%D \module
%D   [       file=mp-chem.mp,
%D        version=2009.05.13,
%D          title=\CONTEXT\ \METAPOST\ graphics,
%D       subtitle=chemicals,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright=\PRAGMA]
%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.

%D This module in incomplete and experimental.

% either consistent setting or not

if known chem_reset : endinput ; fi ;

numeric
    chem_width, chem_radical_min, chem_radical_max, chem_text_max, chem_circle_radius,
    chem_rotation, chem_adjacent, chem_stack, chem_substituent, chem_direction, chem_setting_scale,
    chem_setting_offset, chem_text_offset, chem_picture_offset, chem_center_offset, chem_substituent_offset,
    chem_setting_l, chem_setting_r, chem_setting_t, chem_setting_b ;

boolean
    chem_setting_axis,
    chem_setting_fixedwidth, chem_setting_fixedheight,
    chem_doing_pb, chem_text_trace ;

path
    chem_setting_bbox ;

pair
    chem_shift,
    chem_adjacent_p, chem_substituent_p, chem_direction_p, chem_move_p ;

numeric
    chem_width[], chem_angle[], chem_start[], chem_initialrot[], chem_initialmov[] ;

pair
    chem_stack_d[],
    chem_b_zero[], chem_n_zero[],
    chem_r_max[], chem_r_min[],
    chem_r_zero[], chem_mr_zero[], chem_pr_zero[], chem_crz_zero[],
    chem_rt_zero[], chem_rtt_zero[], chem_rbt_zero[],
    chem_mid_zero[] ;

path
    chem_b_path[], chem_bx_path[], chem_eb_path[], chem_sr_path[], chem_br_path[],
    chem_sb_path[], chem_msb_path[], chem_psb_path[],
    chem_s_path[], chem_ss_path[], chem_mss_path[], chem_pss_path[],
    chem_e_path[], chem_sd_path[], chem_bb_path[], chem_oe_path[],
    chem_bd_path[], chem_bw_path[],
    chem_ddt_path[], chem_ddb_path[], chem_ldt_path[], chem_ldb_path[], chem_rdt_path[], chem_rdb_path[],
    chem_dbl_path[], chem_dbr_path[],
    chem_ad_path[], chem_au_path[],
    chem_r_path[], chem_rl_path[], chem_rr_path[],
    chem_rb_path[], chem_prb_path[], chem_mrb_path[],
    chem_srl_path[], chem_srr_path[],
    chem_msr_path[], chem_psr_path[],
    chem_mr_path[], chem_pr_path[],
    chem_c_path[], chem_cc_path[],
    chem_midt_path[], chem_midb_path[], chem_midst_path[], chem_midsb_path[] ;

chem_setting_scale      :=  1 ;
chem_base_width         := 40pt ;
chem_text_offset        :=  3pt ;
chem_center_offset      :=  6pt ;
chem_picture_offset     := 10pt ;
chem_substituent_offset := 10pt ;
chem_radical_min        :=  1.25 ;
chem_radical_max        :=  1.50 ;
chem_text_min           :=  0.75 ;
chem_text_max           :=  1.75 ;
chem_circle_radius      :=  0.80 ;
chem_circle_radius      :=  1.10 ;
chem_rotation           :=  1 ;
chem_adjacent           :=  0 ;
chem_substituent        :=  0 ;
chem_direction          :=  0 ;
chem_stack_n            :=  0 ;
chem_doing_pb           :=  false ;
chem_shift              := origin ;
chem_dot_factor         := 4 ;
chem_text_trace         := false ;
chem_bd_n               := 4 ;
chem_bw_n               := 4 ;
chem_bd_angle           := 4 ;
chem_bb_angle           := 4 ;

vardef chem_start_structure(expr n, l, r, t, b, scale, axis, fixedwidth, fixedheight, offset) =
    chem_setting_axis := axis ;
    chem_setting_l := l * scale ;
    chem_setting_r := r * scale ;
    chem_setting_t := t * scale ;
    chem_setting_b := b * scale ;
    chem_setting_fixedwidth := fixedwidth ;
    chem_setting_fixedheight := fixedheight ;
    chem_setting_offset := offset ;
    if scale <> chem_setting_scale :
        chem_setting_scale := scale ;
        chem_init_all ;
    fi ;
    chem_rotation    := 1 ;
    chem_adjacent    := 0 ;
    chem_substituent := 0 ;
    chem_direction   := 0 ;
    chem_stack_n     := 0 ;
    chem_doing_pb    := false ;
    chem_shift       := origin ;
enddef ;

