Restore SkLightingShader and associated classes

This reverts https://skia-review.googlesource.com/c/skia/+/31140 (Remove SkLightingShader and associated classes) and updates the classes to ToT

Change-Id: I3b1df1704cca8907aa00f081a7e93339b65ad4fa
Reviewed-on: https://skia-review.googlesource.com/141545
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>

11 files changed, 1189 insertions, 0 deletions

diff --git a/src/core/SkLights.cpp b/src/core/SkLights.cpp
new file mode 100644
index 0000000000..e6c4796506
--- /dev/null
+++ b/src/core/SkLights.cpp
@@ -0,0 +1,91 @@
+
+/*
+ * 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 "SkColorSpaceXformer.h"
+#include "SkLights.h"
+#include "SkReadBuffer.h"
+
+sk_sp<SkLights> SkLights::MakeFromBuffer(SkReadBuffer& buf) {
+    Builder builder;
+
+    SkColor3f ambColor;
+    if (!buf.readScalarArray(&ambColor.fX, 3)) {
+        return nullptr;
+    }
+
+    builder.setAmbientLightColor(ambColor);
+
+    int numLights = buf.readInt();
+
+    for (int l = 0; l < numLights; ++l) {
+        bool isPoint = buf.readBool();
+
+        SkColor3f color;
+        if (!buf.readScalarArray(&color.fX, 3)) {
+            return nullptr;
+        }
+
+        SkVector3 dirOrPos;
+        if (!buf.readScalarArray(&dirOrPos.fX, 3)) {
+            return nullptr;
+        }
+
+        if (isPoint) {
+            SkScalar intensity;
+            intensity = buf.readScalar();
+            Light light = Light::MakePoint(color, dirOrPos, intensity);
+            builder.add(light);
+        } else {
+            Light light = Light::MakeDirectional(color, dirOrPos);
+            builder.add(light);
+        }
+    }
+
+    return builder.finish();
+}
+
+static SkColor3f xform_color(const SkColor3f& color, SkColorSpaceXformer* xformer) {
+    SkColor origColor = SkColorSetARGB(0xFF,
+                                       SkScalarRoundToInt(color.fX),
+                                       SkScalarRoundToInt(color.fY),
+                                       SkScalarRoundToInt(color.fZ));
+    SkColor xformedColor = xformer->apply(origColor);
+    return SkColor3f::Make(SkIntToScalar(SkGetPackedR32(xformedColor)),
+                           SkIntToScalar(SkGetPackedG32(xformedColor)),
+                           SkIntToScalar(SkGetPackedB32(xformedColor)));
+}
+
+sk_sp<SkLights> SkLights::makeColorSpace(SkColorSpaceXformer* xformer) const {
+    SkLights::Builder builder;
+    for (int i = 0; i < this->numLights(); i++) {
+        Light light(fLights[i].type(), xform_color(fLights[i].color(), xformer),
+                    fLights[i].fDirOrPos, fLights[i].fIntensity);
+        builder.add(light);
+    }
+    builder.setAmbientLightColor(xform_color(fAmbientLightColor, xformer));
+    return builder.finish();
+}
+
+void SkLights::flatten(SkWriteBuffer& buf) const {
+    buf.writeScalarArray(&this->ambientLightColor().fX, 3);
+
+    buf.writeInt(this->numLights());
+    for (int l = 0; l < this->numLights(); ++l) {
+        const Light& light = this->light(l);
+
+        bool isPoint = Light::kPoint_LightType == light.type();
+
+        buf.writeBool(isPoint);
+        buf.writeScalarArray(&light.color().fX, 3);
+        buf.writeScalarArray(&light.dir().fX, 3);
+
+        if (isPoint) {
+            buf.writeScalar(light.intensity());
+        }
+    }
+}
diff --git a/src/core/SkNormalFlatSource.cpp b/src/core/SkNormalFlatSource.cpp
new file mode 100644
index 0000000000..f174e185c0
--- /dev/null
+++ b/src/core/SkNormalFlatSource.cpp
@@ -0,0 +1,100 @@
+/*
+ * 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 "SkNormalFlatSource.h"
+
+#include "SkArenaAlloc.h"
+#include "SkNormalSource.h"
+#include "SkPoint3.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+#if SK_SUPPORT_GPU
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+
+class NormalFlatFP : public GrFragmentProcessor {
+public:
+    static std::unique_ptr<GrFragmentProcessor> Make() {
+        return std::unique_ptr<GrFragmentProcessor>(new NormalFlatFP());
+    }
+
+    const char* name() const override { return "NormalFlatFP"; }
+
+    std::unique_ptr<GrFragmentProcessor> clone() const override { return Make(); }
+
+private:
+    class GLSLNormalFlatFP : public GrGLSLFragmentProcessor {
+    public:
+        GLSLNormalFlatFP() {}
+
+        void emitCode(EmitArgs& args) override {
+            GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
+
+            fragBuilder->codeAppendf("%s = float4(0, 0, 1, 0);", args.fOutputColor);
+        }
+
+    private:
+        void onSetData(const GrGLSLProgramDataManager&, const GrFragmentProcessor&) override {}
+    };
+
+    NormalFlatFP()
+            : INHERITED(kFlatNormalsFP_ClassID, kConstantOutputForConstantInput_OptimizationFlag) {
+    }
+
+    void onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override {}
+
+    GrColor4f constantOutputForConstantInput(GrColor4f) const override {
+        return GrColor4f(0, 0, 1, 0);
+    }
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override { return new GLSLNormalFlatFP; }
+
+    bool onIsEqual(const GrFragmentProcessor&) const override { return true; }
+
+    typedef GrFragmentProcessor INHERITED;
+};
+
+std::unique_ptr<GrFragmentProcessor> SkNormalFlatSourceImpl::asFragmentProcessor(
