Re: Mapping of model attributes with unknown values to a corresponding widget display

[Murray Cumming <murrayc murrayc com>]

On Tue, 2011-10-04 at 14:10 +0200, Markus Elfring wrote:
> > That method's documentation mentions that you can instead create the
> > TreeView::Column manually and use TreeViewColumn::set_cell_data_func()
> > with your own callback slot, which you could use to set the
> > "inconsistent" property:
> > http://developer.gnome.org/gtkmm/unstable/classGtk_1_1CellRendererToggle.html#a680f8f0b502d82a6c909aafe90284026
> 
> I hope that a related method overload exists already in a "convenience library".

I don't really know what you are asking for. I don't know of any library
that does exactly what you want, though I guess libgda-uimm might do
what you want, but probably does more than what you want.

> >> How do you store a "NULL" (SQL) for a model attribute with a data type like
> >> "bool" and update its visual appearance accordingly?
> > 
> > Obviously C++'s bool type can't represent 3 values. You would need
> > something else, I suppose.
> 
> I know that, too ... - I'm just looking for general programming interfaces which
> make the handling of model attributes with unknown values a bit more convenient.
> 
> 
> > Personally, I use Gnome::Gda::Value, from libgda, via libgdamm.
> > It's not wonderful, but it works. 
> 
> I find the documentation for this class incomplete.
> http://developer.gnome.org/libgdamm/4.99/classGnome_1_1Gda_1_1Value.html
> 
> Can such a class be used without the complete database abstraction library?

Yes, if you write it yourself, or accept the LGPL license.

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