def chem_stop_structure =
    currentpicture := currentpicture shifted - chem_shift ;
    % axis here
    if chem_setting_fixedwidth :
        chem_setting_l := - xpart llcorner currentpicture ;
        chem_setting_r :=   xpart urcorner currentpicture ;
    fi ;
    if chem_setting_fixedheight :
        chem_setting_t :=   ypart urcorner currentpicture ;
        chem_setting_b := - ypart llcorner currentpicture ;
    fi ;
    chem_setting_bbox :=
        (-chem_setting_l,-chem_setting_b) -- ( chem_setting_r,-chem_setting_b) --
        ( chem_setting_r, chem_setting_t) -- (-chem_setting_l, chem_setting_t) -- cycle ;
    % maybe put it behind the picture
    if chem_setting_axis :
        save stp ; stp := chem_base_width/ 2 * chem_setting_scale ;
        save siz ; siz := chem_base_width/10 * chem_setting_scale ;
        draw (-chem_setting_l,0) -- (chem_setting_r,0) withcolor blue ;
        draw (0,-chem_setting_b) -- (0,chem_setting_t) withcolor blue ;
        for i = 0 step  stp until  chem_setting_r : draw (i,-siz) -- (i,siz) withcolor blue ; endfor ;
        for i = 0 step -stp until -chem_setting_l : draw (i,-siz) -- (i,siz) withcolor blue ; endfor ;
        for i = 0 step  stp until  chem_setting_t : draw (-siz,i) -- (siz,i) withcolor blue ; endfor ;
        for i = 0 step -stp until -chem_setting_b : draw (-siz,i) -- (siz,i) withcolor blue ; endfor ;
        draw chem_setting_bbox withcolor blue ;
    fi ;
    setbounds currentpicture to chem_setting_bbox ;
enddef ;

def chem_start_component =
enddef ;
def chem_stop_component =
enddef ;

def chem_pb =
% draw boundingbox currentpicture withpen pencircle scaled 1mm withcolor blue ;
% draw origin withpen pencircle scaled 2mm withcolor blue ;
    chem_doing_pb := true ;
enddef ;
def chem_pe =
% draw boundingbox currentpicture withpen pencircle scaled .5mm withcolor red ;
% draw origin withpen pencircle scaled 1mm withcolor red ;
    currentpicture := currentpicture shifted - chem_shift ;
% draw origin withpen pencircle scaled .5mm withcolor green ;
    chem_shift := origin ;
    chem_doing_pb := false ;
enddef ;

vardef chem_do (expr p) =
    if chem_doing_pb :
        chem_doing_pb := false ;
%         save pp ; pair pp ; pp := point 1 of ((origin -- p) enlonged chem_picture_offset) ;
%         currentpicture := currentpicture shifted - pp ;
%         chem_shift := chem_shift - center pp ;
        currentpicture := currentpicture shifted - p ;
        chem_shift := chem_shift - p ;
        origin %  nullpicture
    else :
        p
    fi
enddef ;