+                                                                            const GrFPArgs&) const {
+    return NormalFlatFP::Make();
+}
+
+#endif // SK_SUPPORT_GPU
+
+////////////////////////////////////////////////////////////////////////////
+
+SkNormalFlatSourceImpl::Provider::Provider() {}
+
+SkNormalFlatSourceImpl::Provider::~Provider() {}
+
+SkNormalSource::Provider* SkNormalFlatSourceImpl::asProvider(const SkShaderBase::ContextRec &rec,
+                                                             SkArenaAlloc *alloc) const {
+    return alloc->make<Provider>();
+}
+
+void SkNormalFlatSourceImpl::Provider::fillScanLine(int x, int y, SkPoint3 output[],
+                                                    int count) const {
+    for (int i = 0; i < count; i++) {
+        output[i] = {0.0f, 0.0f, 1.0f};
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkFlattenable> SkNormalFlatSourceImpl::CreateProc(SkReadBuffer& buf) {
+    return sk_make_sp<SkNormalFlatSourceImpl>();
+}
+
+void SkNormalFlatSourceImpl::flatten(SkWriteBuffer& buf) const {
+    this->INHERITED::flatten(buf);
+}
+
+////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkNormalSource> SkNormalSource::MakeFlat() {
+    return sk_make_sp<SkNormalFlatSourceImpl>();
+}
diff --git a/src/core/SkNormalFlatSource.h b/src/core/SkNormalFlatSource.h
new file mode 100644
index 0000000000..9303ba10af
--- /dev/null
+++ b/src/core/SkNormalFlatSource.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkNormalFlatSource_DEFINED
+#define SkNormalFlatSource_DEFINED
+
+#include "SkNormalSource.h"
+
+class SK_API SkNormalFlatSourceImpl : public SkNormalSource {
+public:
+    SkNormalFlatSourceImpl(){}
+
+#if SK_SUPPORT_GPU
+    std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs& args) const override;
+#endif
+
+    SkNormalSource::Provider* asProvider(const SkShaderBase::ContextRec& rec,
+                                         SkArenaAlloc* alloc) const override;
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkNormalFlatSourceImpl)
+
+protected:
+    void flatten(SkWriteBuffer& buf) const override;
+
+private:
+    class Provider : public SkNormalSource::Provider {
+    public:
+        Provider();
+
+        ~Provider() override;
+
+        void fillScanLine(int x, int y, SkPoint3 output[], int count) const override;
+
+    private:
+        typedef SkNormalSource::Provider INHERITED;
+    };
+
+    friend class SkNormalSource;
+
+    typedef SkNormalSource INHERITED;
+};
+
+#endif
diff --git a/src/core/SkNormalMapSource.cpp b/src/core/SkNormalMapSource.cpp
new file mode 100644
index 0000000000..1b88366690
--- /dev/null
+++ b/src/core/SkNormalMapSource.cpp
@@ -0,0 +1,253 @@
+/*
+ * 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 "SkNormalMapSource.h"
+
+#include "SkArenaAlloc.h"
+#include "SkLightingShader.h"
+#include "SkMatrix.h"
+#include "SkNormalSource.h"
+#include "SkPM4f.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+#if SK_SUPPORT_GPU
+#include "GrCoordTransform.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "SkGr.h"
+
+class NormalMapFP : public GrFragmentProcessor {
+public:
+    static std::unique_ptr<GrFragmentProcessor> Make(std::unique_ptr<GrFragmentProcessor> mapFP,
+                                                     const SkMatrix& invCTM) {
+        return std::unique_ptr<GrFragmentProcessor>(new NormalMapFP(std::move(mapFP), invCTM));
+    }
+
+    const char* name() const override { return "NormalMapFP"; }
+
+    const SkMatrix& invCTM() const { return fInvCTM; }
+
+    std::unique_ptr<GrFragmentProcessor> clone() const override {
+        return Make(this->childProcessor(0).clone(), fInvCTM);
+    }
+
+private:
+    class GLSLNormalMapFP : public GrGLSLFragmentProcessor {
+    public:
+        GLSLNormalMapFP() : fColumnMajorInvCTM22{0.0f} {}
+
+        void emitCode(EmitArgs& args) override {
+            GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
+            GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
+
+            // add uniform
+            const char* xformUniName = nullptr;
+            fXformUni = uniformHandler->addUniform(kFragment_GrShaderFlag, kFloat2x2_GrSLType,
+                                                   kDefault_GrSLPrecision, "Xform", &xformUniName);
+
+            SkString dstNormalColorName("dstNormalColor");
+            this->emitChild(0, &dstNormalColorName, args);
+            fragBuilder->codeAppendf("float3 normal = normalize(%s.rgb - float3(0.5));",
+                                     dstNormalColorName.c_str());
+
+            // If there's no x & y components, return (0, 0, +/- 1) instead to avoid division by 0
+            fragBuilder->codeAppend( "if (abs(normal.z) > 0.999) {");
+            fragBuilder->codeAppendf("    %s = normalize(float4(0.0, 0.0, normal.z, 0.0));",
+                    args.fOutputColor);
+            // Else, Normalizing the transformed X and Y, while keeping constant both Z and the
+            // vector's angle in the XY plane. This maintains the "slope" for the surface while
+            // appropriately rotating the normal regardless of any anisotropic scaling that occurs.
+            // Here, we call 'scaling factor' the number that must divide the transformed X and Y so
+            // that the normal's length remains equal to 1.
