From 2f8d472d7d038cafca49c67b976260f045e1f318 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Tue, 31 Dec 2019 17:23:29 +0100
Subject: [PATCH] - cleaned up the map drawer by using a real triangulator.

Immediate benefit: almost 200 lines of bona-fide Kencode go to the dumpster.
---
 source/build/src/engine.cpp          |  11 +-
 source/build/src/polymost.cpp        | 188 -------
 source/common/2d/v_2ddrawer.cpp      |  87 ++-
 source/common/2d/v_2ddrawer.h        |   3 +-
 source/thirdparty/include/earcut.hpp | 790 +++++++++++++++++++++++++++
 5 files changed, 874 insertions(+), 205 deletions(-)
 create mode 100644 source/thirdparty/include/earcut.hpp

diff --git a/source/build/src/engine.cpp b/source/build/src/engine.cpp
index 2f9ad83e4..d15e4a5fa 100644
--- a/source/build/src/engine.cpp
+++ b/source/build/src/engine.cpp
@@ -8274,7 +8274,16 @@ static void renderFillPolygon(int32_t npoints)
         if ((unsigned)xb1[z] >= (unsigned)npoints)
             xb1[z] = 0;
 
-    polymost_fillpolygon(npoints);
+    FVector2 xtex, ytex, otex;
+    int x1 = mulscale16(globalx1, xyaspect);
+    int y2 = mulscale16(globaly2, xyaspect);
+    xtex.X = ((float)asm1) * (1.f / 4294967296.f);
+    xtex.Y = ((float)asm2) * (1.f / 4294967296.f);
+    ytex.X = ((float)x1) * (1.f / 4294967296.f);
+    ytex.Y = ((float)y2) * (-1.f / 4294967296.f);
+    otex.X = (fxdim * xtex.X + fydim * ytex.X) * -0.5f + fglobalposx * (1.f / 4294967296.f);
+    otex.Y = (fxdim * xtex.Y + fydim * ytex.Y) * -0.5f - fglobalposy * (1.f / 4294967296.f);
+    twod->FillPolygon(rx1, ry1, xb1, npoints, globalpicnum, globalpal, globalshade, globalorientation, xtex, ytex, otex);
 }
 
 //
diff --git a/source/build/src/polymost.cpp b/source/build/src/polymost.cpp
index 0a97657f0..6e6571e47 100644
--- a/source/build/src/polymost.cpp
+++ b/source/build/src/polymost.cpp
@@ -4719,194 +4719,6 @@ void polymost_dorotatespritemodel(int32_t sx, int32_t sy, int32_t z, int16_t a,
     polymost_identityrotmat();
 }
 
-#include "v_2ddrawer.h"
-static void drawtrap(float x0, float x1, float y0, float x2, float x3, float y1, float *trapextx, F2DPolygons *poly)
-{
-    if (y0 == y1) return;
-
-    float px[4], py[4];
-    int n = 3;
-
-    px[0] = x0; py[0] = y0;  py[2] = y1;
-    if (x0 == x1) { px[1] = x3; py[1] = y1; px[2] = x2; }
-    else if (x2 == x3) { px[1] = x1; py[1] = y0; px[2] = x3; }
-    else               { px[1] = x1; py[1] = y0; px[2] = x3; px[3] = x2; py[3] = y1; n = 4; }
-
-	auto vt = poly->AllocVertices(n);
-    for (int i=0; i<n; i++)
-    {
-        px[i] = min(max(px[i],trapextx[0]),trapextx[1]);
-        poly->vertices[vt++] = { px[i], py[i], float(px[i] * xtex.u + py[i] * ytex.u + otex.u), float(px[i] * xtex.v + py[i] * ytex.v + otex.v) };
-    }
-}
-
-static void tessectrap(const float *px, const float *py, const int32_t *point2, int32_t numpoints, F2DPolygons* poly)
-{
-    float trapextx[2];
-    float x0, x1, m0, m1;
-    int32_t i, j, k, z, i0, i1, i2, i3, npoints, gap, numrst;
-
-    static int32_t allocpoints = 0, *slist = 0, *npoint2 = 0;
-    typedef struct { float x, y, xi; int32_t i; } raster;
-    static raster *rst = 0;
-    if (numpoints+16 > allocpoints) //16 for safety
-    {
-        allocpoints = numpoints+16;
-        rst = (raster *)Xrealloc(rst,allocpoints*sizeof(raster));
-        slist = (int32_t *)Xrealloc(slist,allocpoints*sizeof(int32_t));
-        npoint2 = (int32_t *)Xrealloc(npoint2,allocpoints*sizeof(int32_t));
-    }
-
-    //Remove unnecessary collinear points:
-    for (i=0; i<numpoints; i++) npoint2[i] = point2[i];
-    npoints = numpoints; z = 0;
-    for (i=0; i<numpoints; i++)
-    {
-        j = npoint2[i]; if ((i < numpoints-1) && (point2[i] < i)) z = 3;
-        if (j < 0) continue;
-        k = npoint2[j];
-        m0 = (px[j]-px[i])*(py[k]-py[j]);
-        m1 = (py[j]-py[i])*(px[k]-px[j]);
-        if (m0 < m1) { z |= 1; continue; }
-        if (m0 > m1) { z |= 2; continue; }
-        npoint2[i] = k; npoint2[j] = -1; npoints--; i--; //collinear
-    }
-    if (!z) return;
-    trapextx[0] = trapextx[1] = px[0];
-    for (i=j=0; i<numpoints; i++)
