%D \module
%D   [       file=strc-itm,
%D        version=2008.10.20,
%D          title=\CONTEXT\ Structure Macros,
%D       subtitle=Itemgroups,
%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 Structure Macros / Itemgroups}

\registerctxluafile{strc-itm}{}

%D As we analyze/register widths and such we could as well push and pop the numbers
%D at the \LUA\ end (which saves a few calls).
%D
%D Cleaning up this module happened around the time when Kate Bush came up with the
%D nicest numbered list of words: 50 Words For Snow. It's therefore no surprise that
%D I had that cd running several times when updating this code. One of the
%D highlights of 2011.
%D
%D This module needs to be rewritten but that is tricky with respect to
%D compatibilitity. Basically each major variant (regular, text, columns,
%D horizontal, etc) needs to be on its own.

% todo: check breaks
% todo: check grouping
% todo: fixedconversion

% \startitemize[n,packed]
% \item test \item test \item test
% \stopitemize
%
% \startitemize[n,packed,reverse]
% \item test \item test \item test
% \stopitemize
%
% \startitemize[n,packed,reverse] \item test \item test \stopitemize
% \startitemize[continue]
% \item test \startitemize[n,packed] \item test \item test \stopitemize
% \item test
% \item test
% \stopitemize
% \startitemize[continue] \item test \stopitemize
%
% \startitemize[n,packed] \item test \item test \stopitemize
% \startitemize[continue] \item test            \stopitemize
% \startitemize[continue] \item test            \stopitemize
%
% \setupwhitespace[big]
% \starttext
%     test \startitemize[joinedup]                \item test \item test \stopitemize test \par
%     test \startitemize[joinedup,nowhite]        \item test \item test \stopitemize test \par
%     test \startitemize[joinedup,nowhite,before] \item test \item test \stopitemize test \par
%     test \startitemize[joinedup,nowhite,after]  \item test \item test \stopitemize test \par
% \stoptext
%
% test / example
%
% \startnarrower[left] \startcolumns[n=3] \startitemize
% \item \input ward \item \input ward \item \input ward
% \stopitemize \stopcolumns\stopnarrower \blank
%
% \startnarrower[left] \startitemize[columns,three]
% \item \input ward \item \input ward \item \input ward
% \stopitemize \stopnarrower \blank
%
% \setupitemize[leftmargin=1.5em] \startitemize[columns,three]
% \item \input ward \item \input ward \item \input ward
% \stopitemize \blank
%
% beware, we don't group (yet) as we want to keep the left/right skip
%
% \startitemize
% \startitem \stopitem
% some intermediate text that will properly indent
% \startitem \stopitem
% \stopitem
%
% so we need to keep that property
%
% \startitemize
%   \starthead {xx} test \stophead
%   \startitem test \stopitem
%   \startitem test \stopitem
% \stopitemize
%
% Sometimes the user demands get pretty weird:
%
% \startitemize
%   \item test
%   \item test
%   \headsym{xx} test \par test
% \stopitemize
%
% aligned items
%
% \startitemize[n,fit,broad][itemalign=flushright]
%      \dorecurse{100}{\item The first item.}
% \stopitemize
%
% \setupitemgroup[itemize][each][fit]
% \setupitemgroup[itemize][each][distance=.5em,factor=1,itemalign=flushright]
%
% \startitemize[n]
%      \dorecurse{100}{\item The first item.}
% \stopitemize
%
% \defineitemgroup[gbitemize]
% \setupitemgroup[gbitemize][each][headstyle=bold]
%
% \startgbitemize
% \txt{italian} some italians like this kind of cross||breed between
%   an itemize and a description
% \txt{sicilians} i wonder how many sicilian mathematicians do a thesis
%   on the math involved in predicting the next big bang of the vulcano
% \stopgbitemize
%
% \startitemize[n,repeat]
%     \noitem \startitemize[a] \item Item 1.a. \item Item 1.b. \stopitemize
%     \noitem \startitemize[a] \item Item 2.a. \item Item 2.b. \stopitemize
% \stopitemize
%
% \startitemize[n,repeat][width=0pt]
%   \noitem \startitemize[a][width=2em] \item Item 1.a. \item Item 1.b. \stopitemize
%   \noitem \startitemize[a][width=2em] \item Item 2.a. \item Item 2.b. \stopitemize
% \stopitemize
%
% \startbuffer
% \item
%   \startitemize[n]
%   \item item 1.1
%   \item item 1.2
%   \startitemize[n] \item item 1.2.1 \item item 1.2.2 \stopitemize
%   \item item 1.3
%   \stopitemize
% \item
%   \startitemize[n] \item item 2.1 \item item 2.2 \stopitemize
% \item item 3
%   \startitemize[n] \item item 3.1 \item item 3.2 \stopitemize
% \item
%   \startitemize[n] \item item 4.1 \item item 4.2 \stopitemize
% \stopbuffer
%
% \startitemize[n,repeat,6*broad,packed] \getbuffer \stopitemize \blank[3*big]
% \startitemize[n,repeat,packed]         \getbuffer \stopitemize \blank[3*big]
% \setupitemize[each][atmargin][width=3em]
% \startitemize[n,repeat,packed]         \getbuffer \stopitemize
%
% todo: assume startitem ... stopitem and do an autostopitem .. cleaner for
% elements
%
% \startitemize[text][space=medium]
% \item one \item two \item three
% \stopitemize
%
% For Giuseppe "Oblomov" Bilotta, inspired on a suggestion by Taco
% Hoekwater.
%
% \def\MyItemCommand#1{{\bf#1}\quad}
% \setupitemgroup[itemize][command=\MyItemCommand]
%
% \startitemize
% \item {test} is this okay?
% \item {test} is this okay?
% \item {test} is this okay?
% \stopitemize

\unprotect

\newconditional\c_strc_itemgroups_sub
\newconditional\c_strc_itemgroups_head
\newconditional\c_strc_itemgroups_intro
\newconditional\c_strc_itemgroups_randomize
\newconditional\c_strc_itemgroups_horizontal
\newconditional\c_strc_itemgroups_collecting
\newconditional\c_strc_itemgroups_auto_intro
\newconditional\c_strc_itemgroups_pack
\newconditional\c_strc_itemgroups_paragraph
\newconditional\c_strc_itemgroups_text
\newconditional\c_strc_itemgroups_text_saved
\newconditional\c_strc_itemgroups_first
\newconditional\c_strc_itemgroups_before
\newconditional\c_strc_itemgroups_after
\newconditional\c_strc_itemgroups_nowhite
\newconditional\c_strc_itemgroups_joined
\newconditional\c_strc_itemgroups_reverse
\newconditional\c_strc_itemgroups_continue
\newconditional\c_strc_itemgroups_fitting
\newconditional\c_strc_itemgroups_indented_first
\newconditional\c_strc_itemgroups_inline
\newconditional\c_strc_itemgroups_columns
\newconditional\c_strc_itemgroups_concat
\newconditional\c_strc_itemgroups_txt
\newconditional\c_strc_itemgroups_extra
\newconditional\c_strc_itemgroups_repeat
\newconditional\c_strc_itemgroups_inline_head

% 0 = before/after
% 1 = between unless before
% 2 = between

\newconstant   \c_strc_itemgroups_spacing_mode   \c_strc_itemgroups_spacing_mode\plustwo
\newconditional\c_strc_itemgroups_optimize       \settrue\c_strc_itemgroups_optimize
\newconditional\c_strc_itemgroups_auto_concat    \settrue\c_strc_itemgroups_auto_concat

\newsignal     \d_strc_itemgroups_signal

\newbox        \b_strc_itemgroups

\newdimen      \d_strc_itemgroups_list_width
\newdimen      \d_strc_itemgroups_asked_width

\newdimen      \d_strc_itemgroups_max_width      % multipass
\newcount      \c_strc_itemgroups_max_items      % multipass

\newcount      \c_strc_itemgroups_n_of_items
\newcount      \c_strc_itemgroups_nesting
\newcount      \c_strc_itemgroups_column_depth

\def           \v_strc_itemgroups_counter        {itemgroup:\currentparentitemgroup}
\let           \m_strc_itemgroups_repeat_start   \empty
\def           \v_strc_itemgroups_unknown_symbol {?}
\let           \m_strc_itemgroups_indenting      \empty
\let           \m_strc_itemgroups_destination    \empty

\let           \currentitemlevel                 \!!zerocount % public
\def           \currentnofitems                  {\the\c_strc_itemgroups_max_items}
\def           \currentitemnumber                {\strc_counters_raw_sub\v_strc_itemgroups_counter\currentitemlevel} % public

\newtoks       \itemgroupcommands                % maybe public

\def           \currentitemgroupsymbol           {n}    % here we cannot use a _ in the name
\let           \currentitemgroupconversionset    \empty % here we cannot use a _ in the name
\let           \currentitemgroupsegments         \empty

\def\strc_itemgroups_register_status
  {\clf_registeritemgroup{\currentparentitemgroup}\c_strc_itemgroups_nesting\c_strc_itemgroups_n_of_items\dimexpr\itemgroupparameter\c!maxwidth\relax}

\def\strc_itemgroups_check_n_of_items % we could do this at the lua end and save a call (i.e. will be dimen and counter)
  {\clf_analyzeitemgroup{\currentparentitemgroup}\c_strc_itemgroups_nesting\relax
   \edef\currentnofitems{\the\c_strc_itemgroups_max_items}}

% todo: \dodosetreference -> \strc_counters_register_component (to be checked)

\def\strc_itemgroups_insert_reference % we will make a decent number helper
  {\iftrialtypesetting \else \ifx\currentitemreference \empty \else
     \strc_itemgroups_insert_reference_indeed
   \fi \fi}

\def\strc_itemgroups_insert_extra_reference
  {\iftrialtypesetting \else \ifx\currentitemreference \empty \else
     \normalexpanded{\textreference[\currentitemreference]{\strc_itemgroups_extra_symbol}}%
   \fi \fi}

