Using LibretroApi with MonoGame.Forms

CoreControl.cs

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using MonoGame.Forms.Controls;
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace LibMGTest
{
    public class CoreControl : UpdateWindow
    {
        Wrapper _libretro;

        private const string _core = "snes9x_libretro.dll";

        public int FrameBufferScale = 1;

        Texture2D _frameBuffer;
        SystemAVInfo _avinfo;

        private int _sampleRate;
        private int _channels = 2;
        private int _bufferSize = 300;
        private float[,] _workingBuffer;
        private byte[] _audioBuffer;
        private int bytesPerSample = 2;
        SoundEffect sound;

        private bool Initialized = false;
        private bool DrawFrameBuffer = true;

        protected override void Initialize()
        {
            base.Initialize();

            Editor.RenderTargetsRefreshed += Editor_RenderTargetsRefreshed;

            _libretro = new Wrapper(_core);
            _libretro.Init();
            _libretro.LoadGame("s2.sfc");
            _avinfo = _libretro.GetAVInfo();
            _frameBuffer = new Texture2D(GraphicsDevice, (int)_avinfo.geometry.base_width, (int)_avinfo.geometry.base_height);

            _sampleRate = (int)_libretro.GetAVInfo().timing.sample_rate;
            _audioBuffer = new byte[_channels * _bufferSize * bytesPerSample];
            _workingBuffer = new float[_channels, _bufferSize];

            sound = new SoundEffect(_audioBuffer, _sampleRate, AudioChannels.Stereo);

            Editor.ShowFPS = true;
            Editor.ShowCursorPosition = false;
            Editor.SetDisplayStyle = MonoGame.Forms.Services.GFXService.DisplayStyle.TopRight;

            Initialized = true;
        }

        private void Editor_RenderTargetsRefreshed()
        {
            DrawFrameBuffer = true;
        }

        protected override void OnResize(EventArgs e)
        {
            base.OnResize(e);

            if (Initialized) DrawFrameBuffer = false;
        }

        protected override void Update(GameTime gameTime)
        {
            Libretro.RetroSetInputState(RetroInputState);

            _libretro.Update();

            SubmitBuffer();
            sound.Play();

            base.Update(gameTime);
        }

        protected override void Draw()
        {
            base.Draw();

            Editor.spriteBatch.Begin();

            if (DrawFrameBuffer) _frameBuffer.SetData(ProcessFramebuffer(_libretro.GetFramebuffer(), (uint)_libretro.GetAVInfo().geometry.base_width, (uint)_libretro.GetAVInfo().geometry.base_height));

            Editor.spriteBatch.Draw(_frameBuffer, new Rectangle(
                (Editor.graphics.PresentationParameters.BackBufferWidth / 2) - ((int)_avinfo.geometry.base_width * FrameBufferScale) / 2,
                (Editor.graphics.PresentationParameters.BackBufferHeight / 2) - ((int)_avinfo.geometry.base_height * FrameBufferScale) / 2,
                (int)_avinfo.geometry.base_width * FrameBufferScale, 
                (int)_avinfo.geometry.base_height * FrameBufferScale), Color.White);
            
            Editor.spriteBatch.DrawString(Editor.Font, "XBOX-360 Controller Input", new Vector2(10, 10), Color.Yellow);

            Editor.spriteBatch.End();

            Editor.DrawDisplay();
        }

        protected Color[] ProcessFramebuffer(Pixel[] frameBuffer, uint width, uint height)
        {
            Color[] image = new Color[width * height];
            if (frameBuffer != null)
            {
                image = new Color[width * height];

                for (int i = 0; i < width * height; i++)
                {
                    if (frameBuffer[i] != null)
                    {
                        image[i] = new Color(frameBuffer[i].Red, frameBuffer[i].Green, frameBuffer[i].Blue);
                        frameBuffer[i] = null;
                    }
                }
            }
            return image;
        }

        private void FillWorkingBuffer()
        {
            IntPtr data;
            data = _libretro.GetSoundBuffer().data;
            int i;

            for (i = 0; i < _libretro.GetSoundBuffer().frames; i++)
            {
                short chunk = Marshal.ReadInt16(data);
                _workingBuffer[0, i] = (float)chunk / short.MaxValue;
                data = data + (sizeof(short));

                chunk = Marshal.ReadInt16(data);
                _workingBuffer[1, i] = (float)chunk / short.MaxValue;
                data = data + (sizeof(short));
            }
        }

        private void SubmitBuffer()
        {
            FillWorkingBuffer();
            ConvertBuffer(_workingBuffer, _audioBuffer);
        }

