They shall not automatically hide! That's NeXT design - never hide something,
deactivate it.
Riccardo—I’ll be the first to agree with you that autohiding scrollbars are
usually terrible. I say “usually”, because there is a notable exception: touch
UIs. In a touch UI, scrollbars themselves are terrible.
So two comments: 1) because there are situations where auto-hiding scrollbars
are desirable, I believe the theming engine should support it. That way, people
can design a touch-first theme that delivers a first-class touch UI experience.
And 2) it seems to me that sticking to every NeXT design principle is silly—at
least at the level of preventing new themes from going in a different direction.
I totally agree that NeXTSTEP was amazing, particularly when you compare it
against its contemporaries. But 1) the NeXT team was composed of imperfect
humans and 2) they were designing interfaces quite a long time ago. We should
allow for the possibility that somebody has had a good idea in the years
following 1997.
The wonderful thing about themes is that it is not necessary for us to agree on
what the perfect UI looks like. But we would make a mistake if we limit the
capabilities of the theming engine itself based on something NeXT decided 30
years ago. Some themes can follow NeXT’s conventions and others not.