src/effects/gradients/SkTwoPointConicalGradient_gpu.cpp - platform/external/skqp - Gitiles

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #include "SkTwoPointConicalGradient_gpu.h"

 #include "SkTwoPointConicalGradient.h"

 #if SK_SUPPORT_GPU
 #include "GrTBackendEffectFactory.h"
 // For brevity
 typedef GrGLUniformManager::UniformHandle UniformHandle;

 //////////////////////////////////////////////////////////////////////////////

 static void set_matrix_default_conical(const SkTwoPointConicalGradient& shader,
                                        SkMatrix* invLMatrix) {
     // Inverse of the current local matrix is passed in then,
     // translate to center1, rotate so center2 is on x axis.
     const SkPoint& center1 = shader.getStartCenter();
     const SkPoint& center2 = shader.getEndCenter();

     invLMatrix->postTranslate(-center1.fX, -center1.fY);

     SkPoint diff = center2 - center1;
     SkScalar diffLen = diff.length();
     if (0 != diffLen) {
         SkScalar invDiffLen = SkScalarInvert(diffLen);
         SkMatrix rot;
         rot.setSinCos(-SkScalarMul(invDiffLen, diff.fY),
                        SkScalarMul(invDiffLen, diff.fX));
         invLMatrix->postConcat(rot);
     }
 }

 class GLDefault2PtConicalEffect;

 class Default2PtConicalEffect : public GrGradientEffect {
 public:

     static GrEffectRef* Create(GrContext* ctx,
                                const SkTwoPointConicalGradient& shader,
                                const SkMatrix& matrix,
                                SkShader::TileMode tm) {
         AutoEffectUnref effect(SkNEW_ARGS(Default2PtConicalEffect, (ctx, shader, matrix, tm)));
         return CreateEffectRef(effect);
     }

     virtual ~Default2PtConicalEffect() { }

     static const char* Name() { return "Two-Point Conical Gradient"; }
     virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;

     // The radial gradient parameters can collapse to a linear (instead of quadratic) equation.
     bool isDegenerate() const { return SkScalarAbs(fDiffRadius) == SkScalarAbs(fCenterX1); }
     SkScalar center() const { return fCenterX1; }
     SkScalar diffRadius() const { return fDiffRadius; }
     SkScalar radius() const { return fRadius0; }

     typedef GLDefault2PtConicalEffect GLEffect;

 private:
     virtual bool onIsEqual(const GrEffect& sBase) const SK_OVERRIDE {
         const Default2PtConicalEffect& s = CastEffect<Default2PtConicalEffect>(sBase);
         return (INHERITED::onIsEqual(sBase) &&
                 this->fCenterX1 == s.fCenterX1 &&
                 this->fRadius0 == s.fRadius0 &&
                 this->fDiffRadius == s.fDiffRadius);
     }

     Default2PtConicalEffect(GrContext* ctx,
                             const SkTwoPointConicalGradient& shader,
                             const SkMatrix& matrix,
                             SkShader::TileMode tm)
         : INHERITED(ctx, shader, matrix, tm),
         fCenterX1(shader.getCenterX1()),
         fRadius0(shader.getStartRadius()),
         fDiffRadius(shader.getDiffRadius()) {
         // We pass the linear part of the quadratic as a varying.
         //    float b = -2.0 * (fCenterX1 * x + fRadius0 * fDiffRadius * z)
         fBTransform = this->getCoordTransform();
         SkMatrix& bMatrix = *fBTransform.accessMatrix();
         SkScalar r0dr = SkScalarMul(fRadius0, fDiffRadius);
         bMatrix[SkMatrix::kMScaleX] = -2 * (SkScalarMul(fCenterX1, bMatrix[SkMatrix::kMScaleX]) +
                                             SkScalarMul(r0dr, bMatrix[SkMatrix::kMPersp0]));
         bMatrix[SkMatrix::kMSkewX] = -2 * (SkScalarMul(fCenterX1, bMatrix[SkMatrix::kMSkewX]) +
                                            SkScalarMul(r0dr, bMatrix[SkMatrix::kMPersp1]));
         bMatrix[SkMatrix::kMTransX] = -2 * (SkScalarMul(fCenterX1, bMatrix[SkMatrix::kMTransX]) +
                                             SkScalarMul(r0dr, bMatrix[SkMatrix::kMPersp2]));
         this->addCoordTransform(&fBTransform);
     }