\def\strc_itemgroups_insert_reference_indeed % maybe we need a 'frozen counter' numberdata blob / quick hack .. .mive this to strc-ref
  {% needs testing, gave problems:
   \setnextinternalreference
   % no need to collect nodes in \b_strc_destination_nodes here ... maybe at some point
   \strc_references_start_destination_nodes
   % this is somewhat over the top ... we should use the counter's reference
   \clf_setdestinationattribute
     {%
         metadata {%
             kind            {item}% was item, why?
         \ifx\currentreferencecoding\s!xml
             xmlroot         {\xmldocument}% only useful when text
         \fi
             catcodes        \catcodetable
         }%
         references {%
             internal        \locationcount % no: this spoils references
           % block           {\currentsectionblock}%
             view            {\interactionparameter\c!focus}%
             prefix          {\referenceprefix}%
             reference       {\currentitemreference}%
         }%
         prefixdata {%
             prefix          {\namedcounterparameter\v_strc_itemgroups_counter\c!prefix}%
             separatorset    {\namedcounterparameter\v_strc_itemgroups_counter\c!prefixseparatorset}%
             conversion      {\namedcounterparameter\v_strc_itemgroups_counter\c!prefixconversion}%
             conversionset   {\namedcounterparameter\v_strc_itemgroups_counter\c!prefixconversionset}%
             set             {\namedcounterparameter\v_strc_itemgroups_counter\c!prefixset}%
             segments        {\namedcounterparameter\v_strc_itemgroups_counter\c!prefixsegments}%
           % segments        {\askedprefixsegments}%
             connector       {\namedcounterparameter\v_strc_itemgroups_counter\c!prefixconnector}%
         }%
         numberdata {%
             numbers         {\v_strc_itemgroups_counter}%
             separatorset    {\namedcounterparameter\v_strc_itemgroups_counter\c!numberseparatorset}%
           % conversion      {\namedcounterparameter\v_strc_itemgroups_counter\c!numberconversion}%
           % conversionset   {\namedcounterparameter\v_strc_itemgroups_counter\c!numberconversionset}%
           % fixedconversion {\currentitemgroupconversionset}%
             conversionset   {fixed::\currentitemgroupconversionset}% temp hack
           %
           % for the moment no stopper, we need to make references configurable first
           % stopper         {\namedcounterparameter\v_strc_itemgroups_counter\c!numberstopper}%
             segments        {\namedcounterparameter\v_strc_itemgroups_counter\c!numbersegments}%
         }%
     }%
   \relax
   \strc_references_stop_destination_nodes
   \xdef\currentdestinationattribute{\number\lastdestinationattribute}%
   % will become an option:
   \ifnum\lastdestinationattribute>\zerocount
     \dontleavehmode\hbox attr \destinationattribute\lastdestinationattribute\bgroup
       \strc_references_flush_destination_nodes
     \egroup
   \fi}

%D Defining and setup:

\installcorenamespace{itemgroup}
\installcorenamespace{itemgroupoption}
\installcorenamespace{itemgroupsetting}
\installcorenamespace{itemgroupkeyword}
\installcorenamespace{itemgroupalign}
\installcorenamespace{itemgrouplocal}
\installcorenamespace{itemgroupglobal}
\installcorenamespace{itemgroupdistance}
\installcorenamespace{itemgroupstack}
\installcorenamespace{itemgroupfirst}
\installcorenamespace{itemgroupstart}

\installcommandhandler \??itemgroup {itemgroup} \??itemgroup

\let\setupitemgroups\setupitemgroup

\appendtoks
    \setuevalue{\e!start\currentitemgroup}{\startitemgroup[\currentitemgroup]}%
    \setuevalue{\e!stop \currentitemgroup}{\stopitemgroup}%
    \setuevalue{\e!setup\currentitemgroup\e!endsetup}{\setupitemgroup[\currentitemgroup]}% obsolete
    \let\currentparentitemgroup\currentitemgroup
    \definecounter[\v_strc_itemgroups_counter]%
    % beware ... we cannot use _ as the conversion set is not expanded
    % \defineconversionset[\v_strc_itemgroups_counter][\currentitemgroupconversionset][\currentitemgroupsymbol]%
\to \everydefineitemgroup

%D Global states

\def\strc_itemgroups_store_continue_state#options#settings%
   {\setxvalue{\??itemgroupoption \currentitemgroup}{\strc_itemgroups_process_options{#options}}%
    \setgvalue{\??itemgroupsetting\currentitemgroup}{\setupcurrentitemgroup[#settings]}}

\def\strc_itemgroups_fetch_continue_state
  {\csname\??itemgroupoption \currentitemgroup\endcsname
   \csname\??itemgroupsetting\currentitemgroup\endcsname}

\def\strc_itemgroups_reset_continue_state
  {\expandafter\glet\csname\??itemgroupoption \currentitemgroup\endcsname\relax
   \expandafter\glet\csname\??itemgroupsetting\currentitemgroup\endcsname\relax}

% These will become keywords. We will also add a feature to keep the while set
% together.

\definevspacing[\v!item @0]     [penalty:0]     % allow
\definevspacing[\v!item @10000] [penalty:10000] % no
\definevspacing[\v!item @-5]    [penalty:-5]
\definevspacing[\v!item @5]     [penalty:5]
\definevspacing[\v!item @500]   [penalty:500]   % discourage .. too low, 5000 is better

\def\strc_itemgroups_insert_break_when_needed#break%
  {\ifconditional\c_strc_itemgroups_optimize
     \ifconditional\c_strc_itemgroups_text \else
       #break\relax
     \fi
   \fi}

\def\strc_itemgroups_insert_breakallow       {\strc_itemgroups_insert_break_when_needed\strc_itemgroups_insert_breakallow_indeed}
\def\strc_itemgroups_insert_breakno          {\strc_itemgroups_insert_break_when_needed\strc_itemgroups_insert_breakno_indeed   }
\def\strc_itemgroups_insert_break            {\strc_itemgroups_insert_break_when_needed\strc_itemgroups_insert_break_indeed     }
\def\strc_itemgroups_insert_nobreak          {\strc_itemgroups_insert_break_when_needed\strc_itemgroups_insert_nobreak_indeed   }

\def\strc_itemgroups_insert_breakallow_indeed{\vspacing[\v!item @0]}
\def\strc_itemgroups_insert_breakno_indeed   {\vspacing[\v!item @10000]}
\def\strc_itemgroups_insert_break_indeed     {\flushnotes
                                              \vspacing[\v!item @-5]}
\def\strc_itemgroups_insert_nobreak_indeed   {\flushnotes
                                              \ifinsidecolumns % todo
                                                \vspacing[\v!item @5]%
                                              \else
                                                \vspacing[\v!item @500]%
                                              \fi}

\unexpanded\def\strc_itemgroups_process_options#options%
  {\processcommacommand[#options]\strc_itemgroups_process_option} % expansion of options is handy for xml

% \installcommalistprocessorcommand \strc_itemgroups_process_option_list \strc_itemgroups_process_option
%
% \unexpanded\def\strc_itemgroups_process_options#options%
%   {\normalexpanded{\strc_itemgroups_process_option_list[#options]}} % expansion of options is handy for xml

\def\strc_itemgroups_process_option#option%
  {\edef\itemgroupconstantvalue{#option}%
   \ifx\itemgroupconstantvalue\empty\else
     \splitatasterisk\itemgroupconstantvalue\itemgroupfirst\itemgroupsecond
     \ifx\itemgroupsecond\empty
        \let\itemgroupsecond\itemgroupfirst
        \let\itemgroupfirst\!!plusone
     \fi
     \ifcsname\??itemgroupkeyword\itemgroupsecond\endcsname
       \lastnamedcs
     \else
       \strc_itemgroups_set_symbol\itemgroupconstantvalue
     \fi
   \fi}

\def\strc_itemgroups_process_set_option_pack
  {\ifcase\c_strc_itemgroups_nesting \else
     \settrue\c_strc_itemgroups_pack
   \fi}

\def\strc_itemgroups_process_set_option_unpack
  {\ifcase\c_strc_itemgroups_nesting\else
     \setfalse\c_strc_itemgroups_pack
   \fi}

\setvalue{\??itemgroupkeyword\!!zerocount  }{} % ignore 0
\setvalue{\??itemgroupkeyword\v!packed     }{\strc_itemgroups_process_set_option_pack}
\setvalue{\??itemgroupkeyword\v!unpacked   }{\strc_itemgroups_process_set_option_unpack}
\setvalue{\??itemgroupkeyword\v!intro      }{\settrue\c_strc_itemgroups_intro} % here? not set to false
\setvalue{\??itemgroupkeyword\v!autointro  }{\settrue\c_strc_itemgroups_auto_intro}
\setvalue{\??itemgroupkeyword\v!broad      }{\ifx\itemgroupfirst\empty
                                               \let\itemgroupfirst\!!plusone
                                             \fi
                                             \letitemgroupparameter\c!factor\itemgroupfirst}
\setvalue{\??itemgroupkeyword\v!text       }{\settrue\c_strc_itemgroups_text
                                             \settrue\c_strc_itemgroups_inline
                                             \settrue\c_strc_itemgroups_joined
                                             \strc_itemgroups_process_set_option_pack}
\setvalue{\??itemgroupkeyword\v!before     }{\settrue\c_strc_itemgroups_before}
\setvalue{\??itemgroupkeyword\v!after      }{\settrue\c_strc_itemgroups_after}
\setvalue{\??itemgroupkeyword\v!nowhite    }{\settrue\c_strc_itemgroups_nowhite}
\setvalue{\??itemgroupkeyword\v!margin     }{\setitemgroupparameter\c!width{-2em}} % signal
\setvalue{\??itemgroupkeyword\v!inmargin   }{\setitemgroupparameter\c!width{-2em}} % signal
\setvalue{\??itemgroupkeyword\v!atmargin   }{\ifnum\c_strc_itemgroups_nesting>\plusone
                                               \setitemgroupparameter\c!width{0em}%
                                             \fi} % signal
\setvalue{\??itemgroupkeyword\v!intext     }{\settrue\c_strc_itemgroups_inline}
\setvalue{\??itemgroupkeyword\v!headintext }{\settrue\c_strc_itemgroups_inline_head}
\setvalue{\??itemgroupkeyword\v!loose      }{\setfalse\c_strc_itemgroups_optimize}
\setvalue{\??itemgroupkeyword\v!fit        }{\settrue\c_strc_itemgroups_fitting}
\setvalue{\??itemgroupkeyword\v!nofit      }{\setfalse\c_strc_itemgroups_fitting}
\setvalue{\??itemgroupkeyword\v!paragraph  }{\settrue\c_strc_itemgroups_paragraph
                                             \strc_itemgroups_process_set_option_pack}
\setvalue{\??itemgroupkeyword\v!joinedup   }{\settrue\c_strc_itemgroups_joined
                                             \strc_itemgroups_process_set_option_pack}
\setvalue{\??itemgroupkeyword\v!notjoinedup}{\setfalse\c_strc_itemgroups_joined}
\setvalue{\??itemgroupkeyword\v!serried    }{\edef\itemgroupfirst{-\ifx\itemgroupfirst\empty1\else\itemgroupfirst\fi}%
                                             \letitemgroupparameter\c!factor\itemgroupfirst}
\setvalue{\??itemgroupkeyword\v!stopper    }{\letitemgroupparameter\c!placestopper\v!yes} % keep {}
\setvalue{\??itemgroupkeyword\v!nostopper  }{\letitemgroupparameter\c!placestopper\v!no} % keep {}
\setvalue{\??itemgroupkeyword\v!repeat     }{\settrue\c_strc_itemgroups_repeat}
\setvalue{\??itemgroupkeyword\v!norepeat   }{\setfalse\c_strc_itemgroups_repeat}
\setvalue{\??itemgroupkeyword\v!reverse    }{\settrue\c_strc_itemgroups_reverse}
\setvalue{\??itemgroupkeyword\v!columns    }{\settrue\c_strc_itemgroups_columns}
\setvalue{\??itemgroupkeyword\v!one        }{\letitemgroupparameter\c!n\plusone}
\setvalue{\??itemgroupkeyword\v!two        }{\letitemgroupparameter\c!n\plustwo}
\setvalue{\??itemgroupkeyword\v!three      }{\letitemgroupparameter\c!n\plusthree}
\setvalue{\??itemgroupkeyword\v!four       }{\letitemgroupparameter\c!n\plusfour}
\setvalue{\??itemgroupkeyword\v!five       }{\letitemgroupparameter\c!n\plusfive}
\setvalue{\??itemgroupkeyword\v!six        }{\letitemgroupparameter\c!n\plussix}
\setvalue{\??itemgroupkeyword\v!seven      }{\letitemgroupparameter\c!n\plusseven}
\setvalue{\??itemgroupkeyword\v!eight      }{\letitemgroupparameter\c!n\pluseight}
\setvalue{\??itemgroupkeyword\v!nine       }{\letitemgroupparameter\c!n\plusnine}
\setvalue{\??itemgroupkeyword\v!standard   }{\setitemgroupparameter\c!width        {1.5\emwidth}%
                                             \setitemgroupparameter\c!distance     {.5\emwidth}%
                                            %\letitemgroupparameter\c!factor       \!!zerocount
                                             \letitemgroupparameter\c!factor       {\zerocount}%
                                             \setitemgroupparameter\c!packcriterium{\zerocount}%
                                             \letitemgroupparameter\c!inner        \empty
                                             \letitemgroupparameter\c!beforehead   \empty
                                             \letitemgroupparameter\c!afterhead    \blank
                                             \letitemgroupparameter\c!before       \blank
                                             \letitemgroupparameter\c!inbetween    \blank
                                             \letitemgroupparameter\c!after        \blank}

