Re: Force containers to be list-like

["BJörn Lindqvist" <bjourne gmail com>]

And the patch is here:

http://bugzilla.gnome.org/show_bug.cgi?id=562244

2008/10/7 BJörn Lindqvist <bjourne gmail com>:
> Hello good people,
>
> I think there should be a contract that all subclasses of GtkContainer
> must implement. Conceptually, a container is a collection of
> widgets. Usually that collection is implemented as a list but it does
> not have to be [1]. This means that:
>
> 1. The order child widgets are stored in may not be the same as the
>   order they were added in. This code might not work:
>
>    w1 = gtk.Button()
>    w2 = gtk.Button()
>    container = RandomContainer()
>    container.add(w1)
>    container.add(w2)
>    assert container.get_children() == [w1, w2]
>
> 2. Since the order is not guaranteed it may change for any
>   reason. This code might not work:
>
>   w1 = gtk.Button()
>   w2 = gtk.Button()
>   container = RandomContainer()
>   c1 = container.get_children()
>   c2 = container.get_children()
>   assert c1 == c2
>
> Because those two invariants cannot be guaranteed, it becomes harder
> than it has to be to make z-order work properly, see #550345.
>
> The solution I propose is to require all container implementations to
> behave list-like so that the above code always works by specifying in
> the docs the contract that they need to full fill. I don't think that
> should break any code whatsoever even if it in theory is an ABI
> break. The big gain is that widgets gets an implied z-order which
> makes overlapping widgets work.
>
> In the future (3.0 maybe?) it would be cool if there was a Sequence
> interface that container widgets could implement. That way it would be
> more explicit how containers should be implemented. And other
> list-like widgets could also implement that interface (GtkListStore,
> GtkCellView and GtkMenuShell for example). But for now the contract
> would suffice.
>
> [1] - It could be a set for example.
>
>
> --
> mvh Björn
>



-- 
mvh Björn