Elmord's Magic Valley

Software, lingüística e rock'n'roll. Sometimes in English.

Managing windows and taking notes from Emacs

2018-02-14 00:02 -0200. Tags: comp, emacs, in-english

EXWM and Org mode are two entirely unrelated pieces of Emacs software. However, by virtue of both running in Emacs, they can be combined in some interesting ways.

EXWM

EXWM is a window manager written in Emacs Lisp. I think this is the craziest thing I've seen written in Emacs Lisp so far, and yet it moves. It basically turns Emacs into a tiling window manager. Your windows become Emacs buffers, and you can manage them with the usual Emacs commands for splitting windows, changing focus, switching buffers, and so on. (I learned about it here.)

As a window manager, I don't think it does anything very interesting compared to other tiling window managers. Its real power comes from being integrated into Emacs. This means I can always use Emacs commands no matter what window I am in (for example, if I want to open a file, I can hit C-x C-f no matter what program currently has focus).

This also means it can be customized and scripted in Emacs Lisp. For example, one thing I did with it is make it display "urgent" windows (those that would usually blink in the taskbar) in my Emacs mode line. So far, that's not very interesting, because with a conventional desktop environment I would already have windows highlighted in the taskbar. But what I have also done is customize it so that some windows are detected as "urgent" even though they don't set the urgency window manager hint. For example, I have windows with titles like (1) Skype (i.e., windows with unread messages) tagged as urgent as well.

Another nice trick you can do with EXWM is send fake keypresses to windows. For example, one thing I did was to make a variant of Emacs' insert-char command (which allows entering characters by their Unicode name or hex codepoint) which can be called from any window, by asking for the character name, putting it into the clipboard, and then sending a fake C-v to the application.

My EXWM config file is here. It has grown a bit complex, and some things are still a bit kludgy/glitchy, but I've been using it for some 3-4 months for now. Take the parts you like from it.

Org-capture

Org is an Emacs mode for managing structured data in plain-text format, though that description doesn't really do justice to the thing. It can manage to-do lists, agendas, handle tables in awesome ways, and many more things. It can also export files to various formats, including Beamer presentations, which I've written about before. I'm still learning how to use it and all of its features, and I'm trying to use it for more things, including blogging. (I wrote some kludgy code to export Org files to blog posts, but I found out afterwards that it would be better to create a new export backend inheriting from the built-in HTML export backend. Still have to learn more about this though.)

One cool feature of Org mode is org-capture, a command for taking notes with little flow interruption from what you are currently doing. Once you have it all configured, you can hit something like C-c c j to create an entry using the journal template. The entry will be pre-filled according to the template, and can include, for example, a link to the place you called the command from. For example, if you call it from a w3m buffer, the new note will contain a link to the web page you were visiting. If you call it from some source code, it will create a link to the place you were in the source code file. Org can recognize a variety of different buffer types, and create links appropriate to the context you called it from. You can easily make it recognize new kinds of context by defining new functions and adding them to org-store-link-functions.

Combining the two things

The most immediately observable advantage of using Org-capture in conjunction with EXWM is that you can call it from anywhere, not just regular Emacs buffers, because now Emacs commands work from any window. No matter whether you are seeing a file or reading something in Firefox, you can just type C-c c j to take a note. I find this really nice.

Another advantage is that because you can add new functions to org-store-link-functions, and all your windows are now Emacs buffers, you can actually make org-capture recognize the context of non-Emacs windows too. This is especially useful for browser windows: you can make the link inserted in the note reflect the page you are visiting. Although I'm not aware of a clean way to extract the current URL from a browser window, you can make do by faking the keypresses of C-l (to select the address bar) followed by C-c (to copy the contents to the clipboard), and then reading the clipboard contents from Emacs. Like this:

;; Grab address from the browser.
(defun elmord-exwm-get-firefox-url ()
  (exwm-input--fake-key ?\C-l)
  (sleep-for 0.05)                      ; Wait a bit for the browser to respond.
  (exwm-input--fake-key ?\C-c)
  (sleep-for 0.05)
  (gui-backend-get-selection 'CLIPBOARD 'STRING))

;; org-store-link functions must either return nil (if they don't recognize
;; the context), or call `org-store-link-props' with the appropriate link
;; properties and return non-nil.

(defun elmord-exwm-org-store-link ()
  (when (and (equal major-mode 'exwm-mode)
             (member exwm-class-name '("Firefox" "Firefox-esr")))
    (org-store-link-props
     :type "http"
     :link (elmord-exwm-get-firefox-url)
     :description exwm-title)))         ; Use window title as link description.

;; Finally, we add the new function to the list of known store-link functions.
(add-to-list 'org-store-link-functions 'elmord-exwm-org-store-link)

I find this really cool.

That's all, folks

I have more things I'd like to write about Emacs, but that's it for now.

Comentários (2)

Mannimarco, the King of Worms, 2018-02-14 08:22:48 -0200 #

Juro que quando li "managing windows" eu achei que tu ia ensinar o pessoal como agüentar lidar com o Windows 10 quando fosse obrigado :P. De resto, o post está [i]muito[/i] frio.


Mannimarco, the King of Worms, 2018-02-14 08:23:12 -0200 #

[i]realmente[/i]*


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