\def\strc_itemgroups_initialize_local
  {\setfalse\c_strc_itemgroups_inline
   \setfalse\c_strc_itemgroups_concat
   \setfalse\c_strc_itemgroups_txt
   %
   \setfalse\c_strc_itemgroups_reverse
   \setfalse\c_strc_itemgroups_intro
   \setfalse\c_strc_itemgroups_auto_intro
   \setfalse\c_strc_itemgroups_before
   \setfalse\c_strc_itemgroups_after
   \setfalse\c_strc_itemgroups_nowhite
   \setfalse\c_strc_itemgroups_randomize
   \setfalse\c_strc_itemgroups_horizontal
   \setfalse\c_strc_itemgroups_collecting
   \setfalse\c_strc_itemgroups_intro
   \setfalse\c_strc_itemgroups_continue
   % this will be a constant
   \setfalse\c_strc_itemgroups_head
   \setfalse\c_strc_itemgroups_sub
   \setfalse\c_strc_itemgroups_symbol
   \setfalse\c_strc_itemgroups_columns
   % to be checked
   \let\m_strc_itemgroups_destination\empty
   \let\strc_itemgroups_used_symbol  \empty % ** start value
   \let\strc_itemgroups_margin_symbol\empty
   \let\strc_itemgroups_extra_symbol \empty
   %
   \global\letitemgroupparameter\c!maxwidth\!!zeropoint
   }

\setvalue{\??itemgroupfirst\v!intro       }{\settrue\c_strc_itemgroups_intro}
\setvalue{\??itemgroupfirst\v!continue    }{\settrue\c_strc_itemgroups_continue}
\setvalue{\??itemgroupfirst\v!random      }{\settrue\c_strc_itemgroups_randomize
                                            \settrue\c_strc_itemgroups_collecting}
\setvalue{\??itemgroupkeyword\v!horizontal}{\settrue\c_strc_itemgroups_horizontal
                                            \settrue\c_strc_itemgroups_collecting
                                            \settrue\c_strc_itemgroups_inline
                                            \settrue\c_strc_itemgroups_joined
                                            \strc_itemgroups_process_set_option_pack}

\def\strc_itemgroups_preset_stage_one#options%
  {\processcommacommand[#options]\strc_itemgroups_preset_stage_one_indeed}

% \installcommalistprocessorcommand \strc_itemgroups_preset_stage_one_list \strc_itemgroups_preset_stage_one_indeed
%
% \def\strc_itemgroups_preset_stage_one#options%
%   {\normalexpanded{\strc_itemgroups_preset_stage_one_list[#options]}}

\def\strc_itemgroups_preset_stage_one_indeed#option%
  {\ifcsname\??itemgroupfirst#option\endcsname
     \lastnamedcs
   \fi}

\ifdefined\dotagsetitemgroup \else \let\dotagsetitemgroup\relax             \fi
\ifdefined\dotagsetitem      \else \let\dotagsetitem     \gobbleoneargument \fi

\def\strc_itemgroups_tag_start_group
  {\dostarttaggedchained\t!itemgroup\currentparentitemgroup\??itemgroup
   \dotagsetitemgroup}

\def\strc_itemgroups_tag_stop_group
  {\dostoptagged}

\def\strc_itemgroups_before_command
  {\ifconditional\c_strc_itemgroups_nowhite
     \ifconditional\c_strc_itemgroups_before
       \ifcase\c_strc_itemgroups_nesting\or\itemgroupparameter\c!before\fi
     \else
       \nowhitespace
     \fi
   \else\ifconditional\c_strc_itemgroups_joined
     % \empty
   \else
     \itemgroupparameter\c!before
   \fi\fi}

\def\strc_itemgroups_after_command
  {\ifconditional\c_strc_itemgroups_nowhite
     \ifconditional\c_strc_itemgroups_after
       \ifcase\c_strc_itemgroups_nesting\or\itemgroupparameter\c!after\fi
     \else
       \nowhitespace
     \fi
   \else\ifconditional\c_strc_itemgroups_joined
     % \empty
   \else
     \itemgroupparameter\c!after
   \fi\fi}

\def\strc_itemgroups_between_command
  {\ifconditional\c_strc_itemgroups_nowhite
     \nowhitespace
   \else\ifconditional\c_strc_itemgroups_joined
     % \empty
   \else
     \itemgroupparameter\c!inbetween
   \fi\fi}

\def\strc_itemgroups_before_head_command
  {\ifconditional\c_strc_itemgroups_nowhite
     \nowhitespace
   \else\ifconditional\c_strc_itemgroups_joined
     % \empty
   \else
     \itemgroupparameter\c!beforehead
   \fi\fi}

\def\strc_itemgroups_after_head_command
  {\ifconditional\c_strc_itemgroups_nowhite
     \nowhitespace
   \else\ifconditional\c_strc_itemgroups_joined
     % \empty
   \else
     \itemgroupparameter\c!afterhead
   \fi\fi}

% compatible setup command:

\let\strc_itemgroups_normal_setup\setupitemgroup

\unexpanded\def\setupitemgroup
  {\doquadrupleempty\strc_itemgroups_setup}

\def\strc_itemgroups_setup[#category][#levels][#options][#settings]% category level|each options|settings settings|options
  {\edef\strc_itemgroups_setup_what{#levels}%
   \iffourthargument
     \ifx\strc_itemgroups_setup_what\v!each
       \strc_itemgroups_setup_each{#category}{#options}%
       \strc_itemgroups_setup_each{#category}{#settings}%
     \else
       \strc_itemgroups_setup_list{#levels}{#category}{#options}%
       \strc_itemgroups_setup_list{#levels}{#category}{#settings}%
     \fi
   \else\ifthirdargument
     \ifx\strc_itemgroups_setup_what\v!each
       \strc_itemgroups_setup_each{#category}{#options}%
     \else
       \strc_itemgroups_setup_list{#levels}{#category}{#options}%
     \fi
   \else\ifsecondargument
     \strc_itemgroups_setup_each{#category}{#levels}%
   \else
     \strc_itemgroups_normal_setup[#category]% == settings
   \fi\fi\fi}

% can be made a bit faster

% \def\strc_itemgroups_setup_each#category#whatever%
%   {\doifelseassignment{#whatever}
%      {\strc_itemgroups_normal_setup[#category][#whatever]}
%      {\strc_itemgroups_normal_setup[#category][\c!option={#whatever}]}}

\def\strc_itemgroups_setup_each#category#whatever%
  {\ifcondition\validassignment{#whatever}%
     \strc_itemgroups_normal_setup[#category][#whatever]%
   \else
     \strc_itemgroups_normal_setup[#category][\c!option={#whatever}]%
   \fi}

\def\strc_itemgroups_setup_list_level_a#category#whatever#level%
  {\strc_itemgroups_normal_setup[#category:#level][#whatever]}

\def\strc_itemgroups_setup_list_level_b#category#whatever#level%
  {\strc_itemgroups_normal_setup[#category:#level][\c!option={#whatever}]}

% \def\strc_itemgroups_setup_list#subcategories#category#whatever%
%   {\doifelseassignment{#whatever}
%      {\processcommalist[#subcategories]{\strc_itemgroups_setup_list_level_a{#category}{#whatever}}}
%      {\processcommalist[#subcategories]{\strc_itemgroups_setup_list_level_b{#category}{#whatever}}}}

\def\strc_itemgroups_setup_list#subcategories#category#whatever%
  {\ifcondition\validassignment{#whatever}%
     \processcommalist[#subcategories]{\strc_itemgroups_setup_list_level_a{#category}{#whatever}}%
   \else
     \processcommalist[#subcategories]{\strc_itemgroups_setup_list_level_b{#category}{#whatever}}%
   \fi}

\def\strc_itemgroups_increment_item_counter
  {\ifconditional\c_strc_itemgroups_sub \else
     \ifconditional\c_strc_itemgroups_symbol \else % \ifx\strc_itemgroups_extra_symbol\empty
       \strc_counters_increment_sub\v_strc_itemgroups_counter\currentitemlevel
     \fi
   \fi}

