Tessellator: stop copying vertices into Polys and Monotones.

src/gpu/GrTessellator.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrTessellator.h"
 
 #include "GrPathUtils.h"
@@ skipping 186 matching lines @@
 #endif
     return data;
 }
 
 struct EdgeList {
     EdgeList() : fHead(nullptr), fTail(nullptr) {}
     Edge* fHead;
     Edge* fTail;
 };
 
-struct VertexList {
-    VertexList() : fHead(nullptr), fTail(nullptr) {}
-    Vertex* fHead;
-    Vertex* fTail;
-    void insert(Vertex* v, Vertex* prev, Vertex* next) {
-        list_insert<Vertex, &Vertex::fPrev, &Vertex::fNext>(v, prev, next, &fHead, &fTail);
+template<class T> struct List {
+    List() : fHead(nullptr), fTail(nullptr) {}
+    T* fHead;
+    T* fTail;
+    void insert(T* t, T* prev, T* next) {
+        list_insert<T, &T::fPrev, &T::fNext>(t, prev, next, &fHead, &fTail);
     }
-    void append(Vertex* v) {
-        insert(v, fTail, nullptr);
+    void append(T* t) {
+        insert(t, fTail, nullptr);
     }
-    void prepend(Vertex* v) {
-        insert(v, nullptr, fHead);
+    void prepend(T* t) {
+        insert(t, nullptr, fHead);
+    }
+    void remove(T* t) {
+        list_remove<T, &T::fPrev, &T::fNext>(t, &fHead, &fTail);
     }
 };
 
+typedef List<Vertex> VertexList;
+
 /**
  * An Edge joins a top Vertex to a bottom Vertex. Edge ordering for the list of "edges above" and
  * "edge below" a vertex as well as for the active edge list is handled by isLeftOf()/isRightOf().
  * Note that an Edge will give occasionally dist() != 0 for its own endpoints (because floating
  * point). For speed, that case is only tested by the callers which require it (e.g.,
  * cleanup_active_edges()). Edges also handle checking for intersection with other edges.
  * Currently, this converts the edges to the parametric form, in order to avoid doing a division
  * until an intersection has been confirmed. This is slightly slower in the "found" case, but
  * a lot faster in the "not found" case.
  *
@@ skipping 10 matching lines @@
         : fWinding(winding)
         , fTop(top)
         , fBottom(bottom)
         , fLeft(nullptr)
         , fRight(nullptr)
         , fPrevEdgeAbove(nullptr)
         , fNextEdgeAbove(nullptr)
         , fPrevEdgeBelow(nullptr)
         , fNextEdgeBelow(nullptr)
         , fLeftPoly(nullptr)
-        , fRightPoly(nullptr) {
+        , fRightPoly(nullptr)
+        , fLeftPolyPrev(nullptr)
+        , fLeftPolyNext(nullptr)
+        , fRightPolyPrev(nullptr)
+        , fRightPolyNext(nullptr) {
             recompute();
         }
     int      fWinding;          // 1 == edge goes downward; -1 = edge goes upward.
     Vertex*  fTop;              // The top vertex in vertex-sort-order (sweep_lt).
     Vertex*  fBottom;           // The bottom vertex in vertex-sort-order.
     Edge*    fLeft;             // The linked list of edges in the active edge list.
     Edge*    fRight;            // "
     Edge*    fPrevEdgeAbove;    // The linked list of edges in the bottom Vertex's "edges above".
     Edge*    fNextEdgeAbove;    // "
     Edge*    fPrevEdgeBelow;    // The linked list of edges in the top Vertex's "edges below".
     Edge*    fNextEdgeBelow;    // "
     Poly*    fLeftPoly;         // The Poly to the left of this edge, if any.
     Poly*    fRightPoly;        // The Poly to the right of this edge, if any.
+    Edge*    fLeftPolyPrev;
+    Edge*    fLeftPolyNext;
+    Edge*    fRightPolyPrev;
+    Edge*    fRightPolyNext;
     double   fDX;               // The line equation for this edge, in implicit form.
     double   fDY;               // fDY * x + fDX * y + fC = 0, for point (x, y) on the line.
     double   fC;
     double dist(const SkPoint& p) const {
         return fDY * p.fX - fDX * p.fY + fC;
     }
     bool isRightOf(Vertex* v) const {
         return dist(v->fPoint) < 0.0;
     }
     bool isLeftOf(Vertex* v) const {
@@ skipping 33 matching lines @@
         return true;
     }
     bool isActive(EdgeList* activeEdges) const {
         return activeEdges && (fLeft || fRight || activeEdges->fHead == this);
     }
 };
 
