2020-11-23 18:39:00

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diff --git a/tex/context/base/mkxl/strc-sec.mkxl b/tex/context/base/mkxl/strc-sec.mkxl
new file mode 100644
index 000000000..e5371d1e9
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+++ b/tex/context/base/mkxl/strc-sec.mkxl
@@ -0,0 +1,1321 @@
+%D \module
+%D   [       file=strc-sec,
+%D        version=2008.10.20,
+%D          title=\CONTEXT\ Structure Macros,
+%D       subtitle=Sectioning,
+%D         author=Hans Hagen,
+%D           date=\currentdate,
+%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
+%C
+%C This module is part of the \CONTEXT\ macro||package and is
+%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
+%C details.
+
+%D In retrospect I should have gone futher and move more to the
+%D \LUA\ end but here we are now. Maybe some day.
+
+\writestatus{loading}{ConTeXt Structure Macros / Sectioning}
+
+\unprotect
+
+\startcontextdefinitioncode
+
+\installcorenamespace{structure}
+
+\installdirectcommandhandler \??structure {structure} % unchecked, so we need to initialize used parameters
+
+\setupstructure % not a user command so we might need to change the name
+  [\c!number=,
+   \c!level=,
+   \c!name=,
+   \c!title=,
+   \c!bookmark=,
+   \c!marking=,
+   \c!list=,
+   \c!label=,
+   \c!coupling=,
+   \c!ownnumber=,
+ % \c!interaction=\v!list,
+   \c!sectionseparatorset=\s!default,
+   \c!sectionconversionset=\s!default,
+   \c!sectionstopper=,
+   \c!sectionstarter=,
+   \c!sectionsegments=,
+   \c!sectionresetset=,
+   \c!reference=,
+   \c!backreference=,
+   \c!expansion=\v!no,
+   \c!xmlsetup=,
+   \s!catcodes=,
+   \c!saveinlist=\v!yes]
+
+% maybe flags for list, bm, mark
+
+\def\m_strc_references_prefix_yes{+}
+\def\m_strc_references_prefix_nop{-}
+
+\let\currentstructurereferenceprefix\empty
+
+\installglobalmacrostack\currentstructurereferenceprefix
+
+\def\strc_sectioning_set_reference_prefix
+  {\ifempty\currentstructurereferenceprefix
+     % nothing
+   \orelse\ifx\currentstructurereferenceprefix\m_strc_references_prefix_yes
+     \global\advance\prefixcounter \plusone % temp here
+     \setupglobalreferenceprefix[\the\prefixcounter]%
+   \orelse\ifx\currentstructurereferenceprefix\m_strc_references_prefix_nop
+     \setupglobalreferenceprefix[]%
+   \else
+     \setupglobalreferenceprefix[\currentstructurereferenceprefix]%
+   \fi
+   \glet\currentstructurereferenceprefix\referenceprefix}
+
+% why xdef ?
+
+\setupstructure
+  [\c!label={\headparameter{\currentsectionblock\c!label}},
+   \c!incrementnumber=\ifconditional\c_strc_sectioning_increment\v!yes\else\v!no\fi, % not that needed
+   \c!saveinlist=\ifconditional\c_strc_sectioning_to_list\v!yes\else\v!no\fi,
+   \c!level=\currentheadlevel,
+   \c!number=\ifconditional\c_strc_sectioning_increment\ifconditional\headshownumber\v!yes\else\v!no\fi\else\v!no\fi,
+   \c!expansion=\headparameter\c!expansion,
+   \c!xmlsetup=\headparameter\c!xmlsetup,
+   \s!catcodes=\headparameter\s!catcodes,
+   \c!sectionresetset=\headparameter\c!sectionresetset,
+   \c!sectionseparatorset=\headparameter\c!sectionseparatorset,
+   \c!sectionconversionset=\headparameter\c!sectionconversionset,
+   \c!sectionconversion=\headparameter\c!conversion, % just for compatibility
+   \c!sectionstarter=\headparameter\c!sectionstarter,
+   \c!sectionstopper=\headparameter\c!sectionstopper,
+   \c!sectionset=\headparameter\c!sectionset,
+   \c!sectionsegments=\headparameter\c!sectionsegments,
+   \c!reference=\headparameter\c!reference,
+   \c!referenceprefix=\headparameter\c!referenceprefix,
+   \c!criterium=\headparameter\c!criterium]
+
+% see lists/neat-001.tex for usage of:
+
+\permanent\def\namedstructureheadlocation#1% expandable, maybe [#1]
+  {\csname\??savedinternalreference\ifcsname\??savedinternalreference#1\endcsname#1\else\s!default\fi\endcsname}
+
+% The next directive only makes sense when we have sort of garanteed outcome (math is not so
+% nice for instance).
+%
+% \enabledirectives[references.bookmarks.preroll]
+
+\newconditional\c_strc_bookmarks_preroll
+
+\installtexdirective
+  {references.bookmarks.preroll}
+  {\settrue \c_strc_bookmarks_preroll}
+  {\setfalse\c_strc_bookmarks_preroll}
+
+\def\strc_sectioning_autobookmark#1%
+  {\begingroup
+ % \settrialtypesetting
+   \the\everypreroll
+   \nodestostring\tempstring{#1}%
+   \glet\currentstructurebookmark\tempstring
+   \endgroup}
+
+% zeros:
+%
+% \setuphead[subsection][criterium=all]
+%
+% \dorecurse{3} {
+%     \chapter{Blabla}                 \subsection{bla 1 1} \subsection{bla 1 2}
+%                      \section{bla 2} \subsection{bla 2 1} \subsection{bla 2 2}
+% }
+
+\protected\def\strc_sectioning_register#1#2#3% #1=interfaced-settings, #2=optional user data (not yet supported)
+  {\begingroup
+   \setupstructure[\c!name={#1},#2]%
+   \xdef\currentstructurename           {\structureparameter\c!name}%
+   \xdef\currentstructurecoupling       {\structureparameter\c!coupling}%
+   \xdef\currentstructureownnumber      {\structureparameter\c!ownnumber}% optional own number
+   \xdef\currentstructurelevel          {\structureparameter\c!level}%
+   \edef\currentstructureexpansion      {\structureparameter\c!expansion}%
+   \xdef\currentstructurexmlsetup       {\structureparameter\c!xmlsetup}%
+   \xdef\currentstructurecatcodes       {\structureparameter\s!catcodes}%
+   \xdef\currentstructurelabel          {\structureparameter\c!label}%
+   \xdef\currentstructurereference      {\structureparameter\c!reference}%
+   \xdef\currentstructurereferenceprefix{\structureparameter\c!referenceprefix}%
+   \xdef\currentstructurebackreference  {\structureparameter\c!backreference}%
+   \xdef\currentstructureshownumber     {\structureparameter\c!number}%
+   \xdef\currentstructuresaveinlist     {\structureparameter\c!saveinlist}%
+   \xdef\currentstructureincrementnumber{\structureparameter\c!incrementnumber}%
+   \xdef\currentstructureplaceholder    {\structureparameter\c!placeholder}%
+   \ifx\currentstructureexpansion\s!xml
+     \xmlstartraw
+       \xdef\currentstructuretitle   {\structureparameter\c!title}%
+       \xdef\currentstructurebookmark{\structureparameter\c!bookmark}%
+       \xdef\currentstructuremarking {\structureparameter\c!marking}%
+       \xdef\currentstructurelist    {\structureparameter\c!list}%
+     \xmlstopraw
+     \iflocation \ifempty\currentstructurebookmark \ifconditional\c_strc_bookmarks_preroll
+       \strc_sectioning_autobookmark\currentstructuretitle
+     \fi \fi \fi
+     \ifempty\currentstructurelist
+       \glet\currentstructurelist\currentstructuretitle
+     \fi
+     \glet\currentstructurecoding\s!xml
+   \else
+     \ifx\currentstructureexpansion\v!yes
+       \xdef\currentstructuretitle   {\structureparameter\c!title}%
+       \xdef\currentstructurebookmark{\structureparameter\c!bookmark}%
