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GrTessellator: fix for collinear edge merging.

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In some cases, two edges can be collinear when tested on one side
(e.g., left top vs right edge), but non-collinear when tested on the
other (e.g., right top vs left edge). We were actually merging based
on one criterion, but assserting based on the other.

The safest fix is to merge if either condition is true, and then
assert that both conditions are false.

Bug: 866319
Change-Id: Ia1be330caf62f6d7961746752f73993ca098d0a3
Reviewed-on: https://skia-review.googlesource.com/143501
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>
This commit is contained in:
Stephen White 2018-07-26 10:02:27 -04:00 committed by Skia Commit-Bot
parent b5093bc9ed
commit d26b4d865a
2 changed files with 39 additions and 14 deletions
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38
src/gpu/GrTessellator.cpp
View File

@ -1051,30 +1051,40 @@ void merge_edges_below(Edge* edge, Edge* other, EdgeList* activeEdges, Vertex**
}
}
bool top_collinear(Edge* left, Edge* right) {
if (!left || !right) {
return false;
}
return left->fTop->fPoint == right->fTop->fPoint ||
!left->isLeftOf(right->fTop) || !right->isRightOf(left->fTop);
}
bool bottom_collinear(Edge* left, Edge* right) {
if (!left || !right) {
return false;
}
return left->fBottom->fPoint == right->fBottom->fPoint ||
!left->isLeftOf(right->fBottom) || !right->isRightOf(left->fBottom);
}
void merge_collinear_edges(Edge* edge, EdgeList* activeEdges, Vertex** current, Comparator& c) {
for (;;) {
const SkPoint& top = edge->fTop->fPoint;
const SkPoint& bottom = edge->fBottom->fPoint;
if (edge->fPrevEdgeAbove && (edge->fPrevEdgeAbove->fTop->fPoint == top ||
!edge->fPrevEdgeAbove->isLeftOf(edge->fTop))) {
if (top_collinear(edge->fPrevEdgeAbove, edge)) {
merge_edges_above(edge->fPrevEdgeAbove, edge, activeEdges, current, c);
} else if (edge->fNextEdgeAbove && (edge->fNextEdgeAbove->fTop->fPoint == top ||
!edge->isLeftOf(edge->fNextEdgeAbove->fTop))) {
} else if (top_collinear(edge, edge->fNextEdgeAbove)) {
merge_edges_above(edge->fNextEdgeAbove, edge, activeEdges, current, c);
} else if (edge->fPrevEdgeBelow && (edge->fPrevEdgeBelow->fBottom->fPoint == bottom ||
!edge->fPrevEdgeBelow->isLeftOf(edge->fBottom))) {
} else if (bottom_collinear(edge->fPrevEdgeBelow, edge)) {
merge_edges_below(edge->fPrevEdgeBelow, edge, activeEdges, current, c);
} else if (edge->fNextEdgeBelow && (edge->fNextEdgeBelow->fBottom->fPoint == bottom ||
!edge->isLeftOf(edge->fNextEdgeBelow->fBottom))) {
} else if (bottom_collinear(edge, edge->fNextEdgeBelow)) {
merge_edges_below(edge->fNextEdgeBelow, edge, activeEdges, current, c);
} else {
break;
}
}
SkASSERT(!edge->fPrevEdgeAbove || edge->fPrevEdgeAbove->isLeftOf(edge->fTop));
SkASSERT(!edge->fPrevEdgeBelow || edge->fPrevEdgeBelow->isLeftOf(edge->fBottom));
SkASSERT(!edge->fNextEdgeAbove || edge->fNextEdgeAbove->isRightOf(edge->fTop));
SkASSERT(!edge->fNextEdgeBelow || edge->fNextEdgeBelow->isRightOf(edge->fBottom));
SkASSERT(!top_collinear(edge->fPrevEdgeAbove, edge));
SkASSERT(!top_collinear(edge, edge->fNextEdgeAbove));
SkASSERT(!bottom_collinear(edge->fPrevEdgeBelow, edge));
SkASSERT(!bottom_collinear(edge, edge->fNextEdgeBelow));
}
bool split_edge(Edge* edge, Vertex* v, EdgeList* activeEdges, Vertex** current, Comparator& c,

15
tests/TessellatingPathRendererTests.cpp
View File

@ -616,6 +616,20 @@ static SkPath create_path_42() {
return path;
}
// Reduction from crbug.com/866319. Cause is edges that are collinear when tested from
// one side, but non-collinear when tested from the other.
static SkPath create_path_43() {
SkPath path;
path.moveTo( 307316821852160, -28808363114496);
path.lineTo( 307165222928384, -28794154909696);
path.lineTo( 307013691113472, -28779948802048);
path.lineTo( 306862159298560, -28765744791552);
path.lineTo( 306870313025536, -28766508154880);
path.lineTo( 307049695019008, -28783327313920);
path.lineTo( 307408660332544, -28816974020608);
return path;
}
static std::unique_ptr<GrFragmentProcessor> create_linear_gradient_processor(GrContext* ctx) {
SkPoint pts[2] = { {0, 0}, {1, 1} };
@ -718,4 +732,5 @@ DEF_GPUTEST_FOR_ALL_CONTEXTS(TessellatingPathRendererTests, reporter, ctxInfo) {
test_path(ctx, rtc.get(), create_path_40());
test_path(ctx, rtc.get(), create_path_41(), SkMatrix(), GrAAType::kCoverage);
test_path(ctx, rtc.get(), create_path_42());
test_path(ctx, rtc.get(), create_path_43(), SkMatrix(), GrAAType::kCoverage);
}