% \iffalse meta-comment
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% forest-ext-multi.dtx
% Additions and changes Copyright (C) 2025-2026 Clea F. Rees.
% Code from skeleton.dtx Copyright (C) 2015-2024 Scott Pakin (see below).
%
% This work may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either version 1.3c
% of this license or (at your option) any later version.
% The latest version of this license is in
%   https://www.latex-project.org/lppl.txt
% and version 1.3c or later is part of all distributions of LaTeX
% version 2008-05-04 or later.
%
% This work has the LPPL maintenance status 'muaintained'.
%
% The Current Maintainer of this work is Clea F. Rees.
%
% This work consists of all files listed in manifest.txt.
%
% The file forest-ext-multi.dtx is a derived work under the terms of the
% LPPL. It is based on version 2.4 of skeleton.dtx which is part of
% dtxtut by Scott Pakin. A copy of dtxtut, including the
% unmodified version of skeleton.dtx is available from
% https://www.ctan.org/pkg/dtxtut and released under the LPPL.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% \fi
%
% \iffalse
%<*driver>
\RequirePackage{svn-prov}
% ref. ateb Max Chernoff: https://tex.stackexchange.com/a/723294/
\def\MakePrivateLetters{\makeatletter\ExplSyntaxOn\endlinechar13}
\ExplSyntaxOff
\ProvidesFileSVN{$Id: forest-ext-multi.dtx 11668 2026-02-21 02:34:38Z cfrees $}[v0.3 \revinfo][\filebase DTX: ]
\DefineFileInfoSVN[forest-ext-multi]
\documentclass[11pt,british]{ltxdoc}
% ^^A l3doc, minted both load fancyvrb
% ^^A fancyvrb overwrites svn-prov's macros without warning
% ^^A restore \fileversion \filerev in case we're using something troublesome
\GetFileInfoSVN{forest-ext-multi}
\begin{document}
\DocInput{\filename}
\end{document}
%</driver>
% \fi
%
% \title{ext.multi}
% \author{Clea F. Rees\thanks{%
%     Bug tracker:
%     \href{https://codeberg.org/cfr/prooftrees/issues}{\url{codeberg.org/cfr/prooftrees/issues}}
%     \textbar{} Code:
%     \href{https://codeberg.org/cfr/prooftrees}{\url{codeberg.org/cfr/prooftrees}}
%     % \textbar{} Mirror:
%     % \href{https://github.com/cfr42/prooftrees}{\url{github.com/cfr42/prooftrees}}% 
% }}
% \date{\forestextdocdate}
% \maketitle
%
% ^^A forest-lib-ext.multi{-debug} 
% ^^A <<< 
%<*sty>
% \permissivelines
%    \begin{macrocode}
\NeedsTeXFormat{LaTeX2e}
%% $Id: forest-ext-multi.dtx 11668 2026-02-21 02:34:38Z cfrees $}
%<!debug>    \ProvidesForestLibrary{ext.multi}[2025-12-05 v0.1]
%<debug>    \ProvidesForestLibrary{ext.multi-debug}[2025-12-05 v0.1]
%
%<!debug>    \disable@package@load {forest-lib-ext.multi-debug}
%<debug>    \disable@package@load {forest-lib-ext.multi}
{%
%<!debug>      \PackageWarning {ext.multi (forest library)}
%<debug>      \PackageWarning {ext.multi-debug (forest library)}
  {Only one of ext.multi and ext.multi-debug should be loaded.
    Since the
%<!debug>        ext.multi
%<debug>        ext.multi-debug
    library has already been loaded, I will ignore your request for
%<!debug>        ext.multi-debug.%
%<debug>        ext.multi.%
  }%
}
%    \end{macrocode}
% \iffalse
% ^^A Paid â defnyddio \GetFileInfoSVN*/\GetFileInfoSVN{} yn y fan hon!!
% \fi
% We don't want inconsistent names in hooks.
%    \begin{macrocode}
\SetDefaultHookLabel{forest-ext/multi}
\forestset{
%    \end{macrocode}
% Public options.
% ^^A % Booleans.
% ^^A %    \begin{macrocode}
% ^^A %    \end{macrocode}
% ^^A % Counts.
