private readonly Platform_CreateWindow _createWindow;
private readonly Platform_DestroyWindow _destroyWindow;
private readonly Platform_GetWindowPos _getWindowPos;
private readonly Platform_ShowWindow _showWindow;
private readonly Platform_SetWindowPos _setWindowPos;
private readonly Platform_SetWindowSize _setWindowSize;
private readonly Platform_GetWindowSize _getWindowSize;
private readonly Platform_SetWindowFocus _setWindowFocus;
private readonly Platform_GetWindowFocus _getWindowFocus;
private readonly Platform_GetWindowMinimized _getWindowMinimized;
private readonly Platform_SetWindowTitle _setWindowTitle;

public ImGuiController(GL gl, IView view, IInputContext input)
{
    Init(gl, view, input);

    var io = ImGuiNET.ImGui.GetIO();

    io.Fonts.AddFontDefault();
    io.BackendFlags |= ImGuiBackendFlags.RendererHasVtxOffset;
    io.BackendFlags |= ImGuiBackendFlags.HasMouseCursors;
    io.BackendFlags |= ImGuiBackendFlags.HasSetMousePos;
    io.BackendFlags |= ImGuiBackendFlags.PlatformHasViewports;
    io.BackendFlags |= ImGuiBackendFlags.RendererHasViewports;

    io.ConfigFlags |= ImGuiConfigFlags.ViewportsEnable;
    io.ConfigFlags |= ImGuiConfigFlags.DockingEnable;

    var platformIO = ImGuiNET.ImGui.GetPlatformIO();
    var mainViewport = platformIO.MainViewport;
    mainViewport.PlatformHandle = view.Handle;

    var handle = GCHandle.Alloc(view);

    view.Resize += (size) => mainViewport.PlatformRequestResize = true;
    //view.Moved += p => mainViewport.PlatformRequestMove = true;
    view.Closing += () => mainViewport.PlatformRequestClose = true;

    mainViewport.PlatformUserData = (IntPtr)handle;

    _createWindow = CreateWindow;
    _destroyWindow = DestroyWindow;
    _getWindowPos = GetWindowPos;
    _showWindow = ShowWindow;
    _setWindowPos = SetWindowPos;
    _setWindowSize = SetWindowSize;
    _getWindowSize = GetWindowSize;
    _setWindowFocus = SetWindowFocus;
    _getWindowFocus = GetWindowFocus;
    _getWindowMinimized = GetWindowMinimized;
    _setWindowTitle = SetWindowTitle;

    platformIO.Platform_CreateWindow = Marshal.GetFunctionPointerForDelegate(_createWindow);
    platformIO.Platform_DestroyWindow = Marshal.GetFunctionPointerForDelegate(_destroyWindow);
    platformIO.Platform_ShowWindow = Marshal.GetFunctionPointerForDelegate(_showWindow);
    platformIO.Platform_SetWindowPos = Marshal.GetFunctionPointerForDelegate(_setWindowPos);
    platformIO.Platform_SetWindowSize = Marshal.GetFunctionPointerForDelegate(_setWindowSize);
    platformIO.Platform_SetWindowFocus = Marshal.GetFunctionPointerForDelegate(_setWindowFocus);
    platformIO.Platform_GetWindowFocus = Marshal.GetFunctionPointerForDelegate(_getWindowFocus);
    platformIO.Platform_GetWindowMinimized = Marshal.GetFunctionPointerForDelegate(_getWindowMinimized);
    platformIO.Platform_SetWindowTitle = Marshal.GetFunctionPointerForDelegate(_setWindowTitle);

    ImGuiNative.ImGuiPlatformIO_Set_Platform_GetWindowPos(platformIO.NativePtr, Marshal.GetFunctionPointerForDelegate(_getWindowPos));
    ImGuiNative.ImGuiPlatformIO_Set_Platform_GetWindowSize(platformIO.NativePtr, Marshal.GetFunctionPointerForDelegate(_getWindowSize));

    CreateDeviceResources();
    SetKeyMappings();

    SetPerFrameImGuiData(1f / 60f);

    BeginFrame();
}

private void CreateWindow(ImGuiViewportPtr vp)
{
    // VeldridImGuiWindow window = new VeldridImGuiWindow(_gd, vp);
}

private void DestroyWindow(ImGuiViewportPtr vp)
{
    // if (vp.PlatformUserData != IntPtr.Zero)
    // {
    //     VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    //     window.Dispose();

    //     vp.PlatformUserData = IntPtr.Zero;
    // }
}

private void ShowWindow(ImGuiViewportPtr vp)
{
    // VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    // Sdl2Native.SDL_ShowWindow(window.Window.SdlWindowHandle);
}

private unsafe void GetWindowPos(ImGuiViewportPtr vp, Vector2* outPos)
{
    // VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    // *outPos = new Vector2(window.Window.Bounds.X, window.Window.Bounds.Y);
}

private void SetWindowPos(ImGuiViewportPtr vp, Vector2 pos)
{
    // VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    // window.Window.X = (int)pos.X;
    // window.Window.Y = (int)pos.Y;
}

private void SetWindowSize(ImGuiViewportPtr vp, Vector2 size)
{
    // VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    // Sdl2Native.SDL_SetWindowSize(window.Window.SdlWindowHandle, (int)size.X, (int)size.Y);
}

private unsafe void GetWindowSize(ImGuiViewportPtr vp, Vector2* outSize)
{
    // VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    // Rectangle bounds = window.Window.Bounds;
    // *outSize = new Vector2(bounds.Width, bounds.Height);
}

private void SetWindowFocus(ImGuiViewportPtr vp)
{
    // if (p_sdl_RaiseWindow == null)
    // {
    //     p_sdl_RaiseWindow = Sdl2Native.LoadFunction<SDL_RaiseWindow_t>("SDL_RaiseWindow");
    // }

    // VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    // p_sdl_RaiseWindow(window.Window.SdlWindowHandle);
}

private byte GetWindowFocus(ImGuiViewportPtr vp)
{
    // VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    // SDL_WindowFlags flags = Sdl2Native.SDL_GetWindowFlags(window.Window.SdlWindowHandle);
    // return (flags & SDL_WindowFlags.InputFocus) != 0 ? (byte)1 : (byte)0;
}

private byte GetWindowMinimized(ImGuiViewportPtr vp)
{
    // VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    // SDL_WindowFlags flags = Sdl2Native.SDL_GetWindowFlags(window.Window.SdlWindowHandle);
    // return (flags & SDL_WindowFlags.Minimized) != 0 ? (byte)1 : (byte)0;
}

private unsafe void SetWindowTitle(ImGuiViewportPtr vp, IntPtr title)
{
    // VeldridImGuiWindow window = (VeldridImGuiWindow)GCHandle.FromIntPtr(vp.PlatformUserData).Target;
    // byte* titlePtr = (byte*)title;
    // int count = 0;
    // while (titlePtr[count] != 0)
    // {
    //     titlePtr += 1;
    // }
    // window.Window.Title = System.Text.Encoding.ASCII.GetString(titlePtr, count);
}