-    {
-        if (npoint2[i] < 0) continue;
-        if (px[i] < trapextx[0]) trapextx[0] = px[i];
-        if (px[i] > trapextx[1]) trapextx[1] = px[i];
-        slist[j++] = i;
-    }
-    if (z != 3) //Simple polygon... early out
-    {
-		auto vt = poly->AllocVertices(npoints);
-
-        for (i=0; i<npoints; i++)
-        {
-            j = slist[i];
-            poly->vertices[vt++] = { px[j], py[j], float(px[j] * xtex.u + py[j] * ytex.u + otex.u), float(px[j] * xtex.v + py[j] * ytex.v + otex.v) };
-        }
-        return;
-    }
-
-    //Sort points by y's
-    for (gap=(npoints>>1); gap; gap>>=1)
-        for (i=0; i<npoints-gap; i++)
-            for (j=i; j>=0; j-=gap)
-            {
-                if (py[npoint2[slist[j]]] <= py[npoint2[slist[j+gap]]]) break;
-                k = slist[j]; slist[j] = slist[j+gap]; slist[j+gap] = k;
-            }
-
-    numrst = 0;
-    for (z=0; z<npoints; z++)
-    {
-        i0 = slist[z]; i1 = npoint2[i0]; if (py[i0] == py[i1]) continue;
-        i2 = i1; i3 = npoint2[i1];
-        if (py[i1] == py[i3]) { i2 = i3; i3 = npoint2[i3]; }
-
-        //i0        i3
-        //  \      /
-        //   i1--i2
-        //  /      \ ~
-        //i0        i3
-
-        if ((py[i1] < py[i0]) && (py[i2] < py[i3])) //Insert raster
-        {
-            for (i=numrst; i>0; i--)
-            {
-                if (rst[i-1].xi*(py[i1]-rst[i-1].y) + rst[i-1].x < px[i1]) break;
-                rst[i+1] = rst[i-1];
-            }
-            numrst += 2;
-
-            if (i&1) //split inside area
-            {
-                j = i-1;
-
-                x0 = (py[i1] - rst[j  ].y)*rst[j  ].xi + rst[j  ].x;
-                x1 = (py[i1] - rst[j+1].y)*rst[j+1].xi + rst[j+1].x;
-                drawtrap(rst[j].x,rst[j+1].x,rst[j].y,x0,x1,py[i1], trapextx, poly);
-                rst[j  ].x = x0; rst[j  ].y = py[i1];
-                rst[j+3].x = x1; rst[j+3].y = py[i1];
-            }
-
-            m0 = (px[i0]-px[i1]) / (py[i0]-py[i1]);
-            m1 = (px[i3]-px[i2]) / (py[i3]-py[i2]);
-            j = ((px[i1] > px[i2]) || ((i1 == i2) && (m0 >= m1))) + i;
-            k = (i<<1)+1 - j;
-            rst[j].i = i0; rst[j].xi = m0; rst[j].x = px[i1]; rst[j].y = py[i1];
-            rst[k].i = i3; rst[k].xi = m1; rst[k].x = px[i2]; rst[k].y = py[i2];
-        }
-        else
-        {
-            //NOTE:don't count backwards!
-            if (i1 == i2) { for (i=0; i<numrst; i++) if (rst[i].i == i1) break; }
-            else { for (i=0; i<numrst; i++) if ((rst[i].i == i1) || (rst[i].i == i2)) break; }
-            j = i&~1;
-
-            if ((py[i1] > py[i0]) && (py[i2] > py[i3])) //Delete raster
-            {
-                for (; j<=i+1; j+=2)
-                {
-                    x0 = (py[i1] - rst[j  ].y)*rst[j  ].xi + rst[j  ].x;
-                    if ((i == j) && (i1 == i2)) x1 = x0; else x1 = (py[i1] - rst[j+1].y)*rst[j+1].xi + rst[j+1].x;
-                    drawtrap(rst[j].x,rst[j+1].x,rst[j].y,x0,x1,py[i1], trapextx, poly);
-                    rst[j  ].x = x0; rst[j  ].y = py[i1];
-                    rst[j+1].x = x1; rst[j+1].y = py[i1];
-                }
-                numrst -= 2; for (; i<numrst; i++) rst[i] = rst[i+2];
-            }
-            else
-            {
-                x0 = (py[i1] - rst[j  ].y)*rst[j  ].xi + rst[j  ].x;
-                x1 = (py[i1] - rst[j+1].y)*rst[j+1].xi + rst[j+1].x;
-                drawtrap(rst[j].x,rst[j+1].x,rst[j].y,x0,x1,py[i1], trapextx, poly);
-                rst[j  ].x = x0; rst[j  ].y = py[i1];
-                rst[j+1].x = x1; rst[j+1].y = py[i1];
-
-                if (py[i0] < py[i3]) { rst[i].x = px[i2]; rst[i].y = py[i2]; rst[i].i = i3; }
-                else { rst[i].x = px[i1]; rst[i].y = py[i1]; rst[i].i = i0; }
-                rst[i].xi = (px[rst[i].i] - rst[i].x) / (py[rst[i].i] - py[i1]);
-            }
-        }
-    }
-}
-
-static F2DPolygons poly;
-void polymost_fillpolygon(int32_t npoints)
-{
-    poly.vertices.Clear();
-    poly.indices.Clear();
-    polymost_outputGLDebugMessage(3, "polymost_fillpolygon(npoints:%d)", npoints);
