Add gpu backend for SkPixelXorXfermode

src/effects/SkPixelXorXfermode.cpp

Index: src/effects/SkPixelXorXfermode.cpp
diff --git a/src/effects/SkPixelXorXfermode.cpp b/src/effects/SkPixelXorXfermode.cpp
index 8e13b2250cab2d5bff2e4cd27b68715a9d8b37ed..5ea82e63092680059c1e6795eedeb63285f8be78 100644
--- a/src/effects/SkPixelXorXfermode.cpp
+++ b/src/effects/SkPixelXorXfermode.cpp
@@ -1,4 +1,3 @@
-
 /*
  * Copyright 2011 Google Inc.
  *
@@ -6,7 +5,6 @@
  * found in the LICENSE file.
  */
 
-
 #include "SkPixelXorXfermode.h"
 #include "SkColorPriv.h"
 #include "SkReadBuffer.h"
@@ -19,6 +17,7 @@
 // the alpha-component and still return a valid premultiplied color.
 SkPMColor SkPixelXorXfermode::xferColor(SkPMColor src, SkPMColor dst) const {
     SkPMColor res = src ^ dst ^ fOpColor;
+
     res |= (SK_A32_MASK << SK_A32_SHIFT);   // force it to be opaque
     return res;
 }
@@ -38,6 +37,358 @@ void SkPixelXorXfermode::toString(SkString* str) const {
 }
 #endif
 
+#if SK_SUPPORT_GPU
+#include "GrFragmentProcessor.h"
+#include "GrInvariantOutput.h"
+#include "GrXferProcessor.h"
+
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "glsl/GrGLSLProgramDataManager.h"
+#include "glsl/GrGLSLUniformHandler.h"
+#include "glsl/GrGLSLXferProcessor.h"
+
+///////////////////////////////////////////////////////////////////////////////
+// Fragment Processor
+///////////////////////////////////////////////////////////////////////////////
+
+static void add_pixelxor_code(GrGLSLFragmentBuilder* fragBuilder,
+                              const char* srcColor,
+                              const char* dstColor,
+                              const char* outputColor,
+                              const char* opColor) {
+    static const GrGLSLShaderVar gXorArgs[] = {
+        GrGLSLShaderVar("f1", kFloat_GrSLType),
+        GrGLSLShaderVar("f2", kFloat_GrSLType),
+        GrGLSLShaderVar("f3", kFloat_GrSLType),
+        GrGLSLShaderVar("fPowerOf2Divisor", kFloat_GrSLType),
+    };
+    SkString xorFuncName;
+
+    // The xor function checks if the three passed in floats (f1, f2, f3) would
+    // have a bit in the log2(fPowerOf2Divisor)-th position if they were 
+    // represented by an int. It then performs an xor of the 3 bits (using 
+    // the property that serial xors can be treated as a sum of 0s & 1s mod 2).
