dash list\NC \NR
+\NC prescript \NC string \NC the prescript text \NC \NR
+\NC postscript \NC string \NC the postscript text \NC \NR
+\stoptabulate
+
+The entry \type{dash} is optional.
+ 
+\subsubsection{text}
+
+\starttabulate[|l|l|p|]
+\NC text \NC string \NC the text \NC \NR
+\NC font \NC string \NC font tfm name \NC \NR
+\NC dsize \NC number \NC font size\NC \NR
+\NC color \NC table \NC the object's color \NC \NR
+\NC width \NC number \NC  \NC \NR
+\NC height \NC number \NC  \NC \NR
+\NC depth \NC number \NC  \NC \NR
+\NC transform \NC table \NC a text transformation \NC \NR
+\NC prescript \NC string \NC the prescript text \NC \NR
+\NC postscript \NC string \NC the postscript text \NC \NR
+\stoptabulate
+
+\subsubsection{special}
+
+\starttabulate[|l|l|p|]
+\NC prescript \NC string \NC special text \NC \NR
+\stoptabulate
+
+
+\subsubsection{start_bounds, start_clip}
+
+\starttabulate[|l|l|p|]
+\NC path \NC table \NC the list of knots \NC \NR
+\stoptabulate
+
+\subsubsection{stop_bounds, stop_clip}
+
+No fields available.
+
+\subsection{Subsidiary table formats}
+
+\subsubsection{Paths and pens}
+
+Paths and pens (that are really just a special type of paths as far as
+MPlib is concerned) are represented by an array where each entry
+is a table that represents a knot. 
+
+\starttabulate[|l|l|p|]
+\NC left_type	\NC string \NC when present: 'endpoint', but ususally absent \NC \NR
+\NC right_type	\NC string \NC like \type{left_type}\NC \NR
+\NC x_coord		\NC number \NC X coordinate of this knot\NC \NR
+\NC y_coord		\NC number \NC Y coordinate of this knot\NC \NR
+\NC left_x		\NC number \NC X coordinate of the precontrol point of this knot\NC \NR
+\NC left_y		\NC number \NC Y coordinate of the precontrol point of this knot\NC \NR
+\NC right_x		\NC number \NC X coordinate of the postcontrol point of this knot\NC \NR
+\NC right_y		\NC number \NC Y coordinate of the postcontrol point of this knot\NC \NR
+\stoptabulate
+
+There is one special case: pens that are (possibly transformed)
+ellipses have an extra string-valued key \type{type} with value
+\type{elliptical} besides the array part containing the knot list.
+
+\subsubsection{Colors}
+
+A color is an integer array with 0, 1, 3 or 4 values:
+
+\starttabulate[|l|l|p|]
+\NC 0  \NC Marking only \NC No values. \NC\NR
+\NC 1  \NC Greyscale    \NC 0ne value in the range 0 .. 1, `black' is 0 \NC\NR
+\NC 3  \NC RGB          \NC 3 values in the range 0 .. 1, `black' is 0,0,0  \NC\NR
+\NC 4  \NC CMYK         \NC 4 values in the range 0 .. 1, `black' is 0,0,0,1  \NC\NR
+\stoptabulate
+
+If the color model of the internal object was \type{unitialized}, then
+it was initialized to the values representing `black' in the colorspace
+\type{defaultcolormodel} that was in effect at the time of the \type{shipout}.
+
+\subsubsection{Transforms}
+
+Each transform is a six-item array.
+
+\starttabulate[|l|l|p|]
+\NC 1 \NC number \NC represents x \NC\NR
+\NC 2 \NC number \NC represents y \NC\NR
+\NC 3 \NC number \NC represents xx \NC\NR
+\NC 4 \NC number \NC represents yx \NC\NR
+\NC 5 \NC number \NC represents xy \NC\NR
+\NC 6 \NC number \NC represents yy \NC\NR
+\stoptabulate
+
+Note that the translation (index 1 and 2) comes first. This differs
+from the ordering in  PostScript, where the translation comes last.
+
+\subsubsection{Dashes}
+
+Each \type{dash} is two-item hash, using the same model as PostScript
+for the representation of the dashlist. \type{dashes} is an array of
+`on' and `off', values, and \type{offset} is the phase of the pattern.
+
+\starttabulate[|l|l|p|]
+\NC dashes \NC hash   \NC an array of on-off numbers \NC\NR
+\NC offset \NC number \NC the starting offset value \NC\NR
+\stoptabulate
+
+
+\section{The \luatex{callback} library}
+
+This library has functions that register, find and list callbacks.
+
+The \luatex{callback} library is only available in \LUA\ state zero (0).
+
+\startfunctioncall
+id, error = callback.register(string callback_name,function callback_func)
+id, error = callback.register(string callback_name,nil)
+\stopfunctioncall
+
+where the \syntax{callback_name} is a predefined callback name, see
+below. The function returns the internal \type{id} of the callback
+or \type{nil}, if the callback could not be registered. In the latter
+case, \type{error} contains an error message, otherwise it is
+\type{nil}.
+
+\LUATEX\ internalizes the callback function in such a way that
+it does not matter if you redefine a function accidentally.
+% hahe: what happens then?
+
+Callback assignments are always global. You can use the special value
+\type {nil} instead of a function for clearing the callback.
+
+Currently, callbacks are not dumped into the format file.
+
+\startfunctioncall
+table info = callback.list()
+\stopfunctioncall
+
+The keys in the table are the known callback names, the value is a
+boolean where \type{true} means that the callback is currently set
+(active).
+
+\startfunctioncall
+function f = callback.find(callback_name)
+\stopfunctioncall
+
+If the callback is not set, \luatex{callback.find} returns \type{nil}.
+
+\subsection{File discovery callbacks}
+
+\subsubsection{\luatex{find_read_file} and \luatex{find_write_file}}
+
+Your callback function should have the following conventions:
+
+\startfunctioncall
+string actual_name = function (number id_number, string asked_name)
+\stopfunctioncall
+
+Arguments:
+
+\startitemize
+
+\sym{id_number} 
+
+This number is zero for the log or \tex {input} files. For \TEX's \tex{read} or
+\tex{write} the number is incremented by one, so \tex{read0} becomes~1.
+
+\sym{asked_name} 
+
+This is the user|-|supplied filename, as found by \tex{input}, \tex{openin}
+or \tex{openout}.
+
+\stopitemize
+
+Return value:
+
+\startitemize
+
+\sym{actual_name} 
+
+This is the filename used. For the very first file that is read in by
+\TEX, you have to make sure you return an \type{actual_name} that has
+an extension and that is suitable for use as \type{jobname}. If you
+don't, you will have to manually fix the name of the log file and
+output file after \LUATEX\ is finished, and an eventual format
+filename will become mangled. That is because these file names depend
+on the jobname.
+
+You have to return \type{nil} if the file cannot be found.
+
+\stopitemize
+
+\subsubsection{\luatex{find_font_file}}
+
+Your callback function should have the following conventions:
+
+\startfunctioncall
+string actual_name = function (string asked_name)
+\stopfunctioncall
+
+The \type{asked_name} is an \OTF\ or \TFM\ font metrics file.
+
+Return \type{nil} if the file cannot be found.
+
+\subsubsection{\luatex{find_output_file}}
+
+Your callback function should have the following conventions:
+
+\startfunctioncall
+string actual_name = function (string asked_name)
+\stopfunctioncall
+
+The \type{asked_name} is the \PDF\ or \DVI\ file for writing.
+
+\subsubsection{\luatex{find_format_file}}
+
+Your callback function should have the following conventions:
+
+\startfunctioncall
+string actual_name = function (string asked_name)
+\stopfunctioncall
+
+The \type{asked_name} is a format file for reading (the format file
+for writing is always opened in the current directory).
+
+\subsubsection{\luatex{find_vf_file}}
+
+Like \luatex{find_font_file}, but for virtual fonts. This applies to
+both \ALEPH's \OVF\ files and traditional Knuthian \VF\ files.
+
+\subsubsection{\luatex{find_ocp_file}}
+
+Like \luatex{find_font_file}, but for ocp files.
+
+\subsubsection{\luatex{find_map_file}}
+
+Like \luatex{find_font_file}, but for map files.
+
+\subsubsection{\luatex{find_enc_file}}
+
+Like \luatex{find_font_file}, but for enc files.
+
+\subsubsection{\luatex{find_sfd_file}}
+
+Like \luatex{find_font_file}, but for subfont definition files.
+
+\subsubsection{\luatex{find_pk_file}}
+
+Like \luatex{find_font_file}, but for pk bitmap files. The argument
+\type{name} is a bit special in this case. Its form is
+
+\starttyping
+<base res>dpi/<fontname>.<actual res>pk
+\stoptyping
+
+So you may be asked for \type{600dpi/manfnt.720pk}.  It is up to you
+to find a \quote{reasonable} bitmap file to go with that specification.
+
+\subsubsection{\luatex{find_data_file}}
+
+Like \luatex{find_font_file}, but for embedded files (\tex{pdfobj file '...'}).
+
+\subsubsection{\luatex{find_opentype_file}}
+
+Like \luatex{find_font_file}, but for \OPENTYPE\ font files.
+
+\subsubsection{\luatex{find_truetype_file} and \luatex{find_type1_file}}
+
+Your callback function should have the following conventions:
+
+\startfunctioncall
+string actual_name = function (string asked_name)
+\stopfunctioncall
+
+The \type{asked_name} is a font file. This callback is called while
+\LUATEX\ is building its internal list of needed font files, so the
+actual timing may surprise you. Your return value is later fed back
+into the matching \luatex{read_file} callback.
+
+Strangely enough, \luatex{find_type1_file} is also used for \OPENTYPE\
+(\OTF) fonts.
+
+\subsubsection{\luatex{find_image_file}}
+
+Your callback function should have the following conventions:
+
+\startfunctioncall
+string actual_name = function (string asked_name)
+\stopfunctioncall
+
+The \type{asked_name} is an image file. Your return value is used to
+open a file from the harddisk, so make sure you return something that
+is considered the name of a valid file by your operating system.
+
+\subsection[iocallback]{File reading callbacks}
+
+\subsubsection{\luatex{open_read_file}}
+
+Your callback function should have the following conventions:
+
+\startfunctioncall
+table env = function (string file_name)
+\stopfunctioncall
+
+Argument:
+
+\startitemize
+
+\sym{file_name} 
+
+The filename returned by a previous \luatex{find_read_file} or the return
+value of \luatex{kpse.find_file()} if there was no such callback defined.
+
+\stopitemize
+
+Return value:
+
+\startitemize
+
+\sym{env} 
+
+This is a table containing at least one required and one optional
+callback function for this file. The required field is
+\luatex{reader} and the associated function will be called once
+for each new line to be read, the optional one is \luatex{close}
+that will be called once when \LUATEX\ is done with the file.
+
+\LUATEX\ never looks at the rest of the table, so you can use it to
+store your private per|-|file data. Both the callback functions will
+receive the table as their only argument.
+
+\stopitemize
+
+\subsubsubsection{\luatex{reader}}
+
+\LUATEX\ will run this function whenever it needs a new input line
+from the file.
+
+\startfunctioncall
+function(table env)
+    return string line
+end
+\stopfunctioncall
+
+Your function should return either a string or \type{nil}. The value \type{nil}
+signals that the end of file has occurred, and will make \TEX\ call
+the optional \luatex{close} function next.
+
+\subsubsubsection{\luatex{close}}
+
+\LUATEX\ will run this optional function when it decides to close the file.
+
+\startfunctioncall
+function(table env)
+    return
+end
+\stopfunctioncall
+
+Your function should not return any value.
+
+\subsubsection{General file readers}
+
+There is a set of callbacks for the loading of binary data
+files. These all use the same interface:
+
+\startfunctioncall
+function(string name)
+    return boolean success, string data, number data_size
+end
+\stopfunctioncall
+
+The \type{name} will normally be a full path name as it is returned by
+either one of the file discovery callbacks or the internal version of
+\luatex{kpse.find_file()}.
+
+\startitemize
+
+\sym{success} 
+
+Return false when a fatal error occured (e.\,g.\ when the file cannot be
+found, after all).
+
+\sym{data} 
+
+The bytes comprising the file.
+
+\sym{data_size} 
+
+The length of the \type{data}, in bytes.
+
+\stopitemize
+
+Return an empty string and zero if the file was found but there was a
+reading problem.
+
+The list of functions is:
+\starttabulate[|l|p|]
+\NC \luatex{read_font_file} \NC This function is called when \TEX\ needs to read a \type{ofm} or
+                                \type{tfm} file. \NC\NR
+\NC \luatex{read_vf_file}       \NC for virtual fonts.\NC\NR
+\NC \luatex{read_ocp_file}      \NC for ocp files.\NC\NR
+\NC \luatex{read_map_file}      \NC for map files.\NC\NR
+\NC \luatex{read_enc_file}      \NC for encoding files.\NC\NR
+\NC \luatex{read_sfd_file}      \NC for subfont definition files.\NC\NR
+\NC \luatex{read_pk_file}       \NC for pk bitmap files. \NC\NR
+\NC \luatex{read_data_file}     \NC for embedded files (\tex{pdfobj file '...'}).\NC\NR
+\NC \luatex{read_truetype_file} \NC for \TRUETYPE\ font files. \NC\NR
+\NC \luatex{read_type1_file}    \NC for \TYPEONE\ font files.\NC\NR
+\NC \luatex{read_opentype_file} \NC for \OPENTYPE\ font files.  \NC\NR
+\stoptabulate
+
+\subsection{Data processing callbacks}
+
+\subsubsection{\luatex{process_input_buffer}}
+
+
+This callback allows you to change the contents of the line input
+buffer just before \LUATEX\ actually starts looking at it.
+
+\startfunctioncall
+function(string buffer)
+    return string adjusted_buffer
+end
+\stopfunctioncall
+
+If you return \type{nil}, \LUATEX\ will pretend like your callback
+never happened. You can gain a small amount of processing time from
+that.
+
+
+\subsubsection{\luatex{token_filter}}
+
+This callback allows you to replace the way \LUATEX\ fetches
+lexical tokens.
+
+\startfunctioncall
+function()
+    return table token
+end
+\stopfunctioncall
+
+The calling convention for this callback is a bit more complicated than
+for most other callbacks.  The function should either return a \LUA\
+table representing a valid to|-|be|-|processed token or tokenlist, or
+something else like nil or an empty table.
+
+If your \LUA\ function does not return a table representing a valid
+token, it will be immediately called again, until it eventually does
+return a useful token or tokenlist (or until you reset the callback
+value to nil). See the description of \luatex{token} for some
+handy functions to be used in conjunction with this callback.
+
+If your function returns a single usable token, then that token will
+be processed by \LUATEX\ immediately. If the function returns a token
+list (a table consisting of a list of consecutive token tables), then
+that list will be pushed to the input stack at a completely new token
+list level, with its token type set to \quote{inserted}. In either case,
+the returned token(s) will not be fed back into the callback function.
+
+\subsection{Node list processing callbacks}
+
+The description of nodes and node lists is in~\in{chapter}[nodes].
+
+\subsubsection{\luatex{buildpage_filter}}
+
+This callback is called whenever \LUATEX\ is ready to move stuff to
+the main vertical list. You can use this callback to do specialized
+manipulation of the page building stage like imposition or column
+balancing.
+
+\startfunctioncall
+function(<node> head, string extrainfo)
+    return true | false | <node> newhead
+end
+\stopfunctioncall
+
+As for all the callbacks that deal with nodes, the return value can be
+one of three things:
+
+\startitemize[packed]
+\item \type{boolean true} signals succesful processing
+\item \type{node} signals that the \quote{head} node should be
+replaced by this node
+\item \type{boolean false} signals that the \quote{head} node list should be
+ignored and flushed from memory
+\stopitemize
+
+The string \type{extrainfo} gives some additional information about
+what \TEX's state is with respect to the \quote{current page}. The possible
+values are:
+
+\starttabulate[|lT|p|]
+\NC \bf value           \NC \bf explanation                        \NC\NR
+\NC \tt alignment       \NC a (partial) alignment is being added   \NC\NR
+\NC \tt box             \NC a typeset box is being added           \NC\NR
+\NC \tt begin_of_par    \NC the beginning of a new paragraph       \NC\NR
+\NC \tt vmode_par       \NC \tex{par} was found in vertical mode   \NC\NR
+\NC \tt hmode_par       \NC \tex{par} was found in horizontal mode \NC\NR
+\NC \tt insert          \NC an insert is added                     \NC\NR
+\NC \tt penalty         \NC a penalty (in vertical mode)           \NC\NR
+\NC \tt before_display  \NC immediately before a display starts    \NC\NR
+\NC \tt after_display   \NC a display is finished                  \NC\NR
+\stoptabulate
+
+\subsubsection{\luatex{pre_linebreak_filter}}
+
+This callback is called just before \LUATEX\ starts converting a list
+of nodes into a stack of \tex{hbox}es. The removal of a possible final skip
+and the subsequent insertion of \tex{parfillskip} has not happened
+yet at that moment.
+
+\startfunctioncall
+function(<node> head, string groupcode)
+    return true | false | <node> newhead
+end
+\stopfunctioncall
+
+The string called \type {groupcode} identifies the nodelist's context
+within \TEX's processing. The range of possibilities is given in the
+table below, but not all of those can actually appear in
+\luatex {pre_linebreak_filter}, some are for the
+\luatex {hpack_filter} and \luatex {vpack_filter} callbacks that 
+will be explained in the next two paragraphs.
+
+\starttabulate[|lT|p|]
+\NC \bf value        \NC \bf explanation                           \NC\NR
+\NC \tt hbox         \NC \tex{hbox} in horizontal mode             \NC\NR
+\NC \tt adjusted_hbox\NC \tex{hbox} in vertical mode               \NC\NR
+\NC \tt vbox         \NC \tex{vbox}                                \NC\NR
+\NC \tt vtop         \NC \tex{vtop}                                \NC\NR
+\NC \tt align        \NC \tex{halign} or \tex{valign}              \NC\NR
+\NC \tt disc         \NC discretionaries                           \NC\NR
+\NC \tt insert       \NC packaging an insert                       \NC\NR
+\NC \tt vcenter      \NC \tex{vcenter}                             \NC\NR
+\NC \tt local_box    \NC \tex{localleftbox} or \tex{localrightbox} \NC\NR
+\NC \tt split_off    \NC top of a \tex{vsplit}                     \NC\NR
+\NC \tt split_keep   \NC remainder of a \tex{vsplit}               \NC\NR
+\NC \tt align_set    \NC alignment cell                            \NC\NR
+\NC \tt fin_row      \NC alignment row                             \NC\NR
+\stoptabulate
+
+\subsubsection{\luatex{post_linebreak_filter}}
+
+This callback is called just after \LUATEX\ has converted a list
+of nodes into a stack of \tex{hbox}es. 
+
+\startfunctioncall
+function(<node> head, string groupcode)
+    return true | false | <node> newhead
+end
+\stopfunctioncall
+
+\subsubsection{\luatex{hpack_filter}}
+
+This callback is called when \TEX\ is ready to start boxing some
+horizontal mode material. Math items are ignored at the moment.