vardef chem_b (expr n, f, t, r, c) =
    chem_draw (n, chem_b_path[n], f, t, r, c)  ;
enddef ;
vardef chem_sb (expr n, f, t, r, c) =
    chem_draw (n, chem_sb_path[n], f, t, r, c) ;
enddef ;
vardef chem_s (expr n, f, t, r, c) =
    chem_draw (n, chem_s_path[n], f, t, r, c) ;
enddef ;
vardef chem_ss (expr n, f, t, r, c) =
    chem_draw (n, chem_ss_path[n], f, t, r, c) ;
enddef ;
vardef chem_mid (expr n, r, c) =
    chem_draw_fixed (n, chem_midt_path[n], r, c) ;
    chem_draw_fixed (n, chem_midb_path[n], r, c) ;
enddef ;
vardef chem_mids (expr n, r, c) =
    chem_draw_fixed (n, chem_midst_path[n], r, c) ;
    chem_draw_fixed (n, chem_midsb_path[n], r, c) ;
enddef ;
vardef chem_mss (expr n, f, t, r, c) =
    chem_draw (n, chem_mss_path[n], f, t, r, c) ;
enddef ;
vardef chem_pss (expr n, f, t, r, c) =
    chem_draw (n, chem_pss_path[n], f, t, r, c) ;
enddef ;
vardef chem_msb (expr n, f, t, r, c) =
    chem_draw (n, chem_msb_path[n], f, t, r, c) ;
enddef ;
vardef chem_psb (expr n, f, t, r, c) =
    chem_draw (n, chem_psb_path[n], f, t, r, c) ;
enddef ;
vardef chem_eb  (expr n, f, t, r, c) =
    chem_draw (n, chem_eb_path[n], f, t, r, c) ;
enddef ;
vardef chem_db (expr n, f, t, r, c) =
    if n = 1 :
        chem_draw (n, chem_msb_path [n], f, t, r, c) ;
        chem_draw (n, chem_psb_path [n], f, t, r, c) ;
    else :
        chem_draw (n, chem_dbl_path  [n], f, t, r, c) ;
        chem_draw (n, chem_dbr_path  [n], f, t, r, c) ;
    fi ;
enddef ;
vardef chem_er (expr n, f, t, r, c) =
    chem_draw (n, chem_rl_path[n], f, t, r, c) ;
    chem_draw (n, chem_rr_path[n], f, t, r, c) ;
enddef ;
vardef chem_dr (expr n, f, t, r, c) =
    chem_draw (n, chem_srl_path[n], f, t, r, c) ;
    chem_draw (n, chem_srr_path[n], f, t, r, c) ;
enddef ;
vardef chem_ad (expr n, f, t, r, c) =
    chem_draw_arrow(n, chem_ad_path[n], f, t, r, c) ;
enddef ;
vardef chem_au (expr n, f, t, r, c) =
    chem_draw_arrow(n, chem_au_path[n], f, t, r, c)
enddef ;
vardef chem_r (expr n, f, t, r, c) =
    if n < 0 :
        chem_draw_vertical (n, chem_r_path[n], f, t, r, c) ;
    else :
        chem_draw (n, chem_r_path[n], f, t, r, c) ;
    fi ;
enddef ;
vardef chem_rd (expr n, f, t, r, c) =
    chem_dashed_normal (n, chem_r_path[n], f, t, r, c)
enddef ;
vardef chem_mrd (expr n, f, t, r, c) =
    chem_dashed_normal (n, chem_mr_path[n], f, t, r, c)
enddef ;
vardef chem_prd (expr n, f, t, r, c) =
    chem_dashed_normal (n, chem_pr_path[n], f, t, r, c)
enddef ;
vardef chem_br (expr n, f, t, r, c) =
    chem_fill (n, chem_br_path[n], f, t, r, c )
enddef ;
vardef chem_rb (expr n, f, t, r, c) =
    chem_fill (n, chem_rb_path[n], f, t, r, c)
enddef ;
vardef chem_mrb (expr n, f, t, r, c) =
    chem_fill (n, chem_mrb_path[n], f, t, r, c)
enddef ;
vardef chem_prb (expr n, f, t, r, c) =
    chem_fill (n, chem_prb_path[n], f, t, r, c)
enddef ;
vardef chem_mr (expr n, f, t, r, c) =
    if n < 0 :
        chem_draw_vertical(n, chem_mr_path[n], f, t, r, c)
    else :
        chem_draw (n, chem_mr_path[n], f, t, r, c)
    fi
enddef ;
vardef chem_pr (expr n, f, t, r, c) =
    if n < 0 :
        chem_draw_vertical(n, chem_pr_path[n], f, t, r, c)
    else :
        chem_draw (n, chem_pr_path[n], f, t, r, c)
    fi
enddef ;
vardef chem_sr (expr n, f, t, r, c) =
    chem_draw (n, chem_sr_path[n], f, t, r, c)
enddef ;
vardef chem_msr (expr n, f, t, r, c) =
    chem_draw (n, chem_msr_path[n], f, t, r, c)
enddef ;
vardef chem_psr (expr n, f, t, r, c) =
    chem_draw (n, chem_psr_path[n], f, t, r, c)
enddef ;
vardef chem_c (expr n, f, t, r, c) =
    chem_draw (n, chem_c_path[n], f, t, r, c)
enddef ;
vardef chem_cc (expr n, f, t, r, c) =
    chem_draw (n, chem_cc_path[n], f, f, r, c)
enddef ;
vardef chem_cd (expr n, f, t, r, c) =
    chem_dashed_connected (n, chem_c_path[n], f, t, r, c)
enddef ;
vardef chem_ccd (expr n, f, t, r, c) =
    chem_dashed_normal (n, chem_cc_path[n], f, f, r, c)
enddef ;
vardef chem_rn  (expr n, i, t) =
    chem_rt (n,i,t) ;
enddef ;
vardef chem_rtn (expr n, i, t) =
    chem_rtt(n,i,t) ;
enddef ;
vardef chem_rbn (expr n, i, t) =
    chem_rbt(n,i,t) ;
enddef ;
vardef chem_tb (expr n, f, t, r, c) = % one
    chem_draw (n, chem_msb_path[n], f, t, r, c) ;
    chem_draw (n, chem_sb_path [n], f, t, r, c) ;
    chem_draw (n, chem_psb_path[n], f, t, r, c) ;
enddef ;
vardef chem_ep (expr n, f, t, r, c) = % one
    chem_draw (n, chem_e_path[n], f, t, r, c) ;
enddef ;
vardef chem_es (expr n, f, t, r, c) = % one
    chem_draw_dot (n, center chem_e_path[n], f, t, r, c) ;
enddef ;
vardef chem_ed (expr n, f, t, r, c) = % one
    chem_draw_dot (n, point 0 of chem_e_path[n], f, t, r, c) ;
    chem_draw_dot (n, point 1 of chem_e_path[n], f, t, r, c) ;
enddef ;
vardef chem_et (expr n, f, t, r, c) = % one
    chem_draw_dot (n, point 0 of chem_e_path[n], f, t, r, c) ;
    chem_draw_dot (n, center     chem_e_path[n], f, t, r, c) ;
    chem_draw_dot (n, point 1 of chem_e_path[n], f, t, r, c) ;
enddef ;
vardef chem_sd (expr n, f, t, r, c) = % one
    chem_draw (n, chem_ddt_path[n], f, t, r, c) ;
    chem_draw (n, chem_ddb_path[n], f, t, r, c) ;
enddef ;
vardef chem_rdd (expr n, f, t, r, c) = % one
    chem_draw (n, chem_ldt_path[n], f, t, r, c) ;
    chem_draw (n, chem_ldb_path[n], f, t, r, c) ;
    chem_draw (n, chem_psb_path[n], f, t, r, c) ;
enddef ;
vardef chem_ldd (expr n, f, t, r, c) = % one
    chem_draw (n, chem_msb_path[n], f, t, r, c) ;
    chem_draw (n, chem_rdt_path[n], f, t, r, c) ;
    chem_draw (n, chem_rdb_path[n], f, t, r, c) ;
enddef ;
vardef chem_hb (expr n, f, t, r, c) = % one
    chem_draw_dot (n, point 0 of chem_sb_path[n], f, t, r, c) ;
    chem_draw_dot (n, center     chem_sb_path[n], f, t, r, c) ;
    chem_draw_dot (n, point 1 of chem_sb_path[n], f, t, r, c) ;
enddef ;
vardef chem_bb (expr n, f, t, r, c) = % one
    if n < 0 :
        chem_fill (n, chem_bb_path[n], 1, 1, r, c) ;
        chem_b (n, f, t, r, c) ;
    else :
        chem_fill (n, chem_bb_path[n], f, t, r, c) ;
    fi ;
enddef ;
vardef chem_oe (expr n, f, t, r, c) = % one
    chem_draw (n, chem_oe_path[n], f, t, r, c) ;
enddef ;
vardef chem_bd (expr n, f, t, r, c) = % one
    for i=0 upto 5 :
        chem_draw (n, subpath (2i,2i+1) of chem_bd_path[n], f, t, r, c) ;
    endfor ;
enddef ;
vardef chem_bw (expr n, f, t, r, c) = % one
    chem_draw (n, chem_bw_path[n], f, t, r, c) ;
enddef ;