     GR_DECLARE_EFFECT_TEST;

     // @{
     // Cache of values - these can change arbitrarily, EXCEPT
     // we shouldn't change between degenerate and non-degenerate?!

     GrCoordTransform fBTransform;
     SkScalar         fCenterX1;
     SkScalar         fRadius0;
     SkScalar         fDiffRadius;

     // @}

     typedef GrGradientEffect INHERITED;
 };

 class GLDefault2PtConicalEffect : public GrGLGradientEffect {
 public:
     GLDefault2PtConicalEffect(const GrBackendEffectFactory& factory, const GrDrawEffect&);
     virtual ~GLDefault2PtConicalEffect() { }

     virtual void emitCode(GrGLShaderBuilder*,
                           const GrDrawEffect&,
                           EffectKey,
                           const char* outputColor,
                           const char* inputColor,
                           const TransformedCoordsArray&,
                           const TextureSamplerArray&) SK_OVERRIDE;
     virtual void setData(const GrGLUniformManager&, const GrDrawEffect&) SK_OVERRIDE;

     static EffectKey GenKey(const GrDrawEffect&, const GrGLCaps& caps);

 protected:
     UniformHandle fParamUni;

     const char* fVSVaryingName;
     const char* fFSVaryingName;

     bool fIsDegenerate;

     // @{
     /// Values last uploaded as uniforms

     SkScalar fCachedCenter;
     SkScalar fCachedRadius;
     SkScalar fCachedDiffRadius;

     // @}

 private:
     typedef GrGLGradientEffect INHERITED;

 };

 const GrBackendEffectFactory& Default2PtConicalEffect::getFactory() const {
     return GrTBackendEffectFactory<Default2PtConicalEffect>::getInstance();
 }

 GR_DEFINE_EFFECT_TEST(Default2PtConicalEffect);

 GrEffectRef* Default2PtConicalEffect::TestCreate(SkRandom* random,
                                             GrContext* context,
                                             const GrDrawTargetCaps&,
                                             GrTexture**) {
     SkPoint center1 = {random->nextUScalar1(), random->nextUScalar1()};
     SkScalar radius1 = random->nextUScalar1();
     SkPoint center2;
     SkScalar radius2;
     do {
         center2.set(random->nextUScalar1(), random->nextUScalar1());
         radius2 = random->nextUScalar1 ();
         // If the circles are identical the factory will give us an empty shader.
     } while (radius1 == radius2 && center1 == center2);

     SkColor colors[kMaxRandomGradientColors];
     SkScalar stopsArray[kMaxRandomGradientColors];
     SkScalar* stops = stopsArray;
     SkShader::TileMode tm;
     int colorCount = RandomGradientParams(random, colors, &stops, &tm);
     SkAutoTUnref<SkShader> shader(SkGradientShader::CreateTwoPointConical(center1, radius1,
                                                                           center2, radius2,
                                                                           colors, stops, colorCount,
                                                                           tm));
     SkPaint paint;
     return shader->asNewEffect(context, paint);
 }


