Re: Getting at tree information in ATK

["Padraig O'Briain" <Padraig Obriain Sun COM>]

> 
> To support trees in ATK, I was thinking of defining the relations
> ATK_RELATION_TREE_NODE_CHILDREN and ATK_TREE_NODE_PARENT. 
> 
> These would allow us to specify for each accessible which is in a tree, i.e. 
> GtkTreeStore, the children of a node and the parent node of a node.
> 
> These would be used instead of parent/child to navigate a tree.
> 
> One problem with this approach is that we would have to create accessible 
> objects for each child cell when the user wished to investigate how many child 
> nodes a node has.
> 
> The alternative is to try and use the parent/child relationship to navigate 
the 
> tree.
> 
> To achieve this I think we need the following:
> 
> 1) We need to deal with columns in a GtkTreeView which have more than one 
> renderer. We will assume that there are not two renderers of the same type.
> Consider the case where the column contains a pixbuf and text. Instead of 
> exposing the cells objects corresponding to the pixbuf and the text as 
children 
> of the containercell the containercell will implement all the interfaces that 
> its children may implement and call through to the first child which 
implements 
> the interface.
> 

Rather than make the assumption that all the accessible information can be 
exposed without getting at cell objects in the containercell I propose to define 
two new relations ATK_RELATION_NODE_CHILDERN and ATK_RELATION_NODE_PARENT 
to allow access to the cell objects.

 * ATK_RELATION_NODE_CHILDREN: Indicates an object is a node in a tree or table 
and a compound object which more than one subobject
 * ATK_RELATION_NODE_PARENT: Indicates an object is a subobject of a compound ob
ject which is a node in a tree or table.

> 2) We do not assume that all the cells in a table are children of the table. 
For 
> a GtkTreeStore only the top level cells will be children of the table. For a 
> GtkListStore all the cells will be children of the table.
> 
> 3) The function atk_table_get_index_at() may return an invalid index, i.e. -1, 
> for cells which are not children of the table. This implies that the cell at 
the 
> specified (row, column) is a child of an expandable cell.
> 
> Padraig
> 
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