\unexpanded\def\strc_itemgroups_insert_item_counter
  {\ifconditional\c_strc_itemgroups_repeat
     \ifcase\c_strc_itemgroups_nesting
       % skip
     \or
       \strc_itemgroups_insert_item_counter_indeed % this could become an option
     \else
       \strc_itemgroups_insert_item_counter_indeed
     \fi
   \else
     \strc_itemgroups_insert_item_counter_indeed
   \fi}

\installcorenamespace{itemstopper}

\setvalue{\??itemstopper\v!yes    }{\itemgroupparameter\c!stopper}
\setvalue{\??itemstopper\v!display}{\ifconditional\c_strc_itemgroups_inline\else\itemgroupparameter\c!stopper\fi}
\setvalue{\??itemstopper\v!inline }{\ifconditional\c_strc_itemgroups_inline\itemgroupparameter\c!stopper\fi}

\def\strc_itemgroups_insert_item_counter_indeed % quite slow ... every time this setup .. but it
  {\begingroup                                  % can be optimized ... best move some to strc-num
   \setupcounter
     [\v_strc_itemgroups_counter]%
     [\c!prefix=\itemgroupparameter\c!prefix,
      \c!prefixstopper=\itemgroupparameter\c!prefixstopper,
      \c!prefixseparatorset=\itemgroupparameter\c!prefixseparatorset,
      \c!prefixconversion=\itemgroupparameter\c!prefixconversion,
      \c!prefixconversionset=\itemgroupparameter\c!prefixseparatorset,
      \c!prefixset=\itemgroupparameter\c!prefixset,
      \c!prefixsegments=\itemgroupparameter\c!prefixsegments,
      \c!prefixconnector=\itemgroupparameter\c!prefixconnector,
      \c!criterium=\itemgroupparameter\c!criterium,
      \c!numberorder=\ifconditional\c_strc_itemgroups_reverse\v!reverse\else\v!normal\fi,
      \c!numberstopper=\begincsname\??itemstopper\itemgroupparameter\c!placestopper\endcsname,
      \c!numberconversionset=\v_strc_itemgroups_counter,
      \c!numbersegments=\currentitemgroupsegments]%
   % there will be a fixedconversion key
  %\normalexpanded{\defineconversionset[\v_strc_itemgroups_counter][\currentitemgroupconversionset][\currentitemgroupsymbol]}%
   \normalexpanded{\strc_sets_define_conversion_set[\v_strc_itemgroups_counter][\currentitemgroupconversionset][\currentitemgroupsymbol]}%
   %
   \convertedcounter[\v_strc_itemgroups_counter]% [\number\currentitemlevel]%
   \strc_itemgroups_insert_reference
   \endgroup}

% needs testing (maybe it need to happen later)
%
% \appendtoks
%    \setupcounter
%      [\v_strc_itemgroups_counter]%
%      [\c!prefix=\itemgroupparameter\c!prefix,
%       \c!prefixstopper=\itemgroupparameter\c!prefixstopper,
%       \c!prefixseparatorset=\itemgroupparameter\c!prefixseparatorset,
%       \c!prefixconversion=\itemgroupparameter\c!prefixconversion,
%       \c!prefixconversionset=\itemgroupparameter\c!prefixseparatorset,
%       \c!prefixset=\itemgroupparameter\c!prefixset,
%       \c!prefixsegments=\itemgroupparameter\c!prefixsegments,
%       \c!prefixconnector=\itemgroupparameter\c!prefixconnector,
%       \c!criterium=\itemgroupparameter\c!criterium,
%       \c!numberorder=\ifconditional\c_strc_itemgroups_reverse\v!reverse\else\v!normal\fi,
%       \c!numberstopper=\expdoif{\itemgroupparameter\c!placestopper}\v!yes{\itemgroupparameter\c!stopper},
%       \c!numberconversionset=\v_strc_itemgroups_counter,
%       \c!numbersegments=\currentitemgroupsegments]%
% \to\itemgroupcommands
%
% \def\strc_itemgroups_insert_item_counter_indeed % quite slow ... every time this setup .. but it
%   {\begingroup                                  % can be optimized ... best move some to strc-num
%    % there will be a fixedconversion key
%   %\normalexpanded{\defineconversionset[\v_strc_itemgroups_counter][\currentitemgroupconversionset][\currentitemgroupsymbol]}%
%    \normalexpanded{\strc_sets_define_conversion_set[\v_strc_itemgroups_counter][\currentitemgroupconversionset][\currentitemgroupsymbol]}%
%    %
%    \convertedcounter[\v_strc_itemgroups_counter]% [\number\currentitemlevel]%
%    \strc_itemgroups_insert_reference
%    \endgroup}

\def\strc_itemgroups_set_symbol#symbol%
  {\edef\strc_itemgroups_tmp_symbol{#symbol}%
   \ifx\strc_itemgroups_tmp_symbol\empty \else
     \doifelsesymboldefined\strc_itemgroups_tmp_symbol
        \strc_itemgroups_set_symbol_symbol
        {\doifelseconversiondefined\strc_itemgroups_tmp_symbol
           \strc_itemgroups_set_symbol_conversion
           \donothing}%
   \fi}

\def\strc_itemgroups_set_symbol_symbol
  {\let\currentitemgroupsymbol\strc_itemgroups_tmp_symbol
   \strc_itemgroups_store_global_symbol\currentitemgroupsymbol
   \strc_itemgroups_store_local_symbol\v_strc_itemgroups_unknown_symbol
   \let\strc_itemgroups_used_symbol\strc_itemgroups_set_symbol_symbol_item
   \let\strc_itemgroups_asked_symbol\empty}

\def\strc_itemgroups_set_symbol_conversion
  {\let\currentitemgroupsymbol\strc_itemgroups_tmp_symbol
   \strc_itemgroups_store_global_symbol\currentitemgroupsymbol
   \strc_itemgroups_store_local_symbol\strc_itemgroups_insert_item_counter
   \let\strc_itemgroups_used_symbol\strc_itemgroups_set_symbol_conversion_item
   \let\strc_itemgroups_asked_symbol\empty}

\def\strc_itemgroups_set_symbol_symbol_item
  {\symbol[\currentitemgroupsymbol]}

\def\strc_itemgroups_set_symbol_conversion_item
  {\ifconditional\c_strc_itemgroups_text
     % maybe block stopper here, but one can as well clone an itemgroup then
     \itemgroupparameter\c!lefttext
     \strc_itemgroups_fetch_local_symbol
     \itemgroupparameter\c!righttext
   \else
     \itemgroupparameter\c!left
     \strc_itemgroups_fetch_local_symbol
     \itemgroupparameter\c!right
   \fi}

\def\strc_itemgroups_calculate_list_width#level%
  {\let\savedcurrentitemgroup\currentitemgroup
   \edef\currentitemgroup{\currentparentitemgroup:\number#level}%
   \ifdim\d_strc_itemgroups_max_width>\zeropoint
     \d_strc_itemgroups_list_width\d_strc_itemgroups_max_width
   \else\ifnum\itemgroupparameter\c!factor>\zerocount
     \d_strc_itemgroups_list_width\itemgroupparameter\c!step\relax
     \ifzeropt\d_strc_itemgroups_list_width \d_strc_itemgroups_list_width=.5em\fi
     \multiply\d_strc_itemgroups_list_width \itemgroupparameter\c!factor
     \advance\d_strc_itemgroups_list_width\itemgroupparameter\c!width\relax
   \else
     \d_strc_itemgroups_list_width\itemgroupparameter\c!width\relax
   \fi\fi
   \advance\d_strc_itemgroups_list_width\itemgroupparameter\c!distance\relax
   \let\currentitemgroup\savedcurrentitemgroup}

\unexpanded\def\startitemgroup
  {\dotripleempty\strc_itemgroups_start}

\def\strc_itemgroups_start[#category][#options][#settings]%
  {\begingroup % (1)
   \def\currentitemgroup{#category}% no nested mixing of itemgroups
   \let\currentparentitemgroup\currentitemgroup
   \global\advance\c_strc_itemgroups_nesting\plusone
   \def\currentitemlevel{\number\c_strc_itemgroups_nesting}%
   \normalexpanded{\chaintocurrentitemgroup{\currentparentitemgroup:\currentitemlevel}}%
   \edef\currentitemgroup{\currentparentitemgroup:\currentitemlevel}%
   %
   \ifthirdargument
     \strc_itemgroups_start_indeed[#options][#settings]%
   \else\ifsecondargument
     \ifcondition\validassignment{#options}%
       \strc_itemgroups_start_indeed[][#options]%
     \else
       \strc_itemgroups_start_indeed[#options][]%
     \fi
   \else
     \strc_itemgroups_start_indeed[][]%
   \fi\fi}

