

# vulkan_raii.hpp: a programming guide

## Introduction

vulkan_raii.hpp is a C++ layer on top of vulkan.hpp that follows the RAII-principle (RAII: Resource Acquisition Is Initialization, see [https://en.cppreference.com/w/cpp/language/raii#:~:text=Resource%20Acquisition%20Is%20Initialization%20or,in%20limited%20supply](https://en.cppreference.com/w/cpp/language/raii#:~:text=Resource%20Acquisition%20Is%20Initialization%20or,in%20limited%20supply)). This header-only library uses all the enums and structure wrappers from vulkan.hpp and provides a new set of wrapper classes for the Vulkan handle types. Instead of creating Vulkan handles with vk*Allocate or vk*Create a constructor of the corresponding Vulkan handle wrapper class is used. And instead of destroying Vulkan handles with vk*Free or vk*Destroy, the destructor of that handle class is called.

## General Usage

As a simple example, instead of creating a `vk::Device`

    // create a vk::Device, given a vk::PhysicalDevice physicalDevice and a vk::DeviceCreateInfo deviceCreateInfo
    vk::Device device = physicalDevice.createDevice( deviceCreateInfo );

and destroying it at some point

    // destroy a vk::Device
    device.destroy();

you would create a `vk::raii::Device`

    // create a vk::raii::Device, given a vk::raii::PhysicalDevice physicalDevice and a vk::DeviceCreateInfo deviceCreateInfo
    vk::raii::Device device( physicalDevice, deviceCreateInfo );

That `vk::raii::Device` is automatically destroyed, when its scope is left.

Other than the `vk::Device`, you can assign the `vk::raii::Device` to a smart pointer:

    // create a smart-pointer to a vk::raii::Device, given a smart-pointer to a vk::raii::PhysicalDevice pPhysicalDevice and a vk::DeviceCreateInfo deviceCreateInfo
    std::unique_ptr<vk::raii::Device> pDevice;
    pDevice = std::make_unique<vk::raii::Device>( *pPhysicalDevice, deviceCreateInfo );

Note that, as the vk::raii objects own the actual Vulkan resource, all vk::raii objects are moveable, but not copyable.

For simplicity, in the rest of this document a vk::raii object is always directly instantiated on the stack. Obviously, that's not essential. You could assign them as well to a std::unique_ptr, a std::shared_ptr, or any other smart pointer or object managing data structure. And you can even assign them to a dumb pointer by using the new operator.

Similar to a `vk::Device`, a `vk::raii::Device` provides the functions related to that class. But other than the `vk::Device`, you don't need to provide a device-specific dispatcher to those functions to get multi-device functionality. That's already managed by the `vk::raii::Device`.

That is, calling a device-related function is identical for both cases:

    // call waitIdle from a vk::Device
    device.waitIdle();

    // call waitIdle from a vk::raii::Device
    device.waitIdle();

vk::raii goes one step further. In the vk namespace, most of the functions are members of `vk::Device`. In the vk::raii namespace functions strongly related to a non-dispatchable handle are members of the corresponding vi::raii object. For example, to bind memory to a buffer, in vk namespace you write

    // bind vk::DeviceMemory memory to a vk::Buffer buffer, given vk::DeviceSize memoryOffset
    device.bindBufferMemory( buffer, memory, memoryOffset );

In vk::raii namespace you write

    // bind vk::raii::DeviceMemory memory to a vk::raii::Buffer buffer, given vk::DeviceSize memoryOffset
    buffer.bindMemory( *memory, memoryOffset );
    
Note that `vk::raii::Buffer::bindMemory()`takes a `vk::DeviceMemory` as its first argument, not a `vk::raii::DeviceMemory`. From a vk::raii object you get to the corresponding vk object by just dereferencing the vk::raii object.

