%D \module
%D   [       file=page-mul, % was: core-mul
%D        version=1998.03.15,
%D          title=\CONTEXT\ Page Macros,
%D       subtitle=Multi Column Output,
%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.

% todo: basecolumns as parent for columns and itemize

% !!! there are some issues with hsize an vsize as well as flushing
% !!! floats but this module will be redone anyway
%
% can have some vpack and hpack

\writestatus{loading}{ConTeXt Page Macros / Simple Multi Column}

%D This module is mostly a copy from the original multi column routine as
%D implemented in \type {core-mul}. When the main OTR macro's were
%D isolated in modules and column sets were introduced, this module became
%D part of the OTR modules. As a result this module is no longer generic.

\unprotect

\definesystemvariable {ks}   % KolomSpan

% check \count<insert> multiplications

%D The following macro's implement a multi||column output routine. The original
%D implementation was based on Donald Knuth's implementation, which was adapted by
%D Craig Platt to support balancing of the last page. I gradually adapted Platt's
%D version to our needs but under certain circumstances things still went wrong. I
%D considered all calls to Platt's \type{\page_mul_routine_error} as undesirable.
%D
%D This completely new implementation can handle enough situations for everyday
%D documents, but is still far from perfect. While at the moment the routine doesn't
%D support all kind of floats, it does support:
%D
%D \startitemize[packed]
%D \item  an unlimitted number of columns
%D \item  ragged or not ragged bottoms
%D \item  optional balancing without \type{\page_mul_routine_errors}
%D \item  different \type{\baselineskips}, \type{\spacing}, \type {\topskip} and
%D        \type {\maxdepth}
%D \item  left- and right indentation, e.g. within lists
%D \item  moving columns floats to the next column or page
%D \item  handling of floats that are to wide for a columns
%D \stopitemize
%D
%D One could wonder why single and multi||columns modes are still separated. One
%D reason for this is that \TeX\ is not suited well for handling multi||columns. As
%D a result, the single columns routines are more robust. Handling one column as a
%D special case of multi||columns is posible but at the cost of worse float
%D handling, worse page breaking, worse etc. Complicated multi||column page handling
%D should be done in \cap{DTP}||systems anyway.

\installcorenamespace {columns}

\installframedcommandhandler \??columns {columns} \??columns

%D Going to a new columns is done by means of a \type {\ejectcolumn}. The
%D following definition does not always work.

    \unexpanded\def\ejectcolumn % not good enough
      {\goodbreak
       \showmessage\m!columns2\empty}

%D The output routines plug into a more generic mechanism as can be seen at the
%D end of this file. So, occasionally we need to define some plugin code.

\unexpanded\def\page_mul_place_float_top
  {\showmessage\m!columns4\empty\page_one_place_float_here}

\unexpanded\def\page_mul_place_float_bottom
  {\showmessage\m!columns5\empty\page_one_place_float_here}

\unexpanded\def\page_mul_place_float_here
  {\page_one_place_float_here}

\unexpanded\def\page_mul_place_float_force
  {\page_one_place_float_force}

\unexpanded\def\page_mul_command_side_float_output
  {\page_otr_construct_and_shipout\unvbox\normalpagebox\zerocount} % three arguments

\unexpanded\def\page_mul_command_flush_side_floats
  {\page_sides_forget_floats}

\unexpanded\def\page_mul_command_synchronize_side_floats
  {\page_sides_forget_floats}

\unexpanded\def\page_mul_command_next_page
  {\page_otr_eject_page}

\unexpanded\def\page_mul_command_next_page_and_inserts
  {\page_otr_eject_page_and_flush_inserts}

\let\page_mul_initialize_floats\relax
\let\page_mul_flush_floats     \relax
\let\page_mul_flush_float      \relax

%D A hook:

\let\finishcolumnbox\relax % todo in mkiv

%D This will change to a local one:

\ifdefined\nofcolumns \else \newcount\nofcolumn \fi
\ifdefined\mofcolumns \else \newcount\mofcolumn \fi

\appendtoks
    \nofcolumns\columnsparameter\c!n\relax
\to \everysetupcolumns

%D Columns are separated by spacing or rules or whatever suits.

\installcorenamespace{columnseparators}

\setvalue{\??columnseparators\v!on     }{\let\page_mul_between_columns\page_mul_between_columns_rule}
\setvalue{\??columnseparators\v!off    }{\let\page_mul_between_columns\page_mul_between_columns_space}
\setvalue{\??columnseparators          }{\let\page_mul_between_columns\page_mul_between_columns_space}
\setvalue{\??columnseparators\s!unknown}{\let\page_mul_between_columns\p_page_mul_rule}

\def\page_mul_between_columns_rule
  {\bgroup
   \starttextproperties
   \scratchdistance\dimexpr\columnsparameter\c!distance/2\relax
   \hskip\scratchdistance\relax
   \vrule
     \s!width\linewidth
     \ifnum\bottomraggednessmode=\plustwo % baselinebottom
       \s!depth\strutdepth
     \fi
   \hskip\scratchdistance\relax
   \stoptextproperties
   \egroup}

\def\page_mul_between_columns_space
  {\hskip\columnsparameter\c!distance\relax}

\let\page_mul_between_columns\page_mul_between_columns_space

%D We declare some registers:

\newdimen      \d_page_mul_available_width
\newdimen      \d_page_mul_distance
\newdimen      \d_page_mul_leftskip
\newdimen      \d_page_mul_rightskip
\newdimen      \d_page_mul_offset
\newdimen      \d_page_mul_forced_height
\newdimen      \d_page_mul_used_width
\newdimen      \d_page_mul_temp

\newcount      \c_page_mul_balance_minimum
\newcount      \c_page_mul_n_of_lines

\newbox        \b_page_mul_preceding
\newdimen      \d_page_mul_preceding_height
\newdimen      \d_page_mul_preceding_depth
\newconditional\c_page_mul_preceding_present

\newbox        \b_page_mul_preceding_rest_of_page

\newconditional\c_page_mul_reverse
\newconditional\c_page_mul_trace

%D The next dimensions reports the final column height .. todo

    \newdimen\finalcolumnheights
    \newcount\finalcolumnlines

    \newdimen\savedpagetotal % brrr

    \newif\ifstretchcolumns       \stretchcolumnsfalse
    \newif\ifheightencolumns      \heightencolumnsfalse
    \newif\ifinheritcolumns       \inheritcolumnsfalse
    \newif\ifbalancecolumns       %\balancecolumnstrue

%D An important one:

\unexpanded\def\page_mul_command_set_hsize % beware, this one is available for use in macros
  {\setbox\scratchbox\hbox{\page_mul_between_columns}%
   \d_page_mul_distance\wd\scratchbox
   \d_page_mul_available_width\dimexpr
      \makeupwidth
     -\d_page_mul_leftskip
     -\d_page_mul_rightskip
     -\nofcolumns\d_page_mul_distance
     +\d_page_mul_distance
   \relax
   \d_page_mul_used_width\dimexpr
      \d_page_mul_available_width/\nofcolumns
     -\d_page_mul_offset*\plustwo
   \relax
   \textwidth\d_page_mul_used_width % needs thinking ... grouping etc
   \hsize\d_page_mul_used_width}

%D Torture test:
%D
%D \startbuffer
%D \startbuffer[b]
%D \startcolumns
%D   \input tufte
%D \stopcolumns
%D \stopbuffer
%D \typebuffer[b] \getbuffer[b]
%D
%D \startbuffer[b]
%D \startnarrower
%D   \input tufte
%D \stopnarrower
%D \stopbuffer
%D \typebuffer[b] \getbuffer[b]
%D
%D \startbuffer[b]
%D \startcolumns \startnarrower
%D   \input tufte
%D \stopnarrower \stopcolumns
%D \stopbuffer
%D \typebuffer[b] \getbuffer[b]
%D
%D \startbuffer[b]
%D \startnarrower \startcolumns
%D   \input tufte
%D \stopcolumns \stopnarrower
%D \stopbuffer
%D \typebuffer[b] \getbuffer[b]
%D
%D \startbuffer[b]
%D \startcolumns \startnarrower[left]
%D   \input tufte
%D \stopnarrower \stopcolumns
%D \stopbuffer
%D \typebuffer[b] \getbuffer[b]
%D
%D \startbuffer[b]
%D \startnarrower[left] \startcolumns
%D   \input tufte
%D \stopcolumns \stopnarrower
%D \stopbuffer
%D \typebuffer[b] \getbuffer[b]
%D
%D \startbuffer[b]
%D \startnarrower \startcolumns \startnarrower
%D   \input tufte
%D \stopnarrower\stopcolumns \stopnarrower
%D \stopbuffer
%D \typebuffer[b] \getbuffer[b]
%D
%D \startbuffer[b]
%D \startnarrower[left] \startcolumns \startnarrower
%D   \input tufte
%D \stopnarrower\stopcolumns \stopnarrower
%D \stopbuffer
%D \typebuffer[b] \getbuffer[b]
%D \stopbuffer
%D
%D \start
%D \def\postprocesscolumnline#1{\ruledhbox{\strut\box#1}\hss}
%D \getbuffer
%D \stop

%D One should be aware that when font related dimensions are used in typesetting the
%D in||between material, these dimensions are influenced by bodyfont switches inside
%D multi||column mode.

