A simple and useful game library in Go. Doc: https://godoc.org/github.com/faiface/gogame

go get github.com/faiface/gogame

This library is using SDL2 under the hood. That means that you need to have original SDL2 libraries installed. So far, these are required:

• SDL2
• SDL2_image
• SDL2_gfx

First, let's import Gogame.

import "github.com/faiface/gogame"

Before you use any of Gogame, you have to initialize it. If you're writing a game, that usually happens at the beginning of a program. When you're done with Gogame, you have to quit it.

func main() {
	gogame.Init()
	defer gogame.Quit()
}

If you've ever written a game, you surely are familiar with the "game loop" concept. Gogame manages this for you with gogame.Loop function. Let's take a look at it's signature:

func Loop(cfg Config, lf LoopFunc) error

Loop takes Config as it's first argument, and a LoopFunc as it's second argument. Config is basically a configuration of your game window and some additional settings. LoopFunc stands for:

type LoopFunc func(ctx Context)

Ok, so LoopFunc is a function that takes a gogame.Context. We'll see what it means later. Gogame will call this function at the every iteration of the game loop. gogame.Loop function basically works like this (pseudocode):

func Loop(cfg Config, lf LoopFunc) error {
	// make a game window

	for {
		// update input and output

		ctx := /* make context */
		lf(ctx)
	}
}

Let's make a Config and call gogame.Loop to start a game! For LoopFunc we'll use an anonymous function, to make it easier.

package main

import "github.com/faiface/gogame"

func main() {
	gogame.Init()
	defer gogame.Quit()

	cfg := gogame.Config{
		Title:       "Hello, Gogame!" // title of the game window
		Width:       1024,            // width of the game window
		Height:      768,             // height of the game window
		FPS:         60,              // our LoopFunc will be called 60 times per second
		QuitOnClose: true,            // whenever you close a window, game loop ends
	}

	gogame.Loop(cfg, func(ctx gogame.Context) {
		// nothing here yet
	})
}

When you run this program, you should see an empty black window with title "Hello, Gogame!". Great!

As you could see, LoopFunc has one argument: a Context. What is it? It is a way to interact with you game window. All the input from the mouse and keyboard, and all the drawing goes through a Context.

Gogame doesn't provide a traditional event system for input, because I don't think it's the best way to deal with input. Instead, it provides a set of methods that allow you to check the state of your input devices. For example, you can use ctx.KeyDown(gogame.KeyLeft) to check if the left arrow is pressed on you keyboard. Here's an incomplete overview of the methods. You can find all of them in the documentation of the gogame.Input interface.

gogame.Loop(cfg, func(ctx gogame.Context) {
	if ctx.KeyDown(gogame.KeyLeft) {
		fmt.Println("Left arrow is being pressed down!")
	}
	if ctx.KeyJustDown(gogame.KeySpace) {
		fmt.Println("You have just pressed space!")
	}
	if ctx.KeyJustUp(gogame.KeySpace) {
		fmt.Println("You have just released space!")
	}
	fmt.Println(ctx.MousePosition())
	if ctx.MouseJustDown(gogame.MouseLeft) {
		fmt.Println("Left mouse button just pressed!")
	}
	fmt.Println(ctx.WindowSize())
})

You can also use Context to do all kinds of graphical output (audio output is coming). Here's again an incomplete overview, you can find all of the methods in the documentation of gogame.Output interface.

gogame.Loop(cfg, func(ctx gogame.Context) {
	ctx.Clear(gogame.Colors["red"])
	ctx.DrawPicture(gogame.Rect{X: 100, Y: 100, W: 50, H: 50}, myDog)
	ctx.DrawLine(gogame.Vec{X: 100, Y: 100}, gogame.Vec{X: 500, Y: 400}, 10, gogame.Colors["red"])
})

Somewhere they are called 'images', elsewhere 'textures', even elsewhere 'surfaces', we call them pictures. You can load a picture from a file using gogame.LoadPicture function like this:

myDog := gogame.LoadPicture("data/mydog.png")

Then you can draw a picture onto the window using the ctx.DrawPicture method:

ctx.DrawPicture(gogame.Rect{X: 100, Y: 100, W: 50, H: 50}, myDog)

The picture will be stretched to fit the provided rectangle precisely.

Animations, cameras, canvases, ... look up the documentation (https://godoc.org/github.com/faiface/gogame)!

This library is currently heavily in development alongside my game.

It is by no means complete yet and may be changing in major ways.

Is very welcome! You can improve the documentation, open issues, and contribute code. Don't hesitate and do a pull request!