Re: extension of Glade DTD to support accessibility

[James Henstridge <james daa com au>]

On Wed, 9 May 2001, Bill Haneman wrote:

> Hi folks:
>
> For awhile now one of the ideas in the background of Gnome accessibility
> has been how Glade can help us enhance accessibility for applications.
> Now that we have defined a set of accessibility interfaces and
> properties, it seems appropriate to consider how to support those
> properties in Glade/libglade.

Sounds interesting.  Recently I started looking at porting/rewriting
libglade for gtk 2.0, so I will try to keep ATK in mind when doing so.

>
> As has been pointed out before, in many cases applications may need to
> provide accessibility hints in addition to or instead of those provided
> "automatically" by the ATK implementation for stock GTK widgets.  For
> example, an unlabelled button may wish to set an accessibility "name"
> without actually containing a label:
>
>   AtkObject atkObject = gtk_widget_get_accessible (aButton);
>
>   atk_object_set_name (atkObject, "Quit");

or alternatively,
    g_object_set (atkObject, "name", "Quit", NULL);

(using the properties support for GObjects).  Does ATK expose all the
properties you might want to manipulate through the properties interfaces?
One of the goals for the change is to move as over to using properties
where possible.

>
> I believe that a libglade application can do this by querying libglade
> for a pointer to the appropriate widget, via the widget's unique
> identifier.  However it would be nicer if some ATK properties (at least)
> were settable via attributes in the Glade XML.

Well, I have been proposing that we rewrite the glade XML format for gnome
2.0, so adding support for AtkObject properties sounds like a good idea.

>
> This presumably suggests three steps:
>
> extension of Glade's XML DTD to include these (optional) attributes;
> extension of libglade to parse these attributes and call the appropriate
> atk methods (as above);
> (eventually) extension of Glade to expose these attributes when a
> developer is setting widget properties in the Glade UI builder.

Maybe adding a section like this to the XML:
  <widget id="name" class="GtkButton">
    ...
    <accessibility>
      <property name="name">Quit</property>
    </accessibility>
    ...
  </widget>

>
> I believe that the ATK attributes of most interest are those ordinarily
> set by the following ATK methods:
>
> atk_image_set_image_description (AtkImage *image, gchar *desc);
> atk_object_set_name (AtkObject *accessible, gchar * name);
> atk_object_set_description (AtkObject *accessible, gchar *desc);
> atk_object_set_parent (AtkObject *accessible, AtkObject *parent);
> atk_object_set_role (AtkObject *accessible, AtkRole role);
>  (ROLES are readily specified via a string)
> atk_table_set_caption  (AtkTable *table, gchar *caption);
> atk_table_set_column_description (AtkTable *table, gchar *desc);
> atk_table_set_row_description  (AtkTable *table, gchar *desc);
>
> also (very important!) need to have multiple attributes of type
> "atk_relation" settable on a widget.  The atk_relation consists of a
> relation type flag (such as LABEL_FOR) and a reference to some other
> widget (implementable using an "id" attribute if glade XML supports such
> attributes on the XML elements). AtkObject's set_parent method likewise
> takes a reference to an "AtkObject" object.  The other methods are
> readily implemented using character strings as attribute values.
>
> Comments, suggestions (and volunteers :-) welcome...

Sounds like a good idea.  I will need to read up on ATK a bit now (also
for the python bindings).

James.

-- 
Email: james daa com au
WWW:   http://www.daa.com.au/~james/