ENH: update Clipper2 to 1.5.2

Clipper2 has added a lot of features in the past 2 years, including "offset to polytree" which is very useful for expolygons.

jira: none
Change-Id: I6f51e243656312d8c7693e1c9f5c52cf2f0034d1

src/clipper2/Clipper2Lib/include/clipper2/clipper.engine.h

@@ -1,25 +1,19 @@
 /*******************************************************************************
 * Author    :  Angus Johnson                                                   *
-* Date      :  4 November 2022                                                 *
+* Date      :  17 September 2024                                               *
-* Website   :  http://www.angusj.com                                           *
+* Website   :  https://www.angusj.com                                          *
-* Copyright :  Angus Johnson 2010-2022                                         *
+* Copyright :  Angus Johnson 2010-2024                                         *
 * Purpose   :  This is the main polygon clipping module                        *
-* License   :  http://www.boost.org/LICENSE_1_0.txt                            *
+* License   :  https://www.boost.org/LICENSE_1_0.txt                           *
 *******************************************************************************/
 
 #ifndef CLIPPER_ENGINE_H
 #define CLIPPER_ENGINE_H
 
-constexpr auto CLIPPER2_VERSION = "1.0.6";
+#include "clipper2/clipper.core.h"
-
-#include <cstdlib>
 #include <queue>
-#include <stdexcept>
-#include <vector>
 #include <functional>
-#include <cstddef>
+#include <memory>
-#include <cstdint>
-#include "clipper.core.h"
 
 namespace Clipper2Lib {
 
@@ -29,15 +23,16 @@ namespace Clipper2Lib {
 	struct Vertex;
 	struct LocalMinima;
 	struct OutRec;
-	struct Joiner;
+	struct HorzSegment;
 
 	//Note: all clipping operations except for Difference are commutative.
-	enum class ClipType { None, Intersection, Union, Difference, Xor };
+	enum class ClipType { NoClip, Intersection, Union, Difference, Xor };
 
 	enum class PathType { Subject, Clip };
+	enum class JoinWith { NoJoin, Left, Right };
 
 	enum class VertexFlags : uint32_t {
-		None = 0, OpenStart = 1, OpenEnd = 2, LocalMax = 4, LocalMin = 8
+		Empty = 0, OpenStart = 1, OpenEnd = 2, LocalMax = 4, LocalMin = 8
 	};
 
 	constexpr enum VertexFlags operator &(enum VertexFlags a, enum VertexFlags b)
@@ -54,7 +49,7 @@ namespace Clipper2Lib {
 		Point64 pt;
 		Vertex* next = nullptr;
 		Vertex* prev = nullptr;
-		VertexFlags flags = VertexFlags::None;
+		VertexFlags flags = VertexFlags::Empty;
 	};
 
 	struct OutPt {
@@ -62,7 +57,7 @@ namespace Clipper2Lib {
 		OutPt*	next = nullptr;
 		OutPt*	prev = nullptr;
 		OutRec* outrec;
-		Joiner* joiner = nullptr;
+		HorzSegment* horz = nullptr;
 
 		OutPt(const Point64& pt_, OutRec* outrec_): pt(pt_), outrec(outrec_) {
 			next = this;
@@ -84,15 +79,21 @@ namespace Clipper2Lib {
 	struct OutRec {
 		size_t idx = 0;
 		OutRec* owner = nullptr;
-		OutRecList* splits = nullptr;
 		Active* front_edge = nullptr;
 		Active* back_edge = nullptr;
 		OutPt* pts = nullptr;
 		PolyPath* polypath = nullptr;
+		OutRecList* splits = nullptr;
+		OutRec* recursive_split = nullptr;
 		Rect64 bounds = {};
 		Path64 path;
 		bool is_open = false;
-		~OutRec() { if (splits) delete splits; };
+
+		~OutRec() {
+			if (splits) delete splits;
+			// nb: don't delete the split pointers
+			// as these are owned by ClipperBase's outrec_list_
+		};
 	};
 
 	///////////////////////////////////////////////////////////////////
@@ -124,6 +125,7 @@ namespace Clipper2Lib {
 		Vertex* vertex_top = nullptr;
 		LocalMinima* local_min = nullptr;  // the bottom of an edge 'bound' (also Vatti)
 		bool is_left_bound = false;
+		JoinWith join_with = JoinWith::NoJoin;
 	};
 
 	struct LocalMinima {
@@ -138,26 +140,58 @@ namespace Clipper2Lib {
 		Point64 pt;
 		Active* edge1;
 		Active* edge2;
-		IntersectNode() : pt(Point64(0, 0)), edge1(NULL), edge2(NULL) {}
+		IntersectNode() : pt(Point64(0,0)), edge1(NULL), edge2(NULL) {}
 			IntersectNode(Active* e1, Active* e2, Point64& pt_) :
-			pt(pt_), edge1(e1), edge2(e2)
+			pt(pt_), edge1(e1), edge2(e2) {}
-		{
+	};
-		}
+
+	struct HorzSegment {
+		OutPt* left_op;
+		OutPt* right_op = nullptr;
+		bool left_to_right = true;
+		HorzSegment() : left_op(nullptr) { }
+		explicit HorzSegment(OutPt* op) : left_op(op) { }
+	};
+
+	struct HorzJoin {
+		OutPt* op1 = nullptr;
+		OutPt* op2 = nullptr;
+		HorzJoin() {};
+		explicit HorzJoin(OutPt* ltr, OutPt* rtl) : op1(ltr), op2(rtl) { }
 	};
 
 #ifdef USINGZ
-		typedef std::function<void(const Point64& e1bot, const Point64& e1top,
+	typedef std::function<void(const Point64& e1bot, const Point64& e1top,
 		const Point64& e2bot, const Point64& e2top, Point64& pt)> ZCallback64;
 
 	typedef std::function<void(const PointD& e1bot, const PointD& e1top,
 		const PointD& e2bot, const PointD& e2top, PointD& pt)> ZCallbackD;
 #endif
 
+	typedef std::vector<HorzSegment> HorzSegmentList;
+	typedef std::unique_ptr<LocalMinima> LocalMinima_ptr;
+	typedef std::vector<LocalMinima_ptr> LocalMinimaList;
+	typedef std::vector<IntersectNode> IntersectNodeList;
+
+	// ReuseableDataContainer64 ------------------------------------------------
+
+	class ReuseableDataContainer64 {
+	private:
+		friend class ClipperBase;
+		LocalMinimaList minima_list_;
+		std::vector<Vertex*> vertex_lists_;
+		void AddLocMin(Vertex& vert, PathType polytype, bool is_open);
+	public:
+		virtual ~ReuseableDataContainer64();
+		void Clear();
+		void AddPaths(const Paths64& paths, PathType polytype, bool is_open);
+	};
+
 	// ClipperBase -------------------------------------------------------------
 
 	class ClipperBase {
 	private:
-		ClipType cliptype_ = ClipType::None;
+		ClipType cliptype_ = ClipType::NoClip;
 		FillRule fillrule_ = FillRule::EvenOdd;
 		FillRule fillpos = FillRule::Positive;
 		int64_t bot_y_ = 0;
@@ -165,21 +199,21 @@ namespace Clipper2Lib {
 		bool using_polytree_ = false;
 		Active* actives_ = nullptr;
 		Active *sel_ = nullptr;
-		Joiner *horz_joiners_ = nullptr;
+		LocalMinimaList minima_list_;		//pointers in case of memory reallocs
-		std::vector<LocalMinima*> minima_list_;		//pointers in case of memory reallocs
+		LocalMinimaList::iterator current_locmin_iter_;
-		std::vector<LocalMinima*>::iterator current_locmin_iter_;
 		std::vector<Vertex*> vertex_lists_;
 		std::priority_queue<int64_t> scanline_list_;
-		std::vector<IntersectNode> intersect_nodes_;
+		IntersectNodeList intersect_nodes_;
-		std::vector<Joiner*> joiner_list_;				//pointers in case of memory reallocs
+        HorzSegmentList horz_seg_list_;
+		std::vector<HorzJoin> horz_join_list_;
 		void Reset();
-		void InsertScanline(int64_t y);
+		inline void InsertScanline(int64_t y);
-		bool PopScanline(int64_t &y);
+		inline bool PopScanline(int64_t &y);
-		bool PopLocalMinima(int64_t y, LocalMinima *&local_minima);
+		inline bool PopLocalMinima(int64_t y, LocalMinima*& local_minima);
 		void DisposeAllOutRecs();
 		void DisposeVerticesAndLocalMinima();
 		void DeleteEdges(Active*& e);
-		void AddLocMin(Vertex &vert, PathType polytype, bool is_open);
+		inline void AddLocMin(Vertex &vert, PathType polytype, bool is_open);
 		bool IsContributingClosed(const Active &e) const;
 		inline bool IsContributingOpen(const Active &e) const;
 		void SetWindCountForClosedPathEdge(Active &edge);
@@ -190,7 +224,7 @@ namespace Clipper2Lib {
 		inline bool PopHorz(Active *&e);
 		inline OutPt* StartOpenPath(Active &e, const Point64& pt);
 		inline void UpdateEdgeIntoAEL(Active *e);
-		OutPt* IntersectEdges(Active &e1, Active &e2, const Point64& pt);
+		void IntersectEdges(Active &e1, Active &e2, const Point64& pt);
 		inline void DeleteFromAEL(Active &e);
 		inline void AdjustCurrXAndCopyToSEL(const int64_t top_y);
 		void DoIntersections(const int64_t top_y);
@@ -198,38 +232,41 @@ namespace Clipper2Lib {
 		bool BuildIntersectList(const int64_t top_y);
 		void ProcessIntersectList();
 		void SwapPositionsInAEL(Active& edge1, Active& edge2);
+		OutRec* NewOutRec();
 		OutPt* AddOutPt(const Active &e, const Point64& pt);
 		OutPt* AddLocalMinPoly(Active &e1, Active &e2,
 			const Point64& pt, bool is_new = false);
 		OutPt* AddLocalMaxPoly(Active &e1, Active &e2, const Point64& pt);
 		void DoHorizontal(Active &horz);
-		bool ResetHorzDirection(const Active &horz, const Active *max_pair,
+		bool ResetHorzDirection(const Active &horz, const Vertex* max_vertex,
 			int64_t &horz_left, int64_t &horz_right);
 		void DoTopOfScanbeam(const int64_t top_y);
 		Active *DoMaxima(Active &e);
 		void JoinOutrecPaths(Active &e1, Active &e2);
-		void CompleteSplit(OutPt* op1, OutPt* op2, OutRec& outrec);
-		bool ValidateClosedPathEx(OutPt*& outrec);
-		void CleanCollinear(OutRec* outrec);
 		void FixSelfIntersects(OutRec* outrec);
 		void DoSplitOp(OutRec* outRec, OutPt* splitOp);
-		Joiner* GetHorzTrialParent(const OutPt* op);
+
-		bool OutPtInTrialHorzList(OutPt* op);
+		inline void AddTrialHorzJoin(OutPt* op);
-		void SafeDisposeOutPts(OutPt*& op);
+		void ConvertHorzSegsToJoins();
-		void SafeDeleteOutPtJoiners(OutPt* op);
+		void ProcessHorzJoins();
-		void AddTrialHorzJoin(OutPt* op);
+
-		void DeleteTrialHorzJoin(OutPt* op);
+		void Split(Active& e, const Point64& pt);
-		void ConvertHorzTrialsToJoins();
+		inline void CheckJoinLeft(Active& e,
-		void AddJoin(OutPt* op1, OutPt* op2);
+			const Point64& pt, bool check_curr_x = false);
-		void DeleteJoin(Joiner* joiner);
+		inline void CheckJoinRight(Active& e,
-		void ProcessJoinerList();
+			const Point64& pt, bool check_curr_x = false);
-		OutRec* ProcessJoin(Joiner* joiner);
 	protected:
+		bool preserve_collinear_ = true;
+		bool reverse_solution_ = false;
+		int error_code_ = 0;
 		bool has_open_paths_ = false;
 		bool succeeded_ = true;
-		std::vector<OutRec*> outrec_list_; //pointers in case list memory reallocated
+		OutRecList outrec_list_; //pointers in case list memory reallocated
 		bool ExecuteInternal(ClipType ct, FillRule ft, bool use_polytrees);
-		bool DeepCheckOwner(OutRec* outrec, OutRec* owner);
+		void CleanCollinear(OutRec* outrec);
+		bool CheckBounds(OutRec* outrec);
+		bool CheckSplitOwner(OutRec* outrec, OutRecList* splits);
+		void RecursiveCheckOwners(OutRec* outrec, PolyPath* polypath);
 #ifdef USINGZ
 		ZCallback64 zCallback_ = nullptr;
 		void SetZ(const Active& e1, const Active& e2, Point64& pt);
@@ -239,9 +276,16 @@ namespace Clipper2Lib {
 		void AddPaths(const Paths64& paths, PathType polytype, bool is_open);
 	public:
 		virtual ~ClipperBase();
-		bool PreserveCollinear = true;
+		int ErrorCode() const { return error_code_; };
-		bool ReverseSolution = false;
+		void PreserveCollinear(bool val) { preserve_collinear_ = val; };
+		bool PreserveCollinear() const { return preserve_collinear_;};
+		void ReverseSolution(bool val) { reverse_solution_ = val; };
+		bool ReverseSolution() const { return reverse_solution_; };
 		void Clear();
+		void AddReuseableData(const ReuseableDataContainer64& reuseable_data);
+#ifdef USINGZ
+		int64_t DefaultZ = 0;
+#endif
 	};
 
