[pygtk] Displaying children in a gtk.TreeModelFilter

[Pietro Battiston]

My former email was completely wrong, sorry.

Il giorno ven, 19/02/2010 alle 16.46 +0100, Lionel Dricot ha scritto:
> 
> 
>         (simpler approach, but I guess this is visually _very ugly_
>         and
>         counterintuitive for the user).
>         
>         In any case, I wouldn't want a row to change its appearance...
>         
>         So, what is the best option between the current behaviour and
>         the "show
>         all parents" (the first I presented)? I guess there is no
>         general
>         answer, but that the current is more intuitive for the
>         programmer, and
>         it is easier to workaround it if you need to (I guess that's
>         what
>         seahorse does, for instance).
>         
>         Still, a convenience method to switch from the current
>         behaviour to the
>         "show all parents" one would be a nice feature.
> 
> 
> 
> 
> The more I'm thinking about, the more I'm scratching my head. In fact,
> as soon as you are using TreeModel with children, I cannot find any
> usecase were filters could be useful in their current shape.
> 
> 
> Take for example a list of emails nested by convestation (gmail-like).
> If you do a search, you don't want a mail to be hidden if it matches
> the search but the parent is not. There should be some usecase were
> the current behaviour is useful but I fail to find one.

I do see one: you are exposing a filesystem with your treeview, and want
to show all folders your applications should process. At a certain
moment, a directory is removed from this list (because the app decides
so, or the user unselects it someway - but you don't want to remove it
from the treeview), so now visible_func returns False for it.

In your desired approach, visible_func must change for _all_ children
(and grandons and so on). In the current one, only for the removed row.

That's why I think there is no obviously "right" approach for every
situation. I'd also say that since a tree is usually associated to some
hierarchy, the current one totally makes sense, while the email example

But that said, what I had totally missed is that while the current
behaviour _could_ be obtained (by changing visible_func) if pygtk
behaved as you desire, vice-versa your desired behaviour is _not_
obtainable in the current situation (as far as I know, obviously)...


> 
> I've tried to take the problem in every possible way but I don't find
> any solution to not hide children with an hidden parent. All the
> examples I could find on the web are always for flat list. I suspect
> that the documentation is also written with flat lists in mind.
> 
> 
> 
> 
> So, here's my question : how can you use filter with TreeModel if you
> are not flat ? Please don't tell me to rewrite my TreeModel. It's
> exactly what I wanted to avoid when I started this refactorisation :
> use GTK as it should be, separating the model from the view.
> 

That makes totally sense... and after reading your example I took a look
at Evolution, and saw it obviously recreates the TreeModel.

Pietro