+
+\startfunctioncall
+function(<node> head, string groupcode, number size, string packtype)
+    return true | false | <node> newhead
+end
+\stopfunctioncall
+
+The \type{packtype} is either \type{additional} or \type{exactly}. If
+\type{additional}, then the \type{size} is a \tex{hbox spread ...}
+argument. If \type{exactly}, then the \type{size} is a \tex{hbox to ...}.
+In both cases, the number is in scaled points.
+
+\subsubsection{\luatex{vpack_filter}}
+
+This callback is called when \TEX\ is ready to start boxing some
+vertical mode material. Math displays are ignored at the moment.
+
+This function is very similar to the \luatex{hpack_filter}. Besides
+the fact that it is called at different moments, there is an extra
+variable that matches \TEX's \tex{maxdepth} setting.
+
+\startfunctioncall
+function(<node> head, string groupcode, number size, string packtype,  number maxdepth)
+    return true | false | <node> newhead
+end
+\stopfunctioncall
+
+\subsubsection{\luatex{pre_output_filter}}
+
+This callback is called when \TEX\ is ready to start boxing the
+box 255 for \tex{output}.
+
+\startfunctioncall
+function(<node> head, string groupcode, number size, string packtype, number maxdepth)
+    return true | false | <node> newhead
+end
+\stopfunctioncall
+
+\subsubsection{\luatex{hyphenate}}
+
+\startfunctioncall
+function(<node> head, <node> tail)
+end
+\stopfunctioncall
+
+No return values. This callback has to insert discretionary nodes in
+the node list it receives.
+
+
+\subsubsection{\luatex{ligaturing}}
+
+\startfunctioncall
+function(<node> head, <node> tail)
+end
+\stopfunctioncall
+
+No return values. This callback has to apply ligaturing to the node
+list it receives.
+
+You don't have to worry about return values because the \type{head}
+node that is passed on to the callback is guaranteed not to be a
+glyph_node (if need be, a temporary node will be prepended), and
+therefore it cannot be affected by the mutations that take place.  
+After the callback, the internal value of the `tail of the list' 
+will be recalculated. 
+
+The \type{next} of \type{head} is guaranteed to be non-nil.
+
+The \type{next} of \type{tail} is guaranteed be nil, and therefore the
+second callback argument can often be ignored. It is provided for
+orthogonality, and because it can sometimes be handy when special
+processing has to take place.
+
+\subsubsection{\luatex{kerning}}
+
+\startfunctioncall
+function(<node> head, <node> tail) end
+\stopfunctioncall
+
+No return values. This callback has to apply kerning between the nodes
+in the node list it receives. See \type{ligaturing} for calling
+conventions.
+
+
+\subsection{Information reporting callbacks}
+
+\subsubsection{\luatex{start_run}}
+
+\startfunctioncall
+function()
+\stopfunctioncall
+
+Replaces the code that prints \LUATEX's banner.
+
+\subsubsection{\luatex{stop_run}}
+
+\startfunctioncall
+function()
+\stopfunctioncall
+
+Replaces the code that prints \LUATEX's statistics and \quote{output written
+to} messages.
+
+\subsubsection{\luatex{start_page_number}}
+
+\startfunctioncall
+function()
+\stopfunctioncall
+
+Replaces the code that prints the \type{[} and the page number at the
+begin of \tex{shipout}. This callback will also override the
+printing of box information that normally takes place when
+\tex{tracingoutput} is positive.
+
+\subsubsection{\luatex{stop_page_number}}
+
+\startfunctioncall
+function()
+\stopfunctioncall
+
+Replaces the code that prints the \type{]} at the end of \tex{shipout}.
+
+\subsubsection{\luatex{show_error_hook}}
+
+\startfunctioncall
+function()
+    return
+end
+\stopfunctioncall
+
+This callback is run from inside the \TEX\ error function, and the idea
+is to allow you to do some extra reporting on top of what \TEX\ already
+does (none of the normal actions are removed). You may find some of
+the values in the \luatex{status} table useful.
+
+\startitemize
+
+\sym{message} 
+
+is the formal error message \TEX\ has given to the user.
+(the line after the '!').
+
+\sym{indicator} 
+
+is either a filename (when it is a string) or a location indicator (a
+number) that can mean lots of different things like a token list id
+or a \tex{read} number.
+
+\sym{lineno} 
+
+is the current line number.
+\stopitemize
+
+This is an investigative item for 'testing the water' only.
+The final goal is the total replacement of \TEX's error handling
+routines, but that needs lots of adjustments in the web source because
+\TEX\ deals with errors in a somewhat haphazard fashion. This is why the
+exact definition of \type{indicator} is not given here.
+
+\subsection{Font-related callbacks}
+
+\subsubsection{\luatex{define_font}}
+
+\startfunctioncall
+function(string name, number size, number id) return table font end
+\stopfunctioncall
+
+The string \type{name} is the filename part of the font
+specification, as given by the user.
+
+The number \type{size} is a bit special:
+
+\startitemize[packed]
+\item if it is positive, it specifies an \quote{at size} in scaled points.
+\item if it is negative, its absolute value represents a \quote{scaled}
+setting relative to the designsize of the font.
+\stopitemize
+
+The internal structure of the \type{font} table that is to be
+returned is explained in \in{chapter}[fonts]. That table is saved
+internally, so you can put extra fields in the table for your
+later \LUA\ code to use.
+
+\section{The \luatex{lua} library}
+
+This library contains two read|-|only  items:
+
+\subsection{Variables}
+
+\starttyping
+number n = lua.id
+\stoptyping
+
+This returns the id number of the instance.
+
+\starttyping
+string s = lua.version
+\stoptyping
+
+This returns a \LUATEX\ version identifier string. The value is
+currently \directlua0{tex.print('lua.version')}, but it is soon to be
+replaced by something more elaborate.
+
+\subsection{\LUA\ bytecode registers}
+
+\LUA\ registers can be used to communicate \LUA\ functions across \LUA\
+states. The accepted values for assignments are functions and
+nil. Likewise, the retrieved value is either a function or \type{nil}.
+
+\starttyping
+lua.bytecode[n] = function () .. end
+lua.bytecode[n]()
+\stoptyping
+
+The contents of the \luatex{lua.bytecode} array is stored inside the format
+file as actual \LUA\ bytecode, so it can also be used to preload \LUA\ code.
+
+Note: The function must not contain any upvalues. Currently, functions
+containing upvalues can be stored (and their upvalues are set to
+\type{nil}), but this is an artefact of the current \LUA\
+implementation and thus subject to change.
+
+The associated function calls are
+
+\startfunctioncall
+function f = lua.getbytecode(number n)
+lua.setbytecode(number n, function f)
+\stopfunctioncall
+
+Note: Since a \LUA\ file loaded using \luatex{loadfile(filename)} is
+essentially an anonymous function, a complete file can be stored in a
+bytecode register like this:
+
+\startfunctioncall
+lua.bytecode[n] = loadfile(filename)
+\stopfunctioncall
+
+Now all definitions (functions, variables) contained in the file can be
+created by executing this bytecode register:
+
+\startfunctioncall
+lua.bytecode[n]()
+\stopfunctioncall
+
+\section{The \luatex{kpse} library}
+
+This library provides an interface to the \KPATHSEA\ file search method.
+
+Before the search library can be used at all, its database has to be
+initialized. When \LUATEX\ is used to typeset documents, this happens
+automatically (that is, unless explicitly prohibited by the user's
+startup script. See~\in{section}[init] for more details). In \TEXLUA\
+mode, the initialization has to be done explicitly via the
+\luatex{kpse.set_program_name} function.
+
+\subsection{\luatex{kpse.set_program_name}}
+
+Sets the \KPATHSEA\ executable (and optionally program) name.
+
+\startfunctioncall
+kpse.set_program_name(string name)
+kpse.set_program_name(string name, string progname)
+\stopfunctioncall
+
+The second argument controls the use of the \quote{dotted} values in the
+\type{texmf.cnf} configuration file, and defaults to the first argument.
+
+
+\subsection{\luatex{kpse.find_file}}
+
+The most often used function in the library is find_file:
+
+\startfunctioncall
+string f = kpse.find_file(string filename)
+string f = kpse.find_file(string filename, string ftype)
+string f = kpse.find_file(string filename, boolean mustexist)
+string f = kpse.find_file(string filename, string ftype, boolean mustexist)
+string f = kpse.find_file(string filename, string ftype, number dpi)
+\stopfunctioncall
+
+Arguments:
+\startitemize[intro]
+
+\sym{filename} 
+
+the name of the file you want to find, with or without extension.
+
+\sym{ftype}
+
+maps to the \type {-format} argument of \KPSEWHICH.  The supported
+ \type{ftype} values are the same as the ones supported by the 
+standalone \type{kpsewhich} program:
+
+\startsimplecolumns
+\starttyping
+'gf'
+'pk'
+'bitmap font'
+'tfm'
+'afm'
+'base'
+'bib'
+'bst'
+'cnf'
+'ls-R'
+'fmt'
+'map'
+'mem'
+'mf'
+'mfpool'
+'mft'
+'mp'
+'mppool'
+'MetaPost support'
+'ocp'
+'ofm'
+'opl'
+'otp'
+'ovf'
+'ovp'
+'graphic/figure'
+'tex'
+'TeX system documentation'
+'texpool'
+'TeX system sources'
+'PostScript header'
+'Troff fonts'
+'type1 fonts'
+'vf'
+'dvips config'
+'ist'
+'truetype fonts'
+'type42 fonts'
+'web2c files'
+'other text files'
+'other binary files'
+'misc fonts'
+'web'
+'cweb'
+'enc files'
+'cmap files'
+'subfont definition files'
+'opentype fonts'
+'pdftex config'
+'lig files'
+'texmfscripts'
+\stoptyping
+\stopsimplecolumns
+
+The default type is \type{tex}.
+
+\sym{mustexist}
+
+is similar to \KPSEWHICH's \type{-must-exist}, and the default is \type{false}.
+If you specify \type{true} (or a non|-|zero integer), then the \KPSE\ library
+will search the disk as well as the \type {ls-R} databases.
+
+\sym{dpi}
+
+This is used for the size argument of the formats \type{pk}, \type{gf}, and \type{bitmap font}.
+\stopitemize
+
+\subsection{\luatex{kpse.init_prog}}
+
+Extra initialization for programs that need to generate bitmap fonts.
+
+\startfunctioncall
+kpse.init_prog(string prefix, number base_dpi, string mfmode)
+kpse.init_prog(string prefix, number base_dpi, string mfmode, string fallback)
+\stopfunctioncall
+
+
+\subsection{\luatex{kpse.readable_file}}
+
+Test if an (absolute) file name is a readable file
+
+\startfunctioncall
+string f = kpse.readable_file(string name)
+\stopfunctioncall
+
+The return value is the actual absolute filename you should use,
+because the disk name is not always the same as the requested name,
+due to aliases and system|-|specific handling under e.\,g.\ \MSDOS.
+
+Returns \lua {nil} if the file does not exist or is not readable.
+
+\subsection{\luatex{kpse.expand_path}}
+
+Like kpsewhich's \type {-expand-path}:
+
+\startfunctioncall
+string r = kpse.expand_path(string s)
+\stopfunctioncall
+
+\subsection{\luatex{kpse.expand_var}}
+
+Like kpsewhich's  \type{-expand-var}:
+
+\startfunctioncall
+string r = kpse.expand_var(string s)
+\stopfunctioncall
+
+\subsection{\luatex{kpse.expand_braces}}
+
+Like kpsewhich's \type{-expand-braces}:
+
+\startfunctioncall
+string r = kpse.expand_braces(string s)
+\stopfunctioncall
+
+\subsection{\luatex{kpse.show_path}}
+
+Like kpsewhich's \type{-show-path}:
+
+\startfunctioncall
+string r = kpse.show_path(string ftype)
+\stopfunctioncall
+
+
+\subsection{\luatex{kpse.var_value}}
+
+Like kpsewhich's \type{-var-value}:
+
+\startfunctioncall
+string r = kpse.var_value(string s)
+\stopfunctioncall
+
+\section{The \luatex{status} library}
+
+This contains a number of run|-|time configuration items that
+you may find useful in message reporting, as well as an iterator
+function that gets all of the names and values as a table.
+
+\startfunctioncall
+table info = status.list()
+\stopfunctioncall
+
+The keys in the table are the known items, the value is the current
+value.
+
+Almost all of the values in \type{status} are fetched through a
+metatable at run|-|time whenever they are accessed, so you cannot use
+\type{pairs} on \type{status}, but you {\it can\/} use \type{pairs}
+on \type{info}, of course.
+
+If you do not need the full list, you can also ask for a single item
+by using its name as an index into \type{status}.
+
+The current list is:
+
+\starttabulate[|lT|p|]
+\NC \ssbf key    \NC  \bf explanation \NC\NR
+\NC pdf_gone\NC                  written \PDF\ bytes      \NC \NR
+\NC pdf_ptr\NC                   not yet written \PDF\ bytes      \NC \NR
+\NC dvi_gone\NC                  written \DVI\ bytes      \NC \NR
+\NC dvi_ptr\NC                   not yet written \DVI\ bytes      \NC \NR
+\NC total_pages\NC               number of written pages      \NC \NR
+\NC output_file_name\NC          name of the \PDF\ or \DVI\ file      \NC \NR
+\NC log_name\NC                  name of the log file      \NC \NR
+\NC banner\NC                    terminal display banner      \NC \NR
+\NC var_used\NC                  variable (one|-|word) memory in use \NC \NR
+\NC dyn_used\NC                  token (multi|-|word) memory in use  \NC \NR
+\NC str_ptr\NC                   number of strings      \NC \NR
+\NC init_str_ptr\NC              number of \INITEX\ strings      \NC \NR
+\NC max_strings\NC               maximum allowed strings      \NC \NR
+\NC pool_ptr\NC                  string pool index      \NC \NR
+\NC init_pool_ptr\NC             \INITEX\ string pool index      \NC \NR
+\NC pool_size\NC                 current size allocated for string characters \NC \NR
+\NC node_mem_usage\NC            a string giving insight into currently used nodes\NC\NR
+\NC var_mem_max\NC               number of allocated words for nodes\NC \NR
+\NC fix_mem_max\NC               number of allocated words for tokens\NC \NR
+\NC fix_mem_end\NC               maximum number of used tokens\NC \NR
+\NC cs_count\NC                  number of control sequences      \NC \NR
+\NC hash_size\NC                 size of hash       \NC \NR
+\NC hash_extra\NC                extra allowed hash  \NC \NR
+\NC font_ptr\NC                  number of active fonts      \NC \NR
+\NC max_in_stack\NC              max used input stack entries      \NC \NR
+\NC max_nest_stack\NC            max used nesting stack entries     \NC \NR
+\NC max_param_stack\NC           max used parameter stack entries     \NC \NR
+\NC max_buf_stack\NC             max used buffer position      \NC \NR
+\NC max_save_stack\NC            max used save stack entries      \NC \NR
+\NC stack_size\NC                input stack size      \NC \NR
+\NC nest_size\NC                 nesting stack size      \NC \NR
+\NC param_size\NC                parameter stack size      \NC \NR
+\NC buf_size\NC                  current allocated size of the line buffer \NC \NR
+\NC save_size\NC                 save stack size      \NC \NR
+\NC obj_ptr\NC                   max \PDF\ object pointer      \NC \NR
+\NC obj_tab_size\NC              \PDF\ object table size      \NC \NR
+\NC pdf_os_cntr\NC               max \PDF\ object stream pointer      \NC \NR
+\NC pdf_os_objidx\NC             \PDF\ object stream index \NC \NR
+\NC pdf_dest_names_ptr\NC        max \PDF\ destination pointer       \NC \NR
+\NC dest_names_size\NC           \PDF\ destination table size      \NC \NR
+\NC pdf_mem_ptr\NC               max \PDF\ memory used      \NC \NR
+\NC pdf_mem_size\NC              \PDF\ memory size      \NC \NR
+\NC largest_used_mark\NC         max referenced marks class        \NC \NR
+\NC filename\NC                  name of the current input file    \NC \NR
+\NC inputid\NC                   numeric id of the current input    \NC \NR
+\NC linenumber\NC                location in the current input file\NC \NR
+\NC lasterrorstring\NC           last error string\NC \NR
+\NC luabytecodes\NC              number of active \LUA\ bytecode registers\NC \NR
+\NC luabytecode_bytes\NC         number of bytes in \LUA\ bytecode registers\NC \NR
+\NC luastates\NC                 number of active \LUA\ interpreters\NC \NR
+\NC luastate_bytes\NC            number of bytes in use by \LUA\ interpreters\NC \NR
+\NC output_active\NC             \type{true} if the \tex{output} routine is active\NC \NR
+\stoptabulate
+
+\section{The \luatex{texconfig} table}
+
+This is a table that is created empty. A startup \LUA\ script could
+fill this table with a number of settings that are read out by
+the executable after loading and executing the startup file.
+
+\starttabulate[|lT|l|l|p|]
+\NC \ssbf key      \NC \bf type     \NC \bf default \NC \bf explanation \NC\NR
+\NC string_vacancies \NC   number\NC  75000\NC cf.\ web2c docs \NC \NR
+\NC pool_free \NC 	        number\NC  5000\NC cf.\ web2c docs \NC \NR
+\NC max_strings \NC        number\NC  15000\NC cf.\ web2c docs \NC \NR
+\NC strings_free \NC       number\NC  100\NC cf.\ web2c docs \NC \NR
+\NC nest_size \NC 	        number\NC  50\NC cf.\ web2c docs \NC \NR
+\NC max_in_open \NC        number\NC  15\NC cf.\ web2c docs \NC \NR
+\NC param_size \NC         number\NC  60\NC cf.\ web2c docs \NC \NR
+\NC save_size \NC 	        number\NC  4000\NC cf.\ web2c docs \NC \NR
+\NC stack_size \NC         number\NC  300\NC cf.\ web2c docs \NC \NR
+\NC dvi_buf_size \NC       number\NC  16384\NC cf.\ web2c docs \NC \NR
+\NC error_line \NC         number\NC  79\NC cf.\ web2c docs \NC \NR
+\NC half_error_line \NC    number\NC  50\NC cf.\ web2c docs \NC \NR
+\NC max_print_line \NC     number\NC  79\NC cf.\ web2c docs \NC \NR
+\NC ocp_list_size \NC      number\NC 1000\NC cf.\ web2c docs \NC \NR
+\NC ocp_buf_size \NC       number\NC 1000\NC cf.\ web2c docs \NC \NR
+\NC ocp_stack_size \NC     number\NC 1000\NC cf.\ web2c docs \NC \NR
+\NC hash_extra \NC         number\NC  0\NC cf.\ web2c docs \NC \NR
+\NC pk_dpi \NC             number\NC  72\NC cf.\ web2c docs \NC \NR
+\NC kpse_init \NC boolean \NC true    \NC \type{false} totally disables \KPATHSEA\ initialisation
+                                          (only ever unset this if you implement {\it all\/} file
+                                          find callbacks!)\NC \NR
+\NC trace_file_names \NC boolean \NC true \NC \type{false} disables \TEX's normal file open|-|close
+                                              feedback (the assumption is that callbacks will take care of
+	                                      that) \NC \NR
+\NC src_special_auto  \NC boolean \NC false \NC source specials sub|-|item \NC \NR
+\NC src_special_everypar  \NC boolean \NC false \NC source specials sub|-|item \NC \NR
+\NC src_special_everyparend  \NC boolean \NC false \NC source specials sub|-|item \NC \NR
+\NC src_special_everycr  \NC boolean \NC false \NC source specials sub|-|item \NC \NR
+\NC src_special_everymath  \NC boolean \NC false \NC source specials sub|-|item \NC \NR
+\NC src_special_everyhbox  \NC boolean \NC false \NC source specials sub|-|item \NC \NR
+\NC src_special_everyvbox  \NC boolean \NC false \NC source specials sub|-|item \NC \NR
+\NC src_special_everydisplay  \NC boolean \NC false \NC source specials sub|-|item \NC \NR
+\NC file_line_error  \NC boolean \NC false \NC do \type{file:line} style error messages\NC \NR
+\NC halt_on_error    \NC boolean \NC false \NC abort run on the first encountered error\NC \NR
+\NC formatname       \NC string \NC \NC if no format name was given
+                                             on the commandline, this key will be tested first
+                                             instead of simply quitting\NC \NR
+\NC jobname          \NC string \NC \NC if no input file name was given
+                                           on the commandline, this key will be tested first
+                                           instead of simply giving up\NC \NR
+\stoptabulate
+
+\section{The \luatex{font} library}
+
+The font library provides the interface into the internals of the font
+system, and also it contains helper functions to load traditional
+\TEX\ font metrics formats. Other font loading functionality is
+provided by the \luatex{fontforge} library that will be discussed in
+the next section.