 	// PolyPath / PolyTree --------------------------------------------------------
@@ -256,7 +300,7 @@ namespace Clipper2Lib {
 		PolyPath* parent_;
 	public:
 		PolyPath(PolyPath* parent = nullptr): parent_(parent){}
-		virtual ~PolyPath() { Clear(); };
+		virtual ~PolyPath() {};
 		//https://en.cppreference.com/w/cpp/language/rule_of_three
 		PolyPath(const PolyPath&) = delete;
 		PolyPath& operator=(const PolyPath&) = delete;
@@ -271,50 +315,58 @@ namespace Clipper2Lib {
 
 		virtual PolyPath* AddChild(const Path64& path) = 0;
 
-		virtual void Clear() {};
+		virtual void Clear() = 0;
 		virtual size_t Count() const { return 0; }
 
 		const PolyPath* Parent() const { return parent_; }
 
 		bool IsHole() const
 		{
-			const PolyPath* pp = parent_;
+			unsigned lvl = Level();
-			bool is_hole = pp;
+			//Even levels except level 0
-			while (pp) {
+			return lvl && !(lvl & 1);
-				is_hole = !is_hole;
-				pp = pp->parent_;
-			}
-			return is_hole;
 		}
 	};
 
+	typedef typename std::vector<std::unique_ptr<PolyPath64>> PolyPath64List;
+	typedef typename std::vector<std::unique_ptr<PolyPathD>>  PolyPathDList;
+
 	class PolyPath64 : public PolyPath {
 	private:
-		std::vector<PolyPath64*> childs_;
+		PolyPath64List childs_;
 		Path64 polygon_;
-		typedef typename std::vector<PolyPath64*>::const_iterator pp64_itor;
 	public:
-		PolyPath64(PolyPath64* parent = nullptr) : PolyPath(parent) {}
+		explicit PolyPath64(PolyPath64* parent = nullptr) : PolyPath(parent) {}
-        PolyPath64 *operator[](size_t index) { return static_cast<PolyPath64 *>(childs_[index]); }
+		explicit PolyPath64(PolyPath64* parent, const Path64& path) : PolyPath(parent) { polygon_ = path; }
-        PolyPath64 *Childs(size_t index) const { return static_cast<PolyPath64 *>(childs_[index]); }
+
-		pp64_itor begin() const { return childs_.cbegin(); }
+		~PolyPath64() {
-		pp64_itor end() const { return childs_.cend(); }
+			childs_.resize(0);
+		}
+
+		PolyPath64* operator [] (size_t index) const
+		{
+			return childs_[index].get(); //std::unique_ptr
+		}
+
+		PolyPath64* Child(size_t index) const
+		{
+			return childs_[index].get();
+		}
+
+		PolyPath64List::const_iterator begin() const { return childs_.cbegin(); }
+		PolyPath64List::const_iterator end() const { return childs_.cend(); }
 
 		PolyPath64* AddChild(const Path64& path) override
 		{
-			PolyPath64* result = new PolyPath64(this);
+			return childs_.emplace_back(std::make_unique<PolyPath64>(this, path)).get();
-			childs_.push_back(result);
-			result->polygon_ = path;
-			return result;
 		}
 
 		void Clear() override
 		{
-			for (const PolyPath64* child : childs_) delete child;
 			childs_.resize(0);
 		}
 
-		size_t Count() const  override
+		size_t Count() const override
 		{
 			return childs_.size();
 		}
@@ -323,78 +375,73 @@ namespace Clipper2Lib {
 
 		double Area() const
 		{
-			double result = Clipper2Lib::Area<int64_t>(polygon_);
+			return std::accumulate(childs_.cbegin(), childs_.cend(),
-			for (const PolyPath64* child : childs_)
+				Clipper2Lib::Area<int64_t>(polygon_),
-				result += child->Area();
+				[](double a, const auto& child) {return a + child->Area(); });
-			return result;
-		}
-
-		friend std::ostream& operator << (std::ostream& outstream, const PolyPath64& polypath)
-		{
-			const size_t level_indent = 4;
-			const size_t coords_per_line = 4;
-			const size_t last_on_line = coords_per_line - 1;
-			unsigned level = polypath.Level();
-			if (level > 0)
-			{
-				std::string level_padding;
-				level_padding.insert(0, (level - 1) * level_indent, ' ');
-				std::string caption = polypath.IsHole() ? "Hole " : "Outer Polygon ";
-				std::string childs = polypath.Count() == 1 ? " child" : " children";
-				outstream << level_padding.c_str() << caption << "with " << polypath.Count() << childs << std::endl;
-				outstream << level_padding;
-				size_t i = 0, highI = polypath.Polygon().size() - 1;
-				for (; i < highI; ++i)
-				{
-					outstream << polypath.Polygon()[i] << ' ';
-					if ((i % coords_per_line) == last_on_line)
-						outstream << std::endl << level_padding;
-				}
-				if (highI > 0) outstream << polypath.Polygon()[i];
-				outstream << std::endl;
-			}
-			for (auto child : polypath)
-				outstream << *child;
-			return outstream;
 		}
 
 	};
 
 	class PolyPathD : public PolyPath {
 	private:
-		std::vector<PolyPathD*> childs_;
+		PolyPathDList childs_;
-		double inv_scale_;
+		double scale_;
 		PathD polygon_;
-		typedef typename std::vector<PolyPathD*>::const_iterator ppD_itor;
 	public:
-		PolyPathD(PolyPathD* parent = nullptr) : PolyPath(parent)
+		explicit PolyPathD(PolyPathD* parent = nullptr) : PolyPath(parent)
 		{
-			inv_scale_ = parent ? parent->inv_scale_ : 1.0;
+			scale_ = parent ? parent->scale_ : 1.0;
 		}
-		PolyPathD* operator [] (size_t index)
-		{
-			return static_cast<PolyPathD*>(childs_[index]);
-		}
-		ppD_itor begin() const { return childs_.cbegin(); }
-		ppD_itor end() const { return childs_.cend(); }
 
-		void SetInvScale(double value) { inv_scale_ = value; }
+		explicit PolyPathD(PolyPathD* parent, const Path64& path) : PolyPath(parent)
-		double InvScale() { return inv_scale_; }
+		{
+			scale_ = parent ? parent->scale_ : 1.0;
+			int error_code = 0;
+			polygon_ = ScalePath<double, int64_t>(path, scale_, error_code);
+		}
+
+		explicit PolyPathD(PolyPathD* parent, const PathD& path) : PolyPath(parent)
+		{
+			scale_ = parent ? parent->scale_ : 1.0;
+			polygon_ = path;
+		}
+
+		~PolyPathD() {
+			childs_.resize(0);
+		}
+
+		PolyPathD* operator [] (size_t index) const
+		{
+			return childs_[index].get();
+		}
+
+		PolyPathD* Child(size_t index) const
+		{
+			return childs_[index].get();
+		}
+
+		PolyPathDList::const_iterator begin() const { return childs_.cbegin(); }
+		PolyPathDList::const_iterator end() const { return childs_.cend(); }
+
+		void SetScale(double value) { scale_ = value; }
+		double Scale() const { return scale_; }
+
 		PolyPathD* AddChild(const Path64& path) override
 		{
-			PolyPathD* result = new PolyPathD(this);
+			return childs_.emplace_back(std::make_unique<PolyPathD>(this, path)).get();
-			childs_.push_back(result);
+		}
-			result->polygon_ = ScalePath<double, int64_t>(path, inv_scale_);
+
-			return result;
+		PolyPathD* AddChild(const PathD& path)
+		{
+			return childs_.emplace_back(std::make_unique<PolyPathD>(this, path)).get();
 		}
 
 		void Clear() override
 		{
-			for (const PolyPathD* child : childs_) delete child;
 			childs_.resize(0);
 		}
 
