Fix double blend in GrAAConvexPathRenderer

src/gpu/GrAAConvexPathRenderer.cpp

Index: src/gpu/GrAAConvexPathRenderer.cpp
diff --git a/src/gpu/GrAAConvexPathRenderer.cpp b/src/gpu/GrAAConvexPathRenderer.cpp
index 1813803d8ad7ea41a7556ee1d32b01c366be8f60..0235741c5abe96ea8714d2e4270b48d768889413 100644
--- a/src/gpu/GrAAConvexPathRenderer.cpp
+++ b/src/gpu/GrAAConvexPathRenderer.cpp
@@ -425,20 +425,26 @@ static void create_vertices(const SegmentArray&  segments,
             verts[*v + 3].fD0 = verts[*v + 3].fD1 = -SK_Scalar1;
             verts[*v + 4].fD0 = verts[*v + 4].fD1 = -SK_Scalar1;
 
-            idxs[*i + 0] = *v + 0;
-            idxs[*i + 1] = *v + 2;
-            idxs[*i + 2] = *v + 1;
+            idxs[*i + 0] = *v + 3;
+            idxs[*i + 1] = *v + 1;
+            idxs[*i + 2] = *v + 2;
 
-            idxs[*i + 3] = *v + 3;
-            idxs[*i + 4] = *v + 1;
+            idxs[*i + 3] = *v + 4;
+            idxs[*i + 4] = *v + 3;
             idxs[*i + 5] = *v + 2;
 
-            idxs[*i + 6] = *v + 4;
-            idxs[*i + 7] = *v + 3;
-            idxs[*i + 8] = *v + 2;
+            *i += 6;
+
+            // Fill the interior, if any.
+            if (count > 2) {

[Chris Dalton, 2015/04/21 11:49:05]

Do we need to worry about the case where two colinear lineTo's close off a
quadratic? (In other words, the interior is still empty but segment count > 2)
Or do they already get collapsed into a single lineTo?

[bsalomon, 2015/04/21 15:50:07]

SkPath won't notice colinear lines when constructing a path so I think you could
have this case. Maybe the empty interior could be checked when computing the
center of mass?

Adding Rob, since he is looking to rewrite the tessellation for convex paths.

+                idxs[*i + 0] = *v + 0;
+                idxs[*i + 1] = *v + 2;
+                idxs[*i + 2] = *v + 1;
+
+                *i += 3;
+            }
 
             *v += 5;
-            *i += 9;
         } else {
             SkPoint qpts[] = {sega.endPt(), segb.fPts[0], segb.fPts[1]};
 
@@ -482,12 +488,18 @@ static void create_vertices(const SegmentArray&  segments,
             idxs[*i + 7] = *v + 3;
             idxs[*i + 8] = *v + 4;
 
-            idxs[*i +  9] = *v + 0;
-            idxs[*i + 10] = *v + 2;
-            idxs[*i + 11] = *v + 1;
+            *i += 9;
+
+            // Fill the interior, if any.
+            if (count > 2) {

[Chris Dalton, 2015/04/21 11:41:59]

I decided to err on the side of minimal change, but let me know if you want me
to rearrange things so we only write fanPt to the vertex array inside this
branch.

+                idxs[*i + 0] = *v + 0;
+                idxs[*i + 1] = *v + 2;
+                idxs[*i + 2] = *v + 1;
+
+                *i += 3;
+            }
 
             *v += 6;
-            *i += 12;
         }
     }
 }