Ext JS chart Tooltip not rendering under mouse pointer - extjs

Question

I am trying to add tooltips to my ExtJS chart. The tooltip is getting rendered but not under the mouse pointer. It is getting rendered near end of the page.
Ext.create('Ext.chart.Chart', {
renderTo: Ext.getBody(),
width: 470,
height: 300,
store: store,
axes: [{
type: 'Numeric',
minimum: 0,
minorTickSteps: 0,
maximum: 150,
position: 'left',
fields: ['lineY', 'greenY', 'yellowY', 'redY'],
title: 'Buffer Penetration'
}, {
type: 'Numeric',
position: 'bottom',
fields: ['lineX', 'areaX'],
title: 'Critical Chain Comp'
}],
series: [
{
type: 'area',
axis: 'left',
xField: 'areaX',
yField: ['redY']
},
{
type: 'area',
axis: 'left',
xField: 'areaX',
yField: ['yellowY']
},
{
type: 'area',
axis: 'left',
xField: 'areaX',
yField: ['greenY']
},
{
type: 'line',
axis: 'left',
fill: false,
// tip: 'This is a tip',
xField: 'lineX',
yField: 'lineY',
tips: {
trackMouse: true,
width: 140,
height: 28,
renderer: function (storeItem, item) {
// calculate and display percentage on hover
this.setTitle("Tooltip Text");
}
}
}
]
});
I have my code here : http://jsfiddle.net/Abhishek1191/vdazU/1076/
I feel like I am doing something silly here or maybe there is some issue with the ExtJS library I am using. Help would be highly appreciated