-		size_t Count() const  override
+		size_t Count() const override
 		{
 			return childs_.size();
 		}
@@ -403,10 +450,9 @@ namespace Clipper2Lib {
 
 		double Area() const
 		{
-			double result = Clipper2Lib::Area<double>(polygon_);
+			return std::accumulate(childs_.begin(), childs_.end(),
-			for (const PolyPathD* child : childs_)
+				Clipper2Lib::Area<double>(polygon_),
-				result += child->Area();
+				[](double a, const auto& child) {return a + child->Area(); });
-			return result;
 		}
 	};
 
@@ -446,7 +492,7 @@ namespace Clipper2Lib {
 			closed_paths.clear();
 			open_paths.clear();
 			if (ExecuteInternal(clip_type, fill_rule, false))
-				BuildPaths64(closed_paths, &open_paths);
+					BuildPaths64(closed_paths, &open_paths);
 			CleanUp();
 			return succeeded_;
 		}
@@ -475,14 +521,14 @@ namespace Clipper2Lib {
 	private:
 		double scale_ = 1.0, invScale_ = 1.0;
 #ifdef USINGZ
-		ZCallbackD zCallback_ = nullptr;
+		ZCallbackD zCallbackD_ = nullptr;
 #endif
 		void BuildPathsD(PathsD& solutionClosed, PathsD* solutionOpen);
 		void BuildTreeD(PolyPathD& polytree, PathsD& open_paths);
 	public:
 		explicit ClipperD(int precision = 2) : ClipperBase()
 		{
-			CheckPrecision(precision);
+			CheckPrecisionRange(precision, error_code_);
 			// to optimize scaling / descaling precision
 			// set the scale to a power of double's radix (2) (#25)
 			scale_ = std::pow(std::numeric_limits<double>::radix,
@@ -491,7 +537,7 @@ namespace Clipper2Lib {
 		}
 
 #ifdef USINGZ
-		void SetZCallback(ZCallbackD cb) { zCallback_ = cb; };
+		void SetZCallback(ZCallbackD cb) { zCallbackD_ = cb; };
 
 		void ZCB(const Point64& e1bot, const Point64& e1top,
 			const Point64& e2bot, const Point64& e2top, Point64& pt)
@@ -505,13 +551,13 @@ namespace Clipper2Lib {
 			PointD e1t = PointD(e1top) * invScale_;
 			PointD e2b = PointD(e2bot) * invScale_;
 			PointD e2t = PointD(e2top) * invScale_;
-			zCallback_(e1b,e1t, e2b, e2t, tmp);
+			zCallbackD_(e1b,e1t, e2b, e2t, tmp);
 			pt.z = tmp.z; // only update 'z'
 		};
 
 		void CheckCallback()
 		{
-			if(zCallback_)
+			if(zCallbackD_)
 				// if the user defined float point callback has been assigned
 				// then assign the proxy callback function
 				ClipperBase::zCallback_ =
@@ -526,17 +572,17 @@ namespace Clipper2Lib {
 
 		void AddSubject(const PathsD& subjects)
 		{
-			AddPaths(ScalePaths<int64_t, double>(subjects, scale_), PathType::Subject, false);
+			AddPaths(ScalePaths<int64_t, double>(subjects, scale_, error_code_), PathType::Subject, false);
 		}
 
 		void AddOpenSubject(const PathsD& open_subjects)
 		{
-			AddPaths(ScalePaths<int64_t, double>(open_subjects, scale_), PathType::Subject, true);
+			AddPaths(ScalePaths<int64_t, double>(open_subjects, scale_, error_code_), PathType::Subject, true);
 		}
 
 		void AddClip(const PathsD& clips)
 		{
-			AddPaths(ScalePaths<int64_t, double>(clips, scale_), PathType::Clip, false);
+			AddPaths(ScalePaths<int64_t, double>(clips, scale_, error_code_), PathType::Clip, false);
 		}
 
 		bool Execute(ClipType clip_type, FillRule fill_rule, PathsD& closed_paths)
@@ -574,7 +620,7 @@ namespace Clipper2Lib {
 			if (ExecuteInternal(clip_type, fill_rule, true))
 			{
 				polytree.Clear();
-				polytree.SetInvScale(invScale_);
+				polytree.SetScale(invScale_);
 				open_paths.clear();
 				BuildTreeD(polytree, open_paths);
 			}

src/clipper2/Clipper2Lib/include/clipper2/clipper.minkowski.h

@@ -1,21 +1,18 @@
 /*******************************************************************************
 * Author    :  Angus Johnson                                                   *
-* Date      :  15 October 2022                                                 *
+* Date      :  1 November 2023                                                 *
-* Website   :  http://www.angusj.com                                           *
+* Website   :  https://www.angusj.com                                          *
-* Copyright :  Angus Johnson 2010-2022                                         *
+* Copyright :  Angus Johnson 2010-2023                                         *
 * Purpose   :  Minkowski Sum and Difference                                    *
-* License   :  http://www.boost.org/LICENSE_1_0.txt                            *
+* License   :  https://www.boost.org/LICENSE_1_0.txt                           *
 *******************************************************************************/
 
 #ifndef CLIPPER_MINKOWSKI_H
 #define CLIPPER_MINKOWSKI_H
 
-#include <cstdlib>
+#include "clipper2/clipper.core.h"
-#include <vector>
-#include <string>
-#include "clipper.core.h"
 
-namespace Clipper2Lib 
+namespace Clipper2Lib
 {
 
   namespace detail
@@ -35,7 +32,7 @@ namespace Clipper2Lib
           Path64 path2(pattern.size());
           std::transform(pattern.cbegin(), pattern.cend(),
             path2.begin(), [p](const Point64& pt2) {return p + pt2; });
-          tmp.push_back(path2);
+          tmp.emplace_back(std::move(path2));
         }
       }
       else
@@ -45,7 +42,7 @@ namespace Clipper2Lib
           Path64 path2(pattern.size());
           std::transform(pattern.cbegin(), pattern.cend(),
             path2.begin(), [p](const Point64& pt2) {return p - pt2; });
-          tmp.push_back(path2);
+          tmp.emplace_back(std::move(path2));
         }
       }
 
@@ -59,14 +56,14 @@ namespace Clipper2Lib
           Path64 quad;
           quad.reserve(4);
           {
-            quad.push_back(tmp[g][h]);
+            quad.emplace_back(tmp[g][h]);
-            quad.push_back(tmp[i][h]);
+            quad.emplace_back(tmp[i][h]);
-            quad.push_back(tmp[i][j]);
+            quad.emplace_back(tmp[i][j]);
-            quad.push_back(tmp[g][j]);
+            quad.emplace_back(tmp[g][j]);
           };
           if (!IsPositive(quad))
             std::reverse(quad.begin(), quad.end());
-          result.push_back(quad);
+          result.emplace_back(std::move(quad));
           h = j;
         }
         g = i;
@@ -92,11 +89,12 @@ namespace Clipper2Lib
 
   inline PathsD MinkowskiSum(const PathD& pattern, const PathD& path, bool isClosed, int decimalPlaces = 2)
   {
+    int error_code = 0;
     double scale = pow(10, decimalPlaces);
-    Path64 pat64 = ScalePath<int64_t, double>(pattern, scale);
+    Path64 pat64 = ScalePath<int64_t, double>(pattern, scale, error_code);
-    Path64 path64 = ScalePath<int64_t, double>(path, scale);
+    Path64 path64 = ScalePath<int64_t, double>(path, scale, error_code);
     Paths64 tmp = detail::Union(detail::Minkowski(pat64, path64, true, isClosed), FillRule::NonZero);
-    return ScalePaths<double, int64_t>(tmp, 1 / scale);
+    return ScalePaths<double, int64_t>(tmp, 1 / scale, error_code);
   }
 
   inline Paths64 MinkowskiDiff(const Path64& pattern, const Path64& path, bool isClosed)
@@ -106,11 +104,12 @@ namespace Clipper2Lib
 
   inline PathsD MinkowskiDiff(const PathD& pattern, const PathD& path, bool isClosed, int decimalPlaces = 2)
   {
+    int error_code = 0;
     double scale = pow(10, decimalPlaces);
-    Path64 pat64 = ScalePath<int64_t, double>(pattern, scale); 
+    Path64 pat64 = ScalePath<int64_t, double>(pattern, scale, error_code);
-    Path64 path64 = ScalePath<int64_t, double>(path, scale);
+    Path64 path64 = ScalePath<int64_t, double>(path, scale, error_code);
     Paths64 tmp = detail::Union(detail::Minkowski(pat64, path64, false, isClosed), FillRule::NonZero);
-    return ScalePaths<double, int64_t>(tmp, 1 / scale);
+    return ScalePaths<double, int64_t>(tmp, 1 / scale, error_code);
   }
 
 } // Clipper2Lib namespace

src/clipper2/Clipper2Lib/include/clipper2/clipper.offset.h

@@ -1,20 +1,24 @@
 /*******************************************************************************
 * Author    :  Angus Johnson                                                   *
-* Date      :  15 October 2022                                                 *
+* Date      :  22 January 2025                                                 *
-* Website   :  http://www.angusj.com                                           *
+* Website   :  https://www.angusj.com                                          *
-* Copyright :  Angus Johnson 2010-2022                                         *
+* Copyright :  Angus Johnson 2010-2025                                         *
 * Purpose   :  Path Offset (Inflate/Shrink)                                    *
-* License   :  http://www.boost.org/LICENSE_1_0.txt                            *
+* License   :  https://www.boost.org/LICENSE_1_0.txt                           *
 *******************************************************************************/
 
 #ifndef CLIPPER_OFFSET_H_
 #define CLIPPER_OFFSET_H_
 
 #include "clipper.core.h"
+#include "clipper.engine.h"
+#include <optional>
 
 namespace Clipper2Lib {
 
-enum class JoinType { Square, Round, Miter };
+enum class JoinType { Square, Bevel, Round, Miter };
+//Square : Joins are 'squared' at exactly the offset distance (more complex code)
+//Bevel  : Similar to Square, but the offset distance varies with angle (simple code & faster)
 
 enum class EndType {Polygon, Joined, Butt, Square, Round};
 //Butt   : offsets both sides of a path, with square blunt ends
@@ -23,49 +27,64 @@ enum class EndType {Polygon, Joined, Butt, Square, Round};
 //Joined : offsets both sides of a path, with joined ends
 //Polygon: offsets only one side of a closed path
 