+       \xdef\currentstructuremarking {\structureparameter\c!marking}%
+       \xdef\currentstructurelist    {\structureparameter\c!list}%
+       \iflocation \ifempty\currentstructurebookmark \ifconditional\c_strc_bookmarks_preroll
+         \strc_sectioning_autobookmark\currentstructuretitle
+       \fi \fi \fi
+     \else
+       \xdef\currentstructuretitle   {\detokenizedstructureparameter\c!title}%
+       \xdef\currentstructurebookmark{\detokenizedstructureparameter\c!bookmark}%
+       \xdef\currentstructuremarking {\detokenizedstructureparameter\c!marking}%
+       \xdef\currentstructurelist    {\detokenizedstructureparameter\c!list}%
+       \iflocation \ifempty\currentstructurebookmark
+         \ifconditional\c_strc_bookmarks_preroll
+           \strc_sectioning_autobookmark{\structureparameter\c!title}%
+         \else
+           \begingroup
+           \simplifycommands
+           \xdef\currentstructurebookmark{\detokenize\expandafter{\normalexpanded{\structureparameter\c!title}}}%
+           \endgroup
+         \fi
+       \fi \fi
+     \fi
+     \ifempty\currentstructurelist
+       \glet\currentstructurelist\currentstructuretitle
+     \fi
+     \glet\currentstructurecoding\s!tex
+   \fi
+   \setnextinternalreference
+   \storeinternalreference\currentstructurename{\the\locationcount}%
+   \strc_sectioning_set_reference_prefix
+   \clf_setsectionentry
+        references {
+            internal      \locationcount
+          % block         {\currentsectionblock}
+            prefix        {\currentstructurereferenceprefix}
+            reference     {\currentstructurereference}
+            backreference {\currentstructurebackreference}
+        }
+        directives {
+            resetset {\structureparameter\c!sectionresetset}
+        }
+        metadata {
+            kind      {section}
+            name      {\currentstructurename}
+            catcodes  \ifempty\currentstructurecatcodes\catcodetable\else\csname\currentstructurecatcodes\endcsname\fi\space
+            coding    {\currentstructurecoding}
+        \ifx\currentstructurecoding\s!xml
+            xmlroot   {\xmldocument}
+        \fi
+        \ifempty\currentstructurexmlsetup \else
+            xmlsetup  {\currentstructurexmlsetup}
+        \fi
+        \ifx\currentstructuresaveinlist\v!no
+            nolist \space true\space
+        \fi
+        \ifx\currentstructureincrementnumber\v!yes
+            increment {\currentstructureincrementnumber}
+        \fi
+        }
+        titledata {
+            label    {\detokenize\expandafter{\currentstructurelabel}}
+            title    {\detokenize\expandafter{\currentstructuretitle}}
+        \ifx\currentstructurebookmark\currentstructuretitle \else
+            bookmark {\detokenize\expandafter{\currentstructurebookmark}}
+        \fi
+        \ifx\currentstructuremarking\currentstructuretitle \else
+            marking  {\detokenize\expandafter{\currentstructuremarking}}
+        \fi
+        \ifx\currentstructuresaveinlist\v!no \else
+          \ifx\currentstructurelist\currentstructuretitle \else
+            list     {\detokenize\expandafter{\currentstructurelist}}
+          \fi
+        \fi
+        }
+        numberdata {
+          % block         {\currentsectionblock}
+        \ifx\currentstructureshownumber\v!no
+            hidenumber    \space true\space % space needed for parser
+        \fi
+            separatorset  {\structureparameter\c!sectionseparatorset}
+            conversionset {\structureparameter\c!sectionconversionset}
+            conversion    {\structureparameter\c!sectionconversion}
+            starter       {\structureparameter\c!sectionstarter}
+            stopper       {\structureparameter\c!sectionstopper}
+            set           {\structureparameter\c!sectionset}
+            segments      {\structureparameter\c!sectionsegments}
+            ownnumber     {\currentstructureownnumber}
+            language      {\currentlanguage}% for the moment, needed for bookmarks conversion
+            criterium     {\structureparameter\c!criterium}
+        }
+        userdata {\detokenize{#3}}% will be converted to table at the lua end
+   \relax
+   \xdef\currentstructurelistnumber{\clf_currentsectiontolist}%
+ % \currentstructuresynchronize has to be called someplace, since it introduces a node
+   \setstructuresynchronization\currentstructurelistnumber
+   \endgroup}
+
+\let\currentsectioncountervalue \!!zerocount % redefined later
+\let\previoussectioncountervalue\!!zerocount % redefined later
+
+% We can access the (stored) data with the following macros.
+%
+% \def\MyHeadCommand  #1#2{\framed{#1}\framed{#2 / \structureuservariable{subtitle}}}
+% \def\MyListCommand#1#2#3{\externalfigure[\structurelistuservariable{figure}][height=5mm]#2}
+%
+% \setuphead[chapter][command=\MyHeadCommand]
+% \setuplist[chapter][alternative=command,command=\MyListCommand]
+%
+% \starttext
+%     \setupheadertexts[chapter]
+%     \setupinteraction[state=start]
+%     \placebookmarks[chapter]
+%     \placelist[chapter]
+%     \startchapter[ownnumber=10,title=Ton,list=Hans,marking=Kees,bookmark=Bram][figure=cow.pdf,subtitle=oeps]
+%     \stopchapter
+% \stoptext
+
+% todo: #1 => "#1" ... adapt lua code for name and number
+
+\permanent\def\structurenumber               {\clf_structurenumber}
+\permanent\def\structuretitle                {\clf_structuretitle}
+\permanent\def\structurevariable           #1{\clf_structurevariable         {#1}}
+\permanent\def\structureuservariable       #1{\clf_structureuservariable     {#1}}
+\permanent\def\structurecatcodedget        #1{\clf_structurecatcodedget      {#1}}    % bad name
+\permanent\def\structuregivencatcodedget #1#2{\clf_structuregivencatcodedget {#1}#2 } % bad name
+\permanent\def\structureautocatcodedget  #1#2{\clf_structureautocatcodedget  {#1}{#2}}
+\permanent\def\namedstructurevariable    #1#2{\clf_namedstructurevariable    {#1}{#2}}
+\permanent\def\namedstructureuservariable#1#2{\clf_namedstructureuservariable{#1}{#2}}
+
+% compatibility issue:
+%
+% \def\setfullsectionnumber #1{}
+% \def\preparefullnumber    #1{}
+% \def\fullsectionnumber    {1--1--1}
+% \def\makesectionnumber    [#1]{}
+% \def\makesectionformat    {}
+% \def\sectionformat        {1--1-1-1-1-1-1}
+% \def\composedsectionnumber{}
+% \def\@@kolist{}
+
+% \setuphead[section]   [separator=\separatorlist{?,!,*}]
+% \setuphead[subsection][separator=\separatorlist{??,!!,**}]
+%
+% \let\spr\separatorlist % this will enable this feature
+%
+% \setuphead[section]   [separator={?,!,*}]
+% \setuphead[subsection][separator={??,!!,**}]
+%
+% \setupheads[separator={A,B,C,D,E,F}]
+% \chapter{test}
+% \section{test} \subsection{test} \subsection{test}
+% \section{test} \subsection{test} \subsection{test}
+
+% lua interface / names and interface might change
+
+% \newconditional\c_strc_rendering_continuous % not used (mkii ?)
