Added GPU implementation of 2-point conical gradient.

Review URL: https://codereview.appspot.com/6354062

git-svn-id: http://skia.googlecode.com/svn/trunk@4442 2bbb7eff-a529-9590-31e7-b0007b416f81

2 files changed, 349 insertions, 10 deletions

diff --git a/src/gpu/effects/GrGradientEffects.cpp b/src/gpu/effects/GrGradientEffects.cpp
index d876d62990..005002fc95 100644
--- a/src/gpu/effects/GrGradientEffects.cpp
+++ b/src/gpu/effects/GrGradientEffects.cpp
@@ -35,9 +35,9 @@ private:
 };
 
 void GrGLRadialGradient::emitFS(GrGLShaderBuilder* state,
-                        const char* outputColor,
-                        const char* inputColor,
-                        const char* samplerName) {
+                                const char* outputColor,
+                                const char* inputColor,
+                                const char* samplerName) {
     state->fSampleCoords.printf("vec2(length(%s.xy), 0.5)",
                                 state->fSampleCoords.c_str());
     state->fComplexCoord = true;
@@ -161,7 +161,7 @@ void GrGLRadial2Gradient::setupVariables(GrGLShaderBuilder* state, int stage) {
 }
 
 void GrGLRadial2Gradient::emitVS(GrGLShaderBuilder* state,
-                        const char* vertexCoords) {
+                                 const char* vertexCoords) {
     GrStringBuilder* code = &state->fVSCode;
     GrStringBuilder p2;
     GrStringBuilder p3;
@@ -179,9 +179,9 @@ void GrGLRadial2Gradient::emitVS(GrGLShaderBuilder* state,
 }
 
 void GrGLRadial2Gradient::emitFS(GrGLShaderBuilder* state,
-                        const char* outputColor,
-                        const char* inputColor,
-                        const char* samplerName) {
+                                 const char* outputColor,
+                                 const char* inputColor,
+                                 const char* samplerName) {
     GrStringBuilder* code = &state->fFSCode;
     GrStringBuilder cName("c");
     GrStringBuilder ac4Name("ac4");
@@ -259,9 +259,9 @@ void GrGLRadial2Gradient::initUniforms(const GrGLInterface* gl, int programID) {
 }
 
 void GrGLRadial2Gradient::setData(const GrGLInterface* gl,
-                                 const GrGLTexture& texture,
-                                 const GrCustomStage& baseData,
-                                 int stageNum) {
+                                  const GrGLTexture& texture,
+                                  const GrCustomStage& baseData,
+                                  int stageNum) {
     const GrRadial2Gradient& data =
         static_cast<const GrRadial2Gradient&>(baseData);
     GrAssert(data.isDegenerate() == fIsDegenerate);
@@ -323,6 +323,307 @@ bool GrRadial2Gradient::isEqual(const GrCustomStage& sBase) const {
 
