8 files changed, 895 insertions, 23 deletions

diff --git a/src/3rdparty/earcut/LICENSE b/src/3rdparty/earcut/LICENSE
new file mode 100644
index 00000000..8bafb577
--- /dev/null
+++ b/src/3rdparty/earcut/LICENSE
@@ -0,0 +1,15 @@
+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.
diff --git a/src/3rdparty/earcut/earcut.hpp b/src/3rdparty/earcut/earcut.hpp
new file mode 100644
index 00000000..1f14b9f7
--- /dev/null
+++ b/src/3rdparty/earcut/earcut.hpp
@@ -0,0 +1,773 @@
+#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;
+    N 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(N i, const Point& p, Node* last);
+    void removeNode(Node* p);
+
+    bool hashing;
+    double minX, maxX;
+    double minY, maxY;
+    double size;
+
+    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;
+    size = 0;
+    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 = p->x;
+        minY = maxY = p->y;
+        do {
+            x = p->x;
+            y = p->y;
+            minX = (std::min)(minX, x);
+            minY = (std::min)(minY, y);
+            maxX = (std::max)(maxX, x);
+            maxY = (std::max)(maxY, y);
+            p = p->next;
+        } while (p != outerNode);
+
+        // minX, minY and size are later used to transform coords into integers for z-order calculation
+        size = (std::max)(maxX - minX, maxY - minY);
+    }
+
+    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 int len = static_cast<int>(points.size());
+    int i, j;
+    Point p1, p2;
+    Node* last = nullptr;
+
+    // calculate original winding order of a polygon ring
+    for (i = 0, j = len - 1; i < len; j = i++) {
+        p1 = points[i];
+        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 - 1; i >= 0; i--) 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) return nullptr;
+            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)(a->x, (std::min)(b->x, c->x));
+    const double minTY = (std::min)(a->y, (std::min)(b->y, c->y));
+    const double maxTX = (std::max)(a->x, (std::max)(b->x, c->x));
+    const double maxTY = (std::max)(a->y, (std::max)(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;
+
+    while (true) {
+        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) / size);
+    int32_t y = static_cast<int32_t>(32767.0 * (y_ - minY) / 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(N i, const Point& pt, Node* last) {
+    Node* p = nodes.construct(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 earcut.indices;
+}
+}
diff --git a/src/3rdparty/earcut/qt_attribution.json b/src/3rdparty/earcut/qt_attribution.json
new file mode 100644
index 00000000..0e52989c
--- /dev/null
+++ b/src/3rdparty/earcut/qt_attribution.json
@@ -0,0 +1,13 @@
+{
+    "Id": "earcut",
+    "Name": "Earcut Polygon Triangulation Library",
+    "QDocModule": "qtlocation",
+    "QtUsage": "Used in the QML plugin of Qt Location.",
+
+    "Description": "A C++ port of earcut.js, a fast, header-only polygon triangulation library.",
+    "Homepage": "https://github.com/mapbox/earcut.hpp",
+    "LicenseId": "ISC",
+    "License": "ISC License",
+    "LicenseFile": "LICENSE",
+    "Copyright": "Copyright (c) 2015 Mapbox"
+}
diff --git a/src/location/declarativemaps/qdeclarativepolygonmapitem.cpp b/src/location/declarativemaps/qdeclarativepolygonmapitem.cpp
index daa1a9fc..3218f9f1 100644
--- a/src/location/declarativemaps/qdeclarativepolygonmapitem.cpp
+++ b/src/location/declarativemaps/qdeclarativepolygonmapitem.cpp
@@ -53,6 +53,8 @@
 
 /* poly2tri triangulator includes */
 #include <clip2tri.h>
+#include <earcut.hpp>
+#include <array>
 
 QT_BEGIN_NAMESPACE
 
@@ -185,7 +187,7 @@ void QGeoMapPolygonGeometry::updateSourcePoints(const QGeoMap &map,
 
