sortable: check over change before calling strategy

[trungdo-epi]

useSortable should check if over has change before calling strategy.

https://github.com/clauderic/dnd-kit/blob/master/packages/sortable/src/hooks/useSortable.ts#L84

Currently, strategy is called for every rerender of DndContext.

[clauderic]

Can you elaborate on why this is a problem for your use-case?

[trungdo-epi]

If I am not mistaken.

Currently, DndContext is rerendered on every drag move event. https://github.com/clauderic/dnd-kit/blob/master/packages/core/src/components/DndContext/DndContext.tsx#L359

But not every move event causes overId to change, i.e. over event is less frequent than move event. https://github.com/clauderic/dnd-kit/blob/master/packages/core/src/components/DndContext/DndContext.tsx#L278

If over event does not happen, then there is no need to recalculate transformation of droppable containers.

[VArsenyan]

any update @clauderic ?