ExtJs manually firing Click event, button param is different from mouse click

You must use the fireEvent function like that:

var myBtn = Ext.getCmp('#idLogin button');

myBtn.fireEvent('click', myBtn);

Give it a try.

Because the button click event is a synthetic event fired by the framework. It passes along the button instance and an event object. fireEvent means "notify any subscribers that this event has happened, with these arguments", not "trigger a click event on the underlying button".

So you'd need to use:

button.fireEvent('click', button);

However, this doesn't really make sense, you're just adding an extra layer of indirection.

Why not abstract it out:

Ext.define('My.controller.Login', {
    extend: 'Ext.app.Controller',

    init: function(application) {
        this.control({
            "#idLogin button": {click: this.onButton},
            "#idLogin form > *": {specialkey: this.onKey}
        });
    },

    onButton: function(button, e, eOpts) {
        this.doWindowFoo();
    },

    onKey: function (field, el) {
        if (el.getKey() == Ext.EventObject.ENTER) //ENTER key performs Login
            this.doWindowFoo();
    },

    doWindowFoo: function() {
        // Assumes the window has an id idLogin, there are several other ways to get a reference
        var win = Ext.getCmp('idLogin');
    }
});

Use:

var button= Ext.getCmp('#idLogin button');    
button.fireHandler();