Indentation after braces in C

Question

I don't know what the formal name of it is (this being one of the reasons that I can't find how to achieve it). But, what I want is to make Emacs start the second bracket with the same amount of space that is used in the first one and when you press Enter to go in a new line, that line to start with the same amount of spaces if there is a bracket.

I am not looking for a weird customization (unless it is a last resort). I just am looking for a typical feature in most IDE, that I am sure you use if you write code in your Emacs.

What I want to achieve is this:

for(i=0;i<10;i++)
{
    if(i<5)
    {

        /* I want by pressing Enter the cursor to start in here 
        so to write the print */
        print("Text")


    }
    /* I want this bracket to close automatically 
    under the first one (of the if) and not in the beginning. */

}

Answer 1

Your question appears to be dealing with two independent issues:

1. you want the RET character to automatically indent; and
2. you want an indentation style that is different from the Emacs default.

Electric RET

A character that performs something else than just inserting itself is called electric in Emacs. There are two ways in Emacs to make RET electric: the generic electric-mode, which you enable by doing M-x electric-indent-mode, and works in all modes; and the CC-mode specific minor mode electric mode, which you enable by typing C-c C-l in a CC-mode buffer.

Please try both, and choose whichever your prefer.

Changing the style of indentation

Your preferred indentation style differs from Emacs' default in two ways: it uses 4 spaces indentation, while Emacs uses 2, and it puts curly braces beneath the control operators, rather than on the same line.

The former issue is easily solved:

(setq-default c-basic-offset 4)

The latter is hardly more involved:

(setq c-default-style (cons '(c-mode . "k&r") c-default-style)

You can change the used style for a single buffer by doing M-x c-set-style. Please see the CC-Mode info manual for the available styles.

Answer 2

smartparens, a solution for advanced handling of pairs (such as (), [], {}, <>, ...) supports pre- and post-action hooks. With these it's possible to make Emacs indent the content of a {} pair after hitting RET after the beginning {, the } is inserted at the same time as the {. The following snippet is taken from the documentation and sets up the described behaviour for C++:

(sp-local-pair 'c++-mode "{" nil :post-handlers '((my-create-newline-and-enter-sexp "RET")))

(defun my-create-newline-and-enter-sexp (&rest _ignored)
  "Open a new brace or bracket expression, with relevant newlines and indent. "
  (newline)
  (indent-according-to-mode)
  (forward-line -1)
  (indent-according-to-mode))