\setnewconstant\multicolumnlinemethod\zerocount % 0=normal 1=raw

\def\multicolumnovershootratio{.5} % {\ifgridsnapping0\else.5\fi}

\unexpanded\def\page_mul_set_n_of_lines
  {\settotalinsertionheight
   \d_page_mul_temp\dimexpr
     -\d_page_mul_offset*\plustwo
     +\textheight
      \ifdim\d_page_mul_preceding_height>\zeropoint -\d_page_mul_preceding_height \fi
     -\totalinsertionheight
   \relax
   \ifcase\multicolumnlinemethod
     \getnoflines   \d_page_mul_temp \or
     \getrawnoflines\d_page_mul_temp \else
     \getrawnoflines\d_page_mul_temp
   \fi
   % added 30/7/2004
   \ifnum\layoutlines>\zerocount \ifnum\noflines>\layoutlines
     \noflines\layoutlines
   \fi \fi
   \c_page_mul_n_of_lines\noflines}

\unexpanded\def\page_mul_command_set_vsize
  {\page_one_command_set_vsize % indeed?
   \page_mul_set_n_of_lines
   \d_page_mul_temp\nofcolumns\dimexpr
      \c_page_mul_n_of_lines\openlineheight
     +\multicolumnovershootratio\openlineheight % collect enough data
   \relax
   \global\vsize\d_page_mul_temp
   \pagegoal    \d_page_mul_temp} % let's do it only here

%D It really starts here. After some checks and initializations we change the output
%D routine to continous multi||column mode. This mode handles columns that fill the
%D current and next full pages. The method used is (more or less) multiplying \type
%D {\vsize} and dividing \type {\hsize} by \type {\nofcolumns}. More on this can be
%D found in the \TeX book. We save the top of the current page in box
%D \type {\b_page_mul_preceding}.
%D
%D We manipulate \type {\topskip} a bit, just to be shure that is has no
%D flexibility. This has te be done every time a font switch takles place, because
%D \type {\topskip} can depend on this.

\newconstant\c_page_mul_routine

\setnewconstant\c_page_mul_routine_regular   \zerocount
\setnewconstant\c_page_mul_routine_intercept \plusone
\setnewconstant\c_page_mul_routine_continue  \plustwo
\setnewconstant\c_page_mul_routine_balance   \plusthree
\setnewconstant\c_page_mul_routine_error     \plusfour

\unexpanded\def\page_mul_command_routine
  {\ifcase\c_page_mul_routine
     \page_one_command_routine
   \or
     \page_mul_routine_intercept
   \or
     \page_mul_routine_continue
   \or
     \page_mul_routine_balance
   \or
     \page_mul_routine_error
   \fi}

\def\page_mul_routine_intercept
  {\global\setbox\b_page_mul_preceding\vbox
     {\page_otr_command_flush_top_insertions
      \unvbox\normalpagebox}}

\def\page_mul_routine_error
  {\showmessage\m!columns3\empty
   \page_otr_construct_and_shipout\unvbox\normalpagebox\zerocount} % three arguments

%D When we leave the multi||column mode, we have to process the not yet shipped out
%D part of the columns. When we don't balance, we simply force a continuous output,
%D but a balanced output is more tricky.
%D
%D First we try to fill up the page and when all or something is left we try to
%D balance things. This is another useful adaption of the ancesters of these
%D macro's. It takes some reasoning to find out what happens and maybe I'm making
%D some mistake, but it works.
%D
%D Voiding box \type {\b_page_mul_preceding} is sometimes necessary, e.g. when there is no
%D text given between \type {\begin..} and \type {\end..}. The \type {\par} is
%D needed!

%D Because some initializations happen three times, we defined a macro for
%D them. Erasing \type{\everypar} is needed because we don't want anything
%D to interfere.

\unexpanded\def\page_mul_initialize_variables
  {\reseteverypar
   \dontcomplain
   \settopskip
   \setmaxdepth
   \topskip        1\topskip
   \splittopskip    \topskip
   \splitmaxdepth   \maxdepth
   \boxmaxdepth     \maxdepth % dangerous
   \emergencystretch\zeropoint
   \relax} % sometimes needed !

%D Flushing the page comes to pasting the columns together and appending the result
%D to box \type {\b_page_mul_preceding}, if not void. I've seen a lot of implementations in
%D which some skip was put between normal text and multi||column text. When we don't
%D want this, the baselines can be messed up. I hope the seemingly complicated
%D calculation of a correction \type {\kern} is adequate to overcome this. Although
%D not watertight, spacing is taken into account and even multiple mode changes on
%D one page go well. But cross your fingers and don't blame me.
%D
%D One of the complications of flushing out the boxes is that \type {\b_page_mul_preceding}
%D needs to be \type {\unvbox}'ed, otherwise there is too less flexibility in the
%D page when using \type {\raggedbottom}. It took a lot of time before these kind of
%D problems were overcome. Using \type {\unvbox} at the wrong moment can generate
%D \type {\page_mul_routine_error}'s.
%D
%D One can use the macros \type {\maxcolumnheight} and \type {\maxcolumndepth} when
%D generating material between columns as well as postprocessing column lines.

\newdimen\maxcolumnheight
\newdimen\maxcolumndepth

\newbox\columnpagebox

\def\page_mul_calculate_column_result_dimensions
  {\maxcolumnheight\zeropoint
   \maxcolumndepth \zeropoint
   \dohandleallcolumnscs\page_mul_calculate_column_result_dimensions_step}

\def\page_mul_calculate_column_result_dimensions_step
  {\ifdim\ht\currentcolumnbox>\maxcolumnheight
     \maxcolumnheight\ht\currentcolumnbox
   \fi
   \ifdim\dp\currentcolumnbox>\maxcolumndepth
     \maxcolumndepth\dp\currentcolumnbox
   \fi}

\setnewconstant\multicolumntopflushmethod\plusone % 0: no correction, 1: correction when topstuff, 2: correction, 3: correction++
\setnewconstant\multicolumntopalignmethod\plustwo % 0: nothing, 1: force grid, 2: follow grid

\def\page_mul_flush_preceding_normal
  {\unvbox\b_page_mul_preceding}

\def\page_mul_flush_preceding_ongrid
  {\scratchdimen\dimexpr
     \savedpagetotal
    -\d_page_mul_preceding_height
    -\d_page_mul_preceding_depth
    -\topskip
   \relax
   \box\b_page_mul_preceding
   \kern\scratchdimen}

\def\page_mul_flush_packaged_columns_continued
  {\bgroup
   \page_mul_flush_packaged_columns_indeed
   \box\columnpagebox
   \egroup}

\def\page_mul_flush_packaged_columns_balanced
  {\bgroup
   \page_mul_flush_packaged_columns_indeed
   % messy correction, we need to rewrite this module (newcolumns)
   \setbox\columnpagebox\vbox
     {\offinterlineskip
      \scratchdimen\htdp\columnpagebox
      \box\columnpagebox
      \vskip-\scratchdimen}%
   \ht\columnpagebox\dimexpr
     \noflines\openlineheight
     -\openstrutdepth
     \ifgridsnapping
        % quick hack (at least it works with itemize)
     \else
       -\openlineheight
       +\topskip
     \fi
   \relax
   \dp\columnpagebox\openstrutdepth
   % end of mess
   \box\columnpagebox
   \egroup}

\def\page_mul_synchronize_marks
  {\dohandleallcolumns{\page_marks_synchronize_column\plusone\nofcolumns\mofcolumns\currentcolumnbox}}

