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68d7309 Dec 8, 2016
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Kakoune design

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 it’s environment. On the contrary, Kakoune is expected to run on an 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 pipping 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 it’s responsibilities such as tiling or tabbing.

Orthogonality

Kakoune features should be as orthogonal as possible, for example, in Vim, there is 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 it’s 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).

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 it’s commands close to Vim ones if there is no compelling reasons to change. However self consistency is more important than Vim compatibility.