GrTessellator: handle collinear final vertex.

If the last vertex in a contour is collinear with its neighbours,
remove it (this edge case was missing). Otherwise, the simplify step
may try to split it indefinitely.

Bug: 851409
Change-Id: I7efa4e616cdc1508a73c7a9f3de9d3f571569af8
Reviewed-on: https://skia-review.googlesource.com/138106
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>

2 files changed, 14 insertions, 1 deletions

diff --git a/src/gpu/GrTessellator.cpp b/src/gpu/GrTessellator.cpp
index d6a64cdd46..6cd54380e6 100644
--- a/src/gpu/GrTessellator.cpp
+++ b/src/gpu/GrTessellator.cpp
@@ -1279,13 +1279,14 @@ void sanitize_contours(VertexList* contours, int contourCnt, bool approximate) {
                 round(&v->fPoint);
             }
             Vertex* next = v->fNext;
+            Vertex* nextWrap = next ? next : contour->fHead;
             if (coincident(prev->fPoint, v->fPoint)) {
                 LOG("vertex %g,%g coincident; removing\n", v->fPoint.fX, v->fPoint.fY);
                 contour->remove(v);
             } else if (!v->fPoint.isFinite()) {
                 LOG("vertex %g,%g non-finite; removing\n", v->fPoint.fX, v->fPoint.fY);
                 contour->remove(v);
-            } else if (next && Line(prev->fPoint, next->fPoint).dist(v->fPoint) == 0.0) {
+            } else if (Line(prev->fPoint, nextWrap->fPoint).dist(v->fPoint) == 0.0) {
                 LOG("vertex %g,%g collinear; removing\n", v->fPoint.fX, v->fPoint.fY);
                 contour->remove(v);
             } else {
diff --git a/tests/TessellatingPathRendererTests.cpp b/tests/TessellatingPathRendererTests.cpp
index 0b30feecc0..a9913769df 100644
--- a/tests/TessellatingPathRendererTests.cpp
+++ b/tests/TessellatingPathRendererTests.cpp
@@ -560,6 +560,17 @@ static SkPath create_path_38() {
     return path;
 }
 
+// Reduction from crbug.com/851409.
+static SkPath create_path_39() {
+    SkPath path;
+    path.moveTo(2072553216, 0);
+    path.lineTo(2072553216, 1);
+    path.lineTo(2072553472, -13.5);
+    path.lineTo(2072553216, 0);
+    path.lineTo(2072553472, -6.5);
+    return path;
+}
+
 static std::unique_ptr<GrFragmentProcessor> create_linear_gradient_processor(GrContext* ctx) {
 
     SkPoint pts[2] = { {0, 0}, {1, 1} };
@@ -658,4 +669,5 @@ DEF_GPUTEST_FOR_ALL_CONTEXTS(TessellatingPathRendererTests, reporter, ctxInfo) {
     test_path(ctx, rtc.get(), create_path_36());
     test_path(ctx, rtc.get(), create_path_37());
     test_path(ctx, rtc.get(), create_path_38(), SkMatrix(), GrAAType::kCoverage);
+    test_path(ctx, rtc.get(), create_path_39());
 }