Add shader-based GaussianEdgeShader for reveal case

src/effects/SkRRectsGaussianEdgeShader.cpp

Index: src/effects/SkRRectsGaussianEdgeShader.cpp
diff --git a/src/effects/SkRRectsGaussianEdgeShader.cpp b/src/effects/SkRRectsGaussianEdgeShader.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..d3967dbb4434b55e41cce3367b75bd4d75967f30
--- /dev/null
+++ b/src/effects/SkRRectsGaussianEdgeShader.cpp
@@ -0,0 +1,435 @@
+/*
+ * 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 "SkRRectsGaussianEdgeShader.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+ /** \class SkRRectsGaussianEdgeShaderImpl
+  * This shader applies a gaussian edge to the intersection of two round rects.
+  * The round rects must have the same radii at each corner and the x&y radii
+  * must also be equal.
+  */
+class SkRRectsGaussianEdgeShaderImpl : public SkShader {
+public:
+    SkRRectsGaussianEdgeShaderImpl(const SkRRect& first, const SkRRect& second,
+                                   SkScalar radius, SkScalar pad)
+        : fFirst(first)
+        , fSecond(second)
+        , fRadius(radius)
+        , fPad(pad) {
+    }
+
+    bool isOpaque() const override { return false; }
+
+#if SK_SUPPORT_GPU
+    sk_sp<GrFragmentProcessor> asFragmentProcessor(const AsFPArgs&) const override;
+#endif
+
+    class GaussianEdgeShaderContext : public SkShader::Context {
+    public:
+        GaussianEdgeShaderContext(const SkRRectsGaussianEdgeShaderImpl&, const ContextRec&);
+
+        ~GaussianEdgeShaderContext() override { }
+
+        void shadeSpan(int x, int y, SkPMColor[], int count) override;
+
+        uint32_t getFlags() const override { return 0; }
+
+    private:
+        SkColor                   fPaintColor;
+
+        typedef SkShader::Context INHERITED;
+    };
+
+    SK_TO_STRING_OVERRIDE()
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkRRectsGaussianEdgeShaderImpl)
+
+protected:
+    void flatten(SkWriteBuffer&) const override;
+    size_t onContextSize(const ContextRec&) const override;
+    Context* onCreateContext(const ContextRec&, void*) const override;
+
+private:
+    SkRRect  fFirst;
+    SkRRect  fSecond;
+    SkScalar fRadius;
+    SkScalar fPad;
+
+    friend class SkRRectsGaussianEdgeShader; // for serialization registration system
+
+    typedef SkShader INHERITED;
+};
+
+////////////////////////////////////////////////////////////////////////////
+
+#if SK_SUPPORT_GPU
+
+#include "GrCoordTransform.h"
+#include "GrFragmentProcessor.h"
+#include "GrInvariantOutput.h"
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "glsl/GrGLSLProgramDataManager.h"
+#include "glsl/GrGLSLUniformHandler.h"
+#include "SkGr.h"
+#include "SkGrPriv.h"
+
+class RRectsGaussianEdgeFP : public GrFragmentProcessor {
+public:
+    enum Mode {
+        kCircle_Mode,
+        kRect_Mode,
+        kSimpleCircular_Mode,
+    };
+
+    RRectsGaussianEdgeFP(const SkRRect& first, const SkRRect& second,
+                         SkScalar radius, SkScalar pad)
+        : fFirst(first)
+        , fSecond(second)
+        , fRadius(radius)
+        , fPad(pad) {
+        this->initClassID<RRectsGaussianEdgeFP>();
+        this->setWillReadFragmentPosition();
+
+        fFirstMode = ComputeMode(fFirst);
+        fSecondMode = ComputeMode(fSecond);
+    }
+
+    class GLSLRRectsGaussianEdgeFP : public GrGLSLFragmentProcessor {
+    public:
+        GLSLRRectsGaussianEdgeFP() { }
+
+        void emitModeCode(Mode mode,
+                          GrGLSLFPFragmentBuilder* fragBuilder,
+                          const char* posName,
+                          const char* sizesName,
+                          const char* radiiName,
+                          const char* outputName,
+                          const char  indices[2]) { // how to access the params for the 2 rrects
+
+            // positive distance is towards the center of the circle
+            fragBuilder->codeAppendf("vec2 delta = %s.xy - %s.%s;",
+                                     fragBuilder->fragmentPosition(),
+                                     posName, indices);
+
+            switch (mode) {
+            case kCircle_Mode:
+                fragBuilder->codeAppendf("%s = %s.%c - length(delta);",
+                                         outputName,
+                                         sizesName, indices[0]);
+                break;
+            case kRect_Mode:
+                fragBuilder->codeAppendf("float xDist = %s.%c - abs(delta.x);",
+                                         sizesName, indices[0]);
+                fragBuilder->codeAppendf("float yDist = %s.%c - abs(delta.y);",
+                                         sizesName, indices[1]);
+                fragBuilder->codeAppendf("%s = min(xDist, yDist);", outputName);
+                break;
+            case kSimpleCircular_Mode:
+                // For the circular round rect we first compute the distance
+                // to the rect. Then we compute a multiplier that is 1 if the
+                // point is in one of the circular corners. We then compute the
+                // distance from the corner and then use the multiplier to mask
+                // between the two distances.
