Re: [Help-smalltalk] Re: C Callbacks

[Paolo Bonzini]

.
> callback := ExternalCallback
>       block: [ :lplf :lptm :dwType :lpData | operation value: lplf 
> value: lptm value: dwType ]
>       argumentTypes: 'LOGFONT* lpvoid dword dword'

I see -- the most similar thing to this one is provided by msgSendf. 
You would have to rewrite msgSendf as a function that follows the libffi 
closure API, and then pass it to the ffi_prep_closure together with an 
ffi_cif (there is already code to construct ffi_cif from a 
CFunctionDescriptor).  See for example 
http://developer.apple.com/documentation/Darwin/Reference/ManPages/man3/ffi_prep_closure.3.html 
(the main difference is that, in the example, foo_closure does not look 
at its CIF argument).

> Due to the fact that I need to create callbacks dynamically based on 
> third party data I get (dynamically as well :-( ) I think there is no 
> way around libffi. Maybe I can reuse the existing parameter stuff around 
> #cCall: for inbound calls.

Yes, most of it is written for libffi so it can be recycled for this 
setting too.  It's in cint.c.

Paolo