Re: [g-a-devel]Gnome 2.0 : accessibility for the gnome-cd application

["Padraig O'Briain" <Padraig Obriain sun com>]

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> To: JAYARAJ P R <jayaraj rajappan wipro com>
> CC: padraig obriain sun com, gnome-accessibility-devel gnome org
> Subject: Re: [g-a-devel]Gnome 2.0 : accessibility for the gnome-cd application
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> 
> JAYARAJ P R wrote:
> > 
> > Hi Bill,
> > 
> > Marc has suggested the following approach for the gnome-cd application
> > 
> > 1. Inherit AtkComponent for the custom widget from the parent (GailWidget).
> > 2. Implement functions like atk_object_ref_accessible_child() for the custom
> >    widget.
> > 3. Implement AtkText for the children (PangoLayouts).
> > 
> > Does this approach seem fine with you?
> 
> Yes, especially if Marc thinks it's the right approach :-)
> 
> > Your earlier mail mentioned that we don't necessarily need a factory for the
> > pango layout. In that case, what is the other approach?
> 
> Well, you could implement your own internal methods that the 
> ref_accessible_child_at_index implementation calls.
> 
> See my original post about how to use our own PangoLayout code
> from gail; and please coordinate that with Padraig, I believe
> there is code in gail (gail-util.h) that allows you to get
> an AtkObject appropriate to a PangoLayout.
> 
> >...In gail we
> > do this through the GtkAccessible structure which has a pointer to the
> > Widget (GtkWidget *). But how we do this in case of a PangoLayout if we
> > go for a factory approach?
> 
> If you create your own subtype of AtkObject (which you must, if you are
> adding or modifying implementation code) then you can add your own
> private
> dats, which could include a pointer to the PangoLayout.  I believe that
> our existing PangoLayout support code creates AtkObjects which do
> this already; Padraig?

What we have in gail/util, in gailmisc.[ch] are support functions, which are 
used in GailEntry, GailLabel and GailTextCell, which manipulate a PangoLayout or 
the PangoRectangle obtained from a PangoLayout.

Our hope is that these functions can be used in the implementation of ATK 
interfaces for custom widgets.

Padraig


>
> -best regards
> 
> -Bill
> 
> > Please let me know your comments.
> > 
> > Thanks,
> > Jayaraj.
> > 
> > -----Original Message-----
> > From: gnome-accessibility-devel-admin gnome org
> > [mailto:gnome-accessibility-devel-admin gnome org]On Behalf Of Bill
> > Haneman
> > Sent: Tuesday, February 05, 2002 8:32 PM
> > To: bill haneman Sun COM; jayaraj rajappan wipro com
> > Cc: mukund rajagopalan wipro com; gnome-accessibility-devel gnome org
> > Subject: RE: [g-a-devel]Gnome 2.0 : accessibility for the gnome-cd
> > application
> > 
> > jayaraj wrote:
> > 
> > >As i understand from the discussions till now, there are 2 approaches which
> > >we could follow to provide accessibility for the CDDisplay custom widget in
> > >gnome-cd.
> > >
> > >1.The first approach is to try to expose  separate AtkObjects for each
> > >PangoLayout. Does it mean that we have to implement AtkComponent for the
> > >container of the PangoLayout (which is the custom widget in this case)? Or
> > >can we override the atk_component_ref_accessible_at_point() method for the
> > >custom wiget, so that it returns different AtkObjects for each of the
> > >PangoLayouts depending on the x and y values. Also, i guess we need to
> > >implement a separate factory for the PangoLayout so that we can set the
> > >accessible name and description for each of the PangoLayouts and the code
> > >for this would reside in the application itself.
> > >
> > >2. The second approach is to try to implement most of the AtkText
> > interfaces
> > >for the custom widget.
> > >
> > >Which one do you think would be more appropriate in this particular case?
> > >
> > >Regards,
> > >Jayaraj
> > 
> > I think that the first option is a bit better; however we still need to
> > implement AtkText
> > for the children of the custom widget.  Fortunately we have utilities/helper
> > classes for
> > doing this with PangoLayouts already, in gail.
> > 
> > You don't necessarily need a factory for the pango layout, though installing
> > an
> > accessibility factory for all instances of the PangoLayout type might be a
> > useful thing
> > to do.  We might do the latter in gail, in which case all you would need to
> > do is call
> > 
> > factory = atk_registry_get_factory (atkregistry, PANGO_TYPE_LAYOUT);
> > atkobject = atk_factory_create_accessible (factory, pangolayoutinstance);
> > 
> > from within the custom code for parts of the custom widget's AtkObject
> > implementation, to
> > create the appropriate AtkObject children, which could be cached and
> > returned by calls to
> > atk_component_ref_accessible_at_point() and atk_object_ref_child().
> > 
> > -Bill