% ^^A %    \begin{macrocode}
% ^^A %    \end{macrocode}
% \begin{fkeylist}{every parent,other parents}
% Keylists.
%    \begin{macrocode}
  declare keylist={every parent}{},
  declare keylist={other parents}{},
%    \end{macrocode}
% \end{fkeylist}
% Generic toks.
%    \begin{macrocode}
%    \end{macrocode}
% Internal options.
%    \begin{macrocode}
  declare boolean={multi@connector}{0},
  declare count={multi@n@parents}{0},
  declare count={multi@connects@fosterling}{-1},
  declare count={multi@connects@foster@parent}{-1},
  declare keylist={multi@foster@parents}{},
  declare keylist={multi@fosterlings}{},
  declare keylist={multi@all@parents}{},
  declare toks={multi@edge}{},
  declare toks={multi@edge@subpath}{edge},
  declare toks={multi@edge@sublast}{--},
  declare toks={multi@edge@route}{--},
  declare toks={multi@parent@of}{},
%    \end{macrocode}
% \texseans[My answer:]{695602}.
% \texseans{695600}[Alan Munn], which was based on my original answer.
%
% Public registers.
%    \begin{macrocode}
%<debug>      declare boolean register={debug multi phantoms},
%<debug>      not debug multi phantoms,
%    \end{macrocode}
% Internal scratch registers.
%    \begin{macrocode}
  declare count register={multi@temp@counta},
  multi@temp@counta=0,
  declare toks register={multi@temp@toksa},
  multi@temp@toksa={},
  declare toks register={multi@temp@toksb},
  multi@temp@toksb={},
%    \end{macrocode}
% \begin{fstep}{fosterlings,foster parents,every fosterling,every foster parent,c fosterling,c foster parent}
%   Convenience multi-step nodewalk steps.
%    \begin{macrocode}
  define long step={fosterlings}{}{%
    if multi@fosterlings={}{}{%
      split option={multi@fosterlings}{,}{id}%
    }%
  },
  define long step={foster parents}{}{%
    if multi@foster@parents={}{}{%
      split option={multi@foster@parents}{,}{id}%
    }%
  },
  define long step={every fosterling}{n args=1}{%
    filter={#1}{>O_=!{multi@foster@parents}{}}%
  },
  define long step={every foster parent}{n args=1}{%
    filter={#1}{>O_=!{multi@fosterlings}{}}%
  },
  define long step={c fosterling}{}{%
    id/.option=multi@connects@fosterling%
  },
  define long step={c foster parent}{}{%
    id/.option=multi@connects@foster@parent%
  },
%    \end{macrocode}
% \end{fstep}
% \begin{fstyle}{multi}% ^^A <<<
%   Make this node a grandchild of its current parent and insert specified parents.
%    \begin{macrocode}
  multi/.style={%
%<debug>      debug@multi=Execute style multi at,
%<debug>      debug@multi@option=id,
    split={#1}{,}{multi@parent},
%<debug>      debug@multi@option=multi@n@parents,
%<debug>      debug@multi@option=multi@all@parents,
    before typesetting nodes={%
      multi@parents/.process={%
        OOOw
        {name}
        {multi@n@parents}
        {multi@all@parents}
        {{##1}}%
      },
      delay n=2{%
        multi@edge+= {(.child anchor) },
        multi@temp@counta'=0,
        split option={multi@all@parents}{,}{multi@also@parent},
      },
      delay n=3{%
%<debug>      debug@multi@option=id,
%<debug>      debug@multi@option=multi@edge,
        edge path'/.option=multi@edge,
      },
    },
  },
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
% \begin{fstyle}{multi@also@parent}% ^^A <<<
%   Auxiliary.
%    \begin{macrocode}
  multi@also@parent/.style={%
%<debug>      debug@multi=Execute style multi@also@parent to for #1 at,
%<debug>      debug@multi@option=id,
    multi@temp@counta'+=1,
    multi@edge+/.process={ 
      OR= ? O w 
      {multi@n@parents}{multi@temp@counta}
      {multi@edge@sublast}{multi@edge@subpath}
      {##1 (#1.parent anchor) }
    },
  },
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
% \begin{fstyle}{multi@parent}% ^^A <<<
%   Insert a co-parent.
