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+%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 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 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).
+
+\def\carryoverpar#1% #1 can be \endgroup or \egroup or ... expandable !
+  {\normalexpanded
+     {\noexpand#1%
+      \hangindent\the\hangindent
+      \hangafter \the\hangafter
+      \parskip   \the\parskip
+      \leftskip  \the\leftskip
+      \rightskip \the\rightskip}}
+
+\unexpanded\def\pushparagraphproperties
+  {\edef\currentparagraphproperties{\carryoverpar\relax}%
+   \pushmacro\currentparagraphproperties}
+
+\unexpanded\def\popparagraphproperties
+  {\popmacro\currentparagraphproperties
+   \currentparagraphproperties}
+
+\unexpanded\def\flushparagraphproperties
+  {\popmacro\currentparagraphproperties}
+
+% Beware, changing this will break some code (like pos/backgrounds) but
+% it has been changed anyway so let's see where things go wrong.
+
+\installcorenamespace{paragraphintro}
+
+\let\insertparagraphintro\relax % hook into everypar
+
+\newtoks\t_spac_paragraphs_intro_first
+\newtoks\t_spac_paragraphs_intro_next
+\newtoks\t_spac_paragraphs_intro_each
+
+\newconditional\c_spac_paragraphs_intro_first
+\newconditional\c_spac_paragraphs_intro_next
+\newconditional\c_spac_paragraphs_intro_each
+
+\unexpanded\def\setupparagraphintro
+  {\dodoubleempty\spac_paragraphs_intro}
+
+\unexpanded\def\spac_paragraphs_intro[#1][#2]%
+  {\def\spac_paragraphs_intro_step##1%
+     {\csname\??paragraphintro\ifcsname\??paragraphintro##1\endcsname##1\fi\endcsname{#2}}%
+   \processcommacommand[#1]\spac_paragraphs_intro_step}
+
+\letvalue{\??paragraphintro\empty}\gobbleoneargument
+
+\setvalue{\??paragraphintro\v!reset}#1%
+  {\global\setfalse\c_spac_paragraphs_intro_first
+   \global\setfalse\c_spac_paragraphs_intro_next
+   \global\setfalse\c_spac_paragraphs_intro_each
+   \global\t_spac_paragraphs_intro_first\emptytoks
+   \global\t_spac_paragraphs_intro_next \emptytoks
+   \global\t_spac_paragraphs_intro_each \emptytoks
+   \glet\insertparagraphintro\relax}
+
+\setvalue{\??paragraphintro\v!first}#1%
+  {\global\settrue\c_spac_paragraphs_intro_first
+   \global\t_spac_paragraphs_intro_first\expandafter{\the\t_spac_paragraphs_intro_first#1}%
+   \glet\insertparagraphintro\spac_paragraphs_flush_intro}
+
+\setvalue{\??paragraphintro\v!next}#1%
+  {\global\settrue\c_spac_paragraphs_intro_next
+   \global\t_spac_paragraphs_intro_next\expandafter{\the\t_spac_paragraphs_intro_next#1}%
+   \glet\insertparagraphintro\spac_paragraphs_flush_intro}
+
+\setvalue{\??paragraphintro\v!each}#1%
+  {\global\settrue\c_spac_paragraphs_intro_each
+   \global\t_spac_paragraphs_intro_each\expandafter{\the\t_spac_paragraphs_intro_each#1}%
+   \glet\insertparagraphintro\spac_paragraphs_flush_intro}
+
+%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
+%D
+%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 some paragraph \par
+%D
+%D \setupparagraphintro[first][\hbox to 3.5em{\tt FIRST \hss}]
+%D \setupparagraphintro[first][\hbox to 3.5em{\tt TSRIF \hss}]
+%D
+%D some paragraph \par
+%D some paragraph \par
+%D
+%D \setupparagraphintro[reset]
+%D
+%D some paragraph \par
+%D \stoptyping
+
+\unexpanded\def\flushatparagraph#1%
+  {\global\c_spac_paragraphs_intro_first\plusone
+   \global\t_spac_paragraphs_intro_first\expandafter{\the\t_spac_paragraphs_intro_first#1}%
+   \glet\insertparagraphintro\spac_paragraphs_flush_intro}
+
+%D Here comes the flusher (we misuse the one level expansion of token
+%D registers to feed a nice stream into the paragraph.)
+
+\unexpanded\def\spac_paragraphs_flush_intro % we make sure that the token lists expand directly after another
+  {\normalexpanded{%                            % so the first code is there twice
+     \ifconditional\c_spac_paragraphs_intro_each
+       \ifconditional\c_spac_paragraphs_intro_next
+         \glet\insertparagraphintro\spac_paragraphs_flush_intro_next
+       \else
+         \glet\insertparagraphintro\spac_paragraphs_flush_intro_each
+       \fi
+       \ifconditional\c_spac_paragraphs_intro_first
+         \global\setfalse\c_spac_paragraphs_intro_first
+         \global\t_spac_paragraphs_intro_first\emptytoks
+         \the\t_spac_paragraphs_intro_first
+       \fi
+       \the\t_spac_paragraphs_intro_each
+     \else
+       \ifconditional\c_spac_paragraphs_intro_next
+         \glet\insertparagraphintro\spac_paragraphs_flush_intro_next
+       \fi
+       \ifconditional\c_spac_paragraphs_intro_first
+         \global\setfalse\c_spac_paragraphs_intro_first
+         \global\t_spac_paragraphs_intro_first\emptytoks
+         \the\t_spac_paragraphs_intro_first
+       \fi
+     \fi}}
+
+\unexpanded\def\spac_paragraphs_flush_intro_next
+  {\normalexpanded{%
+     \global\setfalse\c_spac_paragraphs_intro_next
+     \global\t_spac_paragraphs_intro_next\emptytoks
+     \ifconditional\c_spac_paragraphs_intro_each
+       \glet\insertparagraphintro\spac_paragraphs_flush_intro_each
+       \the\t_spac_paragraphs_intro_next
+       \the\t_spac_paragraphs_intro_each
+     \else
+       \glet\insertparagraphintro\relax
+       \the\t_spac_paragraphs_intro_next
+     \fi}}
+
+\unexpanded\def\spac_paragraphs_flush_intro_each
+  {\the\t_spac_paragraphs_intro_each}
+
+%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).
+
+\let\flushpostponednodedata\relax % hook into everypar
+
+\newbox  \b_spac_postponed_data
+%newcount\c_spac_postponed_data
+
+% \installcorenamespace {postponednodesstack}
+%
+% \initializeboxstack\??postponednodesstack
+%
+% \unexpanded\def\pushpostponednodedata
+%   {\global\advance\c_spac_postponed_data\plusone
+%    \savebox\??postponednodesstack{\the\c_spac_postponed_data}{\box\b_spac_postponed_data}}
+%
+% \unexpanded\def\poppostponednodedata
+%   {\global\setbox\b_spac_postponed_data\hbox{\foundbox\??postponednodesstack{\the\c_spac_postponed_data}}%
+%    \global\advance\c_spac_postponed_data\minusone
+%    \ifvoid\b_spac_postponed_data\else
+%      \glet\flushpostponednodedata\spac_postponed_data_flush
+%    \fi}
+
+\newtoks\everyflushatnextpar
+
+\unexpanded\def\pushpostponednodedata
+  {\globalpushbox\b_spac_postponed_data}
+
+\unexpanded\def\poppostponednodedata
+  {\globalpopbox\b_spac_postponed_data
+   \ifvoid\b_spac_postponed_data\else
+     \glet\flushpostponednodedata\spac_postponed_data_flush
+   \fi}
+
+\unexpanded\def\flushatnextpar
+  {\begingroup
+   \the\everyflushatnextpar
+   \glet\flushpostponednodedata\spac_postponed_data_flush
+   \dowithnextboxcs\spac_postponed_data_finish\hbox}
+
+\def\spac_postponed_data_finish
+  {\global\setbox\b_spac_postponed_data\hbox % to\zeropoint
+     {\box\b_spac_postponed_data\box\nextbox}%
+   \endgroup}
+
+\def\spac_postponed_data_flush
+  {%\iftrialtypesetting \else
+     \ifvoid\b_spac_postponed_data\else
+       \hbox{\smashedbox\b_spac_postponed_data}% \box\b_spac_postponed_data
+     \fi
+     \glet\flushpostponednodedata\relax
+   }%\fi}
+
+\unexpanded\def\doflushatpar
+  {\ifvmode
+     \expandafter\flushatnextpar
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+\protect \endinput