Fix rendering of drrects with small circular inner rrects.

Previously when the inner rrect was a circle with a radius of 1 we would
cause a inf * 0 in the shader which would lead to the shape not rendering.

This change also makes concentric circle drrects draw as stroked circles.

bug: chromium:789262

Change-Id: I6efbe3fdde25d6c4e031c7412d83df009afe014a
Reviewed-on: https://skia-review.googlesource.com/79141
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/gpu/effects/GrCircleEffect.h b/src/gpu/effects/GrCircleEffect.h
index bf6bd0e8e6..d721a78241 100644
--- a/src/gpu/effects/GrCircleEffect.h
+++ b/src/gpu/effects/GrCircleEffect.h
@@ -19,8 +19,14 @@ public:
     GrClipEdgeType edgeType() const { return fEdgeType; }
     SkPoint center() const { return fCenter; }
     float radius() const { return fRadius; }
+
     static std::unique_ptr<GrFragmentProcessor> Make(GrClipEdgeType edgeType, SkPoint center,
                                                      float radius) {
+        // A radius below half causes the implicit insetting done by this processor to become
+        // inverted. We could handle this case by making the processor code more complicated.
+        if (radius < .5f) {
+            return nullptr;
+        }
         return std::unique_ptr<GrFragmentProcessor>(new GrCircleEffect(edgeType, center, radius));
     }
     GrCircleEffect(const GrCircleEffect& src);