Diagram.ownedPresentation and Presentation.diagram do not behave as normal relationships

[amolenaar]

Adding a listener for diagram.ownedPresentation does only work for delete events.

On creation, event submission is suppressed during the creation of a diagram item. A diagram item gets a diagram on construction and can not exist without a diagram being set. However, since events are suppressed, services like EventDispatcher do not detect updates on the structure and are therefore unaware of changes in Diagram.ownedPresentation.

The reason events are suppressed during construction is that a model element should first be announced via an ElementCreated event. that is the point an element is available from our repository (element factory) That way we know an element exists and the undo manager can track it accordingly.

On the Presentation.diagram item side this is not a problem: there are no listeners for this specific item while it's being created.

Since Presentations are now normal model elements, managed by ElementFactory, it would be good if their properties expose the same behavior.

Version

Version of Gaphor: 2.x

[amolenaar]

Closed by #1088.