-
-    globvis2 = 0;
-
-    globalx1 = mulscale16(globalx1,xyaspect);
-    globaly2 = mulscale16(globaly2,xyaspect);
-    xtex.u = ((float)asm1) * (1.f / 4294967296.f);
-    xtex.v = ((float)asm2) * (1.f / 4294967296.f);
-    ytex.u = ((float)globalx1) * (1.f / 4294967296.f);
-    ytex.v = ((float)globaly2) * (-1.f / 4294967296.f);
-    otex.u = (fxdim * xtex.u + fydim * ytex.u) * -0.5f + fglobalposx * (1.f / 4294967296.f);
-    otex.v = (fxdim * xtex.v + fydim * ytex.v) * -0.5f - fglobalposy * (1.f / 4294967296.f);
-
-    //Convert int32_t to float (in-place)
-    for (bssize_t i=0; i<npoints; ++i)
-    {
-        ((float *)rx1)[i] = ((float)rx1[i])*(1.0f/4096.f);
-        ((float *)ry1)[i] = ((float)ry1[i])*(1.0f/4096.f);
-    }
-    tessectrap((float*)rx1, (float*)ry1, xb1, npoints, &poly);
-
-    uint8_t const maskprops = (globalorientation>>7)&DAMETH_MASKPROPS;
-    twod->AddPoly(TileFiles.tiles[globalpicnum], poly, globalpal, globalshade, maskprops);
-}
-
-
 
 void polymost_initosdfuncs(void)
 {
diff --git a/source/common/2d/v_2ddrawer.cpp b/source/common/2d/v_2ddrawer.cpp
index 89f8616ca..b5fd90d95 100644
--- a/source/common/2d/v_2ddrawer.cpp
+++ b/source/common/2d/v_2ddrawer.cpp
@@ -32,6 +32,7 @@
 #include "drawparms.h"
 #include "vectors.h"
 #include "gamecvars.h"
+#include "earcut.hpp"
 //#include "doomtype.h"
 #include "templates.h"
 //#include "r_utility.h"
@@ -706,7 +707,7 @@ void F2DDrawer::rotatesprite(int32_t sx, int32_t sy, int32_t z, int16_t a, int16
 //
 //==========================================================================
 
-void F2DDrawer::AddPoly(FTexture* img, F2DPolygons& poly, int palette, int shade, int maskprops)
+void F2DDrawer::AddPoly(FTexture* img, FVector4* vt, size_t vtcount, unsigned int* ind, size_t idxcount, int palette, int shade, int maskprops)
 {
 	RenderCommand dg = {};
 	int method = 0;
@@ -731,32 +732,88 @@ void F2DDrawer::AddPoly(FTexture* img, F2DPolygons& poly, int palette, int shade
 	}
 	dg.mTexture = img;
 	dg.mRemapIndex = palette | (shade << 16);
-	dg.mVertCount = poly.vertices.Size();
-	dg.mVertIndex = (int)mVertices.Reserve(dg.mVertCount);
+	dg.mVertCount = vtcount;
+	dg.mVertIndex = (int)mVertices.Reserve(vtcount);
 	dg.mRenderStyle = LegacyRenderStyles[STYLE_Translucent];
 	dg.mIndexIndex = mIndices.Size();
 	dg.mFlags |= DTF_Wrap;
 	auto ptr = &mVertices[dg.mVertIndex];
 
-	for (auto& sv : poly.vertices)
+	for (size_t i=0;i<vtcount;i++)
 	{
-		ptr->Set(sv.X, sv.Y, 0.f, sv.Z, sv.W, p);
+		ptr->Set(vt[i].X, vt[i].Y, 0.f, vt[i].Z, vt[i].W, p);
 		ptr++;
 	}
 
-	int start = dg.mVertIndex;
-
-	for (unsigned i = 0; i < poly.indices.Size(); i++)
+	dg.mIndexIndex = mIndices.Size();
+	mIndices.Reserve(idxcount);
+	for (size_t i = 0; i < idxcount; i++)
 	{
-		for (int vv = 2; vv < poly.indices[i]; vv++)
-		{
-			AddIndices(start, 3, 0, vv - 1, vv);
-		}
-		start += poly.indices[i];
+		mIndices[dg.mIndexIndex + i] = ind[i] + dg.mVertIndex;
 	}
-
-	dg.mIndexCount = mIndices.Size() - dg.mIndexIndex;
+	dg.mIndexCount = idxcount;
 	AddCommand(&dg);
 }
 
+//==========================================================================
+//
+//
+//
+//==========================================================================
+
+void F2DDrawer::FillPolygon(int *rx1, int *ry1, int *xb1, int32_t npoints, int picnum, int palette, int shade, int props, const FVector2& xtex, const FVector2& ytex, const FVector2 &otex)
+{
+	//Convert int32_t to float (in-place)
+	TArray<FVector4> points(npoints, true);
+	using Point = std::pair<float, float>;
+	std::vector<std::vector<Point>> polygon;
+	std::vector<Point>* curPoly;
+
+	polygon.resize(1);
+	curPoly = &polygon.back();
+
+	for (bssize_t i = 0; i < npoints; ++i)
+	{
+		auto X = ((float)rx1[i]) * (1.0f / 4096.f);
+		auto Y = ((float)ry1[i]) * (1.0f / 4096.f);
+		curPoly->push_back(std::make_pair(X, Y));
+		if (xb1[i] < i && i < npoints - 1)
+		{
+			polygon.resize(polygon.size() + 1);
+			curPoly = &polygon.back();
+		}
+	}
+	// Now make sure that the outer boundary is the first polygon by picking a point that's as much to the outside as possible.
