Design

#1

This document describes the design goals for Kakoune, including
rationales.

Interactivity

Unlike Vim, Kakoune does not have an underlying line-oriented editor,
and is always expected to be used in an interactive (i.e. with the
edited text being displayed in real time) fashion. That should not
prevent Kakoune from being used non interactively (executing macro for
example), but priority should be given to ease of interactive use.

Limited scope

Kakoune is a code editor. It is not an IDE, not a file browser, not a
word processor and not a window manager. It should be very efficient at
editing code, and should, as a side effect, be very efficient at editing
text in general.

Composability

Being limited in scope to code edition should not isolate Kakoune from
its environment. On the contrary, Kakoune is expected to run on a
Unix-like system, along with a lot of text-based tools, and should make
it easy to interact with these tools.

For example, sorting lines should be done using the Unix sort command,
not with an internal implementation. Kakoune should make it easy to do
that, hence the | command for piping selected text through a filter.

The modern Unix environment is not limited to text filters, most people
use a graphical interface nowadays, and Kakoune should be able to take
advantage of that, without hindering text mode support. For example
Kakoune supports multiple clients on the same editing session, so that
multiple windows can be used, letting the system window manager handle
its responsibilities such as tiling or tabbing.

Orthogonality

Kakoune features should be as orthogonal as possible, for example, in
Vim, there are multiple ways for modifying the buffer: Through
normal/insert mode, command mode, and Vim scripts. In Kakoune, modifying
the buffer is the normal/insert mode job.

That means there should be clear separation of concerns between modes:

  • normal mode is for manipulating the selection and the selection
    contents.

  • insert mode is for interactive insertion into the buffer.

  • command mode is for non-editing features (opening a file, setting
    options…).

Orthogonality is an ideal, and should not prevent common sense
pragmatism, the gf and ga commands are not strictly selection
manipulation ones, but fit nicely with other goto commands, and hence
are acceptable in normal mode even though they could arguably be moved
to command mode.

Modes should be orthogonal, and commands in modes should be as well. For
example, Vim uses d and x for very similar things: deleting text. In
Kakoune only d exists, and the design ensures that x is not needed.

Speed

Kakoune should be fast, fast to use, as in a lot of editing in a few
keystrokes, and fast to execute.

  • Vim is the benchmark here, most editing tasks should be doable in
    less or the same number of keys.

  • Kakoune be designed with asynchronicity in mind, launching a
    background process and using its result when available should not
    block the editor.

  • Kakoune should be implemented with speed in mind, a slow editor is a
    useless one.

Simplicity

Simplicity is nice, simplicity correlates with orthogonality and speed,
and makes things easier to understand, bugs easier to fix, and code
easier to change.

  • No threading: multithreading is a hard problem, and is not well
    suited to a text editor:

    • Either we want a direct result, and we need to be synchronous
      with the user, so getting a 4x speed up is meaningless, we need
      to have an algorithm which appears instantaneous the user.

    • Or we want an asynchronous result, and then the processing is
      best left to a helper command which can be reused with other
      Unix tools.

  • No binary plugins: shared object by themselves add a lot of
    complexity. Plugins add another interface to Kakoune, and goes
    against orthogonality. The %sh{ … } and socket interface should be
    made good enough for most plugin use cases.

    • It is better to write Kakoune-independent helper tools
      (intelligent code completer, source code navigation programs)
      that can interact with Kakoune through the shell than write them
      in a plugin.
  • No integrated scripting language: for the same reason as binary
    plugins.

  • Limited smartness: Kakoune should not try to be too smart, being
    smart is often unpredictable for the user, and makes things context
    dependent. When Kakoune tries to be smart, it should provide the
    alternative, non smart version (* tries to detect word
    boundaries on the selection, but alt-* permits to avoid this
    behavior).

Unified interactive use and scripting

As both an effect of Orthogonality and Simplicity, normal mode is
not a layer on top of a text editing language layer (normal mode
keys are not bound to text editing commands), normal mode is the
text editing language.

That means there is no delete-selected-text command that d is bound
to, d is the delete selected text command.

This permits to have scripting use case and interactive use cases share
the same text editing language. Both use normal mode to express complex
edition.

Besides promoting simplicity by avoiding the introduction of another
layer, this helps ensure the interactive editing language is as
expressive as possible as we need to make it able to handle complex use
cases, such as indentation hooks.

Language agnostic

Kakoune should not be tailored for writing in a specific programming
language. Support for different languages should be provided by a kak
script file, built-in language support should be avoided.

Self documenting

Kakoune should be able to document its features, live documentation
along with an extensive suggestion/completion system provides the
discoverability which is often lacking in non GUI tools. Documentation
should as much as possible be integrated with the code so that it stays
up to date.

Vim compatibility

Kakoune is inspired by Vim, and should try to keep its commands close to
Vim’s if there are no compelling reasons to change. However
self-consistency is more important than Vim compatibility.