+    fragBuilder->emitFunction(kFloat_GrSLType,
+                              "xor",
+                              SK_ARRAY_COUNT(gXorArgs),
+                              gXorArgs,
+                              "float bit1 = floor(f1 / fPowerOf2Divisor);"
+                              "float bit2 = floor(f2 / fPowerOf2Divisor);"
+                              "float bit3 = floor(f3 / fPowerOf2Divisor);"
+                              "return mod(bit1 + bit2 + bit3, 2.0);",
+                              &xorFuncName);
+
+    fragBuilder->codeAppend("float red = 0.0, green = 0.0, blue = 0.0;");
+
+    if (srcColor) {
+        fragBuilder->codeAppendf("vec3 src = 255.99 * %s.rgb;", srcColor);
+    } else {
+        fragBuilder->codeAppendf("vec3 src = vec3(255.99);");
+    }
+    fragBuilder->codeAppendf("vec3 dst = 255.99 * %s.rgb;", dstColor);
+    fragBuilder->codeAppendf("vec3 op  = 255.99 * %s;", opColor);
+
+    fragBuilder->codeAppend("float modValue = 128.0;");
+
+    fragBuilder->codeAppend("for (int i = 0; i < 8; i++) {");
+
+    fragBuilder->codeAppendf("float bit = %s(src.r, dst.r, op.r, modValue);", xorFuncName.c_str());
+    fragBuilder->codeAppend("red += modValue * bit;");
+    fragBuilder->codeAppend("src.r = mod(src.r, modValue);");
+    fragBuilder->codeAppend("dst.r = mod(dst.r, modValue);");
+    fragBuilder->codeAppend("op.r = mod(op.r, modValue);");
+
+    fragBuilder->codeAppendf("bit = %s(src.g, dst.g, op.g, modValue);", xorFuncName.c_str());
+    fragBuilder->codeAppend("green += modValue * bit;");
+    fragBuilder->codeAppend("src.g = mod(src.g, modValue);");
+    fragBuilder->codeAppend("dst.g = mod(dst.g, modValue);");
+    fragBuilder->codeAppend("op.g = mod(op.g, modValue);");
+
+    fragBuilder->codeAppendf("bit = %s(src.b, dst.b, op.b, modValue);", xorFuncName.c_str());
+    fragBuilder->codeAppend("blue += modValue * bit;");
+    fragBuilder->codeAppend("src.b = mod(src.b, modValue);");
+    fragBuilder->codeAppend("dst.b = mod(dst.b, modValue);");
+    fragBuilder->codeAppend("op.b = mod(op.b, modValue);");
+
+    fragBuilder->codeAppend("modValue /= 2.0;");
+
+    fragBuilder->codeAppend("}");
+
+    fragBuilder->codeAppendf("%s = vec4(red/255.0, green/255.0, blue/255.0, 1.0);", outputColor);
+}
+
+class GLPixelXorFP;
+
+class PixelXorFP : public GrFragmentProcessor {
+public:
+    static const GrFragmentProcessor* Create(SkColor opColor, const GrFragmentProcessor* dst) {
+        return new PixelXorFP(opColor, dst);
+    }
+
+    ~PixelXorFP() override {};
+
+    const char* name() const override { return "PixelXor"; }
+
+    SkString dumpInfo() const override {
+        SkString str;
+        str.appendf("Color: 0x%08x", fOpColor);
+        return str;
+    }
+
+    SkColor opColor() const { return fOpColor; }
+
+private:
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
+
+    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override;
+
+    bool onIsEqual(const GrFragmentProcessor& fpBase) const override {
+        const PixelXorFP& fp = fpBase.cast<PixelXorFP>();
+        return fOpColor == fp.fOpColor;
+    }
+
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
+        inout->setToUnknown(GrInvariantOutput::kWill_ReadInput);
+    }
+
+    PixelXorFP(SkColor opColor, const GrFragmentProcessor* dst)
+        : fOpColor(opColor) {
+        this->initClassID<PixelXorFP>();
+
+        SkASSERT(dst);
+        SkDEBUGCODE(int dstIndex = )this->registerChildProcessor(dst);
+        SkASSERT(0 == dstIndex);
+    }
+
+    SkColor fOpColor;
+
+    GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
+    typedef GrFragmentProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+class GLPixelXorFP : public GrGLSLFragmentProcessor {
+public:
+    GLPixelXorFP(const PixelXorFP&) {}
+
+    ~GLPixelXorFP() override {}
+
+    void emitCode(EmitArgs& args) override {
+        GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+        SkString dstColor("dstColor");
+        this->emitChild(0, nullptr, &dstColor, args);
+
+        fOpColorUni = args.fUniformHandler->addUniform(GrGLSLUniformHandler::kFragment_Visibility,
