If draggable element has position fixed then autoScroll works wrong

[bumbu]

Here is the example http://jsfiddle.net/bumbu/qjudjkxa/

Everything works right if page is not scrolled, but if you:

• scroll the page to bottom (or by any meaningful amount)
• to drag any element
  then container is automatically scrolled to top.

A video example is on youtube. You can see that when page is not scrolled - autoscroll works fine, it is scrolled then no matter which way I drag it will scroll to the top.

This happens because in autoScrollMove mousePointer uses clientX/Y values which are relative to visible viewport of the browser but getElementRect takes in account page scroll (which shouldn't be used for fixed elements).

If I try to ignore scroll values from getElementRect then autoScroll and restriction do not work or work badly.