Álvaro Ramírez

27 November 2025 Bending Emacs - Episode 6: Overlays

The Bending Emacs series continues with a new a new episode.

Today we had a quick intro to overlays. Here's the snippet I used for adding snippets:

(save-excursion
  (goto-char (point-min))
  (when (search-forward "Hello World" nil t)
    (let* ((start (match-beginning 0))
           (end (match-end 0))
           (ov (make-overlay start end)))
      (overlay-put ov 'face '(:box (:line-width 1 :color "yellow")))
      ;; (overlay-put ov 'face 'underline)
      ;; (overlay-put ov 'face 'highlight)
      ;; (overlay-put ov 'before-string "🔥 ")
      ;; (overlay-put ov 'after-string  " 🚀")
      ;; (overlay-put ov 'display  "Howdy Planet")
      ;; (overlay-put ov 'invisible t)
      ;; (overlay-put ov 'help-echo "Yay overlay!")
      ;; (overlay-put ov 'mouse-face 'success)
      (overlay-put ov 'category 'overlays)
      (overlay-put ov 'evaporate t)
      ov)))

Similarly, this is what we used for removing the overlay.

(remove-overlays (point-min) (point-max)
                 'category 'overlays)

Of the experiments, you can find:

Redaction snippet at the related blog post.
Dired media metadata at Ready Player's ready-player-dired.el.
Link previews: While I don't have elisp to share for link previews just yet, I did release a tiny thumbnail utility named rinku ;)

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