+
+\permanent\def\setstructurelevel         #1#2{\clf_setstructurelevel         {#1}{#2}}         % name, level|parent
+\permanent\def\getstructurelevel           #1{\clf_getstructurelevel         {#1}}             % name
+\permanent\def\setstructurenumber        #1#2{\clf_setstructurenumber         #1{#2}}          % level, number (+/-)
+\permanent\def\getstructurenumber          #1{\clf_getstructurenumber         \numexpr#1\relax} % level
+\permanent\def\getsomestructurenumber    #1#2{\clf_getsomestructurenumber     #1{#2}}           % level, what
+\permanent\def\getfullstructurenumber      #1{\clf_getfullstructurenumber     \numexpr#1\relax} % level
+\permanent\def\getsomefullstructurenumber#1#2{\clf_getsomefullstructurenumber #1{#2}}           % level, what
+\permanent\def\getspecificstructuretitle   #1{\clf_getspecificstructuretitle {#1}{\headparameter\s!catcodes}}
+
+% structure heads (like \startchapter)
+
+% \c!deeptextcommand, \c!deepnumbercommand: undefined !
+% \c!before \c!after \c!distance
+% \c!page \c!header  \c!text \c!footer=,
+% \c!numbercommand \c!textcommand \c!ownnumber \c!number
+% \c!file \c!grid \c!margintext
+% \c!expansion \c!xmlsetup \s!catcode
+
+\installcorenamespace{head}
+\installcorenamespace{headlevel}
+\installcorenamespace{headincrement}
+\installcorenamespace{headplace}
+\installcorenamespace{headmarkyes}
+\installcorenamespace{headmarknop}
+
+\installcommandhandler \??head {head} \??head
+
+\installmacrostack\currenthead
+\installmacrostack\currentheadparent
+
+\setuphead [%
+    %\c!after=,
+    %\c!align=,
+    %\c!aligntitle=,
+    \c!alternative=\v!normal,
+    %\c!before=,
+    %\c!color=,
+    %\c!command=,
+    \c!continue=\v!yes,
+    %\c!coupling=,
+    %\c!deepnumbercommand=,
+    %\c!deeptextcommand=,
+    %\c!default=,
+    \c!distance=\zeropoint,
+    \c!textdistance=\zeropoint,
+    \c!textwidth=\zeropoint,   % signal too
+    \c!numberwidth=\zeropoint, % signal too
+    \c!width=\zeropoint,       % signal too
+    \c!expansion=\v!no,
+    %\c!file=,
+    %\c!footer=,
+    %\c!grid=,
+    \c!hang=\v!none,
+    %\c!header=,
+    \c!incrementnumber=\v!yes,
+    \c!indentnext=\v!no,
+    %\c!label=,
+    %\c!limittext=\languageparameter\c!limittext,
+    \c!margin=\zeropoint,
+    %\c!margintext=,
+    \c!number=\v!yes,
+    \c!numbercolor=\headparameter\c!color,
+    \c!textcolor=\headparameter\c!color,
+    \c!numberstyle=\headparameter\c!style,
+    \c!textstyle=\headparameter\c!style,
+    %\c!numbercommand=,
+    %\c!textcommand=,
+    \c!ownnumber=\v!no,
+    %\c!page=,
+    \c!placehead=\v!yes,
+    \c!sectionconversionset=\s!default,
+    \c!sectionnumber=\v!yes,
+    %\c!sectionsegments=,
+    \c!sectionseparatorset=\s!default,
+    \c!sectionset=\v!all,
+    \c!interlinespace=,
+    %\c!sectionstopper=,
+    %\c!sectionstarter=,
+    %\c!strut=,
+    %\c!style=,
+    %\c!text=,
+    %\c!tolerance=,
+    %\c!beforesection=\directsetup{document:\currenthead:start},  % these might become defaults i.e. acpect document: namespace
+    %\c!insidesection=\directsetup{document:\currenthead:inside}, % these might become defaults i.e. acpect document: namespace
+    %\c!aftersection=\directsetup{document:\currenthead:stop},    % these might become defaults i.e. acpect document: namespace
+   ]
+
+\aliased\let\setupheads\setuphead % will go
+
+\appendtoks
+    \ifempty\currentheadparent
+        \edef\currentheaddefault{\headparameter\c!default}%
+        \edef\currentheadsection{\headparameter\c!section}%
+        \ifx\currenthead\currentheaddefault
+          \let\currentheadparent\currentheadsection
+        \orelse\ifempty\currentheaddefault
+          \let\currentheadparent\currentheadsection
+        \else
+          \let\currentheadparent\currentheaddefault
+        \fi
+        \normalexpanded {%
+            \setheadparameter{\c!label}{\currenthead}%
+            \setheadparameter{\c!coupling}{\currenthead}%
+            \setheadparameter{\s!parent}{\??head\currentheadparent}%
+            \definemarking[\currenthead]         [\currentheadsection]%
+            \definemarking[\currenthead\v!number][\currentheadsection]%
+            \setupmarking [\currenthead]         [\c!filtercommand=\noexpand\sectionheadmarkingtitle {\currenthead}]%
+            \setupmarking [\currenthead\v!number][\c!filtercommand=\noexpand\sectionheadmarkingnumber{\currenthead}]%
+        }%
+        \doifelselist\currenthead\donothing
+          {\definelist[\currenthead][\c!prefix=\v!no]}%
+        % we can't do this now for backward compatibility reasons
+      % \doifelselist\currenthead\donothing
+      %   {\normalexpanded{\definelist[\currenthead][\currentheadparent][\c!prefix=\v!no]}}%
+    \else
+        \normalexpanded {%
+            \setheadparameter{\c!label}{\currenthead}%
+            \setheadparameter{\c!coupling}{\currentheadparent}%
+            \definemarking[\currenthead]         [\currentheadparent]%
+            \definemarking[\currenthead\v!number][\currentheadparent\c!number]%
+        }%
+        \doifelselist\currenthead\donothing
+          {\normalexpanded{\definelist[\currenthead][\currentheadparent][\c!prefix=\v!no]}}%
