Add device space "nudge" to gpu draws

src/gpu/effects/GrConvexPolyEffect.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrConvexPolyEffect.h"
 #include "GrInvariantOutput.h"
 #include "SkPath.h"
@@ skipping 119 matching lines @@
         fsBuilder->codeAppend("\t\tfloat xSub, ySub;\n");
         fsBuilder->codeAppendf("\t\txSub = min(%s.x - %s.x, 0.0);\n", fragmentPos, rectName);
         fsBuilder->codeAppendf("\t\txSub += min(%s.z - %s.x, 0.0);\n", rectName, fragmentPos);
         fsBuilder->codeAppendf("\t\tySub = min(%s.y - %s.y, 0.0);\n", fragmentPos, rectName);
         fsBuilder->codeAppendf("\t\tySub += min(%s.w - %s.y, 0.0);\n", rectName, fragmentPos);
         // Now compute coverage in x and y and multiply them to get the fraction of the pixel
         // covered.
         fsBuilder->codeAppendf("\t\tfloat alpha = (1.0 + max(xSub, -1.0)) * (1.0 + max(ySub, -1.0));\n");
     } else {
         fsBuilder->codeAppendf("\t\tfloat alpha = 1.0;\n");
-        fsBuilder->codeAppendf("\t\talpha *= (%s.x - %s.x) > -0.5 ? 1.0 : 0.0;\n", fragmentPos, rectName);
-        fsBuilder->codeAppendf("\t\talpha *= (%s.z - %s.x) > -0.5 ? 1.0 : 0.0;\n", rectName, fragmentPos);
-        fsBuilder->codeAppendf("\t\talpha *= (%s.y - %s.y) > -0.5 ? 1.0 : 0.0;\n", fragmentPos, rectName);
-        fsBuilder->codeAppendf("\t\talpha *= (%s.w - %s.y) > -0.5 ? 1.0 : 0.0;\n", rectName, fragmentPos);
+        fsBuilder->codeAppendf("\t\talpha *= (%s.x - %s.x) > -0.5 ? 1.0 : 0.0;\n",
+                               fragmentPos, rectName);
+        fsBuilder->codeAppendf("\t\talpha *= (%s.z - %s.x) > -0.5 ? 1.0 : 0.0;\n",
+                               rectName, fragmentPos);
+        fsBuilder->codeAppendf("\t\talpha *= (%s.y - %s.y) > -0.5 ? 1.0 : 0.0;\n",
+                               fragmentPos, rectName);
+        fsBuilder->codeAppendf("\t\talpha *= (%s.w - %s.y) > -0.5 ? 1.0 : 0.0;\n",
+                               rectName, fragmentPos);
     }
 
     if (GrProcessorEdgeTypeIsInverseFill(aare.getEdgeType())) {
         fsBuilder->codeAppend("\t\talpha = 1.0 - alpha;\n");
     }
     fsBuilder->codeAppendf("\t\t%s = %s;\n", outputColor,
                            (GrGLSLExpr4(inputColor) * GrGLSLExpr1("alpha")).c_str());
 }
 
 void GLAARectEffect::setData(const GrGLProgramDataManager& pdman, const GrProcessor& processor) {
     const AARectEffect& aare = processor.cast<AARectEffect>();
     const SkRect& rect = aare.getRect();
     if (rect != fPrevRect) {
-        pdman.set4f(fRectUniform, rect.fLeft + 0.5f, rect.fTop + 0.5f,
-                   rect.fRight - 0.5f, rect.fBottom - 0.5f);
+        // Add a device space "nudge" of 0.003f, 0.003f to match raster's rounding behavior for
+        // BW clipping/drawing
+        pdman.set4f(fRectUniform, rect.fLeft + 0.503f, rect.fTop + 0.503f,
+                                  rect.fRight - 0.497f, rect.fBottom - 0.497f);
         fPrevRect = rect;
     }
 }
 
 void GLAARectEffect::GenKey(const GrProcessor& processor, const GrGLCaps&,
                             GrProcessorKeyBuilder* b) {
     const AARectEffect& aare = processor.cast<AARectEffect>();
     b->add32(aare.getEdgeType());
 }
 
@@ skipping 45 matching lines @@
                                             kVec3f_GrSLType,
                                              kDefault_GrSLPrecision,
                                              "edges",
                                             cpe.getEdgeCount(),
                                             &edgeArrayName);
     GrGLFPFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
     fsBuilder->codeAppend("\t\tfloat alpha = 1.0;\n");
     fsBuilder->codeAppend("\t\tfloat edge;\n");
     const char* fragmentPos = fsBuilder->fragmentPosition();
     for (int i = 0; i < cpe.getEdgeCount(); ++i) {
-        fsBuilder->codeAppendf("\t\tedge = dot(%s[%d], vec3(%s.x, %s.y, 1));\n",
+        // Add a device space "nudge" of 0.003f, 0.003f to match raster's rounding behavior for
+        // BW clipping/drawing. Since we are "nudging" fragment positions we have to go in
+        // the opposite direction.
+        fsBuilder->codeAppendf("\t\tedge = dot(%s[%d], vec3(%s.x - 0.003, %s.y - 0.003, 1));\n",
                                edgeArrayName, i, fragmentPos, fragmentPos);
         if (GrProcessorEdgeTypeIsAA(cpe.getEdgeType())) {
             fsBuilder->codeAppend("\t\tedge = clamp(edge, 0.0, 1.0);\n");
         } else {
             fsBuilder->codeAppend("\t\tedge = edge >= 0.5 ? 1.0 : 0.0;\n");
         }
         fsBuilder->codeAppend("\t\talpha *= edge;\n");
     }
 
     // Woe is me. See skbug.com/2149.
@@ skipping 137 matching lines @@
     }
 
     GrFragmentProcessor* fp;
     do {
         GrPrimitiveEdgeType edgeType = static_cast<GrPrimitiveEdgeType>(
                                         random->nextULessThan(kGrProcessorEdgeTypeCnt));
         fp = GrConvexPolyEffect::Create(edgeType, count, edges);
     } while (NULL == fp);
     return fp;
 }