Re: Native display of line numbers

[Eli Zaretskii]

> Date: Sun, 18 Jun 2017 20:19:33 +0000
> Cc: address@hidden
> From: Alan Mackenzie <address@hidden>
> 
> > Maybe follow-mode could provide a buffer-local variable with the value
> > of that point, and the display engine could simply access that
> > variable?
> 
> Or something like that.  How about a buffer local variable provided by
> the display engine called something like point-window?  Any function
> (here, we're talking mainly follow-mode) could set this to a window, and
> the meaning would be "all relative line numbers should be based from the
> value of point in this window".  This would save the display engine from
> having to check the existence of the variable (follow-mode might not be
> loaded), and updating the value of the variable in follow-mode would be
> straightforward.

That's fine as well, but might be harder to implement, and also
calling Lisp from within the display engine is something I think
should be kept to a minimum.

With my suggestion, checking whether Follow mode is one of buffer's
minor modes is simple enough, and Follow mode should (AFAIU) always
know where's its "point" located, so having a variable with that value
should also be simple.