src/gpu/glsl/GrGLSLGeometryProcessor.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/glsl/GrGLSLGeometryProcessor.h"

#include "src/gpu/GrCoordTransform.h"
#include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
#include "src/gpu/glsl/GrGLSLUniformHandler.h"
#include "src/gpu/glsl/GrGLSLVarying.h"
#include "src/gpu/glsl/GrGLSLVertexGeoBuilder.h"

void GrGLSLGeometryProcessor::emitCode(EmitArgs& args) {
    GrGPArgs gpArgs;
    this->onEmitCode(args, &gpArgs);

    if (args.fGP.willUseTessellationShaders()) {
        // Tessellation shaders are temporarily responsible for integrating their own code strings
        // while we work out full support.
        return;
    }

    GrGLSLVertexBuilder* vBuilder = args.fVertBuilder;
    if (!args.fGP.willUseGeoShader()) {
        // Emit the vertex position to the hardware in the normalized window coordinates it expects.
        SkASSERT(kFloat2_GrSLType == gpArgs.fPositionVar.getType() ||
                 kFloat3_GrSLType == gpArgs.fPositionVar.getType());
        vBuilder->emitNormalizedSkPosition(gpArgs.fPositionVar.c_str(), args.fRTAdjustName,
                                           gpArgs.fPositionVar.getType());
        if (kFloat2_GrSLType == gpArgs.fPositionVar.getType()) {
            args.fVaryingHandler->setNoPerspective();
        }
    } else {
        // Since we have a geometry shader, leave the vertex position in Skia device space for now.
        // The geometry Shader will operate in device space, and then convert the final positions to
        // normalized hardware window coordinates under the hood, once everything else has finished.
        // The subclass must call setNoPerspective on the varying handler, if applicable.
        vBuilder->codeAppendf("sk_Position = float4(%s", gpArgs.fPositionVar.c_str());
        switch (gpArgs.fPositionVar.getType()) {
            case kFloat_GrSLType:
                vBuilder->codeAppend(", 0"); // fallthru.
            case kFloat2_GrSLType:
                vBuilder->codeAppend(", 0"); // fallthru.
            case kFloat3_GrSLType:
                vBuilder->codeAppend(", 1"); // fallthru.
            case kFloat4_GrSLType:
                vBuilder->codeAppend(");");
                break;
            default:
                SK_ABORT("Invalid position var type");
                break;
        }
    }
}

void GrGLSLGeometryProcessor::emitTransforms(GrGLSLVertexBuilder* vb,
                                             GrGLSLVaryingHandler* varyingHandler,
                                             GrGLSLUniformHandler* uniformHandler,
                                             const GrShaderVar& localCoordsVar,
                                             const SkMatrix& localMatrix,
                                             FPCoordTransformHandler* handler) {
    // We only require localCoordsVar to be valid if there is a coord transform that needs
    // it. CTs on FPs called with explicit coords do not require a local coord.
    auto getLocalCoords = [&localCoordsVar,
                           localCoords = SkString(),
                           localCoordLength = int()]() mutable {
        if (localCoords.isEmpty()) {
            localCoordLength = GrSLTypeVecLength(localCoordsVar.getType());
            SkASSERT(GrSLTypeIsFloatType(localCoordsVar.getType()));
            SkASSERT(localCoordLength == 2 || localCoordLength == 3);
            if (localCoordLength == 3) {
                localCoords = localCoordsVar.getName();
            } else {
                localCoords.printf("float3(%s, 1)", localCoordsVar.c_str());
            }
        }
        return std::make_tuple(localCoords, localCoordLength);
    };

    for (int i = 0; *handler; ++*handler, ++i) {
        auto [coordTransform, fp] = handler->get();
        // Add uniform for coord transform matrix.
        const char* matrixName;
        if (!fp.isSampledWithExplicitCoords() || !coordTransform.isNoOp()) {
            SkString strUniName;
            strUniName.printf("CoordTransformMatrix_%d", i);
            auto flag = fp.isSampledWithExplicitCoords() ? kFragment_GrShaderFlag
                                                         : kVertex_GrShaderFlag;
            fInstalledTransforms.push_back().fHandle =
                    uniformHandler
                            ->addUniform(flag, kFloat3x3_GrSLType, strUniName.c_str(), &matrixName)
                            .toIndex();
        } else {
            // Install a coord transform that will be skipped.
            fInstalledTransforms.push_back();
            handler->omitCoordsForCurrCoordTransform();
            continue;
        }

        // Add varying if required and register varying and matrix uniform.
        if (!fp.isSampledWithExplicitCoords()) {
            auto [localCoordsStr, localCoordLength] = getLocalCoords();
            GrGLSLVarying v(kFloat2_GrSLType);
            if (localMatrix.hasPerspective() || coordTransform.matrix().hasPerspective() ||
                localCoordLength == 3) {
                v = GrGLSLVarying(kFloat3_GrSLType);
            }
            SkString strVaryingName;
            strVaryingName.printf("TransformedCoords_%d", i);
            varyingHandler->addVarying(strVaryingName.c_str(), &v);

            if (v.type() == kFloat2_GrSLType) {
                vb->codeAppendf("%s = (%s * %s).xy;", v.vsOut(), matrixName,
                                localCoordsStr.c_str());
            } else {
                vb->codeAppendf("%s = %s * %s;", v.vsOut(), matrixName, localCoordsStr.c_str());
            }
            GrShaderVar fsVar(SkString(v.fsIn()), v.type(), GrShaderVar::kIn_TypeModifier);
            handler->specifyCoordsForCurrCoordTransform(SkString(matrixName),
                                                        fInstalledTransforms.back().fHandle, fsVar);
        } else {
            handler->specifyCoordsForCurrCoordTransform(SkString(matrixName),
                                                        fInstalledTransforms.back().fHandle);
        }
    }
}

void GrGLSLGeometryProcessor::setTransformDataHelper(const SkMatrix& localMatrix,
                                                     const GrGLSLProgramDataManager& pdman,
                                                     const CoordTransformRange& transformRange) {
    int i = 0;
    for (auto [transform, fp] : transformRange) {
        if (fInstalledTransforms[i].fHandle.isValid()) {
            SkMatrix m;
            if (fp.isSampledWithExplicitCoords()) {
                m = GetTransformMatrix(transform, SkMatrix::I());
            } else {
                m = GetTransformMatrix(transform, localMatrix);
            }
            if (!SkMatrixPriv::CheapEqual(fInstalledTransforms[i].fCurrentValue, m)) {
                pdman.setSkMatrix(fInstalledTransforms[i].fHandle.toIndex(), m);
                fInstalledTransforms[i].fCurrentValue = m;
            }
        }
        ++i;
    }
    SkASSERT(i == fInstalledTransforms.count());
}

void GrGLSLGeometryProcessor::writeOutputPosition(GrGLSLVertexBuilder* vertBuilder,
                                                  GrGPArgs* gpArgs,
                                                  const char* posName) {
    gpArgs->fPositionVar.set(kFloat2_GrSLType, "pos2");
    vertBuilder->codeAppendf("float2 %s = %s;", gpArgs->fPositionVar.c_str(), posName);
}

void GrGLSLGeometryProcessor::writeOutputPosition(GrGLSLVertexBuilder* vertBuilder,
                                                  GrGLSLUniformHandler* uniformHandler,
                                                  GrGPArgs* gpArgs,
                                                  const char* posName,
                                                  const SkMatrix& mat,
                                                  UniformHandle* viewMatrixUniform) {
    if (mat.isIdentity()) {
        gpArgs->fPositionVar.set(kFloat2_GrSLType, "pos2");
        vertBuilder->codeAppendf("float2 %s = %s;", gpArgs->fPositionVar.c_str(), posName);
    } else {
        const char* viewMatrixName;
        *viewMatrixUniform = uniformHandler->addUniform(kVertex_GrShaderFlag,
                                                        kFloat3x3_GrSLType,
                                                        "uViewM",
                                                        &viewMatrixName);
        if (!mat.hasPerspective()) {
            gpArgs->fPositionVar.set(kFloat2_GrSLType, "pos2");
            vertBuilder->codeAppendf("float2 %s = (%s * float3(%s, 1)).xy;",
                                     gpArgs->fPositionVar.c_str(), viewMatrixName, posName);
        } else {
            gpArgs->fPositionVar.set(kFloat3_GrSLType, "pos3");
            vertBuilder->codeAppendf("float3 %s = %s * float3(%s, 1);",
                                     gpArgs->fPositionVar.c_str(), viewMatrixName, posName);
        }
    }
}