When trying to quickly move an arc, I get a lots of null point exceptions although it performs correctly at the end.
The helper drawing also isn't painted.
The quick move factory relied on repeating MANY times move and unmove operations. However, those operations introduce small double error representation which end up by changing the element's hashcode (this is a serious problem).
Fixed it by always creating clones to draw and throw them away immediately.
Oh! Fixed on revision 1571.