> I propose the following [brief/ main steps of a] concrete solution for
> changing the color of a hidden tab whose process gave output in the
> meantime:
>
> 1. Every tab has a unique ID that can be read and not modified. This ID is
> dubbed by the system at the creation of the tab.
This is pointless. Window configurations don't need a 'unique ID',
neither does this. Just reify the tab: make it a unique Lisp object type
(again, like window-configurations). Now the tab object serves as its
own unique ID.
We were talking here about a method to implement the hourglass functionality of a tab.
Please read the previous discussion , and what means message passing in scheme. I was talking about that.