 /////////////////////////////////////////////////////////////////////

 GLDefault2PtConicalEffect::GLDefault2PtConicalEffect(const GrBackendEffectFactory& factory,
                                            const GrDrawEffect& drawEffect)
     : INHERITED(factory)
     , fVSVaryingName(NULL)
     , fFSVaryingName(NULL)
     , fCachedCenter(SK_ScalarMax)
     , fCachedRadius(-SK_ScalarMax)
     , fCachedDiffRadius(-SK_ScalarMax) {

     const Default2PtConicalEffect& data = drawEffect.castEffect<Default2PtConicalEffect>();
     fIsDegenerate = data.isDegenerate();
 }

 void GLDefault2PtConicalEffect::emitCode(GrGLShaderBuilder* builder,
                                     const GrDrawEffect&,
                                     EffectKey key,
                                     const char* outputColor,
                                     const char* inputColor,
                                     const TransformedCoordsArray& coords,
                                     const TextureSamplerArray& samplers) {
     this->emitUniforms(builder, key);
     fParamUni = builder->addUniformArray(GrGLShaderBuilder::kFragment_Visibility,
                                          kFloat_GrSLType, "Conical2FSParams", 6);

     SkString cName("c");
     SkString ac4Name("ac4");
     SkString dName("d");
     SkString qName("q");
     SkString r0Name("r0");
     SkString r1Name("r1");
     SkString tName("t");
     SkString p0; // 4a
     SkString p1; // 1/a
     SkString p2; // distance between centers
     SkString p3; // start radius
     SkString p4; // start radius squared
     SkString p5; // difference in radii (r1 - r0)

     builder->getUniformVariable(fParamUni).appendArrayAccess(0, &p0);
     builder->getUniformVariable(fParamUni).appendArrayAccess(1, &p1);
     builder->getUniformVariable(fParamUni).appendArrayAccess(2, &p2);
     builder->getUniformVariable(fParamUni).appendArrayAccess(3, &p3);
     builder->getUniformVariable(fParamUni).appendArrayAccess(4, &p4);
     builder->getUniformVariable(fParamUni).appendArrayAccess(5, &p5);

     // We interpolate the linear component in coords[1].
     SkASSERT(coords[0].type() == coords[1].type());
     const char* coords2D;
     SkString bVar;
     if (kVec3f_GrSLType == coords[0].type()) {
         builder->fsCodeAppendf("\tvec3 interpolants = vec3(%s.xy, %s.x) / %s.z;\n",
                                coords[0].c_str(), coords[1].c_str(), coords[0].c_str());
         coords2D = "interpolants.xy";
         bVar = "interpolants.z";
     } else {
         coords2D = coords[0].c_str();
         bVar.printf("%s.x", coords[1].c_str());
     }

     // output will default to transparent black (we simply won't write anything
     // else to it if invalid, instead of discarding or returning prematurely)
     builder->fsCodeAppendf("\t%s = vec4(0.0,0.0,0.0,0.0);\n", outputColor);

     // c = (x^2)+(y^2) - params[4]
     builder->fsCodeAppendf("\tfloat %s = dot(%s, %s) - %s;\n",
                            cName.c_str(), coords2D, coords2D, p4.c_str());

     // Non-degenerate case (quadratic)
     if (!fIsDegenerate) {

         // ac4 = params[0] * c
         builder->fsCodeAppendf("\tfloat %s = %s * %s;\n", ac4Name.c_str(), p0.c_str(),
                                cName.c_str());

         // d = b^2 - ac4
         builder->fsCodeAppendf("\tfloat %s = %s * %s - %s;\n", dName.c_str(),
                                bVar.c_str(), bVar.c_str(), ac4Name.c_str());

         // only proceed if discriminant is >= 0
         builder->fsCodeAppendf("\tif (%s >= 0.0) {\n", dName.c_str());

         // intermediate value we'll use to compute the roots
         // q = -0.5 * (b +/- sqrt(d))
         builder->fsCodeAppendf("\t\tfloat %s = -0.5 * (%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]
         builder->fsCodeAppendf("\t\tfloat %s = %s * %s;\n", r0Name.c_str(),
                                qName.c_str(), p1.c_str());
         // r1 = c / q
         builder->fsCodeAppendf("\t\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:
         builder->fsCodeAppendf("\t\tfloat %s = max(%s, %s);\n", tName.c_str(),
                                r0Name.c_str(), r1Name.c_str());

