Re: [Vala] GBinding support?

[Fredderic Unpenstein <magentus gmail com>]

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?

Also, is there any way to get rid of the need for BindingFlags in
that?  If the argument IS a BindingFlags, Vala could include that
scope when looking up bare words...?


> However, this is not very type-safe. Would direct language support be
> reasonable? E.g. something like
>
>  foo.x +> bar.y;       // default
>  foo.x <+> bar.y;      // bidirectional
>
> Or is it too cryptic?

There's also := type notation, which fels like "more than assignment".
 Though since binding takes flags, I worry that it'll end up going the
same way as += for signal connection.

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.


> 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