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Why Kakoune -- The quest for a better code editor
=================================================
Maxime Coste <mawww@kakoune.org>
image::kakoune_logo.svg[align="center", link="http://kakoune.org"]
Why invest time into text editing
---------------------------------
While discussing with fellow developers, I was asked the following question
a few times: We spend most of our time as developers thinking, not editing
code; so, why invest time into mastering a complicated code editor, and why
lose some cognitive resources on thinking about text editing instead of
about the real programming problem?
I think this point of view is misguided, for a few reasons:
* Despite their name, code editors are not only about editing, but also about
code navigation. Programming is a hard task partly due to the huge amount of
context we have to keep in mind, and being able to quickly navigate code helps
us refresh that context, by looking at definitions, implementations, and comments.
* Although code editing itself is not the most important part of programming,
it still takes non-negligible time to perform, and can be optimized by using
better tools.
* Finally, a programming career spans a few decades, so investing a few weeks
to improving our editing and navigating speed is definitely worth it.
Why a modal text editor
-----------------------
What is modal text editing
~~~~~~~~~~~~~~~~~~~~~~~~~~
Now that we have established that investing time into mastering text editing
is worth it, let's focus on why I think modal text editors are the way to go.
A modal text editor can be, as its name implies, in different modes. Depending
on the current mode, keys have different effects: in *insert* mode most keys
insert their character in the buffer, as in non-modal editors, but in *normal*
(default) mode, keys have a different effect. For example, `w` can move the
cursor to the next word, `y` can yank (copy) the current selection, `p` can
paste, `u` can undo, `g` followed by `f` can open the filename under the cursor...
Some commands from *normal* mode would change the mode, for example `i` would
enter *insert* mode, from which the `<esc>` key would return to *normal* mode.
The first thing to realize is that non-modal text editors are extremely biased
towards insertion. They make insertion easy (by making the default behaviour of
most keys to insert a character into the buffer) at the expense of making most
other operations suboptimal, by requiring hard to reach keys or modifiers (or,
even worse, moving your hand all the way to your mouse).
Insertion is a key part of text editing, and is worth optimizing, which is
the whole point of completion systems. But it is only a small part of text
editing, we spend a huge amount of our editing time navigating, moving code
around, copying, pasting and reformating.
A modal text editor makes all these operations much more accessible, and easier
to express. But they are not only about having convenient shortcuts.
Modal editing as a text editing language
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Many vi users have an epiphany when they realize that vi does not just
provide a set of modes making various text editing shortcuts easier to type,
but actually provides a text editing language.
Commands are composable in order to express complex changes, `dw` in vi is
not just a shortcut to delete a word, it is the combination of a *verb*: `d`
for delete, with an *object* `w` for word. There are more complex objects like
`ib` (inside block) refers to the content of the parenthesis surrounding
the cursor, so `yib` would yank (copy) the text inside the surround
parenthesis.
This language allows the programmer to express their intent much more closely
than in other editors; most editors can express "delete the word after the
next parenthesis", but more often than not, expressing that intent is more
cumbersome than simply doing an ad-hoc edit. Text editing as a language
changes that, by making clearly expressing your intent the fastest and easiest
way to do your edit.
This is a desirable property because a lot of text editing operations are
repetitive, but only on structurally similar text: the subject text are
different, but they follow the same structure. Being able to express the
text editing at the structural level allows for reusable commands, and makes
the computer do the repetitive job.
Another often overlooked property of using a text editing language is that
it's fun. Programmers are problem solvers, we enjoy solving problems, and
we enjoy even more solving them with a clean and efficient solution. This
kind of text editor transform a dull and repetitive edition task into an
interesting puzzle to solve, and that is an engaging thing.
Think about it this way: Yes, programming is about thinking, concentrating
on a design problem, or on a bug, understanding what needs to be done,
designing a solution, and then writing it. More often that not, once you get
to the writing phase, most of the thinking, problem solving, part is done,
now the remaining task is just editing the code. Modal editors make this
phase both faster, and more fun.
Why Kakoune
-----------
Up to now, I have used vi as an example for modal text editor, mostly because
I expect most programmers have at least heard of it. However, I dont believe
vi and clones are the best modal text editor out there.
I have been working, for the last 5 years, on a new modal editor called
Kakoune. It first started as a reimplementation of Vim (the most popular vi
clone) whose source code is quite dated. But, I soon realized that we could
improve a lot on vi editing model.
Improving on the editing model
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
vi basic grammar is *verb* followed by *object*; it's nice because it matches
well with the order we use in English, "delete word". On the other hand,
it does not match well with the nature of what we express: There is only
a handfull of *verbs* in text editing (**d**elete, **y**ank, **p**aste,
**i**nsert...), and they don't compose, contrarily to *objects* which can be
arbitrarily complex, and difficult to express. That means that errors are
not handled well. If you express your object wrongly with a delete verb,
the wrong text will get deleted, you will need to undo, and try again.
