let () =
  let svg = Svg.new_svg_document ~width:480 ~height:180 () in

  Svg.add_rect svg
    ~x:0 ~y:0
    ~width:480
    ~height:180
    ~fill:"#fff"
    ~stroke:"#000"
    ~stroke_width:2.0
   ()
   ;

  Svg.add_line svg
    ~x1:45   ~y1:45
    ~x2:410  ~y2:45
    ~stroke:"#000"
    ~stroke_width:1.0
   ()
   ;

  Svg.add_line svg
    ~x1:45   ~y1:135
    ~x2:370  ~y2:135
    ~stroke:"#000"
    ~stroke_width:1.0
   ()
   ;

  Svg.add_line svg
    ~x1:55   ~y1:35
    ~x2:55   ~y2:145
    ~stroke:"#000"
    ~stroke_width:1.0
   ()
   ;

  Svg.add_circle svg
    ~cx:120.0
    ~cy:45.0
    ~r:5.6
    ~fill:"none"
    ~stroke:"#000"
    ~stroke_width:1.5
   ()
   ;

  Svg.add_text svg
    ~x:120
    ~y:35
    ~text:"C"
    ~font_size:"14px"
    ~fill:"#000"
   ()
   ;

  Svg.add_circle svg
    ~cx:98.0
    ~cy:135.0
    ~r:5.6
    ~fill:"none"
    ~stroke:"#000"
    ~stroke_width:1.5
   ()
   ;

  Svg.add_text svg
    ~x:92
    ~y:155
    ~text:"A"
    ~font_size:"14px"
    ~fill:"#000"
   ()
   ;

  Svg.add_circle svg
    ~cx:320.0
    ~cy:45.0
    ~r:5.6
    ~fill:"none"
    ~stroke:"#000"
    ~stroke_width:1.5
   ()
   ;

  Svg.add_text svg
    ~x:322
    ~y:35
    ~text:"D"
    ~font_size:"14px"
    ~fill:"#000"
   ()
   ;

  Svg.add_circle svg
    ~cx:238.0
    ~cy:135.0
    ~r:5.6
    ~fill:"none"
    ~stroke:"#000"
    ~stroke_width:1.5
   ()
   ;

  Svg.add_text svg
    ~x:232
    ~y:155
    ~text:"B"
    ~font_size:"14px"
    ~fill:"#000"
   ()
   ;

  Svg.add_circle svg
    ~cx:128.0
    ~cy:135.0
    ~r:5.6
    ~fill:"none"
    ~stroke:"#f00"
    ~stroke_width:1.5
   ()
   ;

  Svg.add_circle svg
    ~cx:178.0
    ~cy:45.0
    ~r:5.6
    ~fill:"none"
    ~stroke:"#0d0"
    ~stroke_width:1.6
   ()
   ;

  let m_def, start_marker, end_marker =
    Svg.make_marker ~marker_size:(10, 10) ~ref_pos:(5, 5)
      ~frag:begin
        let frag = Svg.new_fragment () in
        Svg.add_polygon frag
          ~points:[(2, 1); (8, 5); (2, 9)]
          ~fill:"black" ();
        (frag)
      end
  in
  Svg.add_defs svg [m_def];
  let _ = start_marker in
  Svg.add_line svg
    ~x1:128 ~y1:135
    ~x2:174 ~y2:53
    ~stroke:"#333"
    ~stroke_width:1.2
    ~attrs:[end_marker]
    ();

  Svg.finish_svg svg;
  Svg.print_svg_document svg;
;;