stable 1997.10.28

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+%D \module

+%D   [       file=supp-mul,

+%D        version=1995.03.01,

+%D          title=\CONTEXT\ Support Macros,

+%D       subtitle=Multi Column Output,

+%D         author=Hans Hagen,

+%D           date=\currentdate,

+%D      copyright={PRAGMA / Hans Hagen \& Ton Otten}]

+%C

+%C This module is part of the \CONTEXT\ macro||package and is

+%C therefore copyrighted by \PRAGMA. Non||commercial use is 

+%C granted. 

+

+\writestatus{loading}{Context Support Macros / Multi Column Output}

+

+\unprotect

+

+%D Multi||column output: the main routines

+%D

+%D The following macro's implement a multi||column output

+%D routine. The original implementation was based on Donald

+%D Knuth's implementation, which was adapted by Craig Platt to

+%D support balancing of the last page. I gradually adapted

+%D Platt's version to our needs but under certain

+%D circumstances things still went wrong. I considered all

+%D calls to Platt's \type{\balancingerror} as undesirable.

+

+\startmessages  dutch  library: columns 

+  title: kolommen

+      1: maximaal -- kolommen

+      2: gebruik eventueel \string\filbreak

+      3: probleempje, probeer [balanceren=nee]

+      4: plaatsblok boven nog niet mogelijk

+      5: plaatsblok onder nog niet mogelijk

+      6: -- plaatsblok(en) opgeschort

+      7: balanceren afgebroken na 100 stappen

+      8: gebalanceerd in -- stap(pen)

+      9: uitlijnen controleren!

+     10: (minder dan) 1 regel over

+     11: plaatsblok te breed voor kolom

+     12: plaatsblok verplaatst naar volgende kolom

+     13: breed figuur geplaatst boven kolommen

+\stopmessages

+

+\startmessages  english  library: columns

+  title: columns

+      1: only -- columns possible

+      2: use \string\filbreak\space as alternative

+      3: problems, disable balancing 

+      4: top float not yet supported 

+      5: bottom float not yet supported 

+      6: -- float(s) postponed

+      7: balancing aborted after 100 steps 

+      8: balanced in -- step(s)

+      9: check raggedness 

+     10: (less than) 1 line left 

+     11: float to wide for column 

+     12: float moved to next column 

+     13: wide float moved to top of columns

+\stopmessages

+

+\startmessages  german  library: columns

+  title: Spalten

+      1: nur -- Spalten moeglich

+      2: benutzte \string\filbreak\space als Alternative

+      3: Problem, verwende [ausgleich=nein]

+      4: Gleitobjekt oben ncoh nicht unterstuetzt

+      5: Gleitobjekt unten ncoh nicht unterstuetzt

+      6: -- Gleitobjekt(e) verschoben

+      7: ausgleich nach 100 Schritten abgebrocheb 

+      8: ausgeglichen nach  -- Schritt(en)

+      9: Ausrichtung ueberpruefen

+     10: (weniger als) 1 Zeile uebrig

+     11: Gleitobjekt zu breit fuer Spalte 

+     12: Gleitobjekt in naechste Zeile verschoben 

+     13: breites Gleitobjekt an den Anfang der Spalten verschoben

+\stopmessages

+

+%D This completely new implementation can handle enough

+%D situations for everyday documents, but is still far from

+%D perfect. While at the moment the routine doesn't support

+%D all kind of floats, it does support:

+%D

+%D \startopsomming

+%D \som  an unlimitted number of columns

+%D \som  ragged or not ragged bottoms

+%D \som  optional balancing without \type{\balancingerrors}

+%D \som  different \type{\baselineskips}, \type{\spacing},

+%D       \type{\topskip} and \type{\maxdepth}

+%D \som  left- and right indentation, e.g. within lists

+%D \som  moving columns floats to the next column or page

+%D \som  handling of floats that are to wide for a columns

+%D \stopopsomming

+%D

+%D One could wonder why single and multi||columns modes are

+%D still separated. One reason for this is that \TeX\ is not

+%D suited well for handling multi||columns. As a result, the

+%D single columns routines are more robust. Handling one

+%D column as a special case of multi||columns is posible but at

+%D the cost of worse float handling, worse page breaking,

+%D worse etc. Complicated multi||column page handling should

+%D be done in \kap{DTP}||systems anyway.

+%D

+%D There are three commands provided for entering and leaving

+%D multi||column mode and for going to the next column:

+%D

+%D \interface \type{\beginmulticolumns} \\ \\ 

+%D \interface \type{\endmulticolumns}   \\ \\ 

+%D \interface \type{\ejectcolumn}       \\ \\ 

+%D

+%D This routines are sort of stand||alone. They communicate

+%D with the rest of \CONTEXT\ by means of some interface

+%D macro's, which we only mention.