vardef chem_z_zero@#(text t) =
    chem_text@#(t, chem_do(origin)) ;
enddef ;
vardef chem_cz_zero@#(text t) =
    chem_text@#(t, chem_do(origin)) ;
enddef ;
vardef chem_z@#(expr n, p) (text t) =
    if p = 0 :
        chem_text@#(t, chem_do(origin)) ;
    else :
        chem_text@#(t, chem_do(chem_b_zero[n] rotated chem_ang(n,p))) ;
    fi ;
enddef ;
vardef chem_cz@#(expr n, p) (text t) =
    if n = 1 :
        chem_c_text(t, chem_do(chem_crz_zero[n] rotated chem_ang(n,p))) ;
    else :
        chem_text@#(t, chem_do(chem_b_zero[n] rotated chem_ang(n,p))) ;
    fi ;
enddef ;
vardef chem_midz@#(expr n, p) (text t) =
    chem_text@#(t, chem_do(chem_mid_zero[n] rotated chem_ang(n,p))) ;
enddef ;
vardef chem_rz@#(expr n, p) (text t) =
    if n < 0 :
        % quite special
        chem_text@#(t, chem_do(chem_r_zero[n] shifted (chem_b_zero[n] rotated chem_ang(n,p)))) ;
    else :
        chem_text@#(t, chem_do(chem_r_zero[n] rotated chem_ang(n,p))) ;
    fi ;
enddef ;
vardef chem_crz@#(expr n, p) (text tx) =
    chem_text(tx, chem_do(chem_crz_zero[n] rotated chem_ang(n,p))) ;
enddef ;
vardef chem_mrz@#(expr n, p) (text t) =
    if n < 0 :
        % quite special
        chem_text@#(t, chem_do(chem_mr_zero[n] shifted (chem_b_zero[n] rotated chem_ang(n,p)))) ;
    else :
        chem_text@#(t, chem_do(chem_mr_zero[n] rotated chem_ang(n,p))) ;
    fi ;
enddef ;
vardef chem_prz@#(expr n, p) (text t) =
    if n < 0 :
        % quite special
        chem_text@#(t, chem_do(chem_pr_zero[n] shifted (chem_b_zero[n] rotated chem_ang(n,p)))) ;
    else :
        chem_text@#(t, chem_do(chem_pr_zero[n] rotated chem_ang(n,p))) ;
    fi ;
enddef ;
vardef chem_rt@#(expr n, p) (text t) =
    chem_text@#(t, chem_do(chem_rt_zero[n] rotated chem_ang(n,p))) ;
enddef ;
vardef chem_rtt@#(expr n, p) (text t) =
    chem_text@#(t, chem_do(chem_rtt_zero[n] rotated chem_ang(n,p))) ;
enddef ;
vardef chem_rbt@#(expr n, p) (text t) =
    chem_text@#(t, chem_do(chem_rbt_zero[n] rotated chem_ang(n,p))) ;
enddef ;
vardef chem_zt@#(expr n, p) (text t) =
    if n = 1 :
        chem_text@#(t, chem_do(chem_rt_zero[n] rotated chem_ang(n,p))) ;
    else :
        chem_text@#(t, chem_do(chem_n_zero[n] rotated chem_ang(n,p))) ;
    fi ;
enddef ;
vardef chem_zn@#(expr n, p) (text t) =
    if n = 1 :
        chem_text@#(t, chem_do(chem_rt_zero[n] rotated chem_ang(n,p))) ;
    else :
        chem_text@#(t, chem_do(chem_n_zero[n] rotated chem_ang(n,p))) ;
    fi ;
enddef ;
vardef chem_zbt@#(expr n, p) (text t) =
    chem_text@#(t, chem_do(chem_rtt_zero[n] rotated chem_ang(n,p))) ;
enddef ;
vardef chem_zbn@#(expr n, p) (text t) =
    chem_text@#(t, chem_do(chem_rtt_zero[n] rotated chem_ang(n,p))) ;
enddef ;
vardef chem_ztt@#(expr n, p) (text t) =
    chem_text@#(t, chem_do(chem_rbt_zero[n] rotated chem_ang(n,p))) ;
enddef ;
vardef chem_ztn@#(expr n, p) (text t) =
    chem_text@#(t, chem_do(chem_rbt_zero[n] rotated chem_ang(n,p))) ;
enddef ;

