src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp - platform/external/skia - 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 "src/gpu/GrRenderTarget.h"
 #include "src/gpu/GrShaderCaps.h"
 #include "src/gpu/gl/GrGLGpu.h"
 #include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
 #include "src/gpu/glsl/GrGLSLProgramBuilder.h"
 #include "src/gpu/glsl/GrGLSLUniformHandler.h"
 #include "src/gpu/glsl/GrGLSLVarying.h"

 const char* GrGLSLFragmentShaderBuilder::kDstColorName = "_dstColor";

 uint8_t GrGLSLFragmentShaderBuilder::KeyForSurfaceOrigin(GrSurfaceOrigin origin) {
     SkASSERT(kTopLeft_GrSurfaceOrigin == origin || kBottomLeft_GrSurfaceOrigin == origin);
     return origin + 1;

     static_assert(0 == kTopLeft_GrSurfaceOrigin);
     static_assert(1 == kBottomLeft_GrSurfaceOrigin);
 }

 GrGLSLFragmentShaderBuilder::GrGLSLFragmentShaderBuilder(GrGLSLProgramBuilder* program)
         : GrGLSLShaderBuilder(program) {
     fSubstageIndices.push_back(0);
 }

 const char* GrGLSLFragmentShaderBuilder::sampleOffsets() {
     SkASSERT(CustomFeatures::kSampleLocations & fProgramBuilder->processorFeatures());
     SkDEBUGCODE(fUsedProcessorFeaturesThisStage_DebugOnly |= CustomFeatures::kSampleLocations);
     SkDEBUGCODE(fUsedProcessorFeaturesAllStages_DebugOnly |= CustomFeatures::kSampleLocations);
     return "_sampleOffsets";
 }

 void GrGLSLFragmentShaderBuilder::maskOffMultisampleCoverage(
         const char* mask, ScopeFlags scopeFlags) {
     const GrShaderCaps& shaderCaps = *fProgramBuilder->shaderCaps();
     if (!shaderCaps.sampleMaskSupport()) {
         SkDEBUGFAIL("Attempted to mask sample coverage without support.");
         return;
     }
     if (const char* extension = shaderCaps.sampleVariablesExtensionString()) {
         this->addFeature(1 << kSampleVariables_GLSLPrivateFeature, extension);
     }

     if (!fHasModifiedSampleMask) {
         fHasModifiedSampleMask = true;
         if (ScopeFlags::kTopLevel != scopeFlags) {
             this->codePrependf("sk_SampleMask[0] = ~0;");
         }
         if (!(ScopeFlags::kInsideLoop & scopeFlags)) {
             this->codeAppendf("sk_SampleMask[0] = (%s);", mask);
             return;
         }
     }

     this->codeAppendf("sk_SampleMask[0] &= (%s);", mask);
 }

 void GrGLSLFragmentShaderBuilder::applyFnToMultisampleMask(
         const char* fn, const char* grad, ScopeFlags scopeFlags) {
     SkASSERT(CustomFeatures::kSampleLocations & fProgramBuilder->processorFeatures());
     SkDEBUGCODE(fUsedProcessorFeaturesThisStage_DebugOnly |= CustomFeatures::kSampleLocations);
     SkDEBUGCODE(fUsedProcessorFeaturesAllStages_DebugOnly |= CustomFeatures::kSampleLocations);

     int sampleCnt = fProgramBuilder->effectiveSampleCnt();
     SkASSERT(sampleCnt > 1);

     this->codeAppendf("{");

     if (!grad) {
         SkASSERT(fProgramBuilder->shaderCaps()->shaderDerivativeSupport());
         // In order to use HW derivatives, our neighbors within the same primitive must also be
         // executing the same code. A per-pixel branch makes this pre-condition impossible to
         // fulfill.
         SkASSERT(!(ScopeFlags::kInsidePerPixelBranch & scopeFlags));
         this->codeAppendf("float2 grad = float2(dFdx(%s), dFdy(%s));", fn, fn);
         this->codeAppendf("float fnwidth = fwidth(%s);", fn);
         grad = "grad";
     } else {
         this->codeAppendf("float fnwidth = abs(%s.x) + abs(%s.y);", grad, grad);
     }

