The values of the Attributes and of Text nodes are edited using a edition field under the XlmTree, since GtkCTree does not offer inline edition facilities. This edition field can be a dropdown list for attributes whose value must be in a given set. Since all the edition is performed on a copy of the node, it is very easy to rollback the edition. XmlEditorDialog derives from GtkDialog. However, this might take some time, since the XLMSchema spec is a huge beast.
All contributions are welcome.