Re: [Vala] Properly wrapping callbacks

[Jürg Billeter <j bitron ch>]

On Mon, 2009-01-26 at 11:32 +0100, Frederik wrote:
> Frederik wrote:
> > Michael 'Mickey' Lauer wrote:
> > > Hi,
> > >
> > > I'm working on my first binding for a non-gobject library -- please see 
> > > gsm0710_p.h.
> > >
> > > My current vapi is also attached. I'm struggling with setting the callback 
> > > pointers now. How should the callbacks in my .vala object be defined so that 
> > > I can set them via e.g. 
> > >
> > > <callback>
> > >
> > > var ctx = new Context();
> > > ctx.at_command = <callback>
> > >
> > > Cheers,
> > >
> > > Mickey.
> >
> > You should make your delegate non-static, since an instance gets passed.
> > In your case the instance gets passed as first parameter and not as last
> > parameter, so you must add [CCode [instance_pos = 0)]. And 'char*'
> > translates to 'string' in Vala.
> >
> >   [CCode [instance_pos = 0)]
> >   public delegate int at_command_t (string command);
>
> However, if it is meant as source object for some kind of event and not
> as instance you should mark it as static and pass the context explicitly:
>
>   public static delegate int at_command_t (Context ctx, string command);

Yes, this is better as, in this library, the first callback parameter
does not represent the instance of the user-defined handler (usually
called user_data), it's always a pointer to the context.

Jürg