%D \module
%D   [       file=meta-dum,
%D        version=2003.03.21,
%D          title=\METAPOST\ Graphics,
%D       subtitle=Dummy (External) Graphics,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA / Hans Hagen \& Ton Otten}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

\unprotect

%D This library overloads the normal external figure
%D placeholder by a nicer one.
%D
%D \startbuffer
%D \useMPlibrary[dum]
%D
%D \startlinecorrection
%D \useMPgraphic{placeholder}{width=3cm,height=4cm,color=red}
%D \stoplinecorrection
%D
%D \startlinecorrection
%D \useMPgraphic{placeholder}{width=8cm,height=10cm,color=green}
%D \stoplinecorrection
%D
%D \startlinecorrection
%D \externalfigure[unknown-a][width=3cm,height=1cm]
%D \stoplinecorrection
%D
%D \startlinecorrection
%D \externalfigure[unknown-b][width=4cm,height=5cm]
%D \stoplinecorrection
%D \stopbuffer
%D
%D \typebuffer \getbuffer

% currently preparempvariables is unable to resolve number
% fractions like reduction

% June 22, 2003, this definition was patched to adapt itself
% to transparent colors

\startuseMPgraphic{placeholder}{width,height,color}
  numeric w, h, d, r ; color c, b, cc ; path p ; boolean t ;
  t := is_transparent(\MPvar{color}) ;
  c := not_transparent(\MPvar{color}) ;
  b := not_transparent(white) ;
  w := \MPvar{width} ;
  h := \MPvar{height} ;
  r := \MPvar{reduction} ;
  d := max(w,h) ;
  p := unitsquare xyscaled (w,h) ;
  cc := r[.5c,b] ;
  fill p withcolor if t : transparent(1,.5,cc) else : cc fi ;
  for i := 1 upto 60 :
    cc := r[c randomized(.3,.9),b] ;
    fill fullcircle
      scaled (d/5 randomized (d/5))
      shifted (center p randomized (d))
      withcolor if t : transparent(1,.5,cc) else : cc fi ;
  endfor ;
  clip currentpicture to p ;
\stopuseMPgraphic

\definepalet
  [placeholder]
  [1=red,2=green,3=blue,4=cyan,5=magenta,6=yellow]

% \newcounter \figurereplacementcycle

\let\figurereplacementcycle\relax

\setupexternalfigures
  [\c!reductie=0,
   \c!tekst=\v!ja]

\def\externalfigurereplacement#1#2#3%
  {\getpaletsize[placeholder]%
   \ifx\figurereplacementcycle\relax
     \getrandomnumber \figurereplacementcycle \!!plusone \paletsize
     \globallet \figurereplacementcycle \figurereplacementcycle
   \else
     \doglobal\increment\figurereplacementcycle
   \fi
   \ifnum\figurereplacementcycle>\paletsize
     \globallet\figurereplacementcycle\!!plusone
   \fi
   \weightGRAYfalse % monochrome anyway
   \defineoverlay
     [\s!dummy]
     [\useMPgraphic
        {placeholder}%
        {width=\figurewidth,
         height=\figureheight,
         reduction=\@@efreductie,
         color=placeholder:\figurereplacementcycle}]%
   \expanded{\localframed
     [\??ef]
     [\c!breedte=\figurewidth,
      \c!hoogte=\figureheight,
      \c!kader=\v!uit,
      \c!strut=\v!nee,
      \c!achtergrond=\s!dummy,
      \c!voorgrondkleur=white]}%
     {\doif\@@eftekst\v!ja
        {\infofont \setupinterlinespace \dohyphens % \nohyphens
         \doifelse{#1}\s!dummy  \!!doneafalse\!!doneatrue
         \doifelse{#2}\s!dummy  \!!donebfalse\!!donebtrue
         \doifelse{#3}\s!unknown\!!donecfalse\!!donectrue
         \if!!donea
           name: \expanded{\verbatimstring{#1}}\strut\endgraf
         \fi
         \if!!doneb
           \if!!donea file: \else \if!!donec file: \fi \fi
           \expanded{\verbatimstring{#2}}\strut\endgraf
         \fi
         \if!!donec
           state: \expanded{\verbatimstring{#3}}\strut\endgraf
         \fi}}}

\def\dummyfigure{\externalfigure[placeholder]}

\protect \endinput