\def\page_mul_flush_packaged_columns_indeed
  {\ifvoid\b_page_mul_preceding
     \setfalse\c_page_mul_preceding_present % will be set elsewhere
   \else
     \settrue\c_page_mul_preceding_present
     \page_apply_postprocessors_box\b_page_mul_preceding
   \fi
   \forgetall
   \page_mul_initialize_variables
   \page_mul_calculate_column_result_dimensions
   \page_mul_postprocess_linenumbers
   \page_mul_synchronize_marks
   \page_mul_postprocess_lines
   \page_mul_postprocess_columns
   \dohandleallcolumns
     {\global\setbox\currentcolumnbox\hpack to \d_page_mul_used_width
        {\box\currentcolumnbox}%
      \wd\currentcolumnbox\d_page_mul_used_width
      \ifheightencolumns
        \ht\currentcolumnbox\d_page_mul_forced_height
      \fi}%
   \page_mul_calculate_column_result_dimensions
   \overlaycolumnfootnotes
   \setbox\columnpagebox\vpack % \vbox
     {\ifconditional\c_page_mul_reverse\reversehpack\else\naturalhpack\fi to \makeupwidth
        {\hskip\ifconditional\c_page_mul_reverse\d_page_mul_rightskip\else\d_page_mul_leftskip\fi\relax
         \dohandleallcolumns
           {\finishcolumnbox
               {\setbox\scratchbox\hpack
                   {\ifx\finishcolumnbox\relax\else\strut\fi
                   \box\currentcolumnbox}% hm, why strut
               \anch_mark_column_box\scratchbox\currentcolumn
               \box\scratchbox}%
               \hfil}%
         \unskip
         \hskip\ifconditional\c_page_mul_reverse\d_page_mul_leftskip\else\d_page_mul_rightskip\fi}}%
   \scratchdimen\zeropoint
   \dohandleallcolumns
     {\ifdim-\ht\currenttopcolumnbox<\scratchdimen
        \scratchdimen-\ht\currenttopcolumnbox
      \fi
      \global\setbox\currenttopcolumnbox\emptybox}%
   \advance\scratchdimen \ht\columnpagebox
   \setbox\scratchbox\hbox to \makeupwidth % between can be something so no \hpack
     {\vrule
        \s!width \zeropoint
        \s!height\scratchdimen
        \s!depth \dp\columnpagebox
      \dostepwiserecurse\plustwo\nofcolumns\plusone{\hfil\page_mul_between_columns}\hfil}%
   \setbox\columnpagebox\hpack
     {\box\columnpagebox
      \hskip-\makeupwidth
      \box\scratchbox}%
   \page_mul_postprocess_page
   \ifconditional\c_page_mul_preceding_present
     \settrue\c_page_mul_preceding_present
     % next some incredible crappy code
     \ifcase\multicolumntopalignmethod
       \page_mul_flush_preceding_normal % not on grid
     \or
       \page_mul_flush_preceding_ongrid % force on grid
     \else\ifgridsnapping
       \page_mul_flush_preceding_ongrid % obey grid settings, force on grid
     \else
       \page_mul_flush_preceding_normal % ignore grid settings, not on grid
     \fi \fi
   \fi
   \global\d_page_mul_preceding_height\zeropoint
   \page_otr_command_set_vsize
   \dosomebreak\nobreak % hm, only needed when topstuff
   \ifgridsnapping \else
     \ifcase\multicolumntopflushmethod
       % sometimes method 1 goes wrong, so we need a way out; best sort this out
       % when we run into it again
     \or
       % \input tufte \startcolumns \showbaselines \input tufte \stopcolumns \input tufte
       \ifconditional\c_page_mul_preceding_present
        %          \scratchdimen\topskip
        %          \advance\scratchdimen -\openstrutheight
        %          \nointerlineskip
        %          \vskip-\scratchdimen
         \nointerlineskip
         \vskip\dimexpr\openstrutheight-\topskip\relax
       \fi
     \or
        %        \scratchdimen\topskip
        %        \advance\scratchdimen -\openstrutheight
        %        \nointerlineskip
        %        \vskip-\scratchdimen
       \nointerlineskip
       \vskip\dimexpr\openstrutheight-\topskip\relax
     \or
       % untested but maybe handy
        %        \scratchdimen\topskip
        %        \advance\scratchdimen -\openstrutheight
        %        \nointerlineskip
        %        \vskip-\scratchdimen
        %        \vskip-\lineheight
        %        \vbox{\strut}%
       \nointerlineskip
       \vskip\dimexpr\openstrutheight-\topskip-\lineheight\relax
       \vbox{\strut}%
     \fi
   \fi
   \prevdepth\openstrutdepth
   \nointerlineskip
   \dp\columnpagebox\zeropoint
   \global\finalcolumnheights\ht\columnpagebox
   \getnoflines\finalcolumnheights
   \global\finalcolumnlines\noflines}

%D In case one didn't notice, finaly \type{\finishcolumnbox} is applied to
%D all boxes. One can use these hooks for special purposes.
%D
%D Once upon a time I wanted to manipulate the individual lines in a column.
%D This feature is demonstrated in the two examples below.
%D
%D \startbuffer
%D \def\postprocesscolumnline#1% or \postprocesscolumnbox
%D   {\ruledhbox{\box#1}\hss}
%D
%D \startcolumns[n=4]
%D \dorecurse{25}{line: \recurselevel\par}
%D \stopcolumns
%D \stopbuffer
%D
%D \typebuffer
%D
%D Here we show the natural width of the lines:
%D
%D {\getbuffer}
%D
%D The next example does a bit more advanced manipulation:
%D
%D \startbuffer
%D \def\postprocesscolumnline#1%
%D   {\ifodd\currentcolumn
%D      \hfill\unhbox#1\relax
%D    \else
%D      \relax\unhbox#1\hfill
%D    \fi}
%D
%D \startcolumns[n=4]
%D \dorecurse{25}{line \recurselevel\par}
%D \stopcolumns
%D \stopbuffer
%D
%D \typebuffer
%D
%D Here we also see an application of \type{\currentcolumn}:
%D
%D {\getbuffer}
%D
%D This feature is implemented using the reshape macros presented
%D in \type{supp-box}.

%ifdefined\page_postprocessors_column\else\let\page_postprocessors_column\relax\fi % operates on passed box
\ifdefined\postprocesscolumnline     \else\let\postprocesscolumnline     \relax\fi % operates on passed box
\ifdefined\postprocesscolumnbox      \else\let\postprocesscolumnbox      \relax\fi % operates on passed box
\ifdefined\postprocesscolumnpagebox  \else\let\postprocesscolumnpagebox  \relax\fi % operates on passed box

%def\page_mul_postprocess_linenumbers{\ifx\page_postprocessors_column\relax\else\page_mul_postprocess_linenumbers_indeed\fi}
\def\page_mul_postprocess_lines      {\ifx\postprocesscolumnline     \relax\else\page_mul_postprocess_lines_indeed      \fi}
\def\page_mul_postprocess_columns    {\ifx\postprocesscolumnbox      \relax\else\page_mul_postprocess_columns_indeed    \fi}
\def\page_mul_postprocess_page       {\ifx\postprocesscolumnpagebox  \relax\else\page_mul_postprocess_page_indeed       \fi}

% \def\page_mul_postprocess_linenumbers_indeed
%   {\dohandleallcolumns{\page_apply_postprocessors_column\currentcolumnbox}}

\def\page_mul_postprocess_linenumbers
  {\dohandleallcolumns{\page_apply_postprocessors_column\currentcolumnbox}}

\def\page_mul_postprocess_lines_indeed
  {\dohandleallcolumnscs\page_mul_postprocess_lines_step}

\def\page_mul_postprocess_lines_step % TODO: use lua solution instead
   {\global\setbox\currentcolumnbox\vtop
      {\beginofshapebox
       \unvbox\currentcolumnbox
       \unskip\unskip
       \endofshapebox
       \reshapebox
         {\scratchheight\ht\shapebox
          \scratchdepth \dp\shapebox
          \setbox\shapebox\hbox to \hsize
            {\postprocesscolumnline\shapebox}%
          \ht\shapebox\scratchheight
          \dp\shapebox\scratchdepth
          \box\shapebox}%
       \flushshapebox
       \reseteverypar
       \parskip\zeropoint % = \forgetall
       \verticalstrut
       \vskip-\struttotal
       \vfil}}

\def\page_mul_postprocess_columns_indeed
  {\dohandleallcolumnscs\page_mul_postprocess_columns_step}

\def\page_mul_postprocess_columns_step
  {\global\setbox\currentcolumnbox\hbox
     {\postprocesscolumnbox\currentcolumnbox}}

\def\page_mul_postprocess_page_indeed
  {\postprocesscolumnpagebox\columnpagebox}

%D Here comes the simple splitting routine. It's a bit longer than expected because
%D of ragging bottoms or not. This part can be a bit shorter but I suppose that I
%D will forget what happens. The splitting takes some already present material
%D (think of floats) into account!
%D
%D First we present some auxiliary routines. Any material, like for instance floats,
%D that is already present in the boxes is preserved.

\newdimen\d_page_mul_split_height_used
\newdimen\d_page_mul_split_height_max

\def\page_mul_split_column#1#2#3#4% copy or box
  {\bgroup
   \ifdim\ht#4>\zeropoint
     \d_page_mul_split_height_used#3\relax
     \d_page_mul_split_height_max\d_page_mul_split_height_used
     \advance\d_page_mul_split_height_used -\ht#4%
     \columnfootnotecorrection{#1}\d_page_mul_split_height_used
     \setbox\scratchbox\vsplit#2 to \d_page_mul_split_height_used
     \global\setbox#1\vbox to \d_page_mul_split_height_max
       {\ifgridsnapping
          \scratchdimen\dimexpr\topskip-\openstrutheight\relax
          \vskip\scratchdimen
          \copy#4%
          \vskip-\scratchdimen
        \else
          \unvcopy#4%
        \fi
        \fuzzysnappedbox\unvbox\scratchbox
        \fakecolumnfootnotes{#1}}%
   \else\ifcase\c_strc_notes_page_location
     \global\setbox#1\vsplit#2 to #3%
     \global\setbox#1\vbox
       {\fuzzysnappedbox\unvbox{#1}}% % or \box ?
   \else
     \columnfootnotecorrection{#1}{#3}%
     \setbox\scratchbox\vsplit#2 to #3%
     \global\setbox#1\vbox to #3%
       {\fuzzysnappedbox\unvbox\scratchbox
        \fakecolumnfootnotes{#1}}%
   \fi \fi
   \egroup}

\def\page_mul_split_current_column#1#2%
  {\page_mul_split_column\currentcolumnbox{#1}{#2}\currenttopcolumnbox}

\def\page_mul_split_first_column#1#2%
  {\page_mul_split_column\firstcolumnbox{#1}{#2}\firsttopcolumnbox}

\def\page_mul_split_last_column#1#2%
  {\global\setbox\lastcolumnbox\vbox
     {\unvcopy\lasttopcolumnbox
      \fuzzysnappedbox\unvbox{#1}%
      \fakecolumnfootnotes\lastcolumnbox}}

%D NEW: still to be documented.

