Boon: An Ergonomic Command Mode for Emacs
Boon is a complete package for modal editing, which is not Evil.
- Ergonomic: common commands are easy to type. (See below)
- Lightweight: ~300 loc for its core.
- Good Emacs integration: integrates well with existing Emacs infrastructure and takes advantage of it.
It is largely accepted that modal edition is more ergonomic than using key-chords. Boon attempts to make modal editing as comfortable as possible, by adhering to the following design principles:
Spacial allocation first, mnemonics second: the allocation of keys to commands is primarily based on the locations of keys on the keyboard. Whatever is printed on the key cap is a secondary concern.
Easy finger rolls: common key combinations should either be left/right hand alternation or easy one-hand rolls.
Use of home row and strong fingers for the most used commands
Easy navigation: many commands are bound to navigation. This allocation of keys facilitates moving around, which is the most common task when editting text. Because movements double up as region-definitions, this design also makes manipulation commands more powerful.
Prefer an easy two-keystroke combination to a single hard-to-reach key. Hard-to-reach keys are free for the user to bind to rarely used commands (often user and mode-dependenent).
In command mode, movement keys are bound to the right hand, while text manipulation is bound to the left hand.
The leftwards (and upwards) movements are bound to the leftmost fingers (index and middle finger), while rightwards (and downwards) movements are bound to the rightmost fingers (ring finger and pinky.) Additional unpaired, movements are bound to the middle column (extended reach with index).
The most common edition commands (cut, paste, parenthesis manipulation) are bound to the home row. The top row is (mainly) for searching. The bottom row gives access to regular Emacs stuff (C-x ...) (C-c ...), insert mode, and registers.
Emacs Integration: Reusable Modules
Boon is designed as set of modules, largely independent of each other. Each module is customizable and provides reusable components, in full agreement with the Emacs spirit. This means that even if you disagree with the design choices explained above, you may still want to use some parts of Boon. The structure of Boon is as follows:
- boon-moves.el and boon-search.el provide a set of move and search commands. These work the same way as standard Emacs commands --- they are merely more powerful (or just have different emphasis). Frontends typically bind these commands (in addition to standard ones) in the boon keymaps.
- boon-arguments.el provides a set of selectors to define regions. (These selectors are the equivalent of vim 'text objects'). Selectors include plain regions (words, lines, paragraphs, ...), but also region transformers (think: exclude borders, just borders, including spaces, each, etc.). Additionally every move command (in the boon-moves-map keymap) can be used as a selector which means that they are easily customized. On top of it all, the system supports multiple-cursors (multiple regions will be returned when multiple cursors are active).
- boon-core.el provides an infrastructure for modal editing. The implementation is very much inspired from evil-core, but heavily simplified.
- boon-main.el provides a set of commands. These are similar to standard Emacs commands, but they use the system of selectors described above. (For good measure, some random extra commands are thrown in.) These commands may be used in combination with a modal system or not. A few commands also switch to insert mode.
- boon-keys.el, boon-colemak.el, boon-qwerty.el are frontends. Those require all the above and provide a mapping of moves, selectors and commands onto keys.
- Emacs version >= 25.1
- Qwerty or Colemak layout (workman version partially implemented).
(require 'boon-colemak) ;; (require 'boon-qwerty) ;; for qwerty port
(boon-mode) ;; to enable boon everywhere
If you just eval'ed the above (or just did not want to enable boon everywhere), Boon may not be active in the current buffer. If it is not activated and you want to try it locally, activate it by
(You'll get the version of the tutorial adapted to the frontend you have activated, qwerty or colemak.)
The main variables to configure are:
- boon-select-map, boon-moves-map, boon-command-map. (Those are keymaps.)
- boon-enclosures (can be
If you use powerline, you may want to:
(require 'boon-powerline) (boon-powerline-theme) ;; if you want use powerline with Boon
Comparison with other modal layers for Emacs
Evil is a (quite) complete vi emulation layer for Emacs.
In contrast, in Boon, much of Emacs structure is leveraged and user experience is retained. Examples: the
xkey gives the
C-xprefix map. The usual Emacs (interactive) arguments are used for text objects. Thus most of Boon remains usable even if one does not wish to use modal editing.
Besides, Evil use vi bindings (by default at least), which do not feature the best ergonomics.
Xah Fly Keys http://ergoemacs.org/misc/ergoemacs_vi_mode.html
Like boon, Xah Fly Keys aims at providing a layout whose design is ergonomic. As far as I understand it follows the spirit of Xah's ErgoEmacs package. As I understand ErgoEmacs makes most design decisions differently from boon. I have not made an in-depth comparison of ergonomics yet.
Fingers borrows a few ideas from Boon, including the division of work between left and right hand. fgeller gives a detailed account of the particular differences with Boon. My opinion is that Fingers is compatible with Boon concepts and could (and probably should) be implemented as a Boon 'frontend'.
Modalka is an engine to "introduce native modal editing of your own design". Thus its purpose is similar to
boon-core.el. It could be possible in the future to replace parts of boon-core with a dependency on Modalka. However at the moment it does not seem suitable. The main issue is that modalka does not support several states; it can only be either activated or not.
RYO modal mode https://github.com/Kungsgeten/ryo-modal
RYO modal has the same purpose as Modalka and boon-core. Compared to Modalka, it provides support for repeating the last command. However RYO modal's method is incompatible with Emacs' repeat (and consequently also with boon complex commands). Additionally it suffers from the same drawback as Modalka: it has a single state.
God-mode is similar to "sticky modifier keys" in principle. Its simplicity allows to quickly get up to speed with it. However, it lacks the main benefit of a true modal layer: text operators. (what vi fans call a "language for text edition").
Modal Mode http://retroj.net/modal-mode (Last updated in 2014)
Another modal layer for Emacs, which is also lightweight and aims to integrate with Emacs. However, as far as I can see, there is no special attention paid to ergonomics.