bendns' repos / helix
Unnamed repository; edit this file 'description' to name the repository.
Crate Description
helix-core Core editing primitives, functional.
helix-syntax Tree-sitter grammars
helix-lsp Language server client
helix-view UI abstractions for use in backends, imperative shell.
helix-term Terminal UI
helix-tui TUI primitives, forked from tui-rs, inspired by Cursive

This document contains a high-level overview of Helix internals.

NOTE: Use cargo doc --open for API documentation as well as dependency documentation.

Core

The core contains basic building blocks used to construct the editor. It is heavily based on CodeMirror 6. The primitives are functional: most operations won't modify data in place but instead return a new copy.

The main data structure used for representing buffers is a Rope. We re-export the excellent ropey library. Ropes are cheap to clone, and allow us to easily make snapshots of a text state.

Multiple selections are a core editing primitive. Document selections are represented by a Selection. Each Range in the selection consists of a moving head and an immovable anchor. A single cursor in the editor is simply a selection with a single range, with the head and the anchor in the same position.

Ropes are modified by constructing an OT-like Transaction. It's represents a single coherent change to the document and can be applied to the rope. A transaction can be inverted to produce an undo. Selections and marks can be mapped over a transaction to translate to a position in the new text state after applying the transaction.

NOTE: Transaction::change/Transaction::change_by_selection is the main interface used to generate text edits.

Syntax is the interface used to interact with tree-sitter ASTs for syntax highling and other features.

View

The view layer was supposed to be a frontend-agnostic imperative library that would build on top of core to provide the common editor logic. Currently it's tied to the terminal UI.

A Document ties together the Rope, Selection(s), Syntax, document History, language server (etc.) into a comprehensive representation of an open file.

A View represents an open split in the UI. It holds the currently open document ID and other related state.

NOTE: Multiple views are able to display the same document, so the document contains selections for each view. To retrieve, document.selection() takes a ViewId.

The Editor holds the global state: all the open documents, a tree representation of all the view splits, and a registry of language servers. To open or close files, interact with the editor.

LSP

A language server protocol client.

Term

The terminal frontend.

The main function sets up a new Application that runs the event loop.

commands.rs is probably the most interesting file. It contains all commands (actions tied to keybindings).

keymap.rs links commands to key combinations.

TUI / Term

TODO: document Component and rendering related stuff

de>idle-timeout Time in milliseconds since last keypress before idle timers trigger. Used for autocompletion, set to 0 for instant. 400 completion-trigger-len The min-length of word under cursor to trigger autocompletion 2 auto-info Whether to display infoboxes true true-color Set to true to override automatic detection of terminal truecolor support in the event of a false negative. false rulers List of column positions at which to display the rulers. Can be overridden by language specific rulers in languages.toml file. [] bufferline Renders a line at the top of the editor displaying open buffers. Can be always, never or multiple (only shown if more than one buffer is in use) never color-modes Whether to color the mode indicator with different colors depending on the mode itself false

[editor.statusline] Section

Allows configuring the statusline at the bottom of the editor.

The configuration distinguishes between three areas of the status line:

[ ... ... LEFT ... ... | ... ... ... ... CENTER ... ... ... ... | ... ... RIGHT ... ... ]

Statusline elements can be defined as follows:

[editor.statusline]
left = ["mode", "spinner"]
center = ["file-name"]
right = ["diagnostics", "selections", "position", "file-encoding", "file-line-ending", "file-type"]
separator = "│"
mode.normal = "NORMAL"
mode.insert = "INSERT"
mode.select = "SELECT"

The [editor.statusline] key takes the following sub-keys:

Key Description Default
left A list of elements aligned to the left of the statusline ["mode", "spinner", "file-name"]
center A list of elements aligned to the middle of the statusline []
right A list of elements aligned to the right of the statusline ["diagnostics", "selections", "position", "file-encoding"]
separator The character used to separate elements in the statusline "│"
mode.normal The text shown in the mode element for normal mode "NOR"
mode.insert The text shown in the mode element for insert mode "INS"
mode.select The text shown in the mode element for select mode "SEL"

The following statusline elements can be configured:

Key Description
mode The current editor mode (mode.normal/mode.insert/mode.select)
spinner A progress spinner indicating LSP activity
file-name The path/name of the opened file
file-base-name The basename of the opened file
file-encoding The encoding of the opened file if it differs from UTF-8
file-line-ending The file line endings (CRLF or LF)
total-line-numbers The total line numbers of the opened file
file-type The type of the opened file
diagnostics The number of warnings and/or errors
workspace-diagnostics The number of warnings and/or errors on workspace
selections The number of active selections
primary-selection-length The number of characters currently in primary selection
position The cursor position
position-percentage The cursor position as a percentage of the total number of lines
separator The string defined in editor.statusline.separator (defaults to "│")
spacer Inserts a space between elements (multiple/contiguous spacers may be specified)

[editor.lsp] Section

Key Description Default
enable Enables LSP integration. Setting to false will completely disable language servers regardless of language settings. true
display-messages Display LSP progress messages below statusline[^1] false
auto-signature-help Enable automatic popup of signature help (parameter hints) true
display-signature-help-docs Display docs under signature help popup true

[^1]: By default, a progress spinner is shown in the statusline beside the file path.