Kakoune's grammar is *object* followed by *verb*, combined with instantaneous
feedback, that means you always see the current object (In Kakoune we call
that the selection) before you apply your change, which allows you to correct
errors on the go.
Kakoune tries hard to fix one of the big problems with the vi model: its
lack of interactivity. Because of the *verb* followed by *object* grammar,
vi changes are made in the dark, we dont see their effect until the whole
editing *sentence* is finished. `5dw` will delete to next five words, if
you then realize that was one word too many, you need to undo, go back to
your initial position, and try again with `4dw`. In Kakoune, you would do
`5W`, see immediately that one more word than expected was selected, type
`BH` to remove that word from the selection, then `d` to delete. At each
step you get visual feedback, and have the opportunity to correct it.
At the lower level, the problem is that vi treats moving around and selecting
an object as two different things. Kakoune unifies that, moving *is* selecting.
`w` does not just go to the next word, it selects from current position to
the next word. By convention, capital commands tend to expand the selection,
so `W` would expand the current selection to the next word.
Multiple selections
~~~~~~~~~~~~~~~~~~~
Another particular feature of Kakoune is its support for, and emphasis
towards the use of multiple selections. Multiple selections in Kakoune
are not just one additional feature, it is the central way of interacting
with your text. For example there is no such thing as a "global replace" in
Kakoune. What you would do is select the whole buffer with the `%` command,
then select all matches for a regex in the current selections (that is the
whole buffer here) with the `s` command, which prompts for a regex. You would
end up with one selection for each match of your regex and use the insert
mode to do your change. Globally replacing foo with bar would be done with
`%sfoo<ret>cbar<esc>` which is just the combination of basic building blocks.
.Global replace
video::video/global-replace.webm[align="center", options="autoplay,loop"]
Multiple selections provides us with a very powerfull to express structural
selection: we can subselect matches inside the current selections, keep
selections containing/not containing a match, split selections on a regex,
swap selections contents...
For example, convert from `snake_case_style` to `camelCaseStyle` can be done
by selecting the word (with `w` for example) then subselecting underscores
in the word with `s_<ret>`, deleting these with `d`, then upper casing the
selected characters with `~`. The inverse operation could be done by selecting
the word, then subselecting the upper case characters with `s[A-Z]<ret>`
lower casing them with ` and then inserting an underscode before them with
`i_<esc>` This operation could be put in a macro, and would be reusable
easily to convert any identifier.
.Camel case to snake case
video::video/camel.webm[align="center", options="autoplay,loop"]
Another example would be parameter swapping, if you had `func(arg2, arg1);`
you could select the contents of the parenthesis with `<a-i>(`, split the
selection on comma with `S, <ret>`, and swap selection contents with `<a-)>`.
.Swapping arguments
video::video/args-swap.webm[align="center", options="autoplay,loop"]
It is as well easy to use multiple selections for alignment, as the `&`
command will align all selection cursors by inserting blanks before
selection start
.Aligning variables
video::video/align.webm[align="center", options="autoplay,loop"]
Or to use multiple selections as a way to gather some text from different
places and regroup it in another place, thanks to a special form of pasting
`<a-p>` that will paste every yanked selections instead of the first one.
.Regrouping manager objects together
video::video/regroup.webm[align="center", options="autoplay,loop"]
Interactive, predictible and fast
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A design goal of Kakoune is to beat vim at its own game, while providing a
cleaner editing model. The combination of multiple selections and cleaned up
grammar shows thats its possible to have text edition that is interactive,
predictible, and fast at the same time.
Interactivity comes by providing feedback on every commands, the inverted
*object* then *verb* grammar makes that possible, every selection modification
has direct visual feedback, regex based selections incrementally show what
will get selected, including when the regular expression is invalid, and even
yanking some text displays a message notifying how many selections were yanked.
Predictibilty comes from the simple effect of most commands. Each command is
conceptually simple, doing one single thing. `d` deletes whatever is selected,
nothing more. `%` selects the whole buffer, `s` prompts for a regex and
selects matches in the previous selection. It is the combination of these
building blocks that allows for complex, but predictible, actions on the text.
Being fast, as in less keystrokes, is provided by carefully designing the set
of editing commands so that they interact well together, and by sometimes
sacrificing beauty for useability. For example, `<a-s>` is equivalent to
`S^<ret>`, they both split on new lines, but this is a so common use case that
it deserves to have its own key. As shown in http://github.com/mawww/golf,
Kakoune manages to beat Vim at the keystroke count game in most cases,
using much more idiomatic commands.
Discoverability
~~~~~~~~~~~~~~~
Keyboard oriented programs tend to be at a disadvantage compared to GUI
applications because they are less discoverable; there is no menu bar on
which to click to see the available options, no tooltip appearing when you
hover above a button explaining what it does.