vardef chem_symbol(expr t) =
    draw textext(t) ;
enddef ;

vardef chem_text@#(expr txt, z) = % adapted copy of thelabel@
    save p ; picture p ;
    p := textext(txt) ;
    p := p
        if (labtype@# >= 10) : shifted (0,ypart center p) fi
        shifted (z + chem_text_offset*laboff@# - (labxf@#*lrcorner p + labyf@#*ulcorner p + (1-labxf@#-labyf@#)*llcorner p)) ;
    if chem_text_trace :
        draw z             withpen pencircle scaled 2pt withcolor red ;
        draw boundingbox p withpen pencircle scaled 1pt withcolor red ;
    fi ;
    draw p
enddef ;

vardef chem_c_text(expr txt, z) = % adapted copy of thelabel@
    save p ; picture p ; p := textext(txt) ;
    save b ; path b ; b := (boundingbox p) shifted z ;
    save a ; pair a ; a := (origin--z) intersection_point b ;
    if intersection_found :
        draw p shifted (z enlonged arclength(a -- center b)) ;
    else :
        draw p shifted z ;
    fi
%     draw b withcolor green ;
%     draw a withcolor red ;
enddef ;

vardef chem_ang (expr n, d) =
    ((-1 * (d-1) * chem_angle[n]) + (-chem_rotation+1) * 90 + chem_start[n]) % no ;
enddef ;
vardef chem_rot (expr n, d) =
    chem_rotation := d ;
enddef ;
vardef chem_adj (expr n, d) =
    chem_adjacent := d ;
enddef ;
vardef chem_sub (expr n, d) =
    chem_substituent := d ;
enddef ;
vardef chem_dir (expr n, d) =
    if n = 1 :
        chem_direction_p := (origin - 2*center(chem_b_path[n] rotated chem_ang(n,d+1))) ;
        currentpicture := currentpicture shifted chem_direction_p ;
        chem_shift := chem_shift + chem_direction_p ;
    fi ;
enddef ;
vardef chem_mov (expr n, d) =
    if d = 0 :
        currentpicture := currentpicture shifted - chem_shift ;
        chem_shift := origin ;
    else :
        chem_move_p := (origin - 2*center(chem_b_path[n] rotated chem_ang(n,d+chem_initialmov[n]))) ;
        currentpicture := currentpicture shifted chem_move_p ;
        chem_shift := chem_shift + chem_move_p ;
    fi ;
enddef ;
vardef chem_off (expr n, d) =
    if (d = 1) or (d = 2) or (d = 8) :     % positive
        currentpicture := currentpicture shifted (-chem_setting_offset,0) ;
        chem_shift := chem_shift + (-chem_setting_offset,0)
    elseif (d = 4) or (d = 5) or (d = 6) : % negative
        currentpicture := currentpicture shifted ( chem_setting_offset,0) ;
        chem_shift := chem_shift + ( chem_setting_offset,0)
    fi ;
enddef ;

vardef chem_set(expr n, m) =
    if chem_adjacent > 0 :
        chem_adjacent_d := xpart chem_b_zero[n] + xpart chem_b_zero[m] ;
        if     chem_adjacent = 1 : chem_adjacent_p := (-chem_adjacent_d, 0) ;
        elseif chem_adjacent = 2 : chem_adjacent_p := (0, -chem_adjacent_d) ;
        elseif chem_adjacent = 3 : chem_adjacent_p := ( chem_adjacent_d, 0) ;
        elseif chem_adjacent = 4 : chem_adjacent_p := (0,  chem_adjacent_d) ;
        else                     : chem_adjacent_p := origin ;
        fi ;
        currentpicture := currentpicture shifted chem_adjacent_p ;
        chem_shift := chem_shift + chem_adjacent_p ;
        chem_adjacent := 0 ;
    fi ;
    if chem_substituent > 0 :
        if m = 1 :
            chem_substituent_d := xpart chem_crz_zero[n] + chem_substituent_offset ;
        else :
            chem_substituent_d := xpart chem_crz_zero[n] +  xpart chem_b_zero[m] ;
        fi ;
        if     chem_substituent = 1 : chem_substituent_p := (-chem_substituent_d, 0) ; % - ?
        elseif chem_substituent = 2 : chem_substituent_p := (0,  chem_substituent_d) ;
        elseif chem_substituent = 3 : chem_substituent_p := ( chem_substituent_d, 0) ;
        elseif chem_substituent = 4 : chem_substituent_p := (0, -chem_substituent_d) ;
        else                        : chem_substituent_p := origin ;
        fi ;
        currentpicture := currentpicture shifted chem_substituent_p ;
        chem_shift := chem_shift + chem_substituent_p ;
        chem_substituent := 0 ;
    fi ;
    chem_rotation := chem_initialrot[m] ;
enddef ;

