Add gpu implementation of OverdrawXfermode

src/utils/debugger/SkOverdrawMode.cpp

Index: src/utils/debugger/SkOverdrawMode.cpp
diff --git a/src/utils/debugger/SkOverdrawMode.cpp b/src/utils/debugger/SkOverdrawMode.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..dfb2fc6d71b98c7586deb7c8cfa45bbddf9534ea
--- /dev/null
+++ b/src/utils/debugger/SkOverdrawMode.cpp
@@ -0,0 +1,334 @@
+/*
+ * 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 "SkColorPriv.h"
+#include "SkOverdrawMode.h"
+#include "SkString.h"
+#include "SkXfermode.h"
+
+#if SK_SUPPORT_GPU
+#include "GrFragmentProcessor.h"
+#include "GrInvariantOutput.h"
+#include "GrXferProcessor.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "glsl/GrGLSLXferProcessor.h"
+
+ ///////////////////////////////////////////////////////////////////////////////
+ // Fragment Processor
+ ///////////////////////////////////////////////////////////////////////////////
+
+class GLOverdrawFP;
+
+class GrOverdrawFP : public GrFragmentProcessor {
+public:
+    static const GrFragmentProcessor* Create(const GrFragmentProcessor* dst) {
+        return new GrOverdrawFP(dst);
+    }
+
+    ~GrOverdrawFP() override { }
+
+    const char* name() const override { return "Overdraw"; }
+
+    SkString dumpInfo() const override {
+        SkString str;
+        return str;
+    }
+
+private:
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
+
+    void onGetGLSLProcessorKey(const GrGLSLCaps&, GrProcessorKeyBuilder* b) const override;
+
+    bool onIsEqual(const GrFragmentProcessor&) const override { return true; }
+
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
+        inout->setToUnknown(GrInvariantOutput::kWill_ReadInput);
+    }
+
+    GrOverdrawFP(const GrFragmentProcessor* dst) {
+        this->initClassID<GrOverdrawFP>();
+
+        SkASSERT(dst);
+        SkDEBUGCODE(int dstIndex = )this->registerChildProcessor(dst);
+        SkASSERT(0 == dstIndex);
+    }
+
+    GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
+    typedef GrFragmentProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+static void add_overdraw_code(GrGLSLFragmentBuilder* fragBuilder,
+                              const char* dstColor,
+                              const char* outputColor) {
+
+    static const GrGLSLShaderVar gColorTableArgs[] = {
+        // TODO: once kInt_GrSLType lands - switch this over
+        GrGLSLShaderVar("index", kFloat_GrSLType),
+    };
+    SkString colorTableFuncName;
+
+    // The 'colorTable' function exists to work around older GLSL's prohibition
+    // of initialized arrays. It takes an integer index and just returns the
+    // corresponding color.
+   fragBuilder->emitFunction(kVec4f_GrSLType,
+                             "colorTable",
+                             SK_ARRAY_COUNT(gColorTableArgs),
+                             gColorTableArgs,
+                             "if (index < 1.5) { return vec4(0.5,   0.617, 1.0,   1.0); }"
+                             "if (index < 2.5) { return vec4(0.664, 0.723, 0.83,  1.0); }"
+                             "if (index < 3.5) { return vec4(0.832, 0.762, 0.664, 1.0); }"
+                             "if (index < 4.5) { return vec4(1,     0.75,  0.496, 1.0); }"
+                             "if (index < 5.5) { return vec4(1,     0.723, 0.332, 1.0); }"
+                             "if (index < 6.5) { return vec4(1,     0.645, 0.164, 1.0); }"
+                             "if (index < 7.5) { return vec4(1,     0.527, 0,     1.0); }"