[editor.cursor-shape] Section

Defines the shape of cursor in each mode. Note that due to limitations of the terminal environment, only the primary cursor can change shape. Valid values for these options are block, bar, underline, or hidden.

Key Description Default
normal Cursor shape in normal mode block
insert Cursor shape in insert mode block
select Cursor shape in select mode block

[editor.file-picker] Section

Sets options for file picker and global search. All but the last key listed in the default file-picker configuration below are IgnoreOptions: whether hidden files and files listed within ignore files are ignored by (not visible in) the helix file picker and global search. There is also one other key, max-depth available, which is not defined by default.

All git related options are only enabled in a git repository.

Key Description Default
hidden Enables ignoring hidden files. true
follow-links Follow symlinks instead of ignoring them true
deduplicate-links Ignore symlinks that point at files already shown in the picker true
parents Enables reading ignore files from parent directories. true
ignore Enables reading .ignore files. true
git-ignore Enables reading .gitignore files. true
git-global Enables reading global .gitignore, whose path is specified in git's config: core.excludefile option. true
git-exclude Enables reading .git/info/exclude files. true
max-depth Set with an integer value for maximum depth to recurse. Defaults to None.

[editor.auto-pairs] Section

Enables automatic insertion of pairs to parentheses, brackets, etc. Can be a simple boolean value, or a specific mapping of pairs of single characters.

To disable auto-pairs altogether, set auto-pairs to false:

[editor]
auto-pairs = false # defaults to `true`

The default pairs are (){}[]''""`</code>, but these can be customized by settingauto-pairs` to a TOML table:

[editor.auto-pairs]
'(' = ')'
'{' = '}'
'[' = ']'
'"' = '"'
'`' = '`'
'<' = '>'

Additionally, this setting can be used in a language config. Unless the editor setting is false, this will override the editor config in documents with this language.

Example languages.toml that adds <> and removes ''

[[language]]
name = "rust"

[language.auto-pairs]
'(' = ')'
'{' = '}'
'[' = ']'
'"' = '"'
'`' = '`'
'<' = '>'

[editor.search] Section

Search specific options.

Key Description Default
smart-case Enable smart case regex searching (case insensitive unless pattern contains upper case characters) true
wrap-around Whether the search should wrap after depleting the matches true

[editor.whitespace] Section

Options for rendering whitespace with visible characters. Use :set whitespace.render all to temporarily enable visible whitespace.

Key Description Default
render Whether to render whitespace. May either be "all" or "none", or a table with sub-keys space, nbsp, tab, and newline. "none"
characters Literal characters to use when rendering whitespace. Sub-keys may be any of tab, space, nbsp, newline or tabpad See example below

Example

[editor.whitespace]
render = "all"
# or control each character
[editor.whitespace.render]
space = "all"
tab = "all"
newline = "none"

[editor.whitespace.characters]
space = "·"
nbsp = "⍽"
tab = "→"
newline = "⏎"
tabpad = "·" # Tabs will look like "→···" (depending on tab width)

[editor.indent-guides] Section

Options for rendering vertical indent guides.

Key Description Default
render Whether to render indent guides. false
character Literal character to use for rendering the indent guide │
skip-levels Number of indent levels to skip 0

Example:

[editor.indent-guides]
render = true
character = "╎" # Some characters that work well: "▏", "┆", "┊", "⸽"
skip-levels = 1

[editor.gutters] Section

For simplicity, editor.gutters accepts an array of gutter types, which will use default settings for all gutter components.

[editor]
gutters = ["diff", "diagnostics", "line-numbers", "spacer"]

To customize the behavior of gutters, the [editor.gutters] section must be used. This section contains top level settings, as well as settings for specific gutter components as sub-sections.

Key Description Default
layout A vector of gutters to display ["diagnostics", "spacer", "line-numbers", "spacer", "diff"]

Example:

[editor.gutters]
layout = ["diff", "diagnostics", "line-numbers", "spacer"]

[editor.gutters.line-numbers] Section

Options for the line number gutter

Key Description Default
min-width The minimum number of characters to use 3

Example:

[editor.gutters.line-numbers]
min-width = 1

[editor.gutters.diagnotics] Section

Currently unused

[editor.gutters.diff] Section

Currently unused

[editor.gutters.spacer] Section

Currently unused

[editor.soft-wrap] Section

Options for soft wrapping lines that exceed the view width

Key Description Default
enable Whether soft wrapping is enabled. false
max-wrap Maximum free space left at the end of the line. 20
max-indent-retain Maximum indentation to carry over when soft wrapping a line. 40
wrap-indicator Text inserted before soft wrapped lines, highlighted with ui.virtual.wrap ↪

Example:

[editor.soft-wrap]
enable = true
max-wrap = 25 # increase value to reduce forced mid-word wrapping
max-indent-retain = 0
wrap-indicator = ""  # set wrap-indicator to "" to hide it