+    \fi
+    \presetlabeltext[\currenthead=]%
+    \the\everysetuphead
+\to \everydefinehead
+
+\newtoks\everyredefinehead
+
+\appendtoks
+    \the\everyredefinehead
+\to \everydefinehead
+
+\appendtoks
+   \setstructurelevel\currenthead{\thenamedheadlevel\currenthead}%
+\to \everyredefinehead
+
+\appendtoks
+    % beware, this is a global register
+    \begingroup
+    \edef\currentsectionheadcoupling{\sectionheadcoupling\currenthead}%
+    \edef\currentsectionheadsection {\sectionheadsection \currentsectionheadcoupling}%
+    \edef\currentsectionlevel       {\sectionlevel       \currentsectionheadsection}%
+    \clf_registersection {\currenthead} {
+        coupling {\currentsectionheadcoupling}
+        section  {\currentsectionheadsection}
+        level    \space \currentsectionlevel \space % space needed for parser
+        parent   {\currentheadparent}
+    }%
+    \endgroup
+\to \everyredefinehead
+
+\appendtoks
+   \frozen\instance\setuevalue{\e!start\currenthead}{\strc_sectioning_start[\currenthead]}%
+   \frozen\instance\setuevalue{\e!stop \currenthead}{\strc_sectioning_stop [\currenthead]}%
+\to \everydefinehead
+
+% so \subject as well as \section will need two commands when ownnumber
+% is used (one can disable it anyway for subject) .. this is not downward
+% compatible but better
+
+\appendtoks
+    \ifempty\currenthead \else
+      \doifelse{\headparameter\c!ownnumber}\v!yes
+        {\instance\setuevalue\currenthead{\strc_sectioning_handle_own[\currenthead]}}
+        {\instance\setuevalue\currenthead{\strc_sectioning_handle_nop[\currenthead]}}%
+    \fi
+\to \everysetuphead
+
+\permanent\protected\def\doredefinehead#1#2% called at lua end
+  {\push_macro_currenthead
+   \push_macro_currentheadparent
+   \edef\currenthead{#1}%
+   \edef\currentheadparent{#2}%
+   \the\everyredefinehead\relax
+   \pop_macro_currentheadparent
+   \pop_macro_currenthead}
+
+\let\currentnamedsection\empty
+
+\installmacrostack\currentnamedsection
+
+% structure sections (the parents of chapter etc)
+
+\let\firstsectionname\empty
+\let\lastsectionname \empty
+
+\let\resetallstructuremarks            \relax
+\let\resetcurrentstructuremarks        \relax
+\let\resetcurrentstructuremarkswithpage\relax
+
+\def\resetallstructuremarks            {\resetmarking[\firstsectionname]} % will become option (was \v!section-1)
+\def\resetcurrentstructuremarks        {\resetmarking[\lastsectionname]}  % will become option
+%def\resetcurrentstructuremarkswithpage{\resetmarking[\lastsectionname]}  % will become option
+
+% We could use a commandhandler here but sections are somewhat special in the
+% sense that we have two ways of chaining: the main section (levels) as well
+% as rendering (head).
+
+% -2 = text
+% -1 = manual
+%  0 = block
+% +1 = structurelevel 1 .. n
+
+\newcount\maxstructuredepth
+
+\permanent\def\sectionlevel#1%
+  {\csname\??headlevel\ifcsname\??headlevel#1\endcsname#1\else\v!none\fi\endcsname}
+
+\permanent\def\namedsectionlevel#1#2% direct indirect
+  {\csname\??headlevel
+     \ifcsname\??headlevel#1\endcsname
+       #1%
+     \orelse\ifcsname\??headlevel#2\endcsname
+       #2%
+     \else
+       \v!none
+     \fi
+   \endcsname}
+
+\permanent\def\xthenamedheadlevel#1%
+  {\namedsectionlevel{#1}{\sectionheadsection{\sectionheadcoupling{#1}}}}
+
+\setvalue{\??headlevel\v!block}{0}
+\setvalue{\??headlevel\v!none }{-1}
+\setvalue{\??headlevel\v!text }{-2}
+\setvalue{\??headlevel\v!head }{-3}
+
+\newtoks\everydefinesection
+
+\permanent\protected\def\definesection[#1]%
+  {\ifcsname\??headlevel#1\endcsname \else
+     \edef\currentsection{#1}% not used, will go
+     \edef\currenthead{#1}%
+     \global\advance\maxstructuredepth\plusone
+     \setevalue{\??headlevel#1}{\the\maxstructuredepth}%
+     \setstructurelevel{#1}{\sectionlevel{#1}}%
+     \normalexpanded{\setheadparameter{\s!parent}{\??head\lastsectionname}}% TO BE CHECKED, WE HAVE A HELPER
+     \the\everydefinesection
+     % so far for these default inheritances
+     \definemarking[#1]%
+     \ifnum\maxstructuredepth>\plusone
+       \normalexpanded{\relatemarking[#1][\lastsectionname]}% so, the parent will reset the child
+     \fi
+     \xdef\lastsectionname{#1}%
+     \ifempty\firstsectionname
+        \glet\firstsectionname\lastsectionname
+     \fi
+   \fi}
+
+\permanent\tolerant\protected\def\setupsection[#1]#*[#2]#*[#3]%
+  {\ifparameter#1\else
+     \push_macro_currenthead
+     \edef\currenthead{\ifcsname\??headlevel#1\endcsname#1\else\sectionheadsection{#1}\fi}%
+     \ifparameter#3\or
+       \edef\currenthead{\currenthead#2}% not used at any more in mkiv (sets now)
+       \setupcurrenthead[#3]%
+     \else
+       \setupcurrenthead[#2]%
+     \fi
+     \pop_macro_currenthead
+   \fi}
+
+% we share the parameters as sections are roots of heads so eventually we can
+% consider \definesection -> \definehead with one argument
+
+\appendtoks
+    % This is a rather practical default that we don't want to
+    % be part of the parent chain lookup mechanism; it's also
+    % mkii compatible. Somewhat weird that it's part of the
+    % top level structure but it will be flattened anyway.
