Show notifications to user as feedback if something fails modifying the model.

[rhumbertgz]

Hi again!

How could be possible to show a notification to the user after a general action (e.g create a node X) cannot be executed (e.g., only a Node X is allowed per diagram).

I have a particular node "EntryConcept" that act as root or entry point for my diagram, so I only want to allow create only node of that type.

Since it a validation at the model level not a particular element of my diagram I can't use for an example GIssueMarkerView. However I noticed that if there is problem loading the model I get some notifications (see image below).

I have a basically have a custom CreateNodeOperationHandler where I check if the diagram has already a particular Node, if yes, I just exit without creating the new node. That works, but I would like to give some feedback to the user.

[rhumbertgz]

Looking at the source code of the @eclipse-glsp/server-node I found the solution for both notifications. Here I share my findings in case they can help others

Inject an action dispatcher to your handler class implementation (e.g., CreateNodeOperationHandler)

@inject(ActionDispatcher)
protected actionDispatcher: ActionDispatcher;

For actions notifications like '1' (the message is shown when hovering over the INFO icon) use:

this.actionDispatcher.dispatch( ServerStatusAction.create('Your Message', { severity: 'INFO', timeout: 5000 }));

For messages notifications like '2' use:

this.actionDispatcher.dispatch(ServerMessageAction.create('Your Message', { severity: 'INFO', timeout: 5000 }));

Here you can see the result: