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Fix for out-of-bounds intersection (found by fuzzer).

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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
This commit is contained in:
senorblanco 2015-03-02 09:34:13 -08:00 committed by Commit bot
parent b3310c2221
commit a2b6d28755
2 changed files with 24 additions and 7 deletions
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20
src/gpu/GrTessellatingPathRenderer.cpp
View File

@ -958,13 +958,19 @@ void split_edge(Edge* edge, Vertex* v, Edge** activeEdges, SkChunkAlloc& alloc)
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) {

11
tests/TessellatingPathRendererTests.cpp
View File

@ -220,6 +220,16 @@ static SkPath create_path_14() {
return path;
}
static SkPath create_path_15() {
SkPath path;
path.moveTo( 0.0f, 0.0f);
path.lineTo(10000.0f, 0.0f);
path.lineTo( 0.0f, -1.0f);
path.lineTo(10000.0f, 0.000001f);
path.lineTo( 0.0f, -30.0f);
return path;
}
static void test_path(GrDrawTarget* dt, GrRenderTarget* rt, const SkPath& path) {
GrTessellatingPathRenderer tess;
GrPipelineBuilder pipelineBuilder;
@ -259,5 +269,6 @@ DEF_GPUTEST(TessellatingPathRendererTests, reporter, factory) {
test_path(dt, rt, create_path_12());
test_path(dt, rt, create_path_13());
test_path(dt, rt, create_path_14());
test_path(dt, rt, create_path_15());
}
#endif