Fix for out-of-bounds intersection (found by fuzzer).
Sometimes, the intersection returned by check_intersection() is
out-of-bounds for both edges (above both tops or below both bottoms)
due to floating-point inaccuracy. This causes split_edge() to create a
tiny negative-length edge on one side (which would then assert).
Although we could safely remove this assert and allow the negative
length edge to be removed, it's faster/safer to simply avoid its
creation in the first place by adjusting one edge to the other edge's
endpoint.
Added a new unit test to exercise this case.
Review URL: https://codereview.chromium.org/968993002
diff --git a/src/gpu/GrTessellatingPathRenderer.cpp b/src/gpu/GrTessellatingPathRenderer.cpp
index be28a69..a9ae6fa 100644
--- a/src/gpu/GrTessellatingPathRenderer.cpp
+++ b/src/gpu/GrTessellatingPathRenderer.cpp
@@ -958,13 +958,19 @@
LOG("splitting edge (%g -> %g) at vertex %g (%g, %g)\n",
edge->fTop->fID, edge->fBottom->fID,
v->fID, v->fPoint.fX, v->fPoint.fY);
- Edge* newEdge = ALLOC_NEW(Edge, (v, edge->fBottom, edge->fWinding), alloc);
- insert_edge_below(newEdge, v);
- insert_edge_above(newEdge, edge->fBottom);
- set_bottom(edge, v, activeEdges);
- cleanup_active_edges(edge, activeEdges, alloc);
- fix_active_state(newEdge, activeEdges);
- merge_collinear_edges(newEdge, activeEdges);
+ if (sweep_lt(v->fPoint, edge->fTop->fPoint)) {
+ set_top(edge, v, activeEdges);
+ } else if (sweep_gt(v->fPoint, edge->fBottom->fPoint)) {
+ set_bottom(edge, v, activeEdges);
+ } else {
+ Edge* newEdge = ALLOC_NEW(Edge, (v, edge->fBottom, edge->fWinding), alloc);
+ insert_edge_below(newEdge, v);
+ insert_edge_above(newEdge, edge->fBottom);
+ set_bottom(edge, v, activeEdges);
+ cleanup_active_edges(edge, activeEdges, alloc);
+ fix_active_state(newEdge, activeEdges);
+ merge_collinear_edges(newEdge, activeEdges);
+ }
}
void merge_vertices(Vertex* src, Vertex* dst, Vertex** head, SkChunkAlloc& alloc) {