+	int outer = 0;
+	float minx = FLT_MAX;
+	float miny = FLT_MAX;
+	for (size_t a = 0; a < polygon.size(); a++)
+	{
+		for (auto& pt : polygon[a])
+		{
+			if (pt.first < minx || pt.first == minx && pt.second < miny)
+			{
+				minx = pt.first;
+				miny = pt.second;
+				outer = a;
+			}
+		}
+	}
+	if (outer != 0) std::swap(polygon[0], polygon[outer]);
+	auto indices = mapbox::earcut(polygon);
+
+	int p = 0;
+	for (size_t a = 0; a < polygon.size(); a++)
+	{
+		for (auto& pt : polygon[a])
+		{
+			FVector4 point = { pt.first, pt.second, float(pt.first * xtex.X + pt.second * ytex.X + otex.X), float(pt.first * xtex.Y + pt.second * ytex.Y + otex.Y) };
+			points[p++] = point;
+		}
+	}
+
+	AddPoly(TileFiles.tiles[picnum], points.Data(), points.Size(), indices.data(), indices.size(), palette, shade, (props >> 7)& DAMETH_MASKPROPS);
+}
+
+
 
diff --git a/source/common/2d/v_2ddrawer.h b/source/common/2d/v_2ddrawer.h
index adad2f58b..f81643866 100644
--- a/source/common/2d/v_2ddrawer.h
+++ b/source/common/2d/v_2ddrawer.h
@@ -127,7 +127,8 @@ public:
 
 public:
 	void AddTexture(FTexture *img, DrawParms &parms);
-	void AddPoly(FTexture* img, F2DPolygons& poly, int palette, int shade, int maskprops);
+	void AddPoly(FTexture* img, FVector4 *vt, size_t vtcount, unsigned int *ind, size_t idxcount, int palette, int shade, int maskprops);
+	void FillPolygon(int* rx1, int* ry1, int* xb1, int32_t npoints, int picnum, int palette, int shade, int props, const FVector2& xtex, const FVector2& ytex, const FVector2& otex);
 	void AddFlatFill(int left, int top, int right, int bottom, FTexture *src, bool local_origin);
 
 	void AddColorOnlyQuad(int left, int top, int width, int height, PalEntry color, FRenderStyle *style = nullptr);
diff --git a/source/thirdparty/include/earcut.hpp b/source/thirdparty/include/earcut.hpp
new file mode 100644
index 000000000..d6a2c9798
--- /dev/null
+++ b/source/thirdparty/include/earcut.hpp
@@ -0,0 +1,790 @@
+/*
+ISC License
+
+Copyright (c) 2015, Mapbox
+
+Permission to use, copy, modify, and/or distribute this software for any purpose
+with or without fee is hereby granted, provided that the above copyright notice
+and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE. 
+*/
+#pragma once
+
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <memory>
+#include <vector>
+
+namespace mapbox {
+
+namespace util {
+
+template <std::size_t I, typename T> struct nth {
+    inline static typename std::tuple_element<I, T>::type
+    get(const T& t) { return std::get<I>(t); };
+};
+
+}
+
+namespace detail {
+
+template <typename N = uint32_t>
+class Earcut {
+public:
+    std::vector<N> indices;
+    std::size_t vertices = 0;
+
+    template <typename Polygon>
+    void operator()(const Polygon& points);
+
+private:
+    struct Node {
+        Node(N index, double x_, double y_) : i(index), x(x_), y(y_) {}
+        Node(const Node&) = delete;
+        Node& operator=(const Node&) = delete;
+        Node(Node&&) = delete;
+        Node& operator=(Node&&) = delete;
+
+        const N i;
+        const double x;
+        const double y;
+
+        // previous and next vertice nodes in a polygon ring
+        Node* prev = nullptr;
+        Node* next = nullptr;
+
+        // z-order curve value
+        int32_t z = 0;
+
+        // previous and next nodes in z-order
+        Node* prevZ = nullptr;
+        Node* nextZ = nullptr;
+
+        // indicates whether this is a steiner point
+        bool steiner = false;
+    };
+
+    template <typename Ring> Node* linkedList(const Ring& points, const bool clockwise);
+    Node* filterPoints(Node* start, Node* end = nullptr);
+    void earcutLinked(Node* ear, int pass = 0);
+    bool isEar(Node* ear);
+    bool isEarHashed(Node* ear);
+    Node* cureLocalIntersections(Node* start);
+    void splitEarcut(Node* start);
+    template <typename Polygon> Node* eliminateHoles(const Polygon& points, Node* outerNode);
+    void eliminateHole(Node* hole, Node* outerNode);
+    Node* findHoleBridge(Node* hole, Node* outerNode);
+    void indexCurve(Node* start);
+    Node* sortLinked(Node* list);
+    int32_t zOrder(const double x_, const double y_);
+    Node* getLeftmost(Node* start);
+    bool pointInTriangle(double ax, double ay, double bx, double by, double cx, double cy, double px, double py) const;
+    bool isValidDiagonal(Node* a, Node* b);
+    double area(const Node* p, const Node* q, const Node* r) const;
+    bool equals(const Node* p1, const Node* p2);
+    bool intersects(const Node* p1, const Node* q1, const Node* p2, const Node* q2);
+    bool intersectsPolygon(const Node* a, const Node* b);
+    bool locallyInside(const Node* a, const Node* b);
+    bool middleInside(const Node* a, const Node* b);
+    Node* splitPolygon(Node* a, Node* b);
+    template <typename Point> Node* insertNode(std::size_t i, const Point& p, Node* last);
+    void removeNode(Node* p);
+
+    bool hashing;
+    double minX, maxX;
+    double minY, maxY;
+    double inv_size = 0;
+
+    template <typename T, typename Alloc = std::allocator<T>>
+    class ObjectPool {
+    public:
+        ObjectPool() { }
+        ObjectPool(std::size_t blockSize_) {
+            reset(blockSize_);