 /////////////////////////////////////////////////////////////////////
 
+class GrGLConical2Gradient : public GrGLProgramStage {
+
+public:
+
+    GrGLConical2Gradient(const GrProgramStageFactory& factory,
+                         const GrCustomStage&);
+    virtual ~GrGLConical2Gradient() { }
+
+    virtual void setupVariables(GrGLShaderBuilder* state,
+                                int stage) SK_OVERRIDE;
+    virtual void emitVS(GrGLShaderBuilder* state,
+                        const char* vertexCoords) SK_OVERRIDE;
+    virtual void emitFS(GrGLShaderBuilder* state,
+                        const char* outputColor,
+                        const char* inputColor,
+                        const char* samplerName) SK_OVERRIDE;
+    virtual void initUniforms(const GrGLInterface*, int programID) SK_OVERRIDE;
+    virtual void setData(const GrGLInterface*,
+                         const GrGLTexture&,
+                         const GrCustomStage&,
+                         int stageNum) SK_OVERRIDE;
+
+    static StageKey GenKey(const GrCustomStage& s) {
+        return (static_cast<const GrConical2Gradient&>(s).isDegenerate());
+    }
+
+protected:
+
+    const GrGLShaderVar* fVSParamVar;
+    GrGLint fVSParamLocation;
+    const GrGLShaderVar* fFSParamVar;
+    GrGLint fFSParamLocation;
+
+    const char* fVSVaryingName;
+    const char* fFSVaryingName;
+
+    bool fIsDegenerate;
+
+    // @{
+    /// Values last uploaded as uniforms
+
+    GrScalar fCachedCenter;
+    GrScalar fCachedRadius;
+    GrScalar fCachedDiffRadius;
+
+    // @}
+
+private:
+
+    typedef GrGLProgramStage INHERITED;
+
+};
+
+GrGLConical2Gradient::GrGLConical2Gradient(
+        const GrProgramStageFactory& factory,
+        const GrCustomStage& baseData)
+    : INHERITED(factory)
+    , fVSParamVar(NULL)
+    , fFSParamVar(NULL)
+    , fVSVaryingName(NULL)
+    , fFSVaryingName(NULL)
+    , fCachedCenter(GR_ScalarMax)
+    , fCachedRadius(-GR_ScalarMax)
+    , fCachedDiffRadius(-GR_ScalarMax) {
+
+    const GrConical2Gradient& data =
+        static_cast<const GrConical2Gradient&>(baseData);
+    fIsDegenerate = data.isDegenerate();
+}
+
+void GrGLConical2Gradient::setupVariables(GrGLShaderBuilder* state, int stage) {
+    // 2 copies of uniform array, 1 for each of vertex & fragment shader,
+    // to work around Xoom bug. Doesn't seem to cause performance decrease
+    // in test apps, but need to keep an eye on it.
+    fVSParamVar = &state->addUniform(
+        GrGLShaderBuilder::kVertex_VariableLifetime,
+        kFloat_GrSLType, "uConical2VSParams", stage, 6);
+    fFSParamVar = &state->addUniform(
+        GrGLShaderBuilder::kFragment_VariableLifetime,
+        kFloat_GrSLType, "uConical2FSParams", stage, 6);
+
+    fVSParamLocation = GrGLProgramStage::kUseUniform;
+    fFSParamLocation = GrGLProgramStage::kUseUniform;
+
+    // For radial gradients without perspective we can pass the linear
+    // part of the quadratic as a varying.
+    if (state->fVaryingDims == state->fCoordDims) {
+        state->addVarying(kFloat_GrSLType, "Conical2BCoeff", stage,
+                          &fVSVaryingName, &fFSVaryingName);
+    }
+}
+
+void GrGLConical2Gradient::emitVS(GrGLShaderBuilder* state,
+                                  const char* vertexCoords) {
+    GrStringBuilder* code = &state->fVSCode;
+    GrStringBuilder p2; // distance between centers
+    GrStringBuilder p3; // start radius
+    GrStringBuilder p5; // difference in radii (r1 - r0)
+    fVSParamVar->appendArrayAccess(2, &p2);
+    fVSParamVar->appendArrayAccess(3, &p3);
+    fVSParamVar->appendArrayAccess(5, &p5);
+
+    // For radial gradients without perspective we can pass the linear
+    // part of the quadratic as a varying.
+    if (state->fVaryingDims == state->fCoordDims) {
+        // r2Var = -2 * (r2Parm[2] * varCoord.x - r2Param[3] * r2Param[5])
+        code->appendf("\t%s = -2.0 * (%s * %s.x + %s * %s);\n",
+                      fVSVaryingName, p2.c_str(),
+                      vertexCoords, p3.c_str(), p5.c_str());
+    }
+}
+
+void GrGLConical2Gradient::emitFS(GrGLShaderBuilder* state,
+                                  const char* outputColor,
+                                  const char* inputColor,
+                                  const char* samplerName) {
+    GrStringBuilder* code = &state->fFSCode;
+
+    GrStringBuilder cName("c");
+    GrStringBuilder ac4Name("ac4");
+    GrStringBuilder dName("d");
+    GrStringBuilder qName("q");
+    GrStringBuilder r0Name("r0");
+    GrStringBuilder r1Name("r1");
+    GrStringBuilder tName("t");
+    GrStringBuilder p0; // 4a
+    GrStringBuilder p1; // 1/(2a)
+    GrStringBuilder p2; // distance between centers
+    GrStringBuilder p3; // start radius
+    GrStringBuilder p4; // start radius squared
+    GrStringBuilder p5; // difference in radii (r1 - r0)
+    fFSParamVar->appendArrayAccess(0, &p0);
+    fFSParamVar->appendArrayAccess(1, &p1);
+    fFSParamVar->appendArrayAccess(2, &p2);
+    fFSParamVar->appendArrayAccess(3, &p3);
+    fFSParamVar->appendArrayAccess(4, &p4);
+    fFSParamVar->appendArrayAccess(5, &p5);
+
+    // If we we're able to interpolate the linear component,
+    // bVar is the varying; otherwise compute it
+    GrStringBuilder bVar;
+    if (state->fCoordDims == state->fVaryingDims) {
+        bVar = fFSVaryingName;
+        GrAssert(2 == state->fVaryingDims);
+    } else {
+        GrAssert(3 == state->fVaryingDims);
+        bVar = "b";
+        code->appendf("\tfloat %s = -2.0 * (%s * %s.x + %s * %s);\n", 
+                      bVar.c_str(), p2.c_str(), state->fSampleCoords.c_str(), 
+                      p3.c_str(), p5.c_str());
+    }
+
+    // c = (x^2)+(y^2) - params[4]
+    code->appendf("\tfloat %s = dot(%s, %s) - %s;\n", cName.c_str(), 
