%D \module
%D   [       file=page-str,
%D        version=2006.03.21,
%D          title=\CONTEXT\ Page Macros,
%D       subtitle=Page Streams,
%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 Page Macros / Page Streams}

%D The first version of this component of \CONTEXT\ was written
%D for Thomas Schmitz who asked for parallel page streams. While
%D playing with the code, I decided to make it into a component
%D that can be used to construct all kind of stream related
%D mechanisms. Because I could apply this feature in a project,
%D there is some additional code here (related to graphics).
%D
%D These macros were written while listening to and watching the DVD
%D \quotation {Rush In Rio}.

% not yet ok in mkiv ... marknotes

\unprotect

% taco, what is the best way to append a otr chunk (insert pagediscards?)

\let\currentoutputstream\s!default

\newtoks\defaultstreamoutput \defaultstreamoutput=\OTRONEoutput

\newtoks\normalstreamoutput  \normalstreamoutput={\saveoutputstream[\currentoutputstream]}

\newcount\streampenalty \streampenalty=-101010101

\ifx\multicolumnseject\undefined \else
  \let\normalmulticolumnseject\multicolumnseject
  \def\multicolumnseject{\ifinoutputstream\else\normalmulticolumnseject\fi}
\fi

\newif\ifinoutputstream

\newtoks \everyenableoutputstream

\appendtoks
  \flushsidefloats
\to \everyenableoutputstream

\def\enableoutputstream[#1]%
  {\the\everyenableoutputstream
   \finishoutputstream
   \writestatus{otr}{switching to output stream #1}%
   \inoutputstreamtrue
   \xdef\currentoutputstream{#1}}

\def\disableoutputstream
  {\finishoutputstream
   \writestatus{otr}{switching to default output stream}%
   \inoutputstreamfalse
   \global\let\currentoutputstream\s!default}

\def\useoutputstream[#1]%
  {\writestatus{otr}{using output stream #1}%
   \xdef\currentoutputstream{#1}}

\def\handlestreamoutput
  {\doifelse\currentoutputstream\s!default
     {\ifnum\outputpenalty=\streampenalty
        \ifvoid\normalpagebox \else
          \unvbox\normalpagebox
        \fi
      \else
        \the\defaultstreamoutput
      \fi}
     {\the\normalstreamoutput}}

\OTRONEoutput{\handlestreamoutput}

\def\defineoutputstream[#1]%
  {\doifundefined{otrs:#1}{\expandafter\newbox\csname otrs:#1\endcsname}}

\def\outputstreamtag#1%
  {\csname otrs:#1\endcsname}

\def\finishoutputstream % todo: installoutput
  {\endgraf
   \penalty\streampenalty
   \endgraf}

\def\saveoutputstream[#1]%
  {\writestatus{otr}{saving otr stream #1}%
   \ifvoid\normalpagebox
     \global\setbox\outputstreamtag{#1}\emptybox
   \else
     \global\setbox\outputstreamtag{#1}\vbox
       {\presetoutputstream
        \ifvoid\outputstreamtag{#1}\else\unvbox\outputstreamtag{#1}\fi
        \scratchdimen\dp\normalpagebox
        \unvbox\normalpagebox
        \vskip-\scratchdimen
        \kern\strutdepth}%
   \fi}

% \def\presetoutputstream
%   {\pdffirstlineheight\strutheight
%    \pdflastlinedepth  \strutdepth
%    \pdfeachlineheight \strutheight
%    \pdfeachlinedepth  \strutdepth}

\let\presetoutputstream\relax

\def\outputstreamht  [#1]{\ht\outputstreamtag{#1}}
\def\outputstreamdp  [#1]{\dp\outputstreamtag{#1}}
\def\outputstreamwd  [#1]{\wd\outputstreamtag{#1}}

%def\outputstreambox [#1]{\ifvoid\outputstreamtag{#1}\else\box \outputstreamtag{#1}\fi}
%def\outputstreamcopy[#1]{\ifvoid\outputstreamtag{#1}\else\copy\outputstreamtag{#1}\fi}

\def\dowithoutputstreambox#1[#2]{\ifvoid\outputstreamtag{#2}\else#1\outputstreamtag{#2}\fi}

\def\outputstreamcopy   {\dowithoutputstreambox\copy   }
\def\outputstreambox    {\dowithoutputstreambox\box    }
\def\outputstreamunvcopy{\dowithoutputstreambox\unvcopy}
\def\outputstreamunvbox {\dowithoutputstreambox\unvbox }

%D Footnotes don't go along with streams, simply because there is no
%D way to re-split inserts. A dirty way out is to use marks and store
%D notes that way.

