SDLmixer: provide Mix_ChannelFinished working example

[marcusva]

Originally reported by: JP LeBreton (Bitbucket: JPLeBreton, GitHub: JPLeBreton)

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I'd like to create a callback when a sound finishes playing, and it doesn't appear to work like anything else I've encountered using pysdl2 so far.

http://www.libsdl.org/projects/SDL_mixer/docs/SDL_mixer.html#SEC37

When I call Mix_ChannelFinished(my_func) where my_func is a standard Python function, I get this error:

#!python


ctypes.ArgumentError: argument 1: <class 'TypeError'>: expected CFunctionType instance instead of method

My attempt to give it a CFunctionType instance looks like this:

#!python

MYFUNCTYPE = ctypes.CFUNCTYPE(ctypes.c_void_p, ctypes.POINTER(ctypes.c_int))
my_c_func = MYFUNCTYPE(my_python_func)
sdlmixer.Mix_ChannelFinished(my_c_func)

but this gives the error:

#!python

ctypes.ArgumentError: argument 1: <class 'TypeError'>: expected CFunctionType instance instead of CFunctionType

I'm sure I'm doing something very simple wrong here, but it's non-obvious enough that it would be nice to have an example of how to do this properly in pysdl2's excellent docs!

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• Bitbucket: https://bitbucket.org/marcusva/py-sdl2/issue/86

[marcusva]

Original comment by JP LeBreton (Bitbucket: JPLeBreton, GitHub: JPLeBreton):

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Attached: script creating a Mix_HookMusicFinished callback for music, and a Mix_ChannelFinished for a sound effect (sample/chunk). The music callback works as expected, but the sound callback segfaults running Mix_ChannelFinished - see the comment.

[marcusva]

Original comment by Marcus von Appen (Bitbucket: marcusva, GitHub: marcusva):

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Your Mix_ChannelFinished signature is wrong. It does not return a value and requires a c_int as argument

#!python

MYFUNCTYPE = ctypes.CFUNCTYPE(None, ctypes.c_int)
my_c_func = MYFUNCTYPE(my_python_func)
sdlmixer.Mix_ChannelFinished(my_c_func)

should do the trick.

[marcusva]

Original comment by JP LeBreton (Bitbucket: JPLeBreton, GitHub: JPLeBreton):

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Excellent, thank you! Would you like me to clean up my above code and submit it as an example?