select_dxgi_adapter.cpp

// IDXGIFactory7は生成済み
ComPtr<IDXGIFactory7> p_factory;

// 実際にはグローバル変数ではなく，何らかのメンバ変数など
D3D_FEATURE_LEVEL minimum_feature_level = D3D_FEATURE_LEVEL_12_0;
ComPtr<ID3D12Device6> p_device;
ComPtr<IDXGIAdapter4> p_adapter;

bool selectAdapter()
{
    for(
        uint32_t i = 0;
        p_factory->EnumAdapterByGpuPreference(i, DXGI_GPU_PREFERENCE_HIGH_PERFORMANCE, IID_PPV_ARGS(&p_adapter) != DXGI_ERROR_NOT_FOUND;
        ++i
    )
    {
        DXGI_ADAPTER_DESC3 adapter_desc;
        HRESULT hr = p_adapter->GetDesc3(&adapter_desc);
        if(FAILED(hr) || (adapter_desc.Flags & DXGI_ADAPTER_FLAG3_SOFTWARE))
        {
            continue;
        }
    
        hr = D3D12CreateDevice(
            p_adapter.Get(),
            minimum_feature_level,
            __uuidof(*&p_device),
            nullptr
        );
        if(SUCCEEDED(hr))
        {
            return true;
        }
    }

    return false;
}