vardef chem_draw (expr n, path_fragment, from_point, to_point, linewidth, linecolor) =
    for i:=from_point upto to_point:
        draw (path_fragment rotated chem_ang(n,i)) withpen pencircle scaled linewidth withcolor linecolor ;
    endfor ;
enddef ;
vardef chem_fill (expr n, path_fragment, from_point, to_point, linewidth, linecolor) =
    for i:=from_point upto to_point:
        fill (path_fragment rotated chem_ang(n,i)) withpen pencircle scaled 0 withcolor linecolor ;
    endfor ;
enddef ;

vardef chem_dashed_normal (expr n, path_fragment, from_point, to_point, linewidth, linecolor) =
    for i:=from_point upto to_point:
        draw (path_fragment rotated chem_ang(n,i)) withpen pencircle scaled linewidth withcolor linecolor dashed evenly ;
    endfor ;
enddef ;
vardef chem_dashed_connected (expr n, path_fragment, from_point, to_point, linewidth, linecolor) =
    draw for i:=from_point upto to_point:
        (path_fragment rotated chem_ang(n,i)) if i < to_point : -- fi
    endfor withpen pencircle scaled linewidth withcolor linecolor dashed evenly ;
enddef ;
vardef chem_draw_dot (expr n, path_fragment, from_point, to_point, linewidth, linecolor) =
    for i:=from_point upto to_point:
        draw (path_fragment rotated chem_ang(n,i)) withpen pencircle scaled (chem_dot_factor*linewidth) withcolor linecolor ;
    endfor ;
enddef ;
vardef chem_draw_fixed (expr n, path_fragment, linewidth, linecolor) =
    draw (path_fragment rotated chem_ang(n,1)) withpen pencircle scaled linewidth withcolor linecolor ;
enddef ;
vardef chem_draw_arrow (expr n, path_fragment, from_point, to_point, linewidth, linecolor) =
    for i:=from_point upto to_point:
        drawarrow (path_fragment rotated chem_ang(n,i)) withpen pencircle scaled linewidth withcolor linecolor ;
    endfor ;
enddef ;
vardef chem_draw_vertical (expr n, path_fragment, from_point, to_point, linewidth, linecolor) =
    % quite special
    for i:=from_point upto to_point:
        draw (path_fragment shifted (chem_b_zero[n] rotated chem_ang(n,i))) withpen pencircle scaled linewidth withcolor linecolor ;
    endfor ;
enddef ;

picture chem_stack_p[] ;
pair chem_stack_shift[] ;

vardef chem_save =
    chem_stack_n := chem_stack_n + 1 ;
    chem_stack_p[chem_stack_n] := currentpicture ;
    chem_stack_shift[chem_stack_n] := chem_shift ;
    chem_shift := origin ;
% chem_adjacent := 0 ;
% chem_substituent := 0 ;
% chem_rotation := 1 ;
    currentpicture := nullpicture ;
enddef ;
vardef chem_restore =
    if chem_stack_n > 0 :
        currentpicture := currentpicture shifted - chem_shift ;
        addto chem_stack_p[chem_stack_n] also currentpicture ;
        currentpicture := chem_stack_p[chem_stack_n] ;
        chem_stack_p[chem_stack_n] := nullpicture ;
        chem_shift := chem_stack_shift[chem_stack_n] ;
        chem_stack_n := chem_stack_n - 1 ;
    fi ;
enddef ;

def chem_init_some(expr n, ratio, start, initialrot, initialmov)  =
    chem_width     [n] := ratio * chem_base_width * chem_setting_scale ;
    chem_angle     [n] := 360/abs(n) ;
    chem_start     [n] := start ;
    chem_initialrot[n] := initialrot ;
    chem_initialmov[n] := initialmov ;
    chem_b_zero    [n] := (chem_width[n],0) rotated (chem_angle[n]/2) ;
    chem_n_zero    [n] := (chem_text_min*chem_width[n],0) rotated (chem_angle[n]/2) ;
    chem_r_max     [n] := chem_radical_max*chem_b_zero[n] ;
    chem_r_path    [n] := chem_b_zero[n] -- chem_r_max[n] ;
    chem_mr_path   [n] := chem_r_path [n] rotatedaround(chem_b_zero[n], (180-chem_angle[n])/2) ;
    chem_pr_path   [n] := chem_r_path [n] rotatedaround(chem_b_zero[n],-(180-chem_angle[n])/2) ;
    chem_r_zero    [n] := point 1 of chem_r_path [n] ;
    chem_mr_zero   [n] := point 1 of chem_mr_path[n] ;
    chem_pr_zero   [n] := point 1 of chem_pr_path[n] ;
    chem_crz_zero  [n] := point 1 of (chem_r_path[n] enlonged chem_center_offset) ;
    chem_au_path   [n] := subpath (0.2,0.8) of (chem_r_max[n] -- (chem_r_max[n] rotated chem_angle[n])) ;
    chem_ad_path   [n] := reverse(chem_au_path[n]) ;
    chem_rt_zero   [n] := (((chem_radical_max+chem_radical_min)/2)*chem_width[n],0) rotated (chem_angle[n]/2) ;
    chem_rtt_zero  [n] := chem_rt_zero[n] rotated + 10 ;
    chem_rbt_zero  [n] := chem_rt_zero[n] rotated - 10 ;
    chem_b_path    [n] := reverse(chem_b_zero[n] -- (chem_b_zero[n] rotated -chem_angle[n])) ;
    chem_bx_path   [n] := reverse(chem_b_zero[n] -- (chem_b_zero[n] rotated -chem_angle[n])) ; % ?
    chem_sb_path   [n] := subpath (0.25,0.75) of chem_b_path[n] ;
    chem_s_path    [n] := point 0 of chem_b_path[n] -- point 0 of (chem_b_path[n] rotated (2chem_angle[n])) ;
    chem_ss_path   [n] := subpath (0.25,0.75) of (chem_s_path[n]) ;
    chem_pss_path  [n] := subpath (0.00,0.75) of (chem_s_path[n]) ;
    chem_mss_path  [n] := subpath (0.25,1.00) of (chem_s_path[n]) ;
    chem_mid_zero  [n] := origin shifted (-.25chem_width[n],0) ;
    chem_midst_path[n] := chem_mid_zero[n] -- (chem_width[n],0) rotated ( chem_angle[n] + chem_angle[n]/2) ;
    chem_midsb_path[n] := chem_mid_zero[n] -- (chem_width[n],0) rotated (-chem_angle[n] - chem_angle[n]/2) ;
    chem_midt_path [n] := subpath (0.25,1.00) of chem_midst_path [n] ;
    chem_midb_path [n] := subpath (0.25,1.00) of chem_midsb_path [n] ;
    chem_msb_path  [n] := subpath (0.00,0.75) of chem_b_path[n] ;
    chem_psb_path  [n] := subpath (0.25,1.00) of chem_b_path[n] ;
    chem_dbl_path  [n] := chem_sb_path[n] shifted - (0.05[origin,center chem_sb_path[n]]) ; % parallel
    chem_dbr_path  [n] := chem_sb_path[n] shifted + (0.05[origin,center chem_sb_path[n]]) ;
    chem_eb_path   [n] := chem_sb_path[n] shifted - (0.25[origin,center chem_sb_path[n]]) ;
    chem_sr_path   [n] := chem_radical_min*chem_b_zero[n] -- chem_r_max[n] ;
    chem_rl_path   [n] := chem_r_path[n]  paralleled  (chem_base_width/20) ;
    chem_rr_path   [n] := chem_r_path[n]  paralleled -(chem_base_width/20) ;
    chem_srl_path  [n] := chem_sr_path[n] paralleled  (chem_base_width/20)  ;
    chem_srr_path  [n] := chem_sr_path[n] paralleled -(chem_base_width/20)  ;
    chem_br_path   [n] := point 1 of chem_sb_path[n] --
        point 0 of chem_sb_path[n] rotatedaround(point 1 of chem_sb_path[n], -4) --
        point 0 of chem_sb_path[n] rotatedaround(point 1 of chem_sb_path[n],  4) -- cycle ;
    chem_rb_path   [n] := chem_b_zero[n] -- chem_r_max[n] rotated -2 -- chem_r_max[n] -- chem_r_max[n] rotated 2 --  cycle ;
    chem_mrb_path  [n] := chem_rb_path[n] rotatedaround(chem_b_zero[n], (180-chem_angle[n])/2) ;
    chem_prb_path  [n] := chem_rb_path[n] rotatedaround(chem_b_zero[n],-(180-chem_angle[n])/2) ;
    chem_msr_path  [n] := chem_sr_path[n] rotatedaround(chem_b_zero[n], (180-chem_angle[n])/2) ;
    chem_psr_path  [n] := chem_sr_path[n] rotatedaround(chem_b_zero[n],-(180-chem_angle[n])/2) ;
    % not yet ok:
%     chem_c_path    [n] := subpath (30/45, -30/45) of (fullcircle            scaled (1.25*chem_circle_radius*chem_width[n]));
%     chem_cc_path   [n] := subpath (30/45,8-30/45) of (fullcircle rotated 90 scaled (1.25*chem_circle_radius*chem_width[n]));
    chem_c_path    [n] := subpath (30/45, -30/45) of (fullcircle            scaled (chem_width[n]));
    chem_cc_path   [n] := subpath (30/45,8-30/45) of (fullcircle rotated 90 scaled (chem_width[n]));
enddef ;

def chem_init_three      = chem_init_some(3,30/52  ,-60,1,2) ; enddef ; % 60
def chem_init_four       = chem_init_some(4,30/42.5,  0,1,0) ; enddef ; % 45
def chem_init_five       = chem_init_some(5,30/35  ,  0,1,0) ; enddef ; % 36
def chem_init_six        = chem_init_some(6, 1     ,  0,1,0) ; enddef ; % 30
def chem_init_eight      = chem_init_some(8,30/22.5,  0,1,0) ; enddef ; % 22.5