%
%   Note \texttt{delay} required in case \texttt{name} specified by user.
%    \begin{macrocode}
  multi@parent/.style={%
%<debug>      debug@multi=Execute style multi@parent to add #1 at,
%<debug>      debug@multi@option=id,
%<debug>      debug@multi@option=every parent,
    multi@n@parents'+=1,
    delay/.process={Ow{multi@n@parents}{%
        multi@all@parents+/.process={Ow{name}{parent ##1 of ####1}},
        insert before/.process={%
          OOw2{name}{every parent}
          {%
            [#1,name=parent ##1 of ####1,multi@parent@of=####1, 
              ####2]%
          }%
        },
      }%
    },
  },
% \end{fstyle}% ^^A >>>
% \begin{fstyle}{multi@parents}% ^^A <<<
%   Adjust relns.
%
%   Arguments: name, no.~parents, parents
%    \begin{macrocode}
  multi@parents/.style n args=3{%
%<debug>      debug@multi=Executing style multi@parents with,
%<debug>      debug@multi=options #1 #2 and #3,
    if={>nw+P{#2}{isodd(##1)}}{%
      multi@temp@counta/.expanded=\inteval{(#2 + 1)/2},
      for nodewalk={%
        name/.expanded=parent \foresteregister{multi@temp@counta} of #1 %
      }{%
        append=#1,
      },
    }{%
      multi@temp@counta/.expanded=\inteval{#2/2},
%<debug>      debug@multi@register=multi@temp@counta,
      for nodewalk={%
        name/.expanded=parent \foresteregister{multi@temp@counta} of #1 %
      }{%
        insert after={%
          [,coordinate,no edge, 
            tier=multi@tier@#1@parents,
            delay={%
%<debug>      debug@multi=Appending #1 to,
%<debug>      debug@multi@option=name,
              append=#1,
            },
          ]%
        },
      },
    },
  },
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
%    \begin{macrocode}
%    \end{macrocode}
% \begin{fstyle}{multi@add@parent}% ^^A <<<
%   Connect an additional parent.
%
%   Argument: id of current node; dynamic tree operation; keylist for child; id of additional parent (extant).
%    \begin{macrocode}
  multi@add@parent/.style n args=4{%
%<debug>      debug@multi=Execute style multi@add@parent to add #4 at,
%<debug>      debug@multi@option=id,
%<debug>      debug@multi=Arguments: #1: #2: #3: #4,
%<debug>      debug@multi@option=every parent,
    delay n=2{%
      for nodewalk={%
        id=#4%
      }{%
        multi@fosterlings+=#1,
%<debug>      debug@multi=dynamic action #2,
%<debug>      debug@multi@option=parent anchor,
        #2={%
          [,
            multi@phantom,
            multi@connector,
            multi@connects@fosterling=#1,
            multi@connects@foster@parent=#4,
            for current/.option=!{id=#1}.every parent,
            delay n=3{%
              do dynamics,
              edge path'/.process={%
                Ow {!{id=#1}.multi@edge@route} {%
                  (!c fosterling.child anchor) 
                  ##1 (!c foster parent.parent anchor) %
                }%
              },
              also={#3},
%<debug>      debug@multi@option=id,
%<debug>      debug@multi=edge path and edge,
%<debug>      typeout/.option=edge path,
%<debug>      debug@multi@option=edge,
            },
          ]%
        },%
      },
    },
  },
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
% \begin{fstyle}{also parent,+also parent,also parent+}% ^^A <<<
%   Make an existing node in the tree an additional parent of the current node.
%   What actually happens is that the specified node gets a new child with a copy of the current node's content.
%   However, this child is just like a \texttt{phantom}, except that it has a visible edge.
%   This edge can then be defined to look as if it connects the current node to the additional parent.
%
%   Arguments: dynamic tree operation; parent:options for new node 
%
%   Why do I need to double hashes twice here?