+            fragBuilder->codeAppend( "} else {");
+            fragBuilder->codeAppendf("    float2 transformed = %s * normal.xy;",
+                    xformUniName);
+            fragBuilder->codeAppend( "    float scalingFactorSquared = "
+                                                 "( (transformed.x * transformed.x) "
+                                                   "+ (transformed.y * transformed.y) )"
+                                                 "/(1.0 - (normal.z * normal.z));");
+            fragBuilder->codeAppendf("    %s = float4(transformed*inversesqrt(scalingFactorSquared),"
+                                                   "normal.z, 0.0);",
+                    args.fOutputColor);
+            fragBuilder->codeAppend( "}");
+        }
+
+        static void GenKey(const GrProcessor&, const GrShaderCaps&, GrProcessorKeyBuilder* b) {
+            b->add32(0x0);
+        }
+
+    private:
+        void onSetData(const GrGLSLProgramDataManager& pdman,
+                       const GrFragmentProcessor& proc) override {
+            const NormalMapFP& normalMapFP = proc.cast<NormalMapFP>();
+
+            const SkMatrix& invCTM = normalMapFP.invCTM();
+            fColumnMajorInvCTM22[0] = invCTM.get(SkMatrix::kMScaleX);
+            fColumnMajorInvCTM22[1] = invCTM.get(SkMatrix::kMSkewY);
+            fColumnMajorInvCTM22[2] = invCTM.get(SkMatrix::kMSkewX);
+            fColumnMajorInvCTM22[3] = invCTM.get(SkMatrix::kMScaleY);
+            pdman.setMatrix2f(fXformUni, fColumnMajorInvCTM22);
+        }
+
+    private:
+        // Upper-right 2x2 corner of the inverse of the CTM in column-major form
+        float fColumnMajorInvCTM22[4];
+        GrGLSLProgramDataManager::UniformHandle fXformUni;
+    };
+
+    void onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override {
+        GLSLNormalMapFP::GenKey(*this, caps, b);
+    }
+    NormalMapFP(std::unique_ptr<GrFragmentProcessor> mapFP, const SkMatrix& invCTM)
+            : INHERITED(kMappedNormalsFP_ClassID, kNone_OptimizationFlags)
+            , fInvCTM(invCTM) {
+        this->registerChildProcessor(std::move(mapFP));
+    }
+
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override { return new GLSLNormalMapFP; }
+
+    bool onIsEqual(const GrFragmentProcessor& proc) const override {
+        const NormalMapFP& normalMapFP = proc.cast<NormalMapFP>();
+        return fInvCTM == normalMapFP.fInvCTM;
+    }
+
+    SkMatrix fInvCTM;
+
+    typedef GrFragmentProcessor INHERITED;
+};
+
+std::unique_ptr<GrFragmentProcessor> SkNormalMapSourceImpl::asFragmentProcessor(
+                                                                       const GrFPArgs& args) const {
+    std::unique_ptr<GrFragmentProcessor> mapFP = as_SB(fMapShader)->asFragmentProcessor(args);
+    if (!mapFP) {
+        return nullptr;
+    }
+
+    return NormalMapFP::Make(std::move(mapFP), fInvCTM);
+}
+
+#endif // SK_SUPPORT_GPU
+
+////////////////////////////////////////////////////////////////////////////
+
+SkNormalMapSourceImpl::Provider::Provider(const SkNormalMapSourceImpl& source,
+                                          SkShaderBase::Context* mapContext)
+    : fSource(source)
+    , fMapContext(mapContext) {}
+
+SkNormalSource::Provider* SkNormalMapSourceImpl::asProvider(const SkShaderBase::ContextRec &rec,
+                                                            SkArenaAlloc* alloc) const {
+    SkMatrix normTotalInv;
+    if (!this->computeNormTotalInverse(rec, &normTotalInv)) {
+        return nullptr;
+    }
+
+    // Overriding paint's alpha because we need the normal map's RGB channels to be unpremul'd
+    SkPaint overridePaint {*(rec.fPaint)};
+    overridePaint.setAlpha(0xFF);
+    SkShaderBase::ContextRec overrideRec(overridePaint, *(rec.fMatrix), rec.fLocalMatrix,
+                                         rec.fPreferredDstType, rec.fDstColorSpace);
+
+    auto* context = as_SB(fMapShader)->makeContext(overrideRec, alloc);
+    if (!context) {
+        return nullptr;
+    }
+
+    return alloc->make<Provider>(*this, context);
+}
+
+bool SkNormalMapSourceImpl::computeNormTotalInverse(const SkShaderBase::ContextRec& rec,
+                                                    SkMatrix* normTotalInverse) const {
+    SkMatrix total = SkMatrix::Concat(*rec.fMatrix, fMapShader->getLocalMatrix());
+    if (rec.fLocalMatrix) {
+        total.preConcat(*rec.fLocalMatrix);
+    }
+
+    return total.invert(normTotalInverse);
+}
+
+#define BUFFER_MAX 16
+void SkNormalMapSourceImpl::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();
+
+
+            if (!SkScalarNearlyEqual(SkScalarAbs(tempNorm.fZ), 1.0f)) {
+                SkVector transformed = fSource.fInvCTM.mapVector(tempNorm.fX, tempNorm.fY);
+
+                // Normalizing the transformed X and Y, while keeping constant both Z and the
+                // vector's angle in the XY plane. This maintains the "slope" for the surface while
+                // appropriately rotating the normal for any anisotropic scaling that occurs.
+                // Here, we call scaling factor the number that must divide the transformed X and Y
+                // so that the normal's length remains equal to 1.
