Re: python / tinymail.Account.set_pass_func

[Mark Doffman <mark doffman codethink co uk>]

Hi Shikhar,

Philip Van Hoof wrote:
> I'll let Mark Doffman answer this, he's working on the Python bindings
>
> On Sun, 2008-07-13 at 03:09 +0530, Shikhar wrote:
> > Shikhar wrote:
> > > Shikhar wrote:
> > > > I would appreciate some guidance about how to make use of 
> > > > tinymail.Account.set_pass_func()
> > > >
> > > > What would the (Python) signature of the function be?

The set_pass_func method should take one argument, a python function 
that gets a password for the account.

> > > >
> > > Ah, looking at the tmut source code helped me figure out PasswordGetter
> > Not actually, it turns out. I have spent a lot of time figuring this out 
> > so it would be great if someone could help me out. I don't have 
> > experience with GObject so that could be tripping me, or maybe it has 
> > something to do with the bindings
> >
> >  >>> from tinymail.camel import *
> >  >>> from tinymail.uigtk import GtkPasswordDialog
> >  >>>
> >  >>> def get_pass(aid, prompt):
> > ...     pwdgetter = GtkPasswordDialog()
> > ...     return pwdgetter.get_password(aid, prompt)
> > ...
> >  >>> acc = CamelTransportAccount()
> >  >>> acc.set_id('tny_test')
> >  >>> acc.set_pass_func(get_pass)
> > __main__:1: Warning: invalid cast from `TnyCamelTransportAccount' to 
> > `TnyList'
> > Segmentation fault

The code for this function is implemented in 
bindings/python/tinymail.override line 351. Unfortunately the 
implementation is both wrong and useless. The 'C' interface for the 
account store is:

void (*set_pass_func) (TnyAccount *self, TnyGetPassFunc get_pass_func);

This is very difficult to bind because there is no user data associated 
with the callback. The function the python bindings needs to pass in the 
get_pass_func argument is a marshaller function. The purpose of this 
function is to marshal data arguments in and out of the implementing 
python function, and to actually invoke it.

This means that the actual python function must be stored as a data 
argument, which is missing in this interface.

Ideally all callback functions in the tinymail interface would use 
GClosures, as this would be trivial to bind to. Failing that providing 
user data associated with each callback would make binding by hand 
possible.

Currently it will be difficult, but possible, to provide a python 
wrapper for this function. The solution would involve using 
g_object_set_data to store a pointer to the user data on the account 
object. Messy, but possible.

Much of the interface involving callbacks has not been wrapped by the 
python bindings. This is the first thing that needs to be done to have 
fully functioning python bindings. Many of the callback interfaces have 
user data associated, not sure how many of these difficult cases there are.

> > (Same error even if the account has a Camel 
> > session/username/password/hostname/port/name etc. attributes set)
> > _______________________________________________
> > tinymail-devel-list mailing list
> > tinymail-devel-list gnome org
> > http://mail.gnome.org/mailman/listinfo/tinymail-devel-list

I don't have the time right now to make a concerted push on wrapping the 
callback functions. I can however provide help if you wish to do so.

The g_object_set_data idea for wrapping this particular function comes 
from Rob Taylor. So maybe I can test it out and get back to you.

Thanks

Mark

--
Mark Doffman, Codethink Ltd. -  http://codethink.co.uk