One of the many selling point of using Org-mode as a personal wiki (aka digital garden, see previous post) is its (hyper)link feature.
As we’ve seen previously, we can define internal links between Org-file (and/or their outlines), but also external links targeting external files & sytems. Those can either point to stuff openable in Emacs itself (e.g. link to files, to a shell command…) or external applications if configured as such (e.g. web pages).
Conveniently, pasted URL are directly resolved as http(s) links.
As usually, we may have a bunch of links to a few websites, it can be convenient to be able to have those in a shorter form.
Conveniently, Org-mode support link abbreviations.
For example, we may define our list of recurrent linked website.
(setq org-link-abbrev-alist '(("gh" . "https://github.com/")
("gl" . "https://gitlab.com/")
("hn" . "https://news.ycombinator.com/item?id=")
("lines" . "https://llllllll.co/t/")
;; [...]
("thing" . "https://www.thingiverse.com/thing:")))
One would just have to type [[gh:emacs-mirror/emacs]] instead of https://github.com/emacs-mirror/emacs to insert a link to Emacs’ github mirror.
The above solution is nice if we use org-insert-link to insert links.
But I personally find this command cumbersome. It prompts me 3 times (link type, actual link, description).
I want to go faster and just having to type gh:emacs-mirror/emacs to get a valid link.
One way to achieve this is to declare custom link types.
The solution becomes:
(require 'dash)
(setq my-org-link-abbrev-alist '(("gh" . "https://github.com/")
;; [...]
("thing" . "https://www.thingiverse.com/thing:")))
(--each my-org-link-abbrev-alist
(let* ((link-prefix (car it))
(browse-fn `(lambda (e)
(let ((org-link-abbrev-alist my-org-link-abbrev-alist))
(browse-url (org-link-expand-abbrev (concat ,link-prefix ":" e)))))))
(org-link-set-parameters link-prefix :follow browse-fn)))
Please note that we renamed org-link-abbrev-alist to my-org-link-abbrev-alist to prevent having duplicated prefix entries if we ever want to call org-insert-link.
Most of the time, I just copy/paste an URL into an Org buffer.
Wouldn’t it be convenient if it would automagically shorten it if it correspond to a known abbrev?
Thankfully, this is relatively trivial by advising org-yank.
(require 's)
(defun my-org-link-apply-prefix (txt)
"Rework link TXT, swapping prefix w/ shorted one if matches `my-org-link-abbrev-alist'."
(let ((prfx (--some (and (s-starts-with? (cdr it) txt) (not (string= (cdr it) txt)) it) my-org-link-abbrev-alist)))
(if prfx
(s-replace (cdr prfx) (concat (car prfx) ":") txt)
txt)))
(defadvice org-yank (around prf/org-yank-prefix-link activate)
"Advice around `org-yank' that will auto-compact current entry in `kill-ring' if it matches `my-org-link-abbrev-alist'."
(let* ((kill (or (and kill-ring (current-kill 0)) ""))
(new-kill (my-org-link-apply-prefix kill)))
(unless (s-blank? new-kill)
(kill-new new-kill t))
ad-do-it))
Please not that my-org-link-apply-prefix only covers “basic” prefix abbrevs. It doesn’t support formatted abbrevs (%s, %h) nor formatting using a custom function (%(<CUSTOM-FN>) for which we’d need the inverse function).
As always, this shows how flexible Emacs is and how expressive Elisp can be (once you are used to its quirks).
We showcased a very basic example of custom links. One could really go crazy with those.
For more in-depth examples, check out this article from the The Kitchin Research Group blog. They wrote a bunch of advanced articles about Org, notably about Babel (Org’s JupyterLab equivalent).