    \def\fakecolumnfootnotes#1%
      {\relax
       \ifcase\c_strc_notes_page_location\else
         \ifnum#1=\lastcolumnbox
           \fakenotes
         \fi
       \fi}

    \def\columnfootnotecorrection#1#2%
      {\relax
       \ifcase\c_strc_notes_page_location
         % page notes
       \or
         \ifnum#1=\firstcolumnbox\relax
           \calculatetotalclevernoteheight
           \advance#2 -\totalnoteheight
         \fi
       \else
         \ifnum#1=\lastcolumnbox\relax
           \calculatetotalclevernoteheight
           \advance#2 -\totalnoteheight
         \fi
       \fi}

    \def\overlaycolumnfootnotes
      {\relax
       \ifcase\c_strc_notes_page_location
         % page
       \or
         \checknotepresence \ifnotespresent \page_mul_notes_flush_first_column \fi
       \or
         \checknotepresence \ifnotespresent \page_mul_notes_flush_last_column \fi
       \fi}

    \newbox\b_page_mul_notes

    \def\page_mul_notes_flush_first_column
      {\begingroup
       \setbox\b_page_mul_notes\vbox{\placenoteinserts}%
       \ifzeropt\ht\b_page_mul_notes
         % can't happen as we already checked
       \else
         \page_mul_set_n_of_lines
         \advance\c_page_mul_n_of_lines \minustwo
         \scratchdimen\dimexpr\c_page_mul_n_of_lines\lineheight+\topskip\relax
         \setbox\b_page_mul_notes\hpack{\lower\scratchdimen\box\b_page_mul_notes}%
         \ht\b_page_mul_notes\openstrutheight
         \dp\b_page_mul_notes\openstrutdepth
         \wd\b_page_mul_notes\zeropoint
         \scratchdimen\ht\firstcolumnbox
         \global\setbox\firstcolumnbox\vbox to \scratchdimen
           {\box\firstcolumnbox
            \vskip-\scratchdimen
            \box\b_page_mul_notes}%
       \fi
       \endgroup}

    \def\page_mul_notes_flush_last_column
      {\begingroup
       \setbox\b_page_mul_notes\vbox{\placenoteinserts}%
       \ifzeropt\ht\b_page_mul_notes
         % can't happen as we already checked
       \else
         % maybe here also \page_mul_set_n_of_lines
         \scratchdimen\dimexpr\ht\firstcolumnbox-\openstrutdepth\relax % \strutdp
         \getnoflines\scratchdimen
         \advance\noflines \minustwo
         \scratchdimen\dimexpr\noflines\lineheight+\topskip\relax
         \setbox\b_page_mul_notes\hpack{\lower\scratchdimen\box\b_page_mul_notes}%
         \ht\b_page_mul_notes\openstrutheight
         \dp\b_page_mul_notes\openstrutdepth
         \wd\b_page_mul_notes\zeropoint
         \scratchdimen\ht\lastcolumnbox
         \global\setbox\lastcolumnbox\vbox to \scratchdimen
           {\box\lastcolumnbox
            \vskip-\scratchdimen
            \box\b_page_mul_notes}%
       \fi
       \endgroup}

%D Here comes the routine that splits the long box in columns. The macro \type
%D {\page_mul_flush_floats} can be used to flush either floats that were present before
%D the multi||column mode was entered, or floats that migrate to next columns.
%D Flushing floats is a delicate process.

\def\page_mul_routine_continue
  {\bgroup
   \forgetall
   \page_mul_initialize_variables
 % \dimen0=\makeupheight
 % \advance\dimen0 -\d_page_mul_preceding_height
 % \settotalinsertionheight
 % \advance\dimen0 -\totalinsertionheight
 % \ifgridsnapping % evt altijd, nog testen
 %   \getnoflines{\dimen0}
 %   \dimen0=\noflines\openlineheight
 % \fi
   \page_mul_set_n_of_lines
   \d_page_mul_balance_target\c_page_mul_n_of_lines\openlineheight
   \ifconditional\c_page_mul_trace
     \writestatus\m!columns{continue: lines=\the\c_page_mul_n_of_lines, target=\the\d_page_mul_balance_target, textheight=\the\textheight}%
   \fi
   \dohandleallcolumns
     {\page_mul_split_current_column\normalpagebox\d_page_mul_balance_target}%
   \setbox\b_page_mul_preceding_rest_of_page\vbox{\unvbox\normalpagebox}%
   \ifinheritcolumns
     \ifcase\bottomraggednessmode
       % 0 = ragged
       \dohandleallcolumns
         {\global\setbox\currentcolumnbox\vbox to \ht\firstcolumnbox
            {\scratchdepth\dp\currentcolumnbox
             \unvbox\currentcolumnbox
             \vskip\dimexpr\openstrutdepth-\scratchdepth\relax
             \prevdepth\openstrutdepth % \strutdp
             \vfill}}%
       \strc_notes_check_if_bottom_present
      %\ifconditional\c_notes_bottom_present \else
      %  \dimen0\ht\firstcolumnbox % ??
      %\fi
     \or
       % 1 = normal
       \advance\d_page_mul_balance_target\maxdepth
       \dohandleallcolumns
         {\global\setbox\currentcolumnbox\vbox to \d_page_mul_balance_target
            {\unvbox\currentcolumnbox}}%
     \or
       % 2 = baseline
       % the columns are on top of the baseline
     \fi
   \else
     \dohandleallcolumns
       {\global\setbox\currentcolumnbox\vbox to \d_page_mul_balance_target
          {\ifstretchcolumns
             \unvbox\currentcolumnbox
           \else
             \unvbox\currentcolumnbox % wel of niet \unvbox ?
             \vfill
           \fi}}%
     \dohandleallcolumns
       {\ht\currentcolumnbox\d_page_mul_balance_target}% redundant
   \fi
   \setbox\b_page_mul_preceding\vbox{\page_mul_flush_packaged_columns_continued}%
   \page_otr_construct_and_shipout\box\b_page_mul_preceding\zerocount % three arguments
   \page_otr_command_set_hsize
   \page_otr_command_set_vsize
   \page_mul_flush_floats
   \unvbox\b_page_mul_preceding_rest_of_page
   % \penalty\outputpenalty % gaat gruwelijk mis in opsommingen
   \egroup}

%D And this is the balancing stuff. Again, part of the routine is dedicated to
%D handling ragged bottoms, but here we also see some handling concerning the
%D stretching of columns. We set \type {\widowpenalty} at~0, which enables us to
%D balance columns with few lines. The use of \type {\box2} and \type {\box4}
%D garantees a more robust check when skips are used.

\newbox        \b_page_mul_balance_content
\newbox        \b_page_mul_balance_first_column
\newbox        \b_page_mul_balance_column
\newconstant   \c_page_mul_balance_tries_max
\newcount      \c_page_mul_balance_tries
\newdimen      \d_page_mul_balance_target
\newdimen      \d_page_mul_balance_target_less
\newdimen      \d_page_mul_balance_natural_height
\newdimen      \d_page_mul_balance_regular_height
\newdimen      \d_page_mul_balance_step
\newdimen      \d_page_mul_balance_fuzzyness
\newdimen      \d_page_mul_balance_threshold
\newconditional\c_page_mul_balance_possible

\c_page_mul_balance_tries_max 250 % 100 is too small when floats are involved

\def\page_mul_routine_balance
  {\bgroup
   % why no \forgetall here
   \page_mul_initialize_variables
   \widowpenalty\zerocount
   \setbox\b_page_mul_balance_content\vbox{\unvbox\normalpagebox}%
   \ifdim\ht\b_page_mul_balance_content>\openlineheight % at least one line
     \ifnum\c_page_mul_balance_minimum<\plustwo % balance anyway
       \settrue\c_page_mul_balance_possible
     \else % check criterium to available lines
       \getnoflines{\ht\b_page_mul_balance_content}%
       \divide\noflines \nofcolumns \relax
       \ifnum\noflines<\c_page_mul_balance_minimum \relax
         \ifdim\dimexpr\ht\b_page_mul_balance_content+\ht\firsttopcolumnbox+\openlineheight\relax>\makeupheight
           \settrue\c_page_mul_balance_possible % column exceeding text height
         \else
           \setfalse\c_page_mul_balance_possible % it seems to fit
         \fi
       \else
         \settrue\c_page_mul_balance_possible % balance indeed
       \fi
     \fi
   \else
     \setfalse\c_page_mul_balance_possible % balancing does not make sense
   \fi
   \ifconditional\c_page_mul_balance_possible % start balancing, was: \ifdim\ht\b_page_mul_balance_content>\openlineheight
     \page_mul_balance_try_one
     \ifinheritcolumns
       \page_mul_balance_try_two
     \else
       \page_mul_balance_try_three
     \fi
   \else
     % a one liner is not properly handled here, so best rewrite the text then
     \showmessage\m!columns{10}\empty
     \global\setbox\firstcolumnbox\vbox{\unvbox\b_page_mul_balance_content}%
   \fi
   \c_page_mul_routine\c_page_mul_routine_error
   \baselinebottom % forces depth in separation rule
   \page_mul_flush_packaged_columns_balanced
   \page_mul_eject_page
   \egroup}

\def\page_mul_eject_page
  {%\ifdim\pagetotal>\textheight
   %  \page_otr_trigger_output_routine % new, but wrong as fails on mixed-001.tex (wrong pagetotal at this point)
   %\else
     \allowbreak
   }%\fi}