+typedef std::function<double(const Path64& path, const PathD& path_normals, size_t curr_idx, size_t prev_idx)> DeltaCallback64;
+
 class ClipperOffset {
 private:
 
 	class Group {
 	public:
-		Paths64 paths_in_;
+		Paths64 paths_in;
-		Paths64 paths_out_;
+        std::optional<size_t> lowest_path_idx{};
-		Path64 path_;
+		bool is_reversed = false;
-		bool is_reversed_ = false;
+		JoinType join_type;
-		JoinType join_type_;
+		EndType end_type;
-		EndType end_type_;
+		Group(const Paths64& _paths, JoinType _join_type, EndType _end_type);
-		Group(const Paths64& paths, JoinType join_type, EndType end_type) :
-			paths_in_(paths), join_type_(join_type), end_type_(end_type) {}
 	};
 
+	int   error_code_ = 0;
+	double delta_ = 0.0;
 	double group_delta_ = 0.0;
-	double abs_group_delta_ = 0.0;
 	double temp_lim_ = 0.0;
 	double steps_per_rad_ = 0.0;
+	double step_sin_ = 0.0;
+	double step_cos_ = 0.0;
 	PathD norms;
-	Paths64 solution;
+	Path64 path_out;
+	Paths64* solution = nullptr;
+	PolyTree64* solution_tree = nullptr;
 	std::vector<Group> groups_;
-	JoinType join_type_ = JoinType::Square;
+	JoinType join_type_ = JoinType::Bevel;
-	
+	EndType end_type_ = EndType::Polygon;
+
 	double miter_limit_ = 0.0;
 	double arc_tolerance_ = 0.0;
-	bool merge_groups_ = true;
 	bool preserve_collinear_ = false;
 	bool reverse_solution_ = false;
 
-	void DoSquare(Group& group, const Path64& path, size_t j, size_t k);
+#ifdef USINGZ
-	void DoMiter(Group& group, const Path64& path, size_t j, size_t k, double cos_a);
+	ZCallback64 zCallback64_ = nullptr;
-	void DoRound(Group& group, const Path64& path, size_t j, size_t k, double angle);
+	void ZCB(const Point64& bot1, const Point64& top1,
+		const Point64& bot2, const Point64& top2, Point64& ip);
+#endif
+	DeltaCallback64 deltaCallback64_ = nullptr;
+	size_t CalcSolutionCapacity();
+	bool CheckReverseOrientation();
+	void DoBevel(const Path64& path, size_t j, size_t k);
+	void DoSquare(const Path64& path, size_t j, size_t k);
+	void DoMiter(const Path64& path, size_t j, size_t k, double cos_a);
+	void DoRound(const Path64& path, size_t j, size_t k, double angle);
 	void BuildNormals(const Path64& path);
-	void OffsetPolygon(Group& group, Path64& path);
+	void OffsetPolygon(Group& group, const Path64& path);
-	void OffsetOpenJoined(Group& group, Path64& path);
+	void OffsetOpenJoined(Group& group, const Path64& path);
-	void OffsetOpenPath(Group& group, Path64& path, EndType endType);
+	void OffsetOpenPath(Group& group, const Path64& path);
-	void OffsetPoint(Group& group, Path64& path, size_t j, size_t& k);
+	void OffsetPoint(Group& group, const Path64& path, size_t j, size_t k);
-	void DoGroupOffset(Group &group, double delta);
+	void DoGroupOffset(Group &group);
+	void ExecuteInternal(double delta);
 public:
-	ClipperOffset(double miter_limit = 2.0,
+	explicit ClipperOffset(double miter_limit = 2.0,
 		double arc_tolerance = 0.0,
-		bool preserve_collinear = false, 
+		bool preserve_collinear = false,
 		bool reverse_solution = false) :
 		miter_limit_(miter_limit), arc_tolerance_(arc_tolerance),
 		preserve_collinear_(preserve_collinear),
@@ -73,13 +92,14 @@ public:
 
 	~ClipperOffset() { Clear(); };
 
+	int ErrorCode() const { return error_code_; };
 	void AddPath(const Path64& path, JoinType jt_, EndType et_);
 	void AddPaths(const Paths64& paths, JoinType jt_, EndType et_);
-	void AddPath(const PathD &p, JoinType jt_, EndType et_);
-	void AddPaths(const PathsD &p, JoinType jt_, EndType et_);
 	void Clear() { groups_.clear(); norms.clear(); };
 	
-	Paths64 Execute(double delta);
+	void Execute(double delta, Paths64& sols_64);
+	void Execute(double delta, PolyTree64& polytree);
+	void Execute(DeltaCallback64 delta_cb, Paths64& paths);
 
 	double MiterLimit() const { return miter_limit_; }
 	void MiterLimit(double miter_limit) { miter_limit_ = miter_limit; }
@@ -88,19 +108,17 @@ public:
 	double ArcTolerance() const { return arc_tolerance_; }
 	void ArcTolerance(double arc_tolerance) { arc_tolerance_ = arc_tolerance; }
 
-	//MergeGroups: A path group is one or more paths added via the AddPath or
-	//AddPaths methods. By default these path groups will be offset
-	//independently of other groups and this may cause overlaps (intersections).
-	//However, when MergeGroups is enabled, any overlapping offsets will be
-	//merged (via a clipping union operation) to remove overlaps.
-	bool MergeGroups() const { return merge_groups_; }
-	void MergeGroups(bool merge_groups) { merge_groups_ = merge_groups; }
-
 	bool PreserveCollinear() const { return preserve_collinear_; }
 	void PreserveCollinear(bool preserve_collinear){preserve_collinear_ = preserve_collinear;}
 	
 	bool ReverseSolution() const { return reverse_solution_; }
 	void ReverseSolution(bool reverse_solution) {reverse_solution_ = reverse_solution;}
+
+#ifdef USINGZ
+	void SetZCallback(ZCallback64 cb) { zCallback64_ = cb; }
+#endif
+	void SetDeltaCallback(DeltaCallback64 cb) { deltaCallback64_ = cb; }
+
 };
 
 }

src/clipper2/Clipper2Lib/include/clipper2/clipper.rectclip.h

@@ -1,49 +1,79 @@
 /*******************************************************************************
 * Author    :  Angus Johnson                                                   *
-* Date      :  26 October 2022                                                 *
+* Date      :  5 July 2024                                                     *
-* Website   :  http://www.angusj.com                                           *
+* Website   :  https://www.angusj.com                                          *
-* Copyright :  Angus Johnson 2010-2022                                         *
+* Copyright :  Angus Johnson 2010-2024                                         *
 * Purpose   :  FAST rectangular clipping                                       *
-* License   :  http://www.boost.org/LICENSE_1_0.txt                            *
+* License   :  https://www.boost.org/LICENSE_1_0.txt                           *
 *******************************************************************************/
 
 #ifndef CLIPPER_RECTCLIP_H
 #define CLIPPER_RECTCLIP_H
 
-#include <cstdlib>
+#include "clipper2/clipper.core.h"
-#include <vector>
+#include <queue>
-#include "clipper.h"
-#include "clipper.core.h"
 
-namespace Clipper2Lib 
+namespace Clipper2Lib
 {
 
+  // Location: the order is important here, see StartLocsIsClockwise()
   enum class Location { Left, Top, Right, Bottom, Inside };
 
-  class RectClip {
+  class OutPt2;
+  typedef std::vector<OutPt2*> OutPt2List;
+
+  class OutPt2 {
+  public:
+    Point64 pt;
+    size_t owner_idx = 0;
+    OutPt2List* edge = nullptr;
+    OutPt2* next = nullptr;
+    OutPt2* prev = nullptr;
+  };
+
+  //------------------------------------------------------------------------------
+  // RectClip64
+  //------------------------------------------------------------------------------
+
+  class RectClip64 {
+  private:
+    void ExecuteInternal(const Path64& path);
+    Path64 GetPath(OutPt2*& op);
   protected:
     const Rect64 rect_;
-    const Point64 mp_;
+    const Path64 rect_as_path_;
-    const Path64 rectPath_;
+    const Point64 rect_mp_;
-    Path64 result_;
+    Rect64 path_bounds_;
+    std::deque<OutPt2> op_container_;
+    OutPt2List results_;  // each path can be broken into multiples
+    OutPt2List edges_[8]; // clockwise and counter-clockwise
     std::vector<Location> start_locs_;
-
+    void CheckEdges();
+    void TidyEdges(size_t idx, OutPt2List& cw, OutPt2List& ccw);
     void GetNextLocation(const Path64& path,
-      Location& loc, int& i, int highI);
+      Location& loc, size_t& i, size_t highI);
+    OutPt2* Add(Point64 pt, bool start_new = false);
     void AddCorner(Location prev, Location curr);
     void AddCorner(Location& loc, bool isClockwise);
   public:
-    RectClip(const Rect64& rect) :
+    explicit RectClip64(const Rect64& rect) :
       rect_(rect),
-      mp_(rect.MidPoint()),
+      rect_as_path_(rect.AsPath()),
-      rectPath_(rect.AsPath()) {}
+      rect_mp_(rect.MidPoint()) {}
-    Path64 Execute(const Path64& path);
+    Paths64 Execute(const Paths64& paths);
   };
 
-  class RectClipLines : public RectClip {
+  //------------------------------------------------------------------------------
+  // RectClipLines64
+  //------------------------------------------------------------------------------
+
+  class RectClipLines64 : public RectClip64 {
+  private:
+    void ExecuteInternal(const Path64& path);
+    Path64 GetPath(OutPt2*& op);
   public:
-    RectClipLines(const Rect64& rect) : RectClip(rect) {};
+    explicit RectClipLines64(const Rect64& rect) : RectClip64(rect) {};
-    Paths64 Execute(const Path64& path);
+    Paths64 Execute(const Paths64& paths);
   };
 
