Program.cs

using System;
using System.IO;
using System.Runtime.InteropServices;

namespace SamuraiGunn2
{
    /// <summary>
    /// The main class.
    /// </summary>
    public static class Program
    {
        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool SetDefaultDllDirectories(int directoryFlags);

        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        static extern void AddDllDirectory(string lpPathName);

        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool SetDllDirectory(string lpPathName);

        const int LOAD_LIBRARY_SEARCH_DEFAULT_DIRS = 0x00001000;

        static void Main(string[] args)
        {
#if NETCOREAPP
            DllMap.Initialise(false);
#endif

            // https://github.com/FNA-XNA/FNA/wiki/4:-FNA-and-Windows-API#64-bit-support
            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
            {
                try
                {
                    SetDefaultDllDirectories(LOAD_LIBRARY_SEARCH_DEFAULT_DIRS);
                    AddDllDirectory(Path.Combine(
                        AppDomain.CurrentDomain.BaseDirectory,
                        Environment.Is64BitProcess ? "x64" : "x86"
                    ));
                }
                catch
                {
                    // Pre-Windows 7, KB2533623
                    SetDllDirectory(Path.Combine(
                        AppDomain.CurrentDomain.BaseDirectory,
                        Environment.Is64BitProcess ? "x64" : "x86"
                    ));
                }
            }

            // TODO: figure out why metal rendering causes a black screen

            var OSVersion = SDL2.SDL.SDL_GetPlatform();

            if (OSVersion.Equals("Mac OS X"))
            {
                // https://github.com/FNA-XNA/FNA/wiki/7:-FNA-Environment-Variables#fna_graphics_enable_highdpi
                // NOTE: from documentation:
                //       Lastly, when packaging for macOS, be sure this is in your app bundle's Info.plist:
                //           <key>NSHighResolutionCapable</key>
                //           <string>True</string>
                Environment.SetEnvironmentVariable("FNA_GRAPHICS_ENABLE_HIGHDPI", "1");

                Environment.SetEnvironmentVariable("FNA_GRAPHICS_FORCE_GLDEVICE", "MetalDevice");
                Environment.SetEnvironmentVariable("METAL_DEVICE_WRAPPER_TYPE", "1");
            }

            bool isHighDPI = Environment.GetEnvironmentVariable("FNA_GRAPHICS_ENABLE_HIGHDPI") == "1";
            if (isHighDPI)
                System.Console.WriteLine("HiDPI Enabled");

            using var game = new SamuraiGunnGame();
            game.Run();
        }
    }
}