Fix a ton of robustness issues (parity with earcut v2.2.0) (#76)

* fix a ton of robustness issues

* add a missing dep to hopefully fix travis

* upgrade to clang-6

* xenial

* update readme [skip ci]

.travis.yml

@@ -56,14 +56,13 @@ matrix:
         - BUILDTYPE=Debug
         - MATRIX_EVAL="CC=clang-5.0 && CXX=clang++-5.0"
       compiler: clang
+      dist: xenial
       addons:
         apt:
-          sources:
-            - llvm-toolchain-trusty-5.0
           packages:
             - *shared_linux_packages
             - clang-5.0
-    
+
     # clang3.8 release
     - os: linux
       env:
@@ -115,10 +114,9 @@ matrix:
       osx_image: xcode8
       env: BUILDTYPE=Release
       compiler: gcc
-    
+
     # osx clang
     - os: osx
       osx_image: xcode8
       env: BUILDTYPE=Release
       compiler: clang
-

README.md

@@ -128,4 +128,4 @@ Import the project from https://github.com/mapbox/earcut.hpp.git and you should
 
 ## Status
 
-This is currently based on [earcut 2.1.5](https://github.com/mapbox/earcut#215-feb-5-2019).
+This is currently based on [earcut 2.2.0](https://github.com/mapbox/earcut#220-sep-18-2019).

include/mapbox/earcut.hpp

@@ -65,6 +65,7 @@ class Earcut {
     template <typename Polygon> Node* eliminateHoles(const Polygon& points, Node* outerNode);
     void eliminateHole(Node* hole, Node* outerNode);
     Node* findHoleBridge(Node* hole, Node* outerNode);
+    bool sectorContainsSector(const Node* m, const Node* p);
     void indexCurve(Node* start);
     Node* sortLinked(Node* list);
     int32_t zOrder(const double x_, const double y_);
@@ -74,6 +75,8 @@ class Earcut {
     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 onSegment(const Node* p, const Node* q, const Node* r);
+    int sign(double val);
     bool intersectsPolygon(const Node* a, const Node* b);
     bool locallyInside(const Node* a, const Node* b);
     bool middleInside(const Node* a, const Node* b);
@@ -289,7 +292,7 @@ void Earcut<N>::earcutLinked(Node* ear, int pass) {
 
             // if this didn't work, try curing all small self-intersections locally
             else if (pass == 1) {
-                ear = cureLocalIntersections(ear);
+                ear = cureLocalIntersections(filterPoints(ear));
                 earcutLinked(ear, 2);
 
             // as a last resort, try splitting the remaining polygon into two
@@ -386,7 +389,7 @@ Earcut<N>::cureLocalIntersections(Node* start) {
         p = p->next;
     } while (p != start);
 
-    return p;
+    return filterPoints(p);
 }
 
 // try splitting polygon into two and triangulate them independently
@@ -482,7 +485,7 @@ Earcut<N>::findHoleBridge(Node* hole, Node* outerNode) {
 
     if (!m) return 0;
 
-    if (hx == qx) return m->prev;
+    if (hx == qx) return m; // hole touches outer segment; pick leftmost endpoint
 
     // look for points inside the triangle of hole Vertex, segment intersection and endpoint;
     // if there are no points found, we have a valid connection;
@@ -492,28 +495,38 @@ Earcut<N>::findHoleBridge(Node* hole, Node* outerNode) {
     double tanMin = std::numeric_limits<double>::infinity();
     double tanCur = 0;
 
-    p = m->next;
+    p = m;
     double mx = m->x;
     double my = m->y;
 
