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Also, since addons are not extending from a HTMLElement, addons cannot subscribe to events themselves. HTML events are only going upwards in the DOMTree, not downwards and/or to siblings.

Pros/Cons

Decision

If we want plug-ins for OpenSCD to be asynchronous accessible to each other, OpenSCD-Core should make use of a central event-bus.
Instead of dispatching an event on the plug-in itself, the plug-in can dispatch an event on the central event-bus.

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It is possible to stop the event from bubbling further inside a plugin. This means that a plugin can negate an event that should be handled by a different plugin. (Plugin A sends an event (that should be read by Plugin B), Plugin C is listening to this event and stops the event from going further (event.preventDefault()). Because of Plugin C, plugin B never gets the event).

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Alternative: Window object

Listen to the window .this.object. This object is used everywhere in the OpenSCD application.

Pro's:

Con's

• Risk of becomming a distributored monolith: Distributed Monoliths vs. Microservices: Which Are You Building? | Scout APM Blog
• OpenSCD cannot run in an iframe

Consequences

Implementing a central event-bus means that current OSCD plugins need some refactoring to dispatch events to the event-bus instead of dispatching events on itself.

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