%D \module
%D   [       file=mp-back.mp,
%D        version=2000.05.31,
%D          title=\CONTEXT\ \METAPOST\ graphics,
%D       subtitle=backgrounds,
%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 licen-en.pdf for
%C details.

if known context_back : endinput ; fi ;

boolean context_back ; context_back := true ;

def some_hash ( expr hash_width     ,
                     hash_height    ,
                     hash_linewidth ,
                     hash_linecolor ,
                     hash_angle     ,
                     hash_gap       ) =

    begingroup ;
        stripe_gap := hash_gap ;
        stripe_angle := hash_angle ;
        drawoptions (withpen pencircle scaled hash_linewidth
                     withcolor hash_linecolor) ;
        path p ; p := unitsquare xscaled hash_width yscaled hash_height ;
        stripe_path_a () (draw) p ;  % next we move it all to quadrant 1
        currentpicture := currentpicture shifted urcorner currentpicture ;
    endgroup ;
enddef ;

def some_double_back (expr back_type        ,
                           back_width       ,
                           back_height      ,
                           back_delta       ,
                           back_linewidth   ,
                           back_linecolor   ,
                           back_fillcolor   ,
                           back_topcolor    ,
                           back_bottomcolor ,
                           back_leftcolor   ,
                           back_rightcolor  ) =

    begingroup ;

    save ww, hh, dd, p, q, r, s, t, u, v, w, a, c, d, e, f, back_nillcolor ;

    numeric ww ; ww := back_width  ;
    numeric hh ; hh := back_height ;
    numeric dd ; dd := back_delta  ;

    color back_nillcolor ; back_nillcolor := back_topcolor ;

    path p ; p := fullsquare xscaled  ww      yscaled  hh      ;
    path q ; q := fullsquare xscaled (ww-2dd) yscaled (hh-2dd) ;
    path r ; r := llcorner p --
                  lrcorner p shifted (-3dd,0) .. controls lrcorner p ..
                  lrcorner p shifted (0, 3dd) --
                  urcorner p shifted (0,-3dd) .. controls urcorner p ..
                  urcorner p shifted (-3dd,0) --
                  ulcorner p -- cycle ;
    path s ; s := r xscaled ((ww-2dd)/ww) yscaled ((hh-2dd)/hh) ;
    path t ; t := llcorner p --
                  lrcorner p --
                  urcorner p shifted (0,-3dd) .. controls urcorner p ..
                  urcorner p shifted (-3dd,0) --
                  ulcorner p shifted ( 3dd,0) .. controls ulcorner p ..
                  ulcorner p shifted (0,-3dd) --
                  llcorner p -- cycle ;
    path u ; u := t xscaled ((ww-2dd)/ww) yscaled ((hh-2dd)/hh) ;
    path v ; v := llcorner p shifted ( 3dd,0) --
                  lrcorner p shifted (-3dd,0) .. controls lrcorner p ..
                  lrcorner p shifted (0, 3dd) --
                  urcorner p shifted (0,-3dd) .. controls urcorner p ..
                  urcorner p shifted (-3dd,0) --
                  ulcorner p shifted ( 3dd,0) .. controls ulcorner p ..
                  ulcorner p shifted (0,-3dd) ..
                  llcorner p shifted (0, 3dd) .. controls llcorner p .. cycle ; % {down}  .. cycle ;
    path w ; w := t xscaled ((ww-2dd)/ww) yscaled ((hh-2dd)/hh) ;
    path a ; a := llcorner p -- ulcorner p --
                  ulcorner q -- llcorner q -- cycle ;
    path b ; b := llcorner p -- lrcorner p --
                  lrcorner q -- llcorner q -- cycle ;
    path c ; c := lrcorner p -- urcorner p --
                  urcorner q -- lrcorner q -- cycle ;
    path d ; d := ulcorner p -- urcorner p --
                  urcorner q -- ulcorner q -- cycle ;
    path e ; e := llcorner p -- lrcorner p --
                  urcorner p -- urcorner q --
                  lrcorner q -- llcorner q -- cycle ;
    path f ; f := llcorner p -- ulcorner p --
                  urcorner p -- urcorner q --
                  ulcorner q -- llcorner q -- cycle ;