+                SkScalar scalingFactorSquared =
+                        (SkScalarSquare(transformed.fX) + SkScalarSquare(transformed.fY))
+                        / (1.0f - SkScalarSquare(tempNorm.fZ));
+                SkScalar invScalingFactor = SkScalarInvert(SkScalarSqrt(scalingFactorSquared));
+
+                output[i].fX = transformed.fX * invScalingFactor;
+                output[i].fY = transformed.fY * invScalingFactor;
+                output[i].fZ = tempNorm.fZ;
+            } else {
+                output[i] = {0.0f, 0.0f, tempNorm.fZ};
+                output[i].normalize();
+            }
+
+            SkASSERT(SkScalarNearlyEqual(output[i].length(), 1.0f));
+        }
+
+        output += n;
+        x += n;
+        count -= n;
+    } while (count > 0);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkFlattenable> SkNormalMapSourceImpl::CreateProc(SkReadBuffer& buf) {
+
+    sk_sp<SkShader> mapShader = buf.readFlattenable<SkShaderBase>();
+
+    SkMatrix invCTM;
+    buf.readMatrix(&invCTM);
+
+    return sk_make_sp<SkNormalMapSourceImpl>(std::move(mapShader), invCTM);
+}
+
+void SkNormalMapSourceImpl::flatten(SkWriteBuffer& buf) const {
+    this->INHERITED::flatten(buf);
+
+    buf.writeFlattenable(fMapShader.get());
+    buf.writeMatrix(fInvCTM);
+}
+
+////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkNormalSource> SkNormalSource::MakeFromNormalMap(sk_sp<SkShader> map, const SkMatrix& ctm) {
+    SkMatrix invCTM;
+
+    if (!ctm.invert(&invCTM) || !map) {
+        return nullptr;
+    }
+
+    return sk_make_sp<SkNormalMapSourceImpl>(std::move(map), invCTM);
+}
diff --git a/src/core/SkNormalMapSource.h b/src/core/SkNormalMapSource.h
new file mode 100644
index 0000000000..dfedfd35d5
--- /dev/null
+++ b/src/core/SkNormalMapSource.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkNormalMapSource_DEFINED
+#define SkNormalMapSource_DEFINED
+
+#include "SkNormalSource.h"
+
+class SkNormalMapSourceImpl : public SkNormalSource {
+public:
+    SkNormalMapSourceImpl(sk_sp<SkShader> mapShader, const SkMatrix& invCTM)
+            : fMapShader(std::move(mapShader))
+            , fInvCTM(invCTM) {}
+
+#if SK_SUPPORT_GPU
+    std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs& args) const override;
+#endif
+
+    SkNormalSource::Provider* asProvider(const SkShaderBase::ContextRec& rec,
+                                         SkArenaAlloc* alloc) const override;
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkNormalMapSourceImpl)
+
+protected:
+    void flatten(SkWriteBuffer& buf) const override;
+
+    bool computeNormTotalInverse(const SkShaderBase::ContextRec& rec,
+                                 SkMatrix* normTotalInverse) const;
+
+private:
+    class Provider : public SkNormalSource::Provider {
+    public:
+        Provider(const SkNormalMapSourceImpl& source, SkShaderBase::Context* mapContext);
+
+        void fillScanLine(int x, int y, SkPoint3 output[], int count) const override;
+
+    private:
+        const SkNormalMapSourceImpl& fSource;
+        SkShaderBase::Context*       fMapContext;
+
+        typedef SkNormalSource::Provider INHERITED;
+    };
+
+    sk_sp<SkShader> fMapShader;
+    SkMatrix        fInvCTM; // Inverse of the canvas total matrix, used for rotating normals.
+
+    friend class SkNormalSource;
+
+    typedef SkNormalSource INHERITED;
+};
+
+#endif
+
diff --git a/src/core/SkNormalSource.cpp b/src/core/SkNormalSource.cpp
new file mode 100644
index 0000000000..ad1f5a3e40
--- /dev/null
+++ b/src/core/SkNormalSource.cpp
@@ -0,0 +1,22 @@
+/*
+ * 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 "SkNormalFlatSource.h"
+#include "SkNormalMapSource.h"
+#include "SkNormalSource.h"
+
+// Generating vtable
+SkNormalSource::~SkNormalSource() {}
+
+////////////////////////////////////////////////////////////////////////////
+
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkNormalSource)
+SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkNormalMapSourceImpl)
+SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkNormalFlatSourceImpl)
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
+
+////////////////////////////////////////////////////////////////////////////
diff --git a/src/core/SkNormalSource.h b/src/core/SkNormalSource.h
new file mode 100644
index 0000000000..7339890bef
--- /dev/null
+++ b/src/core/SkNormalSource.h
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkNormalSource_DEFINED
+#define SkNormalSource_DEFINED
+
+#include "SkFlattenable.h"
+#include "SkShaderBase.h"
+
+class SkMatrix;
+struct SkPoint3;
+
+#if SK_SUPPORT_GPU
+class GrFragmentProcessor;
+#endif
+
+/** Abstract class that generates or reads in normals for use by SkLightingShader.
+*/
+class SK_API SkNormalSource : public SkFlattenable {
+public:
+    virtual ~SkNormalSource() override;
+
+#if SK_SUPPORT_GPU
+    /** Returns a fragment processor that takes no input and outputs a normal (already rotated)
+        as its output color. To be used as a child fragment processor.
+    */
+    virtual std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs&) const = 0;
+#endif
+
+    class Provider {
+    public:
+        virtual ~Provider() {}
+
+        /** Called for each span of the object being drawn on the CPU. Your subclass should set
+            the appropriate normals that correspond to the specified device coordinates.
+        */
+        virtual void fillScanLine(int x, int y, SkPoint3 output[], int count) const = 0;
+    };
+
+    /** Returns an instance of 'Provider' that provides normals for the CPU pipeline. The
+        necessary data will be initialized in place at 'storage'.
+    */
+    virtual Provider* asProvider(const SkShaderBase::ContextRec&, SkArenaAlloc*) const = 0;
+
+    /** Returns a normal source that provides normals sourced from the the normal map argument.
+
+        @param  map  a shader that outputs the normal map
+        @param  ctm  the current canvas' total matrix, used to rotate normals when necessary.
+
+        nullptr will be returned if 'map' is null
+
+        The normal map is currently assumed to be an 8888 image where the normal at a texel
+        is retrieved by:
+            N.x = R-127;
+            N.y = G-127;
+            N.z = B-127;
+            N.normalize();
+        The +Z axis is thus encoded in RGB as (127, 127, 255) while the -Z axis is
+        (127, 127, 0).