\def\page_mul_balance_try_one
  {\d_page_mul_balance_target\dimexpr\ht\b_page_mul_balance_content+\topskip-\baselineskip\relax
   \dohandleallcolumns
     {\advance\d_page_mul_balance_target \ht\currenttopcolumnbox}%
   \divide\d_page_mul_balance_target \nofcolumns
   \vbadness\plustenthousand
   \c_page_mul_balance_tries\zerocount
   \bgroup
   \ifgridsnapping
     \d_page_mul_balance_step\lineheight
   \else
     \d_page_mul_balance_step\spacingfactor\onepoint % rubish
   \fi
   \doloop\page_mul_balance_try_one_attempt
   \page_mul_balance_try_one_attempt_final
   \ifnum\c_page_mul_balance_tries>\c_page_mul_balance_tries_max\relax
     \showmessage\m!columns7\empty
   \else
     \showmessage\m!columns8{\the\c_page_mul_balance_tries}%
   \fi
   \egroup}

\def\page_mul_balance_try_one_attempt
  {\advance\c_page_mul_balance_tries \plusone
   \global\setbox\b_page_mul_preceding_rest_of_page\copy\b_page_mul_balance_content\relax
   \page_mul_split_first_column\b_page_mul_preceding_rest_of_page\d_page_mul_balance_target
   \dohandlemidcolumns
     {\page_mul_split_current_column\b_page_mul_preceding_rest_of_page\d_page_mul_balance_target}%
   \page_mul_split_last_column\b_page_mul_preceding_rest_of_page\d_page_mul_balance_target
   \setbox\b_page_mul_balance_first_column\vbox{\unvcopy\firstcolumnbox}%
   \d_page_mul_balance_natural_height\zeropoint
   \dohandleallcolumns\page_mul_balance_try_one_attempt_step
   \advance\d_page_mul_balance_natural_height -.0005pt % (33sp) get rid of accurracy problem, pretty new
   \ifnum\c_page_mul_balance_tries>\c_page_mul_balance_tries_max\relax
     \exitloop
   \else\ifdim\d_page_mul_balance_natural_height>\ht\b_page_mul_balance_first_column
     \advance\d_page_mul_balance_target \d_page_mul_balance_step\relax
   \else
     \exitloop
   \fi\fi}

% \def\page_mul_balance_try_one_attempt_final
%   {\dohandleallcolumns
%      {\global\setbox\currentcolumnbox\vbox{\unvcopy\currentcolumnbox}}}
%
% \def\page_mul_balance_try_one_attempt_step
%   {\setbox\b_page_mul_balance_column\vbox
%      {\unvcopy\currentcolumnbox
%       \unpenalty
%       \unskip
%       \unpenalty
%       \unskip}% maybe better in main splitter
%    \ifdim\ht\b_page_mul_balance_column>\d_page_mul_balance_natural_height
%      \d_page_mul_balance_natural_height\ht\b_page_mul_balance_column
%    \fi}
%
% In mkiv we juggle node lists and we cannot work on copies that easily but in
% practice context hardly uses copies except here. So, the next variant doesn't
% use copies but the original in the final result, for which we need an extra
% split pass. A simple test case is:
%
% \starttext
%     \startcolumns
%         \inleft{!} x \par x
%     \stopcolumns
% \stoptext

\def\page_mul_balance_try_one_attempt_final % we need this because we want to have the non copied content
  {\global\setbox\b_page_mul_preceding_rest_of_page\box\b_page_mul_balance_content
   \page_mul_split_first_column\b_page_mul_preceding_rest_of_page\d_page_mul_balance_target
   \dohandlemidcolumns
     {\page_mul_split_current_column\b_page_mul_preceding_rest_of_page\d_page_mul_balance_target}%
   \page_mul_split_last_column\b_page_mul_preceding_rest_of_page\d_page_mul_balance_target
   \dohandleallcolumns
     {\global\setbox\currentcolumnbox\vbox{\unvbox\currentcolumnbox}}}

\def\page_mul_balance_try_one_attempt_step
  {\setbox\b_page_mul_balance_column\vbox
     {\unvbox\currentcolumnbox % was copy but not needed with the above
      \unpenalty
      \unskip
      \unpenalty
      \unskip}% maybe better in main splitter
   \ifdim\ht\b_page_mul_balance_column>\d_page_mul_balance_natural_height
     \d_page_mul_balance_natural_height\ht\b_page_mul_balance_column
   \fi}

% We cannot assume that the first column is the tallest, if only because we may
% have an aborted balance (one line in the first column and a graphic in the
% second one).

\def\page_mul_balance_try_two
  {\d_page_mul_balance_target\zeropoint
   \dohandleallcolumns
     {\ifdim\ht\currentcolumnbox>\d_page_mul_balance_target
        \d_page_mul_balance_target\ht\currentcolumnbox
      \fi}%
   \d_page_mul_balance_target_less\dimexpr\d_page_mul_balance_target-\openlineheight\relax
   \dohandleallcolumnscs\page_mul_balance_try_two_step}

\def\page_mul_balance_try_two_step
  {\d_page_mul_balance_regular_height\ht\currentcolumnbox
   \d_page_mul_balance_threshold\plusten\openlineheight % funny value
   \global\setbox\currentcolumnbox\vbox to \d_page_mul_balance_target
     {\unvbox\currentcolumnbox
      \ifdim\d_page_mul_balance_regular_height>\d_page_mul_balance_threshold
        \ifdim\d_page_mul_balance_regular_height<\d_page_mul_balance_target
          \ifdim\d_page_mul_balance_regular_height>\d_page_mul_balance_target_less
            \vskip\zeropoint  % !!
          \else
            \vskip\openlineheight
            \vfill
          \fi
        \else
          \vskip\zeropoint
        \fi
      \else
        \vskip\openlineheight
        \vfill
      \fi}}

\def\page_mul_balance_try_three
  {\bgroup
   \ifstretchcolumns
     \d_page_mul_balance_target\ht\firstcolumnbox
     \d_page_mul_balance_fuzzyness\bottomtolerance\ht\firstcolumnbox
     \setbox\b_page_mul_balance_content\vbox{\unvcopy\lastcolumnbox}%
     \advance\d_page_mul_balance_target-\htdp\b_page_mul_balance_content\relax
     \ifdim\d_page_mul_balance_target>\openlineheight\relax
       \ifdim\d_page_mul_balance_target>\d_page_mul_balance_fuzzyness\relax
         % \stretchcolumnsfalse % beter good bad than bad good
         \showmessage\m!columns9\empty
       \fi
     \fi
   \fi
   \dohandleallcolumnscs\page_mul_balance_try_three_step
   \egroup}

\def\page_mul_balance_try_three_step
  {\global\setbox\currentcolumnbox\vbox to \ht\firstcolumnbox
     {\ifstretchcolumns
        \unvbox\currentcolumnbox
      \else
        \box\currentcolumnbox
        \vfill
      \fi}}

%D The multicolumn mechanism is incorporated in a \CONTEXT\ interface,
%D which acts like:
%D
%D \starttyping
%D \startcolumns[n=4,balance=no]
%D   some text
%D \stopcolumns
%D \stoptyping
%D
%D The setup is optional. The default behaviour of columns can be set
%D up with:
%D
%D \starttyping
%D \setupcolumns
%D   [n=2,
%D    balance=yes]
%D \stoptyping
%D
%D In this case, stretching is according to the way it's done outside columns
%D (\type{\inheritcolumnstrue}). Also we can setup the \type{tolerance} within a
%D column, the \type{distance} between columns and the fixed \type{height} of a
%D column.
%D
%D Here come the routines that handle the placement of column floats. Floats that
%D are to big migrate to the next column. Floats that are too wide, migrate to the
%D top of the next page, where they span as much columns as needed. Floats that are
%D left over from outside the multi||column mode are flushed first. In macro
%D \type{\page_otr_construct_and_shipout} the topfloats that are left from previous
%D text should be set.
%D
%D When there are some floats in the queue, we inhibit the flushing of floats on top
%D of columns. The number of waiting floats is preswent in \type{\savednoftopfloats}
%D and is saved. As long as there are floats waiting, the topfloats are places as if
%D we are outside multi||column mode. This is neccessary for e.g. multicolumn lists.
%D
%D When all those floats are flushed, we switch to the local flushing routine.

% \newbox  \floatlist
% \newbox  \savedfloatlist
%
% \def\page_floats_column_push_saved
%   {\ifconditional\c_page_floats_some_waiting
%      \showmessage\m!columns6{\the\savednoffloats}%
%      \global\setbox\savedfloatlist\box\floatlist
%      \xdef\page_floats_column_pop_saved
%        {\global\savednoffloats\the\savednoffloats
%         \global\setbox\floatlist\box\savedfloatlist
%         \global\noexpand\settrue\c_page_floats_some_waiting}%
%      \global\savednoffloats\zerocount
%      \global\setfalse\c_page_floats_some_waiting
%    \else
%      \glet\page_floats_column_pop_saved\relax
%    \fi}
%
% \let\page_floats_column_pop_saved\relax

% \def\page_mul_initialize_floats % messy as it adapts everypar
%   {\xdef\globalsavednoffloats{\the\savednoffloats}%
%    \ifnum\globalsavednoffloats>\zerocount
%      \setglobalcolumnfloats % hm, we always push so this never happens
%    \else
%      \setlocalcolumnfloats
%    \fi}

    \def\page_mul_initialize_floats % messy as it adapts everypar, we need to adapt this
      {\setlocalcolumnfloats}

    \newconditional\onlylocalcolumnfloats % temp hack as we will redo floats (grid snapping is also messy now)
    \newtoks       \everylocalcolumnfloatspar

    \unexpanded\def\page_mul_command_flush_floats
      {\ifconditional\onlylocalcolumnfloats
         \doflushcolumnfloats
       \else
         \page_one_command_flush_floats
       \fi}

    \unexpanded\def\page_mul_command_check_if_float_fits
      {\ifconditional\onlylocalcolumnfloats
         \docolumnroomfloat
       \fi}

    \unexpanded\def\page_mul_command_flush_saved_floats
      {\ifconditional\onlylocalcolumnfloats\relax
       \else
         \page_one_command_flush_saved_floats
       \fi}

    \unexpanded\def\page_mul_command_flush_top_insertions
      {\ifconditional\onlylocalcolumnfloats\relax
       \else
         \page_one_command_flush_top_insertions
       \fi}

    \appendtoks
        \flushnotes
        \page_mul_flush_float
       %\flushmargincontents
        \checkindentation
    \to \everylocalcolumnfloatspar

    \def\setlocalcolumnfloats
      {\settrue\onlylocalcolumnfloats
       \everypar\everylocalcolumnfloatspar
       \let\page_mul_flush_float \doflushcolumnfloat
       \let\page_mul_flush_floats\doflushcolumnfloats}

    \def\setglobalcolumnfloats
      {\setfalse\onlylocalcolumnfloats
       \reseteverypar
       \let\page_mul_flush_float \relax
       \let\page_mul_flush_floats\noflushcolumnfloats}

 % \def\noflushcolumnfloats
 %   {\bgroup
 %    \xdef\localsavednoffloats{\the\savednoffloats}%
 %    \global\savednoffloats\globalsavednoffloats
 %    \page_otr_command_flush_top_insertions
 %    \xdef\globalsavenoffloats{\the\savednoffloats}%
 %    \ifnum\globalsavednoffloats=\zerocount
 %      \setlocalcolumnfloats
 %    \fi
 %    \global\savednoffloats\localsavednoffloats
 %    \egroup}
 %
    \def\noflushcolumnfloats{\doflushcolumnfloats} % not yet redone

%D We need to calculate the amount of free space in a columns. When there is not
%D enough room, we migrate the float to the next column. These macro's are
%D alternatives (and look||alikes) of \type {\doroomfloat}. When a float is to wide,
%D for one column, it is moved to the top of the next page. Of course such moved
%D floats have to be taken into account when we calculate the available space. It's
%D a pitty that such things are no integral part of \TEX.

    \def\getcolumnstatus#1#2#3%
      {\dimen0=\ifdim\pagegoal<\maxdimen \pagetotal \else \zeropoint \fi
       \dimen2=\zeropoint
       \count255=\zerocount
       \dimen8=\makeupheight
       \advance\dimen8 -\d_page_mul_preceding_height
       \def\dogetcolumnstatus
         {\advance\count255 \plusone
          \advance\dimen2 \ht\currenttopcolumnbox
          \advance\dimen2 \dp\currenttopcolumnbox
          \dimen4\dimen2
          \advance\dimen4 \dimen0
          \dimen6=\count255\dimen8
          \ifdim\dimen4>\dimen6
          \else
            \let\dogetcolumnstatus\relax
          \fi}%
       \dohandleallcolumns{\dogetcolumnstatus}%
       \ifnum\count255=0 \count255=1 \fi
       #1=\count255
       #2=\dimen4
       #3=\dimen6 }

    \def\getinsertionheight
      {\ifdim\pagegoal<\maxdimen
         \bgroup
         \dimen0=\makeupheight
         \advance\dimen0 -\pagegoal
         \xdef\insertionheight{\the\dimen0}%
         \egroup
       \else
         \glet\insertionheight\zeropoint
       \fi}

    \def\docolumnroomfloat
      {\ifpostponecolumnfloats
         \global\setfalse\c_page_floats_room
       \else\ifconditional\c_page_floats_not_permitted
         \global\setfalse\c_page_floats_room
       \else
         \bgroup
         \getcolumnstatus{\count255}{\dimen0}{\dimen2}%
         \page_floats_get_info\s!text
         \setbox\scratchbox\vbox % tricky met objecten ?
           {\blank[\rootfloatparameter\c!spacebefore]
            \snaptogrid\vbox{\vskip\floatheight}}% copy?
         \advance\dimen0\dimexpr\ht\scratchbox+2\openlineheight+.5\lineheight\relax\relax % needed because goal a bit higher
         \ifdim\dimen0>\dimen2
           \global\setfalse\c_page_floats_room
         \else
           \global\settrue\c_page_floats_room
         \fi
         \ifdim\floatwidth>\hsize
           \showmessage\m!columns{11}\empty
           \global\setfalse\c_page_floats_room
         \fi
         \egroup
       \fi\fi}

%D Flushing one float is done as soon as possible, i.e. \type {\everypar}.
%D This means that (at the moment) sidefloats are not supported (overulled)!

    \newif\ifflushingcolumnfloats \flushingcolumnfloatstrue

    \def\doflushcolumnfloat
      {\ifpostponecolumnfloats\else\ifflushingcolumnfloats\ifconditional\c_page_floats_some_waiting
         \doflushcolumnfloatindeed
       \fi\fi\fi}

    \def\doflushcolumnfloatindeed
      {\bgroup
       \forgetall
       \let\doflushcolumnfloat\relax
       \getcolumnstatus{\mofcolumns}{\dimen0}{\dimen2}%
       \ifdim\dimen0>\zeropoint
         \page_floats_get_info\s!text
         \ifdim\floatwidth>\hsize
            % dropped ?
         \else
           \setbox2\vbox
             {\blank[\rootfloatparameter\c!spacebefore]
              \snaptogrid\vbox{\vskip\floatheight}}%
           \advance\dimen0 \ht2
           \ifdim\dimen0>\dimen2
             \ifnum\mofcolumns<\nofcolumns
               \advance\mofcolumns \plusone
               \ifdim\ht\currenttopcolumnbox=\zeropoint
                 \page_floats_flush\s!text\plusone
                 \global\setbox\currenttopcolumnbox\vbox
                   {\snaptogrid\vbox{\box\floatbox}
                    \whitespace % nodig ?
                    \blank[\rootfloatparameter\c!spaceafter]}%
                 \dimen4=\htdp\currenttopcolumnbox
                 \global\advance\vsize -\dimen4
                 \advance\dimen4 -\pagegoal
                 \pagegoal-\dimen4
                 \showmessage\m!columns{12}a%
               \else
                 \showmessage\m!columns{12}b%
               \fi
             \else
               \showmessage\m!columns{12}c%
             \fi
           \else
             \ifhmode{\setbox0\lastbox}\fi% waar is die er in geslopen
             \par
             \ifdim\prevdepth<\zeropoint \else % anders bovenaan kolom witruimte
               \nobreak
               \blank[\rootfloatparameter\c!spacebefore]
               \nobreak
             \fi
             \page_floats_flush\s!text\plusone
             \page_otr_command_flush_float_box
             \blank[\rootfloatparameter\c!spaceafter]
           \fi
         \fi
       \fi
       \egroup}

%D This one looks complicated. Upto \type{\nofcolumns} floats are placed,
%D taking the width of a float into account. This routine can be improved
%D on different ways:
%D
%D \startitemize[intro,packed]
%D \item taking into account some imaginary baseline, just to get the
%D       captions in line
%D \item multipass flushing until as many floats are displaced as possible
%D \stopitemize
%D
%D When handling lots of (small) floats spacing can get worse because of
%D lining out the columns.