\def\definemarknote
  {\dodoubleempty\dodefinemarknote}

\def\dodefinemarknote[#1][#2]%
  {\definemarking[mn:#1]%
   \setvalue{mn:#1:n}{0}%
   \getparameters
     [mn:#1]
     [\c!before=,
      \c!after=,
      \c!inbetween=\endgraf,
      \c!command=\firstofoneargument,
      #2]}

\def\setmarknote[#1]#2%
  {\doglobal\incrementvalue{mn:#1:n}%
   \setgvalue{mn:#1:t:\getvalue{mn:#1:n}}{#2}%
   \expanded{\marking[mn:#1]{\getvalue{mn:#1:n}}}}

\def\flushmarknotes[#1]% assumes split
  {\begingroup
%    \edef\firstmarknote{0\fetchmark[mn:#1][column:first]}%
%    \edef\lastmarknote {0\fetchmark[mn:#1][column:last]}%
%    \ifnum\firstmarknote<\lastmarknote\relax
%      \getvalue{mn:#1\c!before}%
%      \dostepwiserecurse\firstmarknote\lastmarknote\plusone
%        {\ifnum\recurselevel>\firstmarknote\relax
%           \ifnum\recurselevel<\lastmarknote\relax
%             \getvalue{mn:#1\c!inbetween}%
%           \fi
%         \fi
%         \getvalue{mn:#1\c!command}{\getvalue{mn:#1:t:\recurselevel}}}%
%      \getvalue{mn:#1\c!after}%
%    \fi
   \endgroup}

\def\erasemarknotes[#1]%
  {\begingroup
   \edef\firstmarknote{0\fetchmark[mn:#1][column:first]}%
   \edef\lastmarknote {0\fetchmark[mn:#1][column:last]}%
   \dostepwiserecurse\firstmarknote\lastmarknote\plusone
     {\global\letvalue{mn:#1:t:\recurselevel}\empty}%
   \endgroup}

%D The next section implements synchronization of (currently
%D two) output streams. In due time we will implement both a
%D vertical and horizontal system, as well as alternative
%D splitters (firstpagevsize, succesivevsize etc).

\def\synchronizeoutputstreams[#1]% [one,two] [left,right]
  {\bgroup
   \getfromcommalist[#1][\plusone]\let\firstoutputstream \commalistelement
   \getfromcommalist[#1][\plustwo]\let\secondoutputstream\commalistelement
   \forgeteverypar
   \def\roundingeps{50sp}%
   \getboxheight\dimen0\of\box\outputstreamtag\firstoutputstream
   \getboxheight\dimen2\of\box\outputstreamtag\secondoutputstream
   \scratchdimen\dimexpr\dimen0-\dimen2\relax
   \ifdim\scratchdimen<-\roundingeps\relax
     \scratchdimen-\scratchdimen
     \writestatus{sync}{compensating first stream: \the\scratchdimen/\number\scratchdimen}%
     \getroundednoflines\scratchdimen
     \global\setbox\outputstreamtag\firstoutputstream\vbox
       {\presetoutputstream
        \unvbox\outputstreamtag\firstoutputstream\dorecurse\noflines\crlf}%
   \else\ifdim\scratchdimen>\roundingeps\relax
     \writestatus{sync}{compensating second stream: \the\scratchdimen/\number\scratchdimen}%
     \getroundednoflines\scratchdimen
     \global\setbox\outputstreamtag\secondoutputstream\vbox
       {\presetoutputstream
        \unvbox\outputstreamtag\secondoutputstream\dorecurse\noflines\crlf}%
   \else
      \writestatus{sync}{no need to compensate streams: \the\scratchdimen/\number\scratchdimen}%
   \fi\fi
   \egroup}

\def\nofoutputstreamsplitlines  {\v!auto} % {40}
\def\outputstreamsplittolerance {-5}

