Right now I’m aware of these translation projects that provide SDL2 units (if you know a further one, let me know):
|Tim Blume's SDL 2.0 units||Pure translation of SDL 2.0 source files. The original, modular structure of the header files is preserved, so the SDL2.pas is composed of many include files. Translations of SDL2_mixer, SDL2_ttf and SDL2_image are available, SDL_net seems to be missing so far. It provides MacOS X support.|
|Imants Gulis' SDL 2.0 units||Heavily modified SDL 2.0 units to allow for dynamic loading of the library.|
|Bare Game Library||Bare Game is a game library which is put on top of the SDL2 library. It also allows for easy combination of SDL2 with Lazarus, which is a great plus. [Official website (baregame.org) is down, is the project dead?]|
Now we go for a detailed discussion of them.
Modified header translations
Well, the Bare Game Library is a great project and I like the idea to provide an easy-to-use game development library very much but it isn’t suitable to learn pure SDL 2.0. Many functions are wrapped by new function names, you would learn much about the usage of Bare Game, fewer about SDL 2.0 itself. Also, the ease of use is traded for flexibility, e.g. there is just support for Windows and Linux, no Mac support, and you are more or less forced to use Lazarus IDE (which is an excellent choice, no question!) but for some reason you might not want to use Lazarus. The usage of libraries always trades ease for flexibility. And finally you are dependent upon a second project. If SDL 2.0 is updated, will Bare Game have updates, too? Bare Game is a great project at all, but for learning SDL 2.0 and if you keep the downsides in mind, it is not the best choice here.
Imant’s Gulis units allow for dynamic loading of SDL 2.0, hence your application decides during run-time if SDL 2.0 has to be loaded. This led to heavily modified unit files compared to the original header files. Also it is expected to use Lazarus. Although there are numerous cases where dynamic loading can be a great plus, for the tutorial and a wide variety of applications this is not necessary.
Pure header translations
In contrast to the packages discussed above, Tim Blume’s SDL 2.0 units are a pure translation of the original C header files. This allows for a better understanding in how SDL 2.0 works. Also it allows for better flexibility with regards to later projects.
This said, to my mind, the best choice to start with SDL 2.0 and Free Pascal: Go for Tim Blume’s SDL 2.0 units. For other purposes, other units may be the better choice.