+    \let\currenthead\currentsection %
+    \setheadparameter\c!textstyle  {\directheadparameter\c!style}%
+    \setheadparameter\c!textcolor  {\directheadparameter\c!color}%
+    \setheadparameter\c!numberstyle{\directheadparameter\c!style}%
+    \setheadparameter\c!numbercolor{\directheadparameter\c!color}%
+\to \everydefinesection
+
+% head -> head
+
+\permanent\def\sectionheadmarkingtitle #1#2{\clf_markingtitle {#1}{#2}} % can be done at lua end
+\permanent\def\sectionheadmarkingnumber#1#2{\clf_markingnumber{#1}{#2}} % can be done at lua end
+
+\permanent\def\sectionheadcoupling#1{\namedheadparameter{#1}\c!coupling}
+\permanent\def\sectionheadsection #1{\namedheadparameter{#1}\c!section}
+
+% head construction
+
+\newconditional\currentstructureown
+
+\newtoks\everybeforehead % hook, todo: before/after keys
+\newtoks\everyafterhead  % hook, todo: before/after keys
+
+\permanent\tolerant\protected\def\strc_sectioning_handle_own[#1]#*[#2]#:#*#=#*#=% [ref] {nr} {title}
+  {\settrue\currentstructureown
+   \triggerautostructurelevel
+   \strc_sectioning_handle{#1}{\c!reference={#2},\c!ownnumber={#3},\c!title={#4}}{}} % name ref nr title --
+
+\permanent\tolerant\protected\def\strc_sectioning_handle_nop[#1]#*[#2]%  [ref] {title} / for taco: [key=value] variant
+  {\setfalse\currentstructureown
+   \triggerautostructurelevel
+   \ifhastok={#2}%
+     \expandafter\strc_sectioning_handle_nop_indeed_yes
+   \else
+     \expandafter\strc_sectioning_handle_nop_indeed_nop
+   \fi
+   {#1}{#2}}
+
+\def\strc_sectioning_handle_nop_indeed_yes#1#2%
+  {\strc_sectioning_handle{#1}{#2}{}}
+
+\def\strc_sectioning_handle_nop_indeed_nop#1#2#3%
+  {\strc_sectioning_handle{#1}{\c!reference={#2},\c!title={#3}}{}} % name ref nr title --
+
+\permanent\tolerant\protected\def\strc_sectioning_start[#1]#*[#2]#*[#3]% for the moment no grouping, too annoying with page breaks
+  {\push_macro_currentnamedsection
+   \push_macro_currentstructurereferenceprefix
+   \edef\currentnamedsection{#1}%
+   \setfalse\currentstructureown
+  %\globalpushmacro\currenthead % this does not work out well
+   \xdef\currenthead{#1}%
+   \setsystemmode\currenthead % new, also here now
+   \headparameter\c!beforesection % beware, no users vars set yet
+   \the\everybeforehead
+   \strc_sectioning_handle{#1}{#2}{#3}% name -- -- -- userdata (we might move the tagged to here)
+   % potential: \bgroup (can be optional: grouped = yes)
+   \headparameter\c!insidesection}
+
+\permanent\protected\def\strc_sectioning_stop[#1]% !!! also used at lua end
+  {\dostoptagged
+   \dostoptagged
+   % potential: \egroup
+  %\globalpopmacro\currenthead % so we do a hard recover
+   \xdef\currenthead{#1}% recover
+   \headparameter\c!aftersection
+   \the\everyafterhead
+   \resetsystemmode\currenthead
+   \pop_macro_currentstructurereferenceprefix
+   \pop_macro_currentnamedsection} % new, also here now
+
+\aliased\let\dostarthead\strc_sectioning_start % used at lua end
+\aliased\let\dostophead \strc_sectioning_stop  % used at lua end
+
+% todo: add grouping but where: before/after trickery .. probably inside because one can always add
+% grouping to the before/after settings
+
+\aliased\let\startnamedsection\strc_sectioning_start
+
+\permanent\protected\def\stopnamedsection
+  {\normalexpanded{\strc_sectioning_stop[\currentnamedsection]}}
+
+% \newconditional\structurereversesectionnumbers  % todo: key/val
+
+\newconditional\c_strc_sectioning_to_list
+\newconditional\c_strc_sectioning_increment
+\newconditional\c_strc_sectioning_place
+\newconditional\c_strc_sectioning_empty
+\newconditional\c_strc_sectioning_hidden
+\newconditional\c_strc_sectioning_section
+
+\newconditional\headshownumber  % public
+\newconditional\headisdisplay   % public
+\newconditional\headissomewhere % public
+
+\setvalue{\??headincrement\v!yes  }{\settrue \c_strc_sectioning_increment\settrue \c_strc_sectioning_to_list}
+\setvalue{\??headincrement\v!no   }{\setfalse\c_strc_sectioning_increment\setfalse\c_strc_sectioning_to_list}
+\setvalue{\??headincrement\v!list }{\setfalse\c_strc_sectioning_increment\settrue \c_strc_sectioning_to_list}
+\setvalue{\??headincrement\s!empty}{\settrue \c_strc_sectioning_increment\settrue \c_strc_sectioning_to_list}
+
+\protected\def\strc_sectioning_initialize_increment
+  {\edef\currentheadincrement{\headparameter\c!incrementnumber}%
+   \ifcsname\??headincrement\currentheadincrement\endcsname
+     \lastnamedcs
+   \else
+     \settrue \c_strc_sectioning_increment\settrue \c_strc_sectioning_to_list
+     % \filterheadnumber
+   \fi}
+
+\permanent\protected\def\filterheadnumber
+  {\settrue\c_strc_sectioning_increment
+   \settrue\c_strc_sectioning_to_list
+   \ifempty\currentproduct
+     % todo : filter from other toc (number, file, title)
+     % use  : \currentheadincrement as spec
+   \fi}
+
+\setvalue{\??headplace\v!yes}%
+  {\setfalse\c_strc_sectioning_empty
+   \settrue \c_strc_sectioning_place
+   \setfalse\c_strc_sectioning_hidden
+   \setfalse\c_strc_sectioning_section}
+
+\setvalue{\??headplace\v!empty}%
+  {\settrue \c_strc_sectioning_empty
+   \settrue \c_strc_sectioning_place
+   \setfalse\c_strc_sectioning_hidden
+   \setfalse\c_strc_sectioning_section}
+
+\setvalue{\??headplace\v!no}%
+  {\settrue \c_strc_sectioning_empty
+   \setfalse\c_strc_sectioning_place
+   \setfalse\c_strc_sectioning_hidden
+   \setfalse\c_strc_sectioning_section}
+
+\setvalue{\??headplace\v!hidden}%
+  {\settrue \c_strc_sectioning_empty
+   \setfalse\c_strc_sectioning_place
+   \settrue \c_strc_sectioning_hidden
+   \setfalse\c_strc_sectioning_section}
+
+\setvalue{\??headplace\v!section}%
+  {\settrue \c_strc_sectioning_empty
+   \setfalse\c_strc_sectioning_place
+   \settrue \c_strc_sectioning_hidden
+   \settrue \c_strc_sectioning_section}
+
+\protected\def\strc_sectioning_initialize_placement
+  {\expandnamespaceparameter\??headplace\headparameter\c!placehead\v!yes}
+
+\newmode\v!sectionnumber
+
+\def\dosetstructureheadnumbercontent
+  {\setsystemmode\v!sectionnumber
+   \settrue\headshownumber} % why ?
+
+\def\doresetstructureheadnumbercontent
+  {\resetsystemmode\v!sectionnumber
+   \setfalse\headshownumber} % why ?
+
+\protected\def\strc_sectioning_initialize_number
+  {\edef\p_number{\sectionblockparameter\c!number}%
+   \ifx\p_number\v!yes
+      \edef\p_number{\headparameter\c!number}%
+      \ifx\p_number\v!yes
+        \settrue\headshownumber
+      \else
+        \setfalse\headshownumber
+      \fi
+   \else
+     \setfalse\headshownumber
+   \fi}
+
+% Beware, we do need some node for anchoring marks and normally a zwnj will
+% do but it interferes so we deal with it at the \LUA\ end.