+                fragBuilder->codeAppendf("float xDist = %s.%c - abs(delta.x);",
+                                         sizesName, indices[0]);
+                fragBuilder->codeAppendf("float yDist = %s.%c - abs(delta.y);",
+                                         sizesName, indices[1]);
+                fragBuilder->codeAppend("float rectDist = min(xDist, yDist);");
+
+                fragBuilder->codeAppendf("vec2 cornerCenter = %s.%s - %s.%s;",
+                                         sizesName, indices,
+                                         radiiName, indices);
+                fragBuilder->codeAppend("delta = vec2(abs(delta.x) - cornerCenter.x,"
+                                                     "abs(delta.y) - cornerCenter.y);");
+                fragBuilder->codeAppendf("xDist = %s.%c - abs(delta.x);",
+                                         radiiName, indices[0]);
+                fragBuilder->codeAppendf("yDist = %s.%c - abs(delta.y);",
+                                         radiiName, indices[1]);
+                fragBuilder->codeAppend("float cornerDist = min(xDist, yDist);");
+                fragBuilder->codeAppend("float multiplier = step(0.0, cornerDist);");
+
+                fragBuilder->codeAppendf("delta += %s.%s;", radiiName, indices);
+
+                fragBuilder->codeAppendf("cornerDist = 2.0 * %s.%c - length(delta);",
+                                         radiiName, indices[0]);
+
+                fragBuilder->codeAppendf("%s = (multiplier * cornerDist) +"
+                                              "((1.0-multiplier) * rectDist);",
+                                         outputName);
+                break;
+            }
+        }
+
+        void emitCode(EmitArgs& args) override {
+            const RRectsGaussianEdgeFP& fp = args.fFp.cast<RRectsGaussianEdgeFP>();
+            GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
+            GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
+
+            const char* positionsUniName = nullptr;
+            fPositionsUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
+                                                       kVec4f_GrSLType, kDefault_GrSLPrecision,
+                                                       "Positions", &positionsUniName);
+            const char* sizesUniName = nullptr;
+            fSizesUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
+                                                   kVec4f_GrSLType, kDefault_GrSLPrecision,
+                                                   "Sizes", &sizesUniName);
+            const char* radiiUniName = nullptr;
+            fRadiiUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
+                                                   kVec4f_GrSLType, kDefault_GrSLPrecision,
+                                                   "Radii", &radiiUniName);
+            const char* padRadUniName = nullptr;
+            fPadRadUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
+                                                    kVec2f_GrSLType, kDefault_GrSLPrecision,
+                                                    "PadRad", &padRadUniName);
+
+            fragBuilder->codeAppend("float firstDist;");
+            fragBuilder->codeAppend("{");
+            this->emitModeCode(fp.firstMode(), fragBuilder,
+                               positionsUniName, sizesUniName, radiiUniName, "firstDist", "xy");
+            fragBuilder->codeAppend("}");
+
+            fragBuilder->codeAppend("float secondDist;");
+            fragBuilder->codeAppend("{");
+            this->emitModeCode(fp.secondMode(), fragBuilder,
+                               positionsUniName, sizesUniName, radiiUniName, "secondDist", "zw");
+            fragBuilder->codeAppend("}");
+
+            // Here use the sign of the distance to the two round rects to mask off the different
+            // cases.
