/// <summary>
/// Unites two given polygons into one and returns it. The two polygons
/// are deleted. Optionally applies a cleanup to the new polygon.
/// </summary>
/// <param name="unionEdges">the edges of the new united polygon</param>
/// <param name="polygon1">the first of the polygons that are to be united</param>
/// <param name="polygon2">the second of the polygons that are to be united</param>
/// <param name="allowCleanUp">if the edges of the united polygon should
/// be cleaned up</param>
/// <returns>the new united polygon</returns>
private Polygon ApplyPolygonUnion(List<Edge> unionEdges, Polygon polygon1, Polygon polygon2, bool allowCleanUp)
{
Debug.Assert(! polygon1.CanBeCleanedUp(), "Cannot unite with a dirty polygon!");
Debug.Assert(!polygon2.CanBeCleanedUp(), "Cannot unite with a dirty polygon!");
Polygon unionPolygon = new Polygon(unionEdges);
unionPolygon.ImposeOwnership();
polygon1.Delete(true);
RemovePolygon(polygon1);
polygon2.Delete(true);
RemovePolygon(polygon2);
AddPolygon(unionPolygon);
if (allowCleanUp) unionPolygon.CleanUp(true);
return unionPolygon;
}
