Work in progress on prefix-hiding, if someone wants to mess with it.

hide-prefix.el

cl--foo
cl-loop


(setq hide-prefix-last-point (cl-remove-if foo bar))


("\\_<\\(cl--\\)\\(\\(\\sw\\|\\s_\\)+\\)"
                               (1 (progn (my-hide-prefix (match-beginning 1) (match-end 1)) nil))
                               (2 font-lock-constant-face))

(font-lock-add-keywords nil '(("\\_<\\(cl-\\)\\([^-]\\)\\(?:\\sw\\|\\s_\\)*"
                               (1 (progn (my-hide-prefix (match-beginning 1) (match-end 1)) nil))
                               (2 hide-prefix-cl-face))
                              ("\\_<\\(hide-prefix-\\)\\([^-]\\(?:\\sw\\|\\s_\\)*\\)"
                               (1 (progn (my-hide-prefix (match-beginning 1) (match-end 1)) nil))
                               (2 font-lock-type-face))))

cl-foo


(defun my-hide-prefix (start end)
  (unless (--keep (overlay-get it 'hide-prefix) (overlays-at start))
    (let ((ov (make-overlay start end nil t)))
      (overlay-put ov 'display "") ;; any prefix possible here
      (overlay-put ov 'hide-prefix t)
      (overlay-put ov 'evaporate t)
      (overlay-put ov 'modification-hooks '(my-hide-prefix-ov-mod)))))

(defun my-hide-prefix-ov-mod (overlay after? beg end &optional length)
  (delete-overlay overlay))

(defvar hide-prefix-last-point 0
  "Point before last command.")

(defvar hide-prefix-last-overlay nil
  "Last expanded overlay.")

(defun hide-prefix-post-command-handler ()
  (when (/= (point) hide-prefix-last-point)
    ;; if there is an overlay before point, show it
    (when hide-prefix-last-overlay
      (overlay-put hide-prefix-last-overlay 'display "")
      (setq hide-prefix-last-overlay nil))
    (let ((ov (car (--filter (overlay-get it 'hide-prefix) (overlays-at (1- (point)))))))
      (when ov
        (overlay-put ov 'display nil)
        (setq hide-prefix-last-overlay ov))))
  (setq hide-prefix-last-point (point)))

(add-hook 'post-command-hook 'hide-prefix-post-command-handler nil t)
(remove-hook 'post-command-hook 'hide-prefix-post-command-handler t)

asd  cl-asd

(let ((oo (cl-loop foo))))
cl-df

sdasd

cl-asd

(defun foo )

(lambda asd)

asd

(defface my-hide-prefix
  '((t (:box (:line-width 1 :color "LightGoldenrod3" :style nil))))
  "foo")

(defvar my-hide-prefix 'my-hide-prefix)

(defface hide-prefix-cl-face
  '((t (:underline (:color "red" :style line))))
  "CL namespace face.")

(defvar hide-prefix-cl-face 'hide-prefix-cl-face)


(defun cl--position (cl-seq cl-start &optional cl-end cl-from-end)
  (if (listp cl-seq)
      (let ((cl-p (nthcdr cl-start cl-seq)))
    (or cl-end (setq cl-end 8000000))
    (let ((cl-res nil))
      (while (and cl-p (< cl-start cl-end) (or (not cl-res) cl-from-end))
        (if (cl--check-test cl-item (car cl-p))
        (setq cl-res cl-start))
        (setq cl-p (cdr cl-p) cl-start (1+ cl-start)))
      cl-res))
    (or cl-end (setq cl-end (length cl-seq)))
    (if cl-from-end
    (progn
      (while (and (>= (setq cl-end (1- cl-end)) cl-start)
              (not (cl--check-test cl-item (aref cl-seq cl-end)))))
      (and (>= cl-end cl-start) cl-end))
      (while (and (< cl-start cl-end)
          (not (cl--check-test cl-item (aref cl-seq cl-start))))
    (setq cl-start (1+ cl-start)))
      (and (< cl-start cl-end) cl-start))))