+            fragBuilder->codeAppend("float in1 = step(0.0f, firstDist);");
+            fragBuilder->codeAppend("float in2 = step(0.0f, secondDist);");
+            fragBuilder->codeAppend("float dist = "
+                                             "in1*in2             * min(firstDist, secondDist);"
+                                             "in1*(1.0-in2)       * firstDist +"
+                                             "(1.0-in1)*in2       * secondDist;");
+
+            // Finally use the distance to apply the Gaussian edge
+            fragBuilder->codeAppendf("float factor = 1.0 - clamp((dist - %s.x)/%s.y, 0.0, 1.0);",
+                                     padRadUniName, padRadUniName);
+            fragBuilder->codeAppend("factor = exp(-factor * factor * 4.0) - 0.018;");
+            fragBuilder->codeAppendf("%s = vec4(%s.rgb, factor);",
+                                     args.fOutputColor, args.fInputColor);
+        }
+
+        static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
+                           GrProcessorKeyBuilder* b) {
+            const RRectsGaussianEdgeFP& fp = proc.cast<RRectsGaussianEdgeFP>();
+
+            b->add32(fp.firstMode() | (fp.secondMode() << 4));
+        }
+
+    protected:
+        void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {
+            const RRectsGaussianEdgeFP& edgeFP = proc.cast<RRectsGaussianEdgeFP>();
+
+            const SkRRect& first = edgeFP.first();
+            const SkRRect& second = edgeFP.second();
+
+            pdman.set4f(fPositionsUni,
+                        first.getBounds().centerX(),
+                        first.getBounds().centerY(),
+                        second.getBounds().centerX(),
+                        second.getBounds().centerY());
+
+            pdman.set4f(fSizesUni, 
+                        0.5f * first.rect().width(),
+                        0.5f * first.rect().height(),
+                        0.5f * second.rect().width(),
+                        0.5f * second.rect().height());
+
+            // This is a bit of overkill since fX should equal fY for both round rects but it
+            // makes the shader code simpler.
+            pdman.set4f(fRadiiUni, 
+                         0.5f * first.getSimpleRadii().fX,
+                         0.5f * first.getSimpleRadii().fY,
+                         0.5f * second.getSimpleRadii().fX,
+                         0.5f * second.getSimpleRadii().fY);
+
+            pdman.set2f(fPadRadUni, edgeFP.pad(), edgeFP.radius());
+        }
+
+    private:
+        // The centers of the two round rects (x1, y1, x2, y2)
+        GrGLSLProgramDataManager::UniformHandle fPositionsUni;
+
+        // The half widths and half heights of the two round rects (w1/2, h1/2, w2/2, h2/2)
+        // For circles we still upload both width & height to simplify things
+        GrGLSLProgramDataManager::UniformHandle fSizesUni;
+
+        // The half corner radii of the two round rects (rx1/2, ry1/2, rx2/2, ry2/2)
+        // We upload both the x&y radii (although they are currently always the same) to make
+        // the indexing in the shader code simpler. In some future world we could also support
+        // non-circular corner round rects & ellipses.
+        GrGLSLProgramDataManager::UniformHandle fRadiiUni;
+
+        // The pad and radius parameters (padding, radius)
+        GrGLSLProgramDataManager::UniformHandle fPadRadUni;
+
+        typedef GrGLSLFragmentProcessor INHERITED;
+    };
+
+    void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
+        GLSLRRectsGaussianEdgeFP::GenKey(*this, caps, b);
+    }
+
+    const char* name() const override { return "RRectsGaussianEdgeFP"; }
+
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
+        inout->setToUnknown(GrInvariantOutput::kWill_ReadInput);
+    }
+
+    const SkRRect& first() const { return fFirst; }
+    Mode firstMode() const { return fFirstMode; }
+    const SkRRect& second() const { return fSecond; }
+    Mode secondMode() const { return fSecondMode; }
+    SkScalar radius() const { return fRadius; }
+    SkScalar pad() const { return fPad; }
+
+private:
+    static Mode ComputeMode(const SkRRect& rr) {
+        if (rr.isCircle()) {
+            return kCircle_Mode;
+        } else if (rr.isRect()) {
+            return kRect_Mode;
+        } else {
+            SkASSERT(rr.isSimpleCircular());
+            return kSimpleCircular_Mode;
+        }
+    }
+
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override {
+        return new GLSLRRectsGaussianEdgeFP;
+    }
+
+    bool onIsEqual(const GrFragmentProcessor& proc) const override {
+        const RRectsGaussianEdgeFP& edgeFP = proc.cast<RRectsGaussianEdgeFP>();
+        return fFirst  == edgeFP.fFirst && fSecond == edgeFP.fSecond && 
+               fRadius == edgeFP.fRadius && fPad == edgeFP.fPad;
+    }
+
+    SkRRect  fFirst;
+    Mode     fFirstMode;
+    SkRRect  fSecond;
+    Mode     fSecondMode;
+    SkScalar fRadius;
+    SkScalar fPad;
+
+    typedef GrFragmentProcessor INHERITED;
+};
+
+////////////////////////////////////////////////////////////////////////////
+
+sk_sp<GrFragmentProcessor> SkRRectsGaussianEdgeShaderImpl::asFragmentProcessor(
+                                                                    const AsFPArgs& args) const {
+    return sk_make_sp<RRectsGaussianEdgeFP>(fFirst, fSecond, fRadius, fPad);
+}
+
+#endif
+
+////////////////////////////////////////////////////////////////////////////
+
+SkRRectsGaussianEdgeShaderImpl::GaussianEdgeShaderContext::GaussianEdgeShaderContext(
+                                                    const SkRRectsGaussianEdgeShaderImpl& shader,
+                                                    const ContextRec& rec)
+    : INHERITED(shader, rec) {
+
+    fPaintColor = rec.fPaint->getColor();
+}
+
+void SkRRectsGaussianEdgeShaderImpl::GaussianEdgeShaderContext::shadeSpan(int x, int y,
+                                                                          SkPMColor result[],
+                                                                          int count) {
+    // TODO: implement
+    for (int i = 0; i < count; ++i) {
+        result[i] = fPaintColor;
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////
+
+#ifndef SK_IGNORE_TO_STRING
+void SkRRectsGaussianEdgeShaderImpl::toString(SkString* str) const {
+    str->appendf("RRectsGaussianEdgeShader: ()");
+}
+#endif
+
+sk_sp<SkFlattenable> SkRRectsGaussianEdgeShaderImpl::CreateProc(SkReadBuffer& buf) {
+    // Discarding SkShader flattenable params
+    bool hasLocalMatrix = buf.readBool();
+    SkAssertResult(!hasLocalMatrix);
+
+    SkRect rect1, rect2;
+
+    buf.readRect(&rect1);
+    SkScalar xRad1 = buf.readScalar();
+    SkScalar yRad1 = buf.readScalar();
+
+    buf.readRect(&rect2);
+    SkScalar xRad2 = buf.readScalar();
+    SkScalar yRad2 = buf.readScalar();
+
+    SkScalar radius = buf.readScalar();
+    SkScalar pad = buf.readScalar();
+
+    return sk_make_sp<SkRRectsGaussianEdgeShaderImpl>(SkRRect::MakeRectXY(rect1, xRad1, yRad1),
+                                                      SkRRect::MakeRectXY(rect2, xRad2, yRad2),
+                                                      radius, pad);
+}
+
+void SkRRectsGaussianEdgeShaderImpl::flatten(SkWriteBuffer& buf) const {
+    INHERITED::flatten(buf);
+
+    SkASSERT(fFirst.isRect() || fFirst.isCircle() || fFirst.isSimpleCircular());
+    buf.writeRect(fFirst.rect());
+    const SkVector& radii1 = fFirst.getSimpleRadii();
+    buf.writeScalar(radii1.fX);
+    buf.writeScalar(radii1.fY);
+
+    SkASSERT(fSecond.isRect() || fSecond.isCircle() || fSecond.isSimpleCircular());
+    buf.writeRect(fSecond.rect());
+    const SkVector& radii2 = fSecond.getSimpleRadii();
+    buf.writeScalar(radii2.fX);
+    buf.writeScalar(radii2.fY);
+
+    buf.writeScalar(fRadius);
+    buf.writeScalar(fPad);
+}
+
+size_t SkRRectsGaussianEdgeShaderImpl::onContextSize(const ContextRec& rec) const {
+    return sizeof(GaussianEdgeShaderContext);
+}
+
+SkShader::Context* SkRRectsGaussianEdgeShaderImpl::onCreateContext(const ContextRec& rec,
+                                                                   void* storage) const {
+    return new (storage) GaussianEdgeShaderContext(*this, rec);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkShader> SkRRectsGaussianEdgeShader::Make(const SkRRect& first,
+                                                 const SkRRect& second,
+                                                 SkScalar radius,
+                                                 SkScalar pad) {
+    if ((!first.isRect()  && !first.isCircle()  && !first.isSimpleCircular()) || 
+        (!second.isRect() && !second.isCircle() && !second.isSimpleCircular())) {
+        // we only deal with the shapes where the x & y radii are equal 
+        // and the same for all four corners
+        return nullptr;
+    }
+
+    return sk_make_sp<SkRRectsGaussianEdgeShaderImpl>(first, second, radius, pad);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkRRectsGaussianEdgeShader)
+SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkRRectsGaussianEdgeShaderImpl)
+SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
+
+///////////////////////////////////////////////////////////////////////////////