axmol/core/renderer/backend/VertexLayout.h

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 Copyright (c) 2018-2019 Xiamen Yaji Software Co., Ltd.

 https://axis-project.github.io/

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#pragma once

#include "Macros.h"
#include "Types.h"
#include "base/CCRef.h"

#include <string>
#include <cstdint>
#include <vector>
#include <unordered_map>

NS_AX_BACKEND_BEGIN
/**
 * @addtogroup _backend
 * @{
 */

/**
 * Store vertex attribute layout.
 */
class AX_DLL VertexLayout
{
public:
    struct Attribute
    {
        Attribute() = default;
        Attribute(std::string_view _name,
                  std::size_t _index,
                  VertexFormat _format,
                  std::size_t _offset,
                  bool needToBeNormallized)
            : name(_name), format(_format), offset(_offset), index(_index), needToBeNormallized(needToBeNormallized)
        {}

        std::string name;  ///< name is used in opengl
        VertexFormat format      = VertexFormat::INT3;
        std::size_t offset       = 0;
        std::size_t index        = 0;  ///< index is used in metal
        bool needToBeNormallized = false;
    };

    VertexLayout() = default;

    /**
     * Set attribute values to name.
     * @param name Specifies the attribute name.
     * @param index Specifies the index of the generic vertex attribute to be modified.
     * @param format Specifies how the vertex attribute data is laid out in memory.
     * @param offset Specifies the byte offset to the first component of the first generic vertex attribute.
     * @param needToBeNormallized Specifies whether fixed-point data values should be normalized (true) or converted
     * directly as fixed-point values (false) when they are accessed.
     */
    void setAttribute(std::string_view name,
                      std::size_t index,
                      VertexFormat format,
                      std::size_t offset,
                      bool needToBeNormallized);

    /**
     * Set stride of vertices.
     * @param stride Specifies the distance between the data of two vertices, in bytes.
     */
    void setLayout(std::size_t stride);

    /**
     * Get the distance between the data of two vertices, in bytes.
     * @return The distance between the data of two vertices, in bytes.
     */
    inline std::size_t getStride() const { return _stride; }

    /**
     * Get vertex step function. Default value is VERTEX.
     * @return Vertex step function.
     * @note Used in metal.
     */
    inline VertexStepMode getVertexStepMode() const { return _stepMode; }

    /**
     * Get attribute informations
     * @return Atrribute informations.
     */
    inline const hlookup::string_map<Attribute>& getAttributes() const { return _attributes; }

    /**
     * Check if vertex layout has been set.
     */
    inline bool isValid() const { return _stride != 0; }

private:
    hlookup::string_map<Attribute> _attributes;
    std::size_t _stride      = 0;
    VertexStepMode _stepMode = VertexStepMode::VERTEX;
};

// end of _backend group
/// @}
NS_AX_BACKEND_END