+
+\subsection{Loading a \TFM\ file}
+
+\startfunctioncall
+table fnt = font.read_tfm(string name, number s)
+\stopfunctioncall
+
+The number is a bit special:
+
+\startitemize
+\item if it is positive, it specifies an \quote{at size} in scaled points.
+\item if it is negative, its absolute value represents a \quote{scaled}
+setting relative to the designsize of the font.
+\stopitemize
+
+The internal structure of the metrics font table that is returned is
+explained in \in{chapter}[fonts].
+
+\subsection{Loading a \VF\ file}
+
+\startfunctioncall
+table vf_fnt = font.read_vf(string name, number s)
+\stopfunctioncall
+
+The meaning of the number \type{s}, and the format of the returned
+table is similar to the one returned by the \luatex{read_tfm()} function.
+
+\subsection{The fonts array}
+
+The whole table of \TEX\ fonts is accessible from lua using a virtual array.
+
+\starttyping
+font.fonts[n] = { ... }
+table f = font.fonts[n]
+\stoptyping
+
+See \in{chapter}[fonts] for the structure of the tables. Because this
+is a virtual array, you cannot call \type{pairs} on it, but see below
+for the \type{font.each} iterator.
+
+The two metatable functions implementing the virtual array are:
+
+\startfunctioncall
+table f = font.getfont(number n)
+font.setfont(number n, table f)
+\stopfunctioncall
+
+Also note the following: assignments can only be made to fonts that
+have already been defined in \TEX, but have not been accessed {\it at
+all\/} since that definition. This limits the usability of the write
+access to \type{font.fonts} quite a lot, a less stringent ruleset will
+likely be implemented later.
+
+\subsection{Checking a font's status}
+
+You can test for the status of a font by calling this function:
+
+\startfunctioncall
+boolean f = font.frozen(number n)
+\stopfunctioncall
+
+The return value is one of true (unassignable), false (can be changed)
+or nil (not a valid font at all).
+
+\subsection{Defining a font directly}
+
+You can define your own font into \luatex{font.fonts} by calling this function:
+
+\startfunctioncall
+number i = font.define(table f)
+\stopfunctioncall
+
+The return value is the internal id number of the defined font (the
+index into \luatex{font.fonts}). If the font creation fails, an error is
+raised. The table is a font structure, as explained in
+\in{chapter}[fonts].
+
+\subsection{Projected next font id}
+
+\startfunctioncall
+number i = font.nextid();
+\stopfunctioncall
+
+This returns the font id number that would be returned by a
+\type{font.define} call if it was executed at this spot in the code
+flow. This is useful for virtual fonts that need to reference
+themselves.
+
+
+
+\subsection{Currently active font}
+
+\startfunctioncall
+number i = font.current();
+font.current(number i);
+\stopfunctioncall
+
+This gets or sets the currently used font number.
+
+\subsection{Maximum font id}
+
+\startfunctioncall
+number i = font.max();
+\stopfunctioncall
+
+This is the largest used index in \type{font.fonts}.
+
+\subsection{Iterating over all fonts}
+
+\startfunctioncall
+for i,v in font.each() do
+  ...
+end
+\stopfunctioncall
+
+This is an iterator over each of the defined \TEX\ fonts. The first
+returned value is the index in \type{font.fonts}, the second the font
+itself, as a lua table. The indices are listed incrementally, but they
+do not always form an array of consecutive numbers: in some cases
+there can be holes in the sequence.
+
+\section{The \luatex{fontforge} library}
+
+\subsection{Getting quick information on a font}
+
+\startfunctioncall
+local info = fontforge.info('filename')
+\stopfunctioncall
+
+This function returns either \type{nil}, or a \type{table}, or an
+array of small tables (in the case of a TrueType collection). The
+returned table(s) will contain six fairly interesting information
+items from the font(s) defined by the file:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key                      \NC \bf type \NC \bf explanation \NC\NR
+\NC fontname                     \NC string   \NC the \quote{PostScript} name of the font\NC\NR
+\NC fullname                     \NC string   \NC The formal name of the font\NC\NR
+\NC familyname                   \NC string   \NC The family name this font belongs to\NC\NR
+\NC weight                       \NC string   \NC A string indicating the color value of the font\NC\NR
+\NC version                      \NC string   \NC The internal font version\NC\NR
+\NC italicangle                  \NC float    \NC The slant angle\NC\NR
+\stoptabulate
+
+Getting information through this function is (sometimes much) more
+efficient than loading the font properly, and is therefore handy when
+you want to create a dictionary of available fonts based on a
+directory contents.
+
+\subsection{Loading an \OPENTYPE\ or \TRUETYPE\ file}
+
+If you want to use an \OPENTYPE\ font, you have to get the metric
+information from somewhere. Using the \type{fontforge} library, the
+basic way to get that information is thus:
+
+
+\starttyping
+function load_font (filename)
+  local metrics = nil
+  local font = fontforge.open(filename)
+  if font then 
+     metrics = fontforge.to_table(font)
+     fontforge.close(font)
+  end
+  return metrics 
+end
+
+myfont = load_font('/opt/tex/texmf/fonts/data/arial.ttf')
+\stoptyping
+
+The main function call is
+
+\startfunctioncall
+f, w = fontforge.open('filename')
+\stopfunctioncall
+
+The first return value is a table representation of the font. The
+second return value is a table containing any warnings and errors
+reported by fontforge while opening the font. In normal typesetting,
+you would probably ignore the second argument, but it can be useful
+for debugging purposes.
+
+For \TRUETYPE\ collections (when filename ends in 'ttc'), you have to
+use a second string argument to specify which font you want from the
+collection.  Use one of the \type{fullname} strings that are returned
+by \type{fontforge.info} for that.
+
+\startfunctioncall
+f, w = fontforge.open('filename','fullname')
+\stopfunctioncall
+
+
+The font file is parsed and partially interpreted by the font
+loading routines from \FONTFORGE. The file format can be \OPENTYPE,
+\TRUETYPE, \TRUETYPE\ Collection, \CFF, or \TYPEONE.
+
+There are a few advantages to this approach compared to reading the
+actual font file ourselves:
+
+\startitemize
+
+\item The font is automatically re|-|encoded, so that the \type{metrics}
+   table for \TRUETYPE\ and \OPENTYPE\ fonts is using \UNICODE\ for
+   the character indices.
+
+\item Many features are pre|-|processed into a format that is easier to handle
+   than just the bare tables would be.
+
+\item \POSTSCRIPT|-|based \OPENTYPE\ fonts do not store the character height and
+  depth in the font file, so the character boundingbox has to be
+  calculated in some way.
+
+\item In the future, it may be interesting to allow \LUA\ scripts access to
+  the font program itself, perhaps even creating or changing the font.
+
+\stopitemize
+
+\subsection{Applying a \quote{feature file}}
+
+You can apply a \quote{feature file} to a loaded font:
+
+\startfunctioncall
+fontforge.apply_featurefile(f,'filename')
+\stopfunctioncall
+
+A \quote{feature file} is a textual representation of the features in an
+OpenType font.  See
+\hyphenatedurl{http://www.adobe.com/devnet/opentype/afdko/topic_feature_file_syntax.html}
+and 
+\hyphenatedurl{http://fontforge.sourceforge.net/featurefile.html}
+for a more detailed description of feature files.
+
+
+\subsection{Applying an \quote{afm file}}
+
+You can apply an \quote{afm file} to a loaded font:
+
+\startfunctioncall
+fontforge.apply_afmfile(f,'filename')
+\stopfunctioncall
+
+An \quote{afm file} is a textual representation of (some of) the metainformation
+in a Type~1 font. See \hyphenatedurl{http://www.adobe.com/devnet/font/pdfs/5004.AFM_Spec.pdf}
+for more information about afm files.
+
+Note: if you \type{fontforge.open()} a PFB file named \type{font.pfb},
+the library will automatically search for and apply \type{font.afm},
+if it exists in the same directory as \type{font.pfb}. In that case,
+there is no need for an explicit call to \type{apply_afmfile()}.
+
+
+\section{Fontforge font tables}
+
+The top|-|level keys in the returned table are (the explanations in
+this part of the documentation are not yet finished):
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key                      \NC \bf type \NC \bf explanation \NC\NR
+\NC table_version                \NC number   \NC indicates the metrics version\NC\NR
+\NC fontname                     \NC string   \NC \POSTSCRIPT\ font name\NC\NR
+\NC fullname                     \NC string   \NC official font name\NC\NR
+\NC familyname                   \NC string   \NC family name\NC\NR
+\NC weight                       \NC string   \NC weight indicator\NC\NR
+\NC copyright                    \NC string   \NC copyright information\NC\NR
+\NC filename                     \NC string   \NC the file name\NC\NR
+%\NC defbasefilename              \NC string   \NC \NC\NR
+\NC version                      \NC string   \NC font version\NC\NR
+\NC italicangle                  \NC float    \NC slant angle\NC\NR
+\NC units_per_em                 \NC number   \NC 1000 for \POSTSCRIPT-based fonts, usually 2048 for \TRUETYPE\NC\NR
+\NC ascent                       \NC number   \NC height of ascender in \type{units_per_em}\NC\NR
+\NC descent                      \NC number   \NC depth of descender in \type{units_per_em}\NC\NR
+\NC upos                         \NC float    \NC \NC\NR
+\NC uwidth                       \NC float    \NC \NC\NR
+\NC vertical_origin              \NC number   \NC \NC\NR
+\NC uniqueid                     \NC number   \NC \NC\NR
+\NC glyphcnt                     \NC number   \NC number of included glyphs\NC\NR
+\NC glyphs                       \NC array    \NC \NC\NR
+\NC glyphmax                     \NC number   \NC maximum used index the glyphs array\NC\NR
+%\NC changed                      \NC number   \NC \NC\NR
+\NC hasvmetrics                  \NC number   \NC \NC\NR
+\NC order2                       \NC number   \NC set to 1 for \TRUETYPE\ splines, 0 otherwise\NC\NR
+\NC strokedfont                  \NC number   \NC \NC\NR
+\NC weight_width_slope_only      \NC number   \NC \NC\NR
+\NC head_optimized_for_cleartype \NC number   \NC \NC\NR
+\NC uni_interp                   \NC enum     \NC \type {unset}, \type {none}, \type {adobe},
+                                                    \type {greek}, \type {japanese}, \type {trad_chinese},
+                                                    \type {simp_chinese}, \type {korean}, \type {ams}\NC\NR
+\NC origname                     \NC string   \NC the file name, as supplied by the user\NC\NR
+\NC map                          \NC table    \NC \NC\NR
+\NC private                      \NC table    \NC \NC\NR
+\NC xuid                         \NC string   \NC \NC\NR
+\NC pfminfo                      \NC table    \NC \NC\NR
+\NC names                        \NC table    \NC \NC\NR
+\NC cidinfo                      \NC table    \NC \NC\NR
+\NC subfonts                     \NC array    \NC \NC\NR
+\NC cidmaster                    \NC array    \NC \NC\NR
+\NC commments                    \NC string   \NC \NC\NR
+\NC anchor_classes               \NC table    \NC \NC\NR
+\NC ttf_tables                   \NC table    \NC \NC\NR
+\NC kerns                        \NC table    \NC \NC\NR
+\NC vkerns                       \NC table    \NC \NC\NR
+\NC texdata                      \NC table    \NC \NC\NR
+\NC lookups                       \NC table    \NC \NC\NR
+\NC gpos                          \NC table    \NC \NC\NR
+\NC gsub                          \NC table    \NC \NC\NR
+\NC chosenname                   \NC string   \NC \NC\NR
+\NC macstyle                     \NC number   \NC \NC\NR
+\NC fondname                     \NC string   \NC \NC\NR
+\NC design_size                  \NC number   \NC \NC\NR
+\NC fontstyle_id                 \NC number   \NC \NC\NR
+\NC fontstyle_name               \NC table    \NC \NC\NR
+\NC design_range_bottom          \NC number   \NC \NC\NR
+\NC design_range_top             \NC number   \NC \NC\NR
+\NC strokewidth                  \NC float    \NC \NC\NR
+\NC mark_classes                 \NC array    \NC \NC\NR
+\NC mark_class_names             \NC array    \NC \NC\NR
+\NC creationtime                 \NC number   \NC \NC\NR
+\NC modificationtime             \NC number   \NC \NC\NR
+\NC os2_version                  \NC number   \NC \NC\NR
+\stoptabulate
+
+\subsubsection{Glyph items}
+
+The \type{glyphs} is an array containing the per|-|character
+information (quite a few of these are only present if nonzero).
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key                      \NC \bf type \NC \bf explanation \NC\NR
+\NC name                         \NC string   \NC the glyph name\NC\NR
+\NC unicode                      \NC number   \NC unicode code point, or -1\NC\NR
+\NC boundingbox                  \NC array    \NC array of four numbers\NC\NR
+\NC width                        \NC number   \NC (only for horizontal fonts)\NC\NR
+\NC vwidth                       \NC number   \NC (only for vertical fonts)\NC\NR
+\NC lsidebearing                 \NC number   \NC (only if nonzero)\NC\NR
+\NC glyph_class                  \NC number   \NC (only if nonzero)\NC\NR
+\NC kerns                        \NC array    \NC (only for horizontal fonts, if set)\NC\NR
+\NC vkerns                       \NC array    \NC (only for vertical fonts, if set)\NC\NR
+\NC dependents                   \NC array    \NC linear array of glyph name strings (only if nonempty)\NC\NR
+\NC lookups                      \NC table    \NC (only if nonempty)\NC\NR
+\NC ligatures                    \NC table    \NC (only if nonempty)\NC\NR
+\NC anchors                      \NC table   \NC (only if set)\NC\NR
+%\NC color                        \NC number   \NC (only if set)\NC\NR
+\NC tex_height                   \NC number   \NC (only if set)\NC\NR
+\NC tex_depth                    \NC number   \NC (only if set)\NC\NR
+\NC tex_sub_pos                  \NC number   \NC (only if set)\NC\NR
+\NC tex_super_pos                \NC number   \NC (only if set)\NC\NR
+\NC comment                      \NC string   \NC (only if set)\NC\NR
+\stoptabulate
+
+The \type{kerns} and \type{vkerns} are linear arrays of small hashes:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key                      \NC \bf type \NC \bf explanation \NC\NR
+\NC char                         \NC string   \NC \NC\NR
+\NC off                          \NC number   \NC \NC\NR
+\NC lookup                       \NC string   \NC \NC\NR
+\stoptabulate
+
+The \type{lookups} is a hash, based on lookup subtable names, with 
+the value of each key inside that a linear array of small hashes:
+
+% TODO: fix this description
+\starttabulate[|lT|l|p|]
+\NC \ssbf key                      \NC \bf type \NC \bf explanation \NC\NR
+\NC type                         \NC enum     \NC \type {position}, \type {pair},  \type {substitution}, \type {alternate},
+                                                  \type {multiple}, \type {ligature}, \type {lcaret},  \type {kerning}, \type {vkerning}, \type {anchors},
+                                                  \type {contextpos}, \type {contextsub}, \type {chainpos}, \type {chainsub},
+                                                  \type {reversesub}, \type {max}, \type {kernback}, \type {vkernback} \NC\NR
+\NC specification                 \NC table   \NC extra data \NC\NR
+\stoptabulate
+
+For the first seven values of \type{type}, there can be additional
+sub|-|information, stored in the sub-table \type{specification}:
+
+\starttabulate[|lT|l|l|p|]
+\NC \bf value    \NC \bf type \NC \bf explanation \NC\NR
+\NC position     \NC table    \NC a table of the \type {offset_specs} type\NC\NR
+\NC pair         \NC table    \NC one string: \type {paired}, and an array of one or 
+                                  two \type {offset_specs} tables:  \type{offsets}\NC\NR
+\NC substitution \NC table    \NC one string: \type {variant}\NC\NR
+\NC alternate    \NC table    \NC one string: \type {components}\NC\NR
+\NC multiple     \NC table    \NC one string: \type {components}\NC\NR
+\NC ligature     \NC table    \NC two strings: \type {components}, \type {char}\NC\NR
+\NC lcaret       \NC array    \NC linear array of numbers\NC\NR
+\stoptabulate
+
+Tables for \type{offset_specs} contain up to four number|-|valued
+fields: \type{x} (a horizontal offset), \type{y} (a vertical offset),
+\type{h} (an advance width correction) and \type{v} (an advance height
+correction).
+
+The \type{ligatures} is a linear array of small hashes:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC lig                \NC table    \NC uses the same substructure as a single \type{possub} item\NC\NR
+\NC char               \NC string   \NC \NC\NR
+\NC components         \NC array    \NC linear array of named components\NC\NR
+\NC ccnt               \NC number   \NC \NC\NR
+\stoptabulate
+
+The \type{anchor} table is indexed by a string signifying the 
+anchor type, which is one of 
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC mark              \NC table   \NC placement mark\NR
+\NC basechar          \NC table   \NC mark for attaching combining items to a base char\NR
+\NC baselig           \NC table   \NC mark for attaching combining items to a ligature\NR
+\NC basemark          \NC table   \NC generic mark for attaching combining items to connect to\NR
+\NC centry            \NC table   \NC cursive entry point\NR
+\NC cexit             \NC table   \NC cursive exit point\NR
+\stoptabulate
+
+The content of these is an short array of defined anchors, with the
+entry keys being the anchor names. For all except \type{baselig}, the
+value is a single table with this definition:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC x                  \NC number   \NC x location\NC\NR
+\NC y                  \NC number   \NC y location\NC\NR
+\NC ttf_pt_index       \NC number   \NC truetype point index, only if given\NC\NR
+\stoptabulate
+
+For \type{baselig}, the value is a small array of such anchor sets
+sets, one for each constituent item of the ligature.
