Fixed an assertion error in GrAAConvexTessellator. While adding a new point, it would check that the new point was not a duplicate of the previous point. It would then drop the previous point if it was in the middle of a straight line, and proceed to add the new point.

Unfortunately, floating point precision issues mean that sometimes, after dropping the previous point, we'd end up with the newly-added point as a duplicate of the new previous point, tripping an assertion failure.

BUG=skia:4732
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1557903002

Review URL: https://codereview.chromium.org/1557903002

1 files changed, 7 insertions, 0 deletions

diff --git a/src/gpu/batches/GrAAConvexTessellator.cpp b/src/gpu/batches/GrAAConvexTessellator.cpp
index 5ef9aefddd..c3d25948de 100644
--- a/src/gpu/batches/GrAAConvexTessellator.cpp
+++ b/src/gpu/batches/GrAAConvexTessellator.cpp
@@ -835,6 +835,13 @@ void GrAAConvexTessellator::lineTo(SkPoint p, bool isCurve) {
         this->popLastPt();
         fNorms.pop();
         fIsCurve.pop();
+        // double-check that the new last point is not a duplicate of the new point. In an ideal
+        // world this wouldn't be necessary (since it's only possible for non-convex paths), but
+        // floating point precision issues mean it can actually happen on paths that were determined
+        // to be convex.
+        if (duplicate_pt(p, this->lastPoint())) {
+            return;
+        }
     }
     SkScalar initialRingCoverage = fStrokeWidth < 0.0f ? 0.5f : 1.0f;
     this->addPt(p, 0.0f, initialRingCoverage, false, isCurve);