bug#12463: 24.2; pos-visible-in-window-p gets slower over time

[Eli Zaretskii]

> From: Stefan Monnier <monnier@IRO.UMontreal.CA>
> Cc: Juanma Barranquero <lekktu@gmail.com>, cyd@gnu.org, jwalt@garni.ch,
>         12463@debbugs.gnu.org
> Date: Fri, 21 Sep 2012 12:38:25 -0400
> 
> >> > I don't know why that function accepts a LIBRARIES argument, rather than
> >> > just making callers bind Vdynamic_library_alist.
> >> That's what it did in the original design, but someone (Stefan, I
> >> think) asked that it was passed as an argument. I have always disliked
> >> that, as it seems highly unlikely that any other variable will ever be
> >> used. I'd be happy to see that argument removed.
> > Well, then maybe Stefan could explain why he wanted it.
> 
> Sorry, can't remember.  Probably because I generally prefer passing
> arguments explicitly over passing them via dynamic binding.

We have gobs of functions in Emacs that access global variables like
Vdynamic_library_alist.  I don't think one more function will change
anything.