outline-level-stuff.el

(defun ap/python-mode-outline-hook ()
  (setq outline-level 'ap/python-outline-level)

  (setq outline-regexp
	(rx (or
	     ;; Commented outline heading
	     (group
	      (* space)	 ; 0 or more spaces
	      (one-or-more (syntax comment-start))
	      (one-or-more space)
	      ;; Heading level
	      (group (repeat 1 8 "\*"))	 ; Outline stars
	      (one-or-more space))

	     ;; Python keyword heading
	     (group
	      ;; Heading level

	      ;; TODO: Try setting this to python-indent-offset
	      ;; instead of space.  Might capture the indention levels
	      ;; better.
	      (group (* space))	; 0 or more spaces
	      bow
	      ;; Keywords
	      (or "class" "def")
	      eow)))))

(defun ap/python-outline-level ()
  ;; Based on this code found at
  ;; http://blog.zenspider.com/blog/2013/07/my-emacs-setup-ruby-and-outline.html:
  ;; (or (and (match-string 1)
  ;;	     (or (cdr (assoc (match-string 1) outline-heading-alist))
  ;;		 (- (match-end 1) (match-beginning 1))))
  ;;	(and (match-string 0)
  ;;	     (cdr (assoc (match-string 0) outline-heading-alist)))

  ;; This doesn't work properly. It sort-of works, but it's not
  ;; correct. Running this function consecutively on the same line
  ;; sometimes returns different results. And it doesn't seem to
  ;; correctly recognize top-level Python functions or classes as
  ;; top-level headings, so subheadings beneath them don't collapse
  ;; properly.

  (or
   ;; Commented outline heading
   (and (string-match (rx
		       (* space)
		       (one-or-more (syntax comment-start))
		       (one-or-more space)
		       (group (one-or-more "\*"))
		       (one-or-more space))
		      (match-string 0))
	(- (match-end 0) (match-beginning 0)))

   ;; Python keyword heading, set by number of indentions
   ;; Add 8 (the highest standard outline level) to every Python keyword heading
   (+ 8 (- (match-end 0) (match-beginning 0)))))

(add-hook 'python-mode-hook 'ap/python-mode-outline-hook)


(defun ap/sh-outline-level ()
  (or
   ;; Commented outline heading
   (and (string-match (rx
		       (* space)
		       (one-or-more (syntax comment-start))
		       (one-or-more space)
		       (group (one-or-more "\*"))
		       (one-or-more space))
		      (match-string 0))
	(- (match-end 1) (match-beginning 1) 1))

   ;; Keyword/function heading
   ;; Add 8 (the highest standard outline level) to every keyword
   ;; heading
   (+ 8 (- (match-end 3) (match-beginning 3)))))

(defun ap/sh-mode-outline-hook ()
  (setq outline-level 'ap/sh-outline-level)
  (setq outline-regexp (rx (group (or
				   ;; Outline headings
				   (and (* space)
					(one-or-more (syntax comment-start))
					(* space)
					(group (one-or-more "\*"))
					(* space))

				   ;; Keywords and functions
				   (and (group (* space))
					(or
					 ;; e.g. "function foo"
					 (and (or "function" "if" "elif" "else" "for" "while")
					      (one-or-more space))

					 ;; e.g. "foo()"
					 (and (one-or-more (or alnum "_-"))
					      (* space)
					      (syntax open-parenthesis)
					      (syntax close-parenthesis)))))))))

(add-hook 'sh-mode-hook 'ap/sh-mode-outline-hook)

(defun ap/el-outline-level ()
  (or
   ;; Commented outline heading
   (and (string-match (rx
		       (* space)
		       (group (one-or-more (syntax comment-start)))
		       (one-or-more space))
		      (match-string 0))
	(- (match-end 0) (match-beginning 0) 1))

   ;; Lisp def heading
   ;; Add 8 (the highest standard outline level) to every keyword
   ;; heading
   (+ 8 (- (match-end 0) (match-beginning 0)))))

(defun ap/el-mode-outline-hook ()
  (setq outline-level 'ap/el-outline-level)
  (setq outline-regexp "\\(;;[;]\\{1,8\\} \\|\\((defun\\)\\)"))

(add-hook 'emacs-lisp-mode-hook 'ap/el-mode-outline-hook)

(defun ap/general-outline-level ()
  (or
   ;; Commented outline heading
   (and (string-match (rx
		       (* space)
		       (one-or-more (syntax comment-start))
		       (one-or-more space)
		       (group (one-or-more "\*"))
		       (one-or-more space))
		      (match-string 0))
	(- (match-end 1) (match-beginning 1) 1))))

(defun ap/general-outline-mode-enable ()
  (interactive)
  (setq outline-level 'ap/general-outline-level)
  (setq outline-regexp (rx (group (* space)
                                  (one-or-more (syntax comment-start))
                                  (* space)
                                  (group (one-or-more "\*"))
                                  (* space))))
  (outline-minor-mode))