     // 2)
     QList<QList<QDoubleVector2D> > clippedPaths;
-    const QList<QDoubleVector2D> &visibleRegion = map.geoProjection().visibleRegion();
+    const QList<QDoubleVector2D> &visibleRegion = map.geoProjection().projectableRegion();
     if (visibleRegion.size()) {
         c2t::clip2tri clipper;
         clipper.addSubjectPath(QClipperUtils::qListToPath(wrappedPath), true);
@@ -306,23 +308,42 @@ void QGeoMapPolygonGeometry::updateScreenPoints(const QGeoMap &map)
 
     screenOutline_ = ppi;
 
-    QTriangleSet ts = qTriangulate(ppi);
-    qreal *vx = ts.vertices.data();
-
-    screenIndices_.reserve(ts.indices.size());
-    screenVertices_.reserve(ts.vertices.size());
+    using Coord = double;
+    using N = uint32_t;
+    using Point = std::array<Coord, 2>;
+
+    std::vector<std::vector<Point>> polygon;
+    polygon.push_back(std::vector<Point>());
+    std::vector<Point> &poly = polygon.front();
+    // ... fill polygon structure with actual data
+
+    for (int i = 0; i < ppi.elementCount(); ++i) {
+        const QPainterPath::Element e = ppi.elementAt(i);
+        if (e.isMoveTo() || i == ppi.elementCount() - 1
+                || (qAbs(e.x - poly.front()[0]) < 0.1
+                    && qAbs(e.y - poly.front()[1]) < 0.1)) {
+            Point p = { e.x, e.y };
+            poly.push_back( p );
+        } else if (e.isLineTo()) {
+            Point p = { e.x, e.y };
+            poly.push_back( p );
+        } else {
+            qWarning("Unhandled element type in polygon painterpath");
+        }
+    }
 
-    if (ts.indices.type() == QVertexIndexVector::UnsignedInt) {
-        const quint32 *ix = reinterpret_cast<const quint32 *>(ts.indices.data());
-        for (int i = 0; i < (ts.indices.size()/3*3); ++i)
-            screenIndices_ << ix[i];
-    } else {
-        const quint16 *ix = reinterpret_cast<const quint16 *>(ts.indices.data());
-        for (int i = 0; i < (ts.indices.size()/3*3); ++i)
-            screenIndices_ << ix[i];
+    if (poly.size() > 2) {
+        // Run tessellation
+        // Returns array of indices that refer to the vertices of the input polygon.
+        // Three subsequent indices form a triangle.
+        screenVertices_.clear();
+        screenIndices_.clear();
+        for (const auto &p : poly)
+            screenVertices_ << QPointF(p[0], p[1]);
+        std::vector<N> indices = mapbox::earcut<N>(polygon);
+        for (const auto &i: indices)
+            screenIndices_ << quint32(i);
     }
-    for (int i = 0; i < (ts.vertices.size()/2*2); i += 2)
-        screenVertices_ << QPointF(vx[i], vx[i + 1]);
 
     screenBounds_ = ppi.boundingRect();
 }
diff --git a/src/location/declarativemaps/qdeclarativepolylinemapitem.cpp b/src/location/declarativemaps/qdeclarativepolylinemapitem.cpp
index aedb9811..26f030b0 100644
--- a/src/location/declarativemaps/qdeclarativepolylinemapitem.cpp
+++ b/src/location/declarativemaps/qdeclarativepolylinemapitem.cpp
@@ -226,7 +226,7 @@ QList<QList<QDoubleVector2D> > QGeoMapPolylineGeometry::clipPath(const QGeoMap &
 
     // 2)
     QList<QList<QDoubleVector2D> > clippedPaths;
-    const QList<QDoubleVector2D> &visibleRegion = map.geoProjection().visibleRegion();
+    const QList<QDoubleVector2D> &visibleRegion = map.geoProjection().projectableRegion();
     if (visibleRegion.size()) {
         c2t::clip2tri clipper;
         clipper.addSubjectPath(QClipperUtils::qListToPath(wrappedPath), false);
diff --git a/src/location/location.pro b/src/location/location.pro
index 5dc89a63..a951ebd6 100644
--- a/src/location/location.pro
+++ b/src/location/location.pro
@@ -10,6 +10,7 @@ CONFIG += simd optimize_full
 # 3rdparty headers produce warnings with MSVC
 msvc: CONFIG -= warning_clean
 
