Re: inaccessible treeviews and tables

[Peter Vágner <pvdeejay gmail com>]

Hello,
I have subclassed GTKRendererCellAccessible, implemented basic get_name 
method in my subclass taking advantage of reference to the CellRenderer.
However what I am unable to workout is how do I get a proper GType of my 
subclass so I can pass it to the 
gtk_cell_renderer_class_set_accessible_type () on my CellRenderer 
subclass. I assumed I am missing something verry obvious but I then went 
back to the earlier discussion you pointed me to a while ago... 
https://mail.gnome.org/archives/gtk-devel-list/2012-August/msg00050.html 
. I can find no method get_type or similar on GTKRenderCellAccessible 
either directly implemented nor inherited. So either I am missing 
something simple or this is more complicated than I might imagine.
Also the help text for gtk_cell_renderer_class_set_accessible_type () 
states it's advised to call this from the init method on the 
CellRenderer. I am afraid this is really basic and I might be able to 
research it else where but what is an init method in this case? Is that 
a constructor or a method called init? I haven't see no method like this 
while looking at the GTK docs.

I apologize for taking your time but I am really interested in being 
able to do this.

Greetings

Peter

On 07.07.2014 16:47, Piñeiro wrote:
> Good catch, I didn't realize that ContactListCellRenderer. Sorry, I'm
> not used to search through Vala source code.
>
> Looking at that code, there is a variable called "entry", that in most
> cases is the contact. On render_name it uses that variable to get the
> name. On render_userstatus it uses that variable to render the status. A
> ContactListCellRendererAccessible would need to use this "entry"
> variable to expose the name and status on a custom implementation of
> AtkObject.get_name and AtkObject.ref_state_set.
>
> Looking for
> https://developer.gnome.org/accessibility-devel-guide/stable/gad-custom.html.en
> has two problems:
>     * It is outdated.
>     * It is intended as a guide to extend widgets accessibility. A cell
> renderer is not a widget.
>
> What do you mean for gtk_get_accessible? AFAIK, that method call doesn't
> exists. There is a public gtk_widget_get_accessible that returns and
> accessible type, and a private one
> _gtk_cell_renderer_get_accessible_type, that returns a type.
>
> Subclassing GtkTreeViewColumn will not get anything. As explained, it is
> the cell renderer the one that gets the focus and renders the content,
> the problem there is about the custom cell renderer.
>
> So, in summary, and based on your comments and a quick look on the code,
> what it is needed to do here is:
>
>   * Create a new subclass of GtkRendererCellAccessible something like,
> ContactListCellRendererAccessible
>   * Call gtk_cell_renderer_class_set_accessible_type on
> ContactListCellRenderer class_init method.
>   * Reimplement AtkObject.get_name and AtkObject.ref_state_set on
> ContactListCellRendererAccessible, using that "entry" variable to get
> the information
>
> Thanks for all this work
>
> Best regards
>
> On 07/07/2014 04:07 PM, Peter Vágner wrote:
> > Hello,
> > Issue in transmission-gtk is just my guess I haven't yet tryed to
> > tinker with its source code so I may really be absolutelly wrong with
> > my assumption.
> > Venom developers are subclassing GTK_CellRenderer here
> > https://github.com/naxuroqa/Venom/blob/master/src/ui/ContactListCellRenderer.vala
> > . I can see they are also using GtkCellRendererText in order to change
> > a GTK_COMBOBOX which remains accessible here
> > https://github.com/naxuroqa/Venom/blob/master/src/ui/ContactListWindow.vala
> > .
> > While creating my CustomCellRendererAccessible do I really have to do
> > everything that is recommended here
> > https://developer.gnome.org/accessibility-devel-guide/stable/gad-custom.html.en
> > ? As I said I have tried to retrieve a coresponding accessible by
> > calling gtk_get_accessible(MyCustomCellRendererObject). I was able to
> > manipulate that accessible and set its name and description however by
> > testing with orca I have discovered changes I am trying to make result
> > in changes to the parent object treeview in this case not individual
> > rows which as I understand are represented by the CustomCellRenderer.
> > Then I have tried to subclass a GTK_TreeViewColumn where the
> > CustomCellRenderer is connected to by trying to create empty
> > ATK_Object, overridding Get_Accessible() in my subclass. Of course
> > this does not work. I haven't really understood where is the problem
> > however I think It is just not possible to instantiate ATK_Object like
> > all the other objects using new operator.
> >
> > So Now I am lost again and I have no idea on how to possibly move
> > forward. Frankly I don't feel confortable following the article Making
> > Custom Components Accessible on the gnome developers wiki, it's why I
> > have started exploring these things on my own hopefully asking more
> > concrete questions. The only lesson I have learned so far is that I
> > really need CustomCellRendererAccessible. But I don't have an idea on
