[emacs] automatically indent to comment-column

[LanX]

Hi

the following emacs lisp code makes typing # DWIM. At the "end" of a perl code line it will automatically indent to the comment-column.

Example typing ..."huhu";#the hash... will produce this indentation:

sub load {
  print "huhu";                 # the hash automatically "jumped"

The code is work in progress if you find bugs feel free to reply here.

(defun my-indent-for-comment (arg)
  "dwim indent-for-comment V0.03"
  (interactive "p")
  (cperl-update-syntaxification (point) (point))
  (if (and
       (not (memq (preceding-char)  '(?$) ))
       ;; (memq (preceding-char)  '( ?\; ?{ ?\( ?\[ ) )
       (memq  (get-text-property (point) 'face) '(cperl-my-trailing-sp
+aces-face nil))
       (looking-at "[[:space:]]*$")
       )
      (cperl-indent-for-comment)
    (insert "#"))
  )        


(add-hook
 'cperl-mode-hook
 (lambda ()
   (local-set-key (kbd "C-#") 'comment-dwim)
   (local-set-key (kbd "#") 'my-indent-for-comment)
   (set-variable 'cperl-comment-column 45 )
   ))

Plz note I also bound C-# to what normally M-; does, because it's much easier to reach on QWERTZ keyboards and IMHO more intuitive in Perl context. Additionally this command will also automatically comment/uncomment selected text.

UPDATE: You have the choice between different levels of aggressiveness, ATM the command checks¹ if the hash doesn't follow a blacklist of chars (actually $). You can change this behaviour to more restrictive whitelisting by uncommenting the following line (i.e. has to follow ; { ( [)

¹) Additionally to excluding any syntax groups (string,command,...) and assuring that only whitespaces follow till the end of line.

[LanX]

The following code will also fix the case of # as delimiter for s///.

Example: typing s#a#b##comment leads to

s#a#b#                         # comment

V0.04

(defun my-indent-for-comment (arg)
  "DWIM indent-for-comment v0.04"
  (interactive "p")
  (cperl-update-syntaxification (point) (point))
  (if (and
       (not (memq (preceding-char)  '(?$) ))
       ;; (memq (preceding-char)  '( ?\; ?{ ?\( ?\[ ) )
       (memq  (get-text-property (point) 'face)
          '(cperl-my-trailing-spaces-face nil))
       (not (get-text-property (point) 'syntax-type))
       (looking-at "[[:space:]]*$")
       )
      (cperl-indent-for-comment)
    (insert "#"))
  )

checking the "face" may be redundant now...

[LanX]

The following code will let "backspace" correct an unwanted jump to comment-column, deleting all previously inserted whitespaces.

example of phases before and after typing bla();#<backspace> (cursor position marked by «)

...
   bla();«
   bla();                            # «
   bla();«

elisp:

 (defun my-cperl-electric-backspace (arg)
   "(Wrapper for my electric commands)
Remove inserted whitespaces or call `cperl-electric-backspace'"
  (interactive "p")
  (if (not (eq last-command  'my-indent-for-comment ))
      (cperl-electric-backspace arg)
    (setq p (point))
    (skip-chars-backward "# \t")
    (delete-region (point) p)
    )
)
  
(add-hook
 'cperl-mode-hook
 (lambda ()
   (local-set-key (kbd "C-#") 'comment-dwim)
   (local-set-key (kbd "#") 'my-indent-for-comment)
   (local-set-key (kbd "DEL") 'my-cperl-electric-backspace)
   (set-variable 'cperl-comment-column 60 )
   ))