Re: bug#347: C mode asks twice about local variables

[Stefan Monnier <monnier@iro.umontreal.ca>]

[ Moving this over to emacs-devel. ]

>> >> Can you try and call `c-file-style' with some extra "don't override"
>> >> (when called from that hack-local-variables-hook) argument so that any
>> >> variable that already has a buffer-local binding will not be
>> >> overridden?
>> Any comment about this suggestion?
> YUCK!!!  ;-)

> I don't know off-hand what the significance of buffer locality is in CC
> Mode styles.

Could you ask the CC mode maintainer, maybe?

> But trying to get a "don't override" parameter to work
> would be horrendous.  hack-local-variables is actually called after the
> language hook, isn't it?  By that time, the CC Mode style will already
> have been set, and the pertinent variables will already be buffer local.
> At least I think so.

I see, yes, it might be messy or even impossible.

>> Non-portability might indeed be a problem (tho, it's obviously "your"
>> problem rather than mine), but introducing a new hook in Emacs-23 won't
>> help you there, so it's not relevant to this discussion.

> What I had in mind was using an (if (boundp 'before-hack-local-variables)
> ...) to separate out new strategy from old.

I'm sure we can come up with a good test to decide whether :safe
will do the right thing.

> Oh, and the hook would need documenting in the Elisp manual, but I can
> manage that.

> Hey, this is so easy and obviously the right thing.  Let's do it!

It's going in the right direction but I'm still not completely satisfied.
How 'bout something like the following:

Some variables can be flagged as being special, in that when they apper
in the file-local list of settings, they "get set" by calling
a function.  E.g. `mode' is globally special and "setting it" will
actually call the corresponding mode.

Then `c-mode' can define `c-file-style' and `c-file-offsets' as being
special so that setting them actually calls a function of yours
(probably a function that could also be used for the :set in defcustom,
BTW).

Of course, the interesting bit is that hack-local-variables will be
careful to reorder the file-local settings such that special variables
are set first.


        Stefan