+                             "if (index < 8.5) { return vec4(1,     0.371, 0,     1.0); }"
+                             "if (index < 9.5) { return vec4(1,     0.195, 0,     1.0); }"
+                             "return vec4(1,     0,     0,     1.0);",
+                             &colorTableFuncName);
+
+    fragBuilder->codeAppend("int nextIdx;");
+    fragBuilder->codeAppendf("vec4 dst = %s;", dstColor);
+    fragBuilder->codeAppend("if (dst.r < 0.25) { nextIdx = 1; }");
+    // cap 'idx' at 10
+    fragBuilder->codeAppend("else if (dst.g < 0.0977) { nextIdx = 10; }");
+    fragBuilder->codeAppend("else if (dst.b > 0.08) { nextIdx = 8 - int(6.0 * dst.b + 0.5); }");
+    fragBuilder->codeAppend("else { nextIdx = 11 - int(5.7 * dst.g + 0.5); }");
+    fragBuilder->codeAppendf("%s = %s(float(nextIdx));", outputColor, colorTableFuncName.c_str());
+}
+
+class GLOverdrawFP : public GrGLSLFragmentProcessor {
+public:
+    GLOverdrawFP(const GrOverdrawFP&) {}
+
+    ~GLOverdrawFP() override {}
+
+    void emitCode(EmitArgs& args) override {
+        GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+        SkString dstColor("dstColor");
+        this->emitChild(0, nullptr, &dstColor, args);
+
+        add_overdraw_code(fragBuilder, dstColor.c_str(), args.fOutputColor);
+    }
+
+    static void GenKey(const GrProcessor&, const GrGLSLCaps&, GrProcessorKeyBuilder*) { }
+
+private:
+    typedef GrGLSLFragmentProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+GrGLSLFragmentProcessor* GrOverdrawFP::onCreateGLSLInstance() const {
+    return new GLOverdrawFP(*this);
+}
+
+void GrOverdrawFP::onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const {
+    GLOverdrawFP::GenKey(*this, caps, b);
+}
+
+const GrFragmentProcessor* GrOverdrawFP::TestCreate(GrProcessorTestData* d) {
+    SkAutoTUnref<const GrFragmentProcessor> dst(GrProcessorUnitTest::CreateChildFP(d));
+    return new GrOverdrawFP(dst);
+}
+
+GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrOverdrawFP);
+
+///////////////////////////////////////////////////////////////////////////////
+// Xfer Processor
+///////////////////////////////////////////////////////////////////////////////
+
+class OverdrawXP : public GrXferProcessor {
+public:
+    OverdrawXP(const DstTexture* dstTexture, bool hasMixedSamples)
+        : INHERITED(dstTexture, true, hasMixedSamples) {
+        this->initClassID<OverdrawXP>();
+    }
+
+    const char* name() const override { return "Overdraw"; }
+
+    GrGLSLXferProcessor* createGLSLInstance() const override;
+
+private:
+    GrXferProcessor::OptFlags onGetOptimizations(const GrPipelineOptimizations& optimizations,
+                                                 bool doesStencilWrite,
+                                                 GrColor* overrideColor,
+                                                 const GrCaps& caps) const override {
+        // We never look at the color input
+        return GrXferProcessor::kIgnoreColor_OptFlag;
+    }
+
+    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override;
+
+    bool onIsEqual(const GrXferProcessor&) const override { return true; }
+
+    typedef GrXferProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+class GLOverdrawXP : public GrGLSLXferProcessor {
+public:
+    GLOverdrawXP(const OverdrawXP&) { }
+
+    ~GLOverdrawXP() 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 {
+        add_overdraw_code(fragBuilder, dstColor, outColor);
+
+        // Apply coverage.