+                                                       kVec3f_GrSLType, kHigh_GrSLPrecision,
+                                                       "opColor");
+        const char* kOpColorUni = args.fUniformHandler->getUniformCStr(fOpColorUni);
+
+        add_pixelxor_code(fragBuilder, args.fInputColor, dstColor.c_str(),
+                          args.fOutputColor, kOpColorUni);
+    }
+
+    static void GenKey(const GrProcessor&, const GrGLSLCaps&, GrProcessorKeyBuilder*) { }
+
+protected:
+    void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {
+        const PixelXorFP& pixXor = proc.cast<PixelXorFP>();
+        pdman.set3f(fOpColorUni,
+                    SkColorGetR(pixXor.opColor())/255.0f,
+                    SkColorGetG(pixXor.opColor())/255.0f,
+                    SkColorGetB(pixXor.opColor())/255.0f);
+    }
+
+private:
+    GrGLSLProgramDataManager::UniformHandle fOpColorUni;
+
+    typedef GrGLSLFragmentProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+GrGLSLFragmentProcessor* PixelXorFP::onCreateGLSLInstance() const {
+    return new GLPixelXorFP(*this);
+}
+
+void PixelXorFP::onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const {
+    GLPixelXorFP::GenKey(*this, caps, b);
+}
+
+const GrFragmentProcessor* PixelXorFP::TestCreate(GrProcessorTestData* d) {
+    SkColor color = d->fRandom->nextU();
+
+    SkAutoTUnref<const GrFragmentProcessor> dst(GrProcessorUnitTest::CreateChildFP(d));
+    return new PixelXorFP(color, dst);
+}
+
+GR_DEFINE_FRAGMENT_PROCESSOR_TEST(PixelXorFP);
+
+///////////////////////////////////////////////////////////////////////////////
+// Xfer Processor
+///////////////////////////////////////////////////////////////////////////////
+
+class PixelXorXP : public GrXferProcessor {
+public:
+    PixelXorXP(const DstTexture* dstTexture, bool hasMixedSamples, SkColor opColor)
+        : INHERITED(dstTexture, true, hasMixedSamples)
+        , fOpColor(opColor) {
+        this->initClassID<PixelXorXP>();
+    }
+
+    const char* name() const override { return "PixelXor"; }
+
+    GrGLSLXferProcessor* createGLSLInstance() const override;
+
+    SkColor opColor() const { return fOpColor; }
+
+private:
+    GrXferProcessor::OptFlags onGetOptimizations(const GrPipelineOptimizations& optimizations,
+                                                 bool doesStencilWrite,
+                                                 GrColor* overrideColor,
+                                                 const GrCaps& caps) const override {
+        return GrXferProcessor::kNone_OptFlags;
+    }
+
+    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override;
+
+    bool onIsEqual(const GrXferProcessor& xpBase) const override {
+        const PixelXorXP& xp = xpBase.cast<PixelXorXP>();
+
+        return fOpColor == xp.fOpColor;
+    }
+
+    SkColor fOpColor;
+
+    typedef GrXferProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+class GLPixelXorXP : public GrGLSLXferProcessor {
+public:
+    GLPixelXorXP(const PixelXorXP& pixelXorXP) { }
+
+    ~GLPixelXorXP() override {}
+
+    static void GenKey(const GrProcessor&, const GrGLSLCaps&, GrProcessorKeyBuilder*) { }
+
+private:
+    void emitBlendCodeForDstRead(GrGLSLXPFragmentBuilder* fragBuilder,
+                                 GrGLSLUniformHandler* uniformHandler,
+                                 const char* srcColor,
+                                 const char* srcCoverage,
+                                 const char* dstColor,
+                                 const char* outColor,
+                                 const char* outColorSecondary,
+                                 const GrXferProcessor& proc) override {
+        fOpColorUni = uniformHandler->addUniform(GrGLSLUniformHandler::kFragment_Visibility,
+                                                 kVec3f_GrSLType, kHigh_GrSLPrecision,
+                                                 "opColor");
+        const char* kOpColorUni = uniformHandler->getUniformCStr(fOpColorUni);
+
+        add_pixelxor_code(fragBuilder, srcColor, dstColor, outColor, kOpColorUni);
+
+        // Apply coverage.
