rubysdl vs. ruby-sdl-ffi

Question

Could anyone here tell me the difference between the Ruby gems rubysdl and ruby-sdl-ffi, like speed variances? If so, which would you prefer? I'm wondering for the sake of my gem that I'm writing, Rubydraw (located here).

Thanks in advance!

Answer 1

I am the author of ruby-sdl-ffi. This question was brought to my attention today, so I am answering for the benefit of anyone who is still curious.

The main difference is that ruby-sdl-ffi is pure Ruby code that accesses SDL (and related libraries) via FFI (foreign function interface), whereas rubysdl is an extension written in C that links to SDL (and related libraries). There are pros and cons to each approach. (Obviously, I feel that FFI is the better approach, or I would not have bothered to write ruby-sdl-ffi.)

Both libraries offer similar feature sets, although there are some differences (noted below). They can both do 2D games with images, sounds/music, and user input from keyboard, mouse, and/or joystick/gamepad. They can also both be used with OpenGL (via ruby-opengl or ffi-opengl) to create hardware-accelerated 3D games. They can both be used on Windows, MacOS X, and Linux (and perhaps other platforms), although rubysdl only works on MacOS X if you use a special Ruby interpreter wrapper called "rsdl".

I have not run any serious benchmarks, so I can't provide any definitive data about raw performance. My general impression is that rubysdl might have a slight performance advantage, but they are close enough that performance isn't the main factor when deciding between the two libraries.

Here is how I would summarize the pros and cons of the two libraries:

ruby-sdl-ffi

• Easier for users to install the gem. It does not need to be compiled, so users don't need to install a C compiler or toolchain.
• Works with MRI (the "usual" Ruby interpreter), JRuby, and probably Rubinius.
• No special interpreter is required on MacOS X. However, the MacOS X support may need to be updated to get it working totally right on the latest versions of MacOS X. (Apple keeps changing things.)
• Lower-level API, more closely mirrors the C libraries. This may be good or bad depending on your perspective.
• Currently has bindings for SDL, SDL_gfx, SDL_image, SDL_mixer, and SDL_ttf libraries. (Compared to rubysdl, it adds SDL_gfx but lacks SGE and SMPEG.) Adding bindings for other libraries is quite easy.
• Not actively developed or maintained anymore. I don't have the time or interest anymore, but someone is welcome to take over, and I can provide guidance.
• Somewhat experimental, and has some rough edges.

rubysdl

• More mature and polished, has withstood the test of time.
• Better support for Japanese text input and rendering.
• Higher-level, more abstract API.
• Binds SDL, SGE, SMPEG, SDL_image, SDL_mixer, and SDL_ttf libraries.
• Requires users to have a C compiler to install the gem. This can be quite a headache on Windows and MacOS X.
• Requires MacOS X users to run your game using the special "rsdl" Ruby interpreter. Thus, to my knowledge, it will not work with JRuby or Rubinius on MacOS X.
• Does not seem to be actively developed or maintained anymore either.