% bb R -R R Z -RZ +RZ

def chem_init_some_front(expr n, ratio, start, initialrot, initialmov) =
    chem_init_some(n, ratio, start, initialrot, initialmov) ;
    chem_bb_path [n] := chem_b_path[n] rotated -chem_angle[n] -- chem_b_path[n] -- chem_b_path[n] rotated chem_angle[n] --
                       (reverse(chem_b_path[n] shortened (chem_base_width/20))) paralleled (chem_base_width/20) --
                        cycle ;
    chem_r_max   [n] := chem_radical_max*chem_b_zero[n] ;
    chem_mr_path [n] := origin -- origin shifted (0,-.25chem_base_width) ;
    chem_pr_path [n] := origin -- origin shifted (0, .25*chem_base_width) ;
    chem_r_path  [n] := point 1 of chem_mr_path[n] -- point 1 of chem_pr_path[n] ;
    chem_mr_zero [n] := point 1 of chem_mr_path[n] ;
    chem_pr_zero [n] := point 1 of chem_pr_path[n] ;
enddef ;

def chem_init_five_front = chem_init_some_front(-5,30/35,0,2,0) ; enddef ; % 36
def chem_init_six_front  = chem_init_some_front(-6, 1   ,0,2,0) ; enddef ; % 30

vardef chem_init_one =
    chem_width     [1] := .75 * chem_base_width * chem_setting_scale ;
    chem_angle     [1] := 360/8 ;
    chem_start     [1] := 0 ;
    chem_initialrot[1] := 1 ;
    chem_initialmov[1] := 1 ;
    chem_b_zero    [1] := (1.75*chem_width[1],0) ;
    chem_r_min     [1] := chem_radical_min*chem_b_zero[1] ;
    chem_r_max     [1] := chem_radical_max*chem_b_zero[1] ;
    chem_r_path    [1] := (.5*chem_width[1],0) -- (1.25*chem_width[1],0) ;
    chem_r_zero    [1] := point 1 of chem_r_path [1] ;
    chem_b_path    [1] := chem_r_path[1] rotated + (chem_angle[1]) ; % used for move here
    chem_b_zero    [1] := chem_r_zero[1] ;
    chem_crz_zero  [1] := chem_r_zero[1] enlonged chem_center_offset ;
    chem_e_path    [1] := (.5*chem_width[1],-.25*chem_width[1]) -- (.5*chem_width[1],.25*chem_width[1]) ;
    chem_sb_path   [1] := chem_r_path [1] ;
    chem_msb_path  [1] := chem_r_path [1] shifted (0,-.1chem_width[1]) ;
    chem_psb_path  [1] := chem_r_path [1] shifted (0, .1chem_width[1]) ;
    chem_ddt_path  [1] := subpath(0,.4) of chem_r_path [1] ;
    chem_ddb_path  [1] := subpath(.6,1) of chem_r_path [1] ;
    chem_ldt_path  [1] := chem_ddt_path [1] shifted (0,-.1chem_width[1]) ; % parallel
    chem_ldb_path  [1] := chem_ddb_path [1] shifted (0,-.1chem_width[1]) ;
    chem_rdt_path  [1] := chem_ddt_path [1] shifted (0, .1chem_width[1]) ;
    chem_rdb_path  [1] := chem_ddb_path [1] shifted (0, .1chem_width[1]) ;
    save pr ; pair pr[] ;
    pr0 := point 0 of chem_r_path[1] ;
    pr1 := point 1 of chem_r_path[1] ;
    chem_bb_path   [1] := pr0 -- (pr1 rotatedaround(pr0,-chem_bb_angle)) -- (pr1 rotatedaround(pr0,chem_bb_angle)) -- cycle ;
    chem_oe_path   [1] := ((-20,0)--(10,0){up}..(20,10)..(30,0)..(40,-10)..(50.0,0)..(60,10)..(70,0)..(80,-10)..{up}(90,0)--(120,0))
        xsized (.75*chem_width[1]) shifted pr0 ;
    chem_rt_zero   [1] := point .5 of chem_r_path[1] ;
    chem_rtt_zero  [1] := chem_rt_zero[1] rotated + (chem_angle[1]/2) ;
    chem_rbt_zero  [1] := chem_rt_zero[1] rotated - (chem_angle[1]/2) ;
    % added by Alan Braslau (adapted to use shared variables):
    save p ; pair p[] ;
    p0 := pr1 rotatedaround(pr0, -chem_bd_angle) ;
    p1 := pr1 rotatedaround(pr0, +chem_bd_angle) ;
    p2 := p0 shifted - pr1 ;
    p3 := p1 shifted - pr1 ;
    chem_bd_path   [1] :=
        p0 -- p1 for i=chem_bd_n downto 0 :
            -- p2 shifted (i/chem_bd_n)[pr1,pr0]
            -- p3 shifted (i/chem_bd_n)[pr1,pr0]
        endfor ;
    chem_bw_path   [1] :=
        for i=0 upto chem_bw_n - 1 :
            ((i)    /chem_bw_n)[pr0,pr1] .. ((i+.25)/chem_bw_n)[pr0,pr1] shifted  p2 ..
            ((i+.50)/chem_bw_n)[pr0,pr1] .. ((i+.75)/chem_bw_n)[pr0,pr1] shifted -p2 ..
        endfor pr1 ;
enddef ;

def chem_init_all =
    chem_init_one ;
    chem_init_three ;
    chem_init_four ;
    chem_init_five ;
    chem_init_six ;
    chem_init_eight ;
    chem_init_five_front ;
    chem_init_six_front ;
enddef ;

chem_init_all ;