+                  state->fSampleCoords.c_str(), state->fSampleCoords.c_str(),
+                  p4.c_str());
+
+    // Non-degenerate case (quadratic)
+    if (!fIsDegenerate) {
+
+        // ac4 = params[0] * c
+        code->appendf("\tfloat %s = %s * %s;\n", ac4Name.c_str(), p0.c_str(),
+                      cName.c_str());
+        
+        // d = b^2 - ac4
+        code->appendf("\tfloat %s = %s * %s - %s;\n", dName.c_str(), 
+                      bVar.c_str(), bVar.c_str(), ac4Name.c_str());
+
+        // if discriminant is < 0, set to transparent black and return
+        code->appendf("\tif (%s < 0.0) {\n\t\tgl_FragColor = vec4(0.0,0.0,0.0,"
+                      "0.0);\n\t\treturn;\n\t}\n", dName.c_str());
+
+        // intermediate value we'll use to compute the roots
+        // q = -0.5 * (b +/- sqrt(d))
+        code->appendf("\tfloat %s = -0.5f * (%s + (%s < 0.0 ? -1.0 : 1.0)"
+                      " * sqrt(%s));\n", qName.c_str(), bVar.c_str(), 
+                      bVar.c_str(), dName.c_str());
+
+        // compute both roots
+        // r0 = q * params[1]
+        code->appendf("\tfloat %s = %s * %s;\n", r0Name.c_str(), qName.c_str(),
+                      p1.c_str());
+        // r1 = c / q
+        code->appendf("\tfloat %s = %s / %s;\n", r1Name.c_str(), cName.c_str(),
+                      qName.c_str());
+
+        // Note: If there are two roots that both generate radius(t) > 0, the 
+        // Canvas spec says to choose the larger t.
+
+        // so we'll look at the larger one first:
+        code->appendf("\tfloat %s = max(%s, %s);\n", tName.c_str(), 
+                      r0Name.c_str(), r1Name.c_str());
+
+        // if r(t) for the larger root is <= 0, try the other one
+        code->appendf("\tif (%s * %s + %s <= 0.0) {\n", tName.c_str(), 
+                      p5.c_str(), p3.c_str());
+        code->appendf("\t\t%s = min(%s, %s);\n", tName.c_str(), 
+                      r0Name.c_str(), r1Name.c_str());
+
+        // if r(t) for the smaller root is also <= 0, set the fragment to 
+        // transparent black and return
+        code->appendf("\t\tif (%s * %s + %s <= 0.0) {\n\t\t\tgl_FragColor = "
+                      "vec4(0.0,0.0,0.0,0.0);\n\t\t\treturn;\n\t\t}\n", 
+                      tName.c_str(), p5.c_str(), p3.c_str());
+        
+        code->appendf("\t}\n");
+    } else {
+
+        // linear case: t = -c/b
+        code->appendf("\tfloat %s = -(%s / %s);\n", tName.c_str(), 
+                      cName.c_str(), bVar.c_str());
+
+        // set the fragment to transparent black and return if r(t) is <= 0
+        code->appendf("\tif (%s * %s + %s <= 0.0) {\n\t\tgl_FragColor = vec4("
+                      "0.0,0.0,0.0,0.0);\n\t\treturn;\n\t}\n", tName.c_str(),
+                      p5.c_str(), p3.c_str());
+    }
+    state->fComplexCoord = true;
+
+    // x coord is: t
+    // y coord is 0.5 (texture is effectively 1D)
+    state->fSampleCoords.printf("\tvec2(%s, 0.5)", tName.c_str());
+
+    state->emitDefaultFetch(outputColor, samplerName);
+}
+
+void GrGLConical2Gradient::initUniforms(const GrGLInterface* gl, int programID) {
+    GR_GL_CALL_RET(gl, fVSParamLocation,
+        GetUniformLocation(programID, fVSParamVar->getName().c_str()));
+    GR_GL_CALL_RET(gl, fFSParamLocation,
+        GetUniformLocation(programID, fFSParamVar->getName().c_str()));
+}
+
+void GrGLConical2Gradient::setData(const GrGLInterface* gl,
+                                   const GrGLTexture& texture,
+                                   const GrCustomStage& baseData,
+                                   int stageNum) {
+    const GrConical2Gradient& data =
+        static_cast<const GrConical2Gradient&>(baseData);
+    GrAssert(data.isDegenerate() == fIsDegenerate);
+    GrScalar centerX1 = data.center();
+    GrScalar radius0 = data.radius();
+    GrScalar diffRadius = data.diffRadius();
+
+    if (fCachedCenter != centerX1 ||
+        fCachedRadius != radius0 ||
+        fCachedDiffRadius != diffRadius) {
+
+        GrScalar a = GrMul(centerX1, centerX1) - diffRadius * diffRadius;
+
+        // When we're in the degenerate (linear) case, the second
+        // value will be INF but the program doesn't read it. (We
+        // use the same 6 uniforms even though we don't need them
+        // all in the linear case just to keep the code complexity
+        // down).
+        float values[6] = {
+            GrScalarToFloat(a * 4),
+            1.f / (GrScalarToFloat(a)),
+            GrScalarToFloat(centerX1),
+            GrScalarToFloat(radius0),
+            GrScalarToFloat(SkScalarMul(radius0, radius0)),
+            GrScalarToFloat(diffRadius)
+        };
+
+        GR_GL_CALL(gl, Uniform1fv(fVSParamLocation, 6, values));
+        GR_GL_CALL(gl, Uniform1fv(fFSParamLocation, 6, values));
+        fCachedCenter = centerX1;
+        fCachedRadius = radius0;
+        fCachedDiffRadius = diffRadius;
+    }
+}
+
+
+/////////////////////////////////////////////////////////////////////
+
+GrConical2Gradient::GrConical2Gradient(GrScalar center,
+                                       GrScalar radius,
+                                       GrScalar diffRadius)
+    : fCenterX1 (center)
+    , fRadius0 (radius)
+    , fDiffRadius (diffRadius) {
+
+}
+
+GrConical2Gradient::~GrConical2Gradient() {
+
+}
+
+
+const GrProgramStageFactory& GrConical2Gradient::getFactory() const {
+    return GrTProgramStageFactory<GrConical2Gradient>::getInstance();
+}
+
+bool GrConical2Gradient::isEqual(const GrCustomStage& sBase) const {
+    const GrConical2Gradient& s = static_cast<const GrConical2Gradient&>(sBase);
+    return (this->isDegenerate() == s.isDegenerate());
+}
+
+/////////////////////////////////////////////////////////////////////
+
+
 class GrGLSweepGradient : public GrGLProgramStage {
 