+    */
+    static sk_sp<SkNormalSource> MakeFromNormalMap(sk_sp<SkShader> map, const SkMatrix& ctm);
+
+    /** Returns a normal source that provides straight-up normals only <0, 0, 1>.
+    */
+    static sk_sp<SkNormalSource> MakeFlat();
+
+    SK_DEFINE_FLATTENABLE_TYPE(SkNormalSource)
+    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
+};
+
+#endif
diff --git a/src/gpu/GrProcessor.h b/src/gpu/GrProcessor.h
index 696ed0a96d..038ce16717 100644
--- a/src/gpu/GrProcessor.h
+++ b/src/gpu/GrProcessor.h
@@ -153,6 +153,9 @@ public:
         kSwizzleFragmentProcessor_ClassID,
         kTestFP_ClassID,
         kTextureGeometryProcessor_ClassID,
+        kFlatNormalsFP_ClassID,
+        kMappedNormalsFP_ClassID,
+        kLightingFP_ClassID,
     };
 
     virtual ~GrProcessor() = default;
diff --git a/src/ports/SkGlobalInitialization_default.cpp b/src/ports/SkGlobalInitialization_default.cpp
index 22aabc2314..ecb9ccb1ca 100644
--- a/src/ports/SkGlobalInitialization_default.cpp
+++ b/src/ports/SkGlobalInitialization_default.cpp
@@ -15,7 +15,9 @@
 #include "SkGradientShader.h"
 #include "SkHighContrastFilter.h"
 #include "SkLayerDrawLooper.h"
+#include "SkLightingShader.h"
 #include "SkLumaColorFilter.h"
+#include "SkNormalSource.h"
 #include "SkOverdrawColorFilter.h"
 #include "SkPerlinNoiseShader.h"
 #include "SkShaderMaskFilter.h"
@@ -51,6 +53,8 @@ void SkFlattenable::PrivateInitializer::InitEffects() {
     // Shader
     SkPerlinNoiseShader::InitializeFlattenables();
     SkGradientShader::InitializeFlattenables();
+    SkLightingShader::InitializeFlattenables();
+    SkNormalSource::InitializeFlattenables();
 
     // PathEffect
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkCornerPathEffect)
diff --git a/src/shaders/SkLightingShader.cpp b/src/shaders/SkLightingShader.cpp
new file mode 100644
index 0000000000..6fa754a6fa
--- /dev/null
+++ b/src/shaders/SkLightingShader.cpp
@@ -0,0 +1,497 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkArenaAlloc.h"
+#include "SkBitmapProcShader.h"
+#include "SkBitmapProcState.h"
+#include "SkColor.h"
+#include "SkColorSpaceXformer.h"
+#include "SkEmptyShader.h"
+#include "SkLightingShader.h"
+#include "SkMathPriv.h"
+#include "SkNormalSource.h"
+#include "SkPoint3.h"
+#include "SkReadBuffer.h"
+#include "SkShaderBase.h"
+#include "SkUnPreMultiply.h"
+#include "SkWriteBuffer.h"
+
+////////////////////////////////////////////////////////////////////////////
+
+/*
+   SkLightingShader TODOs:
+        support different light types
+        support multiple lights
+        fix non-opaque diffuse textures
+
+    To Test:
+        A8 diffuse textures
+        down & upsampled draws
+*/
+
+
+
+/** \class SkLightingShaderImpl
+    This subclass of shader applies lighting.
+*/
+class SkLightingShaderImpl : public SkShaderBase {
+public:
+    /** Create a new lighting shader that uses the provided normal map and
+        lights to light the diffuse bitmap.
+        @param diffuseShader     the shader that provides the diffuse colors
+        @param normalSource      the source of normals for lighting computation
+        @param lights            the lights applied to the geometry
+    */
+    SkLightingShaderImpl(sk_sp<SkShader> diffuseShader,
+                         sk_sp<SkNormalSource> normalSource,
+                         sk_sp<SkLights> lights)
+        : fDiffuseShader(std::move(diffuseShader))
+        , fNormalSource(std::move(normalSource))
+        , fLights(std::move(lights)) {}
+
+    bool isOpaque() const override;
+
+#if SK_SUPPORT_GPU
+    std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs&) const override;
+#endif
+
+    class LightingShaderContext : public Context {
+    public:
+        // The context takes ownership of the context and provider. It will call their destructors
+        // and then indirectly free their memory by calling free() on heapAllocated
+        LightingShaderContext(const SkLightingShaderImpl&, const ContextRec&,
+                              SkShaderBase::Context* diffuseContext, SkNormalSource::Provider*,
+                              void* heapAllocated);
+
+        void shadeSpan(int x, int y, SkPMColor[], int count) override;
+
+        uint32_t getFlags() const override { return fFlags; }
+
+    private:
+        SkShaderBase::Context*    fDiffuseContext;
+        SkNormalSource::Provider* fNormalProvider;
+        SkColor                   fPaintColor;
+        uint32_t                  fFlags;
+
+        typedef Context INHERITED;
+    };
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLightingShaderImpl)
+
+protected:
+    void flatten(SkWriteBuffer&) const override;
+    Context* onMakeContext(const ContextRec&, SkArenaAlloc*) const override;
+    sk_sp<SkShader> onMakeColorSpace(SkColorSpaceXformer* xformer) const override;
+
+private:
+    sk_sp<SkShader> fDiffuseShader;
+    sk_sp<SkNormalSource> fNormalSource;
+    sk_sp<SkLights> fLights;
+
+    friend class SkLightingShader;
+
+    typedef SkShaderBase INHERITED;
+};
+
+////////////////////////////////////////////////////////////////////////////
+
+#if SK_SUPPORT_GPU
+
+#include "GrCoordTransform.h"
+#include "GrFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "glsl/GrGLSLProgramDataManager.h"
+#include "glsl/GrGLSLUniformHandler.h"
+#include "SkGr.h"
+
+// This FP expects a premul'd color input for its diffuse color. Premul'ing of the paint's color is
+// handled by the asFragmentProcessor() factory, but shaders providing diffuse color must output it
+// premul'd.
