Re: custom treemodel?

["Murray Cumming" <murrayc murrayc com>]

> Say I've got a class containing a list of values.  For example, a
> Palette class containing a list of colors (something like the
> following incomplete class declaration):
>
>    class Palette
>    {
>       public:
>          typedef std::vector<rgb_t> color_list_type;
>          // snipped other methods
>          color_list_type& colors(void);
>
>       private:
>          color_list_type m_colors;
>    };
>
> Now say I want to display these values in a treeview.  One option is
> obviously to copy all of the values from m_colors into a
> Gtk::ListModel.  But this has a rather large disadvantage in that when
> I make some changes in the treeview (i.e. add a new item, re-order
> items, remove items), I would need to copy these items out of the
> listmodel into a Palette whenever I want to use this group of items as
> a Palette type.

Maybe you should just store the Palette in the list model and use
cell_data_func callbacks to show it in the treeview.

> I'd rather just have the treeview display data directly from the
> Palette class so that I don't need to copy / synchronize things back
> and forth.  So in order to display data directly from the Palette
> class, I'd need to have Palette inherit from Gtk::TreeModel (i.e.
> implement a custom TreeModel).  There is an example in gtkmm CVS that
> shows how to implement a custom TreeModel, but unfortunately I haven't
> had much luck deciphering it (especially the GlueItem stuff).  And
> besides the example, the documentation on implementing custom
> TreeModels is pretty sparse,  Has anybody really done this before?

I've done it in Glom, but the gtkmm example is simpler.

> Does anybody know of other examples I could look at?  Is there a
> better way to solve this problem than implementing a custom TreeModel?
>
> What I think would be helpful is some guidance on what methods need to
> be implemented / overridden and approximately what they're supposed to
> do, etc.  I'd be willing to put together a document like this (maybe
> as a section in the tutorial) if I can get it figured out.

Murray Cumming
murrayc murrayc com
www.murrayc.com
www.openismus.com