     this->codeAppendf("int mask = 0;");
     this->codeAppendf("if (%s*2 < fnwidth) {", fn);  // Are ANY samples inside the implicit fn?
     this->codeAppendf(    "if (%s*-2 >= fnwidth) {", fn);  // Are ALL samples inside the implicit?
     this->codeAppendf(        "mask = ~0;");
     this->codeAppendf(    "} else for (int i = 0; i < %i; ++i) {", sampleCnt);
     this->codeAppendf(        "float fnsample = dot(%s, _sampleOffsets[i]) + %s;", grad, fn);
     this->codeAppendf(        "if (fnsample < 0) {");
     this->codeAppendf(            "mask |= (1 << i);");
     this->codeAppendf(        "}");
     this->codeAppendf(    "}");
     this->codeAppendf("}");
     this->maskOffMultisampleCoverage("mask", scopeFlags);

     this->codeAppendf("}");
 }

 SkString GrGLSLFPFragmentBuilder::writeProcessorFunction(GrGLSLFragmentProcessor* fp,
                                                          GrGLSLFragmentProcessor::EmitArgs& args) {
     this->onBeforeChildProcEmitCode();
     this->nextStage();

     // An FP's function signature is theoretically always main(half4 color, float2 _coords).
     // However, if it is only sampled by a chain of uniform matrix expressions (or legacy coord
     // transforms), the value that would have been passed to _coords is lifted to the vertex shader
     // and stored in a unique varying. In that case it uses that variable and does not have a
     // second actual argument for _coords.
     // FIXME: An alternative would be to have all FP functions have a float2 argument, and the
     // parent FP invokes it with the varying reference when it's been lifted to the vertex shader.
     size_t paramCount = 2;
     GrShaderVar params[] = { GrShaderVar(args.fInputColor, kHalf4_GrSLType),
                              GrShaderVar(args.fSampleCoord, kFloat2_GrSLType) };

     if (!args.fFp.isSampledWithExplicitCoords()) {
         // Sampled with a uniform matrix expression and/or a legacy coord transform. The actual
         // transformation code is emitted in the vertex shader, so this only has to access it.
         // Add a float2 _coords variable that maps to the associated varying and replaces the
         // absent 2nd argument to the fp's function.
         paramCount = 1;

         if (args.fFp.referencesSampleCoords()) {
             const GrShaderVar& varying = args.fTransformedCoords[0];
             switch(varying.getType()) {
                 case kFloat2_GrSLType:
                     // Just point the local coords to the varying
                     args.fSampleCoord = varying.getName().c_str();
                     break;
                 case kFloat3_GrSLType:
                     // Must perform the perspective divide in the frag shader based on the varying,
                     // and since we won't actually have a function parameter for local coords, add
                     // it as a local variable.
                     this->codeAppendf("float2 %s = %s.xy / %s.z;\n", args.fSampleCoord,
                                       varying.getName().c_str(), varying.getName().c_str());
                     break;
                 default:
                     SkDEBUGFAILF("Unexpected varying type for coord: %s %d\n",
                                  varying.getName().c_str(), (int) varying.getType());
                     break;
             }
         }
     } // else the function keeps its two arguments

     fp->emitCode(args);

     SkString funcName = this->getMangledFunctionName(args.fFp.name());
     this->emitFunction(kHalf4_GrSLType, funcName.c_str(), {params, paramCount},
                        this->code().c_str());
     this->deleteStage();
     this->onAfterChildProcEmitCode();
     return funcName;
 }

 const char* GrGLSLFragmentShaderBuilder::dstColor() {
     SkDEBUGCODE(fHasReadDstColorThisStage_DebugOnly = true;)

     const GrShaderCaps* shaderCaps = fProgramBuilder->shaderCaps();
     if (shaderCaps->fbFetchSupport()) {
         this->addFeature(1 << kFramebufferFetch_GLSLPrivateFeature,
                          shaderCaps->fbFetchExtensionString());