 /***************************************************************************************/
 
 struct Poly {
-    Poly(int winding)
-        : fWinding(winding)
-        , fHead(nullptr)
-        , fTail(nullptr)
-        , fActive(nullptr)
+    Poly(Vertex* v, int winding)
+        : fFirstVertex(v)
+        , fWinding(winding)
         , fNext(nullptr)
         , fPartner(nullptr)
         , fCount(0)
     {
 #if LOGGING_ENABLED
         static int gID = 0;
         fID = gID++;
         LOG("*** created Poly %d\n", fID);
 #endif
     }
-    typedef enum { kNeither_Side, kLeft_Side, kRight_Side } Side;
+    typedef enum { kLeft_Side, kRight_Side } Side;
     struct MonotonePoly {
-        MonotonePoly()
-            : fSide(kNeither_Side)
+        MonotonePoly(Edge* edge, Side side)
+            : fSide(side)
+            , fFirstEdge(nullptr)
+            , fLastEdge(nullptr)
             , fPrev(nullptr)
-            , fNext(nullptr) {}
+            , fNext(nullptr) {
+            addEdge(edge);
+        }
         Side          fSide;
-        VertexList    fVertices;
+        Edge*         fFirstEdge;
+        Edge*         fLastEdge;
         MonotonePoly* fPrev;
         MonotonePoly* fNext;
-        bool addVertex(Vertex* v, Side side, SkChunkAlloc& alloc) {
-            Vertex* newV = ALLOC_NEW(Vertex, (v->fPoint), alloc);
-            bool done = false;
-            if (fSide == kNeither_Side) {
-                fSide = side;
+        void addEdge(Edge* edge) {
+            if (fSide == kRight_Side) {
+                list_insert<Edge, &Edge::fRightPolyPrev, &Edge::fRightPolyNext>(
+                    edge, fLastEdge, nullptr, &fFirstEdge, &fLastEdge);
             } else {
-                done = side != fSide;
+                list_insert<Edge, &Edge::fLeftPolyPrev, &Edge::fLeftPolyNext>(
+                    edge, fLastEdge, nullptr, &fFirstEdge, &fLastEdge);
             }
-            if (fSide == kRight_Side) {
-                fVertices.append(newV);
-            } else {
-                fVertices.prepend(newV);
-            }
-            return done;
         }
 