         // if r(t) > 0, then we're done; t will be our x coordinate
         builder->fsCodeAppendf("\t\tif (%s * %s + %s > 0.0) {\n", tName.c_str(),
                                p5.c_str(), p3.c_str());

         builder->fsCodeAppend("\t\t");
         this->emitColor(builder, tName.c_str(), key, outputColor, inputColor, samplers);

         // otherwise, if r(t) for the larger root was <= 0, try the other root
         builder->fsCodeAppend("\t\t} else {\n");
         builder->fsCodeAppendf("\t\t\t%s = min(%s, %s);\n", tName.c_str(),
                                r0Name.c_str(), r1Name.c_str());

         // if r(t) > 0 for the smaller root, then t will be our x coordinate
         builder->fsCodeAppendf("\t\t\tif (%s * %s + %s > 0.0) {\n",
                                tName.c_str(), p5.c_str(), p3.c_str());

         builder->fsCodeAppend("\t\t\t");
         this->emitColor(builder, tName.c_str(), key, outputColor, inputColor, samplers);

         // end if (r(t) > 0) for smaller root
         builder->fsCodeAppend("\t\t\t}\n");
         // end if (r(t) > 0), else, for larger root
         builder->fsCodeAppend("\t\t}\n");
         // end if (discriminant >= 0)
         builder->fsCodeAppend("\t}\n");
     } else {

         // linear case: t = -c/b
         builder->fsCodeAppendf("\tfloat %s = -(%s / %s);\n", tName.c_str(),
                                cName.c_str(), bVar.c_str());

         // if r(t) > 0, then t will be the x coordinate
         builder->fsCodeAppendf("\tif (%s * %s + %s > 0.0) {\n", tName.c_str(),
                                p5.c_str(), p3.c_str());
         builder->fsCodeAppend("\t");
         this->emitColor(builder, tName.c_str(), key, outputColor, inputColor, samplers);
         builder->fsCodeAppend("\t}\n");
     }
 }

 void GLDefault2PtConicalEffect::setData(const GrGLUniformManager& uman,
                                    const GrDrawEffect& drawEffect) {
     INHERITED::setData(uman, drawEffect);
     const Default2PtConicalEffect& data = drawEffect.castEffect<Default2PtConicalEffect>();
     SkASSERT(data.isDegenerate() == fIsDegenerate);
     SkScalar centerX1 = data.center();
     SkScalar radius0 = data.radius();
     SkScalar diffRadius = data.diffRadius();

     if (fCachedCenter != centerX1 ||
         fCachedRadius != radius0 ||
         fCachedDiffRadius != diffRadius) {

         SkScalar a = SkScalarMul(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] = {
             SkScalarToFloat(a * 4),
             1.f / (SkScalarToFloat(a)),
             SkScalarToFloat(centerX1),
             SkScalarToFloat(radius0),
             SkScalarToFloat(SkScalarMul(radius0, radius0)),
             SkScalarToFloat(diffRadius)
         };

         uman.set1fv(fParamUni, 6, values);
         fCachedCenter = centerX1;
         fCachedRadius = radius0;
         fCachedDiffRadius = diffRadius;
     }
 }

 GrGLEffect::EffectKey GLDefault2PtConicalEffect::GenKey(const GrDrawEffect& drawEffect,
                                                    const GrGLCaps&) {
     enum {
         kIsDegenerate = 1 << kBaseKeyBitCnt,
     };

     EffectKey key = GenBaseGradientKey(drawEffect);
     if (drawEffect.castEffect<Default2PtConicalEffect>().isDegenerate()) {
         key |= kIsDegenerate;
     }
     return key;
 }

 //////////////////////////////////////////////////////////////////////////////

 GrEffectRef* Gr2PtConicalGradientEffect::Create(GrContext* ctx,
                                                 const SkTwoPointConicalGradient& shader,
                                                 SkShader::TileMode tm) {

     SkMatrix matrix;
     if (!shader.getLocalMatrix().invert(&matrix)) {
         return NULL;
     }

     set_matrix_default_conical(shader, &matrix);
     return Default2PtConicalEffect::Create(ctx, shader, matrix, tm);
 }

