It's a pity that the jquery-ui team doesn't support cross-window dragging [1] and it's great that you fix that for many people who need that!
I wonder how hard it is to make your solution work for sortables as well. I tried different possibilities now but didn't find a well working solution.
This fiddle shows the offset between the mouse pointer and the dragged element without your library included:
http://jsfiddle.net/e2kgbcbz/10
It's a pity that the jquery-ui team doesn't support cross-window dragging [1] and it's great that you fix that for many people who need that! I wonder how hard it is to make your solution work for sortables as well. I tried different possibilities now but didn't find a well working solution.
This fiddle shows the offset between the mouse pointer and the dragged element without your library included: http://jsfiddle.net/e2kgbcbz/10
This is with your library included: http://jsfiddle.net/e2kgbcbz/13
What do you think?
Best, Sandro
[1] - just as a reference: https://bugs.jqueryui.com/ticket/7925