[Pyrex] using c-methods for callbacks?

[Lenard Lindstrom]

horace wrote:
> hi,
>
> it would be great if i could use c-methods for callbacks but i always 
> get a crash if i access self. am i doing something wrong or doesn't 
> self get assigned correctly if the method gets called from a c-library?
>
> cdef class Engine:
>   ...
>   cdef void on_space(self): # i pass this to the c-library to be used 
> as the callback
>     print "test!" # this works
>     print self # this crashes
> ------------------------------------------------------------------------
>
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>   
ctypes creates C closures through libffi. That binds the self argument 
with a value. Cython won't do that. It requires assembly code, so is not 
portable. You either have to get your function's arguments through 
global variables or hope the callback mechanism includes an argument 
passing mechanism. If that later, I don't know exactly how to convert a 
Python object to a void pointer and back in Cython. If the callbacks are 
passed a keyboard key argument by the caller then that could be used as 
a key into a dictionary of Python functions.

Lenard Lindstrom
<len-l at telus.net>

PS. Could you disable automated out-of-office replies for postings to 
this mailing list? The replies don't go to the list, but rather to the 
person making the post.
L.