Fix double blend in GrAAConvexPathRenderer

src/gpu/GrAAConvexPathRenderer.cpp

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrAAConvexPathRenderer.h"
 
@@ skipping 407 matching lines @@
             verts[*v + 2].fUV.set(0, 0);
             verts[*v + 3].fUV.set(0, -SK_Scalar1);
             verts[*v + 4].fUV.set(0, -SK_Scalar1);
 
             verts[*v + 0].fD0 = verts[*v + 0].fD1 = -SK_Scalar1;
             verts[*v + 1].fD0 = verts[*v + 1].fD1 = -SK_Scalar1;
             verts[*v + 2].fD0 = verts[*v + 2].fD1 = -SK_Scalar1;
             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]};
 
             SkVector midVec = segb.fNorms[0] + segb.fNorms[1];
             midVec.normalize();
 
             verts[*v + 0].fPos = fanPt;
             verts[*v + 1].fPos = qpts[0];
             verts[*v + 2].fPos = qpts[2];
             verts[*v + 3].fPos = qpts[0] + segb.fNorms[0];
@@ skipping 23 matching lines @@
             idxs[*i + 1] = *v + 1;
             idxs[*i + 2] = *v + 2;
             idxs[*i + 3] = *v + 4;
             idxs[*i + 4] = *v + 3;
             idxs[*i + 5] = *v + 2;
 
             idxs[*i + 6] = *v + 5;
             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;
         }
     }
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 /*
  * Quadratic specified by 0=u^2-v canonical coords. u and v are the first
  * two components of the vertex attribute. Coverage is based on signed
  * distance with negative being inside, positive outside. The edge is specified in
@@ skipping 384 matching lines @@
     geometry.fColor = color;
     geometry.fViewMatrix = vm;
     geometry.fPath = path;
 
     SkAutoTUnref<GrBatch> batch(AAConvexPathBatch::Create(geometry));
     target->drawBatch(pipelineBuilder, batch, &devRect);
 
     return true;
 
 }