 } // Clipper2Lib namespace

src/clipper2/Clipper2Lib/include/clipper2/clipper.version.h

@@ -0,0 +1,6 @@
+#ifndef CLIPPER_VERSION_H
+#define CLIPPER_VERSION_H
+
+constexpr auto CLIPPER2_VERSION = "1.5.2";
+
+#endif  // CLIPPER_VERSION_H

src/clipper2/Clipper2Lib/src/clipper.offset.cpp

@@ -1,48 +1,72 @@
 /*******************************************************************************
 * Author    :  Angus Johnson                                                   *
-* Date      :  15 October 2022                                                 *
+* Date      :  22 January 2025                                                 *
-* Website   :  http://www.angusj.com                                           *
+* Website   :  https://www.angusj.com                                          *
-* Copyright :  Angus Johnson 2010-2022                                         *
+* Copyright :  Angus Johnson 2010-2025                                         *
 * Purpose   :  Path Offset (Inflate/Shrink)                                    *
-* License   :  http://www.boost.org/LICENSE_1_0.txt                            *
+* License   :  https://www.boost.org/LICENSE_1_0.txt                           *
 *******************************************************************************/
 
-#include <cmath>
 #include "clipper2/clipper.h"
 #include "clipper2/clipper.offset.h"
 
 namespace Clipper2Lib {
 
-const double default_arc_tolerance = 0.25;
 const double floating_point_tolerance = 1e-12;
 
+// Clipper2 approximates arcs by using series of relatively short straight
+//line segments. And logically, shorter line segments will produce better arc
+// approximations. But very short segments can degrade performance, usually
+// with little or no discernable improvement in curve quality. Very short
+// segments can even detract from curve quality, due to the effects of integer
+// rounding. Since there isn't an optimal number of line segments for any given
+// arc radius (that perfectly balances curve approximation with performance),
+// arc tolerance is user defined. Nevertheless, when the user doesn't define
+// an arc tolerance (ie leaves alone the 0 default value), the calculated
+// default arc tolerance (offset_radius / 500) generally produces good (smooth)
+// arc approximations without producing excessively small segment lengths.
+// See also: https://www.angusj.com/clipper2/Docs/Trigonometry.htm
+const double arc_const = 0.002; // <-- 1/500
+
+
 //------------------------------------------------------------------------------
 // Miscellaneous methods
 //------------------------------------------------------------------------------
 
-Paths64::size_type GetLowestPolygonIdx(const Paths64& paths)
+std::optional<size_t> GetLowestClosedPathIdx(const Paths64& paths)
 {
-	Paths64::size_type result = 0;
+    std::optional<size_t> result;
-	Point64 lp = Point64(static_cast<int64_t>(0), 
+	Point64 botPt = Point64(INT64_MAX, INT64_MIN);
-		std::numeric_limits<int64_t>::min());
+	for (size_t i = 0; i < paths.size(); ++i)
-
+	{
-	for (Paths64::size_type i = 0 ; i < paths.size(); ++i)
+		for (const Point64& pt : paths[i])
-		for (const Point64& p : paths[i])
+		{
-		{ 
+			if ((pt.y < botPt.y) || 
-			if (p.y < lp.y || (p.y == lp.y && p.x >= lp.x)) continue;
+				((pt.y == botPt.y) && (pt.x >= botPt.x))) continue;
-			result = i;
+            result = i;
-			lp = p;
+			botPt.x = pt.x;
-		}	
+			botPt.y = pt.y;
+		}
+	}
 	return result;
 }
 
-PointD GetUnitNormal(const Point64& pt1, const Point64& pt2)
+inline double Hypot(double x, double y)
+{
+	// given that this is an internal function, and given the x and y parameters
+	// will always be coordinate values (or the difference between coordinate values),
+	// x and y should always be within INT64_MIN to INT64_MAX. Consequently, 
+	// there should be no risk that the following computation will overflow
+	// see https://stackoverflow.com/a/32436148/359538
+	return std::sqrt(x * x + y * y);
+}
+
+static PointD GetUnitNormal(const Point64& pt1, const Point64& pt2)
 {
-	double dx, dy, inverse_hypot;
 	if (pt1 == pt2) return PointD(0.0, 0.0);
-	dx = static_cast<double>(pt2.x - pt1.x);
+	double dx = static_cast<double>(pt2.x - pt1.x);
-	dy = static_cast<double>(pt2.y - pt1.y);
+	double dy = static_cast<double>(pt2.y - pt1.y);
-	inverse_hypot = 1.0 / hypot(dx, dy);
+	double inverse_hypot = 1.0 / Hypot(dx, dy);
 	dx *= inverse_hypot;
 	dy *= inverse_hypot;
 	return PointD(dy, -dx);
@@ -53,15 +77,8 @@ inline bool AlmostZero(double value, double epsilon = 0.001)
 	return std::fabs(value) < epsilon;
 }
 
-inline double Hypot(double x, double y) 
-{
-	//see https://stackoverflow.com/a/32436148/359538
-	return std::sqrt(x * x + y * y);
-}
-
 inline PointD NormalizeVector(const PointD& vec)
 {
-	
 	double h = Hypot(vec.x, vec.y);
 	if (AlmostZero(h)) return PointD(0,0);
 	double inverseHypot = 1 / h;
@@ -78,14 +95,63 @@ inline bool IsClosedPath(EndType et)
 	return et == EndType::Polygon || et == EndType::Joined;
 }
 
-inline Point64 GetPerpendic(const Point64& pt, const PointD& norm, double delta)
+static inline Point64 GetPerpendic(const Point64& pt, const PointD& norm, double delta)
 {
+#ifdef USINGZ
+	return Point64(pt.x + norm.x * delta, pt.y + norm.y * delta, pt.z);
+#else
 	return Point64(pt.x + norm.x * delta, pt.y + norm.y * delta);
+#endif
 }
 
 inline PointD GetPerpendicD(const Point64& pt, const PointD& norm, double delta)
 {
+#ifdef USINGZ
+	return PointD(pt.x + norm.x * delta, pt.y + norm.y * delta, pt.z);
+#else
 	return PointD(pt.x + norm.x * delta, pt.y + norm.y * delta);
+#endif
+}
+
+inline void NegatePath(PathD& path)
+{
+	for (PointD& pt : path)
+	{
+		pt.x = -pt.x;
+		pt.y = -pt.y;
+#ifdef USINGZ
+		pt.z = pt.z;
+#endif
+	}
+}
+
+
+//------------------------------------------------------------------------------
+// ClipperOffset::Group methods
+//------------------------------------------------------------------------------
+
+ClipperOffset::Group::Group(const Paths64& _paths, JoinType _join_type, EndType _end_type):
+	paths_in(_paths), join_type(_join_type), end_type(_end_type)
+{
+	bool is_joined =
+		(end_type == EndType::Polygon) ||
+		(end_type == EndType::Joined);
+	for (Path64& p: paths_in)
+	  StripDuplicates(p, is_joined);
+
+	if (end_type == EndType::Polygon)
+	{
+		lowest_path_idx = GetLowestClosedPathIdx(paths_in);
+		// the lowermost path must be an outer path, so if its orientation is negative,
+		// then flag the whole group is 'reversed' (will negate delta etc.)
+		// as this is much more efficient than reversing every path.
+    is_reversed = (lowest_path_idx.has_value()) && Area(paths_in[lowest_path_idx.value()]) < 0;
+	}
+	else
+	{
+    lowest_path_idx = std::nullopt;
+		is_reversed = false;
+	}
 }
 
 //------------------------------------------------------------------------------
@@ -94,28 +160,13 @@ inline PointD GetPerpendicD(const Point64& pt, const PointD& norm, double delta)
 
 void ClipperOffset::AddPath(const Path64& path, JoinType jt_, EndType et_)
 {
-	Paths64 paths;
+    groups_.emplace_back(Paths64(1, path), jt_, et_);
-	paths.push_back(path);
-	AddPaths(paths, jt_, et_);
 }
 
 void ClipperOffset::AddPaths(const Paths64 &paths, JoinType jt_, EndType et_)
 {
 	if (paths.size() == 0) return;
-	groups_.push_back(Group(paths, jt_, et_));
+    groups_.emplace_back(paths, jt_, et_);
-}
-
-void ClipperOffset::AddPath(const Clipper2Lib::PathD& path, JoinType jt_, EndType et_)
-{
-	PathsD paths;
-	paths.push_back(path);
-	AddPaths(paths, jt_, et_);
-}
-
-void ClipperOffset::AddPaths(const PathsD& paths, JoinType jt_, EndType et_)
-{
-	if (paths.size() == 0) return;
-	groups_.push_back(Group(PathsDToPaths64(paths), jt_, et_));
 }
 
 void ClipperOffset::BuildNormals(const Path64& path)
@@ -123,64 +174,55 @@ void ClipperOffset::BuildNormals(const Path64& path)
 	norms.clear();
 	norms.reserve(path.size());
 	if (path.size() == 0) return;
-	Path64::const_iterator path_iter, path_last_iter = --path.cend();
+	Path64::const_iterator path_iter, path_stop_iter = --path.cend();
-	for (path_iter = path.cbegin(); path_iter != path_last_iter; ++path_iter)
+	for (path_iter = path.cbegin(); path_iter != path_stop_iter; ++path_iter)
-		norms.push_back(GetUnitNormal(*path_iter,*(path_iter +1)));
+        norms.emplace_back(GetUnitNormal(*path_iter,*(path_iter +1)));
-	norms.push_back(GetUnitNormal(*path_last_iter, *(path.cbegin())));
+    norms.emplace_back(GetUnitNormal(*path_stop_iter, *(path.cbegin())));
 }
 