-    while (p != stop) {
+    do {
         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)) {
+            if (locallyInside(p, hole) &&
+                (tanCur < tanMin || (tanCur == tanMin && (p->x > m->x || sectorContainsSector(m, p))))) {
                 m = p;
                 tanMin = tanCur;
             }
         }
 
         p = p->next;
-    }
+    } while (p != stop);
 
     return m;
 }
 
+// whether sector in vertex m contains sector in vertex p in the same coordinates
+template <typename N>
+bool Earcut<N>::sectorContainsSector(const Node* m, const Node* p) {
+    return (
+        (area(m->prev, m, p->prev) < 0 || area(p->prev, m, m->next) < 0) &&
+        (area(m->prev, m, p->next) < 0 || area(p->next, m, m->next) < 0)
+    );
+}
+
 // interlink polygon nodes in z-order
 template <typename N>
 void Earcut<N>::indexCurve(Node* start) {
@@ -648,8 +661,10 @@ bool Earcut<N>::pointInTriangle(double ax, double ay, double bx, double by, doub
 // 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);
+    return a->next->i != b->i && a->prev->i != b->i && !intersectsPolygon(a, b) && // dones't intersect other edges
+           ((locallyInside(a, b) && locallyInside(b, a) && middleInside(a, b) && // locally visible
+            (area(a->prev, a, b->prev) != 0.0 || area(a, b->prev, b) != 0.0)) || // does not create opposite-facing sectors
+            (equals(a, b) && area(a->prev, a, a->next) > 0 && area(b->prev, b, b->next) > 0)); // special zero-length case
 }
 
 // signed area of a triangle
@@ -667,10 +682,33 @@ bool Earcut<N>::equals(const Node* p1, const Node* p2) {
 // 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);
+    int o1 = sign(area(p1, q1, p2));
+    int o2 = sign(area(p1, q1, q2));
+    int o3 = sign(area(p2, q2, p1));
+    int o4 = sign(area(p2, q2, q1));
+
+    if (o1 != o2 && o3 != o4) return true; // general case
+
+    if (o1 == 0 && onSegment(p1, p2, q1)) return true; // p1, q1 and p2 are collinear and p2 lies on p1q1
+    if (o2 == 0 && onSegment(p1, q2, q1)) return true; // p1, q1 and q2 are collinear and q2 lies on p1q1
+    if (o3 == 0 && onSegment(p2, p1, q2)) return true; // p2, q2 and p1 are collinear and p1 lies on p2q2
+    if (o4 == 0 && onSegment(p2, q1, q2)) return true; // p2, q2 and q1 are collinear and q1 lies on p2q2
+
+    return false;
+}
+
+// for collinear points p, q, r, check if point q lies on segment pr
+template <typename N>
+bool Earcut<N>::onSegment(const Node* p, const Node* q, const Node* r) {
+    return q->x <= std::max<double>(p->x, r->x) &&
+        q->x >= std::min<double>(p->x, r->x) &&
+        q->y <= std::max<double>(p->y, r->y) &&
+        q->y >= std::min<double>(p->y, r->y);
+}
+
+template <typename N>
+int Earcut<N>::sign(double val) {
+    return (0.0 < val) - (val < 0.0);
 }
 
 // check if a polygon diagonal intersects any polygon segments

test/convert_tests.js

@@ -59,7 +59,8 @@ fs.readdirSync(base).filter(function (name) {
         "issue45": 0.094,
         "empty_square": Infinity,
         "issue83": Infinity,
-        "issue107": Infinity
+        "issue107": Infinity,
+        "issue119": 0.04
     };
     var expectedLibtessDeviation = libtessDeviationMap[id];
     if (!expectedLibtessDeviation) expectedLibtessDeviation = 0.000001;