\def\strc_itemgroups_start_indeed[#options][#settings]%
  {\edef\itemgroupoptions{\itemgroupparameter\c!option}%
   \edef\itemgroupextraoptions{#options}%
   \ifx\itemgroupoptions\empty
     \let\itemgroupoptions\itemgroupextraoptions
   \else\ifx\itemgroupextraoptions\empty
     % ok
   \else
     \edef\itemgroupoptions{\itemgroupoptions,\itemgroupextraoptions}%
   \fi\fi
   \begingroup % (2)
   \the\itemgroupcommands
   \let\c_strc_itemgroups_text_saved\c_strc_itemgroups_text
   \strc_itemgroups_initialize_local
   \strc_itemgroups_preset_stage_one\itemgroupoptions
%
%    \ifhmode
%      \ifconditional\c_strc_itemgroups_auto_concat
%        \ifdim\lastskip=\d_strc_itemgroups_signal
%          \settrue\c_strc_itemgroups_concat
%        \fi
%      \fi
%      \ifconditional\c_strc_itemgroups_text_saved \else
%        \ifconditional\c_strc_itemgroups_text \else
%          \par
%        \fi
%      \fi
%    \fi
%
   \iftrialtypesetting
     \strc_counters_save\v_strc_itemgroups_counter
   \fi
   \c_strc_itemgroups_n_of_items\zerocount
   \strc_itemgroups_check_n_of_items
   \ifx\itemgroupoptions\empty
     \strc_itemgroups_setup_symbol_default
     \strc_itemgroups_reset_continue_state
     \setupcurrentitemgroup[#settings]%
   \else
     \strc_itemgroups_process_options\itemgroupoptions
     \setupcurrentitemgroup[#settings]%
     \ifconditional\c_strc_itemgroups_continue
       \strc_itemgroups_setup_symbol_continue
       \strc_itemgroups_fetch_continue_state
     \else
       \strc_itemgroups_setup_symbol_asked
       \strc_itemgroups_store_continue_state\itemgroupoptions{#settings}%
     \fi
   \fi
   %
   \ifhmode
     \ifconditional\c_strc_itemgroups_auto_concat
       \ifdim\lastskip=\d_strc_itemgroups_signal
         \settrue\c_strc_itemgroups_concat
       \fi
     \fi
     \ifconditional\c_strc_itemgroups_text_saved \else
       \ifconditional\c_strc_itemgroups_text \else
         \par
       \fi
     \fi
   \fi
   %
   \ifconditional\c_strc_itemgroups_pack
     \ifnum\currentnofitems>\itemgroupparameter\c!packcriterium\relax\else
       \setfalse\c_strc_itemgroups_pack
     \fi
   \fi
   %
   \ifnum\c_strc_itemgroups_nesting=\plusone % NIEUW
     \doadaptleftskip {\itemgroupparameter\c!margin}%
     \doadaptleftskip {\itemgroupparameter\c!leftmargin}%
     \doadaptrightskip{\itemgroupparameter\c!rightmargin}%
   \fi
   %
   \doadaptleftskip {\itemgroupparameter\c!leftmargindistance}%
   \doadaptrightskip{\itemgroupparameter\c!rightmargindistance}%
   %
   \usealignparameter\itemgroupparameter
   \edef\m_strc_itemgroups_indenting{\itemgroupparameter\c!indenting}%
   \ifnum\c_strc_itemgroups_nesting>\zerocount
     \settrue\c_strc_itemgroups_first
     \ifconditional\c_strc_itemgroups_continue \else
       \strc_counters_restart_sub\v_strc_itemgroups_counter\currentitemlevel{\numexpr\itemgroupparameter\c!start-\plusone\relax}%
     \fi
   \fi
   \ifx\strc_itemgroups_used_symbol\empty
     \strc_itemgroups_set_symbol\strc_itemgroups_asked_symbol % ** default value
     \ifx\strc_itemgroups_used_symbol\empty
       \let\currentitemgroupsymbol\currentitemlevel % ** fall back
     \fi
   \fi
   \ifconditional\c_strc_itemgroups_auto_intro\ifnum\prevgraf<\plusthree
     \settrue\c_strc_itemgroups_intro
   \fi\fi
   \ifconditional\c_strc_itemgroups_paragraph
     \ifnum\c_strc_itemgroups_nesting>\plusone
       \letitemgroupparameter\c!inbetween\empty
     \fi
   \fi
   \ifconditional\c_strc_itemgroups_pack
     \letitemgroupparameter\c!inbetween\empty
   \fi
   \ifconditional\c_strc_itemgroups_columns
     \ifinsidecolumns\else\ifcase\c_strc_itemgroups_column_depth
       \global\c_strc_itemgroups_column_depth\c_strc_itemgroups_nesting % global ?
       \strc_itemgroups_before_command
       \strc_itemgroups_tag_start_group
       \strc_itemgroups_start_columns
     \fi\fi
   \fi
   \ifconditional\c_strc_itemgroups_fitting
     \ifdim\d_strc_itemgroups_max_width>\zeropoint
       \letitemgroupparameter\c!width\d_strc_itemgroups_max_width
     \fi
   \fi
   \strc_itemgroups_calculate_list_width\c_strc_itemgroups_nesting
   \ifdim\d_strc_itemgroups_list_width>\zeropoint\relax
     \ifconditional\c_strc_itemgroups_inline\else
       \advance\leftskip\d_strc_itemgroups_list_width\relax
     \fi
   \fi
   \ifx\m_strc_itemgroups_repeat_start\empty
     \let\currentitemgroupconversionset \currentitemgroupsymbol
     \edef\currentitemgroupsegments     {\currentitemlevel}%
   \else
     \edef\currentitemgroupconversionset{\currentitemgroupconversionset,\currentitemgroupsymbol}%
     \edef\currentitemgroupsegments     {\m_strc_itemgroups_repeat_start:\currentitemlevel}%
   \fi
   \d_strc_itemgroups_asked_width\itemgroupparameter\c!width\relax
   \startcollectitems}

\let\startcollectitems\relax
\let\stopcollectitems \relax

\letvalue{\??itemgroupalign\v!flushleft }\relax
\letvalue{\??itemgroupalign\v!right     }\relax
\letvalue{\??itemgroupalign\v!flushright}\hfill
\letvalue{\??itemgroupalign\v!left      }\hfill
\letvalue{\??itemgroupalign\v!middle    }\hfil
\letvalue{\??itemgroupalign\v!center    }\hfil

\def\strc_itemgroups_left_sym_filler
  {\csname\??itemgroupalign\itemgroupparameter\c!symalign\endcsname}

% symbols + states

\def\strc_itemgroups_store_global_symbol#symbol%
  {\letgvalue{\??itemgroupglobal\currentitemlevel}#symbol}

\def\strc_itemgroups_store_local_symbol#symbol%
  {\letgvalue{\??itemgrouplocal\currentitemlevel}#symbol}

\def\strc_itemgroups_fetch_global_symbol
  {\csname\??itemgroupglobal\currentitemlevel\endcsname}

\def\strc_itemgroups_fetch_local_symbol
  {\csname\??itemgrouplocal\currentitemlevel\endcsname}

\def\strc_itemgroups_setup_symbol_default
  {\edef\strc_itemgroups_asked_symbol{\itemgroupparameter\c!symbol}%
   \strc_itemgroups_store_global_symbol\empty}

\def\strc_itemgroups_setup_symbol_continue
  {\ifcsname\??itemgroupglobal\currentitemlevel\endcsname
     \let\strc_itemgroups_asked_symbol\strc_itemgroups_fetch_global_symbol
   \else
     \let\strc_itemgroups_asked_symbol\currentitemlevel
   \fi}

\def\strc_itemgroups_setup_symbol_asked
   {\edef\strc_itemgroups_asked_symbol{\itemgroupparameter\c!symbol}}

\ifdefined\strc_itemgroups_start_columns

    % already defined in page-mix

\else

    % will be redefined in page-mix

    \ifdefined\startcolumns \else
        \unexpanded\def\startcolumns[#settings]{}
        \unexpanded\def\stopcolumns            {}
    \fi

    \def\strc_itemgroups_start_columns
      {\startcolumns
         [\c!n=\itemgroupparameter\c!n,
          \c!height=,
          \c!rule=\v!off,
          \c!balance=\v!yes,
          \c!align=\v!no]}

    \def\strc_itemgroups_stop_columns
      {\stopcolumns}

\fi

\unexpanded\def\stopitemgroup
  {\stopcollectitems
   \ifconditional\c_strc_itemgroups_text
     \removeunwantedspaces
     \space
     \ignorespaces
   \else
     \par
   \fi
   \strc_itemgroups_register_status
   \ifconditional\c_strc_itemgroups_first \else
     \dostoptagged
     \dostoptagged
   % \endgroup % (3)
   \fi
   \ifnum\c_strc_itemgroups_column_depth=\c_strc_itemgroups_nesting\relax
     \strc_itemgroups_stop_columns
     \global\c_strc_itemgroups_column_depth\zerocount % global ?
     \strc_itemgroups_tag_stop_group
     \strc_itemgroups_after_command
     \dontrechecknextindentation
   \else\ifnum\c_strc_itemgroups_nesting=\plusone
     \strc_itemgroups_insert_breakallow
     \strc_itemgroups_tag_stop_group
     \strc_itemgroups_after_command
     \useindentnextparameter\itemgroupparameter
   \else
     % nieuw, not yet nobreak handling
     \strc_itemgroups_tag_stop_group
     \ifcase\c_strc_itemgroups_spacing_mode
       \strc_itemgroups_after_command
     \or
       \strc_itemgroups_after_command
     \fi
     \dontrechecknextindentation
   \fi\fi
   % new test, needed in sidefloats (surfaced in volker's proceedings)
   \iftrialtypesetting
     \strc_counters_restore\v_strc_itemgroups_counter % could happen in LUA
   \fi
   \global\advance\c_strc_itemgroups_nesting\minusone
   \xdef\currentitemlevel{\number\c_strc_itemgroups_nesting}%
  %\ifconditional\c_strc_itemgroups_text
     \endgroup % (2)
     \endgroup % (1)
  %\else
  %  \endgroup % (2)
  %  \endgroup % (1)
  %  \par % hm, already done, and dangerous as \c_strc_itemgroups_text is already forgotten
  %\fi
   \dorechecknextindentation}

% The items.

\unexpanded\def\startitemgroupitem
  {\dosingleempty\strc_itemgroups_start_item}

\def\strc_itemgroups_start_item_first
  {\setfalse\c_strc_itemgroups_first
 % \begingroup % (3)
   \ifcase\c_strc_itemgroups_nesting
                                           % 0
   \or
     \strc_itemgroups_start_item_first_one % 1
   \else
     \strc_itemgroups_start_item_first_two % 2+
   \fi}

\def\strc_itemgroups_start_item_first_one
  {\ifcase\c_strc_itemgroups_column_depth
     \ifconditional\c_strc_itemgroups_intro\strc_itemgroups_insert_breakno\fi
     \strc_itemgroups_before_command
     \strc_itemgroups_tag_start_group
     \ifconditional\c_strc_itemgroups_intro\strc_itemgroups_insert_breakno\fi
   \fi}

\def\strc_itemgroups_start_item_first_two
  {\ifconditional\c_strc_itemgroups_paragraph\else
     \edef\previtemlevel{\the\numexpr\c_strc_itemgroups_nesting-\plusone}%
     \ifcase\c_strc_itemgroups_spacing_mode
       \strc_itemgroups_before_command
     \or
       \doifelsenothing\strc_itemgroups_before_command % should possibly expand to empty
         {\nameditemgroupparameter{\currentparentitemgroup:\previtemlevel}\c!inbetween}%
         \strc_itemgroups_before_command
     \else
       \nameditemgroupparameter{\currentparentitemgroup:\previtemlevel}\c!inbetween
     \fi
     \strc_itemgroups_tag_start_group
   \fi}

\def\strc_itemgroups_start_item_next
  {\dostoptagged % ok? what do we stop here?
   \dostoptagged % ok? what do we stop here?
   \ifconditional\c_strc_itemgroups_text
     \ifhmode
       % WS: make the distance between items customizable, think about better default values -> see itemize-1.tex
       \strc_itemgroups_set_text_item_distance% HH: moved out and made configurable (sort of)
       \removeunwantedspaces
       \hskip\m_strc_itemgroups_text_distance\relax
     \fi
   \else
     \strc_itemgroups_between_command
   \fi}

% c_strc_itemgroups_concat:
%
% the problem is that we use leftskip so concat cannot reliable take the height into
% account; it's .. rather tricky when white space in there anyway (due to \par) .. so
% we rely on a special blank method
%
% \startitemize[n]
%     \item bla
%     \item \startitemize[a]
%         \item bla $\displaystyle\int^{x^{y^4}}$ \item bla
%     \stopitemize
% \stopitemize

\unexpanded\def\strc_itemgroups_start_item[#reference]% we can reuse more
  {\def\currentitemreference{#reference}%
   \ifconditional\c_strc_itemgroups_text
     % begin of item
   \else
     \par
   \fi
   \ifconditional\c_strc_itemgroups_concat
     \strc_itemgroups_insert_breakno
   \fi
   \strc_itemgroups_increment_item_counter
   \ifconditional\c_strc_itemgroups_first
     \strc_itemgroups_start_item_first
   \else
     \strc_itemgroups_start_item_next
   \fi
   \ifconditional\c_strc_itemgroups_concat
     \spac_overlay_lines % see spac-ver.mkvi ... a typical potential problem
     \setfalse\c_strc_itemgroups_concat
   \fi
   \dostarttagged\t!item\empty
  % \dotagsetitem\empty
   \dostarttagged\t!itemtag\empty
   \strc_itemgroups_insert_item
   \dostoptagged
   \ifconditional\c_strc_itemgroups_pack
     \setupwhitespace[\v!none]%
   \fi
   \itemgroupparameter\c!inner % will become obsolete (better use setups)
   \strc_itemgroups_margin_symbol
   \let\strc_itemgroups_margin_symbol\relax
   \dostarttagged\t!itemcontent\empty
   \begstrut % \strut
   \nobreak                            % else problems with intext items
   \seteffectivehsize % NEW !
   \hskip\d_strc_itemgroups_signal     % concat
   \itemgroupparameter\c!command}

\unexpanded\def\stopitemgroupitem
  {\ifhmode
     \endstrut % new per 2017-12-15
   \fi
   \ifconditional\c_strc_itemgroups_text
     % nothing
   \else
     \endgraf
   \fi}
\unexpanded\def\startitemgrouphead
  {\dosingleempty\strc_itemgroups_start_head}

\unexpanded\def\strc_itemgroups_start_head[#reference]%
  {\ifconditional\c_strc_itemgroups_first \else
     \strc_itemgroups_insert_breakallow
   \fi
   \ifconditional\c_strc_itemgroups_pack \else
     \strc_itemgroups_before_head_command
   \fi
   \ifconditional\c_strc_itemgroups_first
     \ifconditional\c_strc_itemgroups_intro \else
       \ifcase\c_strc_itemgroups_nesting
         \strc_itemgroups_insert_breakallow
       \fi
     \fi
   \fi
   \strc_itemgroups_start_item[#reference]%
   \pickupgroupedcommand
     \strc_itemgroups_start_head_indeed
     \strc_itemgroups_stop_head_indeed
     \strc_itemgroups_head_body_indeed}

\unexpanded\def\stopitemgrouphead
  {\dostoptagged
   \stopitemgroupitem}

\unexpanded\def\strc_itemgroups_start_head_indeed
  {\settrue\c_strc_itemgroups_head
   \dotagsetitem\s!head% % weird place
   \dostarttagged\t!itemhead\empty
   \useitemgroupstyleandcolor\c!headstyle\c!headcolor\ignorespaces}

\unexpanded\def\strc_itemgroups_stop_head_indeed
  {\removeunwantedspaces
   \dostoptagged
   \ifconditional\c_strc_itemgroups_inline_head
       \space
       \ignorespaces
   \else
     \ifconditional\c_strc_itemgroups_text
       \space
       \ignorespaces
     \else
       \par
     \fi
     \strc_itemgroups_insert_breakno
     \ifconditional\c_strc_itemgroups_pack\else\strc_itemgroups_after_head_command\fi
     \strc_itemgroups_insert_breakno
  \fi}

\unexpanded\def\strc_itemgroups_head_body_indeed
  {\dostarttagged\t!itembody\empty
   \noindentation
   \ignorespaces}

% Simple commands.

\unexpanded\def\strc_itemgroups_start_do_item
  {\startitemgroupitem}

\unexpanded\def\strc_itemgroups_start_no_item
  {\let\currentitemreference\empty
   \strc_itemgroups_increment_item_counter
  %\advance\c_strc_itemgroups_n_of_items\plusone
   \setbox\b_strc_itemgroups\emptyhbox
   \strc_itemgroups_check_for_repeated
   \ignorespaces}

\unexpanded\def\strc_itemgroups_start_button[#destination]%
  {\edef\m_strc_itemgroups_destination{#destination}%
   \startitemgroupitem}

\unexpanded\def\strc_itemgroups_start_symbol#text%
  {\def\strc_itemgroups_extra_symbol{#text}%
   \settrue\c_strc_itemgroups_symbol
   \startitemgroupitem
   \dotagsetitem\s!symbol}

\unexpanded\def\strc_itemgroups_start_dummy
  {\strc_itemgroups_start_symbol
  %\strut\strut} % two ?
   \begstrut}

\unexpanded\def\strc_itemgroups_start_subitem
  {\settrue\c_strc_itemgroups_sub
   \startitemgroupitem
   \dotagsetitem\s!sub}

\unexpanded\def\strc_itemgroups_start_edge#text%
  {\strc_itemgroups_start_symbol
     {\strc_itemgroups_calculate_list_width\c_strc_itemgroups_nesting
      \dostarttagged\t!ignore\empty % for the moment, maybe an attribute
      \hbox to \d_strc_itemgroups_list_width
        {#text\hskip\itemgroupparameter\c!distance}%
      \dostoptagged}}

\unexpanded\def\strc_itemgroups_start_margin#text%
  {\def\strc_itemgroups_margin_symbol % brrr
     {\dostarttagged\t!ignore\empty % for the moment, maybe an attribute
      \llap
        {\begingroup
         \useitemgroupstyleandcolor\c!marstyle\c!marcolor
         #text% keep em/ex local
         \endgroup
         \hskip\dimexpr\leftskip+\leftmargindistance\relax}%
      \dostoptagged}%
   \startitemgroupitem
   \dotagsetitem\s!margin}

\unexpanded\def\strc_itemgroups_start_text#text%
  {\def\strc_itemgroups_extra_symbol{#text}%
   \settrue\c_strc_itemgroups_symbol
   \settrue\c_strc_itemgroups_txt
   \startitemgroupitem}

% \unexpanded\def\strc_itemgroups_start_head
%   {\settrue\c_strc_itemgroups_head
%    \startitemgrouphead}

\unexpanded\def\strc_itemgroups_start_items
  {\dosingleempty\strc_itemgroups_start_items_indeed}

\unexpanded\def\strc_itemgroups_start_items_indeed[#whatever]% something got lost
  {\strc_itemgroups_start_edge
     {\dorecurse{0\itemgroupparameter\c!items}{\strc_itemgroups_used_symbol\hss}%
      \unskip}}

% \unexpanded\def\startspecialitemgroupitem[#name]%
%   {\csname\??itemgroupstart\ifcsname\??itemgroupstart#name\endcsname#name\else\v!item\fi\endcsname}

\unexpanded\def\startspecialitemgroupitem[#name]%
  {\ifcsname\??itemgroupstart#name\endcsname
      \expandafter\lastnamedcs
    \else
      \expandafter\strc_itemgroups_start_do_item
    \fi}

\unexpanded\def\stopspecialitemgroupitem
  {\stopitemgroupitem}

\letvalue{\??itemgroupstart\v!item}\strc_itemgroups_start_do_item
\letvalue{\??itemgroupstart\v!sub }\strc_itemgroups_start_subitem
\letvalue{\??itemgroupstart\v!sym }\strc_itemgroups_start_symbol
\letvalue{\??itemgroupstart\v!ran }\strc_itemgroups_start_edge
\letvalue{\??itemgroupstart\v!its }\strc_itemgroups_start_items
\letvalue{\??itemgroupstart\v!mar }\strc_itemgroups_start_margin
\letvalue{\??itemgroupstart\v!txt }\strc_itemgroups_start_text

\def\optimizelistitemsbreak
  {\ifcase\c_strc_itemgroups_column_depth \ifconditional\c_strc_itemgroups_optimize
     \ifcase \c_strc_itemgroups_max_items \else
       \ifnum\c_strc_itemgroups_max_items=\plusthree
         \ifnum\c_strc_itemgroups_n_of_items>\plusone
           \strc_itemgroups_insert_nobreak
         \fi
       \else\ifnum\c_strc_itemgroups_max_items>\plusthree
         \ifnum\c_strc_itemgroups_n_of_items=\plustwo
           \ifconditional\c_strc_itemgroups_intro
             \strc_itemgroups_insert_breakno
           \else
             \strc_itemgroups_insert_nobreak
           \fi
         \else\ifnum\c_strc_itemgroups_max_items=\c_strc_itemgroups_n_of_items\relax
           \strc_itemgroups_insert_nobreak
         \else\ifnum\c_strc_itemgroups_n_of_items>\plustwo
           \strc_itemgroups_insert_break
         \else
           \ifconditional\c_strc_itemgroups_intro\else\strc_itemgroups_insert_break\fi
         \fi\fi\fi
       \fi\fi
     \fi
   \fi\fi}

\def\strc_itemgroups_handle_text_item
  {\scratchdimen\wd\b_strc_itemgroups
   \advance \scratchdimen \itemgroupparameter\c!distance\relax
   \ifdim\scratchdimen>\d_strc_itemgroups_list_width
     \advance\scratchdimen -\d_strc_itemgroups_list_width
   \else
     \scratchdimen\zeropoint
   \fi
   \llap{\hbox to \d_strc_itemgroups_list_width{\ifconditional\c_strc_itemgroups_sub\llap{+\enspace}\fi\box\b_strc_itemgroups\hss}}% was: \hfill
   \hskip\scratchdimen}

\def\strc_itemgroups_handle_lapped_item_positive
  {\llap
     {\dontcomplain
      \hbox to \d_strc_itemgroups_list_width
        {\ifconditional\c_strc_itemgroups_sub
           \dostarttagged\t!ignore\empty
           \llap{+\enspace}%
           \dostoptagged
         \fi
         \strc_itemgroups_left_sym_filler
         \box\b_strc_itemgroups % can already have a forced widt, only factor handled here
         \hfil
         \hskip\itemgroupparameter\c!distance}}}

\def\strc_itemgroups_handle_lapped_item_negative
  {\llap
     {\ifconditional\c_strc_itemgroups_sub
        \dostarttagged\t!ignore\empty
        \llap{+\enspace}%
        \dostoptagged
      \fi
      \box\b_strc_itemgroups
      \hskip\leftmargindistance}}