-inline PointD TranslatePoint(const PointD& pt, double dx, double dy)
+void ClipperOffset::DoBevel(const Path64& path, size_t j, size_t k)
 {
-	return PointD(pt.x + dx, pt.y + dy);
+	PointD pt1, pt2;
-}
+	if (j == k)
-
-inline PointD ReflectPoint(const PointD& pt, const PointD& pivot)
-{
-	return PointD(pivot.x + (pivot.x - pt.x), pivot.y + (pivot.y - pt.y));
-}
-
-PointD IntersectPoint(const PointD& pt1a, const PointD& pt1b,
-	const PointD& pt2a, const PointD& pt2b)
-{
-	if (pt1a.x == pt1b.x) //vertical
 	{
-		if (pt2a.x == pt2b.x) return PointD(0, 0);
+		double abs_delta = std::abs(group_delta_);
-
+#ifdef USINGZ
-		double m2 = (pt2b.y - pt2a.y) / (pt2b.x - pt2a.x);
+		pt1 = PointD(path[j].x - abs_delta * norms[j].x, path[j].y - abs_delta * norms[j].y, path[j].z);
-		double b2 = pt2a.y - m2 * pt2a.x;
+		pt2 = PointD(path[j].x + abs_delta * norms[j].x, path[j].y + abs_delta * norms[j].y, path[j].z);
-		return PointD(pt1a.x, m2 * pt1a.x + b2);
+#else
-	}
+		pt1 = PointD(path[j].x - abs_delta * norms[j].x, path[j].y - abs_delta * norms[j].y);
-	else if (pt2a.x == pt2b.x) //vertical
+		pt2 = PointD(path[j].x + abs_delta * norms[j].x, path[j].y + abs_delta * norms[j].y);
-	{
+#endif
-		double m1 = (pt1b.y - pt1a.y) / (pt1b.x - pt1a.x);
-		double b1 = pt1a.y - m1 * pt1a.x;
-		return PointD(pt2a.x, m1 * pt2a.x + b1);
 	}
 	else
 	{
-		double m1 = (pt1b.y - pt1a.y) / (pt1b.x - pt1a.x);
+#ifdef USINGZ
-		double b1 = pt1a.y - m1 * pt1a.x;
+		pt1 = PointD(path[j].x + group_delta_ * norms[k].x, path[j].y + group_delta_ * norms[k].y, path[j].z);
-		double m2 = (pt2b.y - pt2a.y) / (pt2b.x - pt2a.x);
+		pt2 = PointD(path[j].x + group_delta_ * norms[j].x, path[j].y + group_delta_ * norms[j].y, path[j].z);
-		double b2 = pt2a.y - m2 * pt2a.x;
+#else
-		if (m1 == m2) return PointD(0, 0);
+		pt1 = PointD(path[j].x + group_delta_ * norms[k].x, path[j].y + group_delta_ * norms[k].y);
-		double x = (b2 - b1) / (m1 - m2);
+		pt2 = PointD(path[j].x + group_delta_ * norms[j].x, path[j].y + group_delta_ * norms[j].y);
-		return PointD(x, m1 * x + b1);
+#endif
 	}
+    path_out.emplace_back(pt1);
+    path_out.emplace_back(pt2);
 }
 
-void ClipperOffset::DoSquare(Group& group, const Path64& path, size_t j, size_t k)
+void ClipperOffset::DoSquare(const Path64& path, size_t j, size_t k)
 {
 	PointD vec;
-	if (j == k) 
+	if (j == k)
-		vec = PointD(norms[0].y, -norms[0].x);
+		vec = PointD(norms[j].y, -norms[j].x);
 	else
 		vec = GetAvgUnitVector(
 			PointD(-norms[k].y, norms[k].x),
 			PointD(norms[j].y, -norms[j].x));
 
+	double abs_delta = std::abs(group_delta_);
+
 	// now offset the original vertex delta units along unit vector
 	PointD ptQ = PointD(path[j]);
-	ptQ = TranslatePoint(ptQ, abs_group_delta_ * vec.x, abs_group_delta_ * vec.y);
+	ptQ = TranslatePoint(ptQ, abs_delta * vec.x, abs_delta * vec.y);
 	// get perpendicular vertices
 	PointD pt1 = TranslatePoint(ptQ, group_delta_ * vec.y, group_delta_ * -vec.x);
 	PointD pt2 = TranslatePoint(ptQ, group_delta_ * -vec.y, group_delta_ * vec.x);
@@ -189,51 +231,77 @@ void ClipperOffset::DoSquare(Group& group, const Path64& path, size_t j, size_t
 	if (j == k)
 	{
 		PointD pt4 = PointD(pt3.x + vec.x * group_delta_, pt3.y + vec.y * group_delta_);
-		PointD pt = IntersectPoint(pt1, pt2, pt3, pt4);
+		PointD pt = ptQ;
+		GetSegmentIntersectPt(pt1, pt2, pt3, pt4, pt);
 		//get the second intersect point through reflecion
-		group.path_.push_back(Point64(ReflectPoint(pt, ptQ)));
+        path_out.emplace_back(ReflectPoint(pt, ptQ));
-		group.path_.push_back(Point64(pt));
+        path_out.emplace_back(pt);
 	}
 	else
 	{
 		PointD pt4 = GetPerpendicD(path[j], norms[k], group_delta_);
-		PointD pt = IntersectPoint(pt1, pt2, pt3, pt4);
+		PointD pt = ptQ;
-		group.path_.push_back(Point64(pt));
+		GetSegmentIntersectPt(pt1, pt2, pt3, pt4, pt);
+        path_out.emplace_back(pt);
 		//get the second intersect point through reflecion
-		group.path_.push_back(Point64(ReflectPoint(pt, ptQ)));
+        path_out.emplace_back(ReflectPoint(pt, ptQ));
 	}
 }
 
-void ClipperOffset::DoMiter(Group& group, const Path64& path, size_t j, size_t k, double cos_a)
+void ClipperOffset::DoMiter(const Path64& path, size_t j, size_t k, double cos_a)
 {
 	double q = group_delta_ / (cos_a + 1);
-	group.path_.push_back(Point64(
+#ifdef USINGZ
+    path_out.emplace_back(
 		path[j].x + (norms[k].x + norms[j].x) * q,
-		path[j].y + (norms[k].y + norms[j].y) * q));
+		path[j].y + (norms[k].y + norms[j].y) * q,
+        path[j].z);
+#else
+    path_out.emplace_back(
+		path[j].x + (norms[k].x + norms[j].x) * q,
+        path[j].y + (norms[k].y + norms[j].y) * q);
+#endif
 }
 
-void ClipperOffset::DoRound(Group& group, const Path64& path, size_t j, size_t k, double angle)
+void ClipperOffset::DoRound(const Path64& path, size_t j, size_t k, double angle)
 {
-	//even though angle may be negative this is a convex join
+	if (deltaCallback64_) {
-	Point64 pt = path[j];
+		// when deltaCallback64_ is assigned, group_delta_ won't be constant,
-	int steps = static_cast<int>(std::ceil(steps_per_rad_ * std::abs(angle)));
+		// so we'll need to do the following calculations for *every* vertex.
-	double step_sin = std::sin(angle / steps);
+		double abs_delta = std::fabs(group_delta_);
-	double step_cos = std::cos(angle / steps);
+		double arcTol = (arc_tolerance_ > floating_point_tolerance ?
-	
+			std::min(abs_delta, arc_tolerance_) : abs_delta * arc_const);
-	PointD pt2 = PointD(norms[k].x * group_delta_, norms[k].y * group_delta_);
+		double steps_per_360 = std::min(PI / std::acos(1 - arcTol / abs_delta), abs_delta * PI);
-	if (j == k) pt2.Negate();
+		step_sin_ = std::sin(2 * PI / steps_per_360);
-
+		step_cos_ = std::cos(2 * PI / steps_per_360);
-	group.path_.push_back(Point64(pt.x + pt2.x, pt.y + pt2.y));
+		if (group_delta_ < 0.0) step_sin_ = -step_sin_;
-	for (int i = 0; i < steps; i++)
+		steps_per_rad_ = steps_per_360 / (2 * PI);
-	{
-		pt2 = PointD(pt2.x * step_cos - step_sin * pt2.y,
-			pt2.x * step_sin + pt2.y * step_cos);
-		group.path_.push_back(Point64(pt.x + pt2.x, pt.y + pt2.y));
 	}
-	group.path_.push_back(GetPerpendic(path[j], norms[j], group_delta_));
+
+	Point64 pt = path[j];
+	PointD offsetVec = PointD(norms[k].x * group_delta_, norms[k].y * group_delta_);
+
+	if (j == k) offsetVec.Negate();
+#ifdef USINGZ
+    path_out.emplace_back(pt.x + offsetVec.x, pt.y + offsetVec.y, pt.z);
+#else
+    path_out.emplace_back(pt.x + offsetVec.x, pt.y + offsetVec.y);
+#endif
+	int steps = static_cast<int>(std::ceil(steps_per_rad_ * std::abs(angle))); // #448, #456
+	for (int i = 1; i < steps; ++i) // ie 1 less than steps
+	{
+		offsetVec = PointD(offsetVec.x * step_cos_ - step_sin_ * offsetVec.y,
+			offsetVec.x * step_sin_ + offsetVec.y * step_cos_);
+#ifdef USINGZ
+        path_out.emplace_back(pt.x + offsetVec.x, pt.y + offsetVec.y, pt.z);
+#else
+        path_out.emplace_back(pt.x + offsetVec.x, pt.y + offsetVec.y);
+#endif
+	}
+    path_out.emplace_back(GetPerpendic(path[j], norms[j], group_delta_));
 }
 
-void ClipperOffset::OffsetPoint(Group& group, Path64& path, size_t j, size_t& k)
+void ClipperOffset::OffsetPoint(Group& group, const Path64& path, size_t j, size_t k)
 {
 	// Let A = change in angle where edges join
 	// A == 0: ie no change in angle (flat join)
@@ -241,245 +309,346 @@ void ClipperOffset::OffsetPoint(Group& group, Path64& path, size_t j, size_t& k)
 	// sin(A) < 0: right turning
 	// cos(A) < 0: change in angle is more than 90 degree
 
-	if (path[j] == path[k]) { k = j; return; }
+	if (path[j] == path[k]) return;
 
 	double sin_a = CrossProduct(norms[j], norms[k]);
 	double cos_a = DotProduct(norms[j], norms[k]);
 	if (sin_a > 1.0) sin_a = 1.0;
 	else if (sin_a < -1.0) sin_a = -1.0;
 
