ExtJS 4.x Grid Plugin to add ToolTips to each Cell in a Column with Process Config Function snippet for a Grid Panel.

CellToolTip.js

Ext.define('Ext.grid.plugin.CellToolTip', {
    extend: 'Ext.AbstractPlugin',
    alias: 'plugin.CellQTip',
    config: {
        debug: false
    },

    init: function(grid) {

        // You may not need the scope, but if you do, this binding will
        // allow to preserve the scope configured in the column...
        var pluginRenderer = Ext.Function.bind(this.renderer, this);

        Ext.each(grid.query('gridcolumn'), function(col) {
            var renderer = col.renderer;
            col.renderer = renderer ? Ext.Function.createSequence(renderer, pluginRenderer) : pluginRenderer;
        });
    },

    renderer: function(value, metaData, record, rowIndex, colIndex, store, view) {
        var col = view.getGridColumns()[colIndex];
        var fn = this[col.itemId];
        if (fn) {
            metaData.tdAttr = fn(value, metaData, record, rowIndex, colIndex, store, view);
        }     
        return value;
    }
});

Process Config Function Snippet.js

processBlobInfoGridPanel: function(config) {
    var ttp = Ext.create('Ext.grid.plugin.CellToolTip', {
        createdOn: function(value, metaData, record, rowIndex, colIndex, store, view) { return 'data-qtip="' + value.toUTCString() + '"'; },
        contentType: function(value, metaData, record, rowIndex, colIndex, store, view) { return 'data-qtip="Hello World!"'; },
        byteSize: function(value, metaData, record, rowIndex, colIndex, store, view) { return 'data-qtip="' + value + ' bytes"'; }
    });
    config.plugins = [ttp];
    return config;
},