Add GrEllipseEdgeEffect

src/gpu/effects/GrEllipseEdgeEffect.cpp

Index: src/gpu/effects/GrEllipseEdgeEffect.cpp
===================================================================
--- src/gpu/effects/GrEllipseEdgeEffect.cpp	(revision 0)
+++ src/gpu/effects/GrEllipseEdgeEffect.cpp	(working copy)
@@ -0,0 +1,83 @@
+/*
+ * 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 "GrEllipseEdgeEffect.h"
+#include "gl/GrGLEffect.h"
+#include "gl/GrGLEffectMatrix.h"
+#include "gl/GrGLSL.h"
+#include "gl/GrGLTexture.h"
+#include "GrTBackendEffectFactory.h"
+#include "GrTexture.h"
+
+#define ELLIPSE_EDGE_ATTR0 "aEllipseEdge"
+
+class GrGLEllipseEdgeEffect : public GrGLEffect {
+public:
+    GrGLEllipseEdgeEffect(const GrBackendEffectFactory& factory, const GrEffectRef&)
+    : INHERITED (factory) {}
+
+    virtual void emitCode(GrGLShaderBuilder* builder,
+                          const GrEffectStage&,
+                          EffectKey key,
+                          const char* vertexCoords,
+                          const char* outputColor,
+                          const char* inputColor,
+                          const TextureSamplerArray& samplers) SK_OVERRIDE {
+        const char *vsName, *fsName;
+        builder->addVarying(kVec4f_GrSLType, "EllipseEdge", &vsName, &fsName);
+        builder->addAttribute(kVec4f_GrSLType, ELLIPSE_EDGE_ATTR0);
+
+        builder->fVSCode.appendf("\t%s = " ELLIPSE_EDGE_ATTR0 ";\n", vsName);
+        
+        builder->fFSCode.append("\tfloat edgeAlpha;\n");
+        // translate to origin
+        builder->fFSCode.appendf("\tvec2 offset = (%s.xy - %s.xy);\n", builder->fragmentPosition(), fsName);
+        // scale y by xRadius/yRadius
+        builder->fFSCode.appendf("\toffset.y *= %s.w;\n", fsName);  
+        builder->fFSCode.append("\tfloat d = length(offset);\n");
+        // compare length against xRadius
+        builder->fFSCode.appendf("\tedgeAlpha = smoothstep(d - 0.5, d + 0.5, %s.z);\n", fsName);
+        builder->fFSCode.appendf("\t%s = ", outputColor);
+        GrGLSLModulate4f(&builder->fFSCode, inputColor, "edgeAlpha");
+        builder->fFSCode.append(";\n");
+
+    }
+
+    static inline EffectKey GenKey(const GrEffectStage& stage, const GrGLCaps&) {
+        return 0;
+    }
+
+    virtual void setData(const GrGLUniformManager& uman, const GrEffectStage& stage) SK_OVERRIDE {
+    }
+
+private:
+    typedef GrGLEffect INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+GrEllipseEdgeEffect::GrEllipseEdgeEffect() : GrEffect() {
+    this->addVertexAttribName(ELLIPSE_EDGE_ATTR0);
+}
+
+void GrEllipseEdgeEffect::getConstantColorComponents(GrColor* color, uint32_t* validFlags) const {
+    *validFlags = 0;
+}
+
+const GrBackendEffectFactory& GrEllipseEdgeEffect::getFactory() const {
+    return GrTBackendEffectFactory<GrEllipseEdgeEffect>::getInstance();
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+GR_DEFINE_EFFECT_TEST(GrEllipseEdgeEffect);
+
+GrEffectRef* GrEllipseEdgeEffect::TestCreate(SkMWCRandom* random,
+                                               GrContext* context,
+                                               GrTexture* textures[]) {
+    return GrEllipseEdgeEffect::Create();
+}