Flechas con RaphaelJS

Me encontré con que no hay ningún método para dibujar flechas en raphaelJS, así que me puse las pilas y programé uno:

 /**
   * Returns a path in form of an arrow
   * @param arrowSize is the size of the arrow end. Defaults to 10 pixels.
   */
 Raphael.fn.arrow = function(x1, y1, x2, y2, arrowSize) {
  var arrowSize = arrowSize || 10
  var l = Math.sqrt( Math.pow( x2 - x1, 2 ) + Math.pow( y2 - y1, 2 ) )  
  var xStep = (x2 - x1) / l
  var yStep = (y2 - y1) / l

  // arrow point ends
  var arrX1 = x2 + arrowSize * (yStep - xStep) / 2
  var arrY1 = y2 + arrowSize * (-xStep - yStep) / 2 
  var arrX2 = x2 + arrowSize * (-yStep - xStep) / 2
  var arrY2 = y2 + arrowSize * (xStep - yStep) / 2
        
  var path = ["M", x1, y1, "L", x2, y2, //main line
      "M", arrX1, arrY1, "L", x2, y2, "L", arrX2, arrY2] //arrow end
  
  return this.path(path.join(" ")) 
 }

Para usarlo hay que hacer:

var r = Raphael(....)
.....
var arrow = r.arrow(150,100,250,300)