Function choose_shared_vulkan 

pub fn choose_shared_vulkan(
    policy: &AdapterPolicy,
    decode_allowed: bool,
    wanted: bool,
) -> Result<SharedVulkanChoice, SharedVulkanError>

Makes the shared Vulkan device on the adapter policy takes, ranked as every host ranks adapters (alpha2_gpu::rank_adapters): under auto, the adapter encoding the most codecs on the GPU, then one that decodes when decode_allowed, then high-performance order. Without wanted nothing is made and the report says where the product device renders.

If making the device fails, the failure goes into that adapter’s record and the choice runs again: auto tries the next capable adapter, while performance and a pin keep their adapter and render without a shared device.

Errors

Returns why there is no Vulkan instance to choose on.