[Help-smalltalk] Re: C Callbacks

[Udo Schneider]

Paolo,

> No, but callbacks are available without using libffi.  You use functions 
> in the vm_proxy, see the GLUT bindings in the opengl branch of my 
> repository for a simple example.
Nice examples! However as far as I see the callbacks are "static". The 
callback functions are in C and in turn call Smalltalk methods via 
vmproxy. What I was thinking of is defining a callback by providing a 
method/block with appropriate arg and return types in Smalltalk 
dynamically (something similar to ExternalCallbacks in Dolphin Smalltalk
http://www.object-arts.com/docs/externalcallbackobjects.htm)

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

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.

Thanks,

Udo