Receive messages from a widget draw within a layout to render error messages instead

Hi all,

I have created a "User" Widget to either display a login box or a menu depending on if the user is authenticated or not, but because of the display box is pretty small, there are none room for error messages. The user widget is draw from the main layout file. Now do I wonder what are the best options to send those error message back to the layout so it can show those error messages (if any) instead of the usual content (rendered from the controller).

What should be the best option?

Thanks in advance!