src/core/SkMeshPriv.h

/*
 * Copyright 2021 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkMeshPriv_DEFINED
#define SkMeshPriv_DEFINED

#include "include/core/SkData.h"
#include "include/core/SkMesh.h"
#include "src/core/SkSLTypeShared.h"

struct SkMeshSpecificationPriv {
    using Varying   = SkMeshSpecification::Varying;
    using Attribute = SkMeshSpecification::Attribute;
    using ColorType = SkMeshSpecification::ColorType;

    static SkSpan<const Varying> Varyings(const SkMeshSpecification& spec) {
        return SkSpan(spec.fVaryings);
    }

    static const SkSL::Program* VS(const SkMeshSpecification& spec) { return spec.fVS.get(); }
    static const SkSL::Program* FS(const SkMeshSpecification& spec) { return spec.fFS.get(); }

    static int Hash(const SkMeshSpecification& spec) { return spec.fHash; }

    static ColorType GetColorType(const SkMeshSpecification& spec) { return spec.fColorType; }
    static bool HasColors(const SkMeshSpecification& spec) {
        return GetColorType(spec) != ColorType::kNone;
    }

    static SkColorSpace* ColorSpace(const SkMeshSpecification& spec) {
        return spec.fColorSpace.get();
    }

    static SkAlphaType AlphaType(const SkMeshSpecification& spec) { return spec.fAlphaType; }

    static SkSLType VaryingTypeAsSLType(Varying::Type type) {
        switch (type) {
            case Varying::Type::kFloat:  return SkSLType::kFloat;
            case Varying::Type::kFloat2: return SkSLType::kFloat2;
            case Varying::Type::kFloat3: return SkSLType::kFloat3;
            case Varying::Type::kFloat4: return SkSLType::kFloat4;
            case Varying::Type::kHalf:   return SkSLType::kHalf;
            case Varying::Type::kHalf2:  return SkSLType::kHalf2;
            case Varying::Type::kHalf3:  return SkSLType::kHalf3;
            case Varying::Type::kHalf4:  return SkSLType::kHalf4;
        }
        SkUNREACHABLE;
    }

    static SkSLType AttrTypeAsSLType(Attribute::Type type) {
        switch (type) {
            case Attribute::Type::kFloat:        return SkSLType::kFloat;
            case Attribute::Type::kFloat2:       return SkSLType::kFloat2;
            case Attribute::Type::kFloat3:       return SkSLType::kFloat3;
            case Attribute::Type::kFloat4:       return SkSLType::kFloat4;
            case Attribute::Type::kUByte4_unorm: return SkSLType::kHalf4;
        }
        SkUNREACHABLE;
    }

    static int PassthroughLocalCoordsVaryingIndex(const SkMeshSpecification& spec) {
        return spec.fPassthroughLocalCoordsVaryingIndex;
    }

    /**
     * A varying is dead if it is never referenced OR it is only referenced as a passthrough for
     * local coordinates. In the latter case, its index will returned as
     * PassthroughLocalCoordsVaryingIndex. Our analysis is not very sophisticated so this is
     * determined conservatively.
     */
    static bool VaryingIsDead(const SkMeshSpecification& spec, int v) {
        SkASSERT(v >= 0 && SkToSizeT(v) < spec.fVaryings.size());
        return (1 << v) & spec.fDeadVaryingMask;
    }
};

namespace SkMeshPriv {
class Buffer {
public:
    virtual ~Buffer() = 0;

    Buffer() = default;
    Buffer(const Buffer&) = delete;

    Buffer& operator=(const Buffer&) = delete;

    virtual const void* peek() const { return nullptr; }

    virtual bool isGaneshBacked() const { return false; }
};

class IB : public Buffer, public SkMesh::IndexBuffer  {};
class VB : public Buffer, public SkMesh::VertexBuffer {};

template <typename Base> class CpuBuffer final : public Base {
public:
    ~CpuBuffer() override = default;

    static sk_sp<Base> Make(const void* data, size_t size);

    const void* peek() const override { return fData->data(); }

    size_t size() const override { return fData->size(); }

private:
    CpuBuffer(sk_sp<SkData> data) : fData(std::move(data)) {}

    bool onUpdate(GrDirectContext*, const void* data, size_t offset, size_t size) override;

    sk_sp<SkData> fData;
};

using CpuIndexBuffer  = CpuBuffer<IB>;
using CpuVertexBuffer = CpuBuffer<VB>;
}  // namespace SkMeshPriv

inline SkMeshPriv::Buffer::~Buffer() = default;

template <typename Base> sk_sp<Base> SkMeshPriv::CpuBuffer<Base>::Make(const void* data,
                                                                       size_t size) {
    SkASSERT(size);
    sk_sp<SkData> storage;
    if (data) {
        storage = SkData::MakeWithCopy(data, size);
    } else {
        storage = SkData::MakeZeroInitialized(size);
    }
    return sk_sp<Base>(new CpuBuffer<Base>(std::move(storage)));
}

template <typename Base> bool SkMeshPriv::CpuBuffer<Base>::onUpdate(GrDirectContext* dc,
                                                                    const void* data,
                                                                    size_t offset,
                                                                    size_t size) {
    if (dc) {
        return false;
    }
    std::memcpy(SkTAddOffset<void>(fData->writable_data(), offset), data, size);
    return true;
}

#endif