%D \module
%D   [       file=spac-fil,
%D        version=2013.01.13,
%D          title=\CONTEXT\ Spacing Macros,
%D       subtitle=Fillers,
%D         author={Hans Hagen and Wolfgang Schuster},
%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 Spacing Macros / Fillers}

\unprotect

%D A bit more extensive variant of a prototype posted by Wolfgang to the development
%D list. Instead of dealing with a few leader types it makes sense to support them
%D all as well as simple rule fillers. Eventually we can also use in for the
%D mathfillers. We distinguish between alternatives and with them methods, and a
%D checker is provided for use in applying e.g.\ fillers in lists.

\installcorenamespace{filler}
\installcorenamespace{filleralternative}
\installcorenamespace{fillerleadermethod}

\installcommandhandler \??filler {filler} \??filler

\aliased\let\setupfillers\setupfiller

\permanent\protected\def\checkedfiller#1%
  {\ifcsname\namedfillerhash{#1}\s!parent\endcsname
     \filler[#1]%
     \expandafter\gobbleoneargument
   \else
     \expandafter\firstofoneargument
   \fi{#1}}

\permanent\tolerant\protected\def\filler[#1]%
  {\removeunwantedspaces
   \begingroup
   \cdef\currentfiller{#1}%
   \usefillerstyleandcolor\c!style\c!color
   \scratchdimen{\fillerparameter\c!leftmargin}%
   \ifzeropt\scratchdimen\else
     \hskip\scratchdimen
   \fi
   \fillerparameter\c!left\relax
   \expandnamespaceparameter\??filleralternative\fillerparameter\c!alternative\s!unknown\relax
   \fillerparameter\c!right\relax
   \scratchdimen\fillerparameter\c!rightmargin\relax
   \ifzeropt\scratchdimen\else
     \hskip\scratchdimen
   \fi
   \endgroup
   \ignorespaces}

% \definefiller
%   [MyFiller]
%   [offset=.25\emwidth,
%    rightmargindistance=-\rightskip,
%    method=middle]
%
% \startitemize[packed,joinedup][rightmargin=5em]
%     \startitem
%         \input sapolsky \fillupto[MyFiller]{RS}
%     \stopitem
% \stopitemize

\permanent\tolerant\protected\def\fillupto[#1]#:#2%
  {\removeunwantedspaces
   \begingroup
   \cdef\currentfiller{#1}%
   \scratchdimen{\fillerparameter\c!rightmargindistance}%
   \ifzeropt\scratchdimen\else
     \parfillskip \scratchdimen\s!plus \plusone\s!fil\relax
   \fi
   \filler[#1]%
   \ifempty{#2}\else
     \hbox{#2}%
   \fi
   \par
   \endgroup
   \ignorespaces}

\defcsname\??filleralternative\s!unknown\endcsname
  {}

\defcsname\??filleralternative\v!symbol\endcsname
  {\expandnamespaceparameter\??fillerleadermethod\fillerparameter\c!method\v!local
     \ifdim{\fillerparameter\c!offset}>\zeropoint
        \simplealignedspreadbox
          {2\dimexpr\fillerparameter\c!offset\relax}%
          {\fillerparameter\c!align}%
          {\fillerparameter\c!symbol}%
     \else
        \simplealignedbox
          {\fillerparameter\c!width}%
          {\fillerparameter\c!align}%
          {\fillerparameter\c!symbol}%
     \fi
   \hfill}

\defcsname\??filleralternative\v!stretch\endcsname
  {\hfill}

\defcsname\??filleralternative\v!space\endcsname
  {\hskip\glueexpr\fillerparameter\c!distance\relax\relax}

\defcsname\??filleralternative\v!rule\endcsname
  {\expandnamespaceparameter\??fillerleadermethod\fillerparameter\c!method\v!local
     \hrule
       \s!height{\fillerparameter\c!height}%
       \s!depth {\fillerparameter\c!depth}%
   \hfill}

\letcsname\??fillerleadermethod\s!local \endcsname\normalleaders  % overflow ends up inbetween (current box)
\letcsname\??fillerleadermethod\v!global\endcsname\normalgleaders % overflow ends up inbetween (outermost box)
\letcsname\??fillerleadermethod\v!middle\endcsname\normalcleaders % overflow ends up before, after (current box)
\letcsname\??fillerleadermethod\v!broad \endcsname\normalxleaders % overflow ends up before, inbetween, after (current box)

\setupfillers
  [\c!width=\emwidth,
   \c!symbol=.,
   \c!distance=\emwidth,
   \c!offset=\zeropoint,
   \c!align=\v!middle,
   \c!height=.1\exheight,
   \c!depth=\zeropoint,
   \c!leftmargin=\zeropoint,
   \c!rightmargin=\zeropoint,
   \c!rightmargindistance=\zeropoint,
   \c!alternative=\v!symbol,
   \c!method=\s!local]

\definefiller
  [\v!sym]
  [\c!method=\v!global,
   \c!width=.5\emwidth,
   \c!leftmargin=.5\emwidth,
   \c!rightmargin=.5\emwidth]

\definefiller
  [\v!symbol]
  [\c!method=\v!global,
   \c!offset=.125\emwidth,
   \c!leftmargin=.5\emwidth,
   \c!rightmargin=.5\emwidth]

\definefiller
  [\v!rule]
  [\c!alternative=\v!rule,
   \c!leftmargin=.5\emwidth,
   \c!rightmargin=.5\emwidth]

\definefiller
  [\v!width]
  [\c!alternative=\v!stretch]

\definefiller
  [\v!space]
  [\c!alternative=\v!space,
   \c!distance=3\emwidth]

% bonus:

\definefiller
  [dotfill]
  [\c!symbol=\textperiod,
   \c!style=\v!normal,
   \c!method=\v!middle,
   \c!width=.5\emwidth,
   \c!leftmargin=.2\emwidth,
   \c!rightmargin=.2\emwidth]

% If users really want it:
%
% \permanent\protected\def\mathdotfill{\cleaders\hbox{$\mathsurround\zeropoint\mkern1.5mu.\mkern1.5mu$}\hfill} % plain
% \permanent\protected\def\textdotfill{\filler[dotfill]}
% \permanent\protected\def\dotfill    {\mathortext\mathdotfill\textdotfill}

\permanent\protected\def\dotfill{\filler[dotfill]}

% maybe box -> symbol

\protect \endinput

% \definefiller[test-a][alternative=stretch]
% \definefiller[test-b][alternative=symbol,symbol=!]
% \definefiller[test-c][alternative=rule,height=.1ex,leftmargin=.5em,rightmargin=.25em]

% \starttext
%     text\filler[test-a]text \par
%     text\filler[test-b]text \par
%     text\filler[test-c]text \par
%     text\checkedfiller{<nothing>}text \par
% \stoptext
