%D \module
%D   [       file=anch-bar,
%D        version=2003.03.16,
%D          title=\CONTEXT\ Anchoring Macros,
%D       subtitle=Margin Bars and alike,
%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 Anchoring Macros / Margin Bars}

\unprotect

%D We will implement a sidebar mechanism using the
%D functionality from \type {core-pos}.
%D
%D \starttyping
%D \definesidebar[whow][rulecolor=green,distance=]
%D
%D \input tufte \par
%D \startsidebar
%D   \input tufte \par
%D   \input tufte \par
%D   \startsidebar[whow]
%D     \input tufte \par
%D     \input tufte \par
%D     \input tufte
%D   \stopsidebar \par
%D   \input tufte \par
%D   \input tufte
%D \stopsidebar \par
%D \input tufte \par
%D \input tufte \par
%D \startsidebar
%D   \input tufte \par
%D   \input tufte \par
%D   \input tufte \par
%D   \input tufte \par
%D   \input tufte
%D \stopsidebar \par
%D \input tufte \par
%D \input tufte \par
%D \startsidebar
%D   \input tufte
%D   \input tufte
%D   \input tufte
%D   \input tufte
%D   \input tufte
%D \stopsidebar
%D \stoptyping

\installcorenamespace{sidebar}

\installcommandhandler \??sidebar {sidebar} \??sidebar

\newcount\c_anch_sidebars_n
\newdimen\c_anch_sidebars_distance

% \setupMPvariables
%   [mpos:sidebar]
%   [linecolor=red,
%    linewidth=2pt,
%    distance=5pt]

\setupsidebar
  [\c!rulethickness=2pt,
   \c!rulecolor=\s!black,
   \c!alternative=0,
   \c!topoffset=0pt,
   \c!bottomoffset=0pt,
   \c!distance=.5\bodyfontsize]

\let\setupsidebars\setupsidebar

\unexpanded\def\startsidebar
  {\dosingleempty\anch_sidebars_start}

\def\anch_sidebars_start[#1]%
  {\bgroup
   \def\currentsidebar{#1}%
   \dontleavehmode
   \global\advance\c_anch_sidebars_n\plusone
   \advance\c_anch_sidebars_distance\sidebarparameter\c!distance
   \startpositionoverlay{text-1}%
     \normalexpanded{\setMPpositiongraphicrange % maybe expand in definition
       {b:sidebar:\the\c_anch_sidebars_n}%
       {e:sidebar:\the\c_anch_sidebars_n}%
       {mpos:sidebar}%
       {self=sidebar:\the\c_anch_sidebars_n,
        linewidth=\sidebarparameter\c!rulethickness,
        linecolor=\sidebarparameter\c!rulecolor,
        alternative=\sidebarparameter\c!alternative,
        topoffset=\sidebarparameter\c!topoffset,
        bottomoffset=\sidebarparameter\c!bottomoffset,
        distance=\the\c_anch_sidebars_distance}}%
   \stoppositionoverlay
   \bpos{sidebar:\the\c_anch_sidebars_n}}

\unexpanded\def\stopsidebar
  {\removelastspace
   \epos{sidebar:\the\c_anch_sidebars_n}
   \carryoverpar\egroup}

%D Let's keep this nice and simple (okay, we could pass the 6 variables in
%D one lua call).

\startMPpositionmethod{mpos:sidebar}
    \startMPpositiongraphic{mpos:sidebar}{linecolor,linewidth,distance,alternative}%
        if unknown context_apos : input mp-apos.mpiv ; fi ;
        anch_sidebars_draw (
            \MPp\MPbself,\MPp\MPeself,\MPy\MPbself,\MPy\MPeself,\MPh\MPbself,\MPd\MPeself,
            \MPx{\textanchor},\MPy{\textanchor},\MPw{\textanchor},\MPh{\textanchor},
            \MPvar{alternative},\MPvar{distance},\MPvar{linewidth},\MPvar{linecolor},
            \MPvar{topoffset}, \MPvar{bottomoffset}
        ) ;
    \stopMPpositiongraphic
    \MPpositiongraphic{mpos:sidebar}{}%
\stopMPpositionmethod

%D We now reimplement the margin rules handler defined in
%D \type {core-rul}:
%D
%D \setupmarginrules[level=5]
%D
%D \startmarginrule[1]
%D First we set the level at~5. Next we typeset this first
%D paragraph as a level~1 one. As expected no rule show up.
%D \stopmarginrule
%D
%D \startmarginrule[5]
%D The second paragraph is a level~5 one. As we can see here,
%D the marginal rule gets a width according to its level.
%D \stopmarginrule
%D
%D \startmarginrule[8]
%D It will of course be no surprise that this third paragraph
%D has a even thicker margin rule. This behavior can be
%D overruled by specifying the width explictly.
%D \stopmarginrule

\definesidebar
  [\v!margin]
  [\c!rulethickness=\@@karulethickness,
   \c!distance=\dimexpr\leftmargindistance-\@@karulethickness/2\relax]

\definecomplexorsimple\startmarginrule

\def\simplestartmarginrule
  {\complexstartmarginrule[1]}

\def\complexstartmarginrule[#1]%
  {\bgroup
   \ifnum#1<\@@kalevel\relax
     \let\stopmarginrule\egroup
   \else
     \def\@@kadefaultwidth{#1}%
     \let\stopmarginrule\dostopmarginrule
     \normalexpanded{\startsidebar[\v!margin]}% why expanded
   \fi}

\def\dostopmarginrule
  {\stopsidebar
   \egroup}

\protect \endinput