+INCLUDEPATH += ../3rdparty/earcut
 INCLUDEPATH += ../3rdparty/poly2tri
 INCLUDEPATH += ../3rdparty/clipper
 INCLUDEPATH += ../3rdparty/clip2tri
diff --git a/src/location/maps/qgeoprojection.cpp b/src/location/maps/qgeoprojection.cpp
index 07747a31..609fb934 100644
--- a/src/location/maps/qgeoprojection.cpp
+++ b/src/location/maps/qgeoprojection.cpp
@@ -317,6 +317,13 @@ QList<QDoubleVector2D> QGeoProjectionWebMercator::visibleRegion() const
     return m_visibleRegion;
 }
 
+QList<QDoubleVector2D> QGeoProjectionWebMercator::projectableRegion() const
+{
+    if (m_visibleRegionDirty)
+        const_cast<QGeoProjectionWebMercator *>(this)->updateVisibleRegion();
+    return m_projectableRegion;
+}
+
 QDoubleVector2D QGeoProjectionWebMercator::viewportToWrappedMapProjection(const QDoubleVector2D &itemPosition) const
 {
     double s;
@@ -350,6 +357,8 @@ void QGeoProjectionWebMercator::setupCamera()
     int intZoomLevel = static_cast<int>(std::floor(m_cameraData.zoomLevel()));
     m_sideLength = (1 << intZoomLevel) * defaultTileSize;
     m_center = m_centerMercator * m_sideLength;
+    //aperture(90 / 2) = 1
+    m_aperture = tan(QLocationUtils::radians(m_cameraData.fieldOfView()) * 0.5);
 
     double f = m_viewportHeight;
     double z = std::pow(2.0, m_cameraData.zoomLevel() - intZoomLevel) * defaultTileSize;
@@ -358,15 +367,13 @@ void QGeoProjectionWebMercator::setupCamera()
     double z_mercator = std::pow(2.0, m_cameraData.zoomLevel()) * defaultTileSize;
     double altitude_mercator = f / (2.0 * z_mercator);
 
-    //aperture(90 / 2) = 1
-    m_aperture = tan(QLocationUtils::radians(m_cameraData.fieldOfView()) * 0.5);
     // calculate eye
     m_eye = m_center;
     m_eye.setZ(altitude * defaultTileSize / m_aperture);
 
     // And in mercator space
     m_eyeMercator = m_centerMercator;
-    m_eyeMercator.setZ(altitude_mercator);
+    m_eyeMercator.setZ(altitude_mercator  / m_aperture);
 
     m_view = m_eye - m_center;
     QDoubleVector3D side = QDoubleVector3D::normal(m_view, QDoubleVector3D(0.0, 1.0, 0.0));
@@ -402,7 +409,7 @@ void QGeoProjectionWebMercator::setupCamera()
         m_eyeMercator = mTiltMercator * m_viewMercator + m_centerMercator;
     }
 
-    m_view = m_eye - m_center;
+    m_view = m_eye - m_center; // ToDo: this should be inverted (center - eye), and the rest should follow
     m_viewNormalized = m_view.normalized();
     m_up = QDoubleVector3D::normal(m_view, m_side);
 
@@ -455,7 +462,7 @@ void QGeoProjectionWebMercator::setupCamera()
     m_transformation.scale(m_sideLength, m_sideLength, 1.0);
 
     m_centerNearPlane = m_eye + m_viewNormalized;
-    m_centerNearPlaneMercator = m_eyeMercator + m_viewNormalized * m_nearPlaneMercator;
+    m_centerNearPlaneMercator = m_eyeMercator - m_viewNormalized * m_nearPlaneMercator;
 
     // The method does not support tilting angles >= 90.0 or < 0.
 
