2b: Building New Games with FNA

Before You Start

This is strictly a tutorial about using FNA. It is NOT a C# tutorial! If you are learning C# for the first time, use Microsoft's official Introduction to C# on MSDN first before continuing on.

Also, be sure to finish Page 1 before starting this page!

What is XNA?

XNA was, at its core, the software equivalent of an 80's Saturday morning cartoon based on a toy line: A massive advertisement masquerading as a real product. It was built to advertise many new (at the time) products in development at Microsoft:

• C# 2.0
• Direct3D Effects Framework
• XACT Audio Creation Tool
• XInput and the Xbox 360 Controller
• Xbox 360 + Windows Media Center

From 2006 to 2010, Microsoft maintained XNA as a means of allowing independent game developers to ship small games written in C# on Xbox 360, via the "Xbox Live Indie Games" marketplace. The final XNA release also supported building for Windows Phone 7 devices.

As for the XNA API, it was largely a C# wrapper for various DirectX components, but not quite all of them - many features are unavailable in favor of the aforementioned new-fangled DirectX products. For example, while there is a GraphicsDevice class that effectively acts as a 1:1 map of ID3D10Device, notably missing is support for low-level shaders and constant buffers; instead you are expected to use Effects for shader support.

XNA was officially discontinued in 2012, and the Xbox Live Indie Games marketplace was shut down on November 2017.

What is FNA?

FNA is a preservation project designed to accurately reimplement the XNA runtime libraries. When you have an XNA game, you should be able to take the source, compile it against FNA, and have a fully-functioning port. At its core, FNA is a portability library, but many continue to develop new games with FNA. This tutorial will help you make your own FNA games, without needing XNA as a prerequisite. If you are bringing an existing XNA game to FNA, follow this wiki page instead.

Your First Game

See Page 1 for a quick refresher on making new projects. Once you have a project made, you can then proceed:

The First Program

This is the smallest possible program using the framework portion of XNA:

using System;
using Microsoft.Xna.Framework;

static class Program
{
    [STAThread]
    static void Main(string[] args)
    {
        using (Game g = new Game())
        {
            new GraphicsDeviceManager(g);
            g.Run();
        }
    }
}

This should compile into a folder like bin/Debug/. Next to your executable, you will put the native libraries you downloaded earlier into this folder. You only need to worry about the libraries for your development platform; the rest will be for when you distribute your game. For example, if you're building an AnyCPU program on Windows x64, you would take the contents of the native library archive's x64 folder and put them next to your exe.

When using a developer environment on macOS, you will want to add an environment variable that sets DYLD_LIBRARY_PATH=./osx/ (or wherever your dylib files are), so that the IDE's runtime environment will find the fnalibs binaries.

When running this program, you might see some random trash in the window; that is most likely old graphics memory from another program you were running. Aside from that, the game is fully functional; it is reading input, running updates, and presenting frames to the window. But if this is the whole program, where do we put the rest of the game?

The First Game Object

The trick is that you're not going to create a Game directly. Instead, you're going to inherit it!

using System;
using Microsoft.Xna.Framework;

class FNAGame : Game
{
    [STAThread]
    static void Main(string[] args)
    {
        using (FNAGame g = new FNAGame())
        {
            g.Run();
        }
    }

    private FNAGame()
    {
        // This gets assigned to something internally, don't worry...
        new GraphicsDeviceManager(this);
    }
}

But again, there's still no place to put the game. That's because Game has several protected methods that you are meant to implement. Here's what it looks like with the most commonly-used methods:

using System;
using Microsoft.Xna.Framework;

class FNAGame : Game
{
    [STAThread]
    static void Main(string[] args)
    {
        using (FNAGame g = new FNAGame())
        {
            g.Run();
        }
    }

    private FNAGame()
    {
        GraphicsDeviceManager gdm = new GraphicsDeviceManager(this);

        // Typically you would load a config here...
        gdm.PreferredBackBufferWidth = 1280;
        gdm.PreferredBackBufferHeight = 720;
        gdm.IsFullScreen = false;
        gdm.SynchronizeWithVerticalRetrace = true;
    }

    protected override void Initialize()
    {
        /* This is a nice place to start up the engine, after
         * loading configuration stuff in the constructor
         */
        base.Initialize();
    }

    protected override void LoadContent()
    {
        // Load textures, sounds, and so on in here...
        base.LoadContent();
    }

    protected override void UnloadContent()
    {
        // Clean up after yourself!
        base.UnloadContent();
    }

    protected override void Update(GameTime gameTime)
    {
        // Run game logic in here. Do NOT render anything here!
        base.Update(gameTime);
    }

    protected override void Draw(GameTime gameTime)
    {
        // Render stuff in here. Do NOT run game logic in here!
        GraphicsDevice.Clear(Color.CornflowerBlue);
        base.Draw(gameTime);
    }
}