    linecap := butt ; pickup pencircle scaled back_linewidth ;

    if back_type = 1 :

      fill p withcolor back_fillcolor   ;
      fill a withcolor back_leftcolor   ;
      fill b withcolor back_bottomcolor ;
      fill c withcolor back_rightcolor  ;
      fill d withcolor back_topcolor    ;
      draw a withcolor back_linecolor   ;
      draw d withcolor back_linecolor   ;
      draw b withcolor back_linecolor   ;
      draw c withcolor back_linecolor   ;

    elseif back_type = 2 :

      fill p withcolor back_fillcolor   ;
      fill e withcolor back_bottomcolor ;
      fill f withcolor back_topcolor    ;
      draw e withcolor back_linecolor   ;
      draw f withcolor back_linecolor   ;

    elseif back_type = 3 :

      fill v withcolor back_nillcolor   ;
      fill w withcolor back_fillcolor   ;
      draw v withcolor back_linecolor   ;
      draw w withcolor back_linecolor   ;

    elseif back_type = 4 :

      fill t withcolor back_nillcolor   ;
      fill u withcolor back_fillcolor   ;
      draw t withcolor back_linecolor   ;
      draw u withcolor back_linecolor   ;

    elseif back_type = 5 :

      t := t rotatedaround(center t,180) ;
      u := u rotatedaround(center u,180) ;

      fill t withcolor back_nillcolor   ;
      fill u withcolor back_fillcolor   ;
      draw t withcolor back_linecolor   ;
      draw u withcolor back_linecolor   ;

    elseif back_type = 6 :

      r := r rotatedaround(center r,180) ;
      s := s rotatedaround(center s,180) ;

      fill r withcolor back_nillcolor   ;
      fill s withcolor back_fillcolor   ;
      draw r withcolor back_linecolor   ;
      draw s withcolor back_linecolor   ;

    elseif back_type = 7 :

      fill r withcolor back_nillcolor   ;
      fill s withcolor back_fillcolor   ;
      draw r withcolor back_linecolor   ;
      draw s withcolor back_linecolor   ;

    fi ;

    endgroup;
enddef ;

% endinput ;
%
% beginfig (1) ;
%
% some_double_back (1, 4.5cm, 1.5cm, .25cm, 1mm,
%            .5white, .8white, .7white, .6white, .7white, .6white)
%
% currentpicture := currentpicture shifted (0,-3cm) ;
%
% some_double_back (2, 4.5cm, 1.5cm, .25cm, 1mm,
%            .5white, .8white, .7white, .6white, white, white)
%
% currentpicture := currentpicture shifted (0,-3cm) ;
%
% some_double_back (3, 4.5cm, 1.5cm, .25cm, 1mm,
%            .5white, .8white, .7white, white, white, white)
%
% currentpicture := currentpicture shifted (0,-3cm) ;
%
% some_double_back (4, 4.5cm, 1.5cm, .25cm, 1mm,
%            .5white, .8white, .7white, white, white, white)
%
% currentpicture := currentpicture shifted (0,-3cm) ;
%
% some_double_back (5, 4.5cm, 1.5cm, .25cm, 1mm,
%            .5white, .8white, .7white, white, white, white)
%
% currentpicture := currentpicture shifted (0,-3cm) ;
%
% some_double_back (6, 4.5cm, 1.5cm, .25cm, 1mm,
%            .5white, .8white, .7white, white, white, white)
%
% currentpicture := currentpicture shifted (0,-3cm) ;
%
% some_double_back (7, 4.5cm, 1.5cm, .25cm, 1mm,
%            .5white, .8white, .7white, white, white, white)
%
% currentpicture := currentpicture shifted (0,-3cm) ;
%
% some_double_back (8, 4.5cm, 1.5cm, .25cm, 1mm,
%            .5white, .8white, .7white, white, white, white)
%
% endfig ;
%
% end .