+        INHERITED::DefaultCoverageModulation(fragBuilder, srcCoverage, dstColor, outColor,
+                                             outColorSecondary, proc);
+    }
+
+    void onSetData(const GrGLSLProgramDataManager&, const GrXferProcessor&) override { };
+
+    typedef GrGLSLXferProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+void OverdrawXP::onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const {
+    GLOverdrawXP::GenKey(*this, caps, b);
+}
+
+GrGLSLXferProcessor* OverdrawXP::createGLSLInstance() const { return new GLOverdrawXP(*this); }
+
+///////////////////////////////////////////////////////////////////////////////
+class GrOverdrawXPFactory : public GrXPFactory {
+public:
+    static GrXPFactory* Create() { return new GrOverdrawXPFactory(); }
+
+    void getInvariantBlendedColor(const GrProcOptInfo& colorPOI,
+                                  GrXPFactory::InvariantBlendedColor* blendedColor) const override {
+        blendedColor->fWillBlendWithDst = true;
+        blendedColor->fKnownColorFlags = kNone_GrColorComponentFlags;
+    }
+
+private:
+    GrOverdrawXPFactory() {
+        this->initClassID<GrOverdrawXPFactory>();
+    }
+
+    GrXferProcessor* onCreateXferProcessor(const GrCaps& caps,
+                                           const GrPipelineOptimizations& optimizations,
+                                           bool hasMixedSamples,
+                                           const DstTexture* dstTexture) const override {
+        return new OverdrawXP(dstTexture, hasMixedSamples);
+    }
+
+    bool willReadDstColor(const GrCaps& caps,
+                          const GrPipelineOptimizations& optimizations,
+                          bool hasMixedSamples) const override {
+        return true;
+    }
+
+    bool onIsEqual(const GrXPFactory& xpfBase) const override { return true; }
+
+    GR_DECLARE_XP_FACTORY_TEST;
+
+    typedef GrXPFactory INHERITED;
+};
+
+GR_DEFINE_XP_FACTORY_TEST(GrOverdrawXPFactory);
+
+const GrXPFactory* GrOverdrawXPFactory::TestCreate(GrProcessorTestData* d) {
+    return GrOverdrawXPFactory::Create();
+}
+#endif
+
+///////////////////////////////////////////////////////////////////////////////
+class SkOverdrawXfermode : public SkXfermode {
+public:
+    static SkXfermode* Create() {
+        return new SkOverdrawXfermode;
+    }
+
+    SkPMColor xferColor(SkPMColor src, SkPMColor dst) const override {
+        // This table encodes the color progression of the overdraw visualization
+        static const SkPMColor gTable[] = {
+            SkPackARGB32(0x00, 0x00, 0x00, 0x00),
+            SkPackARGB32(0xFF, 128, 158, 255),
+            SkPackARGB32(0xFF, 170, 185, 212),
+            SkPackARGB32(0xFF, 213, 195, 170),
+            SkPackARGB32(0xFF, 255, 192, 127),
+            SkPackARGB32(0xFF, 255, 185, 85),
+            SkPackARGB32(0xFF, 255, 165, 42),
+            SkPackARGB32(0xFF, 255, 135, 0),
+            SkPackARGB32(0xFF, 255,  95, 0),
+            SkPackARGB32(0xFF, 255,  50, 0),
+            SkPackARGB32(0xFF, 255,  0, 0)
+        };
+
+
+        int nextIdx;
+        if (SkColorGetR(dst) < 64) { // dst color is the 0th color so the next color is 1
+            nextIdx = 1;
+        } else if (SkColorGetG(dst) < 25) { // dst color is the 10th color so cap there
+            nextIdx = 10;
+        } else if ((SkColorGetB(dst)+21)/42 > 0) { // dst color is one of 1-6
+            nextIdx = 8 - (SkColorGetB(dst)+21)/42;
+        } else { // dst color is between 7 and 9
+            nextIdx = 11 - (SkColorGetG(dst)+22)/45;
+        }
+        SkASSERT(nextIdx < (int)SK_ARRAY_COUNT(gTable));
+
+        return gTable[nextIdx];
+    }
+
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkOverdrawXfermode)
+
+#if SK_SUPPORT_GPU
+    bool asFragmentProcessor(const GrFragmentProcessor** output,
+                             const GrFragmentProcessor* dst) const override {
+        if (output) {
+            *output = GrOverdrawFP::Create(dst);
+        }
+        return true;
+    }
+
+    bool asXPFactory(GrXPFactory** xpf) const override {
+        if (xpf) {
+            *xpf = GrOverdrawXPFactory::Create();
+        }
+        return true;
+    }
+#endif
+
+#ifndef SK_IGNORE_TO_STRING
+    void toString(SkString* str) const override { str->set("SkOverdrawXfermode"); }
+#endif
+
+private:
+    friend class SkOverdrawMode;
+
+    void flatten(SkWriteBuffer& buffer) const override { }
+
+    typedef SkXfermode INHERITED;
+};
+
+SkFlattenable* SkOverdrawXfermode::CreateProc(SkReadBuffer& buffer) {
+    return Create();
+}
+
+SkXfermode* SkOverdrawMode::Create() { return new SkOverdrawXfermode; }
+
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkOverdrawMode)
+    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkOverdrawXfermode)
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END