Change indentation variables inside of buffer

Question

I personally use 2 spaces for indentation but everyone has a preference and I'd like to respect that. When I open someone else's files I would prefer to use their indentation scheme. In my .emacs file here is everything I use to set my indentation:

(setq css-indent-offset 2)
(setq js-indent-level 2)
(setq javascript-indent-level 2)

(setq-default python-indent 2) ;emacs 23                                                                                
(setq-default python-indent-offset 2); emacs 24                                                                         
(add-hook 'python-mode-hook
    (lambda () (setq tab-width 2)))
(setq html-indent-offset 2)
(setq-default indent-tabs-mode nil)
(setq default-tab-width 2)
(add-hook 'html-mode-hook
      (lambda()
      (setq sgml-basic-offset 2)))

I could modify .emacs every time I want to use a different format, but I'd rather visually identify the indentation mode and manually change the variables (for the current emacs process only) to match the indentation of the file.

Now I know very little about emacs/elisp, but my assumption was M-x setq intent-tabs-mode t would make my tab key generate tabs instead of spaces. No such luck and googling has gotten me no where. Any thoughts?

Answer 1

You can define a command that you can use for the switching. Here's a very basic version:

(defun my-set-indents (n)
  "Set the normal indentation amount.  With no argument, sets to 2.
With just one C-u sets to 4.  With any other argument, sets to that amount."
  (interactive "P")
  (setq n (if n (prefix-numeric-value n) 2))

  (setq css-indent-offset n)
  (setq js-indent-level n)
  (setq javascript-indent-level n)

  (setq-default python-indent n) ;emacs 23                                                                                
  (setq-default python-indent-offset n); emacs 24                                                                         
  (add-hook 'python-mode-hook
    (lambda () (setq tab-width n)))
  (setq html-indent-offset n)
  (setq-default indent-tabs-mode nil)
  (setq default-tab-width n)
  (add-hook 'html-mode-hook
    (lambda()
      (setq sgml-basic-offset n)))
  )

Of course, if you use it more than once, that add-hook could be problematical. I think you'll want to take out the add-hook wrapper and just have the setq directly in this code. You can then invoke it with an arg using M-x my-set-indents, or you could put it on a key (sequence).