+        }
+        ~ObjectPool() {
+            clear();
+        }
+        template <typename... Args>
+        T* construct(Args&&... args) {
+            if (currentIndex >= blockSize) {
+                currentBlock = alloc.allocate(blockSize);
+                allocations.emplace_back(currentBlock);
+                currentIndex = 0;
+            }
+            T* object = &currentBlock[currentIndex++];
+            alloc.construct(object, std::forward<Args>(args)...);
+            return object;
+        }
+        void reset(std::size_t newBlockSize) {
+            for (auto allocation : allocations) alloc.deallocate(allocation, blockSize);
+            allocations.clear();
+            blockSize = std::max<std::size_t>(1, newBlockSize);
+            currentBlock = nullptr;
+            currentIndex = blockSize;
+        }
+        void clear() { reset(blockSize); }
+    private:
+        T* currentBlock = nullptr;
+        std::size_t currentIndex = 1;
+        std::size_t blockSize = 1;
+        std::vector<T*> allocations;
+        Alloc alloc;
+    };
+    ObjectPool<Node> nodes;
+};
+
+template <typename N> template <typename Polygon>
+void Earcut<N>::operator()(const Polygon& points) {
+    // reset
+    indices.clear();
+    vertices = 0;
+
+    if (points.empty()) return;
+
+    double x;
+    double y;
+    int threshold = 80;
+    std::size_t len = 0;
+
+    for (size_t i = 0; threshold >= 0 && i < points.size(); i++) {
+        threshold -= static_cast<int>(points[i].size());
+        len += points[i].size();
+    }
+
+    //estimate size of nodes and indices
+    nodes.reset(len * 3 / 2);
+    indices.reserve(len + points[0].size());
+
+    Node* outerNode = linkedList(points[0], true);
+    if (!outerNode) return;
+
+    if (points.size() > 1) outerNode = eliminateHoles(points, outerNode);
+
+    // if the shape is not too simple, we'll use z-order curve hash later; calculate polygon bbox
+    hashing = threshold < 0;
+    if (hashing) {
+        Node* p = outerNode->next;
+        minX = maxX = outerNode->x;
+        minY = maxY = outerNode->y;
+        do {
+            x = p->x;
+            y = p->y;
+            minX = std::min<double>(minX, x);
+            minY = std::min<double>(minY, y);
+            maxX = std::max<double>(maxX, x);
+            maxY = std::max<double>(maxY, y);
+            p = p->next;
+        } while (p != outerNode);
+
+        // minX, minY and size are later used to transform coords into integers for z-order calculation
+        inv_size = std::max<double>(maxX - minX, maxY - minY);
+        inv_size = inv_size != .0 ? (1. / inv_size) : .0;
+    }
+
+    earcutLinked(outerNode);
+
+    nodes.clear();
+}
+
+// create a circular doubly linked list from polygon points in the specified winding order
+template <typename N> template <typename Ring>
+typename Earcut<N>::Node*
+Earcut<N>::linkedList(const Ring& points, const bool clockwise) {
+    using Point = typename Ring::value_type;
+    double sum = 0;
+    const std::size_t len = points.size();
+    std::size_t i, j;
+    Node* last = nullptr;
+
+    // calculate original winding order of a polygon ring
+    for (i = 0, j = len > 0 ? len - 1 : 0; i < len; j = i++) {
+        const auto& p1 = points[i];
+        const auto& p2 = points[j];
+        const double p20 = util::nth<0, Point>::get(p2);
+        const double p10 = util::nth<0, Point>::get(p1);
+        const double p11 = util::nth<1, Point>::get(p1);
+        const double p21 = util::nth<1, Point>::get(p2);
+        sum += (p20 - p10) * (p11 + p21);
+    }
+
+    // link points into circular doubly-linked list in the specified winding order
+    if (clockwise == (sum > 0)) {
+        for (i = 0; i < len; i++) last = insertNode(vertices + i, points[i], last);
+    } else {
+        for (i = len; i-- > 0;) last = insertNode(vertices + i, points[i], last);
+    }
+
+    if (last && equals(last, last->next)) {
+        removeNode(last);
+        last = last->next;
+    }
+
+    vertices += len;
+
+    return last;
+}
+
+// eliminate colinear or duplicate points
+template <typename N>
+typename Earcut<N>::Node*
+Earcut<N>::filterPoints(Node* start, Node* end) {
+    if (!end) end = start;
+
+    Node* p = start;
+    bool again;
+    do {
+        again = false;
+
+        if (!p->steiner && (equals(p, p->next) /*|| area(p->prev, p, p->next) == 0*/)) 
+		{
+            removeNode(p);
+            p = end = p->prev;
+
+            if (p == p->next) break;
+            again = true;
+
+        } else {
+            p = p->next;
+        }
+    } while (again || p != end);
+
+    return end;
+}
+
+// main ear slicing loop which triangulates a polygon (given as a linked list)
+template <typename N>
+void Earcut<N>::earcutLinked(Node* ear, int pass) {
+    if (!ear) return;
+
+    // interlink polygon nodes in z-order
+    if (!pass && hashing) indexCurve(ear);
+
+    Node* stop = ear;
+    Node* prev;
+    Node* next;
+
+    int iterations = 0;
+
+    // iterate through ears, slicing them one by one
+    while (ear->prev != ear->next) {
+        iterations++;
+        prev = ear->prev;
+        next = ear->next;
+
+        if (hashing ? isEarHashed(ear) : isEar(ear)) {
+            // cut off the triangle
+            indices.emplace_back(prev->i);
+            indices.emplace_back(ear->i);
+            indices.emplace_back(next->i);
+
+            removeNode(ear);
+
+            // skipping the next vertice leads to less sliver triangles
+            ear = next->next;
+            stop = next->next;
+
+            continue;
+        }
+
+        ear = next;
+
+        // if we looped through the whole remaining polygon and can't find any more ears
+        if (ear == stop) {
+            // try filtering points and slicing again
+            if (!pass) earcutLinked(filterPoints(ear), 1);
+
+            // if this didn't work, try curing all small self-intersections locally
+            else if (pass == 1) {
+                ear = cureLocalIntersections(ear);
+                earcutLinked(ear, 2);
+
+            // as a last resort, try splitting the remaining polygon into two
+            } else if (pass == 2) splitEarcut(ear);
+
+            break;
+        }
+    }
+}
+
+// check whether a polygon node forms a valid ear with adjacent nodes
+template <typename N>
+bool Earcut<N>::isEar(Node* ear) {
+    const Node* a = ear->prev;
+    const Node* b = ear;
+    const Node* c = ear->next;
+
+    if (area(a, b, c) >= 0) return false; // reflex, can't be an ear
+
+    // now make sure we don't have other points inside the potential ear
+    Node* p = ear->next->next;
+
+    while (p != ear->prev) {
+        if (pointInTriangle(a->x, a->y, b->x, b->y, c->x, c->y, p->x, p->y) &&
+            area(p->prev, p, p->next) >= 0) return false;
+        p = p->next;
+    }
+
+    return true;
+}
+
+template <typename N>
+bool Earcut<N>::isEarHashed(Node* ear) {
+    const Node* a = ear->prev;
+    const Node* b = ear;
+    const Node* c = ear->next;
+
+    if (area(a, b, c) >= 0) return false; // reflex, can't be an ear
+
+    // triangle bbox; min & max are calculated like this for speed
+    const double minTX = std::min<double>(a->x, std::min<double>(b->x, c->x));
+    const double minTY = std::min<double>(a->y, std::min<double>(b->y, c->y));
+    const double maxTX = std::max<double>(a->x, std::max<double>(b->x, c->x));
+    const double maxTY = std::max<double>(a->y, std::max<double>(b->y, c->y));
+
+    // z-order range for the current triangle bbox;
+    const int32_t minZ = zOrder(minTX, minTY);
+    const int32_t maxZ = zOrder(maxTX, maxTY);
+
+    // first look for points inside the triangle in increasing z-order
+    Node* p = ear->nextZ;
+
+    while (p && p->z <= maxZ) {
+        if (p != ear->prev && p != ear->next &&
+            pointInTriangle(a->x, a->y, b->x, b->y, c->x, c->y, p->x, p->y) &&
+            area(p->prev, p, p->next) >= 0) return false;
+        p = p->nextZ;
+    }
+
+    // then look for points in decreasing z-order
+    p = ear->prevZ;
+
+    while (p && p->z >= minZ) {
+        if (p != ear->prev && p != ear->next &&
+            pointInTriangle(a->x, a->y, b->x, b->y, c->x, c->y, p->x, p->y) &&
+            area(p->prev, p, p->next) >= 0) return false;
+        p = p->prevZ;
+    }
+
+    return true;
+}
+
+// go through all polygon nodes and cure small local self-intersections
+template <typename N>
+typename Earcut<N>::Node*
+Earcut<N>::cureLocalIntersections(Node* start) {
+    Node* p = start;
+    do {
+        Node* a = p->prev;
+        Node* b = p->next->next;
+
+        // a self-intersection where edge (v[i-1],v[i]) intersects (v[i+1],v[i+2])
+        if (!equals(a, b) && intersects(a, p, p->next, b) && locallyInside(a, b) && locallyInside(b, a)) {
+            indices.emplace_back(a->i);
+            indices.emplace_back(p->i);
+            indices.emplace_back(b->i);
+
+            // remove two nodes involved
+            removeNode(p);
+            removeNode(p->next);
+
+            p = start = b;
+        }
+        p = p->next;
+    } while (p != start);
+
+    return p;
+}
+
+// try splitting polygon into two and triangulate them independently
+template <typename N>
+void Earcut<N>::splitEarcut(Node* start) {
+    // look for a valid diagonal that divides the polygon into two
+    Node* a = start;
+    do {
+        Node* b = a->next->next;
+        while (b != a->prev) {
+            if (a->i != b->i && isValidDiagonal(a, b)) {
+                // split the polygon in two by the diagonal
+                Node* c = splitPolygon(a, b);
+
+                // filter colinear points around the cuts
+                a = filterPoints(a, a->next);
+                c = filterPoints(c, c->next);
+
+                // run earcut on each half
+                earcutLinked(a);
+                earcutLinked(c);
+                return;
+            }
+            b = b->next;
+        }
+        a = a->next;
+    } while (a != start);
+}
+
+// link every hole into the outer loop, producing a single-ring polygon without holes
+template <typename N> template <typename Polygon>
+typename Earcut<N>::Node*
+Earcut<N>::eliminateHoles(const Polygon& points, Node* outerNode) {
+    const size_t len = points.size();
+
+    std::vector<Node*> queue;
+    for (size_t i = 1; i < len; i++) {
+        Node* list = linkedList(points[i], false);
+        if (list) {
+            if (list == list->next) list->steiner = true;
+            queue.push_back(getLeftmost(list));
+        }
+    }
+    std::sort(queue.begin(), queue.end(), [](const Node* a, const Node* b) {
+        return a->x < b->x;
+    });
+
+    // process holes from left to right
+    for (size_t i = 0; i < queue.size(); i++) {
+        eliminateHole(queue[i], outerNode);
+        outerNode = filterPoints(outerNode, outerNode->next);
+    }
+
+    return outerNode;
+}
+
+// find a bridge between vertices that connects hole with an outer ring and and link it
+template <typename N>
+void Earcut<N>::eliminateHole(Node* hole, Node* outerNode) {
+    outerNode = findHoleBridge(hole, outerNode);
+    if (outerNode) {
+        Node* b = splitPolygon(outerNode, hole);
+        filterPoints(b, b->next);
+    }
+}
+
+// David Eberly's algorithm for finding a bridge between hole and outer polygon
+template <typename N>
+typename Earcut<N>::Node*
+Earcut<N>::findHoleBridge(Node* hole, Node* outerNode) {
+    Node* p = outerNode;
+    double hx = hole->x;
+    double hy = hole->y;
+    double qx = -std::numeric_limits<double>::infinity();
+    Node* m = nullptr;
+
+    // find a segment intersected by a ray from the hole's leftmost Vertex to the left;
+    // segment's endpoint with lesser x will be potential connection Vertex
+    do {
+        if (hy <= p->y && hy >= p->next->y && p->next->y != p->y) {
+          double x = p->x + (hy - p->y) * (p->next->x - p->x) / (p->next->y - p->y);
+          if (x <= hx && x > qx) {
+            qx = x;
+            if (x == hx) {
+                if (hy == p->y) return p;
+                if (hy == p->next->y) return p->next;
+            }
+            m = p->x < p->next->x ? p : p->next;
+          }
+        }
+        p = p->next;
+    } while (p != outerNode);
+
+    if (!m) return 0;
+
+    if (hx == qx) return m->prev;
+
+    // look for points inside the triangle of hole Vertex, segment intersection and endpoint;
+    // if there are no points found, we have a valid connection;
+    // otherwise choose the Vertex of the minimum angle with the ray as connection Vertex
+
+    const Node* stop = m;
+    double tanMin = std::numeric_limits<double>::infinity();
+    double tanCur = 0;
+
+    p = m->next;
+    double mx = m->x;
+    double my = m->y;
+
+    while (p != stop) {
+        if (hx >= p->x && p->x >= mx && hx != p->x &&
+            pointInTriangle(hy < my ? hx : qx, hy, mx, my, hy < my ? qx : hx, hy, p->x, p->y)) {
+
+            tanCur = std::abs(hy - p->y) / (hx - p->x); // tangential
+
+            if ((tanCur < tanMin || (tanCur == tanMin && p->x > m->x)) && locallyInside(p, hole)) {
+                m = p;
+                tanMin = tanCur;
+            }
+        }
+
+        p = p->next;
+    }
+
+    return m;
+}
+
+// interlink polygon nodes in z-order
+template <typename N>
+void Earcut<N>::indexCurve(Node* start) {
+    assert(start);
+    Node* p = start;
+
+    do {
+        p->z = p->z ? p->z : zOrder(p->x, p->y);
+        p->prevZ = p->prev;
+        p->nextZ = p->next;
+        p = p->next;
+    } while (p != start);
+
+    p->prevZ->nextZ = nullptr;
+    p->prevZ = nullptr;
+
+    sortLinked(p);
+}
+
+// Simon Tatham's linked list merge sort algorithm
+// http://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.html
+template <typename N>
+typename Earcut<N>::Node*
+Earcut<N>::sortLinked(Node* list) {
+    assert(list);
+    Node* p;
+    Node* q;
+    Node* e;
+    Node* tail;
+    int i, numMerges, pSize, qSize;
+    int inSize = 1;
+
+    for (;;) {
+        p = list;
+        list = nullptr;
+        tail = nullptr;
+        numMerges = 0;
+
+        while (p) {
+            numMerges++;
+            q = p;
+            pSize = 0;
+            for (i = 0; i < inSize; i++) {
+                pSize++;
+                q = q->nextZ;
+                if (!q) break;
+            }
+
+            qSize = inSize;
+
+            while (pSize > 0 || (qSize > 0 && q)) {
+
+                if (pSize == 0) {
+                    e = q;
+                    q = q->nextZ;
+                    qSize--;
+                } else if (qSize == 0 || !q) {
+                    e = p;
+                    p = p->nextZ;
+                    pSize--;
+                } else if (p->z <= q->z) {
+                    e = p;
+                    p = p->nextZ;
+                    pSize--;
+                } else {
+                    e = q;
+                    q = q->nextZ;
+                    qSize--;
+                }
+
+                if (tail) tail->nextZ = e;
+                else list = e;
+
+                e->prevZ = tail;
+                tail = e;
+            }
+
+            p = q;
+        }
+
+        tail->nextZ = nullptr;
+
+        if (numMerges <= 1) return list;
+
+        inSize *= 2;
+    }
+}
+
+// z-order of a Vertex given coords and size of the data bounding box
+template <typename N>
+int32_t Earcut<N>::zOrder(const double x_, const double y_) {
+    // coords are transformed into non-negative 15-bit integer range
+    int32_t x = static_cast<int32_t>(32767.0 * (x_ - minX) * inv_size);
+    int32_t y = static_cast<int32_t>(32767.0 * (y_ - minY) * inv_size);
+
+    x = (x | (x << 8)) & 0x00FF00FF;
+    x = (x | (x << 4)) & 0x0F0F0F0F;
+    x = (x | (x << 2)) & 0x33333333;
+    x = (x | (x << 1)) & 0x55555555;
+
+    y = (y | (y << 8)) & 0x00FF00FF;
+    y = (y | (y << 4)) & 0x0F0F0F0F;
+    y = (y | (y << 2)) & 0x33333333;
+    y = (y | (y << 1)) & 0x55555555;
+
+    return x | (y << 1);
+}
+
+// find the leftmost node of a polygon ring
+template <typename N>
+typename Earcut<N>::Node*
+Earcut<N>::getLeftmost(Node* start) {
+    Node* p = start;
+    Node* leftmost = start;
+    do {
+        if (p->x < leftmost->x) leftmost = p;
+        p = p->next;
+    } while (p != start);
+
+    return leftmost;
+}
+
+// check if a point lies within a convex triangle
+template <typename N>
+bool Earcut<N>::pointInTriangle(double ax, double ay, double bx, double by, double cx, double cy, double px, double py) const {
+    return (cx - px) * (ay - py) - (ax - px) * (cy - py) >= 0 &&
+           (ax - px) * (by - py) - (bx - px) * (ay - py) >= 0 &&
+           (bx - px) * (cy - py) - (cx - px) * (by - py) >= 0;
+}
+
+// check if a diagonal between two polygon nodes is valid (lies in polygon interior)
+template <typename N>
+bool Earcut<N>::isValidDiagonal(Node* a, Node* b) {
+    return a->next->i != b->i && a->prev->i != b->i && !intersectsPolygon(a, b) &&
+           locallyInside(a, b) && locallyInside(b, a) && middleInside(a, b);
+}
+
+// signed area of a triangle
+template <typename N>
+double Earcut<N>::area(const Node* p, const Node* q, const Node* r) const {
+    return (q->y - p->y) * (r->x - q->x) - (q->x - p->x) * (r->y - q->y);
+}
+
+// check if two points are equal
+template <typename N>
+bool Earcut<N>::equals(const Node* p1, const Node* p2) {
+    return p1->x == p2->x && p1->y == p2->y;
+}
+
+// check if two segments intersect
+template <typename N>
+bool Earcut<N>::intersects(const Node* p1, const Node* q1, const Node* p2, const Node* q2) {
+    if ((equals(p1, q1) && equals(p2, q2)) ||
+        (equals(p1, q2) && equals(p2, q1))) return true;
+    return (area(p1, q1, p2) > 0) != (area(p1, q1, q2) > 0) &&
+           (area(p2, q2, p1) > 0) != (area(p2, q2, q1) > 0);
+}
+
+// check if a polygon diagonal intersects any polygon segments
+template <typename N>
+bool Earcut<N>::intersectsPolygon(const Node* a, const Node* b) {
+    const Node* p = a;
+    do {
+        if (p->i != a->i && p->next->i != a->i && p->i != b->i && p->next->i != b->i &&
+                intersects(p, p->next, a, b)) return true;
+        p = p->next;
+    } while (p != a);
+
+    return false;
+}
+
+// check if a polygon diagonal is locally inside the polygon
+template <typename N>
+bool Earcut<N>::locallyInside(const Node* a, const Node* b) {
+    return area(a->prev, a, a->next) < 0 ?
+        area(a, b, a->next) >= 0 && area(a, a->prev, b) >= 0 :
+        area(a, b, a->prev) < 0 || area(a, a->next, b) < 0;
+}
+
+// check if the middle Vertex of a polygon diagonal is inside the polygon
+template <typename N>
+bool Earcut<N>::middleInside(const Node* a, const Node* b) {
+    const Node* p = a;
+    bool inside = false;
+    double px = (a->x + b->x) / 2;
+    double py = (a->y + b->y) / 2;
+    do {
+        if (((p->y > py) != (p->next->y > py)) && p->next->y != p->y &&
+                (px < (p->next->x - p->x) * (py - p->y) / (p->next->y - p->y) + p->x))
+            inside = !inside;
+        p = p->next;
+    } while (p != a);
+
+    return inside;
+}
+
+// link two polygon vertices with a bridge; if the vertices belong to the same ring, it splits
+// polygon into two; if one belongs to the outer ring and another to a hole, it merges it into a
+// single ring
+template <typename N>
+typename Earcut<N>::Node*
+Earcut<N>::splitPolygon(Node* a, Node* b) {
+    Node* a2 = nodes.construct(a->i, a->x, a->y);
+    Node* b2 = nodes.construct(b->i, b->x, b->y);
+    Node* an = a->next;
+    Node* bp = b->prev;
+
+    a->next = b;
+    b->prev = a;
+
+    a2->next = an;
+    an->prev = a2;
+
+    b2->next = a2;
+    a2->prev = b2;
+
+    bp->next = b2;
+    b2->prev = bp;
+
+    return b2;
+}
+
+// create a node and util::optionally link it with previous one (in a circular doubly linked list)
+template <typename N> template <typename Point>
+typename Earcut<N>::Node*
+Earcut<N>::insertNode(std::size_t i, const Point& pt, Node* last) {
+    Node* p = nodes.construct(static_cast<N>(i), util::nth<0, Point>::get(pt), util::nth<1, Point>::get(pt));
+
+    if (!last) {
+        p->prev = p;
+        p->next = p;
+
+    } else {
+        assert(last);
+        p->next = last->next;
+        p->prev = last;
+        last->next->prev = p;
+        last->next = p;
+    }
+    return p;
+}
+
+template <typename N>
+void Earcut<N>::removeNode(Node* p) {
+    p->next->prev = p->prev;
+    p->prev->next = p->next;
+
+    if (p->prevZ) p->prevZ->nextZ = p->nextZ;
+    if (p->nextZ) p->nextZ->prevZ = p->prevZ;
+}
+}
+
+template <typename N = uint32_t, typename Polygon>
+std::vector<N> earcut(const Polygon& poly) {
+    mapbox::detail::Earcut<N> earcut;
+    earcut(poly);
+    return std::move(earcut.indices);
+}
+}