 public:
diff --git a/src/gpu/effects/GrGradientEffects.h b/src/gpu/effects/GrGradientEffects.h
index 9bcf9dd772..cf6827f251 100644
--- a/src/gpu/effects/GrGradientEffects.h
+++ b/src/gpu/effects/GrGradientEffects.h
@@ -92,6 +92,44 @@ private:
     typedef GrCustomStage INHERITED;
 };
 
+class GrGLConical2Gradient;
+
+class GrConical2Gradient : public GrCustomStage {
+
+public:
+
+    GrConical2Gradient(GrScalar center, GrScalar radius, GrScalar diffRadius);
+    virtual ~GrConical2Gradient();
+
+    static const char* Name() { return "Two-Point Conical Gradient"; }
+    virtual const GrProgramStageFactory& getFactory() const SK_OVERRIDE;
+    virtual bool isEqual(const GrCustomStage&) const SK_OVERRIDE;
+
+    // The radial gradient parameters can collapse to a linear (instead
+    // of quadratic) equation.
+    bool isDegenerate() const { return SkScalarAbs(fDiffRadius) == 
+                                       SkScalarAbs(fCenterX1); }
+    GrScalar center() const { return fCenterX1; }
+    GrScalar diffRadius() const { return fDiffRadius; }
+    GrScalar radius() const { return fRadius0; }
+
+    typedef GrGLConical2Gradient GLProgramStage;
+
+private:
+
+    // @{
+    // Cache of values - these can change arbitrarily, EXCEPT
+    // we shouldn't change between degenerate and non-degenerate?!
+
+    GrScalar fCenterX1;
+    GrScalar fRadius0;
+    GrScalar fDiffRadius;
+
+    // @}
+
+    typedef GrCustomStage INHERITED;
+};
+
 class GrGLSweepGradient;
 
 class GrSweepGradient : public GrCustomStage {