How to set the field of a union?

[eladmaimoni]

I have the following generated code:

#[repr(C)]
pub struct FlutterRendererConfig {
    pub type_: FlutterRendererType,
    pub __bindgen_anon_1: FlutterRendererConfig__bindgen_ty_1,
}
#[repr(C)]
pub struct FlutterRendererConfig__bindgen_ty_1 {
    pub open_gl: __BindgenUnionField<FlutterOpenGLRendererConfig>,
    pub software: __BindgenUnionField<FlutterSoftwareRendererConfig>,
    pub metal: __BindgenUnionField<FlutterMetalRendererConfig>,
    pub vulkan: __BindgenUnionField<FlutterVulkanRendererConfig>,
    pub bindgen_union_field: [u64; 14usize],
}

I tried various ways to set it, following the official docs and code I found online. all of them fail.

This is one of my attempts:

        let vulkan_config = FlutterVulkanRendererConfig {
            struct_size: size_of::<FlutterVulkanRendererConfig>(),
            version: raw_instance.version,
            instance: raw_instance.instance,
            physical_device: raw_device.physical_device,
            device: raw_device.device,
            queue_family_index: raw_device.queue_family_index,
            queue: raw_device.queue,
            enabled_instance_extension_count: raw_instance.extensions.len(),
            enabled_instance_extensions: enabled_instance_extensions.as_mut_ptr(),
            enabled_device_extension_count: raw_device.extensions.len(),
            enabled_device_extensions: enabled_device_extensions.as_mut_ptr(),
            get_instance_proc_address_callback: None,
            get_next_image_callback: None,
            present_image_callback: None,
        };
        let config = FlutterRendererConfig {
            type_: FlutterRendererType_kVulkan,
            __bindgen_anon_1: FlutterRendererConfig__bindgen_ty_1 {
                vulkan: vulkan_config,
            },
        };

which says:

error[E0308]: mismatched types
   --> src\application.rs:204:25
    |
204 |                 vulkan: vulkan_config,
    |                         ^^^^^^^^^^^^^ expected `__BindgenUnionField<FlutterVulkanRendererConfig>`, found `FlutterVulkanRendererConfig`

other methods I tried don't work either.

any help?

[eladmaimoni]

Ok, I managed to get this to compile:

        let mut config = FlutterRendererConfig::default();
        config.type_ = FlutterRendererType_kVulkan;
        let vk = unsafe { config.__bindgen_anon_1.vulkan.as_mut() };
        vk.struct_size = size_of::<FlutterVulkanRendererConfig>();
        vk.version = raw_instance.version;
        vk.instance = raw_instance.instance;
        vk.physical_device = raw_device.physical_device;
        vk.device = raw_device.device;
        vk.queue_family_index = raw_device.queue_family_index;
        vk.queue = raw_device.queue;
        vk.enabled_instance_extension_count = raw_instance.extensions.len();
        vk.enabled_instance_extensions = enabled_instance_extensions.as_mut_ptr();
        vk.enabled_device_extension_count = raw_device.extensions.len();
        vk.enabled_device_extensions = enabled_device_extensions.as_mut_ptr();
        vk.get_instance_proc_address_callback = None;
        vk.get_next_image_callback = None;
        vk.present_image_callback = None;

but would love to get some feedback on how to do this properly.