+%D

+%D \interface \type{\nofcolumns} \\ 

+%D   the number of columns \\

+%D \interface \type{\betweencolumns} \\ 

+%D   the stuff between columns \\

+%D \interface \type{\finaloutput{material}} \\

+%D   some kind of \type{\pagebody} and \type{\shipout} \\

+%D

+%D \interface \type{\ifbalancecolumns} \\ 

+%D   balancing the colums or not \\

+%D \interface \type{\ifstretchcolumns} \\ 

+%D   ragging the bottom or not \\

+%D

+%D \interface \type{\ifheightencolumns} \\ 

+%D     fix the heigh tor not \\

+%D \interface \type{\fixedcolumnheight} \\

+%D     the optional fixed height \\

+%D

+%D \interface \type{\ifinheritcolumns} \\ 

+%D     handle ragging or not \\

+%D \interface \type{\ifr@ggedbottom} \\

+%D     use ragged bottoms \\

+%D \interface \type{\ifb@selinebottom} \\

+%D     put the bottom line on the \\

+%D \interface \type{\ifnormalbottom} \\

+%D     put the bottom line at the \\

+%D

+%D \interface \type{\usercolumnwidth} \\

+%D     the calculated width of a column \\

+%D \interface \type{\columntextwidth} \\

+%D     the maximum width of a column \\

+%D \interface \type{\columntextheight} \\

+%D     the minimum width of a column \\

+%D

+%D \interface \type{\spacingfactor} \\

+%D     the spacing factor \\

+%D \interface \type{\corpssize} \\

+%D     the (local) corpssize \\

+%D \interface \type{\openlineheight} \\

+%D     the lineheight (including \type{\spacing}) \\

+%D

+%D \interface \type{\EveryCorps} \\

+%D     communication channel to font switching routines \\

+%D

+%D \interface \type{\global\settopskip} \\

+%D   set \type{\topskip} \\

+%D \interface \type{\setcolumnwarnings} \\

+%D   set \type{\badness} and \type{\fuzz} \\

+%D \interface \type{\setcolumninserts} \\

+%D   set \type{\insert}'s \\

+%D \interface \type{\setvsize} \\

+%D   set \type{\vsize} and \type{\pagegoal} \\

+%D \interface \type{\sethsize} \\

+%D   set \type{\hsize} \\

+%D

+%D \interface \type{\flushcolumnfloats} \\ 

+%D   push saved column floats (next page) \\

+%D \interface \type{\flushcolumnfloat} \\ 

+%D   push saved column floats (next column) \\

+%D \interface \type{\setcolumnfloats} \\ 

+%D   initialize column floats \\

+%D

+%D \interface \type{\finishcolumnbox} \\ 

+%D   do something special (a hook) \\

+%D \interface \type{\postprocesscolumnline} \\ 

+%D   do something with each columnline (also a hook) \\

+%D \interface \type{\currentcolumn} \\ 

+%D   the current column \\ 

+%D 

+%D These interface macro's are called upon or initialized

+%D by the multi||column macro's.

+

+\def\columntextwidth        {\zetbreedte}

+\def\columntextheight       {\teksthoogte}

+\def\usercolumnwidth        {\tekstbreedte}

+

+\def\fixedcolumnheight      {\teksthoogte}

+\def\betweencolumns         {\hskip\corpssize}

+

+\def\setcolumnwarnings      {\dontcomplaincolumnboxes}

+\def\setcolumninserts       {\dontpermitcolumninserts}

+

+\def\setcolumnfloats        {} % in CONTEXT used for floats

+\def\flushcolumnfloats      {} % in CONTEXT used for floats

+\def\flushcolumnfloat       {} % in CONTEXT used for floats

+

+\def\finishcolumnbox        {} % in CONTEXT used for backgrounds

+

+%D In fact, the column height and width are set by mens of 

+%D two macro's. One can change their meaning if needed: 

+

+\def\setcolumntextheight%

+   {\def\columntextheight{\teksthoogte}}

+

+\def\setcolumntextwidth%

+   {\def\columntextwidth{\tekstbreedte}}

+

+%D Both macros are redefined in \CONTEXT\ when backgrounds 

+%D are applied to columns. 

+

+\newcount\nofcolumns        \nofcolumns=2

+

+\def\maxnofcolumns          {16}

+\def\allocatednofcolumns    {0}

+

+\newif\ifbalancecolumns    \balancecolumnsfalse

+\newif\ifstretchcolumns    \stretchcolumnsfalse

+\newif\ifinheritcolumns    \inheritcolumnsfalse

+\newif\ifheightencolumns   \heightencolumnsfalse

+

+\newbox\partialpage

+\newskip\partialpageskip

+

+\newbox\restofpage

+\newbox\savedfloatlist

+

+\newdimen\intercolumnwidth

+\newdimen\localcolumnwidth

+\newdimen\partialpageheight

+

+\newtoks\singlecolumnout

+

+%D During initialization the temporary boxes are allocated.

+%D This enables us to use as much columns as we want, without

+%D exhausting the pool of boxes too fast. We could have packed

+%D them in one box, but we've got enough boxes.

+%D

+%D Two sets of boxes are declared, the txtboxes are used for

+%D the text, the topboxes are for moved column floats.

+

+\def\@@txtcol{@@txtcol}

+\def\@@topcol{@@topcol}

+

+\def\initializemulticolumns#1%

+  {\ifnum#1>\maxnofcolumns\relax

+     \showmessage{\m!columns}{1}{\maxnofcolumns}%

+     \nofcolumns=\maxnofcolumns

+   \else

+     \nofcolumns=#1\relax

+   \fi

+   \ifnum\nofcolumns>\allocatednofcolumns\relax

+     \dorecurse

+       {#1}

+       {\ifnum\recurselevel>\allocatednofcolumns\relax

+          \newbox\next

+          \global\letvalue{\@@txtcol\recurselevel}=\next

+          \newbox\next

+          \global\letvalue{\@@topcol\recurselevel}=\next

+        \fi}%

+     \xdef\allocatednofcolumns{\the\nofcolumns}%

+   \fi

+   \edef\firstcolumnbox{\getvalue{\@@txtcol1}}%

+   \edef\firsttopcolumnbox{\getvalue{\@@topcol1}}%

+   \edef\lastcolumnbox{\getvalue{\@@txtcol\the\nofcolumns}}%

+   \edef\lasttopcolumnbox{\getvalue{\@@topcol\the\nofcolumns}}}

+

+%D Without going in details we present two macro's which

+%D handle the columns. The action which is transfered by the

+%D the first and only parameter can do something with

+%D \type{\currentcolumnbox}. In case of the mid columns,

+%D \type{\firstcolumnbox} and \type{\lastcolumnbox} are handled

+%D outside these macro's.

