%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:

% this might move to syst-ini.mkxl

\setnewconstant\frozenhsizecode                 "00000001
\setnewconstant\frozenleftskipcode              "00000002
\setnewconstant\frozenrightskipcode             "00000004
\setnewconstant\frozenhangindentcode            "00000008
\setnewconstant\frozenhangaftercode             "00000010
\setnewconstant\frozenparindentcode             "00000020
\setnewconstant\frozenparfillskipcode           "00000040
\setnewconstant\frozenparfillleftskipcode       "00000080
\setnewconstant\frozenadjustspacingcode         "00000100
\setnewconstant\frozenprotrudecharscode         "00000200
\setnewconstant\frozenpretolerancecode          "00000400
\setnewconstant\frozentolerancecode             "00000800
\setnewconstant\frozenemergencystretchcode      "00001000
\setnewconstant\frozenloosenesscode             "00002000
\setnewconstant\frozenlastlinefitcode           "00004000
\setnewconstant\frozenlinepenaltycode           "00008000
\setnewconstant\frozeninterlinepenaltycode      "00010000
\setnewconstant\frozenclubpenaltycode           "00020000
\setnewconstant\frozenwidowpenaltycode          "00040000
\setnewconstant\frozendisplaywidowpenaltycode   "00080000
\setnewconstant\frozenbrokenpenaltycode         "00100000
\setnewconstant\frozenadjdemeritscode           "00200000
\setnewconstant\frozendoublehyphendemeritscode  "00400000
\setnewconstant\frozenfinalhyphendemeritscode   "00800000
\setnewconstant\frozenparshapecode              "01000000
\setnewconstant\frozeninterlinepenaltiescode    "02000000
\setnewconstant\frozenclubpenaltiescode         "04000000
\setnewconstant\frozenwidowpenaltiescode        "08000000
\setnewconstant\frozendisplaywidowpenaltiescode "10000000

\setnewconstant\paragraphupdatecodes\numexpr
    \frozentolerancecode
  + \frozenloosenesscode
  + \frozenlinepenaltycode
  + \frozeninterlinepenaltycode
  + \frozenwidowpenaltycode
  + \frozenclubpenaltycode
  + \frozenbrokenpenaltycode
  + \frozenadjdemeritscode
  + \frozendoublehyphendemeritscode
  + \frozenfinalhyphendemeritscode
  + \frozeninterlinepenaltiescode
  + \frozenwidowpenaltiescode
  + \frozenclubpenaltiescode
\relax

\setnewconstant\paragraphpenaltycodes\numexpr
    \frozeninterlinepenaltycode
  + \frozenwidowpenaltycode
  + \frozenclubpenaltycode
  + \frozenbrokenpenaltycode
  + \frozeninterlinepenaltiescode
  + \frozenwidowpenaltiescode
  + \frozenclubpenaltiescode
\relax

\setnewconstant\paragraphdemeritcodes\numexpr
    \frozenadjdemeritscode
  + \frozendoublehyphendemeritscode
  + \frozenfinalhyphendemeritscode
\relax

% + \frozenparskipcode

\setnewconstant\paragraphshapecodes\numexpr
   \frozenhangindentcode
 + \frozenhangaftercode
 + \frozenleftskipcode
 + \frozenrightskipcode
 + \frozenparfillskipcode
 + \frozenparshapecode
\relax

\protected\def\freezeparagraphproperties {\snapshotpar\maxcount}
\protected\def\defrostparagraphproperties{\snapshotpar\zerocount}

\protected\def\updateparagraphproperties {\ifhmode\snapshotpar\paragraphupdatecodes \fi}
\protected\def\updateparagraphpenalties  {\ifhmode\snapshotpar\paragraphpenaltycodes\fi}
\protected\def\updateparagraphdemerits   {\ifhmode\snapshotpar\paragraphdemeritcodes\fi}
\protected\def\updateparagraphshapes     {\ifhmode\snapshotpar\paragraphshapecodes  \fi}

% so far

\let\spac_paragraph_freeze\relax

\protected\def\setparagraphfreezing      {\let\spac_paragraph_freeze\freezeparagraphproperties}
\protected\def\forgetparagraphfreezing   {\let\spac_paragraph_freeze\relax}

\installcorenamespace {bparwrap}
\installcorenamespace {eparwrap}
\installcorenamespace {parwrapbefore}
\installcorenamespace {parwrapafter}
\installcorenamespace {parwrapcount}

\let\spac_paragraph_wrap\relax

\newcount\c_spac_paragraph_group_level

\protected\def\spac_paragraph_update
  {\c_spac_paragraph_group_level\currentgrouplevel\relax
   \ifcsname\??bparwrap\the\c_spac_paragraph_group_level\endcsname
     \the\lastnamedcs
     \relax
     \dontleavehmode % just in case
     \wrapuppar{\the\csname\??eparwrap\the\c_spac_paragraph_group_level\endcsname\relax}%
   \fi}

