The pysdl2-cffi package is a wrapper for libSDL2 (http://www.libsdl.org/) and its related libraries SDL_image, SDL_mixer, and SDL_ttf, built using cffi. This package wraps each function in automatically generated helper functions by following some simple rules, exposing them under the sdl namespace without the SDL_ etc. prefixes.
Functions and constants are exposed under the sdl, sdl.image, sdl.mixer, and sdl.ttf namespaces.
Functions are renamed by removing the SDL_ prefix and lower casing the first letter of the function. SDL_CreateWindow becomes sdl.createWindow, IMG_LoadTexture becomes sdl.image.loadTexture.
Constants (or anything that has two capital letters after the prefix) are renamed by removing the prefix only. SDL_INIT_VIDEO becomes sdl.INIT_VIDEO, MIX_INIT_MP3 becomes sdl.mixer.INIT_MP3.
(The original names are available in the lib submodule of each of the _sdl, _sdl_image, _sdl_mixer, _sdl_ttf modules)
Functions with primitive-typed out parameters return a tuple of the return value (if any) and the value of each out parameter.
C:uint32_t SDL_GetMouseState(int *, int *);
pysdl2-cffi:buttons, x, y = sdl.getMouseState() # It is also possible to pass the correct C type to the function: x_pointer = sdl.ffi.new('int *') y_pointer = sdl.ffi.new('int *') buttons, x, y = sdl.getMouseState(x_pointer, y_pointer) x == x and y == y
Structs are exposed as classes that can automatically allocate non-opaque structures. For example, SDL_Rect can be allocated by pysdl2-cffi, but SDL_Window can only be allocated by calling sdl.createWindow(). Structs are exposed without their prefix in the same way as other declarations:
rect = sdl.Rect() rect.x = 4 rect.y = 3 rect.w = 42 rect.h = 64
Structs can accept any valid ffi initializer as their arguments. This also works when a function would otherwise require a struct:
rect = sdl.Rect((4, 3, 42, 64)) rect2 = sdl.Rect(dict(x=4, y=3, w=42, h=64)) intersection = sdl.Rect() # we need to be able to see the result intersects = sdl.intersectRect((4,3,42,64), (40,60,10,10), intersection)
Any function that takes a particular struct as its first argument is also a method on the relevant helper class:
intersects = rect.intersectRect((40,60,10,10), intersection)
The binding does not try to hook resource management to garbage collection. Users should release textures, windows, and so on using the appropriate SDL functions or risk leaking resources.
Most functions in the sdl, sdl.image, and sdl.ttf libraries check their return value for errors. If there was an error then an exception sdl.SDLError() is thrown. The exception’s .message property holds SDL’s own error message as reported by sdl.getError():
>>> sdl.image.load('/tmp/i_dont_exist.png') SDLError: Couldn't open /tmp/i_dont_exist.png
The sdl.mixer library does not currently convert errors to exceptions.