+

+\def\dohandlemidcolumns#1%

+  {\dorecurse

+     {\nofcolumns}

+     {\ifnum\recurselevel>1

+        \ifnum\recurselevel<\nofcolumns\relax

+           \edef\currentcolumnbox{\getvalue{\@@txtcol\recurselevel}}%

+           \edef\currenttopcolumnbox{\getvalue{\@@topcol\recurselevel}}%

+           \let\currentcolumn=\recurselevel

+           #1\relax

+        \fi

+      \fi}}

+

+\def\dohandleallcolumns#1%

+  {\dorecurse

+     {\nofcolumns}

+     {\edef\currentcolumnbox{\getvalue{\@@txtcol\recurselevel}}%

+      \edef\currenttopcolumnbox{\getvalue{\@@topcol\recurselevel}}%

+      \let\currentcolumn=\recurselevel

+      #1\relax}}

+

+%D Going to a new columns is done by means of a

+%D \type{\ejectcolumn}. The following definition does not 

+%D always work.

+

+\def\ejectcolumn%

+  {\goodbreak

+   \showmessage{\m!columns}{2}{}}

+

+%D The next macro should never be called so let's deal with it.

+%D There were several solutions to these kind of errors. First

+%D we check for a good breakpoint before firing up the

+%D multi||column routine (\type{\break} or \type{\allowbreak}).

+%D We do the same at the end of the routine

+%D (\type{\allowbreak}). These allowances are definitely

+%D needed!

+%D

+%D Some on first sight redundant calls to for instance

+%D \type{\setvsize} in the flushing, splitting and balancing

+%D macro's can definitely not be omitted! Some are just there

+%D to handle situations that only few times arise. One of

+%D those can be that the output routine is invoked before

+%D everything is taken care of. This happens when we

+%D flush (part of) the current page with an \type{\unvbox}

+%D with a \type{\pagetotal}~$\approx$ \type{\pagegoal}. One

+%D simply cannot balance columns that are just balanced.

+%D

+%D I hope one never sees the following message. Because it

+%D took me a lot of time to develop the multi||columns

+%D routines, every (although seldom) warning gives me the

+%D creeps!

+

+\def\balancingerror%

+  {\showmessage{\m!columns}{3}{}%

+   \finaloutput{\unvbox255}}

+

+%D Here we present the two \type{\dont...} macro's, which are

+%D of course \CONTEXT||specific ones.

+

+\def\dontcomplaincolumnboxes%

+  {\mindermeldingen}

+

+\def\dontpermitcolumninserts%

+  {\def\dotopfloat%

+     {\showmessage{\m!columns}{4}{}%

+      \doexecfloat}%

+   \def\dobotfloat%

+     {\showmessage{\m!columns}{5}{}%

+      \doexecfloat}}

+

+\def\getinsertionheights\to#1\\% \relax'm 

+  {#1=\!!zeropoint

+   \def\doaddinsertionheight##1%

+     {\ifvoid##1\else

+        \advance#1 by \skip##1

+        \advance#1 by \ht##1

+       \fi}%

+   \doaddinsertionheight\topins

+   \doaddinsertionheight\botins

+   \doaddinsertionheight\footins}

+

+%D The local column width is available in the dimension

+%D register \type{\localcolumnwidth}, which is calculated as:

+

+\def\setcolumnhsize%

+  {\setbox0=\hbox{\parindent\!!zeropoint\betweencolumns}%

+   \intercolumnwidth=\wd0

+   \localcolumnwidth=\columntextwidth

+   \edef\globalcolumnwidth{\the\localcolumnwidth}%

+   \advance\localcolumnwidth by -\leftskip

+   \advance\localcolumnwidth by -\rightskip

+   \advance\localcolumnwidth by -\nofcolumns\intercolumnwidth

+   \advance\localcolumnwidth by \intercolumnwidth

+   \divide\localcolumnwidth  by \nofcolumns

+   \usercolumnwidth=\localcolumnwidth

+   \hsize=\localcolumnwidth} % we don't do it \global

+

+%D One should be aware that when font related dimensions are 

+%D used in typesetting the in||between material, these 

+%D dimensions are influenced by corps switches inside 

+%D multi||column mode. 

+

+%D The global width is saved in \type {\globalcolumnwidth}. 

+%D This value is used when we pack the columns in a \type 

+%D {\hbox}.

+

+\def\setcolumnvsize%

+  {\global\vsize=\columntextheight

+   \ifdim\partialpageheight>\!!zeropoint

+     \global\advance\vsize by -\partialpageheight  

+   \fi

+   \getinsertionheights\to\dimen0\\%

+   \global\advance\vsize by -\dimen0

+   \global\vsize=\nofcolumns\vsize

+   \global\pagegoal=\vsize} % let's do it only here

+

+%D It really starts here. After some checks and initializations

+%D we change the output routine to continous multi||column

+%D mode. This mode handles columns that fill the current and

+%D next full pages. The method used is (more or less)

+%D multiplying \type{\vsize} and dividing \type{\hsize} by

+%D \type{\nofcolumns}. More on this can be found in the

+%D \TeX book. We save the top of the current page in box

+%D \type{\partialpage}.

+%D

+%D We manipulate \type{\topskip} a bit, just to be shure that

+%D is has no flexibility. This has te be done every time a

+%D font switch takles place, because \type{\topskip} can depend

+%D on this.

+%D

+%D Watch the trick with the \type{\vbox}. This way we get the

+%D right interlining and white space.

+

+\def\beginmulticolumns%

+  {\par

+   \begingroup

+   \dontshowcomposition

+   \setcolumntextwidth\relax

+   \setcolumntextheight\relax

+   \ifsomefloatwaiting

+     \showmessage{\m!columns}{6}{\the\savednoffloats}%

+     \global\setbox\savedfloatlist=\box\floatlist

+     \edef\restoresavedfloats%

+       {\global\savednoffloats=\the\savednoffloats

+        \global\setbox\floatlist=\box\savedfloatlist

+        \global\noexpand\somefloatwaitingtrue}%

+     \global\savednoffloats=0

+     \global\somefloatwaitingfalse

+   \else

+     \let\restoresavedfloats=\relax

+   \fi

+   %\global\partialpageskip=\lastskip         % vervallen

+   \dimen0=\pagetotal

+   \advance\dimen0 by \parskip

+   \advance\dimen0 by \openlineheight

+   \ifdim\dimen0<\pagegoal

+     \allowbreak

+   \else

+     \break

+   \fi

+   \EveryCorps{\topskip=1\topskip}%           % nog nodig ?

+   \the\everycorps                            % nog nodig ?

+   \initializemulticolumns\nofcolumns

+   \setcolumninserts

+   \hangafter=0\relax

+   \hangindent=\!!zeropoint\relax

+   \everypar{}% \everypar={\flushcolumnfloat}%

+   \ifdim\pagetotal=\!!zeropoint\relax        % later toegevoegd

+   \else                                      % later toegevoegd

+      \vbox{\strut}%                          % toegevoegd

+      \vskip-\lineskip                        % toegevoegd

+      \vskip-\openlineheight                  % toegevoegd

+   \fi                                        % later toegevoegd

+   %\global\partialpageheight=\pagetotal      % vervangen door \ht\partialpage

+   \global\singlecolumnout=\output

+   \global\output={\global\setbox\partialpage=\vbox{\unvbox255}}%

+   \eject

+   \global\partialpageheight=\ht\partialpage 

+   \global\output={\continuousmulticolumnsout}%

+   \setcolumnfloats

+   \dohandleallcolumns

+     {\global\setbox\currenttopcolumnbox=\box\voidb@x}%

+   \let\sethsize=\setcolumnhsize

+   \let\setvsize=\setcolumnvsize

+   \sethsize

+   \setvsize

+   \showcomposition}

+

+%D When we leave the multi||column mode, we have to process the

+%D not yet shipped out part of the columns. When we don't

+%D balance, we simply force a continuous output, but a balanced

+%D output is more tricky.

+%D

+%D First we try to fill up the page and when all or something

+%D is left we try to balance things. This is another useful

+%D adaption of the ancesters of these macro's. It takes some

+%D reasoning to find out what happens and maybe I'm making

+%D some mistake, but it works.

+%D

+%D Unvoiding box \type{\partialpage} is sometimes necessary,

+%D e.g. when there is no text given between \type{\begin..}

+%D and \type{\end..}. The \type{\par} is needed!

+

+\def\endmulticolumns%

+  {\dontshowcomposition

+   \doflushcolumnfloats % added recently 

+   \par

+   \ifbalancecolumns

+     \global\output={\continuousmulticolumnsout}%

+     \goodbreak

+     \global\output={\balancedmulticolumnsout}%

+   \else

+     \goodbreak

+   \fi

+   \eject                 % the prevdepth is important, try e.g. toclist in 

+   \prevdepth\!!zeropoint % columns before some noncolumned text text 

+   \global\output=\singlecolumnout

+   \ifvoid\partialpage\else

+     \unvbox\partialpage

+   \fi

+   \global\partialpageheight=\!!zeropoint

+   \nofcolumns=1

+   \setvsize

+   \dosomebreak\allowbreak

+   \restoresavedfloats  

+   \endgroup}

+

+%D Because some initializations happen three times, we

+%D defined a macro for them. The \type{\everypar{}} is

+%D needed because we don't want anything to interfere.

+

+\def\setmulticolumnsout%

+  {\everypar{}%

+   \setcolumnwarnings

+   \settopskip

+   \setmaxdepth

+   \topskip=1\topskip

+   \splittopskip=\topskip

+   \splitmaxdepth=\maxdepth

+   \boxmaxdepth=\maxdepth

+   \emergencystretch=\!!zeropoint\relax} % sometimes needed !

+

+%D Flushing the page comes to pasting the columns together and

+%D appending the result to box \type{\partialpage}, if not

+%D void. I've seen a lot of implementations in which some skip

+%D was put between normal text and multi||column text. When we

+%D don't want this, the baselines can be messed up. I hope the

+%D seemingly complicated calculation of a correction

+%D \type{\kern} is adequate to overcome this. Although not

+%D watertight, spacing is taken into account and even multiple

+%D mode changes on one page go well. But cross your fingers and

+%D don't blame me.

+%D

+%D One of the complications of flushing out the boxes is that

+%D \type{\partialpage} needs to be \type{\unvbox}'ed, otherwise

+%D there is too less flexibility in the page when using

+%D \type{\r@ggedbottom}. It took a lot of time before these

+%D kind of problems were overcome. Using \type{\unvbox} at the

+%D wrong moment can generate \type{\balancingerror}'s.

+%D

+%D One can use the macros \type {\maxcolumnheight} and \type 

+%D {\maxcolumndepth} when generating material between columns 

+%D as well as postprocessing column lines.

+

+\let\maxcolumnheight=\!!zeropoint

+\let\maxcolumndepth =\!!zeropoint

+

+\def\setmaxcolumndimensions%

+  {\let\maxcolumnheight=\!!zeropoint 

+   \let\maxcolumndepth =\!!zeropoint

+   \dohandleallcolumns 

+     {\ifdim\ht\currentcolumnbox>\maxcolumnheight 

+        \edef\maxcolumnheight{\the\ht\currentcolumnbox}%

+      \fi

+      \ifdim\dp\currentcolumnbox>\maxcolumndepth

+        \edef\maxcolumndepth{\the\dp\currentcolumnbox}%

+      \fi}}

+

+\def\flushcolumnedpage%

+  {\bgroup

+   \setmulticolumnsout

+   \showcomposition

+   \setmaxcolumndimensions

+   \postprocesscolumns

+   \dohandleallcolumns % \hbox i.v.m. \showcomposition

+     {\global\setbox\currentcolumnbox=\hbox to \localcolumnwidth

+        {\box\currentcolumnbox

+         \global\wd\currentcolumnbox=\localcolumnwidth

+         \ifheightencolumns

+           \global\ht\currentcolumnbox=\fixedcolumnheight

+         \fi}}%

+   \setmaxcolumndimensions

+   \setbox0=\vbox

+     {\hbox to \globalcolumnwidth 

+        {\dohandleallcolumns

+           {\finishcolumnbox{\box\currentcolumnbox}% 

+            \ifnum\currentcolumn<\nofcolumns

+              \hfil\betweencolumns\hfil 

+            \fi}}}%

+   \dohandleallcolumns

+     {\global\setbox\currenttopcolumnbox=\box\voidb@x}%

+   \ifvoid\partialpage

+   \else

+     \unvbox\partialpage

+   \fi

+   \global\partialpageheight=\!!zeropoint

+   \setvsize

+   \dosomebreak\nobreak

+   \dp0=\!!zeropoint

+   \box0

+   \allowbreak % nieuw / test 

+   \egroup}

+

+%D In case one didn't notice, finaly \type{\finishcolumnbox} is 

+%D applied to all boxes. One can use this hook for special 

+%D purposes. But there is more: 

+%D 

+%D Once upon a time I wanted to manipulate the individual lines 

+%D in a column. This feature is demonstrated in the two examples 

+%D below. 

+%D 

+%D \startbuffer

+%D \def\postprocesscolumnline#1%

+%D   {\ruledhbox{#1}\hss}

+%D 

+%D \startkolommen[n=4]

+%D \dorecurse{25}{line: \recurselevel\par}

+%D \stopkolommen

+%D \stopbuffer 

+%D 

+%D \typebuffer 

+%D 

+%D Here we show the natural width of the lines:

+%D 

+%D {\haalbuffer}

+%D 

+%D The next example does a bit more advanced manipulation: 

+%D 

+%D \startbuffer

+%D \def\postprocesscolumnline#1%

+%D   {\ifodd\currentcolumn

+%D      \hfill#1\relax

+%D    \else

+%D      \relax#1\hfill

+%D    \fi}

+%D 

+%D \startkolommen[n=4]

+%D \dorecurse{25}{line \recurselevel\par}

+%D \stopkolommen

+%D \stopbuffer 

+%D 

+%D \typebuffer

+%D 

+%D Here we also see an application of \type{\currentcolumn}: 

+%D 

+%D {\haalbuffer}

+%D 

+%D This feature is implemented using the reshape macros 

+%D presented in \type{supp-box}. 

+

+\def\postprocesscolumns% recent extension

+  {\ifx\postprocesscolumnline\undefined \else 

+     \dohandleallcolumns

+       {\global\setbox\currentcolumnbox=\vtop

+          {\beginofshapebox

+           \unvbox\currentcolumnbox

+           \unskip\unskip

+           \endofshapebox

+           \reshapebox

+             {\dimen0=\ht\shapebox

+              \dimen2=\dp\shapebox

+              \setbox\shapebox=\hbox to \hsize

+                {\postprocesscolumnline{\unhbox\shapebox}}%

+              \ht\shapebox=\dimen0

+              \dp\shapebox=\dimen2

+              \box\shapebox}%

+           \flushshapebox

+           \everypar{}\parskip\!!zeropoint % = \forgetall

+           \strut\endgraf

+           \vskip-\lineheight

+           \vfil}}%

+   \fi}

+

+%D We default to doing nothing!

+

+\let\postprocesscolumnline=\undefined 

+

+%D Here comes the simple splitting routine. It's a bit

+%D longer than expected because of ragging bottoms or not.

+%D This part can be a bit shorter but I suppose that I will

+%D forget what happens. The splitting takes some already

+%D present material (think of floats) into account!

+%D

+%D First we present some auxiliary routines. Any material,

+%D like for instance floats, that is already present in the

+%D boxes is preserved.

+

+\def\splitcolumn#1from \box#2to \dimen#3 top \box#4%

+  {\bgroup

+   \ifdim\ht#4>\!!zeropoint

+     \dimen0=\dimen#3\relax

+     \dimen2=\dimen#3\relax

+     \advance\dimen0 by -\ht#4

+     \setbox0=\vsplit#2 to \dimen0

+     \global\setbox#1=\vbox to \dimen2{\unvcopy#4\unvbox0}%

+   \else

+     \global\setbox#1=\vsplit#2 to \dimen#3

+   \fi

+   \egroup}

+

+\def\splitcurrentcolumn from \box#1to \dimen#2%

+  {\splitcolumn\currentcolumnbox from \box#1 to \dimen#2 top \box\currenttopcolumnbox}

+

+\def\splitfirstcolumn from \box#1to \dimen#2%

+  {\splitcolumn\firstcolumnbox from \box#1 to \dimen#2 top \box\firsttopcolumnbox}

+

+\def\splitlastcolumn from \box#1to \dimen#2%

+  {\global\setbox\lastcolumnbox=\vbox

+     {\unvcopy\lasttopcolumnbox

+      \unvbox#1}}

+

+%D Here comes the routine that splits the long box in columns.

+%D The macro \type{\flushcolumnfloats} can be used to flush

+%D either floats that were present before the multi||column

+%D mode was entered, or floats that migrate to next columns.

+%D Flushing floats is a delicate process.

