Delete message view when operation deleted

[Matthias Schoettle]

When an operation is deleted, corresponding message view (if it exists) should be deleted as well. Otherwise there will be dangling references.

[Matthias Schoettle]

References issue #143: Added deletion of message view (if it exists) to removal of operation.

When removing the message view, the scene doesn't (try to) remove the view, because it might not have been opened yet.

One issue remains. When undoing the removal and the message view is added again: The scene switches to the message view, even though this is probably not wanted by the user. We need to find a way to prevent doing this in this case.

→ <<cset a00236e46a4c>>

[Omar Alam]

The message view layout does not get deleted when deleting its operation. Therefore, the tool gives an exception when saving the model (it says: message view is not contained).

[Matthias Schoettle]

One issue remains. When undoing the removal and the message view is added again: The scene switches to the message view, even though this is probably not wanted by the user. We need to find a way to prevent doing this in this case.

I think there should be no regular reaction to adding a new message view. Instead, the handler (that requests the creation of a message view) listens to model changes and then acts to display it. This is also done, for example, in StructuralViewHandler.createNewClass(...).

[Matthias Schoettle]

References issue #143: Added missing removal of layout of message view.

→ <<cset 5d8c447fc0f5>>

[Matthias Schoettle]

Resolved issue #143: The remaining problem is resolved by having the handler listen to model changes and once the message view was added it is displayed. That way, when the message view is deleted and undo is performed, the message view will not be automatically displayed.

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