\protected\def\registerparwrapper       {\spac_register_par_wrapper\toksapp\tokspre}
\protected\def\registerparwrapperreverse{\spac_register_par_wrapper\tokspre\toksapp}

\protected\def\spac_paragraph_install
  {\expandafter\newtoks\csname\??bparwrap\the\currentgrouplevel\endcsname
   \expandafter\newtoks\csname\??eparwrap\the\currentgrouplevel\endcsname}

\def\spac_paragraph_install_count#1%
  {\expandafter\newcount\csname\??parwrapcount#1\endcsname}

\def\spac_paragraph_install_pair#1#2#3%
  {\expandafter\newtoks\csname\??parwrapbefore#3\endcsname
   \expandafter\newtoks\csname\??parwrapafter #3\endcsname
   #1\csname\??bparwrap\the\currentgrouplevel\endcsname
     {\the\csname\??parwrapbefore#3\endcsname}%
   #2\csname\??eparwrap\the\currentgrouplevel\endcsname
     {\the\csname\??parwrapafter #3\endcsname}}

\def\spac_register_par_wrapper_yes#1#2#3#4#5%
  {\ifcsname\??bparwrap\the\currentgrouplevel\endcsname \else
     \spac_paragraph_install
   \fi
   \ifcsname\??parwrapcount#3\endcsname \else
     \spac_paragraph_install_count{#3}%
   \fi
   \ifcsname\??parwrapbefore#3\endcsname \else
     \spac_paragraph_install_pair#1#2{#3}%
   \fi
   #1\csname\??parwrapbefore#3\endcsname{\advance\csname\??parwrapcount#3\endcsname\plusone\relax
                                         \clf_setparwrapper{#3}#4}%
   #2\csname\??parwrapafter #3\endcsname{#5}%
   \clf_newparwrapper{#3}%
   \let\spac_paragraph_wrap\spac_paragraph_update}

\def\spac_register_par_wrapper_nop#1#2#3#4#5%
  {\ifcsname\??parwrapcount#3\endcsname \else
     \spac_paragraph_install_count{#3}%
   \fi
   \csname\??parwrapcount#3\endcsname\plusone
   #4\wrapuppar{#5}}

\protected\def\spac_register_par_wrapper
  {\ifhmode
     \expandafter\spac_register_par_wrapper_nop
   \else
     \expandafter\spac_register_par_wrapper_yes
   \fi}

\protected\def\forgetparwrapper
  {\csname\??bparwrap\the\currentgrouplevel\endcsname\emptytoks
   \csname\??eparwrap\the\currentgrouplevel\endcsname\emptytoks}

\protected\def\unregisterparwrapper#1%
  {\csname\??parwrapcount#1\endcsname\zerocount
   \ifcsname\??parwrapbefore#1\endcsname
     \lastnamedcs\emptytoks
     \csname\??parwrapafter#1\endcsname\emptytoks
   \fi}

\def\directparwrapper#1#2%
  {#1\wrapuppar{#2}}

% \protected\def\doifelseparwrapper#1%
%   {\ifcsname\??parwrapbefore#1\endcsname
%      \unless\iftok\lastnamedcs\emptytoks
%        \doubleexpandafter\firstoftwoarguments
%      \orelse\iftok\csname\??parwrapafter#1\endcsname\emptytoks
%        \doubleexpandafter\secondoftwoarguments
%      \else
%        \doubleexpandafter\firstoftwoarguments
%      \fi
%    \else
%      \expandafter\secondoftwoarguments
%    \fi}

\protected\def\doifelseparwrapper#1%
  {\unless\ifcsname\??parwrapcount#1\endcsname
     \expandafter\secondoftwoarguments
   \orelse\ifcase\lastnamedcs
     \expandafter\secondoftwoarguments
   \else
     \expandafter\firstoftwoarguments
   \fi}

% \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\spac_paragraph_wrap   \to\everypar
%appendtoks\spac_paragraph_freeze \to\everypar

\setparagraphfreezing

\appendtoks\let\spac_paragraph_wrap\relax\to\everyforgetall

%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).

\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}
%
% This is better when used with protrusion which does not like too deeply nested
% boxes:
%
% \def\spac_postponed_data_finish
%   {\dontcomplain
%    \global\setbox\b_spac_postponed_data\hpack to \zeropoint
%      {\unhbox\b_spac_postponed_data\unhbox\nextbox}%
%    \endgroup}
%
% We could do this if there is content with widths ... not that is should be used
% that way, but this way we don't overflow:

\def\spac_postponed_data_finish
  {\dontcomplain
   \global\setbox\b_spac_postponed_data\hpack % to \zeropoint
     {\unhbox\b_spac_postponed_data
      \scratchdimen\wd\nextbox
      \unhbox\nextbox
      \ifcase\scratchdimen\else\kern-\b_spac_postponed_data\fi}%
   \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