         // Some versions of this extension string require declaring custom color output on ES 3.0+
         const char* fbFetchColorName = "sk_LastFragColor";
         if (shaderCaps->fbFetchNeedsCustomOutput()) {
             this->enableCustomOutput();
             fCustomColorOutput->setTypeModifier(GrShaderVar::TypeModifier::InOut);
             fbFetchColorName = DeclaredColorOutputName();
             // Set the dstColor to an intermediate variable so we don't override it with the output
             this->codeAppendf("half4 %s = %s;", kDstColorName, fbFetchColorName);
         } else {
             return fbFetchColorName;
         }
     }
     return kDstColorName;
 }

 void GrGLSLFragmentShaderBuilder::enableAdvancedBlendEquationIfNeeded(GrBlendEquation equation) {
     SkASSERT(GrBlendEquationIsAdvanced(equation));

     if (fProgramBuilder->shaderCaps()->mustEnableAdvBlendEqs()) {
         this->addFeature(1 << kBlendEquationAdvanced_GLSLPrivateFeature,
                          "GL_KHR_blend_equation_advanced");
         this->addLayoutQualifier("blend_support_all_equations", kOut_InterfaceQualifier);
     }
 }

 void GrGLSLFragmentShaderBuilder::enableCustomOutput() {
     if (!fCustomColorOutput) {
         fCustomColorOutput = &fOutputs.emplace_back(DeclaredColorOutputName(), kHalf4_GrSLType,
                                                     GrShaderVar::TypeModifier::Out);
         fProgramBuilder->finalizeFragmentOutputColor(fOutputs.back());
     }
 }

 void GrGLSLFragmentShaderBuilder::enableSecondaryOutput() {
     SkASSERT(!fHasSecondaryOutput);
     fHasSecondaryOutput = true;
     const GrShaderCaps& caps = *fProgramBuilder->shaderCaps();
     if (const char* extension = caps.secondaryOutputExtensionString()) {
         this->addFeature(1 << kBlendFuncExtended_GLSLPrivateFeature, extension);
     }

     // If the primary output is declared, we must declare also the secondary output
     // and vice versa, since it is not allowed to use a built-in gl_FragColor and a custom
     // output. The condition also co-incides with the condition in which GLES SL 2.0
     // requires the built-in gl_SecondaryFragColorEXT, where as 3.0 requires a custom output.
     if (caps.mustDeclareFragmentShaderOutput()) {
         fOutputs.emplace_back(DeclaredSecondaryColorOutputName(), kHalf4_GrSLType,
                               GrShaderVar::TypeModifier::Out);
         fProgramBuilder->finalizeFragmentSecondaryColor(fOutputs.back());
     }
 }

 const char* GrGLSLFragmentShaderBuilder::getPrimaryColorOutputName() const {
     return this->hasCustomColorOutput() ? DeclaredColorOutputName() : "sk_FragColor";
 }

 bool GrGLSLFragmentShaderBuilder::primaryColorOutputIsInOut() const {
     return fCustomColorOutput &&
            fCustomColorOutput->getTypeModifier() == GrShaderVar::TypeModifier::InOut;
 }

 const char* GrGLSLFragmentShaderBuilder::getSecondaryColorOutputName() const {
     if (this->hasSecondaryOutput()) {
         return (fProgramBuilder->shaderCaps()->mustDeclareFragmentShaderOutput())
                 ? DeclaredSecondaryColorOutputName()
                 : "gl_SecondaryFragColorEXT";
     }
     return nullptr;
 }