    \def\doflushcolumnfloats
      {\ifpostponecolumnfloats\else
         \bgroup
         \forgetall
         \ifconditional\c_page_floats_some_waiting
           \dimen8\zeropoint
           \dimen4\zeropoint
           \count0\zerocount   % count0 can be used local
           \count2\nofcolumns  % count2 can be used local
           \dohandleallcolumns
             {\ifnum\count0>\zerocount % the wide one's reserved space
                \global\setbox\currenttopcolumnbox\vbox
                  {\snaptogrid\vbox
                     {\copy\currenttopcolumnbox
                      \hpack{\vphantom{\vskip\floatheight}}}% known from previous
                      \whitespace % nodig ?
                      \blank[\rootfloatparameter\c!spaceafter]}%
              \else
                \page_floats_get_info\s!text
                \ifdim\floatwidth>\hsize
                  \dimen0\dimexpr\floatwidth+\d_page_mul_distance+.5pt\relax
                  \dimen2\dimexpr\hsize     +\d_page_mul_distance+.5pt\relax
                  \divide\dimen0 \dimen2
                  \count0\dimen0
                  \advance\count0 \plusone
                  \ifnum\count0>\count2
                    \count0\zerocount
                  \else
                    \dimen0\dimexpr\count0\hsize+\count0\d_page_mul_distance-\d_page_mul_distance\relax
                    \page_floats_flush\s!text\plusone
                    \ifdim\floatwidth>\makeupwidth % better somewhere else too
                      \global\setbox\floatbox\hbox to \makeupwidth{\hss\box\floatbox\hss}%
                    \fi % otherwise the graphic may disappear
                    \global\setbox\floatbox\hbox to \dimen0
                      {\processaction[\rootfloatparameter\c!location] % how easy to forget
                         [   \v!left=>\box\floatbox\hss,
                            \v!right=>\hss\box\floatbox,
                          \s!default=>\hss\box\floatbox\hss,
                          \s!unknown=>\hss\box\floatbox\hss]}%
                  \fi
                  \showmessage\m!columns{13}\empty
                \else
                  \page_floats_flush\s!text\plusone
                  \ifdim\floatwidth>\makeupwidth % better somewhere else too
                    \global\setbox\floatbox\hbox to \makeupwidth{\hss\box\floatbox\hss}%
                  \fi % otherwise the graphic may disappear
                % \showmessage\m!columns{13}\empty
                \fi
                \ifdim\ht\floatbox>\zeropoint\relax
                  \global\setbox\currenttopcolumnbox\vbox
                    {\snaptogrid\vbox
                       {\box\currenttopcolumnbox % was copy
                        \box\floatbox}
                     \whitespace % nodig ?
                     \blank[\rootfloatparameter\c!spaceafter]}%
                \fi
                \dimen6\htdp\currenttopcolumnbox
              \fi
              \ifdim\dimen4<\ht\currenttopcolumnbox
                \dimen4\ht\currenttopcolumnbox
              \fi
              \advance\dimen8 \dimen6
              \advance\count2 \minusone
              \advance\count0 \minusone }%
           \page_otr_command_set_vsize
           \global\advance\vsize -\dimen8
           \pagegoal\vsize
         \else
           % \page_mul_command_flush_floats % does not snap!
         \fi
         \egroup
       \fi}

%D The next macro can be used to flush floats in the current stream. No
%D width checking is (yet) done.

    \def\insertcolumnfloats
      {\doloop
         {\ifconditional\c_page_floats_some_waiting
            \bgroup
            \forgetall
            % no check for width
            \page_floats_get
            \blank[\rootfloatparameter\c!spacebefore]
            \snaptogrid\vbox{\copy\floatbox}
            \blank[\rootfloatparameter\c!spaceafter]
            \egroup
          \else
            \exitloop
          \fi}}

%D This were the multi||column routines. They can and need to be improved
%D but at the moment their behaviour is acceptable.
%D
%D One inprovement can be to normalize the height of floats to $ n \times $
%D \type {\lineheight} with a macro like:
%D
%D \starttyping
%D \normalizevbox{...}
%D \stoptyping

% border case, should fit on one page
%
% \startcolumns
% 1 \input tufte  \par \placefigure{}{\framed[width=\hsize,height=3cm]{1}}
% 2 \input tufte  \par \placefigure{}{\framed[width=\hsize,height=3cm]{2}}
% 3 \input tufte  \par \placefigure{}{\framed[width=\hsize,height=3cm]{3}}
% \stopcolumns

\def\backgroundfinishcolumnbox
  {\inheritedcolumnsframed}
   % [\c!strut=\v!no,
   %  \c!width=\v!fit,
   %  \c!height=\v!fit,
   %  \c!align=]}

% to be reconsidered ... (in any case they need to be unexpandable sinze 2011.12.30)

\unexpanded\def\page_columns_align_option_yes {\stretchcolumnstrue \inheritcolumnsfalse}% todo: new key
\unexpanded\def\page_columns_align_option_no  {\stretchcolumnsfalse\inheritcolumnsfalse}% todo: new key
\unexpanded\def\page_columns_align_option_text{\stretchcolumnsfalse\inheritcolumnstrue }%

\newtoks\t_page_mul_initialize

\unexpanded\def\startcolumns
  {\dosingleempty\page_mul_start}

\def\page_mul_start[#1]% %% \startcolumns
  {\bgroup
   \ifinsidecolumns
     \page_mul_start_nop
   \else
     \iffirstargument
       \setupcolumns[#1]%
     \fi
     \nofcolumns\columnsparameter\c!n\relax
     \ifnum\nofcolumns>\plusone
       \page_mul_start_yes
     \else
       \page_mul_start_nop
     \fi
   \fi}

\unexpanded\def\page_mul_start_nop
  {\let\stopcolumns\page_mul_stop_nop}

\unexpanded\def\page_mul_stop_nop
  {\egroup}

\unexpanded\def\page_mul_start_yes
  {\whitespace
   \begingroup
   \let\stopcolumns\page_mul_stop_indeed
   \global\insidecolumnstrue
   \the\t_page_mul_initialize
   %
   \flushnotes
   \begingroup
   %
   \d_page_mul_leftskip\leftskip
   \d_page_mul_rightskip\rightskip
   \leftskip\zeropoint
   \rightskip\zeropoint
   %
   \widowpenalty\zerocount % will become option
   \clubpenalty \zerocount % will become option
   %
   \page_floats_column_push_saved
   %
   \ifdim\dimexpr\pagetotal+\parskip+\openlineheight\relax<\pagegoal
     \allowbreak
   \else
     \break % sometimes fails
   \fi
   \appendtoks
     \topskip1\topskip % best a switch
   \to \everybodyfont
   \the\everybodyfont  % ugly here
   \saveinterlinespace % ugly here
   %
   \initializecolumns\nofcolumns
   %
   \hangafter\zerocount
   \hangindent\zeropoint
   \reseteverypar
   \ifdim\pagetotal=\zeropoint \else
     \verticalstrut
     \vskip-\struttotal
   \fi
   \global\savedpagetotal\pagetotal
   \setupoutputroutine[\s!multicolumn]%
   \c_page_mul_routine\c_page_mul_routine_intercept
   \page_otr_trigger_output_routine % no \holdinginserts=1, can make footnote disappear !
   \global\d_page_mul_preceding_height\ht\b_page_mul_preceding
   \c_page_mul_routine\c_page_mul_routine_continue
   \page_mul_initialize_floats
   \dohandleallcolumns{\global\setbox\currenttopcolumnbox\emptybox}%
   \checkbegincolumnfootnotes
   \page_otr_command_set_hsize
   \page_otr_command_set_vsize}

\setnewconstant\multicolumnendsyncmethod\plusone % 1: old sync 2: new sync (cont-loc/project) / may fail ! ! ! !

\unexpanded\def\page_mul_stop_indeed
  {\relax
   \ifnum\multicolumnendsyncmethod=\plustwo
     \synchronizeoutput
   \else
     % don't collapse these
     \vskip \lineheight
     \vskip-\lineheight % take footnotes into account
   \fi
   \doflushcolumnfloat  % added recently
  %\doflushcolumnfloats % no, since it results in wrong top floats
   \flushnotes          % before start of columns
   \par
   \ifbalancecolumns
     \ifnum\multicolumnendsyncmethod=\plusone
       \c_page_mul_routine\c_page_mul_routine_continue
       \goodbreak
     \fi
     \c_page_mul_routine\c_page_mul_routine_balance
   \else
     \goodbreak
   \fi
   % still the multi column routine
   \page_otr_trigger_output_routine % the prevdepth is important, try e.g. toclist in
   \prevdepth\zeropoint % columns before some noncolumned text text
   %
   \c_page_mul_routine\c_page_mul_routine_regular
   %
   \ifvoid\b_page_mul_preceding\else
     \unvbox\b_page_mul_preceding
   \fi
   \global\d_page_mul_preceding_height\zeropoint
   \endgroup % here
   \nofcolumns\plusone
   \page_otr_command_set_vsize
   \checkendcolumnfootnotes
   \dosomebreak\allowbreak
   \page_floats_column_pop_saved
   %
   \global\insidecolumnsfalse
   \endgroup
   \egroup}%

\appendtoks
    \edef\p_option{\columnsparameter\c!option}%
    \ifx\p_option\v!background
        \let\finishcolumnbox\backgroundfinishcolumnbox
        \doifelseinset{\columnsparameter\c!offset}{\v!none,\v!overlay}
          {\d_page_mul_offset\zeropoint}%
          {\d_page_mul_offset\dimexpr\columnsparameter\c!offset-\columnsparameter\c!rulethickness\relax}%
    \else
        \d_page_mul_offset\zeropoint
    \fi
    \edef\p_command{\columnsparameter\c!command}%
    \ifx\p_command\empty \else
        \let\postprocesscolumnline\p_command
    \fi
    \edef\p_height{\columnsparameter\c!height}%
    \ifx\p_height\empty
        \d_page_mul_forced_height\textheight
        \heightencolumnsfalse
    \else
        \d_page_mul_forced_height\p_height\relax
        \heightencolumnstrue
    \fi
    \edef\p_direction{\columnsparameter\c!direction}%
    \ifx\p_direction\v!right
        \setfalse\c_page_mul_reverse
    \else
        \settrue\c_page_mul_reverse
    \fi
    \edef\p_balance{\columnsparameter\c!balance}%
    \ifx\p_balance\v!yes
        \balancecolumnstrue
    \else
        \balancecolumnsfalse
    \fi
    % % this won't work (blocked by check for overloading; too fuzzy anyway)
    % \installalign\v!yes {\page_columns_align_option_yes }% \stretchcolumnstrue \inheritcolumnsfalse
    % \installalign\v!no  {\page_columns_align_option_no  }% \stretchcolumnsfalse\inheritcolumnsfalse
    % \installalign\v!text{\page_columns_align_option_text}% \stretchcolumnsfalse\inheritcolumnstrue
    % %
    \stretchcolumnsfalse
    \inheritcolumnstrue
    \edef\p_align{\columnsparameter\c!align}%
    \ifx\p_align\empty \else
        \setupalign[\p_align]%
    \fi
    \edef\p_tolerance{\columnsparameter\c!tolerance}%
    \ifx\p_tolerance\empty \else
        \setuptolerance[\p_tolerance]%
    \fi
    \edef\p_blank{\columnsparameter\c!blank}%
    \ifx\p_blank\empty \else
        \setupblank[\p_blank]%
    \fi
    \ifdim\s_spac_whitespace_parskip>\zeropoint\relax
        \setupwhitespace[\p_blank]%
    \fi
    \c_page_mul_balance_minimum\columnsparameter\c!ntop\relax
    \edef\p_page_mul_rule{\columnsparameter\c!rule}%
    \expandnamespacemacro\??columnseparators\p_page_mul_rule\s!unknown
\to \t_page_mul_initialize

