Snap.svg - drag event handler

Question

Question is about the onstart event handler for Element.drag in the newly announced Snap.svg.

The intention of the code below is to register event handlers for the start and stop of a drag (onstart/onstop) on an svg object.

        var s = Snap(800,600);

        var bigCircle = s.circle(300,150,100);

        bigCircle.drag(null,
                function(){
                    console.log("Move started");
                },
                function(){
                    console.log("Move stopped");
                }
        );

The console messages work fine on drag start and stop, but the null overrides the default onmove function - resulting in no actual drag happening. How do I pass something that says "I don't want to mess with the default onmove"?

(Note: I'd prefer to register an event handler by means of assignment, like the familiar onClick, but that's a different matter.)

---

Note added after few hours: The Raphael.js documentation and examples provide some clues. At least now I know how to pass in a proper function for onmove that provides the default move behavior:

        var s = Snap(800,600);

        var bigCircle = s.circle(300,150,100);

        start = function() {
            this.ox = parseInt(this.attr("cx"));
            this.oy = parseInt(this.attr("cy"));
            console.log("Start move, ox=" + this.ox + ", oy=" + this.oy);
        }

        move = function(dx, dy) {
            this.attr({"cx": this.ox + dx, "cy": this.oy + dy});
        }

        stop = function() {
            this.ox = parseInt(this.attr("cx"));
            this.oy = parseInt(this.attr("cy"));
            console.log("Stop move, ox=" + this.ox + ", oy=" + this.oy);
        }

        bigCircle.drag(move, start, stop);

Answer 1

I'm not sure if I'm misunderstanding what you exactly want...don't you want to implement the drag ?

So for example...

var s = Snap(400,400);
var bigCircle = s.circle(150, 150, 100);

var moveFunc = function (dx, dy, posx, posy) {
    this.attr( { cx: posx , cy: posy } ); // basic drag, you would want to adjust to take care of where you grab etc.
};

bigCircle.drag( moveFunc,
            function(){
                console.log("Move started");
            },
            function(){
                console.log("Move stopped");
            }
    );

JSBin here http://jsbin.com/akoCAkA/1/edit?html,js,output