+        INHERITED::DefaultCoverageModulation(fragBuilder, srcCoverage, dstColor, outColor,
+                                             outColorSecondary, proc);
+    }
+
+    void onSetData(const GrGLSLProgramDataManager& pdman,
+                   const GrXferProcessor& processor) override {
+        const PixelXorXP& pixelXor = processor.cast<PixelXorXP>();
+        pdman.set3f(fOpColorUni, 
+                    SkColorGetR(pixelXor.opColor())/255.0f,
+                    SkColorGetG(pixelXor.opColor())/255.0f,
+                    SkColorGetB(pixelXor.opColor())/255.0f);
+    };
+
+    GrGLSLProgramDataManager::UniformHandle fOpColorUni;
+
+    typedef GrGLSLXferProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+void PixelXorXP::onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const {
+    GLPixelXorXP::GenKey(*this, caps, b);
+}
+
+GrGLSLXferProcessor* PixelXorXP::createGLSLInstance() const { return new GLPixelXorXP(*this); }
+
+///////////////////////////////////////////////////////////////////////////////
+
+class GrPixelXorXPFactory : public GrXPFactory {
+public:
+    static GrXPFactory* Create(SkColor opColor) {
+        return new GrPixelXorXPFactory(opColor);
+    }
+
+    void getInvariantBlendedColor(const GrProcOptInfo& colorPOI,
+                                  GrXPFactory::InvariantBlendedColor* blendedColor) const override {
+        blendedColor->fWillBlendWithDst = true;
+        blendedColor->fKnownColorFlags = kNone_GrColorComponentFlags;
+    }
+
+private:
+    GrPixelXorXPFactory(SkColor opColor)
+        : fOpColor(opColor) {
+        this->initClassID<GrPixelXorXPFactory>();
+    }
+
+    GrXferProcessor* onCreateXferProcessor(const GrCaps& caps,
+                                           const GrPipelineOptimizations& optimizations,
+                                           bool hasMixedSamples,
+                                           const DstTexture* dstTexture) const override {
+        return new PixelXorXP(dstTexture, hasMixedSamples, fOpColor);
+    }
+
+    bool willReadDstColor(const GrCaps& caps,
+                          const GrPipelineOptimizations& optimizations,
+                          bool hasMixedSamples) const override {
+        return true;
+    }
+
+    bool onIsEqual(const GrXPFactory& xpfBase) const override {
+        const GrPixelXorXPFactory& xpf = xpfBase.cast<GrPixelXorXPFactory>();
+        return fOpColor == xpf.fOpColor;
+    }
+
+    GR_DECLARE_XP_FACTORY_TEST;
+
+    SkColor fOpColor;
+
+    typedef GrXPFactory INHERITED;
+};
+
+GR_DEFINE_XP_FACTORY_TEST(GrPixelXorXPFactory);
+
+const GrXPFactory* GrPixelXorXPFactory::TestCreate(GrProcessorTestData* d) {
+    SkColor color = d->fRandom->nextU();
+
+    return GrPixelXorXPFactory::Create(color);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+bool SkPixelXorXfermode::asFragmentProcessor(const GrFragmentProcessor** output,
+    const GrFragmentProcessor* dst) const {
+    if (output) {
+        *output = PixelXorFP::Create(fOpColor, dst);
+    }
+    return true;
+}
+
+bool SkPixelXorXfermode::asXPFactory(GrXPFactory** xpf) const {
+    if (xpf) {
+        *xpf = GrPixelXorXPFactory::Create(fOpColor);
+    }
+    return true;
+}
+
+#endif
+
 SkValue SkPixelXorXfermode::asValue() const {
     auto value = SkValue::Object(SkValue::PixelXorXfermode);
     value.set(SkValueKeys::PixelXorXfermode::kOpColor,