Metal -如何从调度的处理程序回调中呈现可绘制

// 创建Metal设备
id<MTLDevice> device = MTLCreateSystemDefaultDevice();

// 创建渲染管道
id<MTLLibrary> library = [device newDefaultLibrary];
id<MTLFunction> vertexFunction = [library newFunctionWithName:@"vertexShader"];
id<MTLFunction> fragmentFunction = [library newFunctionWithName:@"fragmentShader"];
MTLRenderPipelineDescriptor *pipelineDescriptor = [MTLRenderPipelineDescriptor new];
pipelineDescriptor.vertexFunction = vertexFunction;
pipelineDescriptor.fragmentFunction = fragmentFunction;
id<MTLRenderPipelineState> pipelineState = [device newRenderPipelineStateWithDescriptor:pipelineDescriptor error:nil];

// 创建命令缓冲区
id<MTLCommandQueue> commandQueue = [device newCommandQueue];
id<MTLCommandBuffer> commandBuffer = [commandQueue commandBuffer];

// 创建绘制描述符
MTLRenderPassDescriptor *renderPassDescriptor = [MTLRenderPassDescriptor new];
renderPassDescriptor.colorAttachments[0].texture = drawable.texture;
renderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionClear;
renderPassDescriptor.colorAttachments[0].storeAction = MTLStoreActionStore;

// 创建渲染命令编码器
id<MTLRenderCommandEncoder> renderEncoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
[renderEncoder setRenderPipelineState:pipelineState];

// 设置渲染状态
[renderEncoder setViewport:viewport];
[renderEncoder setVertexBuffer:vertexBuffer offset:0 atIndex:0];
[renderEncoder setFragmentTexture:texture atIndex:0];

// 绘制可绘制对象
[renderEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:3];

// 结束渲染命令编码器
[renderEncoder endEncoding];

// 提交命令缓冲区
[commandBuffer presentDrawable:drawable];
[commandBuffer commit];