        /// <summary>
        /// Converts a bi-dimensional (Channel, Samples) floating point buffer to a PCM (byte) buffer with interleaved channels
        /// </summary>
        private void ConvertBuffer(float[,] from, byte[] to)
        {
            const int bytesPerSample = 2;
            int channels = from.GetLength(0);
            int bufferSize = from.GetLength(1);

            // Make sure the buffer sizes are correct
            Debug.Assert(to.Length == bufferSize * channels * bytesPerSample, "Buffer sizes are mismatched.");
            for (int i = 0; i < bufferSize; i++)
            {
                for (int c = 0; c < channels; c++)
                {
                    // First clamp the value to the [-1.0..1.0] range
                    float floatSample = MathHelper.Clamp(from[c, i], -1.0f, 1.0f);

                    // Convert it to the 16 bit [short.MinValue..short.MaxValue] range
                    short shortSample = (short)(floatSample >= 0.0f ? floatSample * short.MaxValue : floatSample * short.MinValue * -1);

                    // Calculate the right index based on the PCM format of interleaved samples per channel [L-R-L-R]
                    int index = i * channels * bytesPerSample + c * bytesPerSample;

                    // Store the 16 bit sample as two consecutive 8 bit values in the buffer with regard to endian-ness
                    if (!BitConverter.IsLittleEndian)
                    {
                        to[index] = (byte)(shortSample >> 8);
                        to[index + 1] = (byte)shortSample;
                    }
                    else
                    {
                        to[index] = (byte)shortSample;
                        to[index + 1] = (byte)(shortSample >> 8);
                    }
                }
            }

        }

        public static unsafe short RetroInputState(uint port, uint device, uint index, uint id)
        {
            //port = 1;
            //device = 1;

            if (id == 0) return GamePad.GetState((int)port).Buttons.A == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 1) return GamePad.GetState((int)port).Buttons.X == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 2) return GamePad.GetState((int)port).Buttons.Back == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 3) return GamePad.GetState((int)port).Buttons.Start == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 4) return GamePad.GetState((int)port).DPad.Up == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 5) return GamePad.GetState((int)port).DPad.Down == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 6) return GamePad.GetState((int)port).DPad.Left == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 7) return GamePad.GetState((int)port).DPad.Right == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 8) return GamePad.GetState((int)port).Buttons.B == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 9) return GamePad.GetState((int)port).Buttons.Y == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 10) return GamePad.GetState((int)port).Buttons.LeftShoulder == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 11) return GamePad.GetState((int)port).Buttons.RightShoulder == ButtonState.Pressed ? (short)1 : (short)0;
            if (id == 12) return GamePad.GetState((int)port).Buttons.LeftStick == ButtonState.Pressed ? (short)1 : (short)0;

            return 0;
        }

        //public static float[] RetroAudio = new float[2048];
        //public static int batch = 0;
        //public static bool leftspeaker = true;
        //public static float[] myAudio = new float[2048];
        //private unsafe void RetroAudioSampleBatch(Int16* data, uint frames)
        //{
        //    // Unity plays audio at 44100Hz, Snes = 32000Hz. So the output of this code
        //    // is really High-pitched.. To make it sound normal I adjusted the AudioSource's
        //    // 'Pitch' value to 0.33f on each Speaker;
        //    for (int i = 0; i < (int)frames; i++)
        //    {
        //        Int16 chunk = Marshal.ReadInt16((IntPtr)data);
        //        data = data + (sizeof(Int16));
        //        float value = (((float)chunk * 0.5f)) / 32768.0f;
        //        if (value > 1.0f) value = 1.0f;
        //        if (value < -1.0f) value = -1.0f;
        //        //value = value * 0.9f;

        //        if (leftspeaker == true)
        //        {
        //            RetroAudio[batch] = value;
        //            batch++;
        //        }
        //        if (leftspeaker == false)
        //        {
        //            RetroAudio[batch] = value;
        //            batch++;
        //        }
        //        leftspeaker = !leftspeaker;

        //        if (batch >= 2048)
        //        {
        //            myAudio = RetroAudio;
        //            batch = 0;
        //        }
        //    }

        //    //short converted = BitConverter.ToInt16(RetroAudio);

        //    return;
        //}
    }
}