[Moose-dev] How to know when a playground has changed?

Hi all, With the valuable support from Johan, I'm migrating my Grafoscopio interactive notebook project to last Pharo 5 / Moose 6 and its getting in a really good shape (see screenshot below). Now I would like to migrate the auto-update functionality when a node is changed. When text nodes is easy, but for code nodes, I need to know when a playground has changed, to send the proper message to the tree, updating its contents. How to know when a playground contents has changed? Cheers, Offray