Shortcuts to Default Directories

[Now largely historical. See ETA for achieving the same effect with bookmarks, and ETA 2 for achieving the same effect with Hydra, which feels better still.]

Yesterday’s Emacs coaching session with Sacha Chua included a sidebar on jumping to and setting default directories. Sacha’s .emacs.d uses registers for this, and her code sets defaults and org-refile targets.

I found later that I had six shortcuts I’d clean forgotten about, that set the default directory and open either dired or a specific file:

(global-set-key (kbd "C-c C-g C-c")
(lambda ()
(interactive)
(setq default-directory "~/.emacs.d/")
(dired ".")))

(global-set-key (kbd "C-c C-g C-h")
(lambda ()
(interactive)
(setq default-directory "~/Dropbox/gesta/")
(find-file "2015.org")))

But a forgotten solution doesn’t count, and having to remember triple-decker key bindings doesn’t help either.

A general solution for the second problem is that an incomplete key binding followed by ? opens a help buffer with all the bindings starting with sequence. C-c C-g ? on my machine yielded:

Global Bindings Starting With C-c C-g:
key binding
— ——-

C-c C-g C-c ??
C-c C-g C-d ??
C-c C-g C-e to-english
C-c C-g C-f to-french
C-c C-g C-h ??
C-c C-g C-p ??
C-c C-g C-r ??
C-c C-g C-u ??
C-c C-g C-w ??

We can make this more useful by switching from defining the key binding functions anonymously inline to moving them out to their own named functions, thus:

(defun my/to-emacs ()
(interactive)
(setq default-directory "~/.emacs.d/")
(dired "."))

(defun my/to-today ()
(interactive)
(setq default-directory "~/Dropbox/gesta/")
(find-file "2015.org"))

(global-set-key (kbd "C-c C-g C-c") ‘my/to-emacs)
(global-set-key (kbd "C-c C-g C-h") ‘my/to-today)

Which fixes those two ?? entries:

C-c C-g C-c my/to-emacs
C-c C-g C-h my/to-today

Another niggle is that I’ve overloaded C-c C-g across three different kinds of commands. Let’s make C-x j the shortcut specifically and only for jumping to a new default directory, and extract some duplicate methods while we’re at it. After:

(defun my/to-file (dir file)
(interactive)
(setq default-directory dir)
(find-file file))

(defun my/to-dir (dir)
(interactive)
(setq default-directory dir)
(dired "."))

(defun my/to-gesta-file (file)
(interactive)
(my/to-file "~/Dropbox/gesta/" file))

(defun my/to-emacs-config ()
(interactive)
(my/to-file "~/.emacs.d/" "sean.org"))

(defun my/to-autrui ()
(interactive)
(my/to-dir "~/code/autrui/"))

(defun my/to-gesta ()
(interactive)
(my/to-dir "~/Dropbox/gesta/"))

(defun my/to-today ()
(interactive)
(my/to-gesta-file "2015.org"))

(defun my/to-readings ()
(interactive)
(my/to-gesta-file "readings.org"))

(defun my/to-writings ()
(interactive)
(my/to-gesta-file "writings.org"))

(defun my/to-twc ()
(interactive)
(my/to-dir "~/Dropbox/gesta/twc/"))

(global-set-key (kbd "C-x j e") ‘my/to-emacs-config)
(global-set-key (kbd "C-x j a") ‘my/to-autrui)
(global-set-key (kbd "C-x j g") ‘my/to-gesta)
(global-set-key (kbd "C-x j h") ‘my/to-today)
(global-set-key (kbd "C-x j r") ‘my/to-readings)
(global-set-key (kbd "C-x j w") ‘my/to-writings)
(global-set-key (kbd "C-x j t") ‘my/to-twc)

C-x j ? then yields:

Global Bindings Starting With C-x j:
key binding
— ——-

C-x j a my/to-autrui
C-x j e my/to-emacs-config
C-x j g my/to-gesta
C-x j h my/to-today
C-x j r my/to-readings
C-x j t my/to-twc
C-x j w my/to-writings

Which is an improvement, but the “Bindings Starting With” help menu is not interactive: we still have to either remember the triple-decker key binding, or type C-x j ? to find the list and then type C-x j h (say) to get the specific shortcut we want. It would be nice if we could over-ride C-x j ? and have it prompt us for one more character to select which of the seven jumps we wanted.

Something like this, in fact:

(defun my/pick-destination (pick)
(interactive "ce = ~/.emacs.d/sean.org a = ~/code/autrui/ g = ~/Dropbox/gesta/ h = …/2015.org r = …/readings.org w = …/writings.org t = …/twc/ ? ")
(case pick
(?e (my/to-emacs-config))
(?a (my/to-autrui))
(?g (my/to-gesta))
(?h (my/to-today))
(?r (my/to-readings))
(?w (my/to-writings))
(?t (my/to-twc))))

(global-set-key (kbd "C-x j ?") ‘my/pick-destination)

interactive "c… takes a single character (see further options here), so the conditional is on a character, which in Emacs Lisp is represented by a ? followed by the character {n}. If there were a single conditional we might use (when (char-equal ?e pick) {n}, but since there are seven of them, we look instead for Emacs Lisp’s equivalent of a switch statement, and find it in case (an alias for cl-case).

So what this does, when you type C-x j ?, is provide a prompt of options in the echo area at the bottom of the screen, and if you type one of the significant letters, it uses that shortcut to default.

Purists would probably prefer to bind ’my/pick-destination to something other than C-x j ? (C-x j j say), so that if we ever bound other commands to something starting with C-x j we would still be able to discover them with C-x j ?. It’s also easier to type because it doesn’t need the shift key for the third element. Having demonstrated that we could over-ride C-x j ? if we wanted to, I’m probably going to side with the purists on this one.

And we’re done. Commit.

ETA: Easier Ways To Do It

That works, but since (see Sacha’s comment below) there are always easier ways to do it:

Simpler Code

find-file will either open a file or open dired if it is passed a directory instead of a file, and opening a file or directory will change the default directory. So we can replace all the extracted ’my/to-file and ’my/to-dir methods with simple find-file calls:

(defun my/to-emacs-config ()
(interactive)
(find-file "~/.emacs.d/sean.org"))

(defun my/to-autrui ()
(interactive)
(find-file "~/code/autrui/"))

… etc …

Using Bookmarks (No Custom Code, Even Simpler)

While ’my/pick-destination gets around the non-interactive nature of ? (minibuffer-completion-help, e.g. C-c C-g ? for list of completions to C-c C-g), using straight-up bookmarks lets you do that without custom code:

C-x r m {name} RET ;; bookmark-set ;; sets a {named} bookmark at current location
C-x r b {name} RET ;; bookmark-jump ;; jump to {named} bookmark
C-x r l ;; list-bookmarks ;; list all bookmarks

So having set bookmarks in the same seven places, either files or directories, we could list-bookmarks and get

% Bookmark File
autrui ~/code/autrui/
emacs ~/.emacs.d/sean.org
gesta ~/Dropbox/gesta/
now ~/Dropbox/gesta/2015.org
readings ~/Dropbox/gesta/readings.org
twc ~/Dropbox/gesta/twc/
writings ~/Dropbox/gesta/writings.org

And this list is interactive. Or we could call C-x r b (bookmark-jump) and start typing the destination we want. (If we get bored of typing, we can reduce the bookmark names to single characters, remembering that C-x r l (list-bookmarks) will give us the translation table if we forget, and then we’re back to being five keystrokes away from any bookmark, without having to add any extra code.)

Using Bookmark+ (And Describing and Customizing Faces)

If we want to be able to do more advanced things with bookmarks – tag them, annotate them, rename them, run dired-like commands on the bookmark list – we can grab the Bookmark+ package and (require ’bookmark+) in our .emacs. (Having done that, if we press e by a line in the bookmark list, for instance, we can edit the lisp record for the bookmark, to rename it or change the destination or see how many times it has been used.)

One problem I had with bookmark+ is that the bookmark list was displaying illegibly in dark blue on a black background. To fix this, I needed to move the cursor over one of the dark blue on black bookmark names and type M-x describe-face, and it reported the face (Emacs-speak for style {n}) of the character, in this case Describe face (default `bmkp-local-file-without-region'):. Pressing enter took me to a buffer which described the face and provided a customize this face link at the end of the first line. I followed (pressed enter) that link to get to a customize face buffer which let me change the styling for that element. On the line:

[X] Foreground: blue [ Choose ] (sample)

I followed (pressed enter on) Choose, it opened a buffer of colour options, I scrolled up to a more visible one, pressed enter again, and got back to the customize face buffer, then went up to “Apply and Save” link and pressed enter again there. Going back to the bookmark list, the bookmarks were visible. The change is preserved for future sessions in the init.el file:

(custom-set-faces
;; custom-set-faces was added by Custom.
;; If you edit it by hand, you could mess it up, so be careful.
;; Your init file should contain only one such instance.
;; If there is more than one, they won’t work right.
‘(bmkp-local-file-without-region ((t (:foreground "green")))))

ETA 2: Using Hydra Instead

Heikki Lehvaslaiho suggested using hydra instead, and as the bookmark solution required a couple of extra keystrokes and I’d been curious about hydra anyway, I thought I’d give it a go.

(require ‘hydra)
(global-set-key
(kbd "C-c j")
(defhydra hydra-jump (:color blue)
"jump"
("e" (find-file "~/.emacs.d/sean.org") ".emacs.d")
("c" (find-file "~/.emacs.d/Cask") "Cask")

("a" (find-file "~/code/autrui/") "autrui")
("h" (find-file "~/Dropbox/gesta/2015.org") "hodie")
("r" (find-file "~/Dropbox/gesta/readings.org") "readings")
("w" (find-file "~/Dropbox/gesta/writings.org") "writings")
("t" (find-file "~/Dropbox/gesta/twc/") "twc")))

I like it. We’re back down to three keystrokes from five and, since we’re providing labels for the commands, we also get the descriptive and interactive and self-updating index which was the big advantage of the bookmark route. If you press C-c j and don’t immediately carry on, it prompts:

jump: [e]: .emacs.d, : Cask, [a]: autrui, [h]: hodie, [r]: readings, [w]: writings, [t]: twc.

Much better. Thanks for the prompt, Heikki!