 GrSurfaceOrigin GrGLSLFragmentShaderBuilder::getSurfaceOrigin() const {
     return fProgramBuilder->origin();
 }

 void GrGLSLFragmentShaderBuilder::onFinalize() {
     SkASSERT(fProgramBuilder->processorFeatures() == fUsedProcessorFeaturesAllStages_DebugOnly);

     if (CustomFeatures::kSampleLocations & fProgramBuilder->processorFeatures()) {
         const SkTArray<SkPoint>& sampleLocations = fProgramBuilder->getSampleLocations();
         this->definitions().appendf("const float2 _sampleOffsets[%i] = float2[%i](",
                                     sampleLocations.count(), sampleLocations.count());
         for (int i = 0; i < sampleLocations.count(); ++i) {
             SkPoint offset = sampleLocations[i] - SkPoint::Make(.5f, .5f);
             if (kBottomLeft_GrSurfaceOrigin == this->getSurfaceOrigin()) {
                 offset.fY = -offset.fY;
             }
             this->definitions().appendf("float2(%f, %f)", offset.x(), offset.y());
             this->definitions().append((i + 1 != sampleLocations.count()) ? ", " : ");");
         }
     }

     fProgramBuilder->varyingHandler()->getFragDecls(&this->inputs(), &this->outputs());
 }

 void GrGLSLFragmentShaderBuilder::onBeforeChildProcEmitCode() {
     SkASSERT(fSubstageIndices.count() >= 1);
     fSubstageIndices.push_back(0);
     // second-to-last value in the fSubstageIndices stack is the index of the child proc
     // at that level which is currently emitting code.
     fMangleString.appendf("_c%d", fSubstageIndices[fSubstageIndices.count() - 2]);
 }

 void GrGLSLFragmentShaderBuilder::onAfterChildProcEmitCode() {
     SkASSERT(fSubstageIndices.count() >= 2);
     fSubstageIndices.pop_back();
     fSubstageIndices.back()++;
     int removeAt = fMangleString.findLastOf('_');
     fMangleString.remove(removeAt, fMangleString.size() - removeAt);
 }
	/*
	* 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 "src/gpu/GrRenderTarget.h"
	#include "src/gpu/GrShaderCaps.h"
	#include "src/gpu/gl/GrGLGpu.h"
	#include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
	#include "src/gpu/glsl/GrGLSLProgramBuilder.h"
	#include "src/gpu/glsl/GrGLSLUniformHandler.h"
	#include "src/gpu/glsl/GrGLSLVarying.h"

	const char* GrGLSLFragmentShaderBuilder::kDstColorName = "_dstColor";

	uint8_t GrGLSLFragmentShaderBuilder::KeyForSurfaceOrigin(GrSurfaceOrigin origin) {
	SkASSERT(kTopLeft_GrSurfaceOrigin == origin \|\| kBottomLeft_GrSurfaceOrigin == origin);
	return origin + 1;

	static_assert(0 == kTopLeft_GrSurfaceOrigin);
	static_assert(1 == kBottomLeft_GrSurfaceOrigin);
	}

	GrGLSLFragmentShaderBuilder::GrGLSLFragmentShaderBuilder(GrGLSLProgramBuilder* program)
	: GrGLSLShaderBuilder(program) {
	fSubstageIndices.push_back(0);
	}

	const char* GrGLSLFragmentShaderBuilder::sampleOffsets() {
	SkASSERT(CustomFeatures::kSampleLocations & fProgramBuilder->processorFeatures());
	SkDEBUGCODE(fUsedProcessorFeaturesThisStage_DebugOnly \|= CustomFeatures::kSampleLocations);
	SkDEBUGCODE(fUsedProcessorFeaturesAllStages_DebugOnly \|= CustomFeatures::kSampleLocations);
	return "_sampleOffsets";
	}