+class LightingFP : public GrFragmentProcessor {
+public:
+    static std::unique_ptr<GrFragmentProcessor> Make(std::unique_ptr<GrFragmentProcessor> normalFP,
+                                                     sk_sp<SkLights> lights) {
+        return std::unique_ptr<GrFragmentProcessor>(new LightingFP(std::move(normalFP),
+                                                                   std::move(lights)));
+    }
+
+    const char* name() const override { return "LightingFP"; }
+
+    std::unique_ptr<GrFragmentProcessor> clone() const override {
+        return std::unique_ptr<GrFragmentProcessor>(new LightingFP(*this));
+    }
+
+    const SkTArray<SkLights::Light>& directionalLights() const { return fDirectionalLights; }
+    const SkColor3f& ambientColor() const { return fAmbientColor; }
+
+private:
+    class GLSLLightingFP : public GrGLSLFragmentProcessor {
+    public:
+        GLSLLightingFP() {
+            fAmbientColor.fX = 0.0f;
+        }
+
+        void emitCode(EmitArgs& args) override {
+
+            GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+            GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
+            const LightingFP& lightingFP = args.fFp.cast<LightingFP>();
+
+            const char *lightDirsUniName = nullptr;
+            const char *lightColorsUniName = nullptr;
+            if (lightingFP.fDirectionalLights.count() != 0) {
+                fLightDirsUni = uniformHandler->addUniformArray(
+                        kFragment_GrShaderFlag,
+                        kFloat3_GrSLType,
+                        kDefault_GrSLPrecision,
+                        "LightDir",
+                        lightingFP.fDirectionalLights.count(),
+                        &lightDirsUniName);
+                fLightColorsUni = uniformHandler->addUniformArray(
+                        kFragment_GrShaderFlag,
+                        kFloat3_GrSLType,
+                        kDefault_GrSLPrecision,
+                        "LightColor",
+                        lightingFP.fDirectionalLights.count(),
+                        &lightColorsUniName);
+            }
+
+            const char* ambientColorUniName = nullptr;
+            fAmbientColorUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
+                                                          kFloat3_GrSLType, kDefault_GrSLPrecision,
+                                                          "AmbientColor", &ambientColorUniName);
+
+            fragBuilder->codeAppendf("float4 diffuseColor = %s;", args.fInputColor);
+
+            SkString dstNormalName("dstNormal");
+            this->emitChild(0, &dstNormalName, args);
+
+            fragBuilder->codeAppendf("float3 normal = %s.xyz;", dstNormalName.c_str());
+
+            fragBuilder->codeAppend( "float3 result = float3(0.0);");
+
+            // diffuse light
+            if (lightingFP.fDirectionalLights.count() != 0) {
+                fragBuilder->codeAppendf("for (int i = 0; i < %d; i++) {",
+                                         lightingFP.fDirectionalLights.count());
+                // TODO: modulate the contribution from each light based on the shadow map
+                fragBuilder->codeAppendf("    float NdotL = clamp(dot(normal, %s[i]), 0.0, 1.0);",
+                                         lightDirsUniName);
+                fragBuilder->codeAppendf("    result += %s[i]*diffuseColor.rgb*NdotL;",
+                                         lightColorsUniName);
+                fragBuilder->codeAppend("}");
+            }
+
+            // ambient light
+            fragBuilder->codeAppendf("result += %s * diffuseColor.rgb;", ambientColorUniName);
+
+            // Clamping to alpha (equivalent to an unpremul'd clamp to 1.0)
+            fragBuilder->codeAppendf("%s = float4(clamp(result.rgb, 0.0, diffuseColor.a), "
+                                               "diffuseColor.a);", args.fOutputColor);
+        }
+
+        static void GenKey(const GrProcessor& proc, const GrShaderCaps&, GrProcessorKeyBuilder* b) {
+            const LightingFP& lightingFP = proc.cast<LightingFP>();
+            b->add32(lightingFP.fDirectionalLights.count());
+        }
+
+    protected:
+        void onSetData(const GrGLSLProgramDataManager& pdman,
+                       const GrFragmentProcessor& proc) override {
+            const LightingFP& lightingFP = proc.cast<LightingFP>();
+
+            const SkTArray<SkLights::Light>& directionalLights = lightingFP.directionalLights();
+            if (directionalLights != fDirectionalLights) {
+                SkTArray<SkColor3f> lightDirs(directionalLights.count());
+                SkTArray<SkVector3> lightColors(directionalLights.count());
+                for (const SkLights::Light& light : directionalLights) {
+                    lightDirs.push_back(light.dir());
+                    lightColors.push_back(light.color());
+                }
+
+                pdman.set3fv(fLightDirsUni, directionalLights.count(), &(lightDirs[0].fX));
+                pdman.set3fv(fLightColorsUni, directionalLights.count(), &(lightColors[0].fX));
+
+                fDirectionalLights = directionalLights;
+            }
+
+            const SkColor3f& ambientColor = lightingFP.ambientColor();
+            if (ambientColor != fAmbientColor) {
+                pdman.set3fv(fAmbientColorUni, 1, &ambientColor.fX);
+                fAmbientColor = ambientColor;
+            }
+        }
+
+    private:
+        SkTArray<SkLights::Light> fDirectionalLights;
+        GrGLSLProgramDataManager::UniformHandle fLightDirsUni;
