VKSC needs the pipeline state to be represented in a format that can be used for offline compilation. For this purpose, the JSON format has been chosen. This page describes the usage of the JSON schema and code related tools. The JSON schema is a document that describes the format for the actual JSON data. Applications may choose to create this JSON data in several ways:

1. Using the generated code directly.
2. Hand-code the JSON data.
3. Using the JSON Generation layer (see https://github.com/KhronosGroup/VulkanTools-ForSC/blob/sc_main/layersvt/json_layer_README.md).

The existing Vulkan registry scripts have been used for generation of JSON related components. To generate the components, go into the xml folder in the VulkanSC repository.

cd xml

The entire vk.xml is generated as a schema, and the pipeline schema references this. We will have two schemas:

• vk.json (representing the whole vk.xml)
• vkpcc.json (representing the pipeline schema)
  

To generate the pipeline schema, do:
python ../scripts/genvk.py -o . vk.json

vkpcc.json is edited manually. The latest version is present under json/ directory.

There is provision to generate a .hpp that can be directly included in C++ applications, or plain .c/.h files can be generated as well.
python ../scripts/genvk.py -o . vulkan_json_data.hpp
python ../scripts/genvk.py -o . vulkan_json_gen.h
python ../scripts/genvk.py -o . vulkan_json_gen.c

This generates hpp code that can be used by applications to parse JSON files to directly get VK structures. This uses the open source framework jsoncpp to parse json fields, and then fill in the struct. To generate:
python ../scripts/genvk.py -o . vulkan_json_parser.hpp

The below shows an example of using the generated code to dump the json data. This is all handled in the layer if the layer approach is taken. The below example shows the plain C way.

    VkRenderPassCreateInfo rp;
    // App fills up the rp struct.

    // Dump data	
    print_VkRenderPassCreateInfo(rp, "Renderpass", 1);
    const char* json_output = getJSONOutput();

If the .hpp is used, the framework stores the data in vk_json::_string_stream. This can be used to write out the string.

The below shows an example of using the generated parser code to parse json data into Vulkan structs.

    std::ifstream ifs("pipeline.json");
    Json::CharReaderBuilder reader;
    Json::Value root;
    Json::String errorStr;

    // Parse entire file. 
    Json::parseFromStream(reader, ifs, &root, &errorStr);

    // Obtain sub fields from the parsed data.
    Json::Value& renderPass = root["Renderpass"]; 
  
    // Parse into Vulkan struct.
    VkRenderPassCreateInfo rp = {};
    vk_json_parser::parse_VkRenderPassCreateInfo("Renderpass", renderPass, rp);