%D \module
%D   [       file=strc-ren,
%D        version=2008.10.20,
%D          title=\CONTEXT\ Structure Macros,
%D       subtitle=Section Rendering,
%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.

\writestatus{loading}{ConTeXt Structure Macros / Section Rendering}

\unprotect

\newconstant\headtimingmode

% Martin Kolarik's problem:
%
% \setuphead[section][command=\doTitle]
% \def\doTitle#1#2{\ruledvbox{\forgetall \hsize=4cm \ruledhbox{\ruledvtop{#1}\ruledvtop{#2}}}}
% \section{test test test test test test test test test test test test test test test test test}

\newevery \everyheadstart \relax

\unexpanded\def\setupheadcomponentfont#1#2%
  {\dontconvertfont
   \ifconditional\headisdisplay
     \edef\askedheadinterlinespace{\headparameter\c!interlinespace}%
     \ifx\askedheadinterlinespace\empty
       % here the interline space is only set when style sets no space
       \setfalse\fontattributeisset % use the currentfontparameter state instead
       \setfalse\interlinespaceisset
       \useheadstyleandcolor\c!style\c!color
       \ifconditional\fontattributeisset \ifconditional\interlinespaceisset \else
         \setupinterlinespace
       \fi \fi
       \setfalse\fontattributeisset \useheadstyleandcolor#1#2%
       \ifconditional\fontattributeisset \ifconditional\interlinespaceisset \else
         \setupinterlinespace
       \fi \fi
     \else
       % here the set interline space overloads any other set space in the style
       \setfalse\fontattributeisset
       \useheadstyleandcolor\c!style\c!color
       \ifconditional\fontattributeisset
         \dosetupcheckedinterlinespace\askedheadinterlinespace
       \fi
       \setfalse\fontattributeisset
       \useheadstyleandcolor#1#2%
       \ifconditional\fontattributeisset
         \dosetupcheckedinterlinespace\askedheadinterlinespace
       \fi
     \fi
   \else
     \setfalse\fontattributeisset
     \useheadstyleandcolor\c!style\c!color
     \ifconditional\fontattributeisset
       \setupspacing
     \fi
     \setfalse\fontattributeisset
     \useheadstyleandcolor#1#2%
     \ifconditional\fontattributeisset
       \setupspacing
     \fi
   \fi}

\def\doplaceheadtextcomponent#1%
  {\begingroup
     \setupheadcomponentfont\c!textstyle\c!textcolor
     \headparameter\c!commandbefore
     \ifcsname\currentheadhash\c!deeptextcommand\endcsname
       \expandafter\let\expandafter\deepstructuretitlecommand\csname\currentheadhash\c!deeptextcommand\endcsname
     \fi
     \ifconditional\headisdisplay % \ifdisplaysectionhead
       % struts can be nilled with \setnostrut
       \headparameter\c!textcommand{\setstrut\begstrut#1\endstrut}%
       \xdef\localheadheight    {\the\strutht}%
       \xdef\localheaddepth     {\the\strutdp}%
       \xdef\localheadlineheight{\the\lineheight}%
       % == \globallet\localheaddepth\strutdepth
     \else
       \headparameter\c!textcommand{#1}%
     \fi
     \headparameter\c!commandafter
     \ifconditional\headisdisplay % \ifdisplaysectionhead
       \endgraf
     \fi
   \endgroup}

\def\doplaceheadnumbercomponent#1%
  {\begingroup
     \setupheadcomponentfont\c!numberstyle\c!numbercolor
     \ifcsname\currentheadhash\c!deepnumbercommand\endcsname
       \expandafter\let\expandafter\deepstructurenumbercommand\csname\currentheadhash\c!deepnumbercommand\endcsname
     \fi
     \ifconditional\headisdisplay % \ifdisplaysectionhead
       % can be nilled with \setnostrut
       \headparameter\c!numbercommand{\setstrut\begstrut#1\endstrut}%
     \else
       \headparameter\c!numbercommand{#1}%
     \fi
   \endgroup}

% \newif\ifheadnumbercontent
% \newif\ifemptyhead
% \newif\ifdisplaysectionhead

\let\currentstructurereferenceattribute\attributeunsetvalue

\def\headreferenceattributes
  {\iflocation
   % \ctxlua{structures.lists.taglocation(\nextinternalreference)}% maybe ... tags entry as used
     attr \destinationattribute \currentstructureattribute
     attr \referenceattribute   \currentstructurereferenceattribute
   % attr \internalattribute    \nextinternalreference
   \fi}