+
+\newtoks\everyheadsynchronization
+
+% \appendtoks
+%     \currentstructuresynchronize
+% \to \everyheadsynchronization
+
+\aliased\let\currentstructuresynchronize\donothing
+
+\appendtoks
+    \currentstructuresynchronize
+    \enforced\glet\currentstructuresynchronize\donothing
+\to \everyheadsynchronization
+
+\protected\def\theheadsynchonization
+  {% no, interferes: \signalcharacter
+   \the\everyheadsynchronization}
+
+% BEWARE: \marking[section]{my text} does not work as we use list indices instead
+% so we need a 'keep track of raw set option' (or maybe a funny internal prefix)
+
+\permanent\protected\def\setheadmarking % li:: so that we can use \marking[section]{Taco needed this}
+  {\strc_sectioning_delayed_flush
+   \normalexpanded{\setmarking[\currenthead]{li::\currentstructurelistnumber}}}
+
+\let\deepstructurenumbercommand\relax
+\let\deepstructuretitlecommand \relax
+
+\permanent\protected\def\fullheadnumber
+  {\edef\currentheadlabeltag{\currentsectionblock\c!label}%
+   \dostarttagged\t!sectionnumber\empty
+   \labeltexts
+     {\headparameter\currentheadlabeltag}
+     {\ifx\deepstructurenumbercommand\relax
+        \structurenumber
+      \else
+        \normalexpanded{\noexpand\deepstructurenumbercommand{\structurenumber}}%
+      \fi}%
+   \dostoptagged}
+
+\permanent\protected\def\fullheadtitle
+  {\dostarttagged\t!sectiontitle\empty
+   \ifx\deepstructuretitlecommand\relax
+     \structuretitle
+   \else
+     \normalexpanded{\noexpand\deepstructuretitlecommand{\structuretitle}}%
+   \fi
+   \dostoptagged}
+
+\let\currenthead        \empty
+\let\currentheadcoupling\empty
+\let\currentheadsection \empty
+\let\currentheadlevel   \!!zerocount
+\let\currentheadcounter \!!zerocount
+
+\let\strc_show_used\relax
+
+\installtextracker
+  {structures.showused}
+  {\let\strc_show_used\clf_showstructure}
+  {\let\strc_show_used\relax}
+
+\appendtoks
+    \strc_show_used
+\to \everystoptext
+
+\protected\def\strc_sectioning_report{\clf_reportstructure}
+
+\ifdefined\strc_rendering_initialize_style_and_color \else
+
+    \protected\def\strc_rendering_initialize_style_and_color#1#2%
+      {\dontconvertfont
+       \useheadstyleandcolor\c!style\c!color
+       \useheadstyleandcolor#1#2%
+       \setupinterlinespace}
+
+\fi
+
+\permanent\tolerant\protected\def\placeheadtext[#1]%
+  {\dontleavehmode
+   \begingroup
+   \protected\def\\{\space}% messy here, but the default (and needs to be grouped)
+   \global\settrue\headisdisplay % triggers interlinespace checking
+   \edef\currenthead{#1}% maybe only when #1 is given
+   \strc_rendering_initialize_style_and_color\c!textstyle\c!textcolor
+   \relax
+   \getspecificstructuretitle{\thenamedheadlevel{#1}}%
+   \endgraf
+   \endgroup}
+
+\permanent\tolerant\protected\def\placeheadnumber[#1]%
+  {\dontleavehmode
+   \begingroup
+   \global\settrue\headisdisplay % triggers interlinespace checking
+   \edef\currenthead{#1}% maybe only when #1 is given
+   \strc_rendering_initialize_style_and_color\c!numberstyle\c!numbercolor
+   \relax
+   \getfullstructurenumber{\thenamedheadlevel{#1}}%
+   \endgraf
+   \endgroup}
+
+\ifdefined\triggerautostructurelevel \else \let\triggerautostructurelevel\relax \fi
+
+\newtoks\everybeforesectionheadhandle
+\newtoks\everyaftersectionheadhandle
+
+\def\strc_sectioning_handle#1#2#3% name data userdata (we can move #1 to the caller)
+  {\xdef\currenthead        {#1}%
+   \xdef\currentheadcoupling{\sectionheadcoupling\currenthead}%
+   \xdef\currentheadsection {\sectionheadsection \currentheadcoupling}%
+   \xdef\currentheadlevel   {\sectionlevel       \currentheadsection}%
+   %
+   %\writestatus\m!system{setup: \currenthead,\currentheadcoupling,\currentheadsection,\currentheadlevel}%
+   %
+   \strc_sectioning_initialize_autolevel
+   \strc_sectioning_initialize_increment
+   \strc_sectioning_initialize_placement
+   \strc_sectioning_initialize_number
+   %
+   \the\everybeforesectionheadhandle
+   %
+   % todo: also mark (for header)
+   %
+   % we might remove the lower level
+   %
+   % not here, after optional \page: \strc_sectioning_register{#1}{#2}{#3}%
+   %
+%    \xdef\currentheadcounter{\currentsectioncountervalue}% lua call
+   %
+   % \currentstructuresynchronize % will move
+   %
+   \let\getheadnumber\empty
+   \let\getheadtitle \empty
+   \let\getheadsyncs \empty
+   \ifconditional\c_strc_sectioning_increment
+     \ifconditional\c_strc_sectioning_place
+       \strc_sectioning_before_yes
+       \strc_sectioning_register{#1}{#2}{#3}% after optional \page
+       \strc_sectioning_report
+       \dostarttagged\t!sectioncaption\empty
+       \let\getheadsyncs\theheadsynchonization
+       \let\getheadtitle\fullheadtitle
+       \ifconditional\headshownumber
+         \let\getheadnumber\fullheadnumber
+         \strc_rendering_place_head_number_and_text
+       \else
+         \strc_rendering_place_head_text
+       \fi
+       \dostoptagged
+       \strc_sectioning_after_yes
+     \orelse\ifconditional\c_strc_sectioning_hidden
+       \strc_sectioning_register{#1}{#2}{#3}% after optional \page
+       \strc_sectioning_report
+       \dostarttagged\t!sectioncaption\empty
+       \let\getheadsyncs\theheadsynchonization
+       \ifconditional\c_strc_sectioning_section
+         \strc_rendering_place_head_section
+       \else
+         \strc_rendering_place_head_hidden % only something when tracing
+       \fi
+       \dostoptagged
+     \else
+       \strc_sectioning_before_nop % toegevoegd ivm subpaginanr / tug sheets
+       \strc_sectioning_register{#1}{#2}{#3}% after optional \page
+       \strc_sectioning_report
+       \dostarttagged\t!sectioncaption\empty
+       \let\getheadsyncs\theheadsynchonization
+       \strc_rendering_place_head_empty % just flush 'm
+       \dostoptagged
+       \strc_sectioning_after_nop
+     \fi
+   \else
+     \ifconditional\c_strc_sectioning_place
+       \strc_sectioning_before_yes
+       \strc_sectioning_register{#1}{#2}{#3}% after optional \page
+       \strc_sectioning_report
+       \dostarttagged\t!sectioncaption\empty
+       \let\getheadsyncs\theheadsynchonization
+       \let\getheadtitle\fullheadtitle
+       \strc_rendering_place_head_text
+       \dostoptagged
+       \strc_sectioning_after_yes
+     \orelse\ifconditional\c_strc_sectioning_hidden
+       \strc_sectioning_register{#1}{#2}{#3}% after optional \page
