axmol/core/renderer/backend/metal/CommandBufferMTL.h

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

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#pragma once

#include "../CommandBuffer.h"
#include "DeviceMTL.h"
#include <unordered_map>

NS_AX_BACKEND_BEGIN

class RenderPipelineMTL;
class DepthStencilStateMTL;

/**
 * @addtogroup _metal
 * @{
 */

/**
 * @brief Store encoded commands for the GPU to execute.
 * A command buffer stores encoded commands until the buffer is committed for execution by the GPU
 */
class CommandBufferMTL : public CommandBuffer
{
public:
    /// @name Constructor, Destructor and Initializers
    /**
     * @param deviceMTL The device for which MTLCommandQueue object was created.
     */
    CommandBufferMTL(DeviceMTL* deviceMTL);
    ~CommandBufferMTL();

    /**
     * Set depthStencil status
     * @param depthStencilState Specifies the depth and stencil status
     */
    virtual void setDepthStencilState(DepthStencilState* depthStencilState) override;

    /**
     * Sets the current render pipeline state object once
     * @param renderPipeline An object that contains the graphics functions and configuration state used in a render
     * pass.
     */
    virtual void setRenderPipeline(RenderPipeline* renderPipeline) override;

    /// @name Setters & Getters
    /**
     * @brief Indicate the begining of a frame
     * Wait until the inflight command buffer has completed its work.
     * Then create MTLCommandBuffer and enqueue it to MTLCommandQueue.
     * Then start schedule available MTLBuffer
     */
    virtual bool beginFrame() override;

    /**
     * Create a MTLRenderCommandEncoder object for graphics rendering to an attachment in a RenderPassDescriptor.
     * MTLRenderCommandEncoder is cached if current RenderPassDescriptor is identical to previous one.
     * @param descriptor Specifies a group of render targets that hold the results of a render pass.
     */
    virtual void beginRenderPass(const RenderTarget* renderTarget, const RenderPassDescriptor& descriptor) override;

    /**
     * Update depthStencil status, improvment: for metal backend cache it
     * @param depthStencilState Specifies the depth and stencil status
     */
    virtual void updateDepthStencilState(const DepthStencilDescriptor& descriptor) override;

    /**
     * Update render pipeline status
     * Building a programmable pipeline involves an expensive evaluation of GPU state.
     * So a new render pipeline object will be created only if it hasn't been created before.
     * @param rt Specifies the render target.
     * @param pipelineDescriptor Specifies the pipeline descriptor.
     */
    virtual void updatePipelineState(const RenderTarget* rt, const PipelineDescriptor& descriptor) override;

    /**
     * Fixed-function state
     * @param x The x coordinate of the upper-left corner of the viewport.
     * @param y The y coordinate of the upper-left corner of the viewport.
     * @param w The width of the viewport, in pixels.
     * @param h The height of the viewport, in pixels.
     */
    virtual void setViewport(int x, int y, unsigned int w, unsigned int h) override;

    /**
     * Fixed-function state
     * @param mode Controls if primitives are culled when front facing, back facing, or not culled at all.
     */
    virtual void setCullMode(CullMode mode) override;

    /**
     * Fixed-function state
     * @param winding The winding order of front-facing primitives.
     */
    virtual void setWinding(Winding winding) override;

    /**
     * Set a global buffer for all vertex shaders at the given bind point index 0.
     * @param buffer The buffer to set in the buffer argument table.
     */
    virtual void setVertexBuffer(Buffer* buffer) override;

    /**
     * Set the uniform data at a given vertex and fragment buffer binding point 1
     * Set a global texture for all vertex and fragment shaders at the given bind location.
     * @param programState A programState object that hold the uniform and texture data.
     */
    virtual void setProgramState(ProgramState* programState) override;

    /**
     * Set indexes when drawing primitives with index list
     * @ buffer A buffer object that the device will read indexes from.
     * @ see `drawElements(PrimitiveType primitiveType, IndexFormat indexType, unsigned int count, unsigned int offset)`
     */
    virtual void setIndexBuffer(Buffer* buffer) override;
    
    void setInstanceBuffer(Buffer* buffer) override;

    /**
     * Draw primitives without an index list.
     * @param primitiveType The type of primitives that elements are assembled into.
     * @param start For each instance, the first index to draw
     * @param count For each instance, the number of indexes to draw
     * @see `drawElements(PrimitiveType primitiveType, IndexFormat indexType, unsigned int count, unsigned int offset)`
	 *
	 * TODO: Implement a wireframe mode for METAL devices. Refer to: https://forums.ogre3d.org/viewtopic.php?t=95089
     */
    virtual void drawArrays(PrimitiveType primitiveType, std::size_t start, std::size_t count, bool wireframe) override;

    /**
     * Draw primitives with an index list.
     * @param primitiveType The type of primitives that elements are assembled into.
     * @param indexType The type if indexes, either 16 bit integer or 32 bit integer.
     * @param count The number of indexes to read from the index buffer for each instance.
     * @param offset Byte offset within indexBuffer to start reading indexes from.
     * @see `setIndexBuffer(Buffer* buffer)`
     * @see `drawArrays(PrimitiveType primitiveType, unsigned int start,  unsigned int count)`
	 *
	 * TODO: Implement a wireframe mode for METAL devices. Refer to: https://forums.ogre3d.org/viewtopic.php?t=95089
     */
    virtual void drawElements(PrimitiveType primitiveType,
                              IndexFormat indexType,
                              std::size_t count,
                              std::size_t offset,
                              bool wireframe) override;
    
    void drawElementsInstanced(PrimitiveType primitiveType,
                               IndexFormat indexType,
                               std::size_t count,
                               std::size_t offset,
                               int instanceCount,
                               bool wireframe = false) override;

    /**
     * Do some resources release.
     */
    virtual void endRenderPass() override;

    /**
     * Present a drawable and commit a command buffer so it can be executed as soon as possible.
     */
    virtual void endFrame() override;

    void endEncoding();

    /**
     * Fixed-function state
     * @param x, y Specifies the lower left corner of the scissor box
     * @param wdith Specifies the width of the scissor box
     * @param height Specifies the height of the scissor box
     */
    virtual void setScissorRect(bool isEnabled, float x, float y, float width, float height) override;

    /**
     * Read pixels from RenderTarget
     * @param callback A callback to deal with pixel data read.
     */
    virtual void readPixels(RenderTarget* rt, std::function<void(const PixelBufferDescriptor&)> callback) override;
    
    id<MTLRenderCommandEncoder> getRenderCommandEncoder() const { return _mtlRenderEncoder; }

    id<MTLCommandBuffer> getMTLCommandBuffer() const { return _mtlCommandBuffer; }

protected:
    /**
     * Read a block of pixels from the given texture
     * @param texture Specifies the texture to get the image.
     * @param origX,origY Specify the window coordinates of the first pixel that is read from the given texture. This
     * location is the lower left corner of a rectangular block of pixels.
     * @param rectWidth,rectHeight Specify the dimensions of the pixel rectangle. rectWidth and rectHeight of one
     * correspond to a single pixel.
     * @param pbd, the output buffer for fill texels data
     * @remark: !!!this function only can call after endFrame, then it's could be works well.
     */
    static void readPixels(TextureBackend* texture,
                           std::size_t origX,
                           std::size_t origY,
                           std::size_t rectWidth,
                           std::size_t rectHeight,
                           PixelBufferDescriptor& pbd);
    static void readPixels(id<MTLTexture> texture,
                           std::size_t origX,
                           std::size_t origY,
                           std::size_t rectWidth,
                           std::size_t rectHeight,
                           PixelBufferDescriptor& pbd);

private:
    void prepareDrawing() const;
    void setTextures() const;
    void doSetTextures(bool isVertex) const;
    void setUniformBuffer() const;
    void afterDraw();
    void flush();
    void flushCaptureCommands();
    void updateRenderCommandEncoder(const RenderTarget* renderTarget, const RenderPassDescriptor& renderPassParams);

    id<MTLCommandBuffer> _mtlCommandBuffer        = nil;
    id<MTLCommandQueue> _mtlCommandQueue          = nil;
    id<MTLRenderCommandEncoder> _mtlRenderEncoder = nil;
    id<MTLBuffer> _mtlIndexBuffer                 = nil;
    id<MTLTexture> _drawableTexture               = nil;

    DepthStencilStateMTL* _depthStencilStateMTL = nullptr;
    RenderPipelineMTL* _renderPipelineMTL       = nullptr;
    ProgramState* _programState                 = nullptr;

    unsigned int _renderTargetWidth  = 0;
    unsigned int _renderTargetHeight = 0;

    dispatch_semaphore_t _frameBoundarySemaphore;
    const RenderTarget* _currentRenderTarget = nil;  // weak ref
    RenderPassDescriptor _currentRenderPassDesc;
    TargetBufferFlags _currentRenderTargetFlags = TargetBufferFlags::NONE;
    NSAutoreleasePool* _autoReleasePool         = nil;

    std::vector<std::pair<TextureBackend*, std::function<void(const PixelBufferDescriptor&)>>> _captureCallbacks;
};

// end of _metal group
/// @}
NS_AX_BACKEND_END