is there a way to keep only source code inside source code, that is make #+BEGIN_SRC and #+END_SRC invisible? It's cosmetic but it makes things clearer when one have to deal with a lot of short code snippets. For exemple:
(defun org-xor (a b)
"Exclusive or."
(if a (not b) b))
instead of :
#+BEGIN_SRC emacs-lisp
(defun org-xor (a b)
"Exclusive or."
(if a (not b) b))
#+END_SRC
The face for all lines starting with #+ is called org-meta-line.
You can customize this face smaller, darker, etc. to make it less visible.
I use the following piece of code that goes some of the way. It's not perfect. Maybe it will become a proper minor-mode some day. (source).
(with-eval-after-load 'org
(defvar-local rasmus/org-at-src-begin -1
"Variable that holds whether last position was a ")
(defvar rasmus/ob-header-symbol ?☰
"Symbol used for babel headers")
(defun rasmus/org-prettify-src--update ()
(let ((case-fold-search t)
(re "^[ \t]*#\\+begin_src[ \t]+[^ \f\t\n\r\v]+[ \t]*")
found)
(save-excursion
(goto-char (point-min))
(while (re-search-forward re nil t)
(goto-char (match-end 0))
(let ((args (org-trim
(buffer-substring-no-properties (point)
(line-end-position)))))
(when (org-string-nw-p args)
(let ((new-cell (cons args rasmus/ob-header-symbol)))
(cl-pushnew new-cell prettify-symbols-alist :test #'equal)
(cl-pushnew new-cell found :test #'equal)))))
(setq prettify-symbols-alist
(cl-set-difference prettify-symbols-alist
(cl-set-difference
(cl-remove-if-not
(lambda (elm)
(eq (cdr elm) rasmus/ob-header-symbol))
prettify-symbols-alist)
found :test #'equal)))
;; Clean up old font-lock-keywords.
(font-lock-remove-keywords nil prettify-symbols--keywords)
(setq prettify-symbols--keywords (prettify-symbols--make-keywords))
(font-lock-add-keywords nil prettify-symbols--keywords)
(while (re-search-forward re nil t)
(font-lock-flush (line-beginning-position) (line-end-position))))))
(defun rasmus/org-prettify-src ()
"Hide src options via `prettify-symbols-mode'.
`prettify-symbols-mode' is used because it has uncollpasing. It's
may not be efficient."
(let* ((case-fold-search t)
(at-src-block (save-excursion
(beginning-of-line)
(looking-at "^[ \t]*#\\+begin_src[ \t]+[^ \f\t\n\r\v]+[ \t]*"))))
;; Test if we moved out of a block.
(when (or (and rasmus/org-at-src-begin
(not at-src-block))
;; File was just opened.
(eq rasmus/org-at-src-begin -1))
(rasmus/org-prettify-src--update))
;; Remove composition if at line; doesn't work properly.
;; (when at-src-block
;; (with-silent-modifications
;; (remove-text-properties (match-end 0)
;; (1+ (line-end-position))
;; '(composition))))
(setq rasmus/org-at-src-begin at-src-block)))
(defun rasmus/org-prettify-symbols ()
(mapc (apply-partially 'add-to-list 'prettify-symbols-alist)
(cl-reduce 'append
(mapcar (lambda (x) (list x (cons (upcase (car x)) (cdr x))))
`(("#+begin_src" . ?✎) ;; ➤ ➟ ➤ ✎
("#+end_src" . ?□) ;; ⏹
("#+header:" . ,rasmus/ob-header-symbol)
("#+begin_quote" . ?»)
("#+end_quote" . ?«)))))
(turn-on-prettify-symbols-mode)
(add-hook 'post-command-hook 'rasmus/org-prettify-src t t))
(add-hook 'org-mode-hook #'rasmus/org-prettify-symbols))
The org-present package does this. Specifically, it is taken care of by (org-present-add-overlays), which then uses (overlay-put) to make the text invisible. This approach is further described in section 39.6 of the Emacs Lisp manual.
The face for #+BEGIN is org-block-begin-line and for #+END is org-block-end-line. If you already have a dark theme, something like this will make it well nigh invisible, and can be tweaked to your liking or to fit a light theme (hint for light, start with #ffffff):
(set-face-attribute 'org-block-begin-line nil :foreground "#000000")
(set-face-attribute 'org-block-end-line nil :foreground "#000000")
For example, here is the code you posted, with these face attributes set, on top of the Spacemacs dark theme:
Note that this will apply not only to SRC blocks but also to QUOTE blocks, etc.
;; Org mode
(add-hook 'org-mode-hook
'(lambda ()
;; Hide org block lines
;; Unset any previous customization for the background color
(set-face-attribute 'org-block-begin-line nil :background 'unspecified)
(set-face-attribute 'org-block-end-line nil :background 'unspecified)
;; Set the foreground color to the value of the background color
(set-face-attribute 'org-block-begin-line nil
:foreground (face-background 'org-block-begin-line nil 'default))
(set-face-attribute 'org-block-end-line nil
:foreground (face-background 'org-block-end-line nil 'default))
))
Sets the foreground color to the background color, which effectively means hiding the text.
Note: you might need to restart emacs (instead of just reloading the config) for the changes to take effect.
Yet another way to do this is using hide-lines.
The following code is from my emacs config (with a few modifications because I have a lot of self-written macros).
(use-package hide-lines :commands hide-lines hide-lines-matching)
;; The line ~(overlay-put overlay 'invisible 'hl)~ in [[helpfn:][hide-lines-add-overlay]] wouldn't
;; work with the argument =hl=. It works when you set it to =t= instead. Maybe =hl= is
;; depreciated.
(define-advice hide-lines-add-overlay (:override (start end) fix-adding-overlay)
"Add an overlay from `start' to `end' in the current buffer.
Push the overlay into `hide-lines-invisible-areas'."
(let ((overlay (make-overlay start end)))
(setq hide-lines-invisible-areas (cons overlay hide-lines-invisible-areas))
(overlay-put overlay 'invisible t)))
(defun org/hide-source-block-delimiters ()
"Hide property drawers."
(interactive)
(let (selective-display-ellipses org-ellipsis)
;; If properties are folded, ellipsis will show.
(org-show-all)
(hide-lines-matching (rx "#+" (or "begin" "end") "_src" (* nonl) "\n"))))