-	bool almostNoAngle = AlmostZero(sin_a) && cos_a > 0;
+	if (deltaCallback64_) {
-	// when there's almost no angle of deviation or it's concave
+		group_delta_ = deltaCallback64_(path, norms, j, k);
-	if (almostNoAngle || (sin_a * group_delta_ < 0))
+		if (group.is_reversed) group_delta_ = -group_delta_;
-	{
-		Point64 p1 = Point64(
-			path[j].x + norms[k].x * group_delta_,
-			path[j].y + norms[k].y * group_delta_);
-		Point64 p2 = Point64(
-			path[j].x + norms[j].x * group_delta_,
-			path[j].y + norms[j].y * group_delta_);
-		group.path_.push_back(p1);
-		if (p1 != p2)
-		{
-			// when concave add an extra vertex to ensure neat clipping
-			if (!almostNoAngle) group.path_.push_back(path[j]);
-			group.path_.push_back(p2);
-		}
 	}
-	else // it's convex 
+	if (std::fabs(group_delta_) <= floating_point_tolerance)
 	{
-		if (join_type_ == JoinType::Round)
+        path_out.emplace_back(path[j]);
-			DoRound(group, path, j, k, std::atan2(sin_a, cos_a));
+		return;
-		else if (join_type_ == JoinType::Miter)
-		{
-			// miter unless the angle is so acute the miter would exceeds ML
-			if (cos_a > temp_lim_ - 1) DoMiter(group, path, j, k, cos_a);
-			else DoSquare(group, path, j, k);
-		}
-		// don't bother squaring angles that deviate < ~20 degrees because
-		// squaring will be indistinguishable from mitering and just be a lot slower
-		else if (cos_a > 0.9)
-			DoMiter(group, path, j, k, cos_a);			
-		else
-			DoSquare(group, path, j, k);			
 	}
-	k = j;
+
+	if (cos_a > -0.999 && (sin_a * group_delta_ < 0)) // test for concavity first (#593)
+	{
+		// is concave
+		// by far the simplest way to construct concave joins, especially those joining very 
+		// short segments, is to insert 3 points that produce negative regions. These regions 
+		// will be removed later by the finishing union operation. This is also the best way 
+		// to ensure that path reversals (ie over-shrunk paths) are removed.
+#ifdef USINGZ
+        path_out.emplace_back(GetPerpendic(path[j], norms[k], group_delta_), path[j].z);
+        path_out.emplace_back(path[j]); // (#405, #873, #916)
+        path_out.emplace_back(GetPerpendic(path[j], norms[j], group_delta_), path[j].z);
+#else
+        path_out.emplace_back(GetPerpendic(path[j], norms[k], group_delta_));
+        path_out.emplace_back(path[j]); // (#405, #873, #916)
+        path_out.emplace_back(GetPerpendic(path[j], norms[j], group_delta_));
+#endif
+	}
+	else if (cos_a > 0.999 && join_type_ != JoinType::Round)
+	{
+		// almost straight - less than 2.5 degree (#424, #482, #526 & #724)
+		DoMiter(path, j, k, cos_a);
+	}
+	else if (join_type_ == JoinType::Miter)
+	{
+		// miter unless the angle is sufficiently acute to exceed ML
+		if (cos_a > temp_lim_ - 1) DoMiter(path, j, k, cos_a);
+		else DoSquare(path, j, k);
+	}
+	else if (join_type_ == JoinType::Round)
+		DoRound(path, j, k, std::atan2(sin_a, cos_a));
+	else if ( join_type_ == JoinType::Bevel)
+		DoBevel(path, j, k);
+	else
+		DoSquare(path, j, k);
 }
 
-void ClipperOffset::OffsetPolygon(Group& group, Path64& path)
+void ClipperOffset::OffsetPolygon(Group& group, const Path64& path)
 {
-	group.path_.clear();
+	path_out.clear();
-	for (Path64::size_type i = 0, j = path.size() -1; i < path.size(); j = i, ++i)
+	for (Path64::size_type j = 0, k = path.size() - 1; j < path.size(); k = j, ++j)
-		OffsetPoint(group, path, i, j);
+		OffsetPoint(group, path, j, k);	
-	group.paths_out_.push_back(group.path_);
+    solution->emplace_back(path_out);
 }
 
-void ClipperOffset::OffsetOpenJoined(Group& group, Path64& path)
+void ClipperOffset::OffsetOpenJoined(Group& group, const Path64& path)
 {
 	OffsetPolygon(group, path);
-	std::reverse(path.begin(), path.end());
+	Path64 reverse_path(path);
-	BuildNormals(path);
+	std::reverse(reverse_path.begin(), reverse_path.end());
-	OffsetPolygon(group, path);
+
+	//rebuild normals 
+	std::reverse(norms.begin(), norms.end());
+    norms.emplace_back(norms[0]);
+	norms.erase(norms.begin());
+	NegatePath(norms);
+
+	OffsetPolygon(group, reverse_path);
 }
 
-void ClipperOffset::OffsetOpenPath(Group& group, Path64& path, EndType end_type)
+void ClipperOffset::OffsetOpenPath(Group& group, const Path64& path)
 {
-	group.path_.clear();
-
 	// do the line start cap
-	switch (end_type)
+	if (deltaCallback64_) group_delta_ = deltaCallback64_(path, norms, 0, 0);
+
+	if (std::fabs(group_delta_) <= floating_point_tolerance)
+        path_out.emplace_back(path[0]);
+	else
 	{
-	case EndType::Butt:
+		switch (end_type_)
-		group.path_.push_back(Point64(
+		{
-			path[0].x - norms[0].x * group_delta_,
+		case EndType::Butt:
-			path[0].y - norms[0].y * group_delta_));
+			DoBevel(path, 0, 0);
-		group.path_.push_back(GetPerpendic(path[0], norms[0], group_delta_));
+			break;
-		break;
+		case EndType::Round:
-	case EndType::Round:
+			DoRound(path, 0, 0, PI);
-		DoRound(group, path, 0,0, PI);
+			break;
-		break;
+		default:
-	default:
+			DoSquare(path, 0, 0);
-		DoSquare(group, path, 0, 0);
+			break;
-		break;
+		}
 	}
 
 	size_t highI = path.size() - 1;
-
 	// offset the left side going forward
-	for (Path64::size_type i = 1, k = 0; i < highI; ++i)
+	for (Path64::size_type j = 1, k = 0; j < highI; k = j, ++j)
-		OffsetPoint(group, path, i, k);
+		OffsetPoint(group, path, j, k);
 
-	// reverse normals 
+	// reverse normals
 	for (size_t i = highI; i > 0; --i)
 		norms[i] = PointD(-norms[i - 1].x, -norms[i - 1].y);
 	norms[0] = norms[highI];
 
 	// do the line end cap
-	switch (end_type)
+	if (deltaCallback64_)
+		group_delta_ = deltaCallback64_(path, norms, highI, highI);
+
+	if (std::fabs(group_delta_) <= floating_point_tolerance)
+        path_out.emplace_back(path[highI]);
+	else
 	{
-	case EndType::Butt:
+		switch (end_type_)
-		group.path_.push_back(Point64(
+		{
-			path[highI].x - norms[highI].x * group_delta_,
+		case EndType::Butt:
-			path[highI].y - norms[highI].y * group_delta_));
+			DoBevel(path, highI, highI);
-		group.path_.push_back(GetPerpendic(path[highI], norms[highI], group_delta_));
+			break;
-		break;
+		case EndType::Round:
-	case EndType::Round:
+			DoRound(path, highI, highI, PI);
-		DoRound(group, path, highI, highI, PI);
+			break;
-		break;
+		default:
-	default:
+			DoSquare(path, highI, highI);
-		DoSquare(group, path, highI, highI);
+			break;
-		break;
+		}
 	}
 
-	for (size_t i = highI, k = 0; i > 0; --i)
+	for (size_t j = highI -1, k = highI; j > 0; k = j, --j)
-		OffsetPoint(group, path, i, k);
+		OffsetPoint(group, path, j, k);
-	group.paths_out_.push_back(group.path_);
+    solution->emplace_back(path_out);
 }
 
-void ClipperOffset::DoGroupOffset(Group& group, double delta)
+void ClipperOffset::DoGroupOffset(Group& group)
 {
-	if (group.end_type_ != EndType::Polygon) delta = std::abs(delta) * 0.5;
+	if (group.end_type == EndType::Polygon)
-	bool isClosedPaths = IsClosedPath(group.end_type_);
-
-	if (isClosedPaths)
 	{
-		//the lowermost polygon must be an outer polygon. So we can use that as the
+		// a straight path (2 points) can now also be 'polygon' offset
-		//designated orientation for outer polygons (needed for tidy-up clipping)
+		// where the ends will be treated as (180 deg.) joins
-		Paths64::size_type lowestIdx = GetLowestPolygonIdx(group.paths_in_);
+        if (!group.lowest_path_idx.has_value()) delta_ = std::abs(delta_);
-    // nb: don't use the default orientation here ...
+		group_delta_ = (group.is_reversed) ? -delta_ : delta_;
-		double area = Area(group.paths_in_[lowestIdx]);
+	}
-		if (area == 0) return;	
-		group.is_reversed_ = (area < 0);
-		if (group.is_reversed_) delta = -delta;
-	} 
 	else
-		group.is_reversed_ = false;
+		group_delta_ = std::abs(delta_);// *0.5;
 
-	group_delta_ = delta;
+	double abs_delta = std::fabs(group_delta_);
-	abs_group_delta_ = std::abs(group_delta_);
+	join_type_	= group.join_type;
-	join_type_ = group.join_type_;
+	end_type_ = group.end_type;
 
-	double arcTol = (arc_tolerance_ > floating_point_tolerance ? arc_tolerance_
+	if (group.join_type == JoinType::Round || group.end_type == EndType::Round)
-		: std::log10(2 + abs_group_delta_) * default_arc_tolerance); // empirically derived
-
-//calculate a sensible number of steps (for 360 deg for the given offset
-	if (group.join_type_ == JoinType::Round || group.end_type_ == EndType::Round)
 	{
-		steps_per_rad_ = PI / std::acos(1 - arcTol / abs_group_delta_) / (PI *2);
+		// calculate the number of steps required to approximate a circle
+		// (see https://www.angusj.com/clipper2/Docs/Trigonometry.htm)
+		// arcTol - when arc_tolerance_ is undefined (0) then curve imprecision
+		// will be relative to the size of the offset (delta). Obviously very
+		//large offsets will almost always require much less precision.
+		double arcTol = (arc_tolerance_ > floating_point_tolerance) ?
+			std::min(abs_delta, arc_tolerance_) : abs_delta * arc_const;
+
+		double steps_per_360 = std::min(PI / std::acos(1 - arcTol / abs_delta), abs_delta * PI);
+		step_sin_ = std::sin(2 * PI / steps_per_360);
+		step_cos_ = std::cos(2 * PI / steps_per_360);
+		if (group_delta_ < 0.0) step_sin_ = -step_sin_;
+		steps_per_rad_ = steps_per_360 / (2 * PI);
 	}
 
-	bool is_closed_path = IsClosedPath(group.end_type_);
+	//double min_area = PI * Sqr(group_delta_);
-	Paths64::const_iterator path_iter;
+	Paths64::const_iterator path_in_it = group.paths_in.cbegin();
-	for(path_iter = group.paths_in_.cbegin(); path_iter != group.paths_in_.cend(); ++path_iter)
+	for ( ; path_in_it != group.paths_in.cend(); ++path_in_it)
 	{
-		Path64 path = StripDuplicates(*path_iter, is_closed_path);
+		Path64::size_type pathLen = path_in_it->size();
-		Path64::size_type cnt = path.size();
+		path_out.clear();
-		if (cnt == 0) continue;
 