+
+For clarification, an anchor table could for example look like this :
+\starttyping
+  ['anchor']={
+    ['basemark']={
+     ['Anchor-7']={ ['x']=170, ['y']=1080 }
+    },
+    ['mark']={
+     ['Anchor-1'] ={ ['x']=160, ['y']=810 },
+     ['Anchor-4']= { ['x']=160, ['y']=800 }
+    },
+    ['baselig']={
+     [1] = { ['Anchor-2'] ={ ['x']=160, ['y']=650 } }, 
+     [2] = { ['Anchor-2']= { ['x']=460, ['y']=640 } }
+    }
+   },
+\stoptyping
+
+
+
+\subsubsection{map table}
+
+The top|-|level map is a list of encoding mappings. Each of those is a table itself.
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC enccount           \NC number   \NC \NC\NR
+\NC encmax             \NC number   \NC \NC\NR
+\NC backmax            \NC number   \NC \NC\NR
+\NC remap              \NC table    \NC \NC\NR
+\NC map                \NC array    \NC non|-|linear array of mappings\NC\NR
+\NC backmap            \NC array    \NC non|-|linear array of backward mappings\NC\NR
+\NC enc                \NC table    \NC \NC\NR
+\stoptabulate
+
+The \type{remap} table is very small:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC firstenc           \NC number   \NC \NC\NR
+\NC lastenc            \NC number   \NC \NC\NR
+\NC infont             \NC number   \NC \NC\NR
+\stoptabulate
+
+The \type{enc} table is a bit more verbose:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC enc_name           \NC string   \NC \NC\NR
+\NC char_cnt           \NC number   \NC \NC\NR
+\NC char_max           \NC number   \NC \NC\NR
+\NC unicode            \NC array    \NC of \UNICODE\ position numbers\NC\NR
+\NC psnames            \NC array    \NC of \POSTSCRIPT\ glyph names\NC\NR
+\NC builtin            \NC number   \NC \NC\NR
+\NC hidden             \NC number   \NC \NC\NR
+\NC only_1byte         \NC number   \NC \NC\NR
+\NC has_1byte          \NC number   \NC \NC\NR
+\NC has_2byte          \NC number   \NC \NC\NR
+\NC is_unicodebmp      \NC number   \NC (only if nonzero)\NC\NR
+\NC is_unicodefull     \NC number   \NC (only if nonzero)\NC\NR
+\NC is_custom          \NC number   \NC (only if nonzero)\NC\NR
+\NC is_original        \NC number   \NC (only if nonzero)\NC\NR
+\NC is_compact         \NC number   \NC (only if nonzero)\NC\NR
+\NC is_japanese        \NC number   \NC (only if nonzero)\NC\NR
+\NC is_korean          \NC number   \NC (only if nonzero)\NC\NR
+\NC is_tradchinese     \NC number   \NC (only if nonzero)\NC\NR
+\NC is_simplechinese   \NC number   \NC (only if nonzero)\NC\NR
+\NC low_page           \NC number   \NC \NC\NR
+\NC high_page          \NC number   \NC \NC\NR
+\NC iconv_name         \NC string   \NC \NC\NR
+\NC iso_2022_escape    \NC string   \NC \NC\NR
+\stoptabulate
+
+\subsubsection{private table}
+
+This is the font's private \POSTSCRIPT\ dictionary, if any. Keys and
+values are both strings.
+
+\subsubsection{cidinfo table}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC registry                  \NC string   \NC \NC\NR
+\NC ordering                  \NC string   \NC \NC\NR
+\NC supplement                \NC number   \NC \NC\NR
+\NC version                   \NC number   \NC \NC\NR
+\stoptabulate
+
+\subsubsection{pfminfo table}
+
+The \type{pfminfo} table contains most of the OS/2 information:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC pfmset             \NC number  \NC \NC\NR
+\NC winascent_add      \NC number  \NC \NC\NR
+\NC windescent_add     \NC number  \NC \NC\NR
+\NC hheadascent_add    \NC number  \NC \NC\NR
+\NC hheaddescent_add   \NC number  \NC \NC\NR
+\NC typoascent_add     \NC number  \NC \NC\NR
+\NC typodescent_add    \NC number  \NC \NC\NR
+\NC subsuper_set       \NC number  \NC \NC\NR
+\NC panose_set         \NC number  \NC \NC\NR
+\NC hheadset           \NC number  \NC \NC\NR
+\NC vheadset           \NC number  \NC \NC\NR
+\NC pfmfamily          \NC number  \NC \NC\NR
+\NC weight             \NC number  \NC \NC\NR
+\NC width              \NC number  \NC \NC\NR
+\NC avgwidth           \NC number  \NC \NC\NR
+\NC firstchar          \NC number  \NC \NC\NR
+\NC lastchar           \NC number  \NC \NC\NR
+\NC fstype             \NC number  \NC \NC\NR
+\NC linegap            \NC number  \NC \NC\NR
+\NC vlinegap           \NC number  \NC \NC\NR
+\NC hhead_ascent       \NC number  \NC \NC\NR
+\NC hhead_descent      \NC number  \NC \NC\NR
+\NC hhead_descent      \NC number  \NC \NC\NR
+\NC os2_typoascent     \NC number  \NC \NC\NR
+\NC os2_typodescent    \NC number  \NC \NC\NR
+\NC os2_typolinegap    \NC number  \NC \NC\NR
+\NC os2_winascent      \NC number  \NC \NC\NR
+\NC os2_windescent     \NC number  \NC \NC\NR
+\NC os2_subxsize       \NC number  \NC \NC\NR
+\NC os2_subysize       \NC number  \NC \NC\NR
+\NC os2_subxoff        \NC number  \NC \NC\NR
+\NC os2_subyoff        \NC number  \NC \NC\NR
+\NC os2_supxsize       \NC number  \NC \NC\NR
+\NC os2_supysize       \NC number  \NC \NC\NR
+\NC os2_supxoff        \NC number  \NC \NC\NR
+\NC os2_supyoff        \NC number  \NC \NC\NR
+\NC os2_strikeysize    \NC number  \NC \NC\NR
+\NC os2_strikeypos     \NC number  \NC \NC\NR
+\NC os2_family_class   \NC number  \NC \NC\NR
+\NC os2_xheight        \NC number  \NC \NC\NR
+\NC os2_capheight      \NC number  \NC \NC\NR
+\NC os2_defaultchar    \NC number  \NC \NC\NR
+\NC os2_breakchar      \NC number  \NC \NC\NR
+\NC os2_vendor         \NC string  \NC \NC\NR
+\NC panose             \NC table  \NC \NC\NR
+\stoptabulate
+
+The \type{panose} subtable has exactly 10 string keys:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC familytype             \NC string   \NC Values as in the \OPENTYPE\ font specification:
+                                        \type {Any}, \type {No Fit}, \type {Text and Display}, \type {Script},
+                                        \type {Decorative}, \type {Pictorial} \NC\NR
+\NC serifstyle             \NC string   \NC See the \OPENTYPE\ font specification for values\NC\NR
+\NC weight                 \NC string   \NC id. \NC\NR
+\NC proportion             \NC string   \NC id. \NC\NR
+\NC contrast               \NC string   \NC id. \NC\NR
+\NC strokevariation        \NC string   \NC id. \NC\NR
+\NC armstyle               \NC string   \NC id. \NC\NR
+\NC letterform             \NC string   \NC id. \NC\NR
+\NC midline                \NC string   \NC id. \NC\NR
+\NC xheight                \NC string   \NC id. \NC\NR
+\stoptabulate
+
+\subsubsection{names table}
+
+Each item has two top|-|level keys:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key         \NC \bf type \NC \bf explanation \NC\NR
+\NC lang                   \NC string   \NC language for this entry \NC\NR
+\NC names                  \NC table    \NC \NC\NR
+\stoptabulate
+
+The \type{names} keys are the actual \TRUETYPE\ name strings. The
+possible keys are:
+
+\starttabulate[|lT|p|]
+\NC \ssbf key           \NC \bf explanation \NC\NR
+\NC copyright   \NC \NC\NR
+\NC family   \NC \NC\NR
+\NC subfamily   \NC \NC\NR
+\NC uniqueid   \NC \NC\NR
+\NC fullname   \NC \NC\NR
+\NC version   \NC \NC\NR
+\NC postscriptname   \NC \NC\NR
+\NC trademark   \NC \NC\NR
+\NC manufacturer   \NC \NC\NR
+\NC designer   \NC \NC\NR
+\NC descriptor   \NC \NC\NR
+\NC venderurl   \NC \NC\NR
+\NC designerurl   \NC \NC\NR
+\NC license   \NC \NC\NR
+\NC licenseurl   \NC \NC\NR
+\NC idontknow   \NC \NC\NR
+\NC preffamilyname   \NC \NC\NR
+\NC prefmodifiers   \NC \NC\NR
+\NC compatfull   \NC \NC\NR
+\NC sampletext   \NC \NC\NR
+\NC cidfindfontname   \NC \NC\NR
+\stoptabulate
+
+\subsubsection{anchor_classes table}
+
+The anchor_classes classes:
+ 
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC name                   \NC string   \NC A descriptive id of this anchor class\NC\NR
+\NC lookup                 \NC string   \NC \NC\NR
+\NC type                   \NC string   \NC One of 'mark', 'mkmk', 'curs', 'mklg' \NC\NR
+\stoptabulate
+% type is actually a lookup subtype, not a feature name. officiallu, these strings
+% should be gpos_mark2mark etc.
+
+\subsubsection{gpos table}
+
+Th gpos table has one array entry for each lookup.
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC type                  \NC string   \NC One of  
+  'gpos_single', 'gpos_pair', 'gpos_cursive', 
+  'gpos_mark2base', 'gpos_mark2ligature', 'gpos_mark2mark',  'gpos_context', 
+  'gpos_contextchain' % ,  'kern_statemachine' 
+\NC\NR
+\NC flags                 \NC table  \NC \NC\NR
+\NC name                  \NC string   \NC \NC\NR
+\NC features              \NC array   \NC \NC\NR
+\NC subtables             \NC array   \NC \NC\NR
+\stoptabulate
+
+The flags table has a true value for each of the lookup flags that is
+actually set:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC r2l                    \NC boolean   \NC \NC\NR
+\NC ignorebaseglyphs       \NC boolean    \NC \NC\NR
+\NC ignoreligatures        \NC boolean    \NC \NC\NR
+\NC ignorecombiningmarks   \NC boolean    \NC \NC\NR
+\stoptabulate
+
+
+
+The features table has:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC tag                    \NC string   \NC \NC\NR
+\NC scripts                \NC table    \NC \NC\NR
+\NC ismax                  \NC number   \NC (only if true)\NC\NR
+\stoptabulate
+
+The scripts table within features has:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC script	               \NC string          \NC \NC\NR
+\NC langs                  \NC array of strings \NC \NC\NR
+\stoptabulate
+
+
+
+The subtables table has:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC name                    \NC string   \NC \NC\NR
+\NC suffix                  \NC string   \NC (only if used)\NC\NR % used by gpos_single to get a default
+\NC anchor_classes          \NC number   \NC (only if used)\NC\NR
+\NC vertical_kerning        \NC number   \NC (only if used)\NC\NR
+\NC kernclass               \NC table    \NC (only if used)\NC\NR
+\stoptabulate
+
+
+The kernclass with subtables table has:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+%\NC first_cnt             \NC number   \NC \NC\NR
+%\NC second_cnt            \NC number   \NC \NC\NR
+\NC firsts                \NC array of strings  \NC \NC\NR
+\NC seconds               \NC array of strings   \NC \NC\NR
+\NC lookup                \NC string \NC associated lookup \NC \NR
+\NC offsets               \NC array of numbers  \NC \NC\NR
+%\NC kcid                 \NC number   \NC ? \NC\NR
+\stoptabulate
+
+\subsubsection{gsub table}
+
+This has identical layout to the \type{gpos} table, except for the
+type:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC type                  \NC string   \NC One of  'gsub_single', 'gsub_multiple', 'gsub_alternate', 
+  'gsub_ligature', 'gsub_context',  'gsub_contextchain', 'gsub_reversecontextchain' 
+\NC\NR
+\stoptabulate
+
+
+
+\subsubsection{ttf_tables table}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC tag                    \NC string   \NC \NC\NR
+\NC len                    \NC number   \NC \NC\NR
+\NC maxlen                 \NC number   \NC \NC\NR
+\NC data                   \NC number   \NC \NC\NR
+\stoptabulate
+
+\subsubsection{kerns table}
+
+Substructure is identical to the per|-|glyph subtable.
+
+\subsubsection{vkerns table}
+
+Substructure is identical to the per|-|glyph subtable.
+
+\subsubsection{texdata table}
+
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC type                   \NC string   \NC \type {unset}, \type {text}, \type {math}, \type {mathext}\NC\NR
+\NC params                 \NC array    \NC 22 font numeric parameters\NC\NR
+\stoptabulate
+
+\subsubsection{lookups table}
+
+Top|-|level \type{lookups} is quite different from the ones at
+character level. The keys in this hash are strings, the values the
+actual lookups, represented as dictionary tables.
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC type                   \NC number   \NC \NC\NR
+\NC format                 \NC enum     \NC One of 'glyphs', 'class', 'coverage', 'reversecoverage' \NC\NR
+\NC tag                    \NC string   \NC \NC\NR
+\NC current_class          \NC array   \NC \NC\NR
+\NC before_class           \NC array   \NC \NC\NR
+\NC after_class            \NC array   \NC \NC\NR
+\NC rules                  \NC array   \NC an array of rule items\NC\NR
+\stoptabulate
+
+Rule items have one common item and one specialized item:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC lookups                \NC array    \NC A linear array of lookup names\NC\NR
+\NC glyph                  \NC array     \NC Only if the parent's format is \quote{glyph}\NC\NR
+\NC class                  \NC array     \NC Only if the parent's format is \quote{glyph}\NC\NR
+\NC coverage               \NC array     \NC Only if the parent's format is \quote{glyph}\NC\NR
+\NC reversecoverage        \NC array     \NC Only if the parent's format is \quote{glyph}\NC\NR
+\stoptabulate
+ 
+A glyph table is:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC names                  \NC string   \NC \NC\NR
+\NC back                   \NC string   \NC \NC\NR
+\NC fore                   \NC string   \NC \NC\NR
+\stoptabulate
+
+
+
+A class table is:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC current              \NC array    \NC of numbers \NC\NR
+\NC before               \NC array    \NC of numbers  \NC\NR
+\NC after                \NC array    \NC of numbers  \NC\NR
+\stoptabulate
+
+coverage:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC current                \NC array    \NC of strings \NC\NR
+\NC before                 \NC array    \NC of strings\NC\NR
+\NC after                  \NC array    \NC of strings \NC\NR
+\stoptabulate
+
+reversecoverage:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC current                \NC array    \NC of strings \NC\NR
+\NC before                 \NC array    \NC of strings\NC\NR
+\NC after                  \NC array    \NC of strings \NC\NR
+\NC replacements           \NC string   \NC \NC\NR
+\stoptabulate
+
+\section{The \luatex{lang} library}
+
+This library provides the interface to \LUATEX's structure
+representing a language, and the associated functions.
+
+\startfunctioncall
+<language> l = lang.new()
+<language> l = lang.new(number id)
+\stopfunctioncall
+
+This function creates a new userdata object. An object of type
+\type{<language>} is the first argument to most of the other functions
+in the \luatex{lang} library. These functions can also be used as if
+they were object methods, using the colon syntax.
+
+Without an argument, the next available internal id number will be
+assigned to this object. With argument, an object will be created that
+links to the internal language with that id number.
+
+\startfunctioncall
+number n = lang.id(<language> l)
+\stopfunctioncall
+
+returns the internal \tex{language} id number this object refers to.
+
+\startfunctioncall
+string n = lang.hyphenation(<language> l)
+lang.hyphenation(<language> l, string n)
+\stopfunctioncall
+
+Either returns the current hyphenation exceptions for this language,
+or adds new ones. The syntax of the string is explained in the next
+chapter,~\in{section}[patternsexceptions].
+
+\startfunctioncall
+lang.clear_hyphenation(<language> l)
+\stopfunctioncall
+
+Clears the exception dictionary for this language.
+
+\startfunctioncall
+string n = lang.clean(string o)
+\stopfunctioncall
+
+Creates a hypenation key from the supplied hyphenation value. The
+syntax of the argument string is explained in the next
+chapter,~\in{section}[patternsexceptions]. This function is useful if
+you want to do something else based on the words in a dictionary file,
+like spell-checking.
+
+\startfunctioncall
+string n = lang.patterns(<language> l)
+lang.patterns(<language> l, string n)
+\stopfunctioncall
+
+Adds additional patterns for this language object, or returns the
+current set. The syntax of this string is explained in the next
+chapter,~\in{section}[patternsexceptions].
+
+\startfunctioncall
+lang.clear_patterns(<language> l)
+\stopfunctioncall
+
+Clears the pattern dictionary for this language.
+
+\startfunctioncall
+number n = lang.prehyphenchar(<language> l)
+lang.prehyphenchar(<language> l, number n)
+\stopfunctioncall
+
+Gets or sets the \quote{pre-break} hyphen character for this font
+(initially the hyphen, decimal 45).
+
+\startfunctioncall
+number n = lang.posthyphenchar(<language> l)
+lang.posthyphenchar(<language> l, number n)
+\stopfunctioncall
+
+Gets or sets the \quote{post-break} hyphen character for this font
+(initially null, decimal 0).
+
+
+\startfunctioncall
+boolean success = lang.hyphenate(<node> head)
+boolean success = lang.hyphenate(<node> head, <node> tail)
+\stopfunctioncall
+
+Inserts hyphenation points (discretionary nodes) in a node list. If
+\type{tail} is given as argument, processing stops on that node. 
+Currently, \type{succes} is always true if \type{head} (and \type{tail}, if
+specified) are proper nodes, regardless of possible other errors.
+
+\chapter[languages]{Languages and characters, Fonts and glyphs}
+
+\LUATEX's internal handling of the characters and glyphs that eventually 
+become typeset is quite different from the way \TEX82 handles those
+same objects. The easiest way to explain the difference is to focus on
+unrestricted horizontal mode (i.\,e.\ paragraphs) and hyphenation first.
+Later on, it will be easy to deal with the differences that occur in
+horizontal and math modes.
+
+In \TEX82, the characters you type are converted into \type{char_node}
+records when they are encountered by the main control loop. \TEX\
+attaches and processes the font information while creating those
+records, so that the resulting \quote{horizontal list} contains the final
+forms of ligatures and implicit kerning. 
