Re: [Vala] GBinding support?

[Frederik <scumm_fredo gmx net>]

Am 21.06.2010 09:29, Fredderic Unpenstein wrote:
> On 21 June 2010 01:57, Frederik <scumm_fredo gmx net> wrote:
> > GLib/GObject 2.26 will add property binding [1]. The straightforward way to
> > support this in Vala would be:
> >  Object.bind_property (foo, "x", bar, "y");
> >  Object.bind_property (foo, "x", bar, "y", BindingFlags.BIDIRECTIONAL);
>
> Would foo.x.bind_property be a possibility?  And perhaps
> bind_bidirectional or bind_with (do you bind anything else, other than
> properties, on an object property?)...  Maybe then also bind_property
> could become bind_to or something equaly less redundant?

A problem is that 'foo.x' will evaluate to the value of the property,
not representing the property itself. So, if you write

  foo.x.bind_property (bar.y);

and if 'foo.x' is 4 and 'bar.y' is 5 it would essentially mean

  4.bind_property (5);

> Personaly, I like the operators, but they're a little limited once you
> add extra varients or options, as with the connect family.  Unless
> some syntax is added for general operator functions...  eg:
>
>    foo.x +> [BIDIRECTIONAL] bar.y;
>
> which could also make += signal connection useful again.  Perhaps
> adding support for a bracketed comma-separated list with the extra
> arguments, instead.

Personally, I prefer descriptive names over symbolic operators. The question
is whether the property binding feature is essential enough to justify extra
syntax (keyword, operator) just to be type safe.

> > And how to deal with 'g_object_bind_property_full'? It takes two TransformFuncs
> > but only one user_data/GDestroyNotify pair.
> >  (foo.x, celsius_to_fahrenheit) <+> (bar.y, fahrenheit_to_celsius);
> >  (foo.x, (b, s, t) => { }) <+> (bar.y, (b, s, t) => { });
>
> That's sort of what I was saying with bracketing above, too.  A
> general syntax pattern like that might help with other places where
> syntactic support would be useful but presently shunned.
>
>
> Fredderic

Best regards,

Frederik