[gtkmm] Custom types in a Gtk::TreeView

[Roger Leigh <roger whinlatter uklinux net>]

I've written a custom class, numeric, which does fast fixed-point
arithmetic.  I'd like to display this directly in a Gtk::TreeView.
After adding it to the TreeModel, and then adding the column to the
view, no problems occur, but when I try to set the data, I get errors:

(test:24166): GLib-GObject-WARNING **: unable to set property
`text' of type `gchararray' from value of type `glibmm__CustomBoxed_N4EPIC7numericE'

What is the best way to convert from "numeric" to a "Glib::ustring".
I've overloaded std::ostream operator<< in the class, but this doesn't
appear to be used.

I can see that I can create a custom cell_data_func handler to set
property_text, but since I will be using this in quite a lot of
different treeviews, I don't want to have to write a handler for each
numeric column in each view.

Would deriving a custom CellRenderer from CellRendererText be a
possibility?  What I can't see here is what method is called to turn
the object in the model into a Glib::ustring.  How does the
CellRenderer "know" which TreeModelColumn it is rendering?

If I create a custom CellRenderer, is it possible to make this the
default renderer for a particular type, so when I add a new view
column to the treeview this renderer is chosen automatically?


Many thanks,
Roger

-- 
Roger Leigh

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