TreeView::append_column_numeric() format?

["Murray Cumming" <murrayc murrayc com>]

At the moment, Gtk::TreeView::append_column() can add numeric columns, but
there is no way to specify how the number will be shown, such as how many
decimal points or leading zeroes. So people have to use
set_cell_data_func() and do the formatting in a callback.

So I would like to add another templated convenience method like this:
Gtk::TreeView::append_column_numeric(TreeModelColumn& model, numeric_format);

But what's the best way to specify the display format for the number? I'd
rather not use that nasty printf() style format. Does C++ have something
more suitable?

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