MouseInput Deltas while mouse not grabbed

If the system mouse cursor is visible (mouse is not grabbed) the getXDelta and getYDelta methods return the absolute x and y values of the mouse.

Is this necessary? Does anyone rely on that bahaviour? Or is it just a missing feature?

I'd like to change that to behave like with grabbed cursor (similar to the AWT implementation, which stores the old value of the mouse pointer and computes deltas).

Any objections?