libgnomecanvas and Accessibility

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

I ran the libgnomecanvas demo program canvas-demo and had a look at the 
accessibility information which is reported. I have a number of observations on 
which I request comment.

1) No states are reported as being set for any canvas item by the function
atk_object_ref_state_set(). I assume that the state "visible" ought to be set if 
an item is not hidden and that the state "showing" ought to be set for items 
which are on the screen. Other states which are set for most widgets are  
"enabled" and "sensitive". I assume that these ought to be set for a canvas 
item.  I assume that canvas items which are not canvas groups should be 
"focusable" and be "focused" when they are the focus item on the canvas.

2) We create specific accessible objects for a subset of canvas items, canvas 
group, canvas text, canvas rich text, canvas widget.

This has the effect that an AtkNoopObject is created for other types of canvas 
items. I think we should create an accessible object for other canvas items 
instead of defaulting to AtkNoopObject.

3) When the canvas receives focus we should report the focus as being on the 
focused item, assuming that it is accessible.

4) There is a z-order for canvas items in a canvas group. This suggests that the 
AtkLayer for canvas items should be ATK_LAYER_MDI and that a canvas item should 
implement atk_object_get_mdi_zorder which identifies where the item is in its 
parent's group z-order.

5) The functions gnome_canvas_item_show() and gnome_item_canvas_hide() allow an 
item on a canvas to be made visible or invisible. I do not think that we can get 
a notification when this happens.

Padraig