Cubic bezier curves with fabric.js renderer

fabricBezierCurve.js

var CubicBezier = function(canvas, opts){
	if(!opts) opts = {};

	this.start = opts.start || new Vec2(100,100);
	this.end   = opts.end   || new Vec2(400, 400);

	this.c1    = opts.c1    || new Vec2(100, 300);
	this.c2 	 = opts.c2 		|| new Vec2(300, 100);

	this.curve = new fabric.Path( this.toSVGPath() );

	this.controlCurve = new fabric.Path( this.toControlPath() );

	this.curve.selectable = this.controlCurve.selectable = false;
	this.curve.fill	 = this.controlCurve.fill = 'none'
	this.curve.stroke= 'black';

	this.controlCurve.stroke 		= 'blue';
	this.controlCurve.strokeDashArray = [5, 5];

	canvas.add( this.curve );
	canvas.renderAll();
	
	// this.renderControlPoints( canvas );

	canvas.calcOffset();

}

CubicBezier.prototype = {

	toSVGPath : function(){
		var str  = "M"+this.start.toString();
				str += "C"+this.c1.toString();
				str += this.c2.toString();
				str += this.end.toString();

		return str
	},

	toControlPath : function(){
		var str  = "M"+this.start.toString();
				str += "L"+this.c1.toString();
				str += "L"+this.c2.toString();
				str += "L"+this.end.toString();

		return str
	},

	renderControlPoints : function(canvas){
		var scope = this;

		var r = 10;
		var points = [
			new fabric.Circle({ top: this.start.y, left: this.start.x,radius:r, as : 'start' }),
			new fabric.Circle({ top: this.end.y, 	 left: this.end.x, 	radius:r, as : 'end' }),
			new fabric.Circle({ top: this.c1.y,    left: this.c1.x,		radius:r, as : 'c1' }),
			new fabric.Circle({ top: this.c2.y, 	 left: this.c2.x, 	radius:r, as : 'c2' })
		];

		points.forEach( function(p){
			p.fill =  '#f55';
			p.stroke = "#2B436E"
			p.hasControls = p.hasBorder = false;
			p.belongsTo = scope;
			canvas.add(p);
		})
	},

	renderCurve : function(canvas){
		var dummyPath = new fabric.Path( this.toSVGPath() );
		this.curve.path = dummyPath.path;

		var dummyPath2 = new fabric.Path( this.toControlPath() );
		this.controlCurve.path = dummyPath2.path;

		// canvas.renderAll();
	},

}