\def\setinlineheadreferenceattributes
  {\ifconditional\headisdisplay \else \iflocation
     \attribute\destinationattribute\currentstructureattribute
     \attribute\referenceattribute  \currentstructurereferenceattribute
   % \attribute\internalattribute   \nextinternalreference
   \fi \fi}

\def\docheckheadreference
  {\edef\currentheadinteraction{\headparameter\c!interaction}%
   \ifx\currentheadinteraction\v!list
     % setuphead[<section>][interaction=list,...]
     \strc_references_get_simple_page_reference{bck:\nextinternalreference}%
     \let\currentstructurereferenceattribute\currentreferenceattribute
   \else\ifx\currentheadinteraction\v!reference
     % setuphead[<section>][interaction=reference,...] start<section>[backreference=abc,...]
     \edef\currentheadbackreference{\structurevariable\c!backreference}% weird, was references.backreference
     \ifx\currentheadbackreference\empty \else
       \strc_references_get_simple_page_reference\currentheadbackreference
       \let\currentstructurereferenceattribute\currentreferenceattribute
     \fi
   \else
      % maybe auto: backreference when given, else list
   \fi\fi}

\unexpanded\def\placecurrentheadtext
  {\beginheadplacement
   \setheadmarking
   \doresettructureheadnumbercontent
   \ifconditional\headleaveempty
     \setbox\sectionheadbox\hbox \headreferenceattributes to \zeropoint{}%
     \makestrutofbox\sectionheadbox
   \else
     \docheckheadreference
     \setbox\sectionheadbox\hbox \headreferenceattributes
       {\spac_grids_set_local_snapping{\headparameter\c!internalgrid}%
        \doresettructureheadnumbercontent
        \useheadstyleparameter\c!style
        \setinlineheadreferenceattributes
        \headparameter\c!command{}{\doplaceheadtextcomponent\getheadtitle}}%
   \fi
   \endheadplacement{\getheadsyncs}}

\unexpanded\def\placecurrentheadnumbertext
  {\beginheadplacement
   \setheadmarking
   \doiftextelse{\getheadnumber}\dosettructureheadnumbercontent\doresettructureheadnumbercontent
   \ifconditional\headleaveempty
     \setbox\sectionheadbox\hbox \headreferenceattributes to \zeropoint{}%
     \makestrutofbox\sectionheadbox
   \else % = needed
     \docheckheadreference
     \setbox\sectionheadbox\hbox \headreferenceattributes
       {\spac_grids_set_local_snapping{\headparameter\c!internalgrid}%
        \useheadstyleparameter\c!style
        \setinlineheadreferenceattributes
        \headparameter\c!command{\doplaceheadnumbercomponent\getheadnumber}{\doplaceheadtextcomponent\getheadtitle}}%
   \fi
   \endheadplacement{\getheadsyncs}}

\unexpanded\def\placecurrentheadempty
  {\hbox \headreferenceattributes {\getheadsyncs}}

%D \starttyping
%D \def\StretchedBox#1%
%D   {\framed
%D      [frame=off,offset=.5em,align=middle,width=broad]
%D      {\sc\def\stretchedspaceamount{.3em}\stretchednormalcase{#1}}}
%D
%D \definehead[MySubject][subject]
%D \setuphead [MySubject][deeptextcommand=\StretchedBox]
%D
%D \MySubject{feeling stretched feeling stretched feeling stretched feeling stretched}
%D \stoptyping

\let\headlastlinewidth\!!zeropoint

\def\localheadheight    {\strutht}
\def\localheaddepth     {\strutdp}
\def\localheadlineheight{\lineheight}

\def\dolocalheadsetup  %  koppeling met standaard kopcommando / engels
  {\forgetall          %  traag dus ...
   \doifsomething{\headparameter\c!align    }     {\normalexpanded{\noexpand\setupalign    [\headparameter\c!align    ]}}%
   \doifsomething{\headparameter\c!tolerance}     {\normalexpanded{\noexpand\setuptolerance[\headparameter\c!tolerance]}}%
   \doif         {\headparameter\c!strut    }\v!no{\setnostrut}% new
   \def\\{\crlf\strut\ignorespaces}}

