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GrTessellator: fix for three edges becoming collinear after splitting.

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In rare cases, a single edge can become collinear with two adjacent
neighbour edges after it's split. The solution is to continue to merge
until no collinear edges are found.

BUG=722000

Change-Id: Ia5dd212b7acfb40ed1d6c74ebfa9e4a4746fe40a
Reviewed-on: https://skia-review.googlesource.com/17963
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>
This commit is contained in:
Stephen White 2017-05-25 14:47:11 -04:00 committed by Skia Commit-Bot
parent 506262665c
commit 6eca90fea6
2 changed files with 60 additions and 13 deletions
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33
src/gpu/GrTessellator.cpp
View File

@ -959,20 +959,27 @@ void merge_edges_below(Edge* edge, Edge* other, EdgeList* activeEdges, Comparato
}
void merge_collinear_edges(Edge* edge, EdgeList* activeEdges, Comparator& c) {
if (edge->fPrevEdgeAbove && (edge->fTop == edge->fPrevEdgeAbove->fTop ||
!edge->fPrevEdgeAbove->isLeftOf(edge->fTop))) {
merge_edges_above(edge, edge->fPrevEdgeAbove, activeEdges, c);
} else if (edge->fNextEdgeAbove && (edge->fTop == edge->fNextEdgeAbove->fTop ||
!edge->isLeftOf(edge->fNextEdgeAbove->fTop))) {
merge_edges_above(edge, edge->fNextEdgeAbove, activeEdges, c);
}
if (edge->fPrevEdgeBelow && (edge->fBottom == edge->fPrevEdgeBelow->fBottom ||
!edge->fPrevEdgeBelow->isLeftOf(edge->fBottom))) {
merge_edges_below(edge, edge->fPrevEdgeBelow, activeEdges, c);
} else if (edge->fNextEdgeBelow && (edge->fBottom == edge->fNextEdgeBelow->fBottom ||
!edge->isLeftOf(edge->fNextEdgeBelow->fBottom))) {
merge_edges_below(edge, edge->fNextEdgeBelow, activeEdges, c);
for (;;) {
if (edge->fPrevEdgeAbove && (edge->fTop == edge->fPrevEdgeAbove->fTop ||
!edge->fPrevEdgeAbove->isLeftOf(edge->fTop))) {
merge_edges_above(edge, edge->fPrevEdgeAbove, activeEdges, c);
} else if (edge->fNextEdgeAbove && (edge->fTop == edge->fNextEdgeAbove->fTop ||
!edge->isLeftOf(edge->fNextEdgeAbove->fTop))) {
merge_edges_above(edge, edge->fNextEdgeAbove, activeEdges, c);
} else if (edge->fPrevEdgeBelow && (edge->fBottom == edge->fPrevEdgeBelow->fBottom ||
!edge->fPrevEdgeBelow->isLeftOf(edge->fBottom))) {
merge_edges_below(edge, edge->fPrevEdgeBelow, activeEdges, c);
} else if (edge->fNextEdgeBelow && (edge->fBottom == edge->fNextEdgeBelow->fBottom ||
!edge->isLeftOf(edge->fNextEdgeBelow->fBottom))) {
merge_edges_below(edge, edge->fNextEdgeBelow, activeEdges, 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));
}
void split_edge(Edge* edge, Vertex* v, EdgeList* activeEdges, Comparator& c, SkArenaAlloc& alloc);

40
tests/TessellatingPathRendererTests.cpp
View File

@ -275,6 +275,45 @@ static SkPath create_path_18() {
return path;
}
// Exercises the case where an edge becomes collinear with *two* of its
// adjacent neighbour edges after splitting.
// This is a reduction from
// http://mooooo.ooo/chebyshev-sine-approximation/horner_ulp.svg
static SkPath create_path_19() {
SkPath path;
path.moveTo( 351.99298095703125, 348.23046875);
path.lineTo( 351.91876220703125, 347.33984375);
path.lineTo( 351.91876220703125, 346.1953125);
path.lineTo( 351.90313720703125, 347.734375);
path.lineTo( 351.90313720703125, 346.1328125);
path.lineTo( 351.87579345703125, 347.93359375);
path.lineTo( 351.87579345703125, 345.484375);
path.lineTo( 351.86407470703125, 347.7890625);
path.lineTo( 351.86407470703125, 346.2109375);
path.lineTo( 351.84844970703125, 347.63763427734375);
path.lineTo( 351.84454345703125, 344.19232177734375);
path.lineTo( 351.78204345703125, 346.9483642578125);
path.lineTo( 351.758636474609375, 347.18310546875);
path.lineTo( 351.75469970703125, 346.75);
path.lineTo( 351.75469970703125, 345.46875);
path.lineTo( 352.5546875, 345.46875);
path.lineTo( 352.55078125, 347.01953125);
path.lineTo( 351.75079345703125, 347.02313232421875);
path.lineTo( 351.74688720703125, 346.15203857421875);
path.lineTo( 351.74688720703125, 347.646148681640625);
path.lineTo( 352.5390625, 346.94140625);
path.lineTo( 351.73907470703125, 346.94268798828125);
path.lineTo( 351.73516845703125, 344.48565673828125);
path.lineTo( 352.484375, 346.73828125);
path.lineTo( 351.68438720703125, 346.7401123046875);
path.lineTo( 352.4765625, 346.546875);
path.lineTo( 351.67657470703125, 346.54937744140625);
path.lineTo( 352.47265625, 346.75390625);
path.lineTo( 351.67266845703125, 346.756622314453125);
path.lineTo( 351.66876220703125, 345.612091064453125);
return path;
}
static sk_sp<GrFragmentProcessor> create_linear_gradient_processor(GrContext* ctx) {
SkPoint pts[2] = { {0, 0}, {1, 1} };
SkColor colors[2] = { SK_ColorGREEN, SK_ColorBLUE };
@ -350,5 +389,6 @@ DEF_GPUTEST_FOR_ALL_CONTEXTS(TessellatingPathRendererTests, reporter, ctxInfo) {
sk_sp<GrFragmentProcessor> fp(create_linear_gradient_processor(ctx));
test_path(ctx, rtc.get(), create_path_17(), nonInvertibleMatrix, GrAAType::kCoverage, fp);
test_path(ctx, rtc.get(), create_path_18());
test_path(ctx, rtc.get(), create_path_19());
}
#endif