Help system

Lattice is self-documenting. Every command, option, mode, event, and key binding carries metadata that the help system surfaces on demand. No internet connection; no man pages; no searching the source. The answer is in the editor.

Quick reference

The <C-h> prefix is available in Normal mode only — the same scope vim uses for the help key. In Insert mode <C-h> is backspace (vim convention); in Command and Search it clears the preceding character.

:describe-key — what does a chord do?

:describe-key CHORD
:describe-key MODEPREFIX_CHORD

Shows every layer that has a binding for CHORD, marks which layer fires under the current buffer's active modes, and links to the source location where the binding was declared.

Mode-prefix syntax

By default :describe-key queries all binding modes at once. To narrow to one mode, prefix the chord with a two-character mode tag followed by _:

Without a prefix, all modes that have a binding for the chord are shown; modes with no binding are omitted to keep the output compact.

:describe-key j          -- shows Normal, Visual, and Replace hits
:describe-key n_j        -- shows Normal hits only
:describe-key i_<C-n>    -- shows the Insert completion-trigger
:describe-key v_>        -- shows what > does in Visual mode

The mode prefix follows the same convention as Neovim's :map commands (nnoremap, inoremap, etc.) — n_ for normal, i_ for insert — so muscle memory transfers.

Output format

j — 3 registration(s) across 3 mode(s):

[Normal mode]
  -> motion:line-down  (fires now)
     layer: Built-in
     source: crates/lattice-host/src/keymap_normal.rs:1620

[Visual mode]
  -> motion:line-down  (fires now)
     layer: Built-in

[Replace mode]
  -> action:overwrite-char  (fires now)
     layer: Built-in

(fires now) marks the binding that would actually execute given the current buffer's active modes. A hit marked (registered but not active) exists in the registry but is shadowed or gated by an inactive minor mode.

The layer field shows which layer the binding lives in: Built-in (the default vim keymap), User config (your init.rs), Major mode: rust (a language-mode contribution), or Minor mode: lsp-mode (a minor-mode contribution). Higher-priority layers shadow lower ones; :describe-key shows the full stack so you can see both the winner and what it shadows.

Source links are live: pressing <CR> on a source line opens the file at that line in a new split.

Via the <C-h> map

In Normal mode, press <C-h> k — a prompt appears. Type the chord you want to describe (with optional mode prefix) and press <Enter>.

:describe-command — metadata for a command

:describe-command NAME

Shows the command's documentation string, argument spec, aliases, current keybindings (every chord bound to it, across all modes), source location, and links to related help topics.

Aliases resolve correctly: :describe-command write and :describe-command w both resolve to ex:write.

Via <C-h>: <C-h> c prompts for a command name with completion.

:describe-option — option documentation

:describe-option NAME

Shows the option's type, current value, default, resolver chain (which layer set it: TOML / :set / mode override / built-in default), and a human-readable description.

Via <C-h>: <C-h> o.

See also :options for an interactive listing of all options with in-place editing (the emacs M-x customize equivalent).

:describe-event — event payload and subscribers

:describe-event NAME

Shows the event's payload type, when it fires, and the list of current subscribers: autocmds, mode lifecycle hooks, plugin hooks. Useful when writing plugins or autocmds and you want to know what fires on a given trigger.

Via <C-h>: <C-h> e.

:describe-mode — the active mode stack

:describe-mode [NAME]

Without an argument: shows the major mode and all active minor modes on the current buffer — name, version, brief description, contributed keybindings, and whether each minor mode is currently active.

With a name: describes that mode whether or not it is active on the current buffer.

Via <C-h>: <C-h> m.

:describe-buffer — buffer metadata

:describe-buffer

Shows the current buffer's ID, kind (Document / Multibuffer / Terminal / Help / …), flags (listed, hidden, modified, read-only), the file path if any, and the full mode stack.

Via <C-h>: <C-h> b.

:apropos — search across everything

:apropos PATTERN

Pattern-matches against command names, option names, event names, mode names, and help topic summaries in a single sweep. Results open in a help buffer with cross-links. Use this when you know what you want to do but not what it is called.

Via <C-h>: <C-h> a.

Examples:

:apropos lsp          -- everything LSP-related
:apropos search       -- search commands, options, and events
:apropos fold         -- fold-related surface
:apropos completion   -- completion triggers and options

:keymap — the full chord table

:keymap [MODE]

Opens a buffer showing the complete chord table for the current state, or for the specified mode. Grouped by layer: Built-in, User config, each active major/minor mode contribution. Each row links to its source via <CR>.

Via <C-h>: <C-h> K (capital K — lowercase k is :describe-key).

:help — topic documentation

:help [TOPIC]
:help-for-help

Opens the named topic as a help buffer. <Tab> after :help lists all registered topics with their summaries. Without an argument, opens the topic index.

:help-for-help (also <C-h> <C-h> or <C-h> ?) opens this page.

Help buffer navigation

Inside any help buffer:

Three link kinds exist in help buffers:

• Topic links (help:modal-editing) — jump to another topic
• Source links (file:line pairs from :describe-*) — open the source in a split
• Chord links (chord notation) — run :describe-key for that chord

Inline help at the command line

At the : command line, press <C-h> while the cursor is on a partially-typed command name to open :describe-command for it inline. This gives you documentation without losing your place in the command you are building.

See also

