Indentation of newlines

Question

I am writing source code and a lot of times I need to press Enter and have the newline indented with 4 spaces more than the previous. As I don't want to do it always, I would like to be able to use C-RET to achieve this.

While searching I found C-j (newline-and-indent) but it always indents with the same amount of spaces and not relatively to the current line.

How can I achieve that?

To make myself clear, what I want is:

First line

/* Not indented. */

    Second line 

    /* Second line indented with 4 spaces. */

        Third line

        /* Third line indented with 4 spaces
        but relative to the second so now it
        has 8 spaces. */

Answer 1

Here's a simple function that indents (with spaces) 4 spaces relative to the previous line:

(defun indent-relative (&optional arg)
  "Newline and indent 4 spaces relative to previous line.  With
C-u, indent to same level as previous line."
  (interactive "P")
  (let* ((amount (if arg 0 4))
         (indent (+ amount (save-excursion
                             (back-to-indentation)
                             (current-column)))))
    (newline 1)
    (insert (make-string indent ?\s))))

(global-set-key (kbd "C-<return>") #'indent-relative)

Answer 2

You can bind the C-RET to do exactly that: newline and 4 spaces.

(global-set-key (kbd "C-<return>") "\C-j    ")