code: function(n){
      var octx = this.octx,
        s = n.series;
  
      if (s.mouse.lineColor) {
        octx.save();
        octx.lineWidth = (s.points ? s.points.lineWidth : 1);
        octx.strokeStyle = s.mouse.lineColor;
        octx.fillStyle = this.processColor(s.mouse.fillColor || '#ffffff', {opacity: s.mouse.fillOpacity});
        octx.translate(this.plotOffset.left, this.plotOffset.top);
  
        if (!this.hit.executeOnType(s, 'drawHit', n)) {
          var
            xa = n.xaxis,
            ya = n.yaxis;
  
          octx.beginPath();
            // TODO fix this (points) should move to general testable graph mixin
            octx.arc(xa.d2p(n.x), ya.d2p(n.y), s.points.hitRadius || s.points.radius || s.mouse.radius, 0, 2 * Math.PI, true);
            octx.fill();
            octx.stroke();
          octx.closePath();
        }
        octx.restore();
        this.clip(octx);
      }
      this.prevHit = n;
    }
docs: Updates the mouse tracking point on the overlay.