Trying to avoid using clipper to merge polygons when they can be avoided.
Try to use the origional (potentially optermised shapes) if merging will produce not change the origional shape.
We do this in a couple of ways:
- We strip away any holes that don't intersect with an outline
- We skip merging outlines that dont intersect with any other shape and simple pass then through. This provides the added benefit/optimisation of using the specialised shapes instead of the generic polygon class where possible.