RE: Moving tree items

["Lachac, Gerry" <G Lachac dialogic com>]

Owen Taylor [mailto:otaylor@gtk.org] writes: 
> "Lachac, Gerry" <G.Lachac@dialogic.com> writes:

>> Can a similar change also be made for a GtkList as well?  I 
>> recently had to
>> implement moving things up and down a list by  allocating a 
>> new GtkListItem,
>> copying the old one and remove it from the list, inserting 
>> the new one

> 
> For a GtkList no recreation, copying is needed:
> 
>  GList *items_to_move = g_list_append (NULL, item_to_remove);
>  
>  gtk_widget_ref (item_to_remove);
>  gtk_list_remove_items (GtkList (list), items_to_move);
>  gtk_list_insert_items (GtkList (list), items_to_move, new_position);
>  gtk_widget_unref (item_to_remove);
> 
> To explain the code:
> 
>  - creates a GList with a single item.
> 
>  - increments the reference count on the item, so that
>    when it is removed from its parent, it is not freed. (Even though
>    it is an orphan, somebody cares about it...)
> 
>  - removes the item from the list
>  
>  - inserts it in the new position
> 
>  - unreferences it, since the List now references it again.
> 

Have you done this before? I swear I tried this technique (it's the first
thing I thought of).  When I tried to insert() the removed item I got
runtime errors from gtk (1.0.1).  I discovered that the list->next field was
not NULL after the remove() so re-inserting wreaked all kinds of havoc. I
may have been doing something else wrong, so I'll double check.  Thanks for
the tip.

-ger