\def\flushoutputstreampages[#1]%
  {\bgroup
   \getfromcommalist[#1][\plusone]\let\firstoutputstream \commalistelement
   \getfromcommalist[#1][\plustwo]\let\secondoutputstream\commalistelement
   \doloop
     {\flushoutputstreams[#1]%
      \ifvoid\outputstreamtag\firstoutputstream
        \ifvoid\outputstreamtag\secondoutputstream
          \exitloop
        \else
          \global\setbox\outputstreamtag\firstoutputstream\vbox{\strut}%
        \fi
      \else
        \ifvoid\outputstreamtag\secondoutputstream
          \global\setbox\outputstreamtag\secondoutputstream\vbox{\strut}%
        \else
          % okay
        \fi
      \fi}%
   \egroup}

\def\flushoutputstreams[#1]%
  {\bgroup
   \getfromcommalist[#1][\plusone]\let\firstoutputstream \commalistelement
   \getfromcommalist[#1][\plustwo]\let\secondoutputstream\commalistelement
   \doif\nofoutputstreamsplitlines\v!auto
     {\getrawnoflines\textheight
      \edef\nofoutputstreamsplitlines{\the\noflines}}%
   \splittopskip\strutheight
   \scratchdimen\nofoutputstreamsplitlines\lineheight\relax
   \unless\iffalse
     \dimen0\scratchdimen
     \doloop
       {\setbox4\copy\outputstreamtag\firstoutputstream
        \setbox0\vsplit4 to \dimen0
        \setbox0\vbox
          {\directsetup{stream:\firstoutputstream:top}%
           \unvbox0
           \directsetup{stream:\firstoutputstream:bottom}}%
        \ifdim\ht0>\scratchdimen
          \advance\dimen0-\lineheight
        \else
          \exitloop
        \fi}%
     \scratchdimen\dimen0
     \dimen2\scratchdimen
     \doloop
       {\setbox6\copy\outputstreamtag\secondoutputstream
        \setbox2\vsplit6 to \dimen2
        \setbox2\vbox
          {\directsetup{stream:\secondoutputstream:top}%
           \unvbox0
           \directsetup{stream:\secondoutputstream:bottom}}%
        \ifdim\ht2>\scratchdimen
          \advance\dimen2-\lineheight
        \else
          \exitloop
        \fi}%
     \scratchdimen\dimen2
   \fi
   \setbox4\copy\outputstreamtag\firstoutputstream
   \setbox6\copy\outputstreamtag\secondoutputstream
   \scratchcounter\zerocount
   \doloop
     {\setbox0\vsplit4 to \scratchdimen
      \setbox0\vbox{\unvbox0}%
      \setbox2\vsplit6 to \scratchdimen
      \setbox2\vbox{\unvbox2}%
      \ifvoid4
        \exitloop
      \else\ifvoid6
        \exitloop
      \else
          \dimen8=\dimexpr\ht4-\ht6\relax
          \ifdim\dimen8<\zeropoint\dimen8=-\dimen8\relax\fi
          \advance\scratchcounter\plusone
          \ifdim\dimen8<.5\lineheight
            \exitloop
          \else\ifnum\outputstreamsplittolerance>\zeropoint
            \ifnum\scratchcounter>\outputstreamsplittolerance\relax
              \exitloop
            \else
              \advance\scratchdimen\lineheight
            \fi
          \else\ifnum\outputstreamsplittolerance<\zeropoint
            \ifnum-\scratchcounter<\outputstreamsplittolerance\relax
              \exitloop
            \else
              \advance\scratchdimen-\lineheight
            \fi
          \else\ifnum\outputstreamsplittolerance=\zeropoint
            \exitloop
          \fi\fi\fi\fi
       \fi\fi}%
   \setbox0\vsplit\outputstreamtag\firstoutputstream to \scratchdimen
   \setbox0\vbox to \textheight
     {\presetoutputstream
      \directsetup{stream:\firstoutputstream:top}%
      \unvbox0
      \vfill
      \directsetup{stream:\firstoutputstream:bottom}}%
   \setbox2\vsplit\outputstreamtag\secondoutputstream to \scratchdimen
   \setbox2\vbox to \textheight
     {\presetoutputstream
      \directsetup{stream:\secondoutputstream:top}%
      \unvbox2
      \vfill
      \directsetup{stream:\secondoutputstream:bottom}}%
   \directsetup{stream:\firstoutputstream:reset}%
   \directsetup{stream:\secondoutputstream:reset}%
   \page[even]
   \box0\vfill\page
   \box2\vfill\page
   \egroup}

%D Because many arrangements are possible, we will implement
%D some examples in a runtime loadable module \type {m-streams}.

\protect \endinput