+       \strc_sectioning_report
+       \let\getheadsyncs\theheadsynchonization
+       \dostarttagged\t!sectioncaption\empty
+       \ifconditional\c_strc_sectioning_section
+         \strc_rendering_place_head_section
+       \else
+         \strc_rendering_place_head_hidden % only something when tracing
+       \fi
+       \dostoptagged
+     \else
+       % do nothing / should be vbox to 0pt
+       \strc_sectioning_before_nop
+       \strc_sectioning_register{#1}{#2}{#3}% after optional \page
+       \strc_sectioning_report
+       \dostarttagged\t!sectioncaption\empty
+       \let\getheadsyncs\theheadsynchonization
+       \strc_rendering_place_head_empty % just flush 'm
+       \dostoptagged
+       \strc_sectioning_after_nop
+     \fi
+   \fi
+   %
+   \the\everyaftersectionheadhandle
+   %
+   \setfalse\c_strc_sectioning_ignore_page
+   % ignorespaces prevents spaces creeping in when after=\dontleavehmode
+   \dostarttagged\t!sectioncontent\empty
+   \ifempty\currentstructureplaceholder
+      \ifconditional\headisdisplay
+        \doubleexpandafter\ignorespaces
+      \else
+        \doubleexpandafter\ignorepars
+      \fi
+   \else
+      \expandafter\strc_sectioning_placeholder
+   \fi}
+
+%D \starttyping
+%D \startsubject[placeholder=todo,title=one]
+%D     whatever one
+%D \stopsubject
+%D \stoptyping
+
+\def\strc_sectioning_placeholder
+  {\placeholder[\currentstructureplaceholder]%
+   \gobblenested{\e!start\currenthead}{\e!stop\currenthead}{\e!stop\currenthead}}
+
+% typesetting (the getters are public)
+
+\protected\def\strc_rendering_place_head_number_and_text
+  {\setheadmarking
+   \getheadnumber/\getheadtitle
+   \getheadsyncs}
+
+\protected\def\strc_rendering_place_head_text
+  {\setheadmarking
+   \getheadtitle
+   \getheadsyncs}
+
+\protected\def\strc_rendering_place_head_empty
+  {\setheadmarking
+   \getheadsyncs}
+
+\installcorenamespace{hiddenheadattr}
+\installcorenamespace{hiddenheadsync}
+
+% todo: when in the page builder we need to resolve the marking immediately
+% because otherwise we have an async
+
+\newbox\b_sectioning_delayed
+
+\def\strc_sectioning_delayed_flush
+  {\ifvoid\b_sectioning_delayed\else
+     \smashedbox\b_sectioning_delayed
+   \fi}
+
+\protected\def\strc_rendering_place_head_section % see hidden below
+  {\global\setbox\b_sectioning_delayed\hpack\bgroup
+     \setmarking[\currentheadcoupling]{li::\currentstructurelistnumber}%
+     \hpack\headreferenceattributes{}% also does the mark
+     \theheadsynchonization
+   \egroup}
+
+\protected\def\strc_rendering_place_head_hidden % maybe trialtypesetting check
+  {\xdefcsname\??hiddenheadattr\currenthead\endcsname
+     {\headreferenceattributes}% can be used when making a box
+   \xdefcsname\??hiddenheadsync\currenthead\endcsname
+     {\noexpand\letgvalue{\??hiddenheadsync\currenthead}\relax
+      \noexpand\setmarking[\currentheadcoupling]{li::\currentstructurelistnumber}%
+      \hpack\headreferenceattributes{}% otherwise no destination ... maybe tag ref as hidden and fall back on page reference
+      \theheadsynchonization}} % and it's a node anyway
+
+\permanent\def\synchronizehead           #1{\begincsname\??hiddenheadsync#1\endcsname}
+\permanent\def\theheadreferenceattributes#1{\begincsname\??hiddenheadattr#1\endcsname}
+
+\permanent\protected\def\placerawheaddata  [#1]{\synchronizehead{#1}}
+\permanent\protected\def\placerawheadtext  [#1]{\getspecificstructuretitle{\thenamedheadlevel{#1}}}
+\permanent\protected\def\placerawheadnumber[#1]{\getfullstructurenumber{\thenamedheadlevel{#1}}}
+
+\permanent\protected\def\repeathead[#1]%
+  {\begingroup
+   \setupinteraction[\c!state=\v!stop]%
+   \def\currenthead{#1}
+   \strc_sectioning_initialize_placement
+   \strc_sectioning_initialize_number
+   \dostarttagged\t!sectioncaption\empty
+   \let\getheadsyncs \relax
+   \def\getheadtitle {\getmarking[#1]}
+   \def\getheadnumber{\getmarking[#1\v!number]}
+   \strc_sectioning_before_yes
+   \ifconditional\headshownumber
+      \strc_rendering_place_head_number_and_text
+   \else
+      \strc_rendering_place_head_text
+   \fi
+   \dostoptagged
+   \strc_sectioning_after_yes
+   \endgroup}
+
+% \setuphead[chapter][placehead=hidden]
+% \chapter {test}
+%
+% %(\synchronizehead{chapter}) % \getheadsyncs
+% %(\getfullstructurenumber{\thenamedheadlevel{chapter}})
+% %(\getspecificstructuretitle{\thenamedheadlevel{chapter}})
+%
+% (\placerawheaddata  [chapter])
+% (\placerawheadnumber[chapter])
+% (\placerawheadtext  [chapter])
+
+% pagebreaks
+
+\letvalue{\??headmarknop\v!page   }\donothing
+\setvalue{\??headmarknop\v!reset  }{\resetcurrentstructuremarks}
+\letvalue{\??headmarknop\s!unknown}\donothing
+
+\letvalue{\??headmarkyes\v!page   }\donothing  % to be checked: {\resetcurrentstructuremarks}
+\setvalue{\??headmarkyes\v!reset  }{\resetcurrentstructuremarks}
+\letvalue{\??headmarkyes\s!unknown}\donothing
+
+\def\strc_sectioning_check_layout
+  {\edef\p_page{\headparameter\c!page}%
+   \ifempty\p_page
+     \strc_sectioning_check_layout_nop
+   \else
+     \strc_sectioning_check_layout_yes
+   \fi}
+
+\def\strc_sectioning_check_layout_nop
+  {\expandnamespaceparameter\??headmarknop\headparameter\c!marking\s!unknown}
+
+\def\strc_sectioning_check_layout_yes
+  {\page[\p_page]%
+   \expandnamespaceparameter\??headmarkyes\headparameter\c!marking\s!unknown
+   \edef\p_header{\headparameter\c!header}%
+   \ifempty\p_header \else
+     \doifelselayouttextline\v!header{\normalexpanded{\setuplayouttext[\v!header][\c!state=\p_header]}}\donothing
+   \fi
+   \edef\p_text{\headparameter\c!text}%
+   \ifempty\p_text \else
+     \doifelselayouttextline\v!text  {\normalexpanded{\setuplayouttext[\v!text  ][\c!state=\p_text  ]}}\donothing
+   \fi
+   \edef\p_footer{\headparameter\c!footer}%
+   \ifempty\p_footer \else
+     \doifelselayouttextline\v!footer{\normalexpanded{\setuplayouttext[\v!footer][\c!state=\p_footer]}}\donothing
+   \fi}
+
+\newcount      \c_strc_sectioning_preceding_level     \c_strc_sectioning_preceding_level\plusone
+\newconditional\c_strc_sectioning_auto_break          \settrue\c_strc_sectioning_auto_break
+\newconditional\c_strc_sectioning_ignore_page
+\newsignal     \d_strc_sectioning_continuous_signal
+
+\protected\def\strc_sectioning_inject_continuous_signal
+  {\ifhmode
+     \hskip\d_strc_sectioning_continuous_signal\relax
+   \fi}
+
+% \let\dotagsectionlevel\relax
+
+\def\strc_sectioning_before_yes
+  {\strc_sectioning_check_before\strc_sectioning_handle_page_yes
+   \headparameter\c!inbetween
+   \dostarttaggedchained\t!section\currenthead\??head
+%    \dotagsectionlevel
+   }
+
+\def\strc_sectioning_before_nop
+  {\strc_sectioning_check_before\strc_sectioning_handle_page_nop
+   \headparameter\c!inbetween
+   \dostarttagged\currenthead\empty} % this is a weird one .. needs checking
+
+\def\strc_sectioning_empty_correction
+  {\ifconditional\c_strc_sectioning_empty
+     % this needs checking
+     \penalty\plustenthousand
+     \vskip-\lineheight
+     \kern\zeropoint
+     \prevdepth\strutdepth
+   \fi}
+
+\def\strc_sectioning_after_nop
+  {}
+
+\def\strc_sectioning_check_before#1%
+  {\ifhmode
+     \scratchcounter\lastpenalty
+     \unpenalty % no beauty in this
+     \ifdim\lastskip=\d_strc_sectioning_continuous_signal
+       % no page break
+       \ifconditional\c_strc_sectioning_ignore_page
+         \setfalse\c_strc_sectioning_ignore_page
+       \else
+         \global\c_strc_sectioning_preceding_level\currentheadlevel
+         \nobreak
+       \fi
+     % \global\settrue\c_strc_rendering_continuous
+     \else
+       \penalty\scratchcounter
+     % \global\setfalse\c_strc_rendering_continuous
+       #1%
+     \fi
+   \else
+   % \global\setfalse\c_strc_rendering_continuous
+     #1%
+   \fi}
+
+%permanent\def\currentsectioncountervalue {\clf_depthnumber\numexpr\thenamedheadlevel\currenthead\relax}
+%permanent\def\previoussectioncountervalue{\clf_depthnumber\numexpr\thenamedheadlevel\currenthead+\minusone\relax}
+
+\permanent\def\currentsectioncountervalue {\clf_depthnumber\numexpr\thenamedheadlevel\currenthead\relax}
+%permanent\def\previoussectioncountervalue{\clf_depthnumber\numexpr\thenamedheadlevel\currenthead+\minusone\relax}
+\permanent\def\previoussectioncountervalue{\clf_depthnumber\numexpr\thenamedheadlevel\previoushead\relax}
+
+\let\previoushead\empty
+
+\def\strc_sectioning_handle_page_nop
+  {\edef\p_continue{\headparameter\c!continue}%
+   \ifx\p_continue\v!yes
+     \ifx\currenthead\previoushead % not really needed
+        \strc_sectioning_check_layout
+     \orelse\ifnum\previoussectioncountervalue=\zerocount
+        \strc_sectioning_check_layout
+     \orelse\ifnum\currentsectioncountervalue>\zerocount
+        \strc_sectioning_check_layout
+     \fi
+   \else
+     \strc_sectioning_check_layout
+   \fi
+   \glet\previoushead\currenthead}
+
+
+\def\strc_sectioning_handle_page_yes
+  {\ifconditional\c_strc_sectioning_ignore_page
+     \setfalse\c_strc_sectioning_ignore_page
+   \else
+     % beware, these numbers are not yet know here
+     \strc_sectioning_handle_page_nop
+     \edef\p_aligntitle{\headparameter\c!aligntitle}%
+     \ifx\p_aligntitle\v!float
+         \ifconditional\c_strc_sectioning_auto_break
+           \spac_vspacing_same_page\currentheadlevel\zerocount
+         \fi
+         \headparameter\c!before\relax
+         \indent
+     \else
+         \page_otr_command_flush_side_floats
+         \ifconditional\c_strc_sectioning_auto_break
+           \spac_vspacing_same_page\currentheadlevel\zerocount
+         \fi
+         \headparameter\c!before\relax
+     \fi
+     \global\c_strc_sectioning_preceding_level\currentheadlevel
+   \fi
+   \glet\previoushead\currenthead}
+
+\def\strc_sectioning_depth_correction
+  {\ifvmode
+     \edef\p_depthcorrection{\headparameter\c!depthcorrection}%
+     \ifx\p_depthcorrection\v!strut
+       \prevdepth\strutdepth
+     \fi
+   \fi}
+
+\def\strc_sectioning_after_yes
+  {\ifconditional\headisdisplay
+     \ifconditional\c_strc_sectioning_auto_break
+       \spac_vspacing_same_page\currentheadlevel\plusone
+     \fi
+     \strc_sectioning_empty_correction
+     \headparameter\c!after
+     \strc_sectioning_depth_correction
+   \fi}
+
+\protected\def\strc_sectioning_prevent_page_break % see strc-con
+  {\ifconditional\c_strc_sectioning_auto_break
+     \spac_vspacing_same_page\currentheadlevel\plustwo
+   \fi}
+
+
+% We do support negative numbers but it can have side effects that we won't catch:
+%
+% \chapter{some} \setupheadnumber[chapter][3] \chapter{more}
+% \setupheadnumber[section][8] \section{b} \section{c} \setupheadnumber[section][-1] \section{d}
+
+\permanent\def\thenamedheadlevel#1%
+  {\sectionlevel{\sectionheadsection{\sectionheadcoupling{#1}}}}
+
+\permanent\tolerant\protected\def\setupheadnumber[#1]#*[#2]% todo: reset if at other level
+  {\setstructurenumber{\thenamedheadlevel{#1}}{\number#2}}
+
+\def\currentheadnumber{0} % ==> \currentheadnumber
+
+\permanent\protected\def\determineheadnumber[#1]%
+  {\xdef\currentheadnumber{\getstructurenumber{\thenamedheadlevel{#1}}}}
+
+% The previous macro is been replaced by the expandable:
+
+\permanent\def\namedheadnumber      #1{\getstructurenumber    {\thenamedheadlevel{#1}}}
+\permanent\def\somenamedheadnumber#1#2{\getsomestructurenumber{\thenamedheadlevel{#1}}{#2}}
+
+\permanent\tolerant\protected\def\headnumber[#1]#*[#2]% simple case is just a number
+  {\getsomefullstructurenumber{\ifparameter#1\or\thenamedheadlevel{#1}\fi}{#2}}
+
+\permanent\tolerant\protected\def\someheadnumber[#1]#*[#2]%
+  {\dontleavehmode
+   \begingroup
+   \edef\currenthead{#1}%
+   \getsomefullstructurenumber{\thenamedheadlevel{#1}}{#2}%
+   \endgroup}
+
+\aliased\let\sectioncountervalue\structurevalue
+
+\def\currentheadtext{obsolete,\space use marks}
+
+% list references, will be redone in lua when we need it
+
+\let\startlistreferences\relax
+\let\stoplistreferences \relax
+
+% experimental
+
+\newconditional\c_strc_sectioning_auto_levels
+
+\appendtoks
+    \settrue\c_strc_sectioning_auto_levels
+\to \everyenableelements
+
+\protected\def\strc_sectioning_initialize_autolevel
+  {\ifconditional\c_strc_sectioning_auto_levels
+     \clf_autonextstructurelevel\currentheadlevel\relax
+     \global\setfalse\c_strc_sectioning_auto_levels
+   \fi}
+
+\permanent\protected\def\triggerautostructurelevel
+  {\global\settrue\c_strc_sectioning_auto_levels}
+
+\permanent\protected\def\finalizeautostructurelevels
+  {\clf_autofinishstructurelevels}
+
+\permanent\protected\def\finalizeautostructurelevel
+  {\dostoptagged
+   \dostoptagged}
+
+\appendtoks
+    \finalizeautostructurelevels
+\to \everystoptext
+
+\stopcontextdefinitioncode
+
+\protect \endinput