Support Vulkan-Profiles

[charles-lunarg]

Allow a user to use a profile to feed vk-bootstrap's instance/device creation process. This should be straight forward as vk-bootstrap already contains all the necessary code to do the vulkan code, what is missing is the profile definition (json) -> vk-bootstrap. How this is achieved is yet to be determined.

Solutions include:

• Write a basic json parser in-source.
• Copy/paste an existing json parser into vk-bootstrap's source tree.
• Require an external dependency for json parsing.

Open Questions:

• Custom profiles? Extremely desirable but needs an interface to express them
  • Allow loading by file-path or only by passing a string?
• Copy/paste "standard" Vulkan-Profiles into vk-bootstrap (with auto-updating)? Alternatively don't provide any profiles by default.

[DethRaid]

Me providing custom profiles as a JSON string makes sense. Different platforms have different filesystem APIs, no need for you to handle all that

[GavinNL]

I don't know if this is worth doing, but LunarG provides some default profiles. Instead of having to write a JSON parser for your library, you can probably use a python script to read the provided json files and generate C++ functions which would return the
extensions/required device features.

I'm doing something similar, but I didn't write the code generator. I manually created the function that returns the profile information. See below:

struct VulkanProfile
{
    std::vector<char const*>         extensions;
    VkPhysicalDeviceFeatures          f10 = {};
    VkPhysicalDeviceVulkan11Features f11 = {};
    VkPhysicalDeviceVulkan12Features f12 = {};
    VkPhysicalDeviceVulkan13Features f13 = {};
};

// code-generated from VK_KHR_Roadman_2022.json
VulkanProfile VK_KHR_Roadmap_2022()
{
    VulkanProfile pro;

    {
        auto & req = pro.f10;
        req.robustBufferAccess = true;
        req.fullDrawIndexUint32 = true;
        req.imageCubeArray = true;
        req.independentBlend = true;
        req.sampleRateShading = true;
        req.drawIndirectFirstInstance = true;
        req.depthClamp = true;
        req.depthBiasClamp = true;
        req.samplerAnisotropy = true;
        req.occlusionQueryPrecise = true;
        req.fragmentStoresAndAtomics = true;
        req.shaderStorageImageExtendedFormats = true;
        req.shaderUniformBufferArrayDynamicIndexing = true;
        req.shaderSampledImageArrayDynamicIndexing = true;
        req.shaderStorageBufferArrayDynamicIndexing = true;
        req.shaderStorageImageArrayDynamicIndexing = true;
    }
    {
        auto & req = pro.f11;
        req.multiview = true;
        req.samplerYcbcrConversion = true;
    }
    
    {
        auto & req = pro.f12;
        req.uniformBufferStandardLayout = true;
        req.subgroupBroadcastDynamicId = true;
        req.imagelessFramebuffer = true;
        req.separateDepthStencilLayouts = true;
        req.hostQueryReset = true;
        req.timelineSemaphore = true;
        req.shaderSubgroupExtendedTypes = true;
        req.samplerMirrorClampToEdge = true;
        req.descriptorIndexing = true;
        req.shaderUniformTexelBufferArrayDynamicIndexing = true;
        req.shaderStorageTexelBufferArrayDynamicIndexing = true;
        req.shaderUniformBufferArrayNonUniformIndexing = true;
        req.shaderSampledImageArrayNonUniformIndexing = true;
        req.shaderStorageBufferArrayNonUniformIndexing = true;
        req.shaderStorageImageArrayNonUniformIndexing = true;
        req.shaderUniformTexelBufferArrayNonUniformIndexing = true;
        req.shaderStorageTexelBufferArrayNonUniformIndexing = true;
        req.descriptorBindingSampledImageUpdateAfterBind = true;
        req.descriptorBindingStorageImageUpdateAfterBind = true;
        req.descriptorBindingStorageBufferUpdateAfterBind = true;
        req.descriptorBindingUniformTexelBufferUpdateAfterBind = true;
        req.descriptorBindingStorageTexelBufferUpdateAfterBind = true;
        req.descriptorBindingUpdateUnusedWhilePending = true;
        req.descriptorBindingPartiallyBound = true;
        req.descriptorBindingVariableDescriptorCount = true;
        req.runtimeDescriptorArray = true;
        req.scalarBlockLayout = true;
        req.vulkanMemoryModel = true;
        req.vulkanMemoryModelDeviceScope = true;
        req.bufferDeviceAddress = true;
        req.vulkanMemoryModel = true;
        req.vulkanMemoryModelDeviceScope = true;
        req.vulkanMemoryModelAvailabilityVisibilityChains = true;
        req.bufferDeviceAddress = true;
    }
    {
        auto & req = pro.f13;
        req.robustImageAccess = true;
        req.shaderTerminateInvocation = true;
        req.shaderZeroInitializeWorkgroupMemory = true;
        req.synchronization2 = true;
        req.shaderIntegerDotProduct = true;
        req.maintenance4 = true;
        req.pipelineCreationCacheControl = true;
        req.subgroupSizeControl = true;
        req.computeFullSubgroups = true;
        req.shaderDemoteToHelperInvocation = true;
        req.inlineUniformBlock = true;
        req.dynamicRendering = true;
        req.robustImageAccess = true;
        req.shaderTerminateInvocation = true;
        req.shaderZeroInitializeWorkgroupMemory = true;
        req.synchronization2 = true;
        req.shaderIntegerDotProduct = true;
        req.maintenance4 = true;
        req.pipelineCreationCacheControl = true;
        req.subgroupSizeControl = true;
        req.computeFullSubgroups = true;
        req.shaderDemoteToHelperInvocation = true;
        req.inlineUniformBlock = true;
        req.descriptorBindingInlineUniformBlockUpdateAfterBind = true;
        req.descriptorBindingInlineUniformBlockUpdateAfterBind = true;
    }

    pro.extensions = {
        "VK_EXT_image_robustness",
        "VK_KHR_shader_non_semantic_info",
        "VK_KHR_shader_terminate_invocation",
        "VK_KHR_format_feature_flags2",
        "VK_KHR_zero_initialize_workgroup_memory",
        "VK_KHR_synchronization2",
        "VK_KHR_shader_integer_dot_product",
        "VK_KHR_maintenance4",
        "VK_EXT_4444_formats",
        "VK_EXT_extended_dynamic_state",
        "VK_EXT_extended_dynamic_state2",
        "VK_EXT_pipeline_creation_cache_control",
        "VK_EXT_subgroup_size_control",
        "VK_EXT_shader_demote_to_helper_invocation",
        "VK_EXT_inline_uniform_block",
        "VK_EXT_pipeline_creation_feedback",
        "VK_EXT_texel_buffer_alignment",
        "VK_EXT_ycbcr_2plane_444_formats",
        "VK_EXT_texture_compression_astc_hdr",
        "VK_EXT_tooling_info",
        "VK_EXT_private_data",
        "VK_KHR_dynamic_rendering",
        "VK_KHR_global_priority",
        "VK_EXT_inline_uniform_block"};

    return pro;
}

[charles-lunarg]

While there are some interesting solutions using C++ directly, I do think a simple JSON parser that can consume profiles directly is the best bet.

There seems to be a good open source json parser fit for this purpose: https://github.com/sheredom/json.h/tree/master

The license is permissive, it only uses a single allocation, and should be straight forward to integrate.

A definite requirement is generating the feature & properties struct parsing, as well as any other things profiles supports.