CWS introduces some new API in the css.document module, which allows
access to a document's Undo/Redo stack. It allows adding own undo
actions to the stack and undo/redo of existing actions.
Also, it supports so-called Undo contexts, which encapsulate multiple
Undo actions, which then appear as a single Undo-able entry only. This
is especially interesting for code which does multiple programmatic
changes to a document. Enclosing those changes in an Undo context
means they all can be undone by the user with a single click only.
For details of the API, look at the autodoc-generated IDL reference,
once the CWS is integrated into MWS.