	void GrGLSLFragmentShaderBuilder::maskOffMultisampleCoverage(
	const char* mask, ScopeFlags scopeFlags) {
	const GrShaderCaps& shaderCaps = *fProgramBuilder->shaderCaps();
	if (!shaderCaps.sampleMaskSupport()) {
	SkDEBUGFAIL("Attempted to mask sample coverage without support.");
	return;
	}
	if (const char* extension = shaderCaps.sampleVariablesExtensionString()) {
	this->addFeature(1 << kSampleVariables_GLSLPrivateFeature, extension);
	}

	if (!fHasModifiedSampleMask) {
	fHasModifiedSampleMask = true;
	if (ScopeFlags::kTopLevel != scopeFlags) {
	this->codePrependf("sk_SampleMask[0] = ~0;");
	}
	if (!(ScopeFlags::kInsideLoop & scopeFlags)) {
	this->codeAppendf("sk_SampleMask[0] = (%s);", mask);
	return;
	}
	}

	this->codeAppendf("sk_SampleMask[0] &= (%s);", mask);
	}

	void GrGLSLFragmentShaderBuilder::applyFnToMultisampleMask(
	const char* fn, const char* grad, ScopeFlags scopeFlags) {
	SkASSERT(CustomFeatures::kSampleLocations & fProgramBuilder->processorFeatures());
	SkDEBUGCODE(fUsedProcessorFeaturesThisStage_DebugOnly \|= CustomFeatures::kSampleLocations);
	SkDEBUGCODE(fUsedProcessorFeaturesAllStages_DebugOnly \|= CustomFeatures::kSampleLocations);

	int sampleCnt = fProgramBuilder->effectiveSampleCnt();
	SkASSERT(sampleCnt > 1);

	this->codeAppendf("{");

	if (!grad) {
	SkASSERT(fProgramBuilder->shaderCaps()->shaderDerivativeSupport());
	// In order to use HW derivatives, our neighbors within the same primitive must also be
	// executing the same code. A per-pixel branch makes this pre-condition impossible to
	// fulfill.
	SkASSERT(!(ScopeFlags::kInsidePerPixelBranch & scopeFlags));
	this->codeAppendf("float2 grad = float2(dFdx(%s), dFdy(%s));", fn, fn);
	this->codeAppendf("float fnwidth = fwidth(%s);", fn);
	grad = "grad";
	} else {
	this->codeAppendf("float fnwidth = abs(%s.x) + abs(%s.y);", grad, grad);
	}

	this->codeAppendf("int mask = 0;");
	this->codeAppendf("if (%s*2 < fnwidth) {", fn); // Are ANY samples inside the implicit fn?
	this->codeAppendf( "if (%s*-2 >= fnwidth) {", fn); // Are ALL samples inside the implicit?
	this->codeAppendf( "mask = ~0;");
	this->codeAppendf( "} else for (int i = 0; i < %i; ++i) {", sampleCnt);
	this->codeAppendf( "float fnsample = dot(%s, _sampleOffsets[i]) + %s;", grad, fn);
	this->codeAppendf( "if (fnsample < 0) {");
	this->codeAppendf( "mask \|= (1 << i);");
	this->codeAppendf( "}");
	this->codeAppendf( "}");
	this->codeAppendf("}");
	this->maskOffMultisampleCoverage("mask", scopeFlags);

	this->codeAppendf("}");
	}

	SkString GrGLSLFPFragmentBuilder::writeProcessorFunction(GrGLSLFragmentProcessor* fp,
	GrGLSLFragmentProcessor::EmitArgs& args) {
	this->onBeforeChildProcEmitCode();
	this->nextStage();