+        GrGLSLProgramDataManager::UniformHandle fLightColorsUni;
+
+        SkColor3f fAmbientColor;
+        GrGLSLProgramDataManager::UniformHandle fAmbientColorUni;
+    };
+
+    void onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override {
+        GLSLLightingFP::GenKey(*this, caps, b);
+    }
+
+    LightingFP(std::unique_ptr<GrFragmentProcessor> normalFP, sk_sp<SkLights> lights)
+            : INHERITED(kLightingFP_ClassID, kPreservesOpaqueInput_OptimizationFlag) {
+        // fuse all ambient lights into a single one
+        fAmbientColor = lights->ambientLightColor();
+        for (int i = 0; i < lights->numLights(); ++i) {
+            if (SkLights::Light::kDirectional_LightType == lights->light(i).type()) {
+                fDirectionalLights.push_back(lights->light(i));
+                // TODO get the handle to the shadow map if there is one
+            } else {
+                SkDEBUGFAIL("Unimplemented Light Type passed to LightingFP");
+            }
+        }
+
+        this->registerChildProcessor(std::move(normalFP));
+    }
+
+    LightingFP(const LightingFP& that)
+            : INHERITED(kLightingFP_ClassID, kPreservesOpaqueInput_OptimizationFlag)
+            , fDirectionalLights(that.fDirectionalLights)
+            , fAmbientColor(that.fAmbientColor) {
+        this->registerChildProcessor(that.childProcessor(0).clone());
+    }
+
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override { return new GLSLLightingFP; }
+
+    bool onIsEqual(const GrFragmentProcessor& proc) const override {
+        const LightingFP& lightingFP = proc.cast<LightingFP>();
+        return fDirectionalLights == lightingFP.fDirectionalLights &&
+               fAmbientColor == lightingFP.fAmbientColor;
+    }
+
+    SkTArray<SkLights::Light> fDirectionalLights;
+    SkColor3f                 fAmbientColor;
+
+    typedef GrFragmentProcessor INHERITED;
+};
+
+////////////////////////////////////////////////////////////////////////////
+
+std::unique_ptr<GrFragmentProcessor> SkLightingShaderImpl::asFragmentProcessor(const GrFPArgs& args) const {
+    std::unique_ptr<GrFragmentProcessor> normalFP(fNormalSource->asFragmentProcessor(args));
+    if (!normalFP) {
+        return nullptr;
+    }
+
+    if (fDiffuseShader) {
+        std::unique_ptr<GrFragmentProcessor> fpPipeline[] = {
+            as_SB(fDiffuseShader)->asFragmentProcessor(args),
+            LightingFP::Make(std::move(normalFP), fLights)
+        };
+        if (!fpPipeline[0] || !fpPipeline[1]) {
+            return nullptr;
+        }
+
+        std::unique_ptr<GrFragmentProcessor> innerLightFP = GrFragmentProcessor::RunInSeries(fpPipeline, 2);
+        // FP is wrapped because paint's alpha needs to be applied to output
+        return GrFragmentProcessor::MulChildByInputAlpha(std::move(innerLightFP));
+    } else {
+        // FP is wrapped because paint comes in unpremul'd to fragment shader, but LightingFP
+        // expects premul'd color.
+        return GrFragmentProcessor::PremulInput(LightingFP::Make(std::move(normalFP), fLights));
+    }
+}
+
+#endif
+
+////////////////////////////////////////////////////////////////////////////
+
+bool SkLightingShaderImpl::isOpaque() const {
+    return (fDiffuseShader ? fDiffuseShader->isOpaque() : false);
+}
+
+SkLightingShaderImpl::LightingShaderContext::LightingShaderContext(
+        const SkLightingShaderImpl& shader, const ContextRec& rec,
+        SkShaderBase::Context* diffuseContext, SkNormalSource::Provider* normalProvider,
+        void* heapAllocated)
+    : INHERITED(shader, rec)
+    , fDiffuseContext(diffuseContext)
+    , fNormalProvider(normalProvider) {
+    bool isOpaque = shader.isOpaque();
+
+    // update fFlags
+    uint32_t flags = 0;
+    if (isOpaque && (255 == this->getPaintAlpha())) {
+        flags |= kOpaqueAlpha_Flag;
+    }
+
+    fPaintColor = rec.fPaint->getColor();
+    fFlags = flags;
+}
+
+static inline SkPMColor convert(SkColor3f color, U8CPU a) {
+    if (color.fX <= 0.0f) {
+        color.fX = 0.0f;
+    } else if (color.fX >= 255.0f) {
+        color.fX = 255.0f;
+    }
+
+    if (color.fY <= 0.0f) {
+        color.fY = 0.0f;
+    } else if (color.fY >= 255.0f) {
+        color.fY = 255.0f;
+    }
+
+    if (color.fZ <= 0.0f) {
+        color.fZ = 0.0f;
+    } else if (color.fZ >= 255.0f) {
+        color.fZ = 255.0f;
+    }
+
+    return SkPreMultiplyARGB(a, (int) color.fX,  (int) color.fY, (int) color.fZ);
+}
+
+// larger is better (fewer times we have to loop), but we shouldn't
+// take up too much stack-space (each one here costs 16 bytes)
+#define BUFFER_MAX 16
+void SkLightingShaderImpl::LightingShaderContext::shadeSpan(int x, int y,
+                                                            SkPMColor result[], int count) {
+    const SkLightingShaderImpl& lightShader = static_cast<const SkLightingShaderImpl&>(fShader);
+
+    SkPMColor diffuse[BUFFER_MAX];
+    SkPoint3 normals[BUFFER_MAX];
+
+    SkColor diffColor = fPaintColor;
+
+    do {
+        int n = SkTMin(count, BUFFER_MAX);
+
+        fNormalProvider->fillScanLine(x, y, normals, n);
+
+        if (fDiffuseContext) {
+            fDiffuseContext->shadeSpan(x, y, diffuse, n);
+        }
+
+        for (int i = 0; i < n; ++i) {
+            if (fDiffuseContext) {
+                diffColor = SkUnPreMultiply::PMColorToColor(diffuse[i]);
+            }
+
+            SkColor3f accum = SkColor3f::Make(0.0f, 0.0f, 0.0f);
+
+            // Adding ambient light
+            accum.fX += lightShader.fLights->ambientLightColor().fX * SkColorGetR(diffColor);
