Decrease GPU drawn brightness for < 1 pixel wide/high rects

src/gpu/GrAARectRenderer.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 "GrAARectRenderer.h"
 #include "GrRefCnt.h"
 #include "GrGpu.h"
 #include "gl/GrGLEffect.h"
 #include "GrTBackendEffectFactory.h"
+#include "SkColorPriv.h"
 
 SK_DEFINE_INST_COUNT(GrAARectRenderer)
 
 ///////////////////////////////////////////////////////////////////////////////
 class GrGLAlignedRectEffect;
 
 // Axis Aligned special case
 class GrAlignedRectEffect : public GrEffect {
 public:
     static GrEffectRef* Create() {
@@ skipping 359 matching lines @@
         return;
     }
 
     intptr_t verts = reinterpret_cast<intptr_t>(geo.vertices());
     size_t vsize = drawState->getVertexSize();
     GrAssert(sizeof(GrPoint) + sizeof(GrColor) == vsize);
 
     GrPoint* fan0Pos = reinterpret_cast<GrPoint*>(verts);
     GrPoint* fan1Pos = reinterpret_cast<GrPoint*>(verts + 4 * vsize);
 
+    SkScalar inset = SkMinScalar(devRect.width(), SK_Scalar1);
+    inset = SK_ScalarHalf * SkMinScalar(inset, devRect.height());
+
     if (combinedMatrix.rectStaysRect()) {
         // Temporarily #if'ed out. We don't want to pass in the devRect but
         // right now it is computed in GrContext::apply_aa_to_rect and we don't
         // want to throw away the work
 #if 0
         SkRect devRect;
         combinedMatrix.mapRect(&devRect, rect);
 #endif
 
         set_inset_fan(fan0Pos, vsize, devRect, -SK_ScalarHalf, -SK_ScalarHalf);
-        set_inset_fan(fan1Pos, vsize, devRect,  SK_ScalarHalf,  SK_ScalarHalf);
+        set_inset_fan(fan1Pos, vsize, devRect, inset,  inset);
     } else {
         // compute transformed (1, 0) and (0, 1) vectors
         SkVector vec[2] = {
           { combinedMatrix[SkMatrix::kMScaleX], combinedMatrix[SkMatrix::kMSkewY] },
           { combinedMatrix[SkMatrix::kMSkewX],  combinedMatrix[SkMatrix::kMScaleY] }
         };
 
         vec[0].normalize();
         vec[0].scale(SK_ScalarHalf);
         vec[1].normalize();
@@ skipping 23 matching lines @@
         *((SkPoint*)((intptr_t)fan1Pos + 3 * vsize)) =
             *((SkPoint*)((intptr_t)fan0Pos + 3 * vsize)) - vec[0] + vec[1];
         *((SkPoint*)((intptr_t)fan0Pos + 3 * vsize)) += vec[0] - vec[1];
     }
 
     verts += sizeof(GrPoint);
     for (int i = 0; i < 4; ++i) {
         *reinterpret_cast<GrColor*>(verts + i * vsize) = 0;
     }
 
+    int scale;
+    if (inset < SK_ScalarHalf) {
+        scale = SkScalarFloorToInt(512.0f * inset / (inset + SK_ScalarHalf));
+        SkASSERT(scale >= 0 && scale <= 255);
+    } else {
+        scale = 0xff;
+    }
+
     GrColor innerColor;
     if (useVertexCoverage) {
-        innerColor = 0xffffffff;
+        innerColor = scale | (scale << 8) | (scale << 16) | (scale << 24);
     } else {
-        innerColor = target->getDrawState().getColor();
+        if (0xff == scale) {
+            innerColor = target->getDrawState().getColor();
+        } else {
+            innerColor = SkAlphaMulQ(target->getDrawState().getColor(), scale);
+        }
     }
 
     verts += 4 * vsize;
     for (int i = 0; i < 4; ++i) {
         *reinterpret_cast<GrColor*>(verts + i * vsize) = innerColor;
     }
 
     target->setIndexSourceToBuffer(indexBuffer);
     target->drawIndexedInstances(kTriangles_GrPrimitiveType, 1,
                                  kVertsPerAAFillRect,
@@ skipping 301 matching lines @@
     // can't call mapRect for devInside since it calls sort
     combinedMatrix.mapPoints((SkPoint*)&devInside, (const SkPoint*)&rects[1], 2);
 
     if (devInside.isEmpty()) {
         this->fillAARect(gpu, target, devOutside, SkMatrix::I(), devOutside, useVertexCoverage);
         return;
     }
 
     this->geometryStrokeAARect(gpu, target, devOutside, devInside, useVertexCoverage);
 }