collision test

A line:

ctx.beginPath();
ctx.moveTo(10, 10);
ctx.lineTo(100, 100);
ctx.stroke()
ctx.closePath();
api.mousemove(function(x,y) {
    console.log(x,y);
});

A draggable ball:

function DragBall(x,y) {
    if ( !(this instanceof arguments.callee) ) 
        return new DragBall(x, y); 

    var x = 0;
    var y = 0;
    var mousedown = false;
    var rad = 10;
    var that = this;

    this.draw = function() {
        api.circle(x, y, rad);
    }

    api.mousemove(function(xx, yy) {
        if (mousedown) {
            console.log("moving to ", xx, yy);
            x = xx;
            y = yy;
            that.draw();
        }
    });

    api.mousedown(function() {
        mousedown = true;
    });

    api.mouseup(function() {
        mousedown = false;
    });

    this.draw();
}

d = new DragBall(30, 30);

$(canvas).mousedown(function(evt) {
  mousedown = true;
});

$(canvas).mouseup(function(evt) {
  mousedown = false;
});

function drawball(x, y) {
  ctx.beginPath();
  ctx.arc(x, y, 10, 0, Math.PI*2, true); 
  ctx.closePath();
  ctx.fill();
}