+            accum.fY += lightShader.fLights->ambientLightColor().fY * SkColorGetG(diffColor);
+            accum.fZ += lightShader.fLights->ambientLightColor().fZ * SkColorGetB(diffColor);
+
+            // This is all done in linear unpremul color space (each component 0..255.0f though)
+            for (int l = 0; l < lightShader.fLights->numLights(); ++l) {
+                const SkLights::Light& light = lightShader.fLights->light(l);
+
+                SkScalar illuminanceScalingFactor = 1.0f;
+
+                if (SkLights::Light::kDirectional_LightType == light.type()) {
+                    illuminanceScalingFactor = normals[i].dot(light.dir());
+                    if (illuminanceScalingFactor < 0.0f) {
+                        illuminanceScalingFactor = 0.0f;
+                    }
+                }
+
+                accum.fX += light.color().fX * SkColorGetR(diffColor) * illuminanceScalingFactor;
+                accum.fY += light.color().fY * SkColorGetG(diffColor) * illuminanceScalingFactor;
+                accum.fZ += light.color().fZ * SkColorGetB(diffColor) * illuminanceScalingFactor;
+            }
+
+            // convert() premultiplies the accumulate color with alpha
+            result[i] = convert(accum, SkColorGetA(diffColor));
+        }
+
+        result += n;
+        x += n;
+        count -= n;
+    } while (count > 0);
+}
+
+////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkFlattenable> SkLightingShaderImpl::CreateProc(SkReadBuffer& buf) {
+
+    // Discarding SkShader flattenable params
+    bool hasLocalMatrix = buf.readBool();
+    SkAssertResult(!hasLocalMatrix);
+
+    sk_sp<SkLights> lights = SkLights::MakeFromBuffer(buf);
+
+    sk_sp<SkNormalSource> normalSource(buf.readFlattenable<SkNormalSource>());
+
+    bool hasDiffuse = buf.readBool();
+    sk_sp<SkShader> diffuseShader = nullptr;
+    if (hasDiffuse) {
+        diffuseShader = buf.readFlattenable<SkShaderBase>();
+    }
+
+    return sk_make_sp<SkLightingShaderImpl>(std::move(diffuseShader), std::move(normalSource),
+                                            std::move(lights));
+}
+
+void SkLightingShaderImpl::flatten(SkWriteBuffer& buf) const {
+    this->INHERITED::flatten(buf);
+
+    fLights->flatten(buf);
+
+    buf.writeFlattenable(fNormalSource.get());
+    buf.writeBool(static_cast<bool>(fDiffuseShader));
+    if (fDiffuseShader) {
+        buf.writeFlattenable(fDiffuseShader.get());
+    }
+}
+
+SkShaderBase::Context* SkLightingShaderImpl::onMakeContext(
+    const ContextRec& rec, SkArenaAlloc* alloc) const
+{
+    SkShaderBase::Context *diffuseContext = nullptr;
+    if (fDiffuseShader) {
+        diffuseContext = as_SB(fDiffuseShader)->makeContext(rec, alloc);
+        if (!diffuseContext) {
+            return nullptr;
+        }
+    }
+
+    SkNormalSource::Provider* normalProvider = fNormalSource->asProvider(rec, alloc);
+    if (!normalProvider) {
+        return nullptr;
+    }
+
+    return alloc->make<LightingShaderContext>(*this, rec, diffuseContext, normalProvider, nullptr);
+}
+
+sk_sp<SkShader> SkLightingShaderImpl::onMakeColorSpace(SkColorSpaceXformer* xformer) const {
+    sk_sp<SkShader> xformedDiffuseShader =
+            fDiffuseShader ? xformer->apply(fDiffuseShader.get()) : nullptr;
+    return SkLightingShader::Make(std::move(xformedDiffuseShader), fNormalSource,
+                                  fLights->makeColorSpace(xformer));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkShader> SkLightingShader::Make(sk_sp<SkShader> diffuseShader,
+                                       sk_sp<SkNormalSource> normalSource,
+                                       sk_sp<SkLights> lights) {
+    SkASSERT(lights);
+    if (!normalSource) {
+        normalSource = SkNormalSource::MakeFlat();
+    }
+
+    return sk_make_sp<SkLightingShaderImpl>(std::move(diffuseShader), std::move(normalSource),
+                                            std::move(lights));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkLightingShader)
+    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLightingShaderImpl)
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
+
+///////////////////////////////////////////////////////////////////////////////
diff --git a/src/shaders/SkLightingShader.h b/src/shaders/SkLightingShader.h
new file mode 100644
index 0000000000..62c881ccf6
--- /dev/null
+++ b/src/shaders/SkLightingShader.h
@@ -0,0 +1,40 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkLightingShader_DEFINED
+#define SkLightingShader_DEFINED
+
+#include "SkFlattenablePriv.h"
+#include "SkLights.h"
+#include "SkShader.h"
+
+class SkBitmap;
+class SkMatrix;
+class SkNormalSource;
+
+class SK_API SkLightingShader {
+public:
+    /** Returns a shader that lights the shape, colored by the diffuseShader, using the
+        normals from normalSource, with the set of lights provided.
+
+        @param  diffuseShader     the shader that provides the colors. If nullptr, uses the paint's
+                                  color.
+        @param  normalSource      the source for the shape's normals. If nullptr, assumes straight
+                                  up normals (<0,0,1>).
+        @param  lights            the lights applied to the normals
+
+        The lighting equation is currently:
+            result = (LightColor * dot(Normal, LightDir) + AmbientColor) * DiffuseColor
+
+    */
+    static sk_sp<SkShader> Make(sk_sp<SkShader> diffuseShader, sk_sp<SkNormalSource> normalSource,
+                                sk_sp<SkLights> lights);
+
+    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
+};
+
+#endif