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%D \module
%D [ file=page-col, % moved from page-ini
%D version=2011.12.07, % 2000.10.20,
%D title=\CONTEXT\ Page Macros,
%D subtitle=Column Helpers,
%D author=Hans Hagen,
%D date=\currentdate,
%D copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.
\writestatus{loading}{ConTeXt Page Macros / Column Helpers}
%D Here we implement a coouple of helpers for dealing with
%D columns. For the moment we keep the names.
\unprotect
%D The next two registers can be used to store pre column
%D material as well as footnotes or so.
\newbox\precolumnbox \newdimen\precolumnboxheight
\newbox\postcolumnbox \newdimen\postcolumnboxheight
%D We reserve a counter for the number of columns as well as
%D the current column. Both are not to be changed by users!
\newcount\nofcolumns \nofcolumns = 1
\newcount\mofcolumns \mofcolumns = 1
\setnewconstant\maxnofcolumns 50
\setnewconstant\allocatednofcolumns 0
%D The next dimensions reports the final column height
\newdimen\finalcolumnheights
\newcount\finalcolumnlines
%D This register can be used as a temporary storage for page
%D content.
\newbox\restofpage
%D A few more (some might go away):
\newif\ifintermediatefootnotes
\newif\ifcarryoverfootnotes %\carryoverfootnotestrue
\newif\iflastcolumnfootnotes %\lastcolumnfootnotestrue
\newif\ifbalancecolumns %\balancecolumnstrue
\newif\ifbalancetoheight %\balancetoheighttrue
\newif\ifforcecolumngrid \forcecolumngridtrue
\newif\ifstretchcolumns \stretchcolumnsfalse
\newif\ifinheritcolumns \inheritcolumnsfalse
\newif\ifheightencolumns \heightencolumnsfalse
\newif\ifbalancingcolumns
\newif\ifcollectingcontent
\newif\ifcolumnoverflow
\newdimen\intercolumnwidth
\newdimen\localcolumnwidth
\newdimen\savedpagetotal
\newconstant\columndirection % 0:lr 1:rl
\def\minbalancetoplines {1}
\def\minfreecolumnlines {2}
\newif\ifrecentercolumnbox \recentercolumnboxtrue
\newif\ifrerecentercolumnbox \rerecentercolumnboxtrue
\newif\ifpackcolumnfloats \packcolumnfloatstrue
%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\initializecolumns#1%
{\ifnum#1>\maxnofcolumns
\showmessage\m!columns1\maxnofcolumns
\nofcolumns\maxnofcolumns
\else
\nofcolumns#1\relax
\fi
\ifnum\nofcolumns>\allocatednofcolumns
\dorecurse\nofcolumns
{\ifnum\recurselevel>\allocatednofcolumns\relax
% \newbox\next \letgvalue{\??zc-\recurselevel-t}=\next
\expandafter\newbox\csname\??zc-\recurselevel-t\endcsname % text
\expandafter\newbox\csname\??zc-\recurselevel-f\endcsname % foot
\expandafter\newbox\csname\??zc-\recurselevel-h\endcsname % top insert
\expandafter\newbox\csname\??zc-\recurselevel-l\endcsname % top insert
\fi}%
\global\allocatednofcolumns\nofcolumns
\fi}
\def\firstcolumnbox {\columntextbox\plusone}
\def\currentcolumnbox {\columntextbox\mofcolumns}
\def\lastcolumnbox {\columntextbox\nofcolumns}
\def\firsttopcolumnbox {\columntopbox \plusone}
\def\currenttopcolumnbox {\columntopbox \mofcolumns}
\def\lasttopcolumnbox {\columntopbox \nofcolumns}
\def\columntextbox #1{\csname\??zc-\number#1-t\endcsname}
\def\columnfootbox #1{\csname\??zc-\number#1-f\endcsname}
\def\columntopbox #1{\csname\??zc-\number#1-h\endcsname}
\def\columnbotbox #1{\csname\??zc-\number#1-l\endcsname}
\def\columnsettextbox {\global\setbox\columntextbox}
\def\columnsetfootbox {\global\setbox\columnfootbox}
\def\columnsettopbox {\global\setbox\columntopbox}
\def\columnsetbotbox {\global\setbox\columnbotbox}
\def\columngettextbox {\copy\columntextbox}
\def\columngetfootbox {\copy\columnfootbox}
\def\columngettopbox {\copy\columntopbox}
\def\columngetbotbox {\copy\columnbotbox}
\def\columnerasetextboxes{\dorecurse\allocatednofcolumns{\columnsettextbox\recurselevel\emptybox}}
\def\columnerasefootboxes{\dorecurse\allocatednofcolumns{\columnsetfootbox\recurselevel\emptybox}}
\def\columnerasetopboxes {\dorecurse\allocatednofcolumns{\columnsettopbox \recurselevel\emptybox}}
\def\columnerasebotboxes {\dorecurse\allocatednofcolumns{\columnsetbotbox \recurselevel\emptybox}}
%D Without going in details we present two macro's which handle
%D the columns. The action which is transfered by the the first
%D and only parameter can do something with \type
%D {\currentcolumnbox}. In case of the mid columns, \type
%D {\firstcolumnbox} and \type {\lastcolumnbox} are handled
%D outside these macro's.
\def\dohandlecolumn#1%
{\mofcolumns\recurselevel
\let\currentcolumn\recurselevel
#1\relax}
\def\dohandleallcolumns#1%
{\dorecurse\nofcolumns{\dohandlecolumn{#1}}}
\def\dohandlerevcolumns#1%
{\dostepwiserecurse\nofcolumns\plusone\minusone{\dohandlecolumn{#1}}}
\def\dohandlemidcolumns#1%
{\dohandleallcolumns
{\ifnum\recurselevel>\plusone
\ifnum\recurselevel<\nofcolumns
\dohandlecolumn{#1}%
\fi
\fi}}
\protect \endinput
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