\def\strc_itemgroups_handle_groups_text_item
  {\hbox
     {\ifconditional\c_strc_itemgroups_sub
        \dostarttagged\t!ignore\empty
        +\enspace
        \dostoptagged
      \fi
      \box\b_strc_itemgroups
      \hskip\interwordspace}%
   \nobreak}

\def\strc_itemgroups_handle_groups_inline_item
  {\hbox to \d_strc_itemgroups_list_width
     {\ifconditional\c_strc_itemgroups_sub
        \dostarttagged\t!ignore\empty
        \llap{+\enspace}%
        \dostoptagged
      \fi
      \box\b_strc_itemgroups
      \hss}} % was: \hfill

\unexpanded\def\strc_itemgroups_start_head_sym#text%
  {\def\strc_itemgroups_extra_symbol{#text}%
   \settrue\c_strc_itemgroups_symbol
   \settrue\c_strc_itemgroups_head
   \strc_itemgroups_start_head}

\def\strc_itemgroups_make_symbol_box
  {\setbox\b_strc_itemgroups\autodirhbox
     {\ifconditional\c_strc_itemgroups_head
        \ifconditional\c_strc_itemgroups_symbol
          \strc_itemgroups_insert_extra_reference
          \useitemgroupstyleandcolor\c!symstyle\c!symcolor
          \strc_itemgroups_extra_symbol
        \else
          \useitemgroupstyleandcolor\c!headstyle\c!headcolor
          \strc_itemgroups_used_symbol
        \fi
      \else
        \ifconditional\c_strc_itemgroups_symbol
          \strc_itemgroups_insert_extra_reference
          \useitemgroupstyleandcolor\c!symstyle\c!symcolor
          \strc_itemgroups_extra_symbol
        \else
          \useitemgroupstyleandcolor\c!style\c!color
          \strc_itemgroups_used_symbol
        \fi
      \fi}%
   \let\strc_itemgroups_extra_symbol\empty
   \setfalse\c_strc_itemgroups_symbol}

\def\strc_itemgroups_make_fitting_box
  {\ifdim\wd\b_strc_itemgroups>\itemgroupparameter\c!maxwidth\relax
     \normalexpanded{\global\setitemgroupparameter{\c!maxwidth}{\the\wd\b_strc_itemgroups}}%
   \fi
   \ifdim\d_strc_itemgroups_max_width>\zeropoint
     \setbox\b_strc_itemgroups\simplealignedbox
       {\dimexpr\d_strc_itemgroups_max_width+\itemgroupparameter\c!distance\relax}
       {\itemgroupparameter\c!itemalign}
       {\box\b_strc_itemgroups\hskip\itemgroupparameter\c!distance}%
   \fi}

\def\strc_itemgroups_make_aligned_box
  {\doifsomething{\itemgroupparameter\c!itemalign}
     {\setbox\b_strc_itemgroups\simplealignedbox
        {\dimexpr\d_strc_itemgroups_asked_width+\itemgroupparameter\c!distance\relax}
        {\itemgroupparameter\c!itemalign}
        {\box\b_strc_itemgroups\hskip\itemgroupparameter\c!distance}}}

\def\strc_itemgroups_make_destination_box
  {\iftrialtypesetting \else \ifx\m_strc_itemgroups_destination\empty \else
     \setbox\b_strc_itemgroups\hbox{\directgotobox{\box\b_strc_itemgroups}[\m_strc_itemgroups_destination]}%
   \fi\fi}

\def\strc_itemgroups_check_indenting
  {\setfalse\c_strc_itemgroups_indented_first
   \ifx\m_strc_itemgroups_indenting\empty \else
     \normalexpanded{\setupindenting[\v!reset,\v!yes,\m_strc_itemgroups_indenting]}%
     \ifconditional\c_spac_indentation_indent_first % better is to have a mode
       \doifnot{\itemgroupparameter\c!alignsymbol}\v!yes
         {\settrue\c_strc_itemgroups_indented_first}%
     \fi
   \fi}

\def\strc_itemgroups_check_for_repeated
  {\ifconditional\c_strc_itemgroups_repeat
      \ifx\m_strc_itemgroups_repeat_start\empty
        \edef\m_strc_itemgroups_repeat_start{\currentitemlevel}%
      \fi
   \else
      \let\m_strc_itemgroups_repeat_start\empty
   \fi}

\def\strc_itemgroups_insert_item
  {\ifconditional\c_strc_itemgroups_text % again?
    % begin of item
   \else
     \par % done twice?
   \fi
   \advance\c_strc_itemgroups_n_of_items\plusone
   \optimizelistitemsbreak
   \strc_itemgroups_check_indenting
   \dontleavehmode
   \ifconditional\c_strc_itemgroups_indented_first
     \hskip-\parindent
   \fi
   \strc_itemgroups_make_symbol_box
   \strc_itemgroups_make_destination_box
   \ifconditional\c_strc_itemgroups_fitting
     \strc_itemgroups_make_fitting_box
   \else\ifdim\d_strc_itemgroups_asked_width>\zeropoint
     \strc_itemgroups_make_aligned_box
   \fi\fi
   \let\m_strc_itemgroups_destination\empty
   \ht\b_strc_itemgroups\strutheight % just in case a symbols is not yet available in
   \dp\b_strc_itemgroups\strutdepth  % the current run (more a mkii mp side artifact)
   \strc_itemgroups_check_for_repeated
   \ifdim\d_strc_itemgroups_asked_width<\zeropoint\relax
     \strc_itemgroups_handle_lapped_item_negative
   \else
     \ifzeropt\d_strc_itemgroups_asked_width
       \strc_itemgroups_calculate_list_width\plusone
     \else
       \strc_itemgroups_calculate_list_width\c_strc_itemgroups_nesting
     \fi
     \ifconditional\c_strc_itemgroups_text
       \strc_itemgroups_handle_groups_text_item
     \else\ifconditional\c_strc_itemgroups_inline
       \strc_itemgroups_handle_groups_inline_item
     \else\ifconditional\c_strc_itemgroups_txt
       \strc_itemgroups_handle_text_item
     \else
       \strc_itemgroups_handle_lapped_item_positive
     \fi\fi\fi
   \fi
   \setfalse\c_strc_itemgroups_head
   \setfalse\c_strc_itemgroups_sub
   \ifconditional\c_strc_itemgroups_indented_first
     \hskip\parindent
   \fi
   \ignorespaces}

\def\strc_itemgroups_start_item_nop
  {\let\currentitemreference\empty
   \strc_itemgroups_increment_item_counter
   \advance\c_strc_itemgroups_n_of_items\plusone
   \setbox\b_strc_itemgroups\hbox
     {\useitemgroupstyleandcolor\c!style\c!color
      \strc_itemgroups_used_symbol}%
   \strc_itemgroups_check_for_repeated
   \ignorespaces}

\setvalue{\??itemgroupdistance\v!none}%
  {\let\m_strc_itemgroups_text_distance\zeropoint}

\setvalue{\??itemgroupdistance\v!space}%
  {\def\m_strc_itemgroups_text_distance{\interwordspace\s!plus\interwordstretch\s!minus\interwordshrink}}

\setvalue\??itemgroupdistance % catches empty value
  {\let\m_strc_itemgroups_text_distance\zeropoint}

\unexpanded\def\strc_itemgroups_set_text_item_distance
  {\edef\m_strc_itemgroups_text_distance{\itemgroupparameter\c!textdistance}%
   \ifx\m_strc_itemgroups_text_distance\empty
     %
   \else\ifcsname\??itemgroupdistance\m_strc_itemgroups_text_distance\endcsname
     \lastnamedcs
   \else
     \strc_itemgroups_set_text_item_distance_indeed
   \fi\fi}

\def\strc_itemgroups_set_text_item_distance_indeed
  {\assignvalue
     \m_strc_itemgroups_text_distance
     \m_strc_itemgroups_text_distance
     {.5\interwordspace\s!plus.5\emwidth}%
     {\interwordspace  \s!plus  \emwidth}%
     {\emwidth         \s!plus  \interwordstretch\s!minus\interwordshrink}}

% \unexpanded\def\strc_itemgroups_default_command
%   {\EveryPar{\ignorespaces}% needed ?
%    \ignorespaces}

\unexpanded\def\strc_itemgroups_default_command
  {\ignorespaces}

%D Special case:

\unexpanded\def\strc_itemgroups_head#text\par
  {\startitemgrouphead{#text}}

%D The local commands:

\appendtoks
    \let\item            \strc_itemgroups_start_do_item
    \let\sub             \strc_itemgroups_start_subitem
    \let\sym             \strc_itemgroups_start_symbol
    \let\ran             \strc_itemgroups_start_edge
    \let\its             \strc_itemgroups_start_items
    \let\mar             \strc_itemgroups_start_margin
    \let\noitem          \strc_itemgroups_start_no_item
    \let\itm             \strc_itemgroups_start_do_item
    \let\but             \strc_itemgroups_start_button
    \let\nop             \strc_itemgroups_start_dummy
    \let\txt             \strc_itemgroups_start_text
    \let\head            \strc_itemgroups_head
    \let\headsym         \strc_itemgroups_start_head_sym
    \let\startitem       \startitemgroupitem
    \let\stopitem        \stopitemgroupitem
    \let\starthead       \startitemgrouphead
    \let\stophead        \stopitemgrouphead
    \let\startspecialitem\startspecialitemgroupitem
    \let\stopspecialitem \stopspecialitemgroupitem
\to \itemgroupcommands

\ifx\currentinterface \s!english \else

    \def\next#1#2{\ifcsname#1\endcsname\else\let\csname#1\endcsname#2\fi}

    \etoksapp\itemgroupcommands{%
        \next{\v!item        }\strc_itemgroups_start_do_item
        \next{\v!sub         }\strc_itemgroups_start_subitem
        \next{\v!sym         }\strc_itemgroups_start_symbol
        \next{\v!ran         }\strc_itemgroups_start_edge
        \next{\v!head        }\strc_itemgroups_head
        \next{\v!its         }\strc_itemgroups_start_items
        \next{\v!mar         }\strc_itemgroups_start_margin
        \next{\v!txt         }\strc_itemgroups_start_text
        \next{\e!start\v!item}\startitemgroupitem
        \next{\e!stop \v!item}\stopitemgroupitem
        \next{\e!start\v!head}\startitemgrouphead
        \next{\e!stop \v!head}\stopitemgrouphead
    }

\fi

\relaxvalueifundefined \v!item
\relaxvalueifundefined \v!sub
\relaxvalueifundefined \v!sym
\relaxvalueifundefined \v!ran
\relaxvalueifundefined \v!head
\relaxvalueifundefined \v!its
\relaxvalueifundefined \v!mar
\relaxvalueifundefined \v!txt
\relaxvalueifundefined {\e!start\v!item}
\relaxvalueifundefined {\e!stop \v!item}
\relaxvalueifundefined {\e!start\v!head}
\relaxvalueifundefined {\e!stop \v!head}