test/fixtures/boxy.cpp

@@ -0,0 +1,17 @@
+// This file is auto-generated, manual changes will be lost if the code is regenerated.
+
+#include "geometries.hpp"
+
+namespace mapbox {
+namespace fixtures {
+
+static const Fixture<short> boxy("boxy", 57, 1e-14, 0.000001, {
+    {{3432,2779},{3432,2794},{3450,2794},{3450,2825},{3413,2825},{3413,2856},{3395,2856},{3395,2871},{3377,2871},{3377,2856},{3359,2856},{3359,2840},{3341,2840},{3341,2871},{3322,2871},{3322,2887},{3249,2887},{3249,2871},{3268,2871},{3268,2840},{3304,2840},{3304,2825},{3322,2825},{3322,2810},{3304,2810},{3304,2794},{3322,2794},{3322,2779},{3341,2779},{3341,2733},{3359,2733},{3359,2687},{3395,2687},{3395,2702},{3432,2702},{3432,2717},{3450,2717},{3450,2733},{3486,2733},{3486,2748},{3468,2748},{3468,2763},{3450,2763},{3450,2779},{3432,2779}},
+    {{3359,2794},{3341,2794},{3341,2810},{3395,2810},{3395,2794},{3377,2794},{3377,2779},{3359,2779},{3359,2794}},
+    {{3432,2779},{3432,2748},{3413,2748},{3413,2779},{3432,2779}},
+    {{3377,2779},{3395,2779},{3395,2748},{3377,2748},{3377,2779}},
+    {{3377,2717},{3395,2717},{3395,2702},{3377,2702},{3377,2717}},
+});
+
+}
+}

test/fixtures/collinear_diagonal.cpp

@@ -0,0 +1,13 @@
+// This file is auto-generated, manual changes will be lost if the code is regenerated.
+
+#include "geometries.hpp"
+
+namespace mapbox {
+namespace fixtures {
+
+static const Fixture<short> collinear_diagonal("collinear_diagonal", 14, 1e-14, 0.000001, {
+    {{3468,1913},{3486,1884},{3413,1869},{3322,1869},{3413,1854},{3413,1869},{3486,1869},{3486,1884},{3504,1884},{3504,1869},{3432,1869},{3432,1854},{3395,1854},{3432,1839},{3432,1854},{3450,1839},{3341,1839},{3341,1825},{3195,1825},{3341,1810},{3341,1825},{3450,1825},{3523,1854},{3523,1913}},
+});
+
+}
+}

test/fixtures/hourglass.cpp

@@ -0,0 +1,13 @@
+// This file is auto-generated, manual changes will be lost if the code is regenerated.
+
+#include "geometries.hpp"
+
+namespace mapbox {
+namespace fixtures {
+
+static const Fixture<short> hourglass("hourglass", 2, 1e-14, 0.000001, {
+    {{7,18},{7,15},{5,15},{7,13},{7,15},{17,17}},
+});
+
+}
+}

test/fixtures/issue119.cpp

@@ -0,0 +1,17 @@
+// This file is auto-generated, manual changes will be lost if the code is regenerated.
+
+#include "geometries.hpp"
+
+namespace mapbox {
+namespace fixtures {
+
+static const Fixture<short> issue119("issue119", 18, 1e-14, 0.04, {
+    {{2,12},{2,20},{25,20},{25,12}},
+    {{7,18},{7,15},{5,15}},
+    {{19,18},{19,17},{17,17}},
+    {{19,17},{21,17},{19,16}},
+    {{7,15},{9,15},{7,13}},
+});
+
+}
+}

test/fixtures/touching2.cpp

@@ -0,0 +1,14 @@
+// This file is auto-generated, manual changes will be lost if the code is regenerated.
+
+#include "geometries.hpp"
+
+namespace mapbox {
+namespace fixtures {
+
+static const Fixture<short> touching2("touching2", 8, 1e-14, 0.000001, {
+    {{120,2031},{92,2368},{94,2200},{33,2119},{42,2112},{53,2068}},
+    {{44,2104},{79,2132},{88,2115},{44,2104}},
+});
+
+}
+}

test/fixtures/touching3.cpp

@@ -0,0 +1,15 @@
+// This file is auto-generated, manual changes will be lost if the code is regenerated.
+
+#include "geometries.hpp"
+
+namespace mapbox {
+namespace fixtures {
+
+static const Fixture<short> touching3("touching3", 15, 1e-14, 0.000001, {
+    {{1241,887},{1257,891},{1248,904},{1232,911},{1212,911},{1207,911},{1209,900},{1219,898},{1225,907},{1241,887}},
+    {{1212,902},{1212,911},{1219,909},{1212,902}},
+    {{1248,891},{1239,896},{1246,898},{1248,891}},
+});
+
+}
+}