src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp

/*
 * 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"

GrGLSLFragmentShaderBuilder::GrGLSLFragmentShaderBuilder(GrGLSLProgramBuilder* program)
        : GrGLSLShaderBuilder(program) {}

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 DeclaredColorOutputName();
}

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