Kakoune solves this problem through the use of two mechanisms: extensive
completion support, and auto-information display.
When a command is written in a prompt, Kakoune will automatically open a menu
providing you with the available completions for the current parameter. It
will know if the parameter is supposed to be a word against a fixed set
of word, the name of a buffer, a filename, etc... Actually, as soon as `:`
is typed, entering command prompt mode, the list of existing commands will
be displayed in the completion menu.
Additionally, Kakoune will display an information box, describing what the
command does, what optional switches it can take, what they do...
.Command discoverability
video::video/discoverability.webm[align="center", options="autoplay,loop"]
That information box gets displayed in other cases, for example if the `g`
key is hit, which then waits for another key (`g` is the *goto* commands
prefix), an information box will display all the recognized keys, informing
the user that Kakoune is waiting on a keystroke, and listing the available
options.
To go even further in discoverability, the auto information system can
be set to display an information box after each normal mode keystroke,
explaining what the key pressed just did.
Extensive completion support
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Keyboard oriented programs are much easier to work with when they provide
extensive completion support. For a long time, completion has been prefix
based, and that has been working very well.
More recently, we started to see more and more programs using the so called
fuzzy completion. Fuzzy completion tends to be subsequence based, instead
of prefix based, which means the typed query needs to be a subsequence of
a candidate to be considered matching, instead of a prefix. That will generate
more candidates (all prefix matches are also subsequence matches), so it
needs a good ranking algorithm to sort the matches and put the best ones first.
Kakoune embraces fuzzy matching for its completion support, which kicks in both
during insert mode, and prompt mode.
.Word completion support
video::video/completion.webm[align="center", options="autoplay,loop"]
Insert mode completion provides completion suggestions while inserting in the
buffer, it can complete words from the buffer, or from all buffers, lines,
filenames, or get completion candidates from an external source, making it
possible to implement intelligent code completion.
.Language specific completion support
video::video/cpp-completion.webm[align="center", options="autoplay,loop"]
Prompt completion is displayed whenever we enter command mode, and provides
completion candidates that are adapted to the command being entered, and to
the current argument being edited.
A better unix citizen
~~~~~~~~~~~~~~~~~~~~~
Easily making programs cooperate with each others is one of the main strength
of the Unix environment. Kakoune is designed to integrate nicely with a POSIX
system: various text editing commands give direct access to the power of POSIX
tools, like `|`, which prompts for a shell command and pipe selections through
it, replacing their contents with the command output, or `$` that prompts for
a command, and keeps selections for which the command returned success.
.Using external commands as filters
video::video/filters.webm[align="center", options="autoplay,loop"]
This is only the tip of the iceberg. Kakoune is very easily controllable from
the shell, just pipe whatever commands you like to `kak -p <session>`, and the
target Kakoune session will execute these.
Kakoune command line also supports shell expansion, similar to what `$(...)`
does in a shell. If you type `echo %sh{ echo hello }` in the command prompt,
"hello" will get displayed in the status line. Various values from Kakoune
can be accessed in these expand through environment variables, which, along
with shell scripting forms the basis of Kakoune extension model.
.Interaction with external shell
video::video/external.webm[align="center", options="autoplay,loop"]
This model, although a bit less familiar than integrating a scripting language,
is conceptually very simple, relatively simple implementation-wise, and is
expressive enough to implement a custom code completer, linters, formatters...
Moreover, combined with support for `fifo` buffers, that read data from a
named `fifo`, Kakoune ends up with an extension model that easily support
asynchronous tasks, by forking a shell in the background to do long lived
work (`grep` or `make` for example) while displaying the result as they
come through the `fifo`.
Kakoune also tries to limit its scope to code editing: in particular, it does
not try to manage windows, and lets the system's window manager, or terminal
multiplexer (such as tmux), handle that responsiblity. This is achieved through
a client/server design: An editing session runs on a server process, and
multiple clients can connect to that session to display different buffers.
.Asynchronous make and multiple clients in tmux
video::video/async.webm[align="center", options="autoplay,loop"]
Final Thoughts
--------------
Kakoune provides an efficient code editing environment, both very predictible,
hence scriptable, and very interactive. Its learning curve is considerably
easier than Vim thanks to a more consistent design associated with strong
discoverability, while still being faster (as in less keystrokes) in most
use cases.
Although easier to learn than Vim, the learning curve is still quite steep,
however we have established that investing time into optimizing the text
editing workflow is worth it for programmers. Moreover, Kakoune simply makes
code editing a fun and rewarding experience.
Kakoune is still evolving, getting better as we get more users, and gathering
more use cases to cater for. It's already a very good code editor, and we need
you to use it so that it can be made even better.
Kakoune is available at http://github.com/mawww/kakoune and has a website at
http://kakoune.org