I am writing a program to create an SDL3 window in C#.

I have compiled SDL3 2.30.5 code from the following repository: https://github.com/libsdl-org/SDL under Win x64 using Rider 2024.1.2.

Here is the code I’m trying to run:

using SDL3;

namespace SDL3Test
{
    class Program
    {
        private static bool _loop;

        static void Main(string[] args)
        {
            if (SDL.Init(SDL.InitFlags.Video) < 0)
            {
                Console.WriteLine($"SDL could not initialize! SDL_Error: {SDL.GetError()}");
                return;
            }

            var window = SDL.CreateWindow("SDL Create Window", 800, 600, SDL.WindowFlags.OpenGL);

            if (window == IntPtr.Zero)
            {
                Console.WriteLine($"Window could not be created! SDL_Error: {SDL.GetError()}");
                return;
            }

            _loop = true;

            while (_loop)
            {
                while (SDL.PollEvent(out var sdlEvent) != 0)
                {
                    if (sdlEvent == SDL.EventType.Quit)
                    {
                        _loop = false;
                    }
                }
            }

            SDL.DestroyWindow(window);

            Console.WriteLine($"SDL_Error: {SDL.GetError()}");

            SDL.Quit();
        }
    }
}

Here is the CreateWindow function:

[LibraryImport(SDLLibrary)]
[UnmanagedCallConv(CallConvs = new[] { typeof(System.Runtime.CompilerServices.CallConvCdecl) })]
private static unsafe partial IntPtr SDL_CreateWindow(byte* title, int w, int h, WindowFlags flags);

public static unsafe IntPtr CreateWindow(string? title, int w, int h, WindowFlags flags)
{
    var utf8TitleBufSize = Utf8Size(title);
    var utf8Title = stackalloc byte[utf8TitleBufSize];
    return SDL_CreateWindow(Utf8Encode(title, utf8Title, utf8TitleBufSize), w, h, flags);
}

And here’s the DestroyWindow function:

[LibraryImport(SDLLibrary, EntryPoint = "SDL_DestroyWindow")]
[UnmanagedCallConv(CallConvs = new[] { typeof(System.Runtime.CompilerServices.CallConvCdecl) })]
public static unsafe partial void DestroyWindow(IntPtr window);

Helper functions:

private static int Utf8Size(string? str)
{
    if (str == null)
    {
        return 0;
    }
    return str.Length * 4 + 1;
}

private static unsafe byte* Utf8Encode(string? str, byte* buffer, int bufferSize)
{
    if (str == null)
    {
        return (byte*)0;
    }
    fixed (char* strPtr = str)
    {
        Encoding.UTF8.GetBytes(strPtr, str.Length + 1, buffer, bufferSize);
    }
    return buffer;
}

private static unsafe string? UTF8_ToManaged(IntPtr s, bool freePtr = false)
{
    if (s == IntPtr.Zero) return null;

    var ptr = (byte*)s;
    while (*ptr != 0) ptr++;

    var result = Encoding.UTF8.GetString((byte*)s, (int)(ptr - (byte*)s));

    if (freePtr) Free(s);
    return result;
}

The problem is that when I call SDL.DestroyWindow(window);, I get the error SDL_Error: Invalid window through GetError.

What could be causing this issue?