@@ -505,6 +512,46 @@ void QGeoProjectionWebMercator::updateVisibleRegion()
     m_visibleRegion.clear();
     if (res.size())
         m_visibleRegion = QClipperUtils::pathToQList(res[0]); // Intersection between two convex quadrilaterals should always be a single polygon
+
+    m_projectableRegion.clear();
+    if (m_cameraData.tilt() == 0) {
+        m_projectableRegion = mapRect;
+    } else {
+        QGeoProjectionWebMercator::Plane nearPlane(m_centerNearPlaneMercator, m_viewNormalized);
+        Line2D nearPlaneXYIntersection = nearPlane.planeXYIntersection();
+        double squareHalfSide = qMax(5.0, nearPlaneXYIntersection.m_point.length());
+        QDoubleVector2D viewDirectionProjected = -m_viewNormalized.toVector2D().normalized();
+
+
+        QDoubleVector2D tl = nearPlaneXYIntersection.m_point
+                            - squareHalfSide * nearPlaneXYIntersection.m_direction
+                            + 2 * squareHalfSide * viewDirectionProjected;
+        QDoubleVector2D tr = nearPlaneXYIntersection.m_point
+                            + squareHalfSide * nearPlaneXYIntersection.m_direction
+                            + 2 * squareHalfSide * viewDirectionProjected;
+        QDoubleVector2D bl = nearPlaneXYIntersection.m_point
+                            - squareHalfSide * nearPlaneXYIntersection.m_direction;
+        QDoubleVector2D br = nearPlaneXYIntersection.m_point
+                            + squareHalfSide * nearPlaneXYIntersection.m_direction;
+
+        QList<QDoubleVector2D> projectableRect;
+        projectableRect.push_back(bl);
+        projectableRect.push_back(br);
+        projectableRect.push_back(tr);
+        projectableRect.push_back(tl);
+
+
+        c2t::clip2tri clipperProjectable;
+        clipperProjectable.clearClipper();
+        clipperProjectable.addSubjectPath(QClipperUtils::qListToPath(mapRect), true);
+        clipperProjectable.addClipPolygon(QClipperUtils::qListToPath(projectableRect));
+
+        Paths resProjectable = clipperProjectable.execute(c2t::clip2tri::Intersection);
+        if (resProjectable.size())
+            m_projectableRegion = QClipperUtils::pathToQList(resProjectable[0]); // Intersection between two convex quadrilaterals should always be a single polygon
+        else
+            m_projectableRegion = viewportRect;
+    }
 }
 
 /*
diff --git a/src/location/maps/qgeoprojection_p.h b/src/location/maps/qgeoprojection_p.h
index 7d306eea..76e11af0 100644
--- a/src/location/maps/qgeoprojection_p.h
+++ b/src/location/maps/qgeoprojection_p.h
@@ -73,6 +73,7 @@ public:
 
     virtual bool isProjectable(const QDoubleVector2D &wrappedProjection) const = 0;
     virtual QList<QDoubleVector2D> visibleRegion() const = 0;
+    virtual QList<QDoubleVector2D> projectableRegion() const = 0;
 
     // Conversion methods for QGeoCoordinate <-> screen.
     // This currently assumes that the "MapProjection" space is [0, 1][0, 1] for every type of possibly supported map projection
@@ -126,7 +127,7 @@ public:
 
     bool isProjectable(const QDoubleVector2D &wrappedProjection) const Q_DECL_OVERRIDE;
     QList<QDoubleVector2D> visibleRegion() const Q_DECL_OVERRIDE;
-
+    QList<QDoubleVector2D> projectableRegion() const Q_DECL_OVERRIDE;
     inline QDoubleVector2D viewportToWrappedMapProjection(const QDoubleVector2D &itemPosition) const;
     inline QDoubleVector2D viewportToWrappedMapProjection(const QDoubleVector2D &itemPosition, double &s) const;
 private:
@@ -202,6 +203,7 @@ private:
     Line2D           m_nearPlaneMapIntersection;
 
     QList<QDoubleVector2D> m_visibleRegion;
+    QList<QDoubleVector2D> m_projectableRegion;
     bool             m_visibleRegionDirty;
 
     Q_DISABLE_COPY(QGeoProjectionWebMercator)