[Q] ctypes callbacks with Delphi

[achrist at easystreet.com]

Andrew MacIntyre wrote:
> 
> On Fri, 17 Oct 2003 achrist at easystreet.com wrote:
> 
> > I'm aving some trouble getting callbacks from a Delphi DLL back to
> > python working through ctypes.
> 
> I suggest that this question will be more visible on the ctypes mailing
> list.  I vaguely recall a question along these lines some time ago, so
> viewing the list archives might be useful.
> 

I've been over those ASPN list archives as best I can, and I don't
see anything that solves this problem.  However, trying to
search the lists is a little tricky.  I did a search on 'callback'
and it shows me results 1-20, which don't show me anything that
I think will help, and clicking on '21-40' gives me advertising and
no more messages. IDK.

When I search for 'Delphi', nothing comes up.  This can't be a Delphi
problem, can it? Delphi can't be that broken, can it?

When I search for the terms in the error message that I get, 'Access 
Violation' and 'write address', I don't see a solution obviously
anywhere.  The ASPN pages load very slowly on my machine over dial-up,
so it's no fun hunting around for something that you don't know is
there.

I see that I have to subscribe to the list to post a message.  So, I
try to subscribe and go to the ASPN page to subscribe, and they list
about 40 groups, but no ctypes-users.   Looks like subscriptions
to this one are not currently available to such as me.

The ctypes tutorial makes this look very easy, and I think that I'm
doing what it shows, and it almost works, but not 100%.  IDK.

The unit tests that come with ctypes have a test for callbacks from
a DLL, so I try to look at that to see what goes on in the DLL to 
see if I can write my DLL the same way.  But they don't include source
for the DLL.  They don't even call a real DLL.  They test ctypes with
a synthetic DLL of some kind created by a ctypes CDLL macro.  So the
unit test only shows that ctypes can talk to itself, not maybe a real
DLL.  IDK.

If anyone is using ctypes with called-back functions written in python
returning (simple integer) values back to a DLL written in C or Delphi,
such DLL called from python through ctypes,  I'd sure like to see
what the python and C or Delphi code that work together look like --
how the identity of the called-back function is passed to the DLL and
how the called-back function sends back its return value.  I'm
trying to follow the tutorial, which looks very easy, but I've not got
it right.

TIA and thanks for your help,


Al