%D Columns breaks

\installcolumnbreakmethod \s!multicolumn \v!preference
  {\goodbreak}

% \installcolumnbreakmethod \s!multicolumn \v!yes
%   {\vskip\textheight
%    \penalty-200 % we can mark and intercept this
%    \vskip-\textheight}

\installcolumnbreakmethod \s!multicolumn \v!yes
   {\vskip .5\pagegoal
    \penalty-200 % we can mark and intercept this
    \vskip-.5\pagegoal}

%D Next we initialize the lot:

\setupcolumns
  [\c!n=2,
   \c!ntop=1,
   \c!command=,
   \c!direction=\v!right,
   \c!rule=\v!off,
   \c!tolerance=\v!tolerant,
   \c!distance=1.5\bodyfontsize, % influenced by switching
   \c!height=,
   \c!balance=\v!yes,
   \c!align=\v!text,
   \c!blank={\v!line,\v!fixed},
   \c!option=,
   \c!rulethickness=\linewidth,
   \c!offset=.5\bodyfontsize]

%D New: only at start of columns; may change ! Rather interwoven and therefore
%D to be integrated when the multi column modules are merged.

    \unexpanded\def\setupcolumnspan[#1]%
      {\getparameters[\??ks][#1]}

    \presetlocalframed
      [\??ks]

    \setupcolumnspan
      [\c!n=2,
       \c!offset=\v!overlay,
       \c!frame=\v!off]

    \newbox\b_page_columns_span \let\page_mul_postprocess_spanbox\gobbleoneargument

    \unexpanded\def\startcolumnspan
      {\dosingleempty\dostartcolumnspan}

    \unexpanded\def\stopcolumnspan
      {\egroup}

    \def\dostartcolumnspan[#1]%
      {\bgroup
       \setupcolumnspan[#1]%
       \forgetall
       \ifinsidecolumns
         \advance\hsize \d_page_mul_distance
         \hsize\@@ksn\hsize
         \advance\hsize -\d_page_mul_distance
       \fi
       \dowithnextboxcs\dofinishcolumnsetspan\vbox\bgroup
         %\topskipcorrection % becomes an option !
         \EveryPar{\begstrut\EveryPar{}}} % also !

    \def\dofinishcolumnsetspan
      {\setbox\b_page_columns_span\flushnextbox
       \ifinsidecolumns\wd\b_page_columns_span\hsize\fi
       \page_mul_postprocess_spanbox\b_page_columns_span
       \scratchdimen\ht\b_page_columns_span
       \setbox\b_page_columns_span\hbox % depth to be checked, probably option!
         {\localframed[\??ks][\c!offset=\v!overlay]{\box\b_page_columns_span}}%
       \ht\b_page_columns_span\scratchdimen
       \dp\b_page_columns_span\strutdp
       \wd\b_page_columns_span\hsize
       \ifinsidecolumns
         \ifnum\@@ksn>1
           \page_otr_command_set_vsize
           \dohandleallcolumns
             {\ifnum\currentcolumn>\@@ksn\else
                \global\setbox\currenttopcolumnbox=\vbox
                  {\ifnum\currentcolumn=1
                     \snaptogrid\vbox{\copy\b_page_columns_span}
                   \else
                     \snaptogrid\vbox{\vphantom{\copy\b_page_columns_span}}
                   \fi}%
                \wd\currenttopcolumnbox\hsize
                \global\advance\vsize -\ht\currenttopcolumnbox
              \fi}
           \pagegoal\vsize
         \else
           \snaptogrid\vbox{\box\b_page_columns_span}
         \fi
       \else
         \snaptogrid\vbox{\box\b_page_columns_span}
       \fi
       \endgraf
       \ifvmode\prevdepth\strutdp\fi
       \egroup}

%D Undocumented and still under development.\ifdefined\startsimplecolumns \else

\unexpanded\def\startsimplecolumns
  {\dosingleempty\page_mul_simple_start}

\def\page_mul_simple_start[#1]%
  {\bgroup
   \setsimplecolumnshsize[#1]%
   \nopenalties
   \setbox\scratchbox\vbox\bgroup
   \forgetall} % \blank[\v!disable]

\unexpanded\def\stopsimplecolumns
  {\removebottomthings
   \egroup
   \rigidcolumnbalance\scratchbox
   \egroup}

\unexpanded\def\setsimplecolumnshsize[#1]%
  {\getdummyparameters
     [\c!width=\hsize,
      \c!distance=1.5\bodyfontsize,
      \c!n=2,
      \c!lines=0,
      #1]%
   \edef\rigidcolumnlines
     {\directdummyparameter\c!lines}%
   \setrigidcolumnhsize
     {\directdummyparameter\c!width}%
     {\directdummyparameter\c!distance}%
     {\directdummyparameter\c!n}}

%D Moved here:

\unexpanded\def\page_mul_command_test_column
  {\dodoubleempty\page_mul_command_test_column_indeed}

\unexpanded\def\page_mul_command_test_column_indeed[#1][#2]% works on last column
  {\page_otr_command_flush_top_insertions\endgraf
   \ifdim\pagegoal<\maxdimen
     \ifdim\pagetotal<\pagegoal
       \d_page_tests_test\dimexpr
         \pagegoal
        -\pagetotal
         \ifdim\lastskip<\parskip+\parskip\fi
         \ifsecondargument+#2\fi
       \relax
       \getrawnoflines\d_page_tests_test % (raw)
       \ifnum#1>\noflines
         \column
       \fi
     \else
       \penalty-\plustenthousand % (untested)
     \fi
   \fi}

%D but fragile anyway.

\let\page_mul_command_package_contents\page_one_command_package_contents
\let\page_mul_command_flush_float_box \page_one_command_flush_float_box
\let\page_mul_command_flush_all_floats\page_one_command_flush_all_floats

\defineoutputroutine
  [\s!multicolumn]
  [\s!page_otr_command_routine                =\page_mul_command_routine,
   \s!page_otr_command_package_contents       =\page_mul_command_package_contents,
   \s!page_otr_command_set_vsize              =\page_mul_command_set_vsize,
   \s!page_otr_command_set_hsize              =\page_mul_command_set_hsize,
 % \s!page_otr_command_synchronize_hsize      =\page_mul_command_synchronize_hsize,
   \s!page_otr_command_next_page              =\page_mul_command_next_page,
   \s!page_otr_command_next_page_and_inserts  =\page_mul_command_next_page_and_inserts,
 % \s!page_otr_command_set_top_insertions     =\page_mul_command_set_top_insertions,
 % \s!page_otr_command_set_bottom_insertions  =\page_mul_command_set_bottom_insertions,
   \s!page_otr_command_flush_top_insertions   =\page_mul_command_flush_top_insertions,
 % \s!page_otr_command_flush_bottom_insertions=\page_mul_command_flush_bottom_insertions,
   \s!page_otr_command_check_if_float_fits    =\page_mul_command_check_if_float_fits,
 % \s!page_otr_command_set_float_hsize        =\page_mul_command_set_float_hsize,
   \s!page_otr_command_flush_float_box        =\page_mul_command_flush_float_box,
   \s!page_otr_command_side_float_output      =\page_mul_command_side_float_output,
   \s!page_otr_command_synchronize_side_floats=\page_mul_command_synchronize_side_floats,
   \s!page_otr_command_flush_floats           =\page_mul_command_flush_floats,
   \s!page_otr_command_flush_side_floats      =\page_mul_command_flush_side_floats,
   \s!page_otr_command_flush_saved_floats     =\page_mul_command_flush_saved_floats,
   \s!page_otr_command_flush_all_floats       =\page_mul_command_flush_all_floats,
 % \s!page_otr_command_flush_margin_blocks    =\page_mul_command_flush_margin_blocks, % not used
   \s!page_otr_command_test_column            =\page_mul_command_test_column
  ]

\installfloatmethod \s!multicolumn  \v!here   \page_mul_place_float_here
\installfloatmethod \s!multicolumn  \v!force  \page_mul_place_float_force
\installfloatmethod \s!multicolumn  \v!top    \page_mul_place_float_top
\installfloatmethod \s!multicolumn  \v!bottom \page_mul_place_float_bottom

\appendtoks
    \flushingcolumnfloatsfalse
\to \everybeforesectionheadhandle

\appendtoks
   \flushingcolumnfloatstrue
\to \everyaftersectionheadhandle

\protect \endinput