Different options for different modes?

[winkerbean]

Hi,

Can Someone point Me in the direction of documentation which shows how
to set different options for different modes? (e.g., preserving tabs
as tabs in a ruby file while converting tabs to four ' ' characters in
a c file) I have searched thru the docs Myself and, though I may have
missed it, I did not see the information. I am using 23.3.

Thanks in advance.

[Stefan Monnier]

The general approach is to use something like

(add-hook 'MAJOR-MODE-hook
(lambda ()
(set (make-local-variable 'VAR) VAL)))

where MAJOR-MODE is the name of the major mode, and I'll let you guess
what VAR and VAL might be.


Stefan

[Philipp Haselwarter]

to set options for certain modes emacs uses `hooks', usually following
the naming scheme `foo-mode-hook' where "foo" is the mode in question.

Check out the section on hooks in the emacs info manual:

C-h i m Emacs m Hooks

a quick example could be
#+begin_src: elisp
(defun my-ruby-coding-style nil
(setq indent-tabs-mode t))

(defun my-c-coding-style nil
(setq indent-tabs-mode nil
tab-width 4))

(add-hook 'c-mode-hook 'my-c-coding-style)
(add-hook 'ruby-mode-hook 'my-ruby-coding-style)
#+end_src

--
Philipp Haselwarter

[rusi]

Stefan Monnier wrote:
> The general approach is to use something like
>
> (add-hook 'MAJOR-MODE-hook
> (lambda ()
> (set (make-local-variable 'VAR) VAL)))

I wonder when this is used and when this:

(eval-after-load 'MAJOR_MODE (setq VAR VAL))

[Stefan Monnier]

>> (add-hook 'MAJOR-MODE-hook
>> (lambda ()
>> (set (make-local-variable 'VAR) VAL)))

> I wonder when this is used and when this:
> (eval-after-load 'MAJOR_MODE (setq VAR VAL))

Your code will be run once when loading the `MAJOR_MODE' package
(i.e. usually the first time `MAJOR_MODE' is used), whereas the code
I quoted is run every time `MAJOR-MODE' is enabled.

If you use Emacs for a single file at a time, the difference between the
two may be unnoticeable. But if you do use several files in the same
Emacs session (which is the normal way to use Emacs), then the
difference is important.


Stefan