Trim the copy of the dst made for dst-reading effects using the clip and dev-bounds of draw.

src/gpu/GrOvalRenderer.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrOvalRenderer.h"
 
 #include "effects/GrCircleEdgeEffect.h"
@@ skipping 118 matching lines @@
             innerRadius = SkMaxScalar(0, radius - halfWidth);
         }
     }
 
     for (int i = 0; i < 4; ++i) {
         verts[i].fCenter = center;
         verts[i].fOuterRadius = outerRadius + 0.5f;
         verts[i].fInnerRadius = innerRadius - 0.5f;
     }
 
-    SkScalar L = -outerRadius;
-    SkScalar R = +outerRadius;
-    SkScalar T = -outerRadius;
-    SkScalar B = +outerRadius;
-
     // We've extended the outer radius out half a pixel to antialias.
     // Expand the drawn rect here so all the pixels will be captured.
-    L += center.fX - SK_ScalarHalf;
-    R += center.fX + SK_ScalarHalf;
-    T += center.fY - SK_ScalarHalf;
-    B += center.fY + SK_ScalarHalf;
+    SkRect bounds = SkRect::MakeLTRB(
+        center.fX - outerRadius - SK_ScalarHalf,
+        center.fY - outerRadius - SK_ScalarHalf,
+        center.fX + outerRadius + SK_ScalarHalf,
+        center.fY + outerRadius + SK_ScalarHalf
+    );
 
-    verts[0].fPos = SkPoint::Make(L, T);
-    verts[1].fPos = SkPoint::Make(R, T);
-    verts[2].fPos = SkPoint::Make(L, B);
-    verts[3].fPos = SkPoint::Make(R, B);
+    verts[0].fPos = SkPoint::Make(bounds.fLeft,  bounds.fTop);
+    verts[1].fPos = SkPoint::Make(bounds.fRight, bounds.fTop);
+    verts[2].fPos = SkPoint::Make(bounds.fLeft,  bounds.fBottom);
+    verts[3].fPos = SkPoint::Make(bounds.fRight, bounds.fBottom);
 
-    target->drawNonIndexed(kTriangleStrip_GrPrimitiveType, 0, 4);
+    target->drawNonIndexed(kTriangleStrip_GrPrimitiveType, 0, 4, &bounds);
 }
 
 void GrOvalRenderer::drawEllipse(GrDrawTarget* target,
                                  const GrPaint& paint,
                                  const GrRect& ellipse,
                                  const SkStrokeRec& stroke)
 {
     GrDrawState* drawState = target->drawState();
 #ifdef SK_DEBUG
     {
@@ skipping 101 matching lines @@
     T += center.fY - SK_ScalarHalf;
     B += center.fY + SK_ScalarHalf;
 
     verts[0].fPos = SkPoint::Make(L, T);
     verts[1].fPos = SkPoint::Make(R, T);
     verts[2].fPos = SkPoint::Make(L, B);
     verts[3].fPos = SkPoint::Make(R, B);
 
     target->drawNonIndexed(kTriangleStrip_GrPrimitiveType, 0, 4);
 }