         SkPoint* emit(SkPoint* data) {
-            Vertex* first = fVertices.fHead;
+            Edge* e = fFirstEdge;
+            e->fTop->fPrev = e->fTop->fNext = nullptr;
+            VertexList vertices;
+            vertices.append(e->fTop);
+            while (e != nullptr) {
+                e->fBottom->fPrev = e->fBottom->fNext = nullptr;
+                if (kRight_Side == fSide) {
+                    vertices.append(e->fBottom);
+                    e = e->fRightPolyNext;
+                } else {
+                    vertices.prepend(e->fBottom);
+                    e = e->fLeftPolyNext;
+                }
+            }
+            Vertex* first = vertices.fHead;
             Vertex* v = first->fNext;
-            while (v != fVertices.fTail) {
+            while (v != vertices.fTail) {
                 SkASSERT(v && v->fPrev && v->fNext);
                 Vertex* prev = v->fPrev;
                 Vertex* curr = v;
                 Vertex* next = v->fNext;
                 double ax = static_cast<double>(curr->fPoint.fX) - prev->fPoint.fX;
                 double ay = static_cast<double>(curr->fPoint.fY) - prev->fPoint.fY;
                 double bx = static_cast<double>(next->fPoint.fX) - curr->fPoint.fX;
                 double by = static_cast<double>(next->fPoint.fY) - curr->fPoint.fY;
                 if (ax * by - ay * bx >= 0.0) {
                     data = emit_triangle(prev, curr, next, data);
                     v->fPrev->fNext = v->fNext;
                     v->fNext->fPrev = v->fPrev;
                     if (v->fPrev == first) {
                         v = v->fNext;
                     } else {
                         v = v->fPrev;
                     }
                 } else {
                     v = v->fNext;
                 }
             }
             return data;
         }
     };
-    Poly* addVertex(Vertex* v, Side side, SkChunkAlloc& alloc) {
-        LOG("addVertex() to %d at %g (%g, %g), %s side\n", fID, v->fID, v->fPoint.fX, v->fPoint.fY,
-               side == kLeft_Side ? "left" : side == kRight_Side ? "right" : "neither");
+    void addEdge(Edge* e, Side side, SkChunkAlloc& alloc) {
+        LOG("addEdge (%g,%g)-(%g,%g) to poly %d, %s side\n",
+               e->fTop->fPoint.fX, e->fTop->fPoint.fY,
+               e->fBottom->fPoint.fX, e->fBottom->fPoint.fY,

[robertphillips, 2016/06/02 12:19:48]

Does the "neither" case still make sense ?

[Stephen White, 2016/06/02 18:01:21]

Good point. Removed.

+               fID, side == kLeft_Side ? "left" : side == kRight_Side ? "right" : "neither");
         Poly* partner = fPartner;
-        Poly* poly = this;
         if (partner) {
             fPartner = partner->fPartner = nullptr;
         }
-        if (!fActive) {
-            fActive = ALLOC_NEW(MonotonePoly, (), alloc);
+        if (!fMonotones.fTail) {
+            fMonotones.append(ALLOC_NEW(MonotonePoly, (e, side), alloc));
+            fCount += 2;
+        } else if (side == fMonotones.fTail->fSide) {
+            fMonotones.fTail->addEdge(e);
+            fCount++;
+        } else {
+            if (e->fBottom == fMonotones.fTail->fLastEdge->fBottom) {
+                return;
+            }
+            e = ALLOC_NEW(Edge, (fMonotones.fTail->fLastEdge->fBottom, e->fBottom, 1), alloc);
+            fMonotones.fTail->addEdge(e);
+            fCount++;
+            MonotonePoly* m;
+            if (partner) {
+                m = partner->fMonotones.fTail;
+                m->addEdge(e);
+                partner->fMonotones.remove(m);
+            } else {
+                m = ALLOC_NEW(MonotonePoly, (e, side), alloc);
+            }
+            fCount += 2;
+            fMonotones.append(m);
         }
-        if (fActive->addVertex(v, side, alloc)) {
-            if (fTail) {
-                fActive->fPrev = fTail;
-                fTail->fNext = fActive;
-                fTail = fActive;
-            } else {
-                fHead = fTail = fActive;
-            }
-            if (partner) {
-                partner->addVertex(v, side, alloc);
-                poly = partner;
-            } else {
-                Vertex* prev = fActive->fSide == Poly::kLeft_Side ?
-                               fActive->fVertices.fHead->fNext : fActive->fVertices.fTail->fPrev;
-                fActive = ALLOC_NEW(MonotonePoly, , alloc);
-                fActive->addVertex(prev, Poly::kNeither_Side, alloc);
-                fActive->addVertex(v, side, alloc);
-            }
-        }
-        fCount++;
-        return poly;
-    }
-    void end(Vertex* v, SkChunkAlloc& alloc) {
-        LOG("end() %d at %g, %g\n", fID, v->fPoint.fX, v->fPoint.fY);
-        if (fPartner) {
-            fPartner = fPartner->fPartner = nullptr;
-        }
-        addVertex(v, fActive->fSide == kLeft_Side ? kRight_Side : kLeft_Side, alloc);
     }
     SkPoint* emit(SkPoint *data) {
         if (fCount < 3) {
             return data;
         }
         LOG("emit() %d, size %d\n", fID, fCount);
-        for (MonotonePoly* m = fHead; m != nullptr; m = m->fNext) {
+        for (MonotonePoly* m = fMonotones.fHead; m != nullptr; m = m->fNext) {
             data = m->emit(data);
         }
         return data;
     }
+    Vertex* lastVertex() const {
+        return fMonotones.fTail ?  fMonotones.fTail->fLastEdge->fBottom : fFirstVertex;
+    }
+    Vertex* fFirstVertex;
     int fWinding;
-    MonotonePoly* fHead;
-    MonotonePoly* fTail;
-    MonotonePoly* fActive;
+    List<MonotonePoly> fMonotones;
     Poly* fNext;
     Poly* fPartner;
     int fCount;
 #if LOGGING_ENABLED
     int fID;
 #endif
 };
 
