There are a bug when we have a window with options :

- constrainHeader: true
- draggable: true
- resizable: true

Then the bug is when you move the window :
- if you resize by reducing the window size, you can move the window outside the frame.
- if you resize by enlarging the window size, you can not move the window on the frame's borders.

Example to reproduce (from the documentation sample):

Code:
Ext.create('Ext.window.Window', {
    title: 'Hello',
    height: 200,
    width: 400,
    layout: 'fit',
    constrainHeader: true,
    draggable: true,
    resizable: true,
    items: {  // Let's put an empty grid in just to illustrate fit layout
        xtype: 'grid',
        border: false,
        columns: [{header: 'World'}],                 // One header just for show. There's no data,
        store: Ext.create('Ext.data.ArrayStore', {}) // A dummy empty data store
    }
}).show();