Refactoring of CPU NormalMap handling out into its own class

src/core/SkNormalSource.cpp

Index: src/core/SkNormalSource.cpp
diff --git a/src/core/SkNormalSource.cpp b/src/core/SkNormalSource.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..2f525303828229b32704ca1635311fd9610a0592
--- /dev/null
+++ b/src/core/SkNormalSource.cpp
@@ -0,0 +1,294 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkError.h"
+#include "SkErrorInternals.h"
+#include "SkLightingShader.h"
+#include "SkNormalSource.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+// Genretating vtable
+SkNormalSource::~SkNormalSource() {}
+
+///////////////////////////////////////////////////////////////////////////////
+
+class NormalMapSourceImpl : public SkNormalSource {
+public:
+    NormalMapSourceImpl(sk_sp<SkShader> mapShader, const SkVector &normRotation)
+        : fMapShader(std::move(mapShader))
+        , fNormRotation(normRotation) {}
+
+#if SK_SUPPORT_GPU
+    sk_sp<GrFragmentProcessor> asFragmentProcessor(GrContext*,
+                                                   const SkMatrix& viewM,
+                                                   const SkMatrix* localMatrix,
+                                                   SkFilterQuality,
+                                                   SkSourceGammaTreatment) const override;
+#endif
+
+    SkNormalSource::Provider* asProvider(const SkShader::ContextRec& rec,
+                                                         void* storage) const override;
+
+    size_t providerSize(const SkShader::ContextRec& rec) const override;
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(NormalMapSourceImpl)
+
+protected:
+    void flatten(SkWriteBuffer& buf) const override;
+
+    bool computeNormTotalInverse(const SkShader::ContextRec& rec, SkMatrix* normTotalInverse) const;
+
+private:
+    class Provider : public SkNormalSource::Provider {
+    public:
+        Provider(const NormalMapSourceImpl& source, SkShader::Context* fMapContext);
+
+        virtual ~Provider() override;
+
+        void fillScanLine(int x, int y, SkPoint3 output[], int count) const override;
+    private:
+        const NormalMapSourceImpl& fSource;
+        SkShader::Context* fMapContext;
+
+        typedef SkNormalSource::Provider INHERITED;
+    };
+
+    sk_sp<SkShader> fMapShader;
+    SkVector        fNormRotation;
+
+    friend class SkNormalSource;
+
+    typedef SkNormalSource INHERITED;
+};
+
+////////////////////////////////////////////////////////////////////////////
+
+#if SK_SUPPORT_GPU
+
+#include "GrCoordTransform.h"
+#include "GrInvariantOutput.h"
+#include "GrTextureParams.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "SkGr.h"
+
+class NormalMapFP : public GrFragmentProcessor {
+public:
+    NormalMapFP(sk_sp<GrFragmentProcessor> mapFP, const SkVector& normRotation)
+        : fNormRotation(normRotation) {
+        this->registerChildProcessor(mapFP);
+
+        this->initClassID<NormalMapFP>();
+    }
+
+    class GLSLNormalMapFP : public GrGLSLFragmentProcessor {
+    public:
+        GLSLNormalMapFP() {
+            fNormRotation.set(0.0f, 0.0f);
+        }
+
+        void emitCode(EmitArgs& args) override {
+
+            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+            GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
+
+            // add uniform
+            const char* xformUniName = nullptr;
+            fXformUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
+                                                   kVec2f_GrSLType, kDefault_GrSLPrecision,
+                                                   "Xform", &xformUniName);
+
+            SkString dstNormalColorName("dstNormalColor");
+            this->emitChild(0, nullptr, &dstNormalColorName, args);
+            fragBuilder->codeAppendf("vec3 normal = %s.rgb - vec3(0.5);",
+                                     dstNormalColorName.c_str());
+
+            // TODO: inverse map the light direction vectors in the vertex shader rather than
+            // transforming all the normals here!
+            fragBuilder->codeAppendf(
+                    "mat3 m = mat3(%s.x, -%s.y, 0.0, %s.y, %s.x, 0.0, 0.0, 0.0, 1.0);",
+                    xformUniName, xformUniName, xformUniName, xformUniName);
+
+            fragBuilder->codeAppend("normal = normalize(m*normal);");
+            fragBuilder->codeAppendf("%s = vec4(normal, 0);", args.fOutputColor);
+        }
+
+        static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
+                           GrProcessorKeyBuilder* b) {
+            b->add32(0x0);
+        }
+
+    protected:
+        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {
+            const NormalMapFP& normalMapFP = proc.cast<NormalMapFP>();
+
+            const SkVector& normRotation = normalMapFP.normRotation();
+            if (normRotation != fNormRotation) {
+                pdman.set2fv(fXformUni, 1, &normRotation.fX);
+                fNormRotation = normRotation;
+            }
+        }
+
+    private:
+        SkVector fNormRotation;
+        GrGLSLProgramDataManager::UniformHandle fXformUni;
+    };
+
+    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
+        GLSLNormalMapFP::GenKey(*this, caps, b);
+    }
+
+    const char* name() const override { return "NormalMapFP"; }
+
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
+        inout->setToUnknown(GrInvariantOutput::ReadInput::kWillNot_ReadInput);
+    }
+
+    const SkVector& normRotation() const { return fNormRotation; }
+
+private:
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override { return new GLSLNormalMapFP; }
+
+    bool onIsEqual(const GrFragmentProcessor& proc) const override {
+        const NormalMapFP& normalMapFP = proc.cast<NormalMapFP>();
+        return fNormRotation == normalMapFP.fNormRotation;
+    }
+
+    SkVector fNormRotation;
+};
+
+sk_sp<GrFragmentProcessor> NormalMapSourceImpl::asFragmentProcessor(
+                                                     GrContext *context,
+                                                     const SkMatrix &viewM,
+                                                     const SkMatrix *localMatrix,
+                                                     SkFilterQuality filterQuality,
+                                                     SkSourceGammaTreatment gammaTreatment) const {
+
+    sk_sp<GrFragmentProcessor> mapFP = fMapShader->asFragmentProcessor(context, viewM,
+            localMatrix, filterQuality, gammaTreatment);
+
+    return sk_make_sp<NormalMapFP>(std::move(mapFP), fNormRotation);
+}
+
+#endif // SK_SUPPORT_GPU
+
+////////////////////////////////////////////////////////////////////////////
+
+NormalMapSourceImpl::Provider::Provider(const NormalMapSourceImpl& source,
+                                        SkShader::Context* mapContext)
+    : fSource(source)
+    , fMapContext(mapContext) {
+}
+
+NormalMapSourceImpl::Provider::~Provider() {
+    fMapContext->~Context();
+}
+
+SkNormalSource::Provider* NormalMapSourceImpl::asProvider(
+        const SkShader::ContextRec &rec, void *storage) const {
+    SkMatrix normTotalInv;
+    if (!this->computeNormTotalInverse(rec, &normTotalInv)) {
+        return nullptr;
+    }
+
+    void* mapContextStorage = (char*)storage + sizeof(Provider);
+    SkShader::Context* context = fMapShader->createContext(rec, mapContextStorage);
+    if (!context) {
+        return nullptr;
+    }
+
+    return new (storage) Provider(*this, context);
+}
+
+size_t NormalMapSourceImpl::providerSize(const SkShader::ContextRec& rec) const {
+    return sizeof(Provider) + fMapShader->contextSize(rec);
+}
+
+bool NormalMapSourceImpl::computeNormTotalInverse(const SkShader::ContextRec& rec,
+                                                  SkMatrix* normTotalInverse) const {
+    SkMatrix total;
+    total.setConcat(*rec.fMatrix, fMapShader->getLocalMatrix());
+
+    const SkMatrix* m = &total;
+    if (rec.fLocalMatrix) {
+        total.setConcat(*m, *rec.fLocalMatrix);
+        m = &total;
+    }
+    return m->invert(normTotalInverse);
+}
+
+#define BUFFER_MAX 16
+void NormalMapSourceImpl::Provider::fillScanLine(int x, int y, SkPoint3 output[],
+                                                 int count) const {
+    SkPMColor tmpNormalColors[BUFFER_MAX];
+
+    do {
+        int n = SkTMin(count, BUFFER_MAX);
+
+        fMapContext->shadeSpan(x, y, tmpNormalColors, n);
+
+        for (int i = 0; i < n; i++) {
+            SkPoint3 tempNorm;
+
+            tempNorm.set(SkIntToScalar(SkGetPackedR32(tmpNormalColors[i])) - 127.0f,
+                         SkIntToScalar(SkGetPackedG32(tmpNormalColors[i])) - 127.0f,
+                         SkIntToScalar(SkGetPackedB32(tmpNormalColors[i])) - 127.0f);
+            tempNorm.normalize();
+
+            output[i].fX = fSource.fNormRotation.fX * tempNorm.fX +
+                           fSource.fNormRotation.fY * tempNorm.fY;
+            output[i].fY = -fSource.fNormRotation.fY * tempNorm.fX +
+                           fSource.fNormRotation.fX * tempNorm.fY;
+            output[i].fZ = tempNorm.fZ;
+        }
+
+        output += n;
+        x += n;
+        count -= n;
+    } while (count > 0);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkFlattenable> NormalMapSourceImpl::CreateProc(SkReadBuffer& buf) {
+
+    sk_sp<SkShader> mapShader = buf.readFlattenable<SkShader>();
+
+    SkVector normRotation = {1,0};
+    if (!buf.isVersionLT(SkReadBuffer::kLightingShaderWritesInvNormRotation)) {
+        normRotation = buf.readPoint();
+    }
+
+    return sk_make_sp<NormalMapSourceImpl>(std::move(mapShader), normRotation);
+}
+
+void NormalMapSourceImpl::flatten(SkWriteBuffer& buf) const {
+    this->INHERITED::flatten(buf);
+
+    buf.writeFlattenable(fMapShader.get());
+    buf.writePoint(fNormRotation);
+}
+
+////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkNormalSource> SkNormalSource::MakeFromNormalMap(sk_sp<SkShader> map,
+                                                        const SkVector &normRotation) {
+    SkASSERT(SkScalarNearlyEqual(normRotation.lengthSqd(), SK_Scalar1));
+    if (!map) {
+        return nullptr;
+    }
+
+    return sk_make_sp<NormalMapSourceImpl>(std::move(map), normRotation);
+}
+
+////////////////////////////////////////////////////////////////////////////
+
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkNormalSource)
+    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(NormalMapSourceImpl)
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
+
+////////////////////////////////////////////////////////////////////////////