_window.Initialize();

        _api = D3D9.GetApi(_window);
        _direct3d9 = _api.Direct3DCreate9(D3D9.SdkVersion);

        if (_direct3d9 is null)
        {
            throw new InvalidOperationException("Failed to create a D3D9 interface.");
        }

        PresentParameters presentationParameters = new()
        {
            Windowed = true,
            SwapEffect = Swapeffect.Discard,
            BackBufferFormat = Format.X8R8G8B8,
            BackBufferWidth = (uint)_window.Size.X,
            BackBufferHeight = (uint)_window.Size.Y,
            PresentationInterval = 0U,
            BackBufferCount = 1U,
            HDeviceWindow = _window.Native!.Win32!.Value.Hwnd
        };

        Caps9 capabilities = new();
        _direct3d9->GetDeviceCaps(Adapter: 0, Devtype.Hal, ref capabilities);

        uint deviceFlags = (uint)(capabilities.DevCaps != 0
            ? D3D9.CreateMultithreaded | D3D9.CreateHardwareVertexprocessing
            : D3D9.CreateMultithreaded | D3D9.CreateSoftwareVertexprocessing);

        fixed (IDirect3DDevice9* devicePtr = &_device)
        {
            _direct3d9->CreateDevice
            (
                Adapter: D3D9.AdapterDefault,
                DeviceType: Devtype.Hal,
                hFocusWindow: _window.Native!.Win32!.Value.Hwnd,
                BehaviorFlags: deviceFlags,
                pPresentationParameters: &presentationParameters,
                ppReturnedDeviceInterface: &devicePtr
            );
        }

        Vertexelement9[] vertexElements =
        [
            new Vertexelement9
            (
                stream: 0,
                offset: 0,
                type: (byte)Decltype.Float3,
                method: (byte)Declmethod.Default,
                usage: (byte)Declusage.Position,
                usageIndex: 0
            ),
            new Vertexelement9
            (
                stream: 0,
                offset: 12,
                type: (byte)Decltype.Float2,
                method: (byte)Declmethod.Default,
                usage: (byte)Declusage.Texcoord,
                usageIndex: 0
            ),
            new Vertexelement9 // D3DDECL_END() terminator.
            (
                stream: 0xFF,
                offset: 0,
                type: (byte)Decltype.Unused,
                method: 0,
                usage: 0,
                usageIndex: 0
            )
        ];

        IDirect3DVertexDeclaration9* vertexDeclarationPtr = null;

        fixed (Vertexelement9* vertexElementsPtr = vertexElements)
        {
            // NullReferenceException when the method below is called.
            _device.CreateVertexDeclaration(vertexElementsPtr, &vertexDeclarationPtr);
        }