How to control indentation after an open parenthesis in Emacs

Question

When I use emacs python-mode, if the last character of a line is an open parenthesis it indents the next line just one step in from the indentation of the previous line.

call_some_function(
    some_very_long_argument_that_I_want_to_put_on_its_own_line)

I like that. Now in ecmascript-mode (which I am using for actionscript 3), it always indents to the level of the previous parenthesis.

call_some_function(
                   this_is_not_really_saving_me_any_horizontal_space);

How can I make ecmascript-mode indent like python-mode in this respect?

Answer 1

Since ecmascript-mode is based on cc-mode, you can use c-set-offset which allows you to customize any syntactic symbol's offset with the preferred value.

In your case, go to the point which is indented in the wrong level, hit Cc Co (or type Mx c-set-offset ), accept the suggested symbol ( arglist-intro ), and set it a new value (eg + , the default offset).

You can also do it programmatically in your dotemacs, for instance, with:

(add-hook 'ecmascript-mode-hook
          (lambda ()
            (c-set-offset 'arglist-intro '+)
            (c-set-offset 'arglist-close 0)))

Answer 2

ecmascript-mode seems to be based on cc-mode . If you set the indentation style for cc-mode , it will also work for ecmascript-mode . I have the following code in my .emacs . When I use ecmascript-mode it indents as desired:

;;{{{ c/c++ indent style variables

(require 'cc-mode)

(defconst my-c-style
  '(
    (c-electric-pound-behavior     . 'alignleft)
    (c-tab-always-indent           . t)
    (c-hanging-braces-alist        . ((block-open)
                                      (brace-list-open)
                                      (substatement-open)
                                      (defun-open before after)
                                      (defun-close before after)
                                      ))
    (c-hanging-colons-alist        . ((member-init-intro before)
                                      (inher-intro)
                                      (case-label)
                                      (access-label      after)
                                      (label             after)
                                      (access-key        after)))
    (c-cleanup-list                . (scope-operator
                                      empty-defun-braces
                                      defun-close-semi))
    (c-offsets-alist               . ((arglist-close        . c-lineup-arglist)
                                      (case-label           . 4)
                                      (statement-case-intro . 4)
                                      (access-label         . -4)
                                      (label                . -)
                                      (substatement-open    . 0)
                                      (block-open           . 0)
                                      (knr-argdecl-intro    . -)))
    )
  "My C++/C Programming Style")


; Customizations for both c-mode and c++-mode
(defun my-c-mode-common-hook ()
  ; set up for my perferred indentation style, but  only do it once
  (c-add-style "My" my-c-style 'set-this-style)
  ; we like auto-newline and hungry-delete
  (c-toggle-auto-hungry-state 1)
  ; keybindings for both C and C++.  We can put these in c-mode-map
  ; because c++-mode-map inherits it
  (define-key c-mode-map "\C-m" 'newline-and-indent)
  ; insert 8 tabs
  (setq tab-width 8)
 )

;;}}}

Answer 3

Thank you Török Gábor, in my case I prefered to set

(add-hook 'XXX-mode-hook
      (lambda ()
              (c-set-offset 'arglist-cont-nonempty '+)))

I was looking for something like this :

veryLongFunctionName (bar, bar, bar)

For a more exhaustive list of variables : read emacs documentation