 #endif
	/*
	* Copyright 2014 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#include "SkTwoPointConicalGradient_gpu.h"

	#include "SkTwoPointConicalGradient.h"

	#if SK_SUPPORT_GPU
	#include "GrTBackendEffectFactory.h"
	// For brevity
	typedef GrGLUniformManager::UniformHandle UniformHandle;

	//////////////////////////////////////////////////////////////////////////////

	static void set_matrix_default_conical(const SkTwoPointConicalGradient& shader,
	SkMatrix* invLMatrix) {
	// Inverse of the current local matrix is passed in then,
	// translate to center1, rotate so center2 is on x axis.
	const SkPoint& center1 = shader.getStartCenter();
	const SkPoint& center2 = shader.getEndCenter();

	invLMatrix->postTranslate(-center1.fX, -center1.fY);

	SkPoint diff = center2 - center1;
	SkScalar diffLen = diff.length();
	if (0 != diffLen) {
	SkScalar invDiffLen = SkScalarInvert(diffLen);
	SkMatrix rot;
	rot.setSinCos(-SkScalarMul(invDiffLen, diff.fY),
	SkScalarMul(invDiffLen, diff.fX));
	invLMatrix->postConcat(rot);
	}
	}

	class GLDefault2PtConicalEffect;

	class Default2PtConicalEffect : public GrGradientEffect {
	public:

	static GrEffectRef* Create(GrContext* ctx,
	const SkTwoPointConicalGradient& shader,
	const SkMatrix& matrix,
	SkShader::TileMode tm) {
	AutoEffectUnref effect(SkNEW_ARGS(Default2PtConicalEffect, (ctx, shader, matrix, tm)));
	return CreateEffectRef(effect);
	}

	virtual ~Default2PtConicalEffect() { }

	static const char* Name() { return "Two-Point Conical Gradient"; }
	virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;

	// The radial gradient parameters can collapse to a linear (instead of quadratic) equation.
	bool isDegenerate() const { return SkScalarAbs(fDiffRadius) == SkScalarAbs(fCenterX1); }
	SkScalar center() const { return fCenterX1; }
	SkScalar diffRadius() const { return fDiffRadius; }
	SkScalar radius() const { return fRadius0; }

	typedef GLDefault2PtConicalEffect GLEffect;

	private:
	virtual bool onIsEqual(const GrEffect& sBase) const SK_OVERRIDE {
	const Default2PtConicalEffect& s = CastEffect<Default2PtConicalEffect>(sBase);
	return (INHERITED::onIsEqual(sBase) &&
	this->fCenterX1 == s.fCenterX1 &&
	this->fRadius0 == s.fRadius0 &&
	this->fDiffRadius == s.fDiffRadius);
	}

	Default2PtConicalEffect(GrContext* ctx,
	const SkTwoPointConicalGradient& shader,
	const SkMatrix& matrix,
	SkShader::TileMode tm)
	: INHERITED(ctx, shader, matrix, tm),
	fCenterX1(shader.getCenterX1()),
	fRadius0(shader.getStartRadius()),
	fDiffRadius(shader.getDiffRadius()) {
	// We pass the linear part of the quadratic as a varying.
	// float b = -2.0 * (fCenterX1 * x + fRadius0 * fDiffRadius * z)
	fBTransform = this->getCoordTransform();
	SkMatrix& bMatrix = *fBTransform.accessMatrix();
	SkScalar r0dr = SkScalarMul(fRadius0, fDiffRadius);
	bMatrix[SkMatrix::kMScaleX] = -2 * (SkScalarMul(fCenterX1, bMatrix[SkMatrix::kMScaleX]) +
	SkScalarMul(r0dr, bMatrix[SkMatrix::kMPersp0]));
	bMatrix[SkMatrix::kMSkewX] = -2 * (SkScalarMul(fCenterX1, bMatrix[SkMatrix::kMSkewX]) +
	SkScalarMul(r0dr, bMatrix[SkMatrix::kMPersp1]));
	bMatrix[SkMatrix::kMTransX] = -2 * (SkScalarMul(fCenterX1, bMatrix[SkMatrix::kMTransX]) +
	SkScalarMul(r0dr, bMatrix[SkMatrix::kMPersp2]));
	this->addCoordTransform(&fBTransform);
	}

