Re: Emacs's handling of line numbers [from bug#5042]

[Eli Zaretskii]

> From: Stefan Monnier <address@hidden>
> Cc: address@hidden,  address@hidden
> Date: Sat, 17 Apr 2010 10:45:19 -0400
> 
> > What are these two ``kinds'' of restriction you are talking about, and
> > how are they relevant to the issue at hand, which is how to number
> > lines when a buffer is narrowed?
> 
> He's proposing to distinguish between two different kinds of narrowing
> (aka "restrictions").

Yes, but what _are_ these two kinds?  How are they different from one
another?