Custom cell renderer for multi-line editable text

[Nathan Fredrickson <nathan silverorange com>]

I have been searching for a way to create a TreeView with cells
containing multi-line editable text.  The GtkCellRendererText can be set
as editable, but it only allows the editing of a single line.

A custom cell renderer can be created to display multiple lines of text,
but the tough part seems to be the multi-line editor.  I've searched
unsuccessfully for such a custom cell renderer.  Has anything like this
been written before?

Nathan