option 2: component-specific object
GridLayout Interaction State
{
    selectedChildId: ViewerId,
    isHighlighted: boolean,
}

interactionManager.getAllComponents().withType('GridLayout').subscribe(
    'onEnterPressed',
    (subscriber: { ..., interactionState: GridLayout Interaction State }, message, globalState) => {
        if (globalState.selected === subscriber.viewerId) {
            console.log('I'm the selected one!');
            interactionManager.publish({
                eventName: 'PrintSomething',
                message: {  },
            });
        }
        globalState.selected = subscriber.viewerId;
    }
);

type ViewerHandle = {
    viewerId: ViewerId,
    parent: ViewerHandle,
};

type GridLayoutHandle extends ViewerHandle = {
    viewModel: {
        type: 'GridLayout',
        content: null,
        metadata: null,
    },
    selectedChildId: ViewerId,
}

type InteractionState = {

};

type InteractionManager = {

};

im.type().filter()

im.forEach()

im.type('GridLayout').forEach((viewer: ViewerHandle<GridLayout>) => {
    viewer.on('onEnterPressed', (message: Message, global: InteractionState) => {
        if (global.selectedId === viewer.viewerId) {
            im.emit('PrintSomething', {});  // (topic, message)
        }
        console.log(viewer.selectedChildId);
    });
    viewer.on('onEscPressed', (message, globalState) => {

    });
});