Handler

Indicates a function within a Listener should be registered as a Handler

The function can read from different accessors by adding arguments SourceScope, TargetScope, EventScope. They may appear in any order, be omitted, or used as a receiver.

If SourceScope is nullable or omitted, the handler will not be called when there is no source present on the event.

Example:

@Handler
fun TargetScope.doSomething(source: SourceScope, event: EventScope) {
    // Within here, you may use accessors defined for all three.
}