Sorry, the "%d" thing was a bug. It looks like the let-binding error was
introduced after my last checkout, though, so I guess that's deal with.

This all raises the issue, though: what's the accepted replacement for
frame-local variables, and why are they deprecated in the first place? My
package has rather a few of them, and it's very useful to be able to use
them like variables. I want to make them available for user customization,
let-bind them, and use them without having to go through lots of manual
frame-parameter rigamarole each time. I would rather not break any user
customizations using these variables. So what should I do?

On Mon, May 17, 2010 at 6:45 AM, Stefan Monnier <monnier@iro.umontreal.ca>wrote:

> > I've run into a bug with GNU Emacs 24.0.50.1 (i686-pc-linux-gnu, GTK+
> > Version 2.16.1, checked out from the repo a week or so ago). Let-binding
> > frame-local variables doesn't work: although the let-bound value is
> correct
> > within the `let', it doesn't get reset after the `let'. To reproduce,
> just
> > run http://gist.github.com/403208.
>
> I definitely cannot reproduce the behavior you show on that page:
> The code stops at "(message "Before: %d" foo)" because foo has
> value nil at that point which is incompatible with the %d format.
> If I get rid of this bug, then I bump into the next error which is that
> `let' raises "Frame-local vars cannot be let-bound".
>
> Note that frame-local variables have been deprecated since Emacs-22.2,
> and I definitely intend to remove support for them (tho for Emacs-24.1,
> the plan is currently only to remove support for let-binding them).
>
>
>        Stefan
>