	GR_DECLARE_EFFECT_TEST;

	// @{
	// Cache of values - these can change arbitrarily, EXCEPT
	// we shouldn't change between degenerate and non-degenerate?!

	GrCoordTransform fBTransform;
	SkScalar fCenterX1;
	SkScalar fRadius0;
	SkScalar fDiffRadius;

	// @}

	typedef GrGradientEffect INHERITED;
	};

	class GLDefault2PtConicalEffect : public GrGLGradientEffect {
	public:
	GLDefault2PtConicalEffect(const GrBackendEffectFactory& factory, const GrDrawEffect&);
	virtual ~GLDefault2PtConicalEffect() { }

	virtual void emitCode(GrGLShaderBuilder*,
	const GrDrawEffect&,
	EffectKey,
	const char* outputColor,
	const char* inputColor,
	const TransformedCoordsArray&,
	const TextureSamplerArray&) SK_OVERRIDE;
	virtual void setData(const GrGLUniformManager&, const GrDrawEffect&) SK_OVERRIDE;

	static EffectKey GenKey(const GrDrawEffect&, const GrGLCaps& caps);

	protected:
	UniformHandle fParamUni;

	const char* fVSVaryingName;
	const char* fFSVaryingName;

	bool fIsDegenerate;

	// @{
	/// Values last uploaded as uniforms

	SkScalar fCachedCenter;
	SkScalar fCachedRadius;
	SkScalar fCachedDiffRadius;

	// @}

	private:
	typedef GrGLGradientEffect INHERITED;

	};

	const GrBackendEffectFactory& Default2PtConicalEffect::getFactory() const {
	return GrTBackendEffectFactory<Default2PtConicalEffect>::getInstance();
	}

	GR_DEFINE_EFFECT_TEST(Default2PtConicalEffect);

	GrEffectRef* Default2PtConicalEffect::TestCreate(SkRandom* random,
	GrContext* context,
	const GrDrawTargetCaps&,
	GrTexture**) {
	SkPoint center1 = {random->nextUScalar1(), random->nextUScalar1()};
	SkScalar radius1 = random->nextUScalar1();
	SkPoint center2;
	SkScalar radius2;
	do {
	center2.set(random->nextUScalar1(), random->nextUScalar1());
	radius2 = random->nextUScalar1 ();
	// If the circles are identical the factory will give us an empty shader.
	} while (radius1 == radius2 && center1 == center2);

	SkColor colors[kMaxRandomGradientColors];
	SkScalar stopsArray[kMaxRandomGradientColors];
	SkScalar* stops = stopsArray;
	SkShader::TileMode tm;
	int colorCount = RandomGradientParams(random, colors, &stops, &tm);
	SkAutoTUnref<SkShader> shader(SkGradientShader::CreateTwoPointConical(center1, radius1,
	center2, radius2,
	colors, stops, colorCount,
	tm));
	SkPaint paint;
	return shader->asNewEffect(context, paint);
	}