+
+When it becomes necessary to hyphenate words in a paragraph, \TEX\
+converts (one word at time) the \type{char_node} records into a
+string array by replacing ligatures with their components and
+ignoring the kerning. Then it runs the hyphenation algorithm on this
+string, and converts the hyphenated result back into a
+\quote{horizontal list} that is consecutively spliced back into 
+the paragraph stream.
+
+The \type{char_node} records are somewhat misnamed, as they are glyph
+positions in specific fonts, and therefore not really \quote{characters}
+in the linguistic sense. There is no language information inside the
+\type{char_node} records. Instead, language information is passed along 
+using \type{language whatsit} records inside the horizontal list.
+
+In \LUATEX, the situation is quite different. The characters you
+type are always converted into \type{glyph_node} records with a
+special subtype to identify them as being intended as linguistic
+characters. \LUATEX\ stores the needed language information in those
+records, but does not do any font-related processing at the time of
+node creation.
+
+When it becomes necessary to typeset a paragraph, \LUATEX\ first
+inserts all hyphenation points right into the whole node list.
+Next, it processes all the font information in the whole list
+(creating ligatures and adjusting kerning), and finally it adjusts
+all the subtype identifiers so that the records are \quote{glyph
+nodes} from now on.
+
+That was the broad overview. The rest of this chapter will deal with the
+minutiae of the new process.
+
+\section[charsandglyphs]{Characters and glyphs}
+
+\TEX82 (including \PDFTEX) differentiated between \type{char_node}s
+and \type{lig_node}s.  The former are simple items that contained
+nothing but a \quote{character} and a \quote{font} field, and they
+lived in the same memory as tokens did. The latter also contained a
+list of components, and a subtype indicating whether this ligature was
+the result of a word boundary, and it was stored in the same place as
+other nodes like boxes and kerns and glues.
+
+In \LUATEX, these two types are merged into one, somewhat larger
+structure called a \type{glyph_node}. Besides having the old
+character, font, and component fields, and the new special fields like
+\quote{attr} (see~\in{section}[glyphnodes]), these nodes also contain:
+
+\startitemize
+\item A subtype, split into four main types: 
+   \startitemize 
+   \item \quote{character} -- for characters to be hyphenated
+   \item \quote{glyph}  -- for specific font glyphs
+   \item \quote{ligature}  -- for ligatures
+   \item \quote{ghost}  -- for \quote{ghost objects}
+   \stopitemize
+   The latter two make further use of two extra fields:
+   \startitemize 
+   \item \quote{left}  -- for ligatures: created from a left word boundary. 
+                    for ghosts:  created from \tex{leftghost}
+   \item \quote{right} -- for ligatures: created from a right word boundary. 
+                    for ghosts:  created from \tex{rightghost}
+   \stopitemize
+   for ligatures, both bits can be set at the same time (in case of a single-glyph word).
+
+\item \type{glyph_node}s of type \quote{character} also contain language data, 
+  split into four items that were current when the node was created:
+  the \tex{setlanguage} (15 bits), \tex{lefthyphenmin} (8 bits),
+  \tex{righthyphenmin} (8 bits), and \tex{uchyph} (1 bit).
+\stopitemize
+
+Incidentally, \LUATEX\ allows 32768 separate languages, and words can
+be 256 characters long.
+
+Because the \tex{uchyph} value is saved in the actual nodes, its
+handling is subtly different from \TEX82: changes to \tex{uchyph}
+become effective immediately, not at the end of the current partial
+paragraph.
+
+Typeset boxes now always have their language information embedded in
+the nodes themselves, so there is no longer a possible dependancy on
+the surrounding language settings. In \TEX82, a mid-paragraph
+statement like \type{\unhbox0} would process the box using the current
+paragraph language unless there was a \tex{setlanguage} issued inside
+the box. In \LUATEX, all language variables are already frozen.
+
+
+\section{The main control loop}
+
+In \LUATEX's main loop, almost all input characters that are to be
+typeset are converted into \type{glyph_node} records with subtype
+\quote{character}, but there are a few small exceptions.
+
+First, the \tex{accent} primitives creates nodes with subtype \quote{glyph}
+instead of \quote{character}: one for the actual accent and one for the
+accentee. The primary reason for this is that \tex{accent} in \TEX82
+is explicitly dependent on the current font encoding, so it would not
+make much sense to attach a new meaning to the primitive's name, as
+that would invalidate many old documents and macro packages. A
+secondary reason is that in \TEX82, \tex{accent} prohibits hyphenation
+of the current word. Since in \LUATEX\ hyphenation only takes place on
+\quote{character} nodes, it is possible to achieve the same effect.
+
+This change of meaning did happen with \tex{char}, that now generates
+\quote{character} nodes, consistent with its changed meaning in \XETEX.
+The changed status of \tex{char} is not yet finalized, but if it stays
+as it is now, a new primitive \tex{glyph} should be added to directly
+insert a font glyph id.
+
+Second, all the results of processing in math mode eventually become
+nodes with \quote{glyph} subtypes.
+
+Third, the \ALEPH-derived commands \tex{leftghost} and
+\tex{rightghost} create nodes of a third subtype: \quote{ghost}. These nodes
+are ignored completely by all further processing until the stage where
+inter-glyph kerning is added.
+
+Fourth, automatic discretionaries are handled differently. \TEX82
+inserts an empty discretionary after sensing an input character that
+matches the \tex{hyphenchar} in the current font. This test is wrong,
+in our opinion: wether or not hyphenation takes place should not
+depend on the current font, it is a language property.
+
+In \LUATEX, it works like this: if \LUATEX\ senses a string of input
+characters that matches the value of the new integer parameter
+\tex{exhyphenchar}, it will insert an empty discretionary after that
+series of nodes. Initex sets the \type{\exhyphenchar=`\-}. 
+Incidentally, this is a global parameter instead of a
+language-specific one because it may be useful to change the value
+depending on the document structure instead of the text language. 
+
+The exact status and meaning of \tex{hyphenchar} is still under
+consideration, it will probably become used in the character to glyph
+conversion stage. Currently it is simply ignored.
+
+Fifth, \tex{setlanguage} no longer creates whatsits. The meaning of
+\tex{setlanguage} is changed so that it is now an integer parameter 
+like all others. That integer parameter is used in \tex{glyph_node}
+creation to add language information to the glyph nodes. In
+conjunction, the \tex{language} primitive is extended so that it
+always also updates the value of \tex{setlanguage}.
+
+Sixth, the \tex{noboundary} command (this command prohibits word
+boundary processing where that would normally take place) now does
+create whatsits. These whatsits are needed because the exact place of
+the \tex{noboundary} command in the input stream has to be retained
+until after the ligature and font processing stages.
+
+Finally, there is no longer a \type{main_loop} label in the
+code. Remember that \TEX82 did quite a lot of processing while adding
+\type{char_nodes} to the horizontal list? For speed reasons, it handled 
+that processing code outside of the \quote{main control} loop, and only the
+first character of any \quote{word} was handled by that \quote{main control} loop.
+In \LUATEX, there is no longer a need for that (all hard work is done
+later), and the (now very small) bits of character-handling code have
+been moved back inline. When \tex{tracingcommands} is on, this is
+visible because the full word is reported, instead of just the initial
+character.
+
+
+\section[patternsexceptions]{Loading patterns and exceptions}
+
+The hyphenation algorithm in \LUATEX\ is quite different from the one
+in \TEX82, although it uses essentially the same user input.
+
+After expansion, the argument for \tex{patterns} has to be proper
+UTF-8, no \tex{char} or \tex{chardef-ed} commands are allowed. (The
+current implementation is even more strict, and will reject all
+non-unicode characters, but that will be changed in the future. For
+now, the generated errors are a valuable tool in discovering
+font-encoding specific pattern files)
+
+Likewise, the expanded argument for \tex{hyphenation} also has to be
+proper UTF-8, but here a tiny little bit of extra syntax is provided:
+
+\startitemize[n]
+\item three sets of arguments in curly braces (\type{{}{}{}})
+   indicates a desired complex discretionary, with arguments 
+   as in \tex{discretionary}'s command in normal document input.
+\item \type{-} indicates a desired simple discretionary,  cf. \type{\-} and 
+   \type{\discretionary{-}{}{}} in normal document input.
+\item Internal command names are ignored. This rule is provided 
+   especially for \tex{discretionary}, but it also helps to deal with
+  \tex{relax} commands that may sneak in.
+\item \type{=} indicates a hyphen in the document input (but that
+  is only useful in documents where \tex{exhyphenchar} is not equal to
+  the hyphen).
+\stopitemize
+
+The expanded argument is first converted back to a space-separated
+string while dropping the internal command names. This string is then
+converted into a dictionary by a routine that creates key||value pairs
+by converting the other listed items. It is important to note that the
+keys in an exception dictionary can always be generated from the
+values. Here are a few examples:
+
+\starttabulate[|l|l|l|]
+\NC \ssbf value          \NC \ssbf implied key (input) \NC \ssbf effect\NC\NR 
+\NC \type{ta-ble}        \NC table  \NC \type{ta\-ble} 
+                                        ($=$ \type{ta\discretionary{-}{}{}ble})\NC\NR
+\NC \type{ba{k-}{}{c}ken}\NC backen \NC \type{ba\discretionary{k-}{}{c}ken}\NC\NR
+\stoptabulate
+
+The resultant patterns and exception dictionary will be stored under
+the language code that is the present value of \tex{language}. 
+
+In the last line of the table, you see there is no \tex{discretionary}
+command in the value: the command is optional in the \TEX-based input
+syntax. The underlying reason for that is that it is conceivable that
+a whole dictionary of words is stored as a plain text file and loaded
+into \LUATEX\ using one of the functions in the Lua \luatex{lang}
+library. This loading method is quite a bit faster than going through
+the \TEX\ language primitives, but some (most?) of that speed gain
+would be lost if it had to interpret command sequences while doing so.
+
+The motivation behind the \ETEX\ extension \tex{savinghyphcodes} was
+that hyphenation heavily depended on font encodings. This is no longer
+true in \LUATEX, and the corresponding primitive is ignored pending
+complete removal. The future semantics of \tex{uppercase} and
+\tex{lowercase} are still under consideration, no changes have taken
+place yet.
+
+
+\section{Applying hyphenation}
+
+The internal structures \LUATEX\ uses for the insertion of
+discretionaries in words is very different from the ones in \TEX82,
+and that means there are some noticable differences in handling as
+well.
+
+First and foremost, there is no \quote{compressed trie} involved in
+hyphenation. The algorithm still reads \PATGEN-generated pattern
+files, but \LUATEX\ uses a finite state hash to match the patterns
+against the word to be hyphenated. This algorithm is based on the
+\quote{libhnj} library used by OpenOffice. 
+The memory allocation for this new implementation is completely
+dynamic, so the \WEBC\ setting for \type{trie_size} is ignored.
+
+Differences between \LUATEX\ and \TEX82 that are a direct result of that:
+
+\startitemize
+\item \LUATEX\ happily hyphenates the full Unicode character range.
+\item Pattern and exception dictionary size is limited by the
+  available memory only, all allocations are done dynamically.
+  The trie-related settings in \type{texmf.cnf} are ignored.
+\item Because there is no \quote{trie preparation} stage, language patterns 
+  never become frozen. This means that the primitive \tex{patterns}
+  (and its lua counterpart \luatex{lang.patterns}) can be used at any
+  time, not only in initex.
+\item Only the string representation of \tex{patterns} and 
+  \tex{hyphenation} is stored in the format file. At format load time,
+  they are simply re-evaluated. It follows that there is no real 
+  reason to preload languages in the format file. In fact, it is 
+  usually not a good idea to do so. It is much smarter to load 
+  patterns no sooner than the first time they are actually needed.
+\item \LUATEX\ uses the language-specific variables
+\tex{prehyphenchar} and \tex{posthyphenchar} in the creation of 
+discretionaries, instead of \TEX82's \tex{hyphenchar}.
+\stopitemize
+
+Previously, there were problems with changing the node attributes
+mid-word, but that problem is now solved, as nodes in a word are not
+converted to and from a string any more (this was required by the old
+hyphenation code), they are edited in place. Inserted characters and
+ligatures inherit their attributes from the nearest glyph node item
+(usually the preceding one, but the following one for the items
+inserted at the left-hand side of a word).
+
+Word boundaries are no longer implied by font switches, but by
+language switches. One word can have two separate fonts and still be
+hyphenated correctly (but it can not have two different languages,
+the \tex{setlanguage} command forces a word boundary).
+
+All languages start out with \type{\prehyphenchar=`\-} and
+\type{\posthyphenchar=0}. When you assign the values of
+\tex{prehyphenchar} and \tex{posthyphenchar}, you are actually
+changing the settings for the current \tex{language}, this behavior
+is compatible with \tex{patterns} and \tex{hyphenation}.
+
+\LUATEX\ also hyphenates the first word in a paragraph. 
+
+Words can be up to 256 characters long (up from 64 in \TEX82).  Longer
+words generate an error right now, but eventually either the
+limitation will be removed or perhaps it will become possbile to
+silently ignore the excess characters (this is what happens in \TEX82,
+but there the behavior cannot be controlled).
+
+If you are using the Lua function \type{lang.hyphenate}, you should be
+aware that this function expects to receive a list of \quote{character}
+nodes. It will not operate properly in the presence of \quote{glyph},
+\quote{ligature}, or \quote{ghost} nodes, nor does it know how to deal with
+kerning.  In the near future, it will be able to skip over \quote{ghost}
+nodes, and we may add a less fuzzy function you can call as well.
+
+The hyphenation exception dictionary is maintained as key-value
+hash, and that is also dynamic, so the \type{hyph_size} setting is not
+used either.
+
+A technical paper detailing the new algorithm will be released as a
+separate document.
+
+\section{Applying ligatures and kerning}
+
+After all possible hyphenation points have been inserted in the list,
+\LUATEX\ will process the list to convert the \quote{character} nodes into 
+\quote{glyph} and \quote{ligature} nodes. This is actually done in two stages:
+first all ligatures are processed, then all kerning information is
+applied to the result list. But those two stages are somewhat
+dependent on each other: If the used font makes it possible to do so,
+the ligaturing stage adds virtual \quote{character} nodes to the word
+boundaries in the list. While doing so, it removes and interprets
+\type{noboundary} nodes. The kerning stage deletes those word boundary 
+items after it is done with them, and it does the same for \quote{ghost}
+nodes. Finally, at the end of the kerning stage, all remaining
+\quote{character} nodes are converted to \quote{glyph} nodes.
+
+This work separation is worth mentioning because, if you overrule from
+Lua only one of the two callbacks related to font handling, then you
+have to make sure you perform the tasks normally done by \LUATEX\
+itself in order to make sure that the other, non-overrruled, routine
+continues to function properly.
+
+Work in this area is not yet complete, but most of the possible cases
+are handled by our rewritten ligaturing engine. We are working hard to
+make sure all of the possible inputs will become supported soon.
+
+For example, take the word \type{office}, hyphenated \type{of-fice},
+using a \quote{normal} font with all the \type{f}-\type{i} ligatures:
+\starttabulate[|l|l|]
+\NC Initial:               \NC \type{{o}{f}{f}{i}{c}{e}}           \NC\NR
+\NC After hyphenation:     \NC \type{{o}{f}{{-},{},{}}{f}{i}{c}{e}}\NC\NR
+\NC First ligature stage:  \NC \type{{o}{{f}{-},{f},{ff}}{i}{c}{e}}\NC\NR
+\NC Final result:          \NC \type{{o}{{f}{-},{fi},{ffi}}{c}{e}} \NC\NR
+\stoptabulate
+
+That's bad enough, but if there was a hyphenation point between the
+\type{f} and the \type{i}: \type{of-f-ice}, the final result should be: 
+\starttyping
+   {o}{{f}{-},
+       {{f}{-},
+        {i},
+        {fi}},
+       {{ff}{-},
+        {i},
+        {ffi}}}{c}{e}
+\stoptyping
+with discretionaries in the post-break text as well as in the
+replacement text of the top-level discretionary that resulted from the
+first hyphenation point.  And this is only a simple case.
+
+\section{Breaking paragraphs into lines}
+
+This code is still almost unchanged, but because of the
+above-mentioned changes with respect to discretionaries and ligatures,
+line breaking will potentially be different from traditional \TEX.
+The actual line breaking code is still based on the \TEX82 algorithms,
+and it does not expect there to be discretionaries inside of
+discretionaries. 
+
+But that situation is now fairly common in \LUATEX, due to the changes
+to the ligaturing mechanism. And also, the \LUATEX\ discretionary
+nodes are implemented slightly different from the \TEX82 nodes: the
+\type{no_break} text is now embedded inside the disc node, where 
+previously these nodes kept their place in the horizontal list (the
+discretionary node contained a counter indicating how many nodes to
+skip).
+
+The combined effect of these two differences is that \LUATEX\ does not
+always use all of the potential breakpoints in a paragraph, especially
+when fonts with many ligatures are used.
+
+% TODO: 
+%   Check \sfcode handling
+%   Implement \glyph
+%
+%   Remove \savinghyphcodes
+%   Allow non-UCS characters in \patterns
+
+\chapter[fonts]{Font structure}
+
+All \TEX\ fonts are represented to \LUA\ code as tables, and
+internally as C~structures. All keys in the table below are saved in
+the internal font structure if they are present in the table returned
+by the
+\luatex{define_font} callback, or if they result from the normal \TFM|/|\VF\
+reading routines if there is no \luatex{define_font} callback defined.
+
+The column \quote{from \VF} means that this key will be created by the
+\luatex{font.read_vf()} routine, \quote{from \TFM} means that the key will be created
+by the \luatex{font.read_tfm()} routine, and \quote{used} means whether or not the
+\LUATEX\ engine itself will do something with the key.
+
+The top|-|level keys in the table are as follows:
+
+\starttabulate[|l|l|l|l|l|p|]
+\NC \ssbf key            \NC \bf from vf \NC \bf from tfm \NC \bf used\NC \bf value type \NC \bf description \NC\NR
+\NC name               \NC yes      \NC yes      \NC yes \NC string \NC metric (file) name\NC\NR
+\NC area               \NC no       \NC yes      \NC yes \NC string \NC (directory) location, typically empty\NC\NR
+\NC used               \NC no       \NC yes      \NC yes \NC boolean\NC used already? (initial: false)\NC \NR
+\NC characters         \NC yes      \NC yes      \NC yes \NC table  \NC the defined glyphs of this font \NC \NR
+\NC checksum           \NC yes      \NC yes      \NC no  \NC number \NC default: 0 \NC \NR
+\NC designsize         \NC no       \NC yes      \NC yes \NC number \NC expected size (default: 655360 == 10pt) \NC \NR
+\NC direction          \NC no       \NC yes      \NC yes \NC number \NC default: 0 (LTR) \NR
+\NC encodingbytes      \NC no       \NC no       \NC yes \NC number \NC default: depends on \type {format}\NC\NR
+\NC encodingname       \NC no       \NC no       \NC yes \NC string \NC encoding name\NC\NR
+\NC fonts              \NC yes      \NC no       \NC yes \NC table  \NC locally used fonts\NC \NR
+\NC fullname           \NC no       \NC no       \NC yes \NC string \NC actual (\POSTSCRIPT) name\NC\NR
+\NC header             \NC yes      \NC no       \NC no  \NC string \NC header comments, if any\NC \NR
+\NC hyphenchar         \NC no       \NC no       \NC yes \NC number \NC default: TeX's \tex{hyphenchar} \NC \NR
+\NC parameters         \NC no       \NC yes      \NC yes \NC hash   \NC default: 7 parameters, all zero \NC \NR
+\NC size               \NC no       \NC yes      \NC yes \NC number \NC loaded (at) size. (default: same as designsize) \NC \NR
+\NC skewchar           \NC no       \NC no       \NC yes \NC number \NC default: TeX's \tex{skewchar}  \NC \NR
+\NC type               \NC yes      \NC no       \NC yes \NC string \NC basic type of this font\NC \NR
+\NC format             \NC no       \NC no       \NC yes \NC string \NC disk format type\NC \NR
+\NC embedding          \NC no       \NC no       \NC yes \NC string \NC \PDF\ inclusion\NC \NR
+\NC filename           \NC no       \NC no       \NC yes \NC string \NC disk file name\NC\NR
+\NC tounicode          \NC no       \NC yes      \NC yes \NC number \NC if 1, \LUATEX\ assumes per-glyph tounicode entries are
+present in the font\NC\NR
+\NC stretch            \NC no       \NC no       \NC yes \NC number \NC the `stretch' value from \type{\pdffontexpand}\NC\NR
+\NC shrink             \NC no       \NC no       \NC yes \NC number \NC the `shrink' value from \type{\pdffontexpand}\NC\NR
+\NC step               \NC no       \NC no       \NC yes \NC number \NC the `step' value from \type{\pdffontexpand}\NC\NR
+\NC auto_expand        \NC no       \NC no       \NC yes \NC boolean\NC the `autoexpand keyword from \type{\pdffontexpand}\NC\NR
+\NC expansion_factor   \NC no       \NC no       \NC no  \NC number \NC the actual expansion factor of an expanded font\NC\NR
+\NC attributes         \NC no       \NC no       \NC yes \NC string \NC the \type{\pdffontattr}\NC\NR
+\stoptabulate
+
+The key \type{name} is always required.
+
+The keys \type{stretch}, \type{shrink}, \type{step} and optionally \type{auto_expand} 
+only have meaning when used together: they can be used to replace a post-loading
+\type{\pdffontexpand} command. 
+
+The \type{expansion_factor} is value that can be present inside a font in \type{font.fonts}.
+It is the actual expansion factor (a value between \type{-shrink} and \type{stretch}, with
+step \type{step}) of a font that was automatically generated by the font expansion algorithm.
+
+The key \type{attributes} can be used to replace \type{\pdffontattr}.
+
+The key \type{used} is set by the engine when a font is actively in
+use, this makes sure that the font's definition is written to the
+output file (\DVI\ or \PDF). The \TFM\ reader sets it to false.
+
+The \type{direction} is a number signalling the \quote{normal} direction for
+this font. There are sixteen possibilities:
+
+\starttabulate[|c|c|c|c|]
+\NC \bf number \NC \bf meaning \NC \bf number \NC \bf meaning \NC\NR
+\NC 0          \NC LT          \NC 8          \NC TT          \NC\NR
+\NC 1          \NC LL          \NC 9          \NC TL          \NC\NR
+\NC 2          \NC LB          \NC 10         \NC TB          \NC\NR
+\NC 3          \NC LR          \NC 11         \NC TR          \NC\NR
+\NC 4          \NC RT          \NC 12         \NC BT          \NC\NR
+\NC 5          \NC RL          \NC 13         \NC BL          \NC\NR
+\NC 6          \NC RB          \NC 14         \NC BB          \NC\NR
+\NC 7          \NC RR          \NC 15         \NC BR          \NC\NR
+\stoptabulate
+
+These are \OMEGA|-|style direction abbreviations: the first character
+indicates the \quote{first} edge of the character glyphs (the edge that is
+seen first in the writing direction), the second the \quote{top} side.
+
+The \type{parameters} is a hash with mixed key types. There are seven
+possible string keys, as well as a number of integer indices (these
+start from 8 up). The seven strings are actually used instead of the
+bottom seven indices, because that gives a nicer user interface.
+
+The names and their internal remapping:
+
+\starttabulate[|l|c|]
+\NC \bf name      \NC \bf internal remapped number \NC\NR
+\NC slant         \NC 1  \NC\NR
+\NC space         \NC 2  \NC\NR
+\NC space_stretch \NC 3  \NC\NR
+\NC space_shrink  \NC 4  \NC\NR
+\NC x_height      \NC 5  \NC\NR
+\NC quad          \NC 6  \NC\NR
+\NC extra_space   \NC 7  \NC\LR
+\stoptabulate
+
+The keys \type{type}, \type{format}, \type{embedding}, \type{fullname} and
+\type{filename} are used to embed \OPENTYPE\ fonts in the result \PDF.
+
+The \type{characters} table is a list of character hashes indexed by
+an integer number. The number is the \quote{internal code} \TEX\ knows this
+character by.
+
+Two very special string indexes can be used also: \type{left_boundary} is a
+virtual character whose ligatures and kerns are used to handle word
+boundary processing. \type{right_boundary} is similar but not actually
+used for anything (yet!).
+
+Other index keys are ignored.
+
+Each character hash itself is a hash. For example, here is the
+character \quote{f} (decimal 102) in the font cmr10 at 10 points:
+
+% hahe: why this complicated notation, why not e. g. width=200250?
+\starttyping
+[102] = {
+  ['width'] = 200250,
+  ['height'] = 455111,
+  ['depth'] = 0,
+  ['italic'] = 50973,
+  ['kerns'] = {
+     [63] = 50973,
+     [93] = 50973,
+     [39] = 50973,
+     [33] = 50973,
+     [41] = 50973
+  },
+  ['ligatures'] = {
+    [102] = {
+       ['char'] = 11,
+       ['type'] = 0
+    },
+    [108] = {
+       ['char'] = 13,
+       ['type'] = 0
+    },
+    [105] = {
+       ['char'] = 12,
+       ['type'] = 0
+    }
+  }
+}
+\stoptyping
+
+The following top|-|level keys can be present inside a character hash:
+
+\starttabulate[|l|c|c|c|l|p|]
+\NC \ssbf key    \NC \bf from vf \NC \bf from tfm \NC \bf used \NC \bf value type \NC \bf description \NC\NR
+\NC width      \NC yes         \NC yes          \NC yes      \NC number         \NC character's width, in sp (default 0) \NC\NR
+\NC height     \NC no          \NC yes          \NC yes      \NC number         \NC character's height, in sp (default 0) \NC\NR
+\NC depth      \NC no          \NC yes          \NC yes      \NC number         \NC character's depth, in sp (default 0) \NC\NR
+\NC italic     \NC no          \NC yes          \NC yes      \NC number         \NC character's italic correction, in sp (default zero) \NC\NR
+\NC left_protruding  \NC no    \NC no           \NC maybe    \NC number         \NC character's \type{\lpcode}\NC\NR
+\NC right_protruding \NC no    \NC no           \NC maybe    \NC number         \NC character's \type{\rpcode}\NC\NR
+\NC expansion_factor \NC no    \NC no           \NC maybe    \NC number         \NC character's \type{\efcode}\NC\NR
+\NC tounicode  \NC no          \NC no           \NC maybe    \NC string         \NC character's Unicode equivalent(s), in
+UTF-16BE hexadecimal format\NC\NR
+\NC next       \NC no          \NC yes          \NC yes      \NC number         \NC the \quote{next larger} character index \NC\NR
+\NC extensible \NC no          \NC yes          \NC yes      \NC table          \NC the constituent parts of an extensible recipe \NC\NR
+\NC kerns      \NC no          \NC yes          \NC yes      \NC table          \NC kerning information \NC\NR
+\NC ligatures  \NC no          \NC yes          \NC yes      \NC table          \NC ligaturing information \NC\NR
+\NC commands   \NC yes         \NC no           \NC yes      \NC array          \NC virtual font commands \NC\NR
+\NC name       \NC no          \NC no           \NC no       \NC string         \NC the character (\POSTSCRIPT) name \NC\NR
+\NC index      \NC no          \NC no           \NC yes      \NC number         \NC the (\OPENTYPE\ or \TRUETYPE) font glyph index \NC\NR
+\NC used       \NC no          \NC yes          \NC yes      \NC boolean        \NC typeset already (default: false)? \NC\NR
+\stoptabulate
+
+The values of \type{left_protruding} and \type{right_protruding} are used only when
+\type{\pdfprotrudechars} is non-zero.
+
+Whether or not \type{expansion_factor} is used depends on the font's global expansion
+settings, as well as on the value of \type{\pdfadjustspacing}.
+
+The usage of \type{tounicode} is this: if this font specifies a \type{tounicode=1} at
+the top level, then \LUATEX\ will construct a \type{/ToUnicode} entry for the PDF
+font (or font subset) based on the character-level \type{tounicode} strings, where
+they are available. If a character does not have a sensible Unicode equivalent,
+do not provide a string either (no empty strings).
+
+If the font-level \type{tounicode} is not set, then \LUATEX\ will build up
+\type{/ToUnicode} based on the \TEX\ code points you used, and any character-level
+\type{tounicodes} will be ignored. {\it At the moment, the string format is exactly the
+format that is expected by Adobe CMAP files (UTF-16BE in hexadecimal encoding), minus
+the enclosing angle brackets. This may change in the future.} Small example: the
+\type{tounicode} for a \type{fi} ligature would be \type{00660069}.
+
+The presence of \type{extensible} will overrule \type{next}, if that is also present.
+
+The \type{extensible} table is very simple:
+
+\starttabulate[|l|l|p|]
+\NC \ssbf key \NC \bf type \NC \bf description                    \NC\NR
+\NC top     \NC number   \NC \quote{top} character index        \NC\NR
+\NC mid     \NC number   \NC \quote{middle} character index     \NC\NR
+\NC bot     \NC number   \NC \quote{bottom} character index     \NC\NR
+\NC rep     \NC number   \NC \quote{repeatable} character index \NC\NR
+\stoptabulate
+
+The \type{kerns} table is a hash indexed by character index (and
+\quote{character index} is defined as either a non|-|negative integer or the
+string value \type {right_boundary}), with the values the kerning to be
+applied, in scaled points.
+
+The \type{ligatures} table is a hash indexed by character index (and
+\quote{character index} is defined as either a non|-|negative integer or the
+string value \type {right_boundary}), with the values being yet another small
+hash, with two fields:
+
+\starttabulate[|l|l|p|]
+\NC \ssbf key \NC \bf type \NC \bf description \NC\NR
+\NC type    \NC number   \NC the type of this ligature command, default 0 \NC\NR
+\NC char    \NC number   \NC the character index of the resultant ligature \NC\NR
+\stoptabulate
+
+The \type{char} field in a ligature is required.
+
+The \type{type} field inside a ligature is the numerical or string value of one of the eight
+possible ligature types supported by \TEX.  When \TEX\ inserts a new ligature, it puts the new
+glyph in the middle of the left and right glyphs. The original left and right glyphs can
+optionally be retained, and when at least one of them is kept, it is also possible to move the
+new \quote{insertion point} forward one or two places. The glyph that ends up to the right of the
+insertion point will become the next \quote{left}.
+
+\starttabulate[|l|c|l|l|]
+\NC \bf textual (Knuth) \NC \bf number \NC \bf string    \NC result \NC\NR
+\NC l + r =: n          \NC 0          \NC \type{=:}     \NC \|n    \NC\NR
+\NC l + r =:\| n        \NC 1          \NC \type{=:|}    \NC \|nr   \NC\NR
+\NC l + r \|=: n        \NC 2          \NC \type{|=:}    \NC \|ln   \NC\NR
+\NC l + r \|=:\| n      \NC 3          \NC \type{|=:|}   \NC \|lnr  \NC\NR
+\NC l + r  =:\|\> n     \NC 5          \NC \type{=:|>}   \NC n\|r   \NC\NR
+\NC l + r \|=:\> n      \NC 6          \NC \type{|=:>}   \NC l\|n   \NC\NR
+\NC l + r \|=:\|\> n    \NC 7          \NC \type{|=:|>}  \NC l\|nr  \NC\NR
+\NC l + r \|=:\|\>\> n  \NC 11         \NC \type{|=:|>>} \NC ln\|r  \NC\NR
+\stoptabulate
+
+The default value is~0, and can be left out. That signifies a \quote{normal}
+ligature where the ligature replaces both original glyphs. In this table
+the~\| indicates the final insertion point.
+
+The \type{commands} array is explained below.
+
+\section {Real fonts}
+
+Whether or not a \TEX\ font is a \quote{real} font that should be written to
+the \PDF\ document is decided by the \type{type} value in the top|-|level
+font structure. If the value is \type{real}, then this is a proper
+font, and the inclusion mechanism will attempt to add the needed
+font object definitions to the \PDF.
+
+Values for \type{type}:
+
+\starttabulate[|l|p|]
+\NC \bf value     \NC \bf description        \NC\NR
+\NC real          \NC this is a base font    \NC\NR
+\NC virtual       \NC this is a virtual font \NC\NR
+\stoptabulate
+
+The actions to be taken depend on a number of different variables:
+
+\startitemize[packed]
+\item Whether the used font fits in an 8-bit encoding scheme or not
+\item The type of the disk font file
+\item The level of embedding requested
+\stopitemize
+
+A font that uses anything other than an 8-bit encoding vector has to
+be written to the \PDF\ in a different way.
+
+The rule is: if the font table has \type {encodingbytes} set to~2,
+then this is a wide font, in all other cases it isn't. The value~2 is
+the default for \OPENTYPE\ and \TRUETYPE\ fonts loaded via \LUA. For
+\TYPEONE\ fonts, you have to set \type {encodingbytes} to~2
+explicitly. For \PK\ bitmap fonts, wide font encoding is not
+supported at all.
+
+If no special care is needed, \LUATEX\ currently falls back to the
+mapfile|-|based solution used by \PDFTEX\ and \DVIPS. This behavior
+will be removed in the future, when the existing code becomes
+integrated in the new subsystem.
+
+But if this is a \quote{wide} font, then the new subsystem kicks in, and
+some extra fields have to be present in the font structure. In this
+case, \LUATEX\ does not use a map file at all.
+
+The extra fields are: \type{format}, \type{embedding}, \type{fullname},
+\type{cidinfo} (as explained above), \type{filename}, and the
+\type{index} key in the separate characters.
+
+Values for \type{format} are:
+
+\starttabulate[|l|p|]
+\NC \bf value \NC \bf description                                           \NC\NR
+\NC type1     \NC this is a \POSTSCRIPT\ \TYPEONE\ font                     \NC\NR
+\NC type3     \NC this is a bitmapped (\PK) font                            \NC\NR
+\NC truetype  \NC this is a \TRUETYPE\ or \TRUETYPE|-|based \OPENTYPE\ font \NC\NR
+\NC opentype  \NC this is a \POSTSCRIPT|-|based \OPENTYPE\ font             \NC\NR
+\stoptabulate
+
+(\type{type3} fonts are provided for backward compatibility only, and do not
+support the new wide encoding options.)
+
+Values for \type{embedding} are:
+
+\starttabulate[|l|p|]
+\NC \bf value \NC \bf description \NC\NR
+\NC no        \NC don't embed the font at all \NC\NR
+\NC subset    \NC include and atttempt to subset the font \NC\NR
+\NC full      \NC include this font in its entirety \NC\NR
+\stoptabulate
+
+It is not possible to artificially modify the transformation matrix
+for the font at the moment.
+
+The other fields are used as follows: The \type{fullname} will be the
+\POSTSCRIPT|/|\PDF\ font name. The \type{cidinfo} will be used as the
+character set (the CID \type{/Ordering} and \type{/Registry} keys). The
+\type{filename} points to the actual font file. If you include the
+full path in the \type{filename} or if the file is in the local
+directory, \LUATEX\ will run a little bit more efficient because it
+will not have to re|-|run the \type{find_xxx_file} callback in that
+case.
+
+Be careful: when mixing old and new fonts in one document, it is possible to
+create \POSTSCRIPT\ name clashes that can result in printing
+errors. When this happens, you have to change the \type{fullname}
+of the font.
+
+Typeset strings are written out in a wide format using 2~bytes per
+glyph, using the \type{index} key in the character information as
+value. The overall effect is like having an encoding based on numbers
+instead of traditional (\POSTSCRIPT) name|-|based reencoding. The way
+to get the correct \type{index} numbers for \TYPEONE\ fonts is by
+loading the font via \type{fontforge.open}; use the table indices as
+\type{index} fields.
+
+This type of reencoding means that there is no longer a clear
+connection between the text in your input file and the strings in the
+output \PDF\ file. Dealing with this is high on the agenda.
+
+\section {Virtual fonts}
+
+You have to take the following steps if you want \LUATEX\ to treat the
+returned table from \luatex{define_font} as a virtual font:
+
+\startitemize[packed]
+\item Set the top|-|level key \type {type} to \type {virtual}.
+\item Make sure there is at least one valid entry in \luatex{fonts} (see below)
+\item Give a \type {commands} array to every character (see below)
+\stopitemize
+
+The presence of the toplevel \type {type} key with the specific value
+\type {virtual} will trigger handling of the rest of the special virtual
+font fields in the table, but the mere existance of 'type' is enough
+to prevent \LUATEX\ from looking for a virtual font on its own.
+
+Therefore, this also works \quote{in reverse}: if you are absolutely certain
+that a font is not a virtual font, assigning the value \type{base} or
+\type{real} to \type{type} will inhibit \LUATEX\ from looking for a virtual font
+file, thereby saving you a disk search.
+
+The \luatex{fonts} is another \LUA\ array. The values are one- or two|-|key
+hashes themselves, each entry indicating one of the base fonts in a
+virtual font. An example makes this easy to understand
+
+\starttyping
+fonts = { { name = 'ptmr8a', size = 655360},
+          { name = 'psyr', size = 600000},
+          { id = 38 } }
+\stoptyping
+
+says that the first referenced font (index 1) in this virtual font is
+\type{ptrmr8a} loaded at 10pt, and the second is \type{psyr}  loaded
+at a little over 9pt. The third one is previously defined font that
+is known to \LUATEX\ as fontid \quote{38}.
+
+The array index numbers are used by the character command definitions
+that are part of each character.
