%D \module
%D   [       file=spac-par,
%D        version=2009.10.16, % 1997.03.31, was core-spa.tex
%D          title=\CONTEXT\ Spacing Macros,
%D       subtitle=Paragraphs,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA / Hans Hagen \& Ton Otten}]
%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 Spacing Macros / Paragraphs}

\unprotect

%D The dreadful sequence \type {\bgroup} \unknown\
%D \type {\carryoverpar} \unknown\ \type {\egroup} is needed
%D when for instance sidefloats are used in combination with
%D something that starts with a group. This is because
%D otherwise the indentation as set (by the output routine)
%D inside the group are forgotten afterwards. (I must
%D not forget its existence).

\global\let\carriedoverpar\relax

\def\carryoverpar#1%
  {\normalexpanded     % \scratchtoks{#1}%
     {\noexpand#1% \the\scratchtoks
      \hangindent\the\hangindent
      \hangafter \the\hangafter
      \parskip   \the\parskip
      \leftskip  \the\leftskip
      \rightskip \the\rightskip}}

\newconditional \parbasedattributes

\def\finishparbasedattributes
  {\ifconditional\parbasedattributes
     \setfalse\parbasedattributes
     \par
   \fi}

\def\dostopparbasedattributes
  {\settrue\parbasedattributes
   \dostopattributes}

% beware, changing this will break some code (like pos/backgrounds)

\newtoks\everyfirstparagraphintro
\newtoks\everynextparagraphintro
\newtoks\@@everyparagraphtoks

\chardef\everyparagraphintro\zerocount

\unexpanded\def\setupparagraphintro
  {\dodoubleempty\dosetupparagraphintro}

\def\dosetupparagraphintro[#1][#2]%
  {\processallactionsinset
     [#1]
     [   \v!reset=>\global\chardef\everyparagraphintro\zerocount
                   \global\everyfirstparagraphintro\emptytoks
                   \global\everynextparagraphintro \emptytoks,
         \v!first=>\global\chardef\everyparagraphintro\plusone
                   \doglobal\appendtoks#2\to\everyfirstparagraphintro,
          \v!next=>\ifcase\everyparagraphintro\global\chardef\everyparagraphintro\plusone\fi
                   \doglobal\appendtoks#2\to\everynextparagraphintro,
          \v!each=>\ifcase\everyparagraphintro\global\chardef\everyparagraphintro\plustwo\fi
                   \doglobal\appendtoks#2\to\everyfirstparagraphintro
                   \doglobal\appendtoks#2\to\everynextparagraphintro]}

%D We can say:
%D
%D \starttyping
%D \setupparagraphintro[first][\index{Knuth}]
%D \stoptyping
%D
%D Maybe more convenient is:
%D
%D \starttyping
%D \flushatparagraph{\index{Zapf}}
%D \stoptyping

\def\flushatparagraph#1%
  {\global\chardef\everyparagraphintro\plusone
   \global\appendtoks{#1}\to\everyfirstparagraphintro
   \global\let\insertparagraphintro\doinsertparagraphintro}

\def\doinsertparagraphintro % can be merged with the next
  {\ifcase\everyparagraphintro\else\@EA\dodoinsertparagraphintro\fi}

\def\dodoinsertparagraphintro
  {\begingroup
   \everypar\emptytoks
   \ifcase\everyparagraphintro\relax
     % no data
     \@@everyparagraphtoks\emptytoks
   \or
     % first data
     \global\chardef\everyparagraphintro\plustwo
     \@@everyparagraphtoks\everyfirstparagraphintro
     \global\everyfirstparagraphintro\emptytoks
   \or
     % next data
     \@@everyparagraphtoks\everynextparagraphintro
   \fi
   \the\@@everyparagraphtoks
   \global\let\insertparagraphintro\relax
   \endgroup}

\let\insertparagraphintro\relax

%D \starttyping
%D \setupparagraphintro[first][\hbox to 3.5em{\tt FIRST \hss}]
%D \setupparagraphintro[first][\hbox to 3.5em{\tt TSRIF \hss}]
%D \setupparagraphintro[next] [\hbox to 3.5em{\tt NEXT  \hss}]
%D \setupparagraphintro[next] [\hbox to 3.5em{\tt TXEN  \hss}]
%D \setupparagraphintro[each] [\hbox to 3.0em{\tt EACH  \hss}]
%D \setupparagraphintro[each] [\hbox to 3.0em{\tt HCEA  \hss}]
%D
%D some paragraph \par
%D some paragraph \par
%D some paragraph \par
%D
%D \definelabel[parnumber]
%D
%D \setupparagraphintro[reset,each][\inleft{\slxx\parnumber}]
%D
%D some paragraph \par
%D some paragraph \par
%D some paragraph \par
%D \stoptyping

%D \macros
%D   {flushatnextpar}
%D
%D This macro collects data that will be flushed at the next paragraph.
%D By using this macro you can avoid interfering nodes (writes, etc).

\newbox\postponednodedata
\let\flushpostponednodedata\relax

\def\flushatnextpar
  {\bgroup
   \global\let\flushpostponednodedata\doflushpostponednodedata
   \dowithnextbox{\global\setbox\postponednodedata\hbox{\box\postponednodedata\box\nextbox}\egroup}\hbox}

\def\doflushpostponednodedata
  {\ifvoid\postponednodedata\else
     \hbox{\smashedbox\postponednodedata}%
   \fi
   \global\let\flushpostponednodedata\relax}

% Very nasty but needed for margin stuff inside colored
% paragraphs.

\let\normalvadjust\vadjust

\def\graphicvadjust % nasty bidi handling
  {\dowithnextboxcontent
     {\forgetall}
     {\vadjust{\vbox attr \graphicvadjustattribute \plusone
        {\unvbox\nextbox
         % corrects for one line paragraphs
         \nointerlineskip
         \kern-\struttotal
         \nointerlineskip
         \verticalstrut}}}%
     \vbox}

%D This works only in a properly strutted line, and is meant
%D for deeply burried operations, like in heads.

\def\fakedvadjust
  {\dowithnextbox
     {\setbox\nextbox\hbox{\llap{\lower\strutdepth\box\nextbox}}%
      \smashedbox\nextbox}%
   \vtop}

\def\localvbox#1#% used?
  {\vbox#1\bgroup
     \forgetparskip
     \setlocalhsize
     \hsize\localhsize
     \forgetparindent
     \forgetbothskips
     \forgeteverypar
     \let\next=}

\protect \endinput