	/////////////////////////////////////////////////////////////////////

	GLDefault2PtConicalEffect::GLDefault2PtConicalEffect(const GrBackendEffectFactory& factory,
	const GrDrawEffect& drawEffect)
	: INHERITED(factory)
	, fVSVaryingName(NULL)
	, fFSVaryingName(NULL)
	, fCachedCenter(SK_ScalarMax)
	, fCachedRadius(-SK_ScalarMax)
	, fCachedDiffRadius(-SK_ScalarMax) {

	const Default2PtConicalEffect& data = drawEffect.castEffect<Default2PtConicalEffect>();
	fIsDegenerate = data.isDegenerate();
	}

	void GLDefault2PtConicalEffect::emitCode(GrGLShaderBuilder* builder,
	const GrDrawEffect&,
	EffectKey key,
	const char* outputColor,
	const char* inputColor,
	const TransformedCoordsArray& coords,
	const TextureSamplerArray& samplers) {
	this->emitUniforms(builder, key);
	fParamUni = builder->addUniformArray(GrGLShaderBuilder::kFragment_Visibility,
	kFloat_GrSLType, "Conical2FSParams", 6);

	SkString cName("c");
	SkString ac4Name("ac4");
	SkString dName("d");
	SkString qName("q");
	SkString r0Name("r0");
	SkString r1Name("r1");
	SkString tName("t");
	SkString p0; // 4a
	SkString p1; // 1/a
	SkString p2; // distance between centers
	SkString p3; // start radius
	SkString p4; // start radius squared
	SkString p5; // difference in radii (r1 - r0)

	builder->getUniformVariable(fParamUni).appendArrayAccess(0, &p0);
	builder->getUniformVariable(fParamUni).appendArrayAccess(1, &p1);
	builder->getUniformVariable(fParamUni).appendArrayAccess(2, &p2);
	builder->getUniformVariable(fParamUni).appendArrayAccess(3, &p3);
	builder->getUniformVariable(fParamUni).appendArrayAccess(4, &p4);
	builder->getUniformVariable(fParamUni).appendArrayAccess(5, &p5);

	// We interpolate the linear component in coords[1].
	SkASSERT(coords[0].type() == coords[1].type());
	const char* coords2D;
	SkString bVar;
	if (kVec3f_GrSLType == coords[0].type()) {
	builder->fsCodeAppendf("\tvec3 interpolants = vec3(%s.xy, %s.x) / %s.z;\n",
	coords[0].c_str(), coords[1].c_str(), coords[0].c_str());
	coords2D = "interpolants.xy";
	bVar = "interpolants.z";
	} else {
	coords2D = coords[0].c_str();
	bVar.printf("%s.x", coords[1].c_str());
	}

	// output will default to transparent black (we simply won't write anything
	// else to it if invalid, instead of discarding or returning prematurely)
	builder->fsCodeAppendf("\t%s = vec4(0.0,0.0,0.0,0.0);\n", outputColor);

	// c = (x^2)+(y^2) - params[4]
	builder->fsCodeAppendf("\tfloat %s = dot(%s, %s) - %s;\n",
	cName.c_str(), coords2D, coords2D, p4.c_str());

	// Non-degenerate case (quadratic)
	if (!fIsDegenerate) {

	// ac4 = params[0] * c
	builder->fsCodeAppendf("\tfloat %s = %s * %s;\n", ac4Name.c_str(), p0.c_str(),
	cName.c_str());

	// d = b^2 - ac4
	builder->fsCodeAppendf("\tfloat %s = %s * %s - %s;\n", dName.c_str(),
	bVar.c_str(), bVar.c_str(), ac4Name.c_str());

	// only proceed if discriminant is >= 0
	builder->fsCodeAppendf("\tif (%s >= 0.0) {\n", dName.c_str());

	// intermediate value we'll use to compute the roots
	// q = -0.5 * (b +/- sqrt(d))
	builder->fsCodeAppendf("\t\tfloat %s = -0.5 * (%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]
	builder->fsCodeAppendf("\t\tfloat %s = %s * %s;\n", r0Name.c_str(),
	qName.c_str(), p1.c_str());
	// r1 = c / q
	builder->fsCodeAppendf("\t\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:
	builder->fsCodeAppendf("\t\tfloat %s = max(%s, %s);\n", tName.c_str(),
	r0Name.c_str(), r1Name.c_str());

