When you contain a draggable element, the actual element itself will be contained to whatever containment you specify. This is not desirable though, it would be better if the handle be contained instead of the element itself. If you use a handle (without containment) it is very easy to drag the handle above the window and if you drop it there, the element will be 'lost' in the sense that you can't drag it anymore.
Specifying a containment resolves this issue, but if you want the handle to be outside the element (which I would like in my application) the issue remains. Another issue I have in that application is that I use draggable elements as windows (similar to the windows in photoshop). If you specify a containment, you can't drag the elements off-screen which makes the screen full and cluttered. If the handle would be contained, you could drag the window off-sreen at least a little bit without 'losing' them'
So my question is: is it possible to specify the containment so that it applies to the handle of the draggable element instead of the element? If not I will file this as a bug.