The First Input

It's not a game without input, right? FNA exposes GamePad, Keyboard, and Mouse for user input. There is also a Microsoft.Xna.Framework.Input.Touch namespace for touch screen support.

Input isn't terribly complicated; you store two copies of input state, one for current input and another for previous input. This lets you detect presses and releases, in addition to just checking for a button being down:

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Input;

class FNAGame : Game
{
    [STAThread]
    static void Main(string[] args)
    {
        using (FNAGame g = new FNAGame())
        {
            g.Run();
        }
    }

    private KeyboardState keyboardPrev = new KeyboardState();
    private MouseState mousePrev = new MouseState();
    private GamePadState gpPrev = new GamePadState();

    private FNAGame()
    {
        new GraphicsDeviceManager(this);
    }

    protected override void Update(GameTime gameTime)
    {
        // Poll input
        KeyboardState keyboardCur = Keyboard.GetState();
        MouseState mouseCur = Mouse.GetState();
        GamePadState gpCur = GamePad.GetState(PlayerIndex.One);

        // Check for presses
        if (keyboardCur.IsKeyDown(Keys.Space) && keyboardPrev.IsKeyUp(Keys.Space))
        {
            System.Console.WriteLine("Space bar was pressed!");
        }
        if (mouseCur.RightButton == ButtonState.Released && mousePrev.RightButton == ButtonState.Pressed)
        {
            System.Console.WriteLine("Right mouse button was released!");
        }
        if (gpCur.Buttons.A == ButtonState.Pressed && gpPrev.Buttons.A == ButtonState.Pressed)
        {
            System.Console.WriteLine("A button is being held!");
        }

        // Current is now previous!
        keyboardPrev = keyboardCur;
        mousePrev = mouseCur;
        gpPrev = gpCur;

        base.Update(gameTime);
    }

    protected override void Draw(GameTime gameTime)
    {
        GraphicsDevice.Clear(Color.CornflowerBlue);
        base.Draw(gameTime);
    }
}

Be sure to read all of the input APIs for more details! You may also be interested in some extensions to the XNA spec that improve input support in FNA.

The First Sprite

Finally, some graphics! In XNA, there is a class called SpriteBatch that makes sprite drawing relatively easy. Combine that with your own textures and you have the foundation of a 2D renderer.

This sample loads a PNG named "FNATexture", located in a "Content" folder, and renders it with a SpriteBatch:

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

class FNAGame : Game
{
    [STAThread]
    static void Main(string[] args)
    {
        using (FNAGame g = new FNAGame())
        {
            g.Run();
        }
    }

    private SpriteBatch batch;
    private Texture2D texture;

    private FNAGame()
    {
        new GraphicsDeviceManager(this);

        // All content loaded will be in a "Content" folder
        Content.RootDirectory = "Content";
    }

    protected override void LoadContent()
    {
        // Create the batch...
        batch = new SpriteBatch(GraphicsDevice);

        // ... then load a texture from ./Content/FNATexture.png
        texture = Content.Load<Texture2D>("FNATexture");
    }

    protected override void UnloadContent()
    {
        batch.Dispose();
        texture.Dispose();
    }

    protected override void Draw(GameTime gameTime)
    {
        GraphicsDevice.Clear(Color.CornflowerBlue);

        // Draw the texture to the corner of the screen
        batch.Begin();
        batch.Draw(texture, Vector2.Zero, Color.White);
        batch.End();

        base.Draw(gameTime);
    }
}

If all went well, the PNG you chose should now be displayed! When drawing sprites, be absolutely sure that you draw as many as you possibly can before calling End(); batches are meant to be large, singular groups rather than lots of small, fragmented groups. The more you put in a single batch, the better your program will perform.

And whatever you do, do NOT use SpriteSortMode.Immediate!

The First Sound

In addition to XACT, there is also a SoundEffect API available. It's as simple as loading a .wav file and mashing Play():

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Input;

class FNAGame : Game
{
    [STAThread]
    static void Main(string[] args)
    {
        using (FNAGame g = new FNAGame())
        {
            g.Run();
        }
    }

    private SoundEffect sound;
    private KeyboardState keyboardPrev = new KeyboardState();

    private FNAGame()
    {
        new GraphicsDeviceManager(this);

        // All content loaded will be in a "Content" folder
        Content.RootDirectory = "Content";
    }

    protected override void LoadContent()
    {
        // Sound is ./Content/FNASound.wav
        sound = Content.Load<SoundEffect>("FNASound");
    }

    protected override void UnloadContent()
    {
        sound.Dispose();
    }

    protected override void Update(GameTime gameTime)
    {
        KeyboardState keyboardCur = Keyboard.GetState();

        if (keyboardCur.IsKeyDown(Keys.Space) && keyboardPrev.IsKeyUp(Keys.Space))
        {
            sound.Play();
        }

        keyboardPrev = keyboardCur;
    }

    protected override void Draw(GameTime gameTime)
    {
        GraphicsDevice.Clear(Color.CornflowerBlue);
        base.Draw(gameTime);
    }
}

There is lots of deeper functionality, including instance management, 3D audio APIs, and even a streaming sound object, useful for streaming from larger files (for example, sending decoded data from an Ogg Vorbis music file).

The First Song

XNA includes a Media namespace, which includes support for basic playback of music and video files. FNA supports Ogg Vorbis and QOA for the Song implementation:

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Media;

class FNAGame : Game
{
    [STAThread]
    static void Main(string[] args)
    {
        using (FNAGame g = new FNAGame())
        {
            g.Run();
        }
    }

    private Song song;

    private FNAGame()
    {
        new GraphicsDeviceManager(this);

        // All content loaded will be in a "Content" folder
        Content.RootDirectory = "Content";
    }

    protected override void LoadContent()
    {
        // Song is ./Content/FNASong.ogg
        song = Content.Load<Song>("FNASong");
    }

    protected override void UnloadContent()
    {
        song.Dispose();
    }

    protected override void Update(GameTime gameTime)
    {
        // Just keep playing the song over and over
        if (MediaPlayer.State == MediaState.Stopped)
        {
            MediaPlayer.Play(song);
        }
        base.Update(gameTime);
    }

    protected override void Draw(GameTime gameTime)
    {
        GraphicsDevice.Clear(Color.CornflowerBlue);
        base.Draw(gameTime);
    }
}

The First Video

Video objects are a fair bit more involved than Song. In addition to playing the sound, a VideoPlayer will provide the frames in the form of a texture, which you can then render however you like:

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Media;
using Microsoft.Xna.Framework.Graphics;

class FNAGame : Game
{
    [STAThread]
    static void Main(string[] args)
    {
        using (FNAGame g = new FNAGame())
        {
            g.Run();
        }
    }

    private GraphicsDeviceManager gdm;
    private Video video;
    private VideoPlayer videoPlayer;
    private SpriteBatch batch;

    private FNAGame()
    {
        gdm = new GraphicsDeviceManager(this);

        // All content loaded will be in a "Content" folder
        Content.RootDirectory = "Content";
    }

    protected override void LoadContent()
    {
        // Video is ./Content/FNAVideo.ogv
        video = Content.Load<Video>("FNAVideo");
        batch = new SpriteBatch(GraphicsDevice);

        gdm.PreferredBackBufferWidth = video.Width;
        gdm.PreferredBackBufferHeight = video.Height;
        gdm.ApplyChanges();

        // Just loop the video over and over
        videoPlayer = new VideoPlayer();
        videoPlayer.IsLooped = true;
        videoPlayer.Play(video);
    }

    protected override void UnloadContent()
    {
        batch.Dispose();
        videoPlayer.Dispose();
        video = null;
    }

    protected override void Draw(GameTime gameTime)
    {
        // Draw the video frame to the window, which should be the same size
        batch.Begin(SpriteSortMode.Deferred, BlendState.Opaque);
        batch.Draw(videoPlayer.GetTexture(), Vector2.Zero, Color.White);
        batch.End();
        base.Draw(gameTime);
    }
}