> > how to do that.
> >
> > Thanks your patience and helpfull hints.
> >
> >
> > Greetings
> >
> > Peter
> >
> > On 07.07.2014 14:02, Piñeiro wrote:
> > > Hi,
> > >
> > > I will try to answer your question as best as I can.
> > >
> > > As you say, sometimes a 3rd party gtk app developer creates a custom
> > > cell renderer in order to add some new visual stuff. The accessibility
> > > related are not skipped. The already in place cell renderer
> > > accessibility is used. But if the new cell renderer uses something
> > > totally different to render text, then the gtk+ cell render accessible
> > > object would not be valid. In that case you would need to provide a
> > > custom accessibility object for that custom cell renderer. For the rest
> > > of this email, I will call them CustomCellRenderer and
> > > CustomCellRendererAccessible
> > >
> > > gtk_cell_renderer_class_set_accessible_type, is just the method that
> > > relates a cell renderer with his accessible method. Is just a utility
> > > method to avoid the need to redefine the method get_accessible for any
> > > custom object. So for this case, once you have a
> > > CustomCellRendererAccessible, you would need to call
> > > gtk_cell_renderer_class_set_accessible_type on your CustomCellRenderer.
> > >
> > > About caring on CellRenderer: as I said, there is already an
> > > accessibility support of CellRenderer. So probably you just need to
> > > focus on that CustomCellRenderer, where the information about name and
> > > state are stored there (that would be the difference with a "vanilla"
> > > CellRenderer), and then try to expose it via a
> > > CustomCellRenderAccessible.
> > >
> > > About that transmission-gtk: after a quick look on Venom. I don't see
> > > any custom cell renderer being created. As far as I see, they are using
> > > GtkCellRendererText, that should be already supported. Are you sure that
> > > in that case you are under a custom cell renderer problem?
> > >
> > > Best regards
> > >
> > > [1] https://developer.gnome.org/gtk3/3.12/GtkCellRendererText.html
> > >
> > > On 07/05/2014 06:20 PM, Peter Vágner wrote:
> > > > Hello,
> > > > A while ago I was trying to get some understanding on how to make 3rt
> > > > party gtk apps accessible. At that time Alejandro Piñeiro pointed me
> > > > to some docs and bugzilla entries describing the current situation.
> > > > Unfortunatelly I haven't still mastered that. I have at least realized
> > > > and hopefully understood at least some verry basic things related to
> > > > this.
> > > > For example currently I am able to set accessible labels and I am able
> > > > to add / tweak relations between labels and the interactive controls
> > > > they are supposed to label. I know this is not a big deal but I have
> > > > already tweaked an app or two this way and I know it works fine.
> > > > Another thing what's currently on my radar are widgets that are often
> > > > reported as tables or treeviews. Individual rows appear to be keyboard
> > > > focusable however orca is unable to report their role and text.
> > > > I guess the common scenario is that the app developers tend to
> > > > subclass Gtk.CellRenderer to create more visually appealing design. In
> > > > this case if I understand correctly the content is directly drawn to
> > > > the widget surface and proper accessibility related properties are
> > > > skipped from the implementation entirely.
> > > > By reading gtk reference docs I have came accross a method
> > > > gtk_cell_renderer_class_set_accessible_type () . That appears to be
> > > > only info I was able to find related to Gtk.CellRenderer and
> > > > accessibility. Can anyone please give me a hint so I might try move
> > > > forward and try learning how to implement accessibility for a widget
> > > > where Gtk.CellRenderer is used?
> > > > Do I need to care about Gtk.CellRenderer or should I just set
> > > > accessibility related properties such as label and description for the
> > > > affected widgets without looking at Gtk.CellRenderer? How do I refer
> > > > to multiple treeview colums or table cells in such implementation? Is
> > > > there an app or just a code example I should look into to see this in
> > > > action?
> > > > I have seen widgets with incomplete accessibility like this in many
> > > > apps but if my explanation is not accurate enough here are two from
> > > > the top of my head. One is the list of torrents in the
> > > > transmission-gtk svn://svn.transmissionbt.com/Transmission/trunk and
> > > > the other is a contact list widget in a gtk3 based tox client called
> > > > venom https://github.com/naxuroqa/Venom .
> > > > I will be looking into this some more, it may take me a while like it
> > > > took me ages to figure out and get used to labelling and related stuff
> > > > so I am just trying maybe with some hint I might master it better this
> > > > time.
> > > >
> > > > Thanks
> > > >
> > > > Peter
> > > >
> > > > _______________________________________________
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> > > > gnome-accessibility-list gnome org
> > > > https://mail.gnome.org/mailman/listinfo/gnome-accessibility-list