%    \begin{macrocode}
  also parent/.style 2 args={%
%<debug>    debug@multi=Executing style also parent at,
%<debug>    debug@multi@option=id,
    delay={%
      split={#2}{:}{multi@temp@toksa,multi@temp@toksb},
%<debug>    debug@multi@register=multi@temp@toksa,
%<debug>    debug@multi@register=multi@temp@toksb,
      if nodewalk valid={name/.register=multi@temp@toksa}{%
        multi@temp@counta/.option=!{name/.register=multi@temp@toksa}.id,
      }{%
        multi@temp@counta/.option/.process={Rw{multi@temp@toksa}{##1.id}},
      },
%<debug>    debug@multi@register=multi@temp@counta,
      multi@foster@parents+/.register=multi@temp@counta,
      multi@add@parent/.process={%
        O_RwR
        {id}
        {#1}
        {multi@temp@toksb}
        {{##1}}
        {multi@temp@counta}%
      },
    },
  },
  +also parent/.style={%
%<debug>    debug@multi=Executing style +also parent at,
%<debug>    debug@multi@option=id,
    also parent={prepend}{#1},
  },
  also parent+/.style={%
%<debug>    debug@multi=Executing style also parent+ at,
%<debug>    debug@multi@option=id,
    also parent={append}{#1},
  },
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
% \begin{fstyle}{}% ^^A <<<
%    \begin{macrocode}
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
% \begin{fstyle}{multi@phantom}% ^^A <<<
%   Not really phantoms.
%    \begin{macrocode}
  multi@phantom/.style={
    before drawing tree={%
%<debug>      if debug multi phantoms={%
%<debug>        rectangle,
%<debug>        if content={}{,
%<debug>          draw=red,
%<debug>        }{%
%<debug>          red,
%<debug>        },
%<debug>      }{%
      coordinate,
%<debug>      },
      typeset node,
    },
  },
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
% \begin{fstyle}{add parent}% ^^A <<<
%   Add a new node to the tree and connect it to the current node.
%    \begin{macrocode}
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
% \begin{fstyle}{debug@multi,debug@multi@register,debug@multi@option}% ^^A <<<
%   Internal styles for debugging.
%   Should not be used directly, but may be applied by loading the debugging code.
%    \begin{macrocode}
%<debug>    debug@multi/.code={%
%<debug>      \ExpandArgs {e} \typeout{[Forest ext.multi debug]:: \detokenize{#1}}%
%<debug>    },
%<debug>    debug@multi@register/.code={%
%<debug>      \ExpandArgs {e} \typeout{[Forest ext.multi debug]:: \detokenize{#1}
%<debug>        = \foresteregister{#1}%
%<debug>      }%
%<debug>    },
%<debug>    debug@multi@option/.code={%
%<debug>      \ExpandArgs {e} \typeout{[Forest ext.multi debug]:: \detokenize{#1}
%<debug>        = \foresteoption{#1}%
%<debug>      }%
%<debug>    },
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
% \begin{fstyle}{debug multi phantoms,not debug multi phantoms}% ^^A <<<
%   Supply a code key as substitute for the boolean if the debugging code isn't loaded.
%    \begin{macrocode}
%<!debug>    debug multi phantoms/.code={%
%<!debug>      \PackageWarning{forest-lib-ext.multi}{%
%<!debug>        You requested the style 'debug multi phantoms', 
%<!debug>        but did not load the debugging code. 
%<!debug>        Either load 'ext.multi-debug' instead of 
%<!debug>        'ext.multi' or remove this style.
%<!debug>      }%
%<!debug>    }, 
%<!debug>    node debug multi phantoms/.code={%
%<!debug>      \PackageWarning{forest-lib-ext.multi}{%
%<!debug>        You requested the style 'not debug multi phantoms', 
%<!debug>        but did not load the debugging code. 
%<!debug>        Either load 'ext.multi-debug' instead of 
%<!debug>        'ext.multi' or remove this style.
%<!debug>      }%
%<!debug>    }, 
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
% We need empty defaults here so that e.g.~\pkg{ext.ling} can be loaded without \pkg{edges}, in which case the set of default is empty.
% If \pkg{edges} is loaded, we overwrite this style in a hook at \texttt{begindocument}.
%    \begin{macrocode}
%<!debug>      libraries/ext.multi/defaults/.style=
%<debug>      libraries/ext.multi-debug/defaults/.style=
  {},
}
%    \end{macrocode}
% We need conditional code in case \pkg{edges} is loaded.