\def\beginheadplacement
  {\bgroup
   \setsystemmode\currenthead
   \xdef\localheadheight    {\the\strutht}%
   \xdef\localheaddepth     {\the\strutdp}%
   \xdef\localheadlineheight{\the\lineheight}%
   % == \globallet\localheaddepth\strutdp
   \everypar\emptytoks % needed indeed
   \noindent           % ipv \whitespace elders, na \forgetall !
   \bgroup
   \doifinsetelse{\headparameter\c!aligntitle}{\v!yes,\v!float}% new
     {\skip0 1\leftskip
      \skip2 1\rightskip
      \xdef\localheadskip{\the\skip0}%
      \forgetall
      \leftskip\skip0
      \rightskip\skip2
      \setlocalhsize\hsize\localhsize
      \forgetbothskips}
     {\globallet\localheadskip\!!zeropoint
      \forgetall}%
   \setfalse\inhibitmargindata % brrrr is set in forgetall
   \dontcomplain
   \postponenotes
   \iflocation
     \ifconditional\headisdisplay % \ifdisplaysectionhead
     \else
       % obsolete: \noninterferingmarks
     \fi
   \fi
   \resetinteractionparameter\c!style
   \resetinteractionparameter\c!color
   \resetinteractionparameter\c!contrastcolor
   %\strictouterreferencestrue % tzt instelling
   \let\localheadsetup\dolocalheadsetup}

% \setuphead[chapter]         [style=\bfd,after=,hang=line] % fit broad 2
% \setuphead[section]         [style=\bfc,after=,hang=line]
% \setuphead[subsection]      [style=\bfb,after=,hang=line]
% \setuphead[subsubsection]   [style=\bfa,after=,hang=line]
% \setuphead[subsubsubsection][style=\bf ,after=,hang=line]
%
% \chapter         {Test} \input tufte \page
% \section         {Test} \input tufte \page
% \subsection      {Test} \input tufte \page
% \subsubsection   {Test} \input tufte \page
% \subsubsubsection{Test} \input tufte \page
%
% \chapter         {Test\\Test} \input tufte \page
% \section         {Test\\Test} \input tufte \page
% \subsection      {Test\\Test} \input tufte \page
% \subsubsection   {Test\\Test} \input tufte \page
% \subsubsubsection{Test\\Test} \input tufte \page

\def\hangheadplacement
  {\scratchdimen\localheadlineheight
   \bgroup
   \openlineheight\scratchdimen
   \scratchdimen\htdp0%
   \getnoflines\scratchdimen
   \advance\noflines\minusone
   \normalexpanded{\egroup\noflines\the\noflines}% brrr
   \setbox0\hbox{\lower\noflines\scratchdimen\box0}%
   \scratchdimen\dimexpr\htdp0-\localheadheight+\strutdp\relax
   \ht0 \strutht
   \dp0 \strutdp
   \edef\localheaddepth{\the\strutdp}}

\newconditional\continuoussectionhead % oeps, \newif\ifcontinuoushead got lost
\newbox\sectionheadbox

\def\endheadplacement#1%
  {\noflines\zerocount
   \ifconditional\headisdisplay % \ifdisplaysectionhead
     % new (todo tight == one following line up)
     \processaction
       [\headparameter\c!hang]
       [    \v!line=>\hangheadplacement\noflines\zerocount,
           \v!broad=>\hangheadplacement\getnoflines\scratchdimen,
             \v!fit=>\hangheadplacement\getrawnoflines\scratchdimen,
            \v!none=>\noflines\zerocount,
         \v!default=>\noflines\zerocount,
         \v!unknown=>\hangheadplacement\noflines\numexpr0\commalistelement-1\relax]%
     % so far
     \let\headlastlinewidth\!!zeropoint
     % kind of special, we want to snap heads also according to local specs local
     \ifgridsnapping
       \hbox\bgroup % extra hbox will trigger global snapper on top of local
         \edef\currentheadgridsnapping{\headparameter\c!grid}%
         \ifconditional\headisdisplay
           \ifx\currentheadgridsnapping\empty\else
             \useheadstyleandcolor\c!style\c!color
             \setupinterlinespace
             \useheadstyleandcolor\c!textstyle\c!textcolor
             \setupinterlinespace
           \fi
         \fi
         \snaptogrid[\currentheadgridsnapping]\hbox
           {\hskip\localheadskip\hskip\headparameter\c!margin\box\sectionheadbox}%
       \egroup
     \else
       \hbox
         {\hskip\localheadskip\hskip\headparameter\c!margin\box\sectionheadbox}%
     \fi
     \flushnotes % new, not really needed
     \endgraf
     \ifvmode
       \ifnum\noflines>\zerocount
         \dorecurse\noflines{\nointerlineskip\dosomebreak\nobreak\strut\endgraf}% to be checked
       \fi
       \nointerlineskip
       \dosomebreak\nobreak
     \fi
     #1%
   \else
     \strut
     \flushnotes % new, here since we're in par mode
     \unhbox\sectionheadbox
     \globallet\headlastlinewidth\!!zeropoint
     #1%
     \hskip\numberheaddistance\!!plus\numberheaddistance\!!minus.25\dimexpr\numberheaddistance\relax
     \hskip\continuousheadsignal\ignorespaces
   \fi
   \ifconditional\headisdisplay % \ifdisplaysectionhead
     \ifvmode
       \ifgridsnapping % important, font related depth, see comment
         \prevdepth\strutdp
       \else
         \prevdepth\localheaddepth
       \fi
     \fi
   \fi
   \egroup
   \egroup
   \ifconditional\headisdisplay % \ifdisplaysectionhead
     \useindentnextparameter\headparameter
   \else
     \nonoindentation % recently added, was a bug
   \fi}

% nice testcase
%
% \setupheads[aligntitle=yes]
%
% \startnarrower
%   \subject{\dorecurse{100}{x }}
%   \section{\dorecurse{100}{x }}
%   \input tufte \par
%   \setupheads[alternative=inmargin]
%   \subject{\dorecurse{100}{x }}
%   \section{\dorecurse{100}{x }}
%   \input tufte \par
% \stopnarrower

\installcorenamespace{headplacementalternative}
\installcorenamespace{headplacementnature}

\let\numberheadalternative\v!normal

\unexpanded\def\defineheadplacement
  {\dodoubleargument\dodefineheadplacement}

% \def\dodefineheadplacement[#1][#2]% #3#4
%   {\setvalue{\??headplacementnature#1}{#2}%
%    \setvalue{\??headplacementalternative#1}}

% \dodefineheadplacement[sectiona][vertical]{#1->#2}
% \dodefineheadplacement[sectionb][vertical]#1#2{#1->#2}
%
% \setuphead[section][alternative=sectiona]
% \setuphead[subsection][alternative=sectionb]

\def\dodefineheadplacementyes[#1][#2]%#3#4%
  {\setvalue{\??headplacementnature#1}{#2}%
   \setvalue{\??headplacementalternative#1}##1##2}

\def\dodefineheadplacementnop[#1][#2]%
  {\setvalue{\??headplacementnature#1}{#2}%
   \setvalue{\??headplacementalternative#1}}

\def\dodefineheadplacement[#1][#2]%
  {\doifnextbgroupelse
     {\dodefineheadplacementyes[#1][#2]}%
     {\dodefineheadplacementnop[#1][#2]}}

\def\presetnumberheadalternative
  {\doifelsevalue{\??headplacementnature\numberheadalternative}\v!horizontal\setfalse\settrue\headisdisplay}

\def\normalplacehead
  {\csname\??headplacementalternative\ifcsname\??headplacementalternative\numberheadalternative\endcsname\numberheadalternative\else\v!normal\fi\endcsname}

\def\setheaddisplay % used in strc-sec
  {\doifelsevalue{\??headplacementnature\headparameter\c!alternative}\v!horizontal
     {\setfalse\headisdisplay}
     {\settrue \headisdisplay}}

\defineheadplacement[\v!paragraph][\v!vertical]#1#2%
  {\vbox
     {\localheadsetup
      \begstrut
      \ifconditional\headshownumber % \ifheadnumbercontent
        #1\hskip\numberheaddistance
      \fi
      #2}}

% \setuphead
%   [chapter]
%   [numberwidth=2cm,hang=line,after={\blank[3*line]}]
%
% \chapter{Oeps oeps oeps} \input tufte   \section{Oeps}
% \chapter{Oeps oeps oeps} \section{Oeps} \input tufte

\defineheadplacement[\v!normal][\v!vertical]#1#2%
  {\vbox
     {\localheadsetup
      \edef\headwidth      {\headparameter\c!width      }%
      \edef\headnumberwidth{\headparameter\c!numberwidth}%
      \edef\headtextwidth  {\headparameter\c!textwidth  }%
      \ifconditional\headshownumber
        \ifx\headwidth\empty
        \else
          \ifx\headnumberwidth\empty
            \ifx\headtextwidth\empty\else
              \edef\headnumberwidth{\the\dimexpr\headwidth-\headtextwidth\relax}%
            \fi
          \else
            \ifx\headtextwidth\empty
              \edef\headtextwidth{\the\dimexpr\headwidth-\headnumberwidth\relax}%
            \fi
          \fi
          \hsize\headwidth
        \fi
        \ifx\headnumberwidth\empty\else
          \let\numberheaddistance\!!zeropoint
        \fi
        \setbox\scratchbox\hbox \ifx\headnumberwidth\empty\else to \headnumberwidth\fi{{#1}}%
        \scratchdimen\dimexpr\wd\scratchbox+\numberheaddistance\relax
        \ifx\headtextwidth\empty\else
          \hsize\dimexpr\scratchdimen+\headparameter\c!textwidth\relax
        \fi
        \hangindent\scratchdimen
        \hangafter \plusone
        \noindent
        \box\scratchbox\hskip\numberheaddistance
      \else
        \ifx\headtextwidth\empty
          \ifx\headwidth\empty
          \else
            \hsize\headwidth
          \fi
        \else
          \hsize\headtextwidth
        \fi
        \noindent
      \fi
      #2}}

% \unexpanded\def\placeheadmarginalternative#1#2%
%   {\vbox
%      {\localheadsetup
%       \begstrut % use one \strut here!
%       \dontleavehmode % in case there is no strut, else side effects with llap
%       \ifconditional\headshownumber
%         \llap{\hbox{\hfill{#1}\hskip\localheadskip\hskip\leftmargindistance}}% introduces whitespace
%         % maybe better:
%         % \inleftmargin{\hbox{\hss{#1}\hskip\localheadskip}}%
%       \fi
%       {#2}}}

\unexpanded\def\placeheadmarginalternative#1#2%
 {\vbox
    {\localheadsetup
     \begstrut % use one \strut here!
     \dontleavehmode % in case there is no strut, else side effects with llap
     \ifconditional\headshownumber
       \llap{\hbox{\hfill{#1}\hskip\dimexpr\localheadskip+\doifoddpageelse\leftmargindistance\rightmargindistance\relax}}% introduces whitespace
     \fi
     {#2}}}

\defineheadplacement[\v!inmargin][\v!vertical]#1#2{\placeheadmarginalternative{#1}{#2}}
\defineheadplacement[\v!margin]  [\v!vertical]#1#2{\placeheadmarginalternative{#1}{#2}}

\defineheadplacement[\v!middle][\v!vertical]#1#2%
  {\vbox
     {\localheadsetup
      \veryraggedcenter
      \let\\\endgraf
      \let\crlf\endgraf
      \ifconditional\headshownumber
        \strut#1\par
      \fi
      \begstrut#2}}

\defineheadplacement[\v!text][\v!horizontal]#1#2%
  {\bgroup
   \localheadsetup % no stretch in distance
   \ifconditional\headshownumber
     {#1}\kern\numberheaddistance
   \fi
   {\begstrut#2}%
   \egroup}

\unexpanded\def\placeheadlohialternative#1#2#3%
  {\ifconditional\headshownumber
     \setbox0\hbox{#2}
     \setbox2=#1{\localheadsetup\advance\hsize-\wd0\relax#3}%
     \hbox{\box0\hskip\numberheaddistance\box2}%
   \else
     #1{\localheadsetup\noindent#3}%
   \fi}

% onder/boven lijnt het nummer op de onderste/bovenste regel
% uit van een meerregelige kop

\defineheadplacement[\v!bottom][\v!vertical]#1#2{\placeheadlohialternative\vbox{#1}{#2}}
\defineheadplacement[\v!top]   [\v!vertical]#1#2{\placeheadlohialternative\vtop{#1}{#2}}

% helpers

% \defineinmargin [ChapterInMargin] [outer] [normal] [distance=0.3em]
%
% \defineheadplacement[MyTest][horizontal]#1#2%
%   {\startlocalheadsetup
%   %\ChapterInMargin{\headhbox{\strut#2}}% proper destination, ref okay
%    \ChapterInMargin{\strut#2}% zero destination, ref okay
%    \stoplocalheadsetup}
%
% \setuphead
%   [chapter]
%   [alternative=MyTest]

\unexpanded\def\headhbox{\hbox\headreferenceattributes}
\unexpanded\def\headvbox{\vbox\headreferenceattributes}

\unexpanded\def\startlocalheadsetup{\bgroup\localheadsetup}
\unexpanded\def\stoplocalheadsetup {\egroup}

\protect \endinput