function closestEdge(x,y,w,h) {
        var topEdgeDist = distMetric(x,y,w/2,0);
        var bottomEdgeDist = distMetric(x,y,w/2,h);
        var leftEdgeDist = distMetric(x,y,0,h/2);
        var rightEdgeDist = distMetric(x,y,w,h/2);
        var min = Math.min(topEdgeDist,bottomEdgeDist,leftEdgeDist,rightEdgeDist);
        switch (min) {
            case leftEdgeDist:
                return "left";
            case rightEdgeDist:
                return "right";
            case topEdgeDist:
                return "top";
            case bottomEdgeDist:
                return "bottom";
        }
}

function distMetric(x,y,x2,y2) {
    var xDiff = x - x2;
    var yDiff = y - y2;
    return (xDiff * xDiff) + (yDiff * yDiff);
}