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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}
+
+\registerctxluafile{spac-par}{autosuffix}
+
+\unprotect
+
+%D New experimental stuff:
+
+\let\spac_paragraph_freeze\relax
+
+\protected\def\freezeparagraphproperties {\snapshotpar\maxcount}
+\protected\def\defrostparagraphproperties{\snapshotpar\zerocount}
+
+\protected\def\setparagraphfreezing   {\let\spac_paragraph_freeze\freezeparagraphproperties}
+\protected\def\forgetparagraphfreezing{\let\spac_paragraph_freeze\relax}
+
+\installcorenamespace {bparwrap}
+\installcorenamespace {eparwrap}
+
+\let\spac_paragraph_wrap\relax
+
+\protected\def\spac_paragraph_update
+  {\ifcsname\??bparwrap\the\currentgrouplevel\endcsname
+     \the\lastnamedcs
+     \wrapuppar{\the\csname\??eparwrap\the\currentgrouplevel\endcsname}%
+   \fi}
+
+
+\protected\def\spac_paragraph_install
+  {\expandafter\newtoks\csname\??bparwrap\the\currentgrouplevel\endcsname
+   \expandafter\newtoks\csname\??eparwrap\the\currentgrouplevel\endcsname}
+
+% \protected\def\registerparwrapper#1#2%
+%   {\ifcsname\??bparwrap\the\currentgrouplevel\endcsname \else
+%      \spac_paragraph_install
+%    \fi
+%    \toksapp\csname\??bparwrap\the\currentgrouplevel\endcsname{#1}%
+%    \tokspre\csname\??eparwrap\the\currentgrouplevel\endcsname{#2}%
+%    \let\spac_paragraph_wrap\spac_paragraph_update}
+
+% \protected\def\registerparwrapperreverse#1#2%
+%   {\ifcsname\??bparwrap\the\currentgrouplevel\endcsname \else
+%      \spac_paragraph_install
+%    \fi
+%    \tokspre\csname\??bparwrap\the\currentgrouplevel\endcsname{#1}%
+%    \toksapp\csname\??eparwrap\the\currentgrouplevel\endcsname{#2}%
+%    \let\spac_paragraph_wrap\spac_paragraph_update}
+
+\protected\def\registerparwrapper#1#2#3%
+  {\ifcsname\??bparwrap\the\currentgrouplevel\endcsname \else
+     \spac_paragraph_install
+   \fi
+   \clf_newparwrapper{#1}%
+   \toksapp\csname\??bparwrap\the\currentgrouplevel\endcsname{\clf_setparwrapper{#1}#2}%
+   \tokspre\csname\??eparwrap\the\currentgrouplevel\endcsname{#3}%
+   \let\spac_paragraph_wrap\spac_paragraph_update}
+
+\protected\def\registerparwrapperreverse#1#2#3%
+  {\ifcsname\??bparwrap\the\currentgrouplevel\endcsname \else
+     \spac_paragraph_install
+   \fi
+   \clf_newparwrapper{#1}%
+   \tokspre\csname\??bparwrap\the\currentgrouplevel\endcsname{\clf_setparwrapper{#1}#2}%
+   \toksapp\csname\??eparwrap\the\currentgrouplevel\endcsname{#3}%
+   \let\spac_paragraph_wrap\spac_paragraph_update}
+
+\protected\def\forgetparwrapper
+  {\csname\??bparwrap\the\currentgrouplevel\endcsname\emptytoks
+   \csname\??eparwrap\the\currentgrouplevel\endcsname\emptytoks}
+
+% \getparwrapper  % defined in lua
+% \lastparwrapper % defined in lua
+
+\protected\def\showparwrapperstate#1%
+  {\begingroup
+   \infofont ¶#1\hilo
+     {\smallinfofont\getparwrapper {#1}}%
+     {\smallinfofont\lastparwrapper{#1}}%
+   \endgroup}
+
+\appendtoks    \updateparwrapperindeed      \to\everypar
+\appendtoks\let\updateparwrapperindeed\relax\to\everyforgetall
+
+\installtexexperiment
+  {paragraphs.freeze}
+  {\setparagraphfreezing
+   \appendtoksonce\spac_paragraph_wrap  \to  \everypar
+   \appendtoksonce\spac_paragraph_freeze\to  \everypar}
+  {\forgetparagraphfreezing
+   \removetoks    \spac_paragraph_wrap  \from\everypar
+   \removetoks    \spac_paragraph_freeze\from\everypar}
+
+%D In due time, the code below will be upgraded using the above mechanisms.
+
+%D The dreadful sequence \type {\bgroup} \unknown\ \type {\carryoverpar} \unknown\
+%D \type {\egroup} is needed when for instance sidefloats are used in combination
+%D with something that starts with a group. This is because otherwise the
+%D indentation as set (by the output routine) inside the group are forgotten
+%D afterwards. (I must not forget its existence).
+
+% Todo (maybe):
+%
+% \parshape             \getparshape\relax
+% \interlinepenalties   \getinterlinepenalties\relax
+% \clubpenalties        \getclubpenalties\relax
+% \widowpenalties       \getwidowpenalties\relax
+% \displaywidowpenalties\getdisplaywidowpenalties\relax
+
+\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}
+
+%D Beware, changing this will break some code (like pos/backgrounds) but it has been
+%D 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
+   \gtoksapp\t_spac_paragraphs_intro_first{#1}%
+   \glet\insertparagraphintro\spac_paragraphs_flush_intro}
+
+\setvalue{\??paragraphintro\v!next}#1%
+  {\global\settrue\c_spac_paragraphs_intro_next
+   \gtoksapp\t_spac_paragraphs_intro_next{#1}%
+   \glet\insertparagraphintro\spac_paragraphs_flush_intro}
+
+\setvalue{\??paragraphintro\v!each}#1%
+  {\global\settrue\c_spac_paragraphs_intro_each
+   \gtoksapp\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
+   \gtoksapp\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 registers to
+%D feed a nice stream into the paragraph.)
+
+\unexpanded\def\spac_paragraphs_flush_intro % we make sure that the token lists expand directly
+  {\normalexpanded{%                        % after another 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. By using
+%D 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\hpack}
+
+\def\spac_postponed_data_finish
+  {\global\setbox\b_spac_postponed_data\hpack % to\zeropoint
+     {\box\b_spac_postponed_data\box\nextbox}%
+   \endgroup}
+
+\def\spac_postponed_data_flush
+  {%\iftrialtypesetting \else
+     \ifvoid\b_spac_postponed_data\else
+       \hpack{\smashedbox\b_spac_postponed_data}% \box\b_spac_postponed_data
+     \fi
+     \glet\flushpostponednodedata\relax
+   }%\fi}
+
+\unexpanded\def\doflushatpar % might be renamed
+  {\ifvmode
+     \expandafter\flushatnextpar
+   \else
+     \expandafter\firstofoneargument
+   \fi}
+
+\protect \endinput