Re: TreeIters again

[muppet <scott asofyet org>]

On Feb 21, 2008, at 9:23 AM, Dave Howorth wrote:

> The problem is that $selected_row_iter is never equal to $iter.  
> $iter is
> a new TreeIter for every sibling.

Yes.  That's because the objects are intended to be allocated on the  
stack.  See below.


> <rant>TreeIters seem like a very badly thought out feature!</rant>

GtkTreeIter is designed to be very fast in C code, using stack  
allocation and short object lifetimes.  This makes binding GtkTreeIter  
to a dynamic language like perl rather, ahem, challenging, and  
Gtk2::TreeIter is not very natural in perl.  Sorry.  Gtk2::ListStore  
is natural for wrapping up in tie() magic to masquerade as an array,  
but Gtk2::TreeStore is not so simple.  Therefore, there is no  
canonical perlish iteration interface.  (But  
Gtk2::Ex::Simple::TiedList is quite handy for Gtk2::ListStores.)

So, not a badly thought-out feature in and of themselves, but not very  
fun for language bindings.


> I know I could use iter_nth_child() to iterate using an index, but I
> haven't found a way to discover the index of the selected child.
> Something like:
>
>    my $selected_index =
>            $tree_store->???child_index???($parent, $selected_iter);

You can get a path from an iter, and you can convert a path to  
indices.  You can build a path from indices.  From the docs:

>        A path is essentially a potential node.  It is a location on  
> a model
>        that may or may not actually correspond to a node on a  
> specific model.
>        The Gtk2::TreePath object can be converted into either an  
> array of
>        unsigned integers or a string.  The string form is a list of  
> numbers
>        separated by a colon.  Each number refers to the offset at  
> that level.
>        Thus, the path '0' refers to the root node and the path '2:4'  
> refers
>        to the fifth child of the third node.



So,

    my $selected_index =
        ($tree_store->get_path ($selected_iter)->get_indices)[-1];



--
It's all very complicated and would take a scientist to explain it.
  -- MST3K