Custom CellRenderer with custom property

[Aaron Johnson <a-j charter net>]

Hello, I've searched the web for a few days now and am out of ideas...

What I'm trying to do is create a TriState cellrenderer (one of several 
renderers that are part of a column) that can render a value that can 
take 3 states (unchecked, checked, or grayed).  This is represented as 
an integer in the data model.  Here is the closest to what I can figure out:


Gtk::TreeView::Column *tvc = new Gtk::TreeView::Column("Test");
tvc->pack_start(renderer, false);
tvc->pack_start(columns.col_name);
tvc->add_attribute(renderer, "tristate", columns.col_state);

I get this when it tries to render the cells
(Tierra.exe:4892): GLib-GObject-WARNING **: g_object_get_property: 
object class
`gtkmm__GtkCellRenderer' has no property named `tristate'

I can figure out that it wouldn't know about my tristate property, but I 
can't figure out how to register it.  I've tried to simply define a 
property like this in the TriStateCellRenderer class:
Glib::Property<int> tristate;  // instantiated as 
TriStateCellRenderer::TriStateCellRenderer : tristate(*this, "tristate");

However it gives me this error:
(Tierra.exe:4892): GLib-GObject-CRITICAL **: 
g_object_class_install_property: as
sertion `class->set_property != NULL' failed

I thought I was getting close, but as I go through the glib, glibmm, 
gtk, and gtkmm source I'm getting lost.  I figure I'm missing some sort 
of callback that is called when the property is set, but I can't figure 
out how or where to set it. 

Obviously I'm doing something wrong.  I can't believe I haven't found 
some example that doesn't do this.  I've seen references to 
CustomCellRenderer (even in the gtkmm sources), but it seems to have 
been removed.  Can someone point me to an example of a CellRenderer 
using properties.  The built in renderers (e.g. CellRendererText) seem 
to be taking advantage of some property handling built into Gtk.

Am I close or way off?  Any suggestions?