SDL: not (just) a 2D graphics library
3 September 2019
My first real introduction with programming was with the C programming language, on a French website that was, at the time, known by the “Le Site Du Zéro” (think “The newbie’s website”).
At this time, I was in middle school, and I was pretty bored by it. It’s around that time that I started to have really access to the internet at home, and started spending a lot of time on it.
There were a few things behind this, mostly I was looking for trying to understand how video games works and how they were made. I was also trying to learn more about how computers work, without actually knowing what to look for, and I started dabbling into Linux in that time. This was around 2007.
This website had a well written, comprehensive, and actually fun “Introduction to C programming” tutorial. (They called them tutorials, but think of them more like courses…) Today, this website became “Open Classrooms”, a popular french MOOC platform, but the originals “tutos” are still up, and were (for some of them) improved, some turned into video courses.
This one was divided into 3 parts, one that is you “C programming 101” type of stuff, were they show you how to create variables, functions, if statements, loops, structures… This kind of things, the 2nd one is about more advanced things with pointers, memory allocations, arrays and whatnot, and the 3rd one is about showing you how to use a library, and takes example of the SDL to create a window, display things, and make a little sokoban game (with stolen Super Mario World sprites 😉).
In this thing, SDL is described as being a 2D graphics library for games, and for years, I regarded the SDL as being just that. I have no clue if other people had this misconception, but when I look for things about the SDL, I mostly see things about making 2D games with it, or seeing it merely as a way to get a window and a screen and not much else.
But, oh man. It’s so much more than that.
The SDL name did make little sense to me at that time, but I never really thought about it. SDL is the Simple Directmedia Layer. A better way of describing the SDL would be a “cross platform API for doing most of the things you would want to do with an OS, including drawing windows, creating threads, loading DLLs, and pretty much anything.
I’ve learned recently that it was developed to be used as an aid for porting software from windows to other platform. The main idea being to support functionalities in a convenient package that are analogue to what was available with Microsoft DirectX. This was developed by former Loki Software employee Sam Lantinga. The business-model of that company was to port video games from windows to other platforms, and mostly Linux.
The SDL works on pretty much anything you would want to use. Today, for me it looks more like a fundamental building block for multimedia programs (video games, and other interactive things with custom graphics), and without having to worry too much about the platform you are running into.
If you use the SDL, anything you do through it will work on a computer running Windows, MacOS, Linux, flavors of BSD, obscure little things like Haiku (Haiku is awesome. This is a really interesting operating system project), any kind of smartphone being Android or iOs, and probably much more things like video game consoles. All these platforms are available to you without having to change your code too much (not at all most of the time).
Since version 2.0 came out, the SDL is licensed under the zLib license. Before that, SDL was LGPL. LGPL is not a problem in commercial, closed source software (like video games usually are) when the library is dynamically linked to the program (for example, on Windows, the library is a .DLL file distributed alongside the binaries of the game.) This permit you to recompile and change the library, and the developers of the game needs to make the source code of the version used with the game available to you, including any changes they may have done to it, and under the same rights. This can make some company’s lawyers uneasy. the zLib license is a much shorter, much straightforward license that pretty much says “do whatever with the code of this, and credit about it is appreciated”
Also since version 2.0, the huge feature list of the library was expended further. The impressive feature list can be read here.
I spent quite some time misrepresenting what the SDL was, thinking that it was just a lousy 2D graphics libraries with a software renderer, and not the impressive tool that it actually is.
Few years ago, while searching content from Vavle about their SteamVR system, I stumbled across this talk by Ryan C. Gordon, a prolific freelance programmer that, if you ever ran a video game natively on Linux, there’s a pretty high chance he helped make this a reality. I really invite you to watch this, and appreciate all the hard work this simple C library can do for you in just a few lines…
As a side note, I really should plug a little project a good friend of mine started some time ago (and which I contribute to, because it’s awesome) to make a safe, C++17, RAII wrapper around most of the useful bits of SDL for 2D/OpenGL/Vulkan programming. Check it out here: https://github.com/Edhebi/cpp-sdl2