 /***************************************************************************************/
 
 bool coincident(const SkPoint& a, const SkPoint& b) {
     return a == b;
 }
 
 Poly* new_poly(Poly** head, Vertex* v, int winding, SkChunkAlloc& alloc) {
-    Poly* poly = ALLOC_NEW(Poly, (winding), alloc);
-    poly->addVertex(v, Poly::kNeither_Side, alloc);
+    Poly* poly = ALLOC_NEW(Poly, (v, winding), alloc);
     poly->fNext = *head;
     *head = poly;
     return poly;
 }
 
 Vertex* append_point_to_contour(const SkPoint& p, Vertex* prev, Vertex** head,
                                 SkChunkAlloc& alloc) {
     Vertex* v = ALLOC_NEW(Vertex, (p), alloc);
 #if LOGGING_ENABLED
     static float gID = 0.0f;
@@ skipping 718 matching lines @@
         for (Edge* e = v->fFirstEdgeAbove; e; e = e->fNextEdgeAbove) {
             LOG("%g -> %g, lpoly %d, rpoly %d\n", e->fTop->fID, e->fBottom->fID,
                 e->fLeftPoly ? e->fLeftPoly->fID : -1, e->fRightPoly ? e->fRightPoly->fID : -1);
         }
         LOG("edges below:\n");
         for (Edge* e = v->fFirstEdgeBelow; e; e = e->fNextEdgeBelow) {
             LOG("%g -> %g, lpoly %d, rpoly %d\n", e->fTop->fID, e->fBottom->fID,
                 e->fLeftPoly ? e->fLeftPoly->fID : -1, e->fRightPoly ? e->fRightPoly->fID : -1);
         }
 #endif
         if (v->fFirstEdgeAbove) {

[robertphillips, 2016/06/02 12:19:48]

Either "nullptr != e" or "e" ?

-            if (leftPoly) {
-                leftPoly = leftPoly->addVertex(v, Poly::kRight_Side, alloc);
-            }
-            if (rightPoly) {
-                rightPoly = rightPoly->addVertex(v, Poly::kLeft_Side, alloc);
-            }
-            for (Edge* e = v->fFirstEdgeAbove; e != v->fLastEdgeAbove; e = e->fNextEdgeAbove) {
-                Edge* leftEdge = e;
-                Edge* rightEdge = e->fNextEdgeAbove;
-                SkASSERT(rightEdge->isRightOf(leftEdge->fTop));
-                remove_edge(leftEdge, &activeEdges);
-                if (leftEdge->fRightPoly) {
-                    leftEdge->fRightPoly->end(v, alloc);
+            for (Edge* e = v->fFirstEdgeAbove; e != nullptr; e = e->fNextEdgeAbove) {
+                remove_edge(e, &activeEdges);
+                if (e->fLeftPoly) {
+                    e->fLeftPoly->addEdge(e, Poly::kRight_Side, alloc);
                 }
-                if (rightEdge->fLeftPoly && rightEdge->fLeftPoly != leftEdge->fRightPoly) {
-                    rightEdge->fLeftPoly->end(v, alloc);
+                if (e->fRightPoly) {
+                    e->fRightPoly->addEdge(e, Poly::kLeft_Side, alloc);
                 }
             }
-            remove_edge(v->fLastEdgeAbove, &activeEdges);
             if (!v->fFirstEdgeBelow) {
                 if (leftPoly && rightPoly && leftPoly != rightPoly) {
                     SkASSERT(leftPoly->fPartner == nullptr && rightPoly->fPartner == nullptr);
                     rightPoly->fPartner = leftPoly;
                     leftPoly->fPartner = rightPoly;
                 }
             }
         }
         if (v->fFirstEdgeBelow) {
             if (!v->fFirstEdgeAbove) {
-                if (leftPoly && leftPoly == rightPoly) {
-                    // Split the poly.
-                    if (leftPoly->fActive->fSide == Poly::kLeft_Side) {
-                        leftPoly = new_poly(&polys, leftEnclosingEdge->fTop, leftPoly->fWinding,
-                                            alloc);
-                        leftPoly->addVertex(v, Poly::kRight_Side, alloc);
-                        rightPoly->addVertex(v, Poly::kLeft_Side, alloc);
-                        leftEnclosingEdge->fRightPoly = leftPoly;
-                    } else {
-                        rightPoly = new_poly(&polys, rightEnclosingEdge->fTop, rightPoly->fWinding,
-                                             alloc);
-                        rightPoly->addVertex(v, Poly::kLeft_Side, alloc);
-                        leftPoly->addVertex(v, Poly::kRight_Side, alloc);
-                        rightEnclosingEdge->fLeftPoly = rightPoly;
+                if (leftPoly) {
+                    if (leftPoly == rightPoly) {
+                        if (leftPoly->fMonotones.fTail &&
+                            leftPoly->fMonotones.fTail->fSide == Poly::kLeft_Side) {
+                            leftPoly = new_poly(&polys, leftPoly->lastVertex(),
+                                                leftPoly->fWinding, alloc);
+                            leftEnclosingEdge->fRightPoly = leftPoly;
+                        } else {
+                            rightPoly = new_poly(&polys, rightPoly->lastVertex(),
+                                                 rightPoly->fWinding, alloc);
+                            rightEnclosingEdge->fLeftPoly = rightPoly;
+                        }
                     }
-                } else {
-                    if (leftPoly) {
-                        leftPoly = leftPoly->addVertex(v, Poly::kRight_Side, alloc);
-                    }
-                    if (rightPoly) {
-                        rightPoly = rightPoly->addVertex(v, Poly::kLeft_Side, alloc);
-                    }
+                    Edge* join = ALLOC_NEW(Edge, (leftPoly->lastVertex(), v, 1), alloc);
+                    leftPoly->addEdge(join, Poly::kRight_Side, alloc);
+                    rightPoly->addEdge(join, Poly::kLeft_Side, alloc);
                 }
             }
             Edge* leftEdge = v->fFirstEdgeBelow;
             leftEdge->fLeftPoly = leftPoly;
             insert_edge(leftEdge, leftEnclosingEdge, &activeEdges);
             for (Edge* rightEdge = leftEdge->fNextEdgeBelow; rightEdge;
                  rightEdge = rightEdge->fNextEdgeBelow) {
                 insert_edge(rightEdge, leftEdge, &activeEdges);
                 int winding = leftEdge->fLeftPoly ? leftEdge->fLeftPoly->fWinding : 0;
                 winding += leftEdge->fWinding;
@@ skipping 174 matching lines @@
         }
     }
     int actualCount = static_cast<int>(vertsEnd - *verts);
     SkASSERT(actualCount <= count);
     SkASSERT(pointsEnd - points == actualCount);
     delete[] points;
     return actualCount;
 }
 
 } // namespace