## First Steps

### 00 Create a vk::raii::Context

The very first step when using classes from the vk::raii namespace is to instantiate a `vk::raii::Context`. This class has no counterpart in either the vk namespace or the pure C-API of Vulkan. It is the handle to the few functions that are not bound to a `VkInstance` or a `VkDevice`:

    // instantiate a vk::raii::Context
    vk::raii::Context context;

To use any of those "global" functions, your code would look like that:

    // get the API version, using that context
    uint32_t apiVersion = context.enumerateInstanceVersion();

### 01 Create a vk::raii::Instance

To pass that information on to a `vk::raii::Instance`, its constructor gets a reference to that `vk::raii::Context`:

    // instantiate a vk::raii::Instance, given a vk::raii::Context context and a vk::InstanceCreateInfo instanceCreateInfo
    vk::raii::Instance instance( context, instanceCreateInfo );

The `vk::raii::Instance` now holds all the instance-related functions. For example, to get all the `vk::PhysicalDeviceGroupProperties` for an instance, your call would look like this:

    // get all vk::PhysicalDeviceGroupProperties from a vk::raii::Instance instance
    std::vector<vk::PhysicalDeviceGroupProperties> physicalDeviceGroupProperties = instance.enumeratePhysicalDeviceGroups();

Actually, "all the instance-related functions", as stated above, might be a bit misleading. There are just very few public functions available with the `vk::raii::Instance`, as most of the instance-related functions are creation functions that are not wrapped publicly but used internally when instantiating other vk::raii-objects.

### 02 Enumerate the vk::raii::PhysicalDevices

Enumerating the physical devices of an instance is slightly different in vk::raii namespace as you might be used to from the vk-namespace or the pure C-API. As there might be multiple physical devices attached, you would instantiate a `vk::raii::PhysicalDevices` (note the trailing 's' here!), which essentially is a `std::vector` of `vk::raii::PhysicalDevice`s (note the trailing 's' here!):

    // enumerate the vk::raii::PhysicalDevices, given a vk::raii::Instance instance
    vk::raii::PhysicalDevices physicalDevices( instance );

As vk::raii::PhysicalDevices is just a `std::vector<vk::raii::PhysicalDevice>`, you can access any specific `vk::raii:PhysicalDevice` by indexing into that `std::vector`:

    // get the vk::LayerProperties of the vk::raii::PhysicalDevice with index physicalDeviceIndex, given a vk::raii::PhysicalDevices physicalDevices
    std::vector<vk::LayerProperties> layerProperties = physicalDevices[physicalDeviceIndex].enumerateDeviceLayerProperties();

You can as well get one `vk::raii::PhysicalDevice` out of a `vk::raii::PhysicalDevices` like this:

    // get the vk::raii::PhysicalDevice with index physicalDeviceIndex, given a vk::raii::PhysicalDevices physicalDevices object:
    vk::raii::PhysicalDevice physicalDevice( std::move( physicalDevices[physicalDeviceIndex] ) );

Note, that even though the actual `VkPhysicalDevice` owned by a `vk::raii::PhysicalDevice` is not a destructible resource, for consistency reasons a `vk::raii::PhysicalDevice` is a movable but not copyable object just like all the other vk::raii objects.

### 03 Create a vk::raii::Device

To create a `vk::raii::Device`, you just instantiate an object of that class:

    // create a vk::raii::Device, given a vk::raii::PhysicalDevice physicalDevice and a vk::DeviceCreateInfo deviceCreateInfo
    vk::raii::Device device( physicalDevice, deviceCreateInfo );

For each instantiated `vk::raii::Device`, the device-specific Vulkan function pointers are resolved. That is, for multi-device programs, you automatically use the correct device-specific function pointers, and organizing a multi-device program is simplified:

    // create a vk::raii::Device per vk::raii::PhysicalDevice, given a vk::raii::PhysicalDevices physicalDevices, and a corresponding array of vk::DeviceCreateInfo deviceCreateInfos
    std::vector<vk::raii::Device> devices;
    for ( size_t i = 0; i < physicalDevices.size(); i++ )
    {
      devices.push_back( vk::raii::Device( physicalDevices[i], deviceCreateInfos[i] ) );
    }

### 04 Create a vk::raii::CommandPool and vk::raii::CommandBuffers

Creating a `vk::raii::CommandPool` is simply done by instantiating such an object:

    // create a vk::raii::CommandPool, given a vk::raii::Device device and a vk::CommandPoolCreateInfo commandPoolCreateInfo
    vk::raii::CommandPool commandPool( device, commandPoolCreateInfo );

As the number of `vk::raii::CommandBuffer`s to allocate from a `vk::raii::CommandPool` is given by the member `commandBufferCount` of a `vk::CommandBufferAllocateInfo` structure, it can't be instantiated as a single object. Instead you get a `vk::raii::CommandBuffers` (note the trailing 's' here!), which essentially is a `std::vector` of `vk::raii::CommandBuffer`s (note the trailing 's' here!).

    // create a vk::raii::CommandBuffers, given a vk::raii::Device device and a vk::CommandBufferAllocateInfo commandBufferAllocateInfo
    vk::raii::CommandBuffers commandBuffers( device, commandBufferAllocateInfo );

Note, that the `vk::CommandBufferAllocateInfo` holds a `vk::CommandPool` member `commandPool`. To assign that from a `vk::raii::CommandPool` you can use the `operator*()`:

    // assign vk::CommandBufferAllocateInfo::commandPool, given a vk::raii::CommandPool commandPool
    commandBufferAllocateInfo.commandPool = *commandPool;

As a `vk::raii::CommandBuffers` is just a `std::vector<vk::raii::CommandBuffer>`, you can access any specific `vk::raii:CommandBuffer` by indexing into that `std::vector`:

    // start recording of the vk::raii::CommandBuffer with index commandBufferIndex, given a vk::raii::CommandBuffers commandBuffers
    commandBuffers[commandBufferIndex].begin();

You can as well get one `vk::raii::CommandBuffer` out of a `vk::raii::CommandBuffers` like this:

    // get the vk::raii::CommandBuffer with index commandBufferIndex, given a vk::raii::CommandBuffers commandBuffers
    vk::raii::CommandBuffer commandBuffer( std::move( commandBuffers[commandBufferIndex] ) );

    // start recording
    commandBuffer.begin();

There is one important thing to note, regarding command pool and command buffer handling. When you destroy a `VkCommandPool`, all `VkCommandBuffer`s allocated from that pool are implicitly freed. That automatism does not work well with the raii-approach. As the `vk::raii::CommandBuffers` are independent objects, they are not automatically destroyed when the `vk::raii::CommandPool` they are created from is destroyed. Instead, their destructor would try to use an invalid `vk::raii::CommandPool`, which obviously is an error.

To handle that correctly, you have to make sure, that all `vk::raii::CommandBuffers` generated from a `vk::raii::CommandPool` are explicitly destroyed before that `vk::raii::CommandPool` is destroyed!

### 05 Create a vk::raii::SwapchainKHR

To initialize a swap chain, you first instantiate a `vk::raii::SwapchainKHR`:

    // create a vk::raii::SwapchainKHR, given a vk::raii::Device device and a vk::SwapchainCreateInfoKHR swapChainCreateInfo
    vk::raii::SwapchainKHR swapchain( device, swapChainCreateInfo );

You can get an array of presentable images associated with that swap chain:

    // get presentable images associated with vk::raii::SwapchainKHR swapchain
    std::vector<VkImage> images = swapchain.getImages();

Note, that you don't get `vk::raii::Image`s here, but plain `VkImage`s. They are controlled by the swap chain, and you should not destroy them.

But you can create `vk::raii::ImageView`s out of them:

    // create a vk::raii::ImageView per VkImage, given a vk::raii::Device sevice, a vector of VkImages images and a vk::ImageViewCreateInfo imageViewCreateInfo
    std::vector<vk::raii::ImageView> imageViews;
    for ( auto image : images )
    {
      imageViewCreatInfo.image = image;
      imageViews.push_back( vk::raii::ImageView( device, imageViewCreateInfo ) );
    }

### 06 Create a Depth Buffer

For a depth buffer, you need an image and some device memory and bind the memory to that image. That is, you first create a vk::raii::Image

    // create a vk::raii::Image image, given a vk::raii::Device device and a vk::ImageCreateInfo imageCreateInfo
    // imageCreateInfo.usage should hold vk::ImageUsageFlagBits::eDepthStencilAttachment
    vk::raii::Image depthImage( device, imageCreateInfo );

To create the corresponding vk::raii::DeviceMemory, you should determine appropriate values for the vk::MemoryAllocateInfo. That is, get the memory requirements from the pDepthImage, and determine some memoryTypeIndex from the pPhysicalDevice's memory properties, requiring vk::MemoryPropertyFlagBits::eDeviceLocal.

    // get the vk::MemoryRequirements of the pDepthImage
    vk::MemoryRequirements memoryRequirements = depthImage.getMemoryRequirements();

    // determine appropriate memory type index, using some helper function determineMemoryTypeIndex
    vk::PhysicalDeviceMemoryProperties memoryProperties = physicalDevice.getMemoryProperties();
    uint32_t memoryTypeIndex = determineMemoryTypeIndex( memoryProperties, memoryRequirements.memoryTypeBits, vk::MemoryPropertyFlagBits::eDeviceLocal );

    // create a vk::raii::DeviceMemory depthDeviceMemory for the depth buffer
    vk::MemoryAllocateInfo memoryAllocateInfo( memoryRequirements.size, memoryTypeIndex );
    vk::raii::DeviceMemory depthDeviceMemory( device, memoryAllocateInfo );

Then you can bind the depth memory to the depth image

    // bind the pDepthMemory to the pDepthImage
    depthImage.bindMemory( *depthDeviceMemory, 0 );

Finally, you can create an image view on that depth buffer image

    // create a vk::raii::ImageView depthView, given a vk::ImageViewCreateInfo imageViewCreateInfo
    imageViewCreateInfo.image = *depthImage;
    vk::raii::ImageView depthImageView( device, imageViewCreateInfo );

### 07 Create a Uniform Buffer

Initializing a uniform buffer is very similar to initializing a depth buffer as described above. You just instantiate a `vk::raii::Buffer` instead of a `vk::raii::Image`, and a `vk::raii::DeviceMemory`, and bind the memory to the buffer:

    // create a vk::raii::Buffer, given a vk::raii::Device device and a vk::BufferCreateInfo bufferCreateInfo
    vk::raii::Buffer uniformBuffer( device, bufferCreateInfo );

    // get memoryRequirements for this uniform buffer
    vk::MemoryRequirements memoryRequirements = uniformBuffer.getMemoryRequirements();

    // determine appropriate memory type index, using some helper function, given a vk::raii::PhysicalDevice physicalDevice and some memoryPropertyFlags
    vk::PhysicalDeviceMemoryProperties memoryProperties = physicalDevice.getMemoryProperties();
    uint32_t memoryTypeIndex = determineMemoryTypeIndex( memoryProperties, memoryRequirements.memoryTypeBits, memoryPropertyFlags );
    
    // create a vk::raii::DeviceMemory uniformDeviceMemory for the uniform buffer
    vk::MemoryAllocateInfo memoryAllocateInfo( memoryRequirements.size, memoryTypeIndex );
    vk::raii::DeviceMemory uniformDeviceMemory( device, memoryAllocateInfo );
    
    // bind the vk::raii::DeviceMemory uniformDeviceMemory to the vk::raii::Buffer uniformBuffer
    uniformBuffer.bindMemory( *uniformDeviceMemory, 0 );

### 08 Create a vk::raii::PipelineLayout

To initialize a Pipeline Layout you just have to instantiate a `vk::raii::DescriptorSetLayout` and a `vk::raii::PipelineLayout` using that `vk::raii::DescriptorSetLayout`:

    // create a vk::raii::DescriptorSetLayout, given a vk::raii::Device device and a vk::DescriptorSetLayoutCreateInfo descriptorSetLayoutCreateInfo
    vk::raii::DescriptorSetLayout descriptorSetLayout( device, descriptorSetLayoutCreateInfo );

    // create a vk::raii::PipelineLayout, given a vk::raii::Device device and a vk::raii::DescriptorSetLayout
    vk::PipelineLayoutCreateInfo pipelineLayoutCreateInfo( {}, *descriptorSetLayout );
    vk::raii::PipelineLayout pipelineLayout( device, pipelineLayoutCreateInfo );

### 09 Create a vk::raii::DescriptorPool and vk::raii::DescriptorSets

The Descriptor Set handling with `vk::raii` requires some special handling that is not needed when using the pure C-API or the vk-namespace!

As a `vk::raii::DescriptorSet` object destroys itself in the destructor, you have to instantiate the corresponding `vk::raii::DescriptorPool` with the `vk::DescriptorPoolCreateInfo::flags` set to (at least) `vk::DescriptorPoolCreateFlagBits::eFreeDescriptorSet`. Otherwise, such individual destruction of a `vk::raii::DescriptorSet` would not be allowed!

That is, an instantiation of a `vk::raii::DescriptorPool` would look like this:

    // create a vk::raii::DescriptorPool, given a vk::raii::Device device and a vk::DescriptorPoolCreateInfo descriptorPoolCreateInfo
    assert( descriptorPoolCreateInfo.flags & vk::DescriptorPoolCreateFlagBits::eFreeDescriptorSet );
    vk::raii::DescriptorPool descriptorPool( device, descriptorPoolCreateInfo );

To actually instantiate a `vk::raii::DescriptorSet`, you need a `vk::raii::DescriptorPool`, as just described, and a `vk::raii::DescriptorSetLayout`, similar to the one described in the previous section.

Moreover, as the number of `vk::raii::DescriptorSet`s to allocate from a `vk::raii::DescriptorPool` is given by the number of `vk::DescriptorSetLayouts` held by a `vk::DescriptorSetAllocateInfo`, it can't be instantiated as a single object. Instead you get a `vk::raii::DescriptorSets` (note the trailing 's' here!), which essentially is a `std::vector` of `vk::raii::DescriptorSet`s (note the trailing 's' here!).

When you want to create just one `vk::raii::DescriptorSet`, using just one `vk::raii::DescriptorSetLayout`, your code might look like this:

    // create a vk::raii::DescriptorSets, holding a single vk::raii::DescriptorSet, given a vk::raii::Device device, a vk::raii::DescriptorPool descriptorPool, and a single vk::raii::DescriptorSetLayout descriptorSetLayout
    vk::DescriptorSetAllocateInfo descriptorSetAllocateInfo( *descriptorPool, *descriptorSetLayout );
    vk::raii::DescriptorSets pDescriptorSets( device, descriptorSetAllocateInfo );

And, again similar to the vk::raii::CommandBuffers handling described above, you can get one `vk::raii::DescriptorSet` out of a `vk::raii::DescriptorSets` like this:

    // get the vk::raii::DescriptorSet with index descriptorSetIndex, given a vk::raii::DescriptorSets descriptorSets
    vk::raii::DescriptorSet descriptorSet( std::move( descriptorSets[descriptorSetIndex] ) );

### 10 Create a vk::raii::RenderPass

Creating a `vk::raii::RenderPass` is pretty simple, given you already have a meaningful `vk::RenderPassCreateInfo`:

    // create a vk::raii::RenderPass, given a vk::raii::Device device and a vk::RenderPassCreateInfo renderPassCreateInfo
    vk::raii::RenderPass renderPass( device, renderPassCreateInfo );

### 11 Create a vk::raii::ShaderModule

Again, creating a `vk::raii::ShaderModule` is simple, given a `vk::ShaderModuleCreateInfo` with some meaningful code:

    // create a vk::raii::ShaderModule, given a vk::raii::Device device and a vk::ShaderModuleCreateInfo shaderModuleCreateInfo
    vk::raii::ShaderModule shaderModule( device, shaderModuleCreateInfo );

### 12 Create vk::raii::Framebuffers

If you have a `std::vector<vk::raii::ImageView>` as described in chapter 05 above, with one view per `VkImage` that you got from a `vk::raii::SwapchainKHR`; and one `vk::raii::ImageView` as described in chapter 06 above, which is a view on a `vk::raii::Image`, that is supposed to be a depth buffer, you can create a `vk::raii::Framebuffer` per swapchain image.

    // create a vector of vk::raii::Framebuffer, given a vk::raii::ImageView depthImageView, a vector of vk::raii::ImageView swapchainImageViews, a vk::raii::RenderPass renderPass, a vk::raii::Devie device, and some width and height
    // use the depth image view as the second attachment for each vk::raii::Framebuffer
    std::array<vk::ImageView, 2> attachments;
    attachments[1] = *depthImageView;
    std::vector<vk::raii::Framebuffer> framebuffers;
    for ( auto const & imageView : swapchainImageViews )
    {
      // use each image view from the swapchain as the first attachment
      attachments[0] = *imageView;
      vk::FramebufferCreateInfo framebufferCreateInfo( {}, *renderPass, attachments, width, height, 1 );
      framebuffers.push_back( vk::raii::Framebuffer( device, framebufferCreateInfo ) );
    }

### 13 Initialize a Vertex Buffer

To initialize a vertex buffer, you essentially have to combine some of the pieces described in the chapters before. First, you need to create a `vk::raii::Buffer` and a `vk::raii::DeviceMemory` and bind them:

    // create a vk::raii::Buffer vertexBuffer, given a vk::raii::Device device and some vertexData in host memory
    vk::BufferCreateInfo bufferCreateInfo( {}, sizeof( vertexData ), vk::BufferUsageFlagBits::eVertexBuffer );
    vk::raii::Buffer vertexBuffer( device, bufferCreateInfo );

    // create a vk::raii::DeviceMemory vertexDeviceMemory, given a vk::raii::Device device and a uint32_t memoryTypeIndex
    vk::MemoryRequirements memoryRequirements = vertexBuffer.getMemoryRequirements();
    vk::MemoryAllocateInfo memoryAllocateInfo( memoryRequirements.size, memoryTypeIndex );
    vk::raii::DeviceMemory vertexDeviceMemory( device, memoryAllocateInfo );

    // bind the complete device memory to the vertex buffer
    vertexBuffer.bindMemory( *vertexDeviceMemory, 0 );

    // copy the vertex data into the vertexDeviceMemory
    ...

Later on, you can bind that vertex buffer to a command buffer:

    // bind a complete single vk::raii::Buffer vertexBuffer as a vertex buffer, given a vk::raii::CommandBuffer commandBuffer
    commandBuffer.bindVertexBuffer( 0, { *vertexBuffer }, { 0 } );

### 14 Initialize a Graphics Pipeline

Initializing a graphics pipeline is not very raii-specific. Just instantiate it, provided you have a valid vk::GraphicsPipelineCreateInfo:

    // create a vk::raii::Pipeline, given a vk::raii::Device device and a vk::GraphicsPipelineCreateInfo graphicsPipelineCreateInfo
    vk::raii::Pipeline graphicsPipeline( device, graphicsPipelineCreateInfo );

The only thing to keep in mind here is the dereferencing of raii handles, like `pipelineLayout` or `renderPass` in the `vk::GraphicsPipelineCreateInfo`:

    vk::GraphicsPipelineCreateInfo graphicsPipelineCreateInfo(
      {},                                    // flags
      pipelineShaderStageCreateInfos,        // stages
      &pipelineVertexInputStateCreateInfo,   // pVertexInputState
      &pipelineInputAssemblyStateCreateInfo, // pInputAssemblyState
      nullptr,                               // pTessellationState
      &pipelineViewportStateCreateInfo,      // pViewportState
      &pipelineRasterizationStateCreateInfo, // pRasterizationState
      &pipelineMultisampleStateCreateInfo,   // pMultisampleState
      &pipelineDepthStencilStateCreateInfo,  // pDepthStencilState
      &pipelineColorBlendStateCreateInfo,    // pColorBlendState
      &pipelineDynamicStateCreateInfo,       // pDynamicState
      *pipelineLayout,                       // layout
      *renderPass                            // renderPass
    );

### 15 Drawing a Cube

Finally, we get all those pieces together and draw a cube.

To do so, you need a `vk::raii::Semaphore`:

    // create a vk::raii::Semaphore, given a vk::raii::Device
    vk::raii::Semaphore imageAcquiredSemphore( device, vk::SemaphoreCreateInfo() );

That semaphore can be used, to acquire the next imageIndex from the `vk::raii::SwapchainKHR` swapchain:

    vk::Result result;
    uint32_t imageIndex;
    std::tie( result, imageIndex ) = swapchain.acquireNextImage( timeout, *imageAcquiredSemaphore );

Note, `vk::raii::SwapchainKHR::acquireNextImage` returns a `std::pair<vk::Result, uint32_t>`, that can nicely be assigned onto two separate values using std::tie().

And also note, the returned `vk::Result` can not only be `vk::Result::eSuccess`, but also `vk::Result::eTimeout`, `vk::Result::eNotReady`, or `vk::Result::eSuboptimalKHR`, which should be handled here accordingly!

Next, you can record some commands into a `vk::raii::CommandBuffer`:

    // open the commandBuffer for recording
    commandBuffer.begin( {} );

    // initialize a vk::RenderPassBeginInfo with the current imageIndex and some appropriate renderArea and clearValues
    vk::RenderPassBeginInfo renderPassBeginInfo( *renderPass, *framebuffers[imageIndex], renderArea, clearValues );

    // begin the render pass with an inlined subpass; no secondary command buffers allowed
    commandBuffer.beginRenderPass( renderPassBeginInfo, vk::SubpassContents::eInline );

    // bind the graphics pipeline
    commandBuffer.bindPipeline( vk::PipelineBindPoint::eGraphics, *graphicsPipeline );

    // bind an appropriate descriptor set
    commandBuffer.bindDescriptorSets( vk::PipelineBindPoint::eGraphics, *pipelineLayout, 0, { *descriptorSet }, nullptr );

    // bind the vertex buffer
    commandBuffer.bindVertexBuffers( 0, { *vertexBuffer }, { 0 } );

    // set viewport and scissor
    commandBuffer.setViewport( 0, viewport );
    commandBuffer.setScissor( renderArea );

    // draw the 12 * 3 vertices once, starting with vertex 0 and instance 0
    commandBuffer.draw( 12 * 3, 1, 0, 0 );

    // end the render pass and stop recording
    commandBuffer.endRenderPass();
    commandBuffer.end();

To submit that command buffer to a `vk::raii::Queue` graphicsQueue you might want to use a `vk::raii::Fence`

    // create a vk::raii::Fence, given a vk::raii::Device device
    vk::raii::Fence fence( device, vk::FenceCreateInfo() );

With that, you can fill a `vk::SubmitInfo` and submit the command buffer

    vk::PipelineStageFlags waitDestinationStageMask( vk::PipelineStageFlagBits::eColorAttachmentOutput );
    vk::SubmitInfo submitInfo( *imageAcquiredSemaphore, waitDestinationStageMask, *commandBuffer );
    graphicsQueue.submit( submitInfo, *fence );

At some later point, you can wait for that submit being ready by waiting for the fence

    while ( vk::Result::eTimeout == device.waitForFences( { *fence }, VK_TRUE, timeout ) )
      ;

And finally, you can use the `vk::raii::Queue` presentQueue to, well, present that image

    vk::PresentInfoKHR presentInfoKHR( nullptr, *swapChain, imageIndex );
    result = presentQueue.presentKHR( presentInfoKHR );

Note here, again, that `result` can not only be `vk::Result::eSuccess`, but also `vk::Result::eSuboptimalKHR`, which should be handled accordingly.

## Conclusion

With the vk::raii namespace you've got a complete set of Vulkan handle wrapper classes following the RAII-paradigm. That is, they can easily be assigned to a smart pointer. And you can't miss their destruction.

Moreover, the actual function pointer handling is done automatically by `vk::raii::Context`, `vk::raii::Instance`, and `vk::raii::Device`. That is, you always use the correct device-specific functions, no matter how many devices you're using.

Note, though, that there are a few classes, like `vk::raii::CommandPool` and `vk::raii::DescriptorSet`, that need some special handling that deviates from what you can do with the pure C-API or the wrapper classes in the vk-namespace.
