[ESS] fill-column in Rnw files

[Kasper Daniel Hansen]

On Thu, Jul 14, 2011 at 10:29 AM, Stephen Eglen
<S.J.Eglen at damtp.cam.ac.uk> wrote:
>> If I set the fill-column in an Rnw file to a non-standard value (say
>> 100, standard is 70) inside a Latex chunk and I move around and pass
>> an R chunk, the fill-column value gets reset.  This looks like a bug
>> to me.
>
> How did you change the value of the variable?  Every time you switch
> from R to latex, it will re-run e.g. latex-mode, so that any variables
> set temporarily will be lost.  If you set it through a hook, you may
> have better luck.  e.g.
>
>  (add-hook 'LaTeX-mode-hook '(lambda() (setq ...)))
>
> as the hooks will be rerun each time you switch mode.
>
> This is a limitation of the current .Rnw setup.

Thanks for the pointer.  During experiments I have been setting it
using C-x f (ie. interactively), but my real use case is to use a file
local variable like

% Local Variables:
% fill-column: 100
% End:

at the end of my .Rnw file (because several people edits this file).
I have now "solved" this by having

% Local Variables:
% eval: (add-hook 'LaTeX-mode-hook '(lambda () (setq fill-column 100)))
% End:

I have put "solved" in quotes because not only does this piece of code
affect other latex buffers I will be editing (this might not be so
bad, I like fill-column 100), but it also affect other buffers of
other users who edits this file in Emacs.  Nevertheless, it seems like
the only solution right now?

Kasper