	// if r(t) > 0, then we're done; t will be our x coordinate
	builder->fsCodeAppendf("\t\tif (%s * %s + %s > 0.0) {\n", tName.c_str(),
	p5.c_str(), p3.c_str());

	builder->fsCodeAppend("\t\t");
	this->emitColor(builder, tName.c_str(), key, outputColor, inputColor, samplers);

	// otherwise, if r(t) for the larger root was <= 0, try the other root
	builder->fsCodeAppend("\t\t} else {\n");
	builder->fsCodeAppendf("\t\t\t%s = min(%s, %s);\n", tName.c_str(),
	r0Name.c_str(), r1Name.c_str());

	// if r(t) > 0 for the smaller root, then t will be our x coordinate
	builder->fsCodeAppendf("\t\t\tif (%s * %s + %s > 0.0) {\n",
	tName.c_str(), p5.c_str(), p3.c_str());

	builder->fsCodeAppend("\t\t\t");
	this->emitColor(builder, tName.c_str(), key, outputColor, inputColor, samplers);

	// end if (r(t) > 0) for smaller root
	builder->fsCodeAppend("\t\t\t}\n");
	// end if (r(t) > 0), else, for larger root
	builder->fsCodeAppend("\t\t}\n");
	// end if (discriminant >= 0)
	builder->fsCodeAppend("\t}\n");
	} else {

	// linear case: t = -c/b
	builder->fsCodeAppendf("\tfloat %s = -(%s / %s);\n", tName.c_str(),
	cName.c_str(), bVar.c_str());

	// if r(t) > 0, then t will be the x coordinate
	builder->fsCodeAppendf("\tif (%s * %s + %s > 0.0) {\n", tName.c_str(),
	p5.c_str(), p3.c_str());
	builder->fsCodeAppend("\t");
	this->emitColor(builder, tName.c_str(), key, outputColor, inputColor, samplers);
	builder->fsCodeAppend("\t}\n");
	}
	}

	void GLDefault2PtConicalEffect::setData(const GrGLUniformManager& uman,
	const GrDrawEffect& drawEffect) {
	INHERITED::setData(uman, drawEffect);
	const Default2PtConicalEffect& data = drawEffect.castEffect<Default2PtConicalEffect>();
	SkASSERT(data.isDegenerate() == fIsDegenerate);
	SkScalar centerX1 = data.center();
	SkScalar radius0 = data.radius();
	SkScalar diffRadius = data.diffRadius();

	if (fCachedCenter != centerX1 \|\|
	fCachedRadius != radius0 \|\|
	fCachedDiffRadius != diffRadius) {

	SkScalar a = SkScalarMul(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] = {
	SkScalarToFloat(a * 4),
	1.f / (SkScalarToFloat(a)),
	SkScalarToFloat(centerX1),
	SkScalarToFloat(radius0),
	SkScalarToFloat(SkScalarMul(radius0, radius0)),
	SkScalarToFloat(diffRadius)
	};

	uman.set1fv(fParamUni, 6, values);
	fCachedCenter = centerX1;
	fCachedRadius = radius0;
	fCachedDiffRadius = diffRadius;
	}
	}

	GrGLEffect::EffectKey GLDefault2PtConicalEffect::GenKey(const GrDrawEffect& drawEffect,
	const GrGLCaps&) {
	enum {
	kIsDegenerate = 1 << kBaseKeyBitCnt,
	};

	EffectKey key = GenBaseGradientKey(drawEffect);
	if (drawEffect.castEffect<Default2PtConicalEffect>().isDegenerate()) {
	key \|= kIsDegenerate;
	}
	return key;
	}

	//////////////////////////////////////////////////////////////////////////////

	GrEffectRef* Gr2PtConicalGradientEffect::Create(GrContext* ctx,
	const SkTwoPointConicalGradient& shader,
	SkShader::TileMode tm) {

	SkMatrix matrix;
	if (!shader.getLocalMatrix().invert(&matrix)) {
	return NULL;
	}

	set_matrix_default_conical(shader, &matrix);
	return Default2PtConicalEffect::Create(ctx, shader, matrix, tm);
	}

	#endif