+
+The \luatex{commands} array is a hash where each item is another small array, with the first
+entry representing a command and the extra items being the parameters to that command. The
+allowed commands and their arguments are:
+
+\starttabulate[|l|l|l|p|]
+\NC \bf command name  \NC \bf arguments \NC \bf arg type \NC \bf description \NC\NR
+\NC font              \NC 1         \NC number    \NC select a new font from the local \luatex{fonts} table\NC\NR
+\NC char              \NC 1         \NC number    \NC typeset this character number from the current font, 
+                                                      and move right by the character's width\NC\NR
+\NC node              \NC 1         \NC node      \NC output this node (list), and move right 
+                                                      by the width of this list\NC\NR
+\NC slot              \NC 2         \NC number    \NC a shortcut for the combination of a font and char command\NC\NR
+\NC push              \NC 0         \NC           \NC save current position\NC\NR
+\NC nop               \NC 0         \NC           \NC do nothing \NC\NR
+\NC pop               \NC 0         \NC           \NC pop position \NC\NR
+\NC rule              \NC 2         \NC 2 numbers \NC output a rule $w*h$, and move right.\NC\NR
+\NC down              \NC 1         \NC number    \NC move down on the page\NC\NR
+\NC right             \NC 1         \NC number    \NC move right on the page\NC\NR
+\NC special           \NC 1         \NC string    \NC output a \tex{special} command\NC\NR
+\NC comment           \NC any       \NC any       \NC the arguments of this command are ignored\NC\NR
+\stoptabulate
+
+Here is a rather elaborate glyph commands example:
+\starttyping
+...
+commands = {
+  {'push'},                     -- remember where we are
+  {'right', 5000},              -- move right about 0.08pt
+  {'font', 3},                  -- select the fonts[3] entry
+  {'char', 97},                 -- place character 97 (ASCII 'a')
+  {'pop'},                      -- go all the way back
+  {'down', -200000},            -- move upwards by about 3pt
+  {'special', 'pdf: 1 0 0 rg'}  -- switch to red color
+  {'rule', 500000, 20000}       -- draw a bar
+  {'special','pdf: 0 g'}        -- back to black
+}
+...
+\stoptyping
+
+The default value for \type {font} is always~1 at the start of the \type{commands} array. 
+Therefore, if the virtual font is essentially only a re|-|encoding, then you do usually not 
+have create an explicit \quote{font} command in the array.
+
+Rules inside of \type{commands} arrays are built up using only two dimensions: 
+they do not have depth. For correct vertical placement, an extra \type{down} command 
+may be needed.
+
+Regardless of the amount of movement you create within the \type {commands},
+the output pointer will always move by exactly the width that was given in
+the \type {width} key of the character hash. Any movements that take place 
+inside the \type{commands} array are ignored on the upper level.
+
+\subsection{Artificial fonts}
+
+Even in a \quote{real} font, there can be virtual characters. When \LUATEX\ encounters a \type {commands}
+field inside a character when it becomes time to typeset the character, it will interpret the commands, just
+like for a true virtual character. In this case, if you have created no \quote{fonts} array, then the default
+(and only) \quote{base} font is taken to be the current font itself. In practice, this means that you can
+create virtual duplicates of existing characters which is useful if you want to create composite characters.
+
+Note: this feature does {\it not\/} work the other way around. There can not be \quote{real} characters in a
+virtual font! You cannot use this technique for font re-encoding either; you need a truly virtual 
+font for that (because characters that are already present cannot be altered).
+
+\subsection{Example virtual font}
+
+Finally, here is a plain \TEX\ input file with a virtual font demonstration:
+
+\startbuffer
+\directlua0 {
+  callback.register('define_font',
+    function (name,size)
+      if name == 'cmr10-red' then
+        f = font.read_tfm('cmr10',size)
+        f.name = 'cmr10-red'
+        f.type = 'virtual'
+        f.fonts = {{ name = 'cmr10', size = size }}
+        for i,v in pairs(f.characters) do
+          if (string.char(i)):find('[tacohanshartmut]') then
+             v.commands = {
+               {'special','pdf: 1 0 0 rg'},
+               {'char',i},
+               {'special','pdf: 0 g'},
+              }
+          else
+             v.commands = {{'char',i}}
+          end
+        end
+      else
+        f = font.read_tfm(name,size)
+      end
+      return f
+    end
+  )
+}
+
+\font\myfont = cmr10-red at 10pt \myfont  This is a line of text \par
+\font\myfontx= cmr10 at 10pt \myfontx Here is another line of text \par
+\stopbuffer
+
+\typebuffer
+
+%\getbuffer
+
+\chapter[nodes]{Nodes}
+
+\section{\LUA\ node representation}
+
+\TEX's nodes are represented in \LUA\ as userdata object with a variable
+set of fields. In the following syntax tables, such the type of such a
+userdata object is represented as \syntax{<node>}.
+
+ 
+The current return value of \luatex{node.types()} is: 
+\ctxlua {
+  local d = node.types()
+  tex.print('\\type{' .. d[0] .. '} (' .. 0 .. '), ') 
+  for _,v in pairs(d) do 
+    if _ > 0 then
+      tex.print('\\type{' .. v .. '} (' .. _ .. '), ') 
+    end
+  end 
+} but as already mentioned, the math and alignment nodes
+in this list are not supported at the moment. The useful list
+is described in the next sections.
+
+\subsection{Auxiliary items}
+
+A few node|-|typed userdata objects do not occur in the \quote{normal}
+list of nodes, but can be pointed to from within that list. They are
+not quite the same as regular nodes, but it is easier for the library
+routines to treat them as if they were.
+
+\subsubsection{glue_spec items}
+
+Skips are about the only type of data objects in traditional \TEX\
+that are not a simple value. The structure that represents the glue
+components of a skip is called a \type {glue_spec}, and it has the following
+accessible fields:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf key            \NC \bf type \NC \bf explanation \NC\NR
+\NC width          \NC number  \NC \NC\NR
+\NC stretch        \NC number  \NC \NC\NR
+\NC stretch_order  \NC number  \NC \NC\NR
+\NC shrink         \NC number  \NC \NC\NR
+\NC shrink_order   \NC number  \NC \NC\NR
+\stoptabulate
+
+These objects are reference counted, so there is actually an extra
+field named \type {ref_count} as well. This item type will likely
+disappear in the future, and the glue fields themselves will
+become part of the nodes referencing glue items.
+
+\subsubsection{attribute\_list and attribute items}
+
+The newly introduced attribute registers are non|-|trivial, because
+the value that is attached to a node is essentially a sparse array of
+key|-|value pairs.
+
+It is generally easiest to deal with attribute lists and attributes
+by using the dedicated functions in the \luatex{node} library, but
+for completeness, here is the low|-|level interface. 
+
+An \type{attribute_list} item is used as a head pointer for a list
+of attribute items. It has only one user-visible field:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC next          \NC \syntax{<node>}  \NC pointer to the first attribute\NC\NR
+\stoptabulate
+
+A normal node's attribute field will point to an item of type
+\type{attribute_list}, and the \type{next} field in that item will point 
+to the first defined \quote{attribute} item, whose \type {next} will
+point to the second \quote{attribute} item, etc.
+
+Valid fields in \type{attribute} items:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC next           \NC \syntax{<node>}  \NC pointer to the next attribute\NC\NR
+\NC number         \NC number  \NC the attribute type id\NC\NR
+\NC value          \NC number  \NC the attribute value\NC\NR
+\stoptabulate
+
+\subsubsection{action item}
+
+Valid fields: \showfields{action}
+
+These are a special kind of item that only appears inside
+pdf start link objects. 
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC action_type   \NC  number   \NC  \NC\NR
+\NC action_id     \NC  number or string   \NC  \NC\NR
+\NC named_id      \NC  number   \NC  \NC\NR
+\NC file          \NC  string   \NC  \NC\NR
+\NC new_window    \NC  number   \NC  \NC\NR
+\NC data          \NC  string   \NC  \NC\NR
+\NC ref_count     \NC  number   \NC  \NC\NR
+\stoptabulate
+
+\subsection{Main text nodes}
+
+These are the nodes that comprise actual typesetting commands. 
+
+A few fields are present in all nodes regardless of their type, these are:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC next    \NC \syntax{<node>}  \NC  The next node in a list, or nil\NC\NR
+\NC id      \NC number  \NC  The node's type (\type{id}) number \NC\NR
+\NC subtype \NC number  \NC  The node \type{subtype} identifier\NC\NR
+\stoptabulate
+
+The \type{subtype} is sometimes just a stub entry. Not all nodes
+actually use the \type{subtype}, but this way you can be sure that all
+nodes accept it as a valid field name, and that is often handy in node
+list traversal. In the following tables \type{next} and \type{id} are
+not explicitly mentioned.
+
+Besides these three fields, almost all nodes also have an \type {attr}
+field, and there is a also a field called \type{prev}. That last field
+is always present, but only initialized on explicit request: when the
+function \type{node.slide()} is called, it will set up the \type{prev}
+fields to be a backwards pointer in the argument node list.
+
+
+\subsubsection{hlist nodes}
+
+Valid fields: \showfields{hlist}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  unused\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  The head of the associated attribute list \NC\NR
+\NC width      \NC number  \NC  \NC\NR
+\NC height     \NC number  \NC  \NC\NR
+\NC depth      \NC number  \NC  \NC\NR
+\NC shift      \NC number  \NC  a displacement perpendicular to the
+                                character progression direction \NC\NR
+\NC glue_order \NC number  \NC  a number in the range 0--4, indicating
+                                the glue order\NC\NR
+\NC glue_set   \NC number  \NC  the calculated glue ratio\NC\NR
+\NC glue_sign  \NC number  \NC  \NC\NR
+\NC list       \NC \syntax{<node>}    \NC  the body of this list\NC\NR
+\NC dir        \NC number  \NC  the direction of this box\NC\NR
+\stoptabulate
+
+\subsubsection{vlist nodes}
+
+Valid fields: As for hlist, except that \quote{shift} is a displacement
+perpendicular to the line progression direction.
+
+\subsubsection{rule nodes}
+
+Valid fields: \showfields{rule}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  unused\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC width      \NC number  \NC  rule size. The special value $-1073741824$
+                                is used for \quote{running} glue dimensions\NC\NR
+\NC height     \NC number  \NC  ' '\NC\NR
+\NC depth      \NC number  \NC  ' '\NC\NR
+\NC dir        \NC number  \NC  the direction of this rule\NC\NR
+\stoptabulate
+
+\subsubsection{ins nodes}
+
+Valid fields: \showfields{ins}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  the insertion class\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC cost       \NC number  \NC  the penalty associated with this insert\NC\NR
+\NC height     \NC number  \NC  \NC\NR
+\NC depth      \NC number  \NC  \NC\NR
+\NC list       \NC \syntax{<node>}    \NC  the body of this insert\NC\NR
+\NC spec       \NC \syntax{<node>}    \NC a pointer to the \tex{splittopskip} glue spec\NC\NR
+\stoptabulate
+
+\subsubsection{mark nodes}
+
+Valid fields: \showfields{mark}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  unused\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC class      \NC number  \NC  the mark class\NC\NR
+\NC mark       \NC table   \NC  a table representing a token list\NC\NR
+\stoptabulate
+
+\subsubsection{adjust nodes}
+
+Valid fields: \showfields{adjust}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  0 = normal, 1 = \quote{pre}\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC list       \NC \syntax{<node>}    \NC  adjusted material\NC\NR
+\stoptabulate
+
+\subsubsection{disc nodes}
+
+Valid fields: \showfields{disc}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  indicates the source of a discretionary. 
+                                0 = the \tex{discretionary} command, 
+                                1 = the \tex{-} command, 
+                                2 = added automatically following a \type{-},
+                                3 = added by the hyphenation algorithm\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC pre        \NC \syntax{<node>}    \NC  pointer to the pre|-|break text\NC\NR
+\NC post       \NC \syntax{<node>}    \NC  pointer to the post|-|break text\NC\NR
+\NC replace    \NC \syntax{<node>}    \NC  pointer to the no|-|break text\NC\NR
+\stoptabulate
+
+\subsubsection{math nodes}
+
+Valid fields: \showfields{math}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  0 = \quote{on}, 1 = \quote{off}\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC surround   \NC number  \NC  width of the \tex{mathsurround} kern\NC\NR
+\stoptabulate
+
+\subsubsection{glue nodes}
+
+Valid fields: \showfields{glue}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  0 = \tex{skip},
+                                1--18 = internal glue parameters,
+                                100 = \tex{leaders},
+                                101 = \tex{cleaders},
+                                102 = \tex{xleaders}  \NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC spec       \NC \syntax{<node>}    \NC  pointer to a glue\_spec item \NC\NR
+\NC leader     \NC \syntax{<node>}    \NC  pointer to a box or rule for leaders\NC\NR
+\stoptabulate
+
+\subsubsection{kern nodes}
+
+Valid fields: \showfields{kern}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  0 = from font,
+                                1 = from \tex{kern} or \tex{/},
+                                2 = from \tex{accent}\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC kern      \NC number  \NC  \NC\NR
+\stoptabulate
+
+
+\subsubsection{penalty nodes}
+
+Valid fields: \showfields{penalty}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  not used\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC penalty    \NC number  \NC  \NC\NR
+\stoptabulate
+
+\subsubsection[glyphnodes]{glyph nodes}
+
+Valid fields: \showfields{glyph}
+
+\newbox\mybox
+\setbox\mybox=\hbox{\vbox {\hsize=3cm
+\starttabulate[|l|l|]
+\NC bit 0 \NC character \NC\NR
+\NC bit 1 \NC glyph     \NC\NR
+\NC bit 2 \NC ligature  \NC\NR
+\NC bit 3 \NC ghost     \NC\NR
+\NC bit 4 \NC left      \NC\NR
+\NC bit 5 \NC right     \NC\NR
+\stoptabulate 
+}}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field\NC \ssbf type         \NC \ssbf explanation \NC\NR
+\NC subtype    \NC number             \NC bitfield, with bits:\crlf
+                                          \copy\mybox\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC \NC\NR
+\NC char       \NC number             \NC \NC\NR
+\NC font       \NC number             \NC \NC\NR
+\NC lang       \NC number             \NC \NC\NR
+\NC left       \NC number             \NC \NC\NR
+\NC right      \NC number             \NC \NC\NR
+\NC uchyph     \NC boolean            \NC \NC\NR
+\NC components \NC \syntax{<node>}    \NC pointer to ligature components\NC\NR
+\NC xoffset    \NC number             \NC \NC\NR
+\NC yoffset    \NC number             \NC \NC\NR
+\stoptabulate
+
+See \in{section}[charsandglyphs] for a detailed description of the
+\type{subtype} field.
+
+\subsubsection{margin\_kern nodes}
+
+Valid fields: \showfields{margin_kern}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC subtype    \NC number  \NC  0 = left side,
+                                1 = right side\NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC width      \NC number  \NC  \NC\NR
+\NC glyph      \NC \syntax{<node>}    \NC  \NC\NR
+\stoptabulate
+
+\subsection{whatsit nodes}
+
+Whatsit nodes come in many subtypes that you can ask for by running
+\luatex{node.whatsits()}: 
+\ctxlua {for _,v in pairs(node.whatsits()) do
+tex.print('\\type{' .. v .. '} (' .. _ .. '), ') end }
+
+\subsubsection{open nodes}
+
+Valid fields: \showfields{whatsit,open}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC stream    \NC number  \NC \TEX's stream id number\NC\NR
+\NC name      \NC string  \NC file name \NC\NR
+\NC ext       \NC string  \NC file extension \NC\NR
+\NC area      \NC string  \NC file area \NC\NR
+\stoptabulate
+
+\subsubsection{write nodes}
+
+Valid fields: \showfields{whatsit,write}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC stream    \NC number  \NC \TEX's stream id number\NC\NR
+\NC data      \NC table   \NC a table representing the token list to be written\NC\NR
+\stoptabulate
+
+\subsubsection{close nodes}
+
+Valid fields: \showfields{whatsit,close}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC stream    \NC number  \NC \TEX's stream id number\NC\NR
+\stoptabulate
+
+\subsubsection{special nodes}
+
+Valid fields: \showfields{whatsit,special}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC data      \NC string  \NC the \tex{special} information\NC\NR
+\stoptabulate
+
+\subsubsection{language nodes}
+
+
+\LUATEX\ does not have language whatsits any more. All language 
+information is already present inside the glyph nodes themselves.
+This whatsit subtype will be removed in the next release.
+
+
+\subsubsection{local_par nodes}
+
+Valid fields: \showfields{whatsit,local_par}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC pen_inter \NC number  \NC interline penalty\NC\NR
+\NC pen_broken\NC number  \NC broken penalty\NC\NR
+\NC dir       \NC number  \NC the direction of this par\NC\NR
+\NC box_left  \NC \syntax{<node>}      \NC the \tex{localleftbox}\NC\NR
+\NC box_left_width\NC number\NC width of the \tex{localleftbox}\NC\NR
+\NC box_right  \NC \syntax{<node>}      \NC the \tex{localrightbox}\NC\NR
+\NC box_right_width\NC number\NC width of the \tex{localrightbox}\NC\NR
+\stoptabulate
+
+\subsubsection{dir nodes}
+
+Valid fields: \showfields{whatsit,dir}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC dir       \NC number  \NC the direction\NC\NR
+\NC level     \NC number  \NC nesting level of this direction whatsit\NC\NR
+\NC dvi_ptr   \NC number  \NC a saved dvi buffer byte offset\NC\NR
+\NC dir_h     \NC number  \NC a saved dvi position\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_literal nodes}
+
+Valid fields: \showfields{whatsit,pdf_literal}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC mode      \NC number  \NC  the \quote{mode} setting of this literal\NC\NR
+\NC data      \NC string  \NC the \tex{pdfliteral} information\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_refobj nodes}
+
+Valid fields: \showfields{whatsit,pdf_refobj}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC objnum    \NC number  \NC the referenced \PDF\ object number\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_refxform nodes}
+
+Valid fields: \showfields{whatsit,pdf_refxform}. 
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC width     \NC number  \NC \NC \NR
+\NC height    \NC number  \NC \NC \NR
+\NC depth     \NC number  \NC \NC \NR
+\NC objnum    \NC number  \NC the referenced \PDF\ object number\NC\NR
+\stoptabulate
+
+Be aware that \type{pdf_refxform} nodes have dimensions that are used by \LUATEX.
+
+\subsubsection{pdf_refximage nodes}
+
+Valid fields: \showfields{whatsit,pdf_refximage}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC width     \NC number  \NC \NC \NR
+\NC height    \NC number  \NC \NC \NR
+\NC depth     \NC number  \NC \NC \NR
+\NC objnum    \NC number  \NC the referenced \PDF\ object number\NC\NR
+\stoptabulate
+
+Be aware that \type{pdf_refximage} nodes have dimensions that are used by \LUATEX.