	// An FP's function signature is theoretically always main(half4 color, float2 _coords).
	// However, if it is only sampled by a chain of uniform matrix expressions (or legacy coord
	// transforms), the value that would have been passed to _coords is lifted to the vertex shader
	// and stored in a unique varying. In that case it uses that variable and does not have a
	// second actual argument for _coords.
	// FIXME: An alternative would be to have all FP functions have a float2 argument, and the
	// parent FP invokes it with the varying reference when it's been lifted to the vertex shader.
	size_t paramCount = 2;
	GrShaderVar params[] = { GrShaderVar(args.fInputColor, kHalf4_GrSLType),
	GrShaderVar(args.fSampleCoord, kFloat2_GrSLType) };

	if (!args.fFp.isSampledWithExplicitCoords()) {
	// Sampled with a uniform matrix expression and/or a legacy coord transform. The actual
	// transformation code is emitted in the vertex shader, so this only has to access it.
	// Add a float2 _coords variable that maps to the associated varying and replaces the
	// absent 2nd argument to the fp's function.
	paramCount = 1;

	if (args.fFp.referencesSampleCoords()) {
	const GrShaderVar& varying = args.fTransformedCoords[0];
	switch(varying.getType()) {
	case kFloat2_GrSLType:
	// Just point the local coords to the varying
	args.fSampleCoord = varying.getName().c_str();
	break;
	case kFloat3_GrSLType:
	// Must perform the perspective divide in the frag shader based on the varying,
	// and since we won't actually have a function parameter for local coords, add
	// it as a local variable.
	this->codeAppendf("float2 %s = %s.xy / %s.z;\n", args.fSampleCoord,
	varying.getName().c_str(), varying.getName().c_str());
	break;
	default:
	SkDEBUGFAILF("Unexpected varying type for coord: %s %d\n",
	varying.getName().c_str(), (int) varying.getType());
	break;
	}
	}
	} // else the function keeps its two arguments

	fp->emitCode(args);

	SkString funcName = this->getMangledFunctionName(args.fFp.name());
	this->emitFunction(kHalf4_GrSLType, funcName.c_str(), {params, paramCount},
	this->code().c_str());
	this->deleteStage();
	this->onAfterChildProcEmitCode();
	return funcName;
	}

	const char* GrGLSLFragmentShaderBuilder::dstColor() {
	SkDEBUGCODE(fHasReadDstColorThisStage_DebugOnly = true;)

	const GrShaderCaps* shaderCaps = fProgramBuilder->shaderCaps();
	if (shaderCaps->fbFetchSupport()) {
	this->addFeature(1 << kFramebufferFetch_GLSLPrivateFeature,
	shaderCaps->fbFetchExtensionString());

	// Some versions of this extension string require declaring custom color output on ES 3.0+
	const char* fbFetchColorName = "sk_LastFragColor";
	if (shaderCaps->fbFetchNeedsCustomOutput()) {
	this->enableCustomOutput();
	fCustomColorOutput->setTypeModifier(GrShaderVar::TypeModifier::InOut);
	fbFetchColorName = DeclaredColorOutputName();
	// Set the dstColor to an intermediate variable so we don't override it with the output
	this->codeAppendf("half4 %s = %s;", kDstColorName, fbFetchColorName);
	} else {
	return fbFetchColorName;
	}
	}
	return kDstColorName;
	}

	void GrGLSLFragmentShaderBuilder::enableAdvancedBlendEquationIfNeeded(GrBlendEquation equation) {
	SkASSERT(GrBlendEquationIsAdvanced(equation));

	if (fProgramBuilder->shaderCaps()->mustEnableAdvBlendEqs()) {
	this->addFeature(1 << kBlendEquationAdvanced_GLSLPrivateFeature,
	"GL_KHR_blend_equation_advanced");
	this->addLayoutQualifier("blend_support_all_equations", kOut_InterfaceQualifier);
	}
	}

	void GrGLSLFragmentShaderBuilder::enableCustomOutput() {
	if (!fCustomColorOutput) {
	fCustomColorOutput = &fOutputs.emplace_back(DeclaredColorOutputName(), kHalf4_GrSLType,
	GrShaderVar::TypeModifier::Out);
	fProgramBuilder->finalizeFragmentOutputColor(fOutputs.back());
	}
	}

	void GrGLSLFragmentShaderBuilder::enableSecondaryOutput() {
	SkASSERT(!fHasSecondaryOutput);
	fHasSecondaryOutput = true;
	const GrShaderCaps& caps = *fProgramBuilder->shaderCaps();
	if (const char* extension = caps.secondaryOutputExtensionString()) {
	this->addFeature(1 << kBlendFuncExtended_GLSLPrivateFeature, extension);
	}

