Re: custom treemodel?

[Paul Davis <pjdavis engineering uiowa edu>]

Murray Cumming wrote:

> > 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.
>
>  
After poking around a bit in my freshly built gtkmm, I noticed this:

gtkmm/examples/Makefile.am
# Doesn't build with GLIBMM_ENABLE_PROPERTIES unset:
#cellrenderercustom

Dunno if thats important or not though.

> > 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
>
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