+
+\subsubsection{pdf_annot nodes}
+
+Valid fields: \showfields{whatsit,pdf_annot}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC width     \NC number  \NC \NC \NR
+\NC height    \NC number  \NC \NC \NR
+\NC depth     \NC number  \NC \NC \NR
+\NC objnum    \NC number  \NC the referenced \PDF\ object number\NC\NR
+\NC data      \NC string  \NC the annotation data\NC\NR
+\stoptabulate
+
+
+\subsubsection{pdf_start_link nodes}
+
+Valid fields: \showfields{whatsit,pdf_start_link}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC width     \NC number  \NC \NC \NR
+\NC height    \NC number  \NC \NC \NR
+\NC depth     \NC number  \NC \NC \NR
+\NC objnum    \NC number  \NC the referenced \PDF\ object number\NC\NR
+\NC link_attr \NC table   \NC the link attribute token list\NC\NR
+\NC action    \NC \syntax{<node>}    \NC the action to perform\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_end_link nodes}
+
+Valid fields: \showfields{whatsit,pdf_end_link}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\stoptabulate
+
+\subsubsection{pdf_dest nodes}
+
+Valid fields: \showfields{whatsit,pdf_dest}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC width     \NC number  \NC \NC \NR
+\NC height    \NC number  \NC \NC \NR
+\NC depth     \NC number  \NC \NC \NR
+\NC named_id  \NC number  \NC is the dest_id a string value?\NC\NR
+\NC dest_id   \NC number or string \NC the destination id\NC\NR
+\NC dest_type \NC number\NC type of destination\NC\NR
+\NC xyz_zoom  \NC number\NC \NC\NR
+\NC objnum    \NC number  \NC the \PDF\ object number\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_thread nodes}
+
+Valid fields: \showfields{whatsit,pdf_thread}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC width      \NC number  \NC \NC \NR
+\NC height     \NC number  \NC \NC \NR
+\NC depth      \NC number  \NC \NC \NR
+\NC named_id   \NC number  \NC is the tread_id a string value?\NC\NR
+\NC tread_id   \NC number or string \NC the thread id\NC\NR
+\NC thread_attr\NC number           \NC extra thread information\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_start_thread nodes}
+
+Valid fields: \showfields{whatsit,pdf_start_thread}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr       \NC \syntax{<node>}    \NC  \NC\NR
+\NC width      \NC number  \NC \NC \NR
+\NC height     \NC number  \NC \NC \NR
+\NC depth      \NC number  \NC \NC \NR
+\NC named_id   \NC number  \NC is the tread_id a string value?\NC\NR
+\NC tread_id   \NC number or string \NC the thread id\NC\NR
+\NC thread_attr\NC number           \NC extra thread information\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_end_thread nodes}
+
+Valid fields: \showfields{whatsit,pdf_end_thread}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\stoptabulate
+
+\subsubsection{pdf_save_pos nodes}
+
+Valid fields: \showfields{whatsit,pdf_save_pos}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\stoptabulate
+
+\subsubsection{late_lua nodes}
+
+Valid fields: \showfields{whatsit,late_lua}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC reg       \NC number  \NC \LUA\ state id number \NC\NR
+\NC data      \NC string  \NC data to execute\NC\NR
+\stoptabulate
+
+\subsubsection{close_lua nodes}
+
+Valid fields: \showfields{whatsit,close_lua}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC reg    \NC number  \NC \LUA\ state id number\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_colorstack  nodes}
+
+Valid fields: \showfields{whatsit,pdf_colorstack}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC stack    \NC number  \NC colorstack id number\NC\NR
+\NC cmd      \NC number  \NC command to execute\NC\NR
+\NC data     \NC string  \NC data\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_setmatrix nodes}
+
+Valid fields: \showfields{whatsit,pdf_setmatrix}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC data     \NC string  \NC data\NC\NR
+\stoptabulate
+
+\subsubsection{pdf_save nodes}
+
+Valid fields: \showfields{whatsit,pdf_save}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\stoptabulate
+
+\subsubsection{pdf_restore nodes}
+
+Valid fields: \showfields{whatsit,pdf_restore}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\stoptabulate
+
+\subsubsection{user_defined nodes}
+
+User-defined whatsit nodes can only be created and handled from Lua
+code. In effect, they are an extension to the extension
+mechanism. The \LUATEX\ engine will simply step over such whatsits
+without ever looking at the contents.
+
+Valid fields: \showfields{whatsit,user_defined}
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf field     \NC \bf type \NC  \bf explanation \NC\NR
+\NC attr      \NC \syntax{<node>}    \NC  \NC\NR
+\NC user_id  \NC number  \NC id number\NC\NR
+\NC type     \NC number  \NC type of the value\NC\NR
+\NC value    \NC number  \NC \NC\NR
+\NC          \NC string  \NC \NC\NR
+\NC          \NC \syntax{<node>}   \NC \NC\NR
+\NC          \NC table \NC \NC\NR
+\stoptabulate
+
+The \type{type} can have one of five distinct values:
+
+\starttabulate[|lT|l|p|]
+\NC \ssbf value   \NC  \bf explanation \NC\NR
+\NC  97           \NC  the value is an attribute node list \NC\NR
+\NC  100          \NC  the value is a number \NC\NR
+\NC  110          \NC  the value is a node list \NC\NR
+\NC  115          \NC  the value is a token list in string form\NC\NR
+\NC  116          \NC  the value is a token list in lua table form\NC\NR
+\stoptabulate
+
+
+\chapter{Modifications}
+
+Besides the expected changes caused by new functionality, there are a
+number of not|-|so|-|expected changes. These are sometimes a side|-|effect
+of a new (conflicting) feature, or, more often than not, a change
+necessary to clean up the internal interfaces.
+
+\section{Changes from \TEX\ 3.141592}
+
+\startitemize
+
+\item See~\in{chapter}[languages] for many small changes related to paragraph 
+  building, language handling, and hyphenation.
+
+\item There is no pool file, all strings are embedded during compilation.
+
+\item \type {plus 1 fillll} does not generate an error. The extra \quote{l} is
+simply typeset.
+
+\item The \tex{endlinechar} can be either added (values 0 or more), or not
+(negative values). If it is added, the character is always decimal 13 a/k/a
+\type{^^M} a/k/a carriage return (This change may be temporary).
+
+\item The banner line and the statistics messages are different, as
+well as many warnings and error texts.
+
+\stopitemize
+
+\section{Changes from \ETEX\ 2.2}
+
+\startitemize
+
+\item The \ETEX\ functionality is always present and enabled
+   (but see below about \TEXXET), so the prepended asterisk or
+   \type{-etex} switch for \INITEX\ is not needed.
+
+\item \TEXXET\ is not present, so the primitives
+
+\starttyping
+\TeXXeTstate
+\beginR
+\beginL
+\endR
+\endL
+\stoptyping
+
+are missing.
+
+\item Some of the tracing information that is output by \ETEX's \tex{tracingassigns} and 
+  \tex{tracingrestores} is not there.
+
+\item Register management in \LUATEX\ uses the \ALEPH\ model, so the maximum value is 65535
+  and the implementation uses a flat array instead of the mixed
+ flat|\&|sparse model from \ETEX.
+
+\item \type{savinghyphcodes} is a no-op and may possibly be removed. 
+ See~\in{chapter}[languages] for details.
+
+\stopitemize
+
+\section{Changes from \PDFTEX\ 1.40}
+
+\startitemize
+
+\item The (experimental) support for snap nodes has been removed, because 
+it is much more natural to build this functionality on top of node
+processing and attributes. The associated primitives that are now gone
+are: \tex{pdfsnaprefpoint}, \tex{pdfsnapy}, and \tex{pdfsnapycomp}.
+
+\item The (experimental) support for specialized spacing around nodes 
+has also been removed. The associated primitives that are now gone are:
+\tex{pdfadjustinterwordglue}, \tex{pdfprependkern}, and \tex{pdfappendkern}, 
+as well as the five supporting primitives \tex{knbscode}, \tex{stbscode}, 
+\tex{shbscode}, \tex{knbccode}, and \tex{knaccode}.
+
+
+
+\item A number of \quote{utility functions} is removed:
+
+\startcolumns[n=3]
+\starttyping
+\pdfelapsedtime
+\pdfescapehex
+\pdfescapename
+\pdfescapestring
+\pdffiledump
+\pdffilemoddate
+\pdffilesize
+\pdflastmatch
+\pdfmatch
+\pdfmdfivesum
+\pdfresettimer
+\pdfshellescape
+\pdfstrcmp
+\pdfunescapehex
+\stoptyping
+\stopcolumns
+
+\item A few other experimental primitives are also provided without the
+      extra  \luatex {pdf} prefix, so they can also be called like this:
+
+\startcolumns[n=3]
+\starttyping
+\primitive
+\ifprimitive
+\ifabsnum
+\ifabsdim
+\stoptyping
+\stopcolumns
+
+\item The definitions for new didot and new cicero are patched.
+
+\item The \tex{pdfprimitive} is bugfixed.
+
+\item The \tex{pdftexversion} is set to 200.
+
+\stopitemize
+
+\section{Changes from \ALEPH\ RC4}
+
+\startitemize
+
+\item The input translations from \ALEPH\ are not implemented, the
+   related primitives are not available:
+
+\startcolumns[n=2]
+\starttyping
+\DefaultInputMode
+\noDefaultInputMode
+\noInputMode
+\InputMode
+\DefaultOutputMode
+\noDefaultOutputMode
+\noOutputMode
+\OutputMode
+\DefaultInputTranslation
+\noDefaultInputTranslation
+\noInputTranslation
+\InputTranslation
+\DefaultOutputTranslation
+\noDefaultOutputTranslation
+\noOutputTranslation
+\OutputTranslation
+\stoptyping
+\stopcolumns
+
+\item A small series of bounds checking fixes to \tex{ocp} and
+   \tex{ocplist} has been added to prevent the system from crashing
+   due to array indexes running out of bounds.
+
+\item The \tex{hoffset} bug when \tex{pagedir TRT}  is fixed,
+removing the need for an explicit fix to \tex{hoffset}
+
+\item A bug causing \tex{fam} to fail for family numbers above
+    15 is fixed.
+
+\item Some bits of \ALEPH\ assumed \type{0} and \type{null} were identical.
+This resulted for instance in a bug that sometimes caused an eternal
+loop when trying to \tex{show} a box.
+
+\item A fair amount of other minor bugs are fixed as well, most of these
+related to \tex{tracingcommands} output.
+
+\item The number of possible fonts, ocps and ocplists is
+smaller than their maximum \ALEPH\ value (around 5000 fonts and
+30000 ocps / ocplists).
+
+\item The internal function \type{scan_dir()} has been renamed to
+\type{scan_direction()} to prevent a naming clash.
+
+\item The \type{^^} notation can come in five and six item repetitions also, to
+insert characters that do not fit in the BMP.
+
+\item Glues {\it immediately after} direction change commands are not 
+legal breakpoints.
+
+\item The \tex{ocp} and \tex{ocplist} statistics at the end of a run
+are only printed if OCP's are actually used.
+
+\stopitemize
+
+\section{Changes from standard \WEBC}
+
+\startitemize
+
+\item There is no mltex
+
+\item There is no enctex
+
+\item The following commandline switches are silently ignored, even
+in non|-|\LUA\ mode:
+
+\starttyping
+-8bit
+-translate-file=TCXNAME
+-mltex
+-enc
+-etex
+\stoptyping
+
+\item \tex{openout} whatsits are not written to the log file.
+
+\item Some of the so|-|called web2c extensions are hard to set up
+  in non|-|\KPSE\ mode because texmf.cnf is not read: \type{shell-escape}
+  is off (but that is not a problem because of \LUA's
+  \lua{os.execute}), and the paranoia checks on \type{openin} and
+  \type{openout} do not happen (however, it is easy for a \LUA\ script
+  to do this itself by overloading \lua{io.open}).
+
+
+\stopitemize
+
+\chapter{Implementation notes}
+
+\section{Primitives overlap}
+
+The primitives
+
+\starttabulate[|l|l|]
+\NC \tex{pdfpagewidth} \NC \tex{pagewidth}  \NC \NR
+\NC \tex{pdfpageheight}\NC \tex{pageheight} \NC \NR
+\NC \tex{fontcharwd}   \NC \tex{charwd}     \NC \NR
+\NC \tex{fontcharht}   \NC \tex{charht}     \NC \NR
+\NC \tex{fontchardp}   \NC \tex{chardp}     \NC \NR
+\NC \tex{fontcharic}   \NC \tex{charic}     \NC \NR
+\stoptabulate
+
+are all aliases of each other.
+
+\section{Memory allocation}
+
+The single internal memory heap that traditional \TEX\ used for tokens
+and nodes is split into two separate arrays. Each of these will grow
+dynamically when needed.
+
+The \type{texmf.cnf} settings related to main memory are no longer
+used (these are: \type{main_memory}, \type{mem_bot},
+\type{extra_mem_top} and \type{extra_mem_bot}). \quote{Out of main
+memory} errors can still occur, but the limiting factor is now the
+amount of RAM in your system, not a predefined limit.
+
+Also, the memory (de)allocation routines for nodes are completely
+rewritten. The relevant code now lives in the C file \type{luanode.c},
+and basically uses a dozen or so avail lists instead of a
+doubly|-|linked model. An extra function layer is added so that the 
+code can ask for nodes by type instead of directly requisitioning
+a certain amount of memory words.
+
+Because of the split into two arrays and the resulting differences in
+the data structures, some of the Pascal \WEB\ macros have been
+duplicated.  For instance, there are now \type{vlink} and \type{vinfo}
+as well as \type{link} and \type{info}. All access to the variable
+memory array is now hidden behind a macro called \type{vmem}.
+
+The implementation of the growth of two arrays (via reallocation)
+introduces a potential pitfall: the memory arrays should never be used
+as the left hand side of a statement that can modify the array in
+question.
+
+The input line buffer and pool size are now also reallocated when
+needed, and the \type{texmf.cnf} settings \type{buf_size} and
+\type{pool_size} are silently ignored.
+
+\section{Sparse arrays}
+
+The \tex{mathcode}, \tex{delcode}, \tex{catcode},
+\tex{sfcode}, \tex{lccode} and \tex{uccode} tables are now
+sparse arrays that are implemented in~C. They are no longer part of
+the \TEX\ \quote{equivalence table} and because each had 1.1 million
+entries with a few memory words each, this makes a major difference
+in memory usage.
+
+These assignments do not yet show up when using the etex tracing
+routines \tex{tracingassigns} and \tex{tracingrestores} (code
+simply not written yet).
+
+A side|-|effect of the current implementation is that \tex{global} is
+now more expensive in terms of processing than non|-|global assignments.
+
+See \type{mathcodes.c} and \type{textcodes.c} if you are interested in
+the details.
+
+Also, the glyph ids within a font are now managed by means
+of a sparse array and glyph ids can go up to index $2^{21}-1$.
+
+\section{Simple single-character csnames}
+
+Single|-|character commands are no longer treated specially in the
+internals, they are stored in the hash just like the multiletter
+csnames.
+
+The code that displays control sequences explicitly checks if
+the length is one when it has to decide whether or not to add a
+trailing space.
+
+\section{Compressed format}
+
+The format is passed through zlib, allowing it to shrink to roughly
+half of the size it would have had in uncompressed form. This takes a
+bit more CPU cycles but much less disk I/O, so it should still be
+faster.
+
+\section{Binary file reading}
+
+All of the internal code is changed in such a way that if one of the
+\type{read_xxx_file} callbacks is not set, then the file is read by
+a C function using basically the same convention as the callback: a
+single read into a buffer big enough to hold the entire file
+contents. While this uses more memory than the previous code (that
+mostly used \type{getc} calls), it can be quite a bit faster
+(depending on your I/O subsystem).
+
+\chapter{Known bugs and limitations}
+
+The bugs below are going to be fixed eventually.
+
+The top ones will be fixed soon, but in the later items either the
+actual problem is hard to find, or the code that causes the bug is
+going to be replaced by a new subsystem soon anyway, or it may not
+be worth the hassle and the limitations will eventually be documented.
+
+\startitemize
+
+\item The current linebreaking implementation does not yet take all 
+possible breakpoints into account where ligatures are involved in
+the process.  This means that line breaks may change in future
+versions.
+
+\item Sometimes font loading via fontforge generates a message like this
+\starttyping
+Bad call to gww_iconv_open, neither arg is UCS4 (EUC-CN->UTF-8)
+\stoptyping
+during font loading. This is a limitation of the internal iconv
+implementation.
+
+\item Font expansion does not work quite as it should. On the mailing
+list (sep 21), Jonathan Sauer posted a very nice test file along with
+an explanation. 
+
+\item \luatex{tex.print()} and \luatex{tex.sprint()} do not work if
+\tex{directlua} is used in an \OTP\ file (in the output of an
+\type{expression} rule).
+
+\item Handling of attributes in math mode is not complete. The data
+structures in math mode are quite different from those in text mode,
+so this will take some extra effort to implement correctly.
+
+\item When used inside  \type{\directlua}, \type{pdf.print()} should create a
+literal node instead of flushing immediately.
+
+\item At the moment, only characters in plane~0 and plane~1 can be
+assigned catcode~13 (i.\,e.\ turned into active characters). This is a
+temporary measure to reduce the memory requirements of \LUATEX.  In
+general, \LUATEX's memory footprint is a bit larger that we would
+like (with \type{plain.fmt} preloaded it needs about 55MB).
+
+\item Not all of \ALEPH's direction commands are handled properly in
+\PDF\ mode, and especially the vertical scripts support is missing
+almost completely (only TRT and TLT are routinely tested).
+
+\item Letter spacing (\tex{letterspacefont}) is currently non|-|functional
+due to massive changes in the virtual font handling. This
+functionality may actually be removed completely in the future,
+because it is straightforward to set up letterspacing using the \LUA\
+\quote{define_font} interface.
+
+\item Node pointers are not always checked for validity, so if you make a 
+mistake in the node list processing, \LUATEX\ may terminate itself with an
+assertion error or \quote{Emergency stop}.
+
+\item In \DVI\ generation mode, using a \type{\textdir} switch inside the
+preamble of a \type{\halign} results in overprinted text in the \DVI\ file,
+because the column width is not taken into account during the final
+placement phase (this is a bug inherited from \ALEPH). Also, \ALEPH\
+apparently dislikes having more than one non-grouped \type{\textdir}
+command in a single lined paragraph.
+
+\item Certain constructs in math mode leak memory nodes. 
+
+\stopitemize
+
+
+\chapter{TODO}
+
+On top of the \quote{normal} extensions that are planned, there are
+some more specific small feature requests. Whether these will all be
+included is not certain yet, (and new requests are welcome).
+
+\startitemize
+
+\item Implement the \TEX\ primitive \tex{dimension}, cf.\ \tex{number}.
+
+\item Change the \LUA\ table \type{tex.dimen} to accept and return float
+values instead of strings.
+
+\item Do something about \tex{withoutpt} and/or a new register type \tex{real}?
+
+\item Create callback for the automatic creation of missing
+characters in fonts.
+
+\item Implement the \TEX\ primitive \tex{htdp}?
+
+\item Do boxes with dual baselines.
+
+\item A way to (re?)calculate the width of a  \tex{vbox}, taking only
+the natural width of the included items into account.
+
+\item Make the number of the output box configurable.
+
+\item Complete the attributes in math and switch all the nodes to a double|-|linked list.
+
+\item Finish the interface from Lua to \TeX's internals, specially the hash and 
+equivalence table (a small subpart is implementing \type{\csname}
+lookups for \type{tex.box} access).
+
+\item Use of Type1C for embedded PostScript font subsets in
+traditional 8-bit encodings.
+
+\item Support font reencoding of 8-bit fonts via char index instead of
+via map files.
+
+\item Attempt to parse OFM level~0 fonts that are masquerading as level~1.
+
+\item Add line numbers and input context information to the lua errors.
+\stopitemize
+
+\stoptext