	// If the primary output is declared, we must declare also the secondary output
	// and vice versa, since it is not allowed to use a built-in gl_FragColor and a custom
	// output. The condition also co-incides with the condition in which GLES SL 2.0
	// requires the built-in gl_SecondaryFragColorEXT, where as 3.0 requires a custom output.
	if (caps.mustDeclareFragmentShaderOutput()) {
	fOutputs.emplace_back(DeclaredSecondaryColorOutputName(), kHalf4_GrSLType,
	GrShaderVar::TypeModifier::Out);
	fProgramBuilder->finalizeFragmentSecondaryColor(fOutputs.back());
	}
	}

	const char* GrGLSLFragmentShaderBuilder::getPrimaryColorOutputName() const {
	return this->hasCustomColorOutput() ? DeclaredColorOutputName() : "sk_FragColor";
	}

	bool GrGLSLFragmentShaderBuilder::primaryColorOutputIsInOut() const {
	return fCustomColorOutput &&
	fCustomColorOutput->getTypeModifier() == GrShaderVar::TypeModifier::InOut;
	}

	const char* GrGLSLFragmentShaderBuilder::getSecondaryColorOutputName() const {
	if (this->hasSecondaryOutput()) {
	return (fProgramBuilder->shaderCaps()->mustDeclareFragmentShaderOutput())
	? DeclaredSecondaryColorOutputName()
	: "gl_SecondaryFragColorEXT";
	}
	return nullptr;
	}

	GrSurfaceOrigin GrGLSLFragmentShaderBuilder::getSurfaceOrigin() const {
	return fProgramBuilder->origin();
	}

	void GrGLSLFragmentShaderBuilder::onFinalize() {
	SkASSERT(fProgramBuilder->processorFeatures() == fUsedProcessorFeaturesAllStages_DebugOnly);

	if (CustomFeatures::kSampleLocations & fProgramBuilder->processorFeatures()) {
	const SkTArray<SkPoint>& sampleLocations = fProgramBuilder->getSampleLocations();
	this->definitions().appendf("const float2 _sampleOffsets[%i] = float2[%i](",
	sampleLocations.count(), sampleLocations.count());
	for (int i = 0; i < sampleLocations.count(); ++i) {
	SkPoint offset = sampleLocations[i] - SkPoint::Make(.5f, .5f);
	if (kBottomLeft_GrSurfaceOrigin == this->getSurfaceOrigin()) {
	offset.fY = -offset.fY;
	}
	this->definitions().appendf("float2(%f, %f)", offset.x(), offset.y());
	this->definitions().append((i + 1 != sampleLocations.count()) ? ", " : ");");
	}
	}

	fProgramBuilder->varyingHandler()->getFragDecls(&this->inputs(), &this->outputs());
	}

	void GrGLSLFragmentShaderBuilder::onBeforeChildProcEmitCode() {
	SkASSERT(fSubstageIndices.count() >= 1);
	fSubstageIndices.push_back(0);
	// second-to-last value in the fSubstageIndices stack is the index of the child proc
	// at that level which is currently emitting code.
	fMangleString.appendf("_c%d", fSubstageIndices[fSubstageIndices.count() - 2]);
	}

	void GrGLSLFragmentShaderBuilder::onAfterChildProcEmitCode() {
	SkASSERT(fSubstageIndices.count() >= 2);
	fSubstageIndices.pop_back();
	fSubstageIndices.back()++;
	int removeAt = fMangleString.findLastOf('_');
	fMangleString.remove(removeAt, fMangleString.size() - removeAt);
	}