%D A nice example of a plugin:
%D
%D \startbuffer
%D \startitemize[a,random,packed]
%D \startitem first  \stopitem \startitem second \stopitem
%D \startitem third  \stopitem \startitem fourth \stopitem
%D \stopitemize
%D
%D \startitemize[a,random,packed]
%D \startitem first  \stopitem \startitem second \stopitem
%D \startitem third  \stopitem \startitem fourth \stopitem
%D \stopitemize
%D
%D \startitemize[a,packed]
%D \startitem first  \stopitem \startitem second \stopitem
%D \startitem third  \stopitem \startitem fourth \stopitem
%D \stopitemize
%D \stopbuffer
%D
%D \typebuffer \getbuffer

% better collectitems als conditional and a real plugin mechanism (some day)

\newcount\c_strc_itemgroups_collected_stored
\newcount\c_strc_itemgroups_collected_done
\newcount\c_strc_itemgroups_collected_current

% \expandafter\def\expandafter\strc_itemgroups_collected_store\expandafter#\expandafter1\csname\e!stop\v!item\endcsname % use grabuntil
%   {\advance\c_strc_itemgroups_collected_stored\plusone
%    \setvalue{\??itemgroupstack\number\c_strc_itemgroups_collected_stored}{\startitemgroupitem#1\stopitemgroupitem}}

\let\strc_itemgroups_collected_store\relax

\normalexpanded{\def\strc_itemgroups_collected_store#1\csname\e!stop\v!item\endcsname}%
  {\advance\c_strc_itemgroups_collected_stored\plusone
   \setvalue{\??itemgroupstack\number\c_strc_itemgroups_collected_stored}{\startitemgroupitem#1\stopitemgroupitem}}

\def\strc_itemgroups_collected_flush_randomize
  {\collecteditemgroupitem}

\def\strc_itemgroups_collected_flush_horizontal
  {\begingroup
   \scratchcounter\itemgroupparameter\c!n\relax
   \ifnum\c_strc_itemgroups_collected_done>\plusone
     \ifcase\modulonumber\scratchcounter\c_strc_itemgroups_collected_done\relax
       % compensate for rounding errors
       \hfill % \hskip\zeropoint plus \scaledpoint minus \scaledpoint
       \allowbreak
     \fi
   \fi
   \noindent % no \dontleavehmode
   \hbox to \dimexpr\availablehsize/\scratchcounter\relax{\collecteditemgroupitem\hss}%
   \endgroup}

% \def\strc_itemgroups_collected_flush_indeed
%   {\collecteditemgroupitem
%    \iftrialtypesetting
%      \undefinevalue{\??itemgroupstack\number\c_strc_itemgroups_collected_current}%
%    \fi}

\def\strc_itemgroups_collected_flush_indeed
  {\collecteditemgroupitem
   \undefinevalue{\??itemgroupstack\number\c_strc_itemgroups_collected_current}}

\def\strc_itemgroups_collected_flush
  {\ifconditional\c_strc_itemgroups_randomize
     \getrandomcount\c_strc_itemgroups_collected_current\plusone\c_strc_itemgroups_collected_stored
   \else
     \advance\c_strc_itemgroups_collected_current\plusone
   \fi
   \ifcsname\??itemgroupstack\number\c_strc_itemgroups_collected_current\endcsname
     \edef\collecteditemgroupitem{\lastnamedcs}%
     \ifconditional\c_strc_itemgroups_horizontal
       \strc_itemgroups_collected_flush_horizontal
     \else
       \strc_itemgroups_collected_flush_indeed
     \fi
     \advance\c_strc_itemgroups_collected_done\plusone
   \fi
   \ifnum\c_strc_itemgroups_collected_done<\c_strc_itemgroups_collected_stored
     \expandafter\strc_itemgroups_collected_flush
   \fi}

\unexpanded\def\stopcollectitems
  {\ifconditional\c_strc_itemgroups_collecting
     \c_strc_itemgroups_collected_done   \zerocount
     \c_strc_itemgroups_collected_current\zerocount
     \ifnum\c_strc_itemgroups_collected_stored>\zerocount
       \ifconditional\c_strc_itemgroups_horizontal
         \strc_itemgroups_before_command
         \setfalse\c_strc_itemgroups_first
         \strc_itemgroups_collected_flush
        %\strc_itemgroups_after_command % triggered elsewhere
       \else
         \strc_itemgroups_collected_flush
       \fi
     \fi
   \fi}

\unexpanded\def\startcollectitems
  {\ifconditional\c_strc_itemgroups_collecting
     \c_strc_itemgroups_collected_stored\zerocount
     \letvalue{\e!start\v!item}\strc_itemgroups_collected_store
   \fi}

%D Left-overs:

\unexpanded\def\item
  {\strc_itemgroups_item_alone}

\def\strc_itemgroups_item_alone[#category]#text\par
  {\doifelsesomething{#category}{\startitemgroup[#category]}{\startitemgroup[\v!itemize]}%
   \startitem#text\stopitem
   \stopitemgroup}

\unexpanded\def\head
  {\strc_itemgroups_head_alone}

\def\strc_itemgroups_head_alone[#category]#head\par#body\par
  {\doifelsesomething{#category}{\startitemgroup[#category]}{\startitemgroup[\v!itemize]}%
   \starthead{#head}#body\stophead
   \stopitemgroup}

\setuvalue{\e!start\v!item}%
  {\startitemgroup[\v!itemize]%
   \startitemgroupitem
   \setuvalue{\e!stop\v!item}{\stopitemgroupitem\stopitemgroup}}

% \def\sym#text%
%   {\noindent
%    \begingroup
%    \setbox\scratchbox\hbox{\settrialtypesetting#text}%
%    \setbox\scratchbox\hbox\ifdim\wd\scratchbox<1em to 1.5\else spread 1\fi em{#text\hfil}%
%    \normalexpanded{\box\scratchbox\endgroup\hangindent\the\wd\scratchbox}%
%    \ignorespaces}

%D End of plugin.

%D Something for tables:

\unexpanded\def\itemtag
  {\dosingleempty\strc_itemgroups_item_tag}

\unexpanded\def\strc_itemgroups_item_tag[#reference]% we can reuse more
  {\def\currentitemreference{#reference}%
   \iftrialtypesetting
     \strc_counters_save\v_strc_itemgroups_counter
     \strc_itemgroups_increment_item_counter
     \strc_itemgroups_insert_item_tag_indeed
     \strc_counters_restore\v_strc_itemgroups_counter
   \else
     \strc_itemgroups_increment_item_counter
     \strc_itemgroups_insert_item_tag_indeed
   \fi}

\def\strc_itemgroups_insert_item_tag_indeed
  {\letitemgroupparameter\c!distance\zeropoint
   %letitemgroupparameter\c!width\zeropoint
   \strc_itemgroups_make_symbol_box
   \strc_itemgroups_make_destination_box
   \let\m_strc_itemgroups_destination\empty
   \ht\b_strc_itemgroups\strutheight
   \dp\b_strc_itemgroups\strutdepth
   \box\b_strc_itemgroups
   \ignorespaces}

%D Done again.

\setupitemgroup
  [\c!margin=\zeropoint,
   \c!leftmargin=\zeropoint,
   \c!rightmargin=\zeropoint,
   \c!leftmargindistance=\zeropoint,
   \c!rightmargindistance=\zeropoint,
   \c!indentnext=\v!yes,
   \c!width=1.5\emwidth,
   \c!factor=0,
  %\c!distance=.5em, % is now:
   \c!step=.5\emwidth, % deals with broad
   \c!distance=\zeropoint,
  %\c!align=\v!normal, % definitely not \v!normal !
  %\c!symalign=,
  %\c!color=,
  %\c!indenting=, % untouched if empty
  %\c!style=,
   \c!marstyle=\v!type,
  %\c!symstyle=,
  %\c!headstyle=,
  %\c!marcolor=,
  %\c!symcolor=,
  %\c!headcolor=,
  %\c!beforehead=,
   \c!symcolor=\itemgroupparameter\c!color, % new per 2012.01.17
   \c!symstyle=\itemgroupparameter\c!style, % new per 2012.01.17
   \c!afterhead=\blank,
   \c!before=\blank,
   \c!inbetween=\blank,
   \c!after=\blank,
  %\c!stopper=.,
   \c!placestopper=\v!yes,
   \c!stopper=.,
  %\c!inner=,
   \c!n=2,
   \c!items=4,
   \c!levels=10,
   \c!lefttext=(,
   \c!righttext=),
   \c!start=1,
   \c!packcriterium=\zerocount,
   \c!criterium=\v!all, % permits 0 and negative numbers
  %\c!option=,
   \c!textdistance=\v!space, % none big medium small <dimension>
   \c!command=\strc_itemgroups_default_command,
   \c!indenting=\v!next,
  %\c!alignsymbol=v!no,
   \c!symbol=\currentitemlevel,
   \c!prefix=\v!no,
  %\c!prefixstopper=.,
  %\c!prefixseparatorset=,
  %\c!prefixconversion=,
  %\c!prefixconversionset=,
  %\c!prefixset=,
  %\c!prefixsegments=1:100,
   \c!prefixconnector=.,
   \c!numberseparatorset=,
   \c!numberconversionset=,
   \c!numberstopper=.,
   \c!numbersegments=1]

\defineitemgroup
  [\v!itemize]

%D This is really ugly I should get rid of the global mess, whuch is a side
%D effect of the simple \type {\item} interface that we're stuck with for
%D compatibility reasons. See footnotes for usage. It's probablynot robust
%D for mixed itemgroups so in the end I need to get rid of the globals. One
%D problem is that counters are set.

\defineitemgroup
  [\v!itemize:\v!note]

\def\strc_itemgroups_push
  {\edef\strc_itemgroups_pop
     {\xdef\noexpand\currentitemlevel{\currentitemlevel}%
      \global\c_strc_itemgroups_nesting     \the\c_strc_itemgroups_nesting     \relax
      \global\c_strc_itemgroups_column_depth\the\c_strc_itemgroups_column_depth\relax}%
   \global\c_strc_itemgroups_column_depth\zerocount
   \global\c_strc_itemgroups_nesting     \zerocount
   \glet\currentitemlevel\!!zerocount
   \unexpanded\def\startitemize{\startitemgroup[\v!itemize:\v!note]}%
   \unexpanded\def\stopitemize {\stopitemgroup}}

\let\strc_itemgroups_pop\relax

\protect \endinput