+

+\def\continuousmulticolumnsout%

+  {\bgroup

+   \setmulticolumnsout

+   \dontshowcomposition

+   \dimen0=\columntextheight

+   %\advance\dimen0 by -\maxdepth % wel of niet (niet dus)

+   \advance\dimen0 by -\partialpageheight

+   \getinsertionheights\to\dimen2\\% toegevoegd ivm voetnoten 

+   \advance\dimen0 by -\dimen2     % idem 

+   \dohandleallcolumns

+     {\splitcurrentcolumn from \box255 to \dimen0}%

+   \setbox\restofpage=\vbox{\unvbox255}%

+   \ifinheritcolumns

+     \ifr@ggedbottom

+       \dohandleallcolumns

+         {\global\setbox\currentcolumnbox=\vbox to \dimen0

+            {\unvbox\currentcolumnbox

+             \vfill}}%

+     \fi

+     \ifn@rmalbottom

+       \advance\dimen0 by \maxdepth

+       \dohandleallcolumns

+         {\global\setbox\currentcolumnbox=\vbox to \dimen0

+            {\unvbox\currentcolumnbox}}%

+     \fi

+     \ifb@selinebottom

+       % the columns are on top of the baseline

+     \fi

+   \else

+     \dohandleallcolumns

+       {\global\setbox\currentcolumnbox=\vbox to \dimen0

+          {\ifstretchcolumns

+             \unvbox\currentcolumnbox

+           \else

+             \unvbox\currentcolumnbox % wel of niet \unvbox ?

+             \vfill

+           \fi}}%

+     \dohandleallcolumns

+       {\global\ht\currentcolumnbox=\dimen0}%

+   \fi

+   \finaloutput{\flushcolumnedpage}%

+   \sethsize

+   \setvsize

+   \flushcolumnfloats

+   \unvbox\restofpage

+   % \penalty\outputpenalty % gaat gruwelijk mis in opsommingen

+   \egroup}

+

+%D And this is the balancing stuff. Again, part of the routine

+%D is dedicated to handling ragged bottoms, but here we also

+%D see some handling concerning the stretching of columns.

+%D We set \type{\widowpenalty} at~0, which enables us to

+%D balance columns with few lines. The use of \type{\box2} and

+%D \type{\box4} garantees a more robust check when skips are

+%D used.

+

+\def\balancedmulticolumnsout%

+  {\bgroup

+   \setmulticolumnsout

+   \dontshowcomposition

+   \widowpenalty=0

+   \setbox0=\vbox{\unvbox255}%

+   \ifdim\ht0>\openlineheight

+     \dimen0=\ht0

+     \advance\dimen0 by \topskip

+     \advance\dimen0 by -\baselineskip

+     \divide\dimen0 by \nofcolumns

+     \vbadness=\!!tenthousand\relax

+     \count255=0

+     \bgroup

+     \dimen2=\!!onepoint

+     \dimen2=\spacingfactor\dimen2

+     \loop

+       \advance\count255 by 1

+       \global\setbox\restofpage=\copy0\relax

+       \splitfirstcolumn from \box\restofpage to \dimen0

+       \dohandlemidcolumns

+         {\splitcurrentcolumn from \box\restofpage to \dimen0}%

+       \splitlastcolumn from \box\restofpage to \dimen0

+       \setbox2=\vbox{\unvcopy\firstcolumnbox}%

+       \dimen4=\!!zeropoint

+       \dohandleallcolumns

+         {\setbox4=\vbox{\unvcopy\currentcolumnbox}%

+          \dimen6=\ht4

+          \ifdim\dimen6>\dimen4 \dimen4=\dimen6\fi}%

+       \donefalse

+       \ifnum\count255>100\relax

+         \donefalse

+       \fi

+       \ifdim\dimen4>\ht2

+         \donetrue

+       \fi

+       \ifdone

+         \advance\dimen0 by \dimen2\relax

+     \repeat

+     \dohandleallcolumns

+       {\global\setbox\currentcolumnbox=\vbox{\unvcopy\currentcolumnbox}}% NIEUW

+     \ifnum\count255>100\relax

+       \showmessage{\m!columns}{7}{}%

+     \else

+       \showmessage{\m!columns}{8}{\the\count255\space}%

+     \fi

+     \egroup

+     \ifinheritcolumns

+       \dimen0=\ht\firstcolumnbox

+       \dimen2=\ht\firstcolumnbox

+       \advance\dimen2 by -\openlineheight

+       \dohandleallcolumns

+         {\dimen4=\ht\currentcolumnbox

+          \dimen6=10\openlineheight

+          \global\setbox\currentcolumnbox=\vbox to \dimen0

+            {\unvbox\currentcolumnbox

+             \ifdim\dimen4>\dimen6

+               \ifdim\dimen4<\dimen0

+                 \ifdim\dimen4>\dimen2

+                   \vskip\!!zeropoint  % !!

+                 \else

+                   \vskip\openlineheight

+                   \vfill

+                 \fi

+               \else

+                 \vskip\!!zeropoint

+               \fi

+             \else

+               \vskip\openlineheight

+               \vfill

+             \fi}}%

+     \else

+       \bgroup

+       \ifstretchcolumns

+         \dimen0=\ht\firstcolumnbox

+         \dimen2=\bottomtolerance\ht\firstcolumnbox

+         \setbox0=\vbox{\unvcopy\lastcolumnbox}%

+         \advance\dimen0 by -\ht0\relax

+         \advance\dimen0 by -\dp0\relax

+         \ifdim\dimen0>\openlineheight\relax

+           \ifdim\dimen0>\dimen2\relax

+             % \stretchcolumnsfalse % beter goed slecht dan slecht goed

+             \showmessage{\m!columns}{9}{}%

+           \fi

+         \fi

+       \fi

+       \dohandleallcolumns

+         {\global\setbox\currentcolumnbox=\vbox to \ht\firstcolumnbox

+            {\ifstretchcolumns

+               \unvbox\currentcolumnbox

+             \else

+               \box\currentcolumnbox

+               \vfill

+             \fi}}%

+       \egroup

+     \fi

+   \else

+     \showmessage{\m!columns}{10}{}%

+     \global\setbox\firstcolumnbox=\vbox{\unvbox0}%

+   \fi

+   \global\output={\balancingerror}%

+   \b@selinebottomtrue % forces depth in separation rule 

+   \flushcolumnedpage

+   \egroup}

+

+%D The multicolumn mechanism is incorporated in a \CONTEXT\

+%D interface, which acts like:

+%D

+%D \starttypen

+%D \startcolumns[n=4,balance=no,stretch=no,line=on]

+%D   some text

+%D \stopcolumns

+%D \stoptypen

+%D

+%D The setup is optional. The default behaviour of columns

+%D can be set up with:

+%D

+%D \starttypen

+%D \setupcolumns

+%D   [n=2,

+%D    balance=yes,

+%D    stretch=text,

+%D    line=off]

+%D \stoptypen

+%D

+%D In this case, stretching is according to the way it's

+%D done outside columns (\type{\inheritcolumnstrue}). Also

+%D we can setup the \type{tolerance} within a column, the

+%D \type{distance} between columns and the fixed

+%D \type{height} of a column.

+

+%D Multi||column output: the float routines

+%D

+%D Here come the routines that handle the placement of column

+%D floats. Floats that are to big migrate to the next

+%D column. Floats that are too wide, migrate to the top of the

+%D next page, where they span as much columns as needed.

+%D Floats that are left over from outside the multi||column

+%D mode are flushed first. In macro \type{\finaloutput} the

+%D topfloats that are left from previous text should be set.

+%D

+%D When there are some floats in the queue, we inhibit the

+%D flushing of floats on top of columns. The number of

+%D waiting floats is preswent in \type{\savednoftopfloats} and

+%D is saved. As long as there are floats waiting, the topfloats

+%D are places as if we are outside multi||column mode. This is

+%D neccessary for e.g. multicolumn lists.

+%D

+%D When all those floats are flushed, we switch to the local

+%D flushing routine.

+

+\def\setcolumnfloats%

+  {\xdef\globalsavednoffloats{\the\savednoffloats}%

+   \ifnum\globalsavednoffloats>0

+     \setglobalcolumnfloats

+   \else

+     \setlocalcolumnfloats

+   \fi}

+

+\def\setglobalcolumnfloats%

+  {\everypar={}%

+   \let\flushcolumnfloat=\relax

+   \let\doroomfloat=\relax

+   \let\flushcolumnfloats=\noflushcolumnfloats}

+

+\def\setlocalcolumnfloats%

+  {\everypar={\flushcolumnfloat\checkindentation}% nog documenteren 

+   \let\flushcolumnfloat=\doflushcolumnfloat

+   \let\doroomfloat=\docolumnroomfloat

+   \let\flushcolumnfloats=\doflushcolumnfloats

+   \let\dosetbothinserts=\relax

+   \let\dotopinsertions=\relax}

+

+\def\noflushcolumnfloats%

+  {\bgroup

+   \xdef\localsavednoffloats{\the\savednoffloats}%

+   \global\savednoffloats=\globalsavednoffloats

+   \dotopinsertions

+   \xdef\globalsavenoffloats{\the\savednoffloats}%

+   \ifnum\globalsavednoffloats=0

+     \setlocalcolumnfloats

+   \fi

+   \global\savednoffloats=\localsavednoffloats

+   \egroup}

+

+%D We need to calculate the amount of free space in a columns.

+%D When there is not enough room, we migrate the float to the

+%D next column. These macro's are alternatives (and

+%D look||alikes) of \type{\doroomfloat}. When a float is to

+%D wide, for one column, it is moved to the top of the next

+%D page. Of course such moved floats have to be taken into

+%D account when we calculate the available space. It's a pitty

+%D that such things are no integral part of \TEX.

+

+% \def\getcolumnstatus\column#1\total#2\goal#3\\%

+%   {\ifdim\pagegoal<\maxdimen

+%      \dimen0=\pagegoal

+%      \divide\dimen0 by \nofcolumns

+%      \dimen2=\!!zeropoint

+%      \count255=0\relax

+%      \dimen8=\columntextheight

+%      \advance\dimen8 by -\partialpageheight

+%      %\advance\dimen8 by -\maxdepth % recently deleted 

+%      \def\dogetcolumnstatus%

+%        {\advance\count255 by 1\relax

+%         \advance\dimen2 by \ht\currenttopcolumnbox

+%         \advance\dimen2 by \dp\currenttopcolumnbox

+%         \dimen4=\dimen2\relax

+%         \advance\dimen4 by \pagetotal

+%         \dimen6=\count255\dimen8

+%         \ifdim\dimen4>\dimen6

+%         \else

+%           \let\dogetcolumnstatus=\relax

+%         \fi}%

+%      \dohandleallcolumns{\dogetcolumnstatus}%

+%      \ifdim\dimen4=\dimen6

+%        \dimen4=\!!zeropoint

+%        \advance\count255 by 1

+%      \fi

+%      #1=\count255

+%      #2=\dimen4

+%      #3=\dimen6

+%    \else

+%      #1=1

+%      #2=\!!zeropoint

+%      #3=\teksthoogte

+%      \advance#3 by -\partialpageheight

+%    \fi}

+

+\def\getcolumnstatus\column#1\total#2\goal#3\\%

+  {\ifdim\pagegoal<\maxdimen

+     \dimen0=\pagegoal

+     \dimen10=\pagetotal

+   \else

+     \dimen0=\nofcolumns\teksthoogte

+     \dimen10=\!!zeropoint

+   \fi

+   \divide\dimen0 by \nofcolumns

+   \dimen2=\!!zeropoint

+   \count255=0

+   \dimen8=\columntextheight

+   \advance\dimen8 by -\partialpageheight

+   %\advance\dimen8 by -\maxdepth % recently deleted 

+   \def\dogetcolumnstatus%

+     {\advance\count255 by 1

+      \advance\dimen2 by \ht\currenttopcolumnbox

+      \advance\dimen2 by \dp\currenttopcolumnbox

+      \dimen4=\dimen2

+      \advance\dimen4 by \dimen10 % pagetotal

+      \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\docolumnroomfloat%

+  {\ifnofloatpermitted

+     \global\roomforfloatfalse

+   \else

+     \getcolumnstatus\column\count255\total\dimen0\goal\dimen2\\%

+     \advance\dimen0 by \ht\floatbox

+     \advance\dimen0 by \dp\floatbox

+     \advance\dimen0 by \floattopskip

+     % \advance\dimen0 by -\pageshrink nog eens testen

+     \ifdim\dimen0>\dimen2

+       \global\roomforfloatfalse

+     \else

+       \global\roomforfloattrue

+     \fi

+     \ifdim\wd\floatbox>\hsize

+       \showmessage{\m!columns}{11}{}%

+       \global\roomforfloatfalse

+     \fi

+   \fi}

+

+%D Flushing one float is done as soon as possible, i.e.

+%D \type{\everypar}. This means that (at the moment)

+%D sidefloats are not supported (overulled)!

+

+\def\doflushcolumnfloat%

+  {\bgroup

+   \ifsomefloatwaiting

+     \let\doflushcolumnfloat=\relax

+     \getcolumnstatus\column\count255\total\dimen0\goal\dimen2\\%

+     \ifdim\dimen0>\!!zeropoint

+       \dogetfloat

+       \ifdim\wd\floatbox>\hsize

+         \doresavefloat

+       \else

+         \setbox2=\vbox

+           {\blanko[\@@bkvoorwit]

+            \copy\floatbox

+            \blanko[\@@bknawit]}%

+         \advance\dimen0 by \ht2

+         \advance\dimen0 by 2\openlineheight % still neccessary ?

+         \ifdim\dimen0>\dimen2

+           \showmessage{\m!columns}{12}{}%

+           \doresavefloat

+         \else

+           \ifhmode{\setbox0=\lastbox}\fi% waar is die er in geslopen

+           \par

+           \ifdim\prevdepth<\!!zeropoint\relax % anders bovenaan kolom witruimte 

+           \else

+             \blanko[\@@bkvoorwit]

+           \fi

+           \copy\floatbox

+           \blanko[\@@bknawit]

+         \fi

+       \fi

+     \fi

+   \fi

+   \egroup}

+

+%D This one looks complicated. Upto \type{\nofcolumns} floats

+%D are placed, taking the width of a float into account. This

+%D routine can be improved on different ways:

+%D

+%D \startopsomming[intro,opelkaar]

+%D \som taking into account some imaginary baseline, just to

+%D      get the captions in line

+%D \som multipass flushing until as many floats are displaced

+%D      as possible

+%D \stopopsomming

+%D

+%D When handling lots of (small) floats spacing can get worse

+%D because of lining out the columns.

+

+\def\doflushcolumnfloats%

+  {\bgroup

+   \ifnum\savednoffloats>1\relax % no \ifsomefloatwaiting

+     \dimen8=\!!zeropoint

+     \dimen4=\!!zeropoint

+     \count0=0            % count0 can be used local

+     \count2=\nofcolumns  % count2 can be used local

+     \dohandleallcolumns

+       {\ifnum\count0>0\relax % the wide one's reserved space 

+          \global\setbox\currenttopcolumnbox=

+            \vbox{\vphantom{\copy\floatbox}\witruimte\blanko[\@@bknawit]}%

+        \else

+          \dogetfloat

+          \ifdim\wd\floatbox>\hsize

+            \dimen0=\wd\floatbox

+            \advance\dimen0 by \intercolumnwidth

+            \dimen2=\hsize

+            \advance\dimen2 by \intercolumnwidth

+            \divide\dimen0 by \dimen2

+            \count0=\dimen0

+            \advance\count0 by 1

+            \ifnum\count0>\count2

+              \doresavefloat

+            \else

+              \dimen0=\count0\hsize

+              \advance\dimen0 by \count0\intercolumnwidth

+              \advance\dimen0 by -\intercolumnwidth

+              \wd\floatbox=.5\wd\floatbox

+              \setbox\floatbox=\hbox to \dimen0{\hss\box\floatbox\hss}%

+            \fi

+            \showmessage{\m!columns}{13}{}%

+          \else

+            \showmessage{\m!columns}{13}{}%

+          \fi

+          \ifdim\ht\floatbox>\!!zeropoint\relax

+            \global\setbox\currenttopcolumnbox=

+              \vbox

+                {\copy\floatbox

+                 \witruimte % nodig ? 

+                 \blanko[\@@bknawit]}%

+          \fi

+          \dimen6=\ht\currenttopcolumnbox

+          \advance\dimen6 by \dp\currenttopcolumnbox

+        \fi

+        \ifdim\dimen4<\ht\currenttopcolumnbox

+          \dimen4=\ht\currenttopcolumnbox

+        \fi

+        \advance\dimen8 by \dimen6

+        \advance\count2 by -1

+        \advance\count0 by -1\relax}%

+     \setvsize

+     \global\advance\vsize by -\dimen8

+     \global\pagegoal=\vsize

+   \else

+     \doflushfloats

+   \fi

+   \egroup}

+

+%D This were the multi||column routines. They can and need to

+%D be improved but at the moment their behaviour is acceptable.

+%D

+%D One inprovement can be to normalize the height of floats

+%D to $n\times \type{\lineheight}$ with a macro like:

+%D

+%D \starttypen

+%D \normalizevbox{...}

+%D \stoptypen

+

+\protect

+

+\endinput

+
\ No newline at end of file