%    \begin{macrocode}
\AddToHook{begindocument}{%
  \IfPackageLoadedT{forest-lib-edges}{%
%<!debug>        \PackageInfo{forest-lib-ext.multi}
%<debug>        \PackageInfo{forest-lib-ext.multi-debug}
    {Found the edges library. Enabling support code.}%
    \usetikzlibrary{ext.paths.ortho}%
    \forestset{%
%    \end{macrocode}
% \begin{fstyle}{multi@forked@edge}% ^^A <<<
%   I wish \pkg{forest} used booleans or similar a bit more extensively here so this was easier to handle (without clobbering).
%    \begin{macrocode}
      multi@forked@edge/.style={%
        /forest/.cd,
        /tikz/ext/ortho/distance/.process={Ow{fork sep}{-##1}},
        every parent+={%
          forked edge,
          /tikz/ext/ortho/distance/.process={Ow{fork sep}{-##1}},
        },
        multi@edge@subpath={%
          (.child anchor) -|-
        },
        multi@edge@sublast={%
          (.child anchor) -|-
        },
        multi@edge@route={%
          -|-
        },
      },
%    \end{macrocode}
% \end{fstyle}% ^^A >>>
%   Setup some (hopefully) intuitive defaults.
%
%   A negative value for \texttt{ext/ortho/distance} is measured from the target coordinate rather than the start.
%   We are constructing the paths backwards in comparison with \pkg{forest}.
%   \texttt{0.5em} is the \pkg{forest} default.
%   Do \textbf{not} try passing the option value here!
%    \begin{macrocode}
%<!debug>      libraries/ext.multi/defaults/.style=
%<debug>      libraries/ext.multi-debug/defaults/.style=
      {%
        default preamble+={
          Autoforward={fork sep}{%
            every parent+={%
              fork sep=##1,
              edge+={/tikz/ext/ortho/distance=-##1},
            },
            edge+={/tikz/ext/ortho/distance=-##1},
          },
          fork sep'=0.5em,
          forked edge'/.forward to=/forest/multi@forked@edge,
        },
      },
%    \end{macrocode}
% There's no ‘hook’ mechanism for this, so there is not really a nice or robust way of doing this, I don't think.
% For the \pkg{edges} library, in particular, there are, in fact, no defaults at all ....
%
%    \begin{macrocode}
      libraries/edges/defaults/.append style={%
%<!debug>      libraries/ext.multi/defaults,
%<debug>      libraries/ext.multi-debug/defaults,
        /utils/exec={%
%<!debug>      \PackageInfo{forest-lib-ext.multi}
%<debug>      \PackageInfo{forest-lib-ext.multi-debug}
          {%
            Appending compatibility code for forked edges to default settings.%
          }%
        },
      }%
    }%
  }%
%    \end{macrocode}
% \changes{v0.2}{2026-01-21}{Try to add something if tagging. But order is wrong. I think the whole specific approach here is misguided. But the basic infrastructure I think is maybe OK. Just I don't think producing alt text for arbitrary trees is good like this. Maybe just drop the structural descriptions? And just read the node content? Or what?}
%    \begin{macrocode}
  \ifcsname l_forestext_tagging_custom_bool\endcsname
%<!debug>        \PackageInfo{forest-lib-ext.multi}
%<debug>        \PackageInfo{forest-lib-ext.multi-debug}
    {%
      Found the ext.tagging or ext.tagging-debug library. 
      Enabling support code.%
    }%
    \forestset{%
%<!debug>      libraries/ext.multi/defaults/.append style=
%<debug>      libraries/ext.multi-debug/defaults/.append style=
      {%
        also parent/.append style={%
          before collating tags={%
            alt text+/.process={Ow{##2.content}{ also child of ####1 }},
          },
        },
        multi/.append style={%
          before collating tags={%
            alt text+={multiple parents: },
            split={#1}{,}{multi@to@alt},
          },
          multi@to@alt/.style={%
            alt text+={#1, },
          },
        },
      },
    }%
  \fi
}
%    \end{macrocode}
%</sty>
%^^A >>>
%
% ^^A \Finale
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
%^^A vim: et:tw=0:sw=2:ts=2:foldmethod=marker:fmr=<<<,>>>: