Let's concentrate on fixing the fullscreen mode and windowed mode in different resolutions this time.

Please note that to go fullscreen in this demo, you must change two lines in the ShootThemAllGame() constructor. Uncomment the line GoFullScreenWithResolution(720, 400); and comment out (REM) the GoWindowed(400, 400); line.

https://github.com/tornseglare/ShootThemAll/releases/tag/v1.4

We use GraphicsDeviceManager (our graphics variable) to make these changes. Theoretically, the minimum amount of code to go fullscreen with a given resolution are these four lines:

graphics.IsFullScreen = true;
graphics.PreferredBackBufferWidth = width;
graphics.PreferredBackBufferHeight = height;
graphics.ApplyChanges();

Sorry to say, as you can see in the image showing the actual code above, we must do this twice! This seems to be an old bug in monogame, and it might be a different case for your hardware. At least doing it this way causes no harm.

One more thing of interest is the HardwareModeSwitch. I set it already in the constructor when creating the graphics object. If set to true the switch is a bit slower but results in better performance in most hardware.

graphics = new GraphicsDeviceManager(this)
{
	HardwareModeSwitch = true // Try to set this to false.
};

This is almost identical to going fullscreen, except we set graphics.IsFullScreen to false. Just for the fun of it, we set the window position as well, with this.Window.Position = new Point(42, 42);, and allow the user to resize the window with this.Window.AllowUserResizing = true;.

You don't need any of these, but if you are interested or run into problems, these will aid you when debugging your code. Take a look in each event callback, especially the Graphics_DeviceReset(object sender, EventArgs e) might be interesting, put a breakpoint there and run the code.

The GraphicsAdapter.DefaultAdapter.SupportedDisplayModes give you a collection of the display modes your device supports in fullscreen mode.

My function SupportedDisplayModes() just prints them out for you in the debug console.

One possibility is to let the user choose among these resolutions in some settings dialog in your game.

Last I would like to mention this neat function:

It asks the default GraphicsAdapter for the current fullscreen resolution and tries to go fullscreen with this resolution. Usually this is the same resolution as your windows installation have.

I am not sure about this one, but if you have one graphic card, there is exactly one GraphicsAdapter, and that would be the GraphicsAdapter.DefaultAdapter. If you have several graphic cards I guess they would show up in the GraphicsAdapter.Adapters collection.