%D \module
%D   [       file=grph-par,
%D        version=2016.07.08,
%D          title=\CONTEXT\ Graphic Macros,
%D       subtitle=Patterns,
%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.

%D This works ok in Okular and MuPDF but somehow xforms don't work in Acrobat
%D (full nor reader). Also the basic offset is kind of unspecified. So \unknown\
%D we're dealing with a fragile feature. So, don't rely on where the first (ulr)
%D tile occurs.
%D
%D The two commands introduced here are not documented (yet).

\writestatus{loading}{ConTeXt Graphic Macros / Patterns}

\unprotect

\registerctxluafile{grph-pat}{}

\unexpanded\def\registerpattern
  {\begingroup
   \letdummyparameter\c!name   \s!dummy
   \letdummyparameter\c!width  \v!auto
   \letdummyparameter\c!height \v!auto
   \letdummyparameter\c!hoffset\zeropoint
   \letdummyparameter\c!voffset\zeropoint
   \dodoubleempty\syst_boxes_registerpattern}

\def\syst_boxes_registerpattern[#1][#2]%
  {\ifsecondargument
     \setdummyparameter\c!name{#1}%
     \getdummyparameters[#2]%
   \else\iffirstargument
     \doifassignmentelse{#1}
       {\getdummyparameters[#1]}%
       {\setdummyparameter\c!name{#1}}%
   \fi\fi
   \dowithnextboxcs\syst_boxes_registerpattern_indeed\hbox}

\edef\v!auto_m{-\v!auto}

\def\syst_boxes_registerpattern_indeed
  {%\finalizeobjectbox\nextbox
   \edef\p_width  {\dummyparameter\c!width}%
   \edef\p_height {\dummyparameter\c!height}%
   \edef\p_hoffset{\dummyparameter\c!hoffset}%
   \edef\p_voffset{\dummyparameter\c!voffset}%
   \scratchwidth  \dimexpr\ifx\p_width  \v!auto\wd  \nextbox   \else\p_width  \fi\relax
   \scratchheight \dimexpr\ifx\p_height \v!auto\htdp\nextbox   \else\p_height \fi\relax
   \scratchhoffset\dimexpr\ifx\p_hoffset\v!auto\scratchwidth /2\else\ifx\p_hoffset\v!auto_m-\scratchwidth /2\else\p_hoffset\fi\fi\relax
   \scratchvoffset\dimexpr\ifx\p_voffset\v!auto\scratchheight/2\else\ifx\p_voffset\v!auto_m-\scratchheight/2\else\p_voffset\fi\fi\relax
   \clf_registerpattern
      name    {\dummyparameter\c!name}
      number  \nextbox
      width   \scratchwidth
      height  \scratchheight
      hoffset \scratchhoffset
      voffset \scratchvoffset
   \relax
   \endgroup}

\unexpanded\def\applypattern
  {\hbox\bgroup
   \letdummyparameter\c!name  \s!dummy
   \letdummyparameter\c!width \zeropoint
   \letdummyparameter\c!height\zeropoint
   \dodoubleempty\syst_boxes_applypattern}

\def\syst_boxes_applypattern[#1][#2]%
  {\ifsecondargument
     \setdummyparameter\c!name{#1}%
     \getdummyparameters[#2]%
   \else\iffirstargument
     \doifassignmentelse{#1}
       {\getdummyparameters[#1]}%
       {\setdummyparameter\c!name{#1}}%
   \fi\fi
   \clf_applypattern
      name   {\dummyparameter\c!name}
      number \nextbox
      width  \dimexpr\dummyparameter\c!width\relax
      height \dimexpr\dummyparameter\c!height\relax
   \relax
   \box\nextbox
   \egroup}

\protect

\continueifinputfile{grph-pat.mkiv}

\nopdfcompression

\starttext

    \registerpattern[demo]{It \darkred Works!}

    \framed[offset=overlay]{\applypattern[demo][width=7cm,height=4cm]}

    \blank

    \registerpattern[name=more,hoffset=0bp,voffset=0pt]{\externalfigure[cow.pdf][width=1cm]}

    \framed[offset=overlay]{\applypattern[name=more,width=7cm,height=4cm]}

    \blank

    \registerpattern[name=more,hoffset=auto,voffset=auto]{\externalfigure[cow.pdf][width=1cm]}

    \framed[offset=overlay]{\applypattern[name=more,width=7cm,height=4cm]}

    \blank

    \registerpattern[name=more,hoffset=-auto,voffset=-auto]{\externalfigure[cow.pdf][width=1cm]}

    \framed[offset=overlay]{\applypattern[name=more,width=7cm,height=4cm]}

\stoptext