The First Save

XNA provides two filesystem APIs: TitleContainer and StorageContainer. TitleContainer is how you should open files in the game folder (provided Content.Load() does not do what you want), and is pretty much exactly the same as File.OpenRead. StorageContainer is a lot more involved, however:

using System;
using Microsoft.Xna.Framework.Storage;

void DoStorageContainerThing()
{
    IAsyncResult result;

    result = StorageDevice.BeginShowSelector(null, null);
    while (!result.IsCompleted)
    {
        // Just hang out for a bit...
        System.Threading.Thread.Sleep(1);
    }
    StorageDevice device = StorageDevice.EndShowSelector(result);

    result = device.BeginOpenContainer("SaveData", null, null);
    while (!result.IsCompleted)
    {
        // Just hang out for a bit...
        System.Threading.Thread.Sleep(1);
    }
    StorageContainer container = device.EndOpenContainer(result);

    // Do stuff!

    // Clean up after yourself! Maybe keep `device` from getting collected.
    container.Dispose();
}

From there, container's API is self-explanatory. There are Create/Delete/Exists/Open/GetNames APIs for directories and files. Pretty much what you'd expect!

The container's path is $SAVELOC/$CONTAINERNAME/$PLAYERINDEX:

• $SAVELOC looks something like this... and before you ask, yes, XNA really based the save folder on the EXE name:

string platform = SDL.SDL_GetPlatform();
string exeName = Path.GetFileNameWithoutExtension(
    AppDomain.CurrentDomain.FriendlyName
).Replace(".vshost", "");
if (platform.Equals("Windows"))
{
    return Path.Combine(
        Environment.GetFolderPath(
            Environment.SpecialFolder.MyDocuments
        ),
        "SavedGames",
        exeName
    );
}
if (platform.Equals("Mac OS X"))
{
    string osConfigDir = Environment.GetEnvironmentVariable("HOME");
    if (String.IsNullOrEmpty(osConfigDir))
    {
        return "."; // Oh well.
    }
    return Path.Combine(
        osConfigDir,
        "Library/Application Support",
        exeName
    );
}
if (    platform.Equals("Linux") ||
    platform.Equals("FreeBSD") ||
    platform.Equals("OpenBSD") ||
    platform.Equals("NetBSD")   )
{
    string osConfigDir = Environment.GetEnvironmentVariable("XDG_DATA_HOME");
    if (String.IsNullOrEmpty(osConfigDir))
    {
        osConfigDir = Environment.GetEnvironmentVariable("HOME");
        if (String.IsNullOrEmpty(osConfigDir))
        {
            return "."; // Oh well.
        }
        osConfigDir += "/.local/share";
    }
    return Path.Combine(osConfigDir, exeName);
}
return SDL.SDL_GetPrefPath(null, exeName);

• $CONTAINERNAME is the name you passed to BeginOpenContainer.
• $PLAYERINDEX is either AllPlayers if you didn't pass a PlayerIndex, or Player1 through Player4.

The First Effect

NOTE: This is an advanced subject! You may want to read the official Effects documentation first.

XNA and FNA use Direct3D Effects for shader support. Effects are groups of HLSL shaders bundled together into one file, which can be executed in separate subgroups called "techniques" and "passes". The XNA API is slightly dumbed down compared to the stock Effects API:

using Microsoft.Xna.Framework.Graphics;

// Effects can be loaded as content!
Effect effect = Content.Load<Effect>("FNAEffect");

// You can set parameters...
effect.Parameters["MadeUpParameter"].SetValue(0.0f);

// Set techniques...
effect.CurrentTechnique = effect.Techniques["MadeUpTechnique"];

// ... and then render each pass in the technique!
foreach (EffectPass p in effect.CurrentTechnique.Passes)
{
    p.Apply(); // Sets the shaders, passes the parameters
    GraphicsDevice.DrawIndexedPrimitives(...);
}

// Clean up after yourself!
effect.Dispose();

XNA has multiple effects built in, for those who just want basic rendering without having to write shaders. Examples include BasicEffect, AlphaTestEffect, and EnvironmentMapEffect.

When writing your own Effects, you must precompile them first. This is done with FXC, the Microsoft DirectX Shader Compiler, which you can find in the DirectX SDK. To compile .fx files:

fxc.exe /T fx_2_0 FNAEffect.fx /Fo FNAEffect.fxb

Note that FXC works with Wine, so on Linux and macOS you can still develop shaders by calling wine fxc.exe.

To see some examples of .fx files, look at the stock effects!