-		if (cnt == 1) // single point - only valid with open paths
+		if (pathLen == 1) // single point
 		{
-			group.path_ = Path64();
+			if (deltaCallback64_)
-			//single vertex so build a circle or square ...
-			if (group.join_type_ == JoinType::Round)
 			{
-				double radius = abs_group_delta_;
+				group_delta_ = deltaCallback64_(*path_in_it, norms, 0, 0);
-				group.path_ = Ellipse(path[0], radius, radius);
+				if (group.is_reversed) group_delta_ = -group_delta_;
+				abs_delta = std::fabs(group_delta_);
+			}
+
+			if (group_delta_ < 1) continue;
+			const Point64& pt = (*path_in_it)[0];
+			//single vertex so build a circle or square ...
+			if (group.join_type == JoinType::Round)
+			{
+				double radius = abs_delta;
+                size_t steps = steps_per_rad_ > 0 ? static_cast<size_t>(std::ceil(steps_per_rad_ * 2 * PI)) : 0; //#617
+				path_out = Ellipse(pt, radius, radius, steps);
+#ifdef USINGZ
+				for (auto& p : path_out) p.z = pt.z;
+#endif
 			}
 			else
 			{
-				int d = (int)std::ceil(abs_group_delta_);
+				int d = (int)std::ceil(abs_delta);
-				Rect64 r = Rect64(path[0].x - d, path[0].y - d, path[0].x + d, path[0].y + d);
+				Rect64 r = Rect64(pt.x - d, pt.y - d, pt.x + d, pt.y + d);
-				group.path_ = r.AsPath();
+				path_out = r.AsPath();
+#ifdef USINGZ
+				for (auto& p : path_out) p.z = pt.z;
+#endif
 			}
-			group.paths_out_.push_back(group.path_);
-		}
-		else
-		{
-			BuildNormals(path);
-			if (group.end_type_ == EndType::Polygon) OffsetPolygon(group, path);
-			else if (group.end_type_ == EndType::Joined) OffsetOpenJoined(group, path);
-			else OffsetOpenPath(group, path, group.end_type_);
-		}
-	}
 
-	if (!merge_groups_)
+            solution->emplace_back(path_out);
-	{
+			continue;
-		//clean up self-intersections ...
+		} // end of offsetting a single point
-		Clipper64 c;
-		c.PreserveCollinear = false;
-		//the solution should retain the orientation of the input
-		c.ReverseSolution = reverse_solution_ != group.is_reversed_;
-		c.AddSubject(group.paths_out_);
-		if (group.is_reversed_)
-			c.Execute(ClipType::Union, FillRule::Negative, group.paths_out_);
-		else
-			c.Execute(ClipType::Union, FillRule::Positive, group.paths_out_);
-	}
 
-	solution.reserve(solution.size() + group.paths_out_.size());
+		if ((pathLen == 2) && (group.end_type == EndType::Joined))
-	copy(group.paths_out_.begin(), group.paths_out_.end(), back_inserter(solution));
+			end_type_ = (group.join_type == JoinType::Round) ?
-	group.paths_out_.clear();
+			  EndType::Round :
+			  EndType::Square;
+
+		BuildNormals(*path_in_it);
+		if (end_type_ == EndType::Polygon) OffsetPolygon(group, *path_in_it);
+		else if (end_type_ == EndType::Joined) OffsetOpenJoined(group, *path_in_it);
+		else OffsetOpenPath(group, *path_in_it);
+	}
 }
 
-Paths64 ClipperOffset::Execute(double delta)
+#ifdef USINGZ
+void ClipperOffset::ZCB(const Point64& bot1, const Point64& top1,
+	const Point64& bot2, const Point64& top2, Point64& ip)
 {
-	solution.clear();
+	if (bot1.z && ((bot1.z == bot2.z) || (bot1.z == top2.z))) ip.z = bot1.z;
-	if (std::abs(delta) < default_arc_tolerance)
+	else if (bot2.z && (bot2.z == top1.z)) ip.z = bot2.z;
-	{
+	else if (top1.z && (top1.z == top2.z)) ip.z = top1.z;
-		for (const Group& group : groups_)
+	else if (zCallback64_) zCallback64_(bot1, top1, bot2, top2, ip);
+}
+#endif
+
+size_t ClipperOffset::CalcSolutionCapacity()
+{
+	size_t result = 0;
+	for (const Group& g : groups_)
+		result += (g.end_type == EndType::Joined) ? g.paths_in.size() * 2 : g.paths_in.size();
+	return result;
+}
+
+bool ClipperOffset::CheckReverseOrientation()
+{
+	// nb: this assumes there's consistency in orientation between groups
+	bool is_reversed_orientation = false;
+	for (const Group& g : groups_)
+		if (g.end_type == EndType::Polygon)
 		{
-			solution.reserve(solution.size() + group.paths_in_.size());
+			is_reversed_orientation = g.is_reversed;
-			copy(group.paths_in_.begin(), group.paths_in_.end(), back_inserter(solution));
+			break;
+		}
+	return is_reversed_orientation;
+}
+
+void ClipperOffset::ExecuteInternal(double delta)
+{
+	error_code_ = 0;
+	if (groups_.size() == 0) return;
+	solution->reserve(CalcSolutionCapacity());
+
+	if (std::abs(delta) < 0.5) // ie: offset is insignificant
+	{
+		Paths64::size_type sol_size = 0;
+		for (const Group& group : groups_) sol_size += group.paths_in.size();
+		solution->reserve(sol_size);
+		for (const Group& group : groups_)
+			copy(group.paths_in.begin(), group.paths_in.end(), back_inserter(*solution));
+	}
+	else
+	{
+
+		temp_lim_ = (miter_limit_ <= 1) ?
+			2.0 :
+			2.0 / (miter_limit_ * miter_limit_);
+
+		delta_ = delta;
+		std::vector<Group>::iterator git;
+		for (git = groups_.begin(); git != groups_.end(); ++git)
+		{
+			DoGroupOffset(*git);
+			if (!error_code_) continue; // all OK
+			solution->clear();
 		}
-		return solution;
 	}
 
-	temp_lim_ = (miter_limit_ <= 1) ? 
+	if (!solution->size()) return;
-		2.0 : 
-		2.0 / (miter_limit_ * miter_limit_);
 
-	std::vector<Group>::iterator groups_iter;
+		bool paths_reversed = CheckReverseOrientation();
-	for (groups_iter = groups_.begin(); 
+	//clean up self-intersections ...
-		groups_iter != groups_.end(); ++groups_iter)
+	Clipper64 c;
+	c.PreserveCollinear(false);
+	//the solution should retain the orientation of the input
+	c.ReverseSolution(reverse_solution_ != paths_reversed);
+#ifdef USINGZ
+	auto fp = std::bind(&ClipperOffset::ZCB, this, std::placeholders::_1,
+		std::placeholders::_2, std::placeholders::_3,
+		std::placeholders::_4, std::placeholders::_5);
+	c.SetZCallback(fp);
+#endif
+	c.AddSubject(*solution);
+	if (solution_tree)
 	{
-		DoGroupOffset(*groups_iter, delta);
+		if (paths_reversed)
-	}
+			c.Execute(ClipType::Union, FillRule::Negative, *solution_tree);
-
-	if (merge_groups_ && groups_.size() > 0)
-	{
-		//clean up self-intersections ...
-		Clipper64 c;
-		c.PreserveCollinear = false;
-		//the solution should retain the orientation of the input
-		c.ReverseSolution = reverse_solution_ != groups_[0].is_reversed_;
-
-		c.AddSubject(solution);
-		if (groups_[0].is_reversed_)
-			c.Execute(ClipType::Union, FillRule::Negative, solution);
 		else
-			c.Execute(ClipType::Union, FillRule::Positive, solution);
+			c.Execute(ClipType::Union, FillRule::Positive, *solution_tree);
 	}
-	return solution;
+	else
+	{
+		if (paths_reversed)
+			c.Execute(ClipType::Union, FillRule::Negative, *solution);
+		else
+			c.Execute(ClipType::Union, FillRule::Positive, *solution);
+	}
+}
+
+void ClipperOffset::Execute(double delta, Paths64& paths64)
+{
+	paths64.clear();
+	solution = &paths64;
+	solution_tree = nullptr;
+	ExecuteInternal(delta);
+}
+
+
+void ClipperOffset::Execute(double delta, PolyTree64& polytree)
+{
+	polytree.Clear();
+	solution_tree = &polytree;
+	solution = new Paths64();
+	ExecuteInternal(delta);
+	delete solution;
+	solution = nullptr;
+}
+
+void ClipperOffset::Execute(DeltaCallback64 delta_cb, Paths64& paths)
+{
+	deltaCallback64_ = delta_cb;
+	Execute(1.0, paths);
 }
 
 } // namespace

src/libslic3r/Clipper2Utils.cpp

@@ -57,7 +57,7 @@ static ExPolygons PolyTreeToExPolygons(Clipper2Lib::PolyTree64 &&polytree)
             for (int i = 0; i < polynode.Count(); ++i) {
                 (*expolygons)[cnt].holes[i].points = Path64ToPoints(polynode[i]->Polygon());
                 // Add outer polygons contained by (nested within) holes.
-                for (int j = 0; j < polynode[i]->Count(); ++j) PolyTreeToExPolygonsRecursive(std::move(*polynode[i]->Childs(j)), expolygons);
+                for (int j = 0; j < polynode[i]->Count(); ++j) PolyTreeToExPolygonsRecursive(std::move(*polynode[i]->Child(j)), expolygons);
             }
         }
 
@@ -65,7 +65,7 @@ static ExPolygons PolyTreeToExPolygons(Clipper2Lib::PolyTree64 &&polytree)
         {
             size_t cnt = 1;
             for (size_t i = 0; i < polynode.Count(); ++i) {
-                for (size_t j = 0; j < polynode.Childs(i)->Count(); ++j) cnt += PolyTreeCountExPolygons(*polynode.Childs(i)->Childs(j));
+                for (size_t j = 0; j < polynode.Child(i)->Count(); ++j) cnt += PolyTreeCountExPolygons(*polynode.Child(i)->Child(j));
             }
             return cnt;
         }