1 d3.svg.diagonal = function() {

     2   var source = d3_svg_chordSource,

     3       target = d3_svg_chordTarget,

     4       projection = d3_svg_diagonalProjection;

     5 

     6   function diagonal(d, i) {

     7     var p0 = source.call(this, d, i),

     8         p3 = target.call(this, d, i),

     9         m = (p0.y + p3.y) / 2,

    10         p = [p0, {x: p0.x, y: m}, {x: p3.x, y: m}, p3];

    11     p = p.map(projection);

    12     return "M" + p[0] + "C" + p[1] + " " + p[2] + " " + p[3];

    13   }

    14 

    15   diagonal.source = function(x) {

    16     if (!arguments.length) return source;

    17     source = d3.functor(x);

    18     return diagonal;

    19   };

    20 

    21   diagonal.target = function(x) {

    22     if (!arguments.length) return target;

    23     target = d3.functor(x);

    24     return diagonal;

    25   };

    26 

    27   diagonal.projection = function(x) {

    28     if (!arguments.length) return projection;

    29     projection = x;

    30     return diagonal;

    31   };

    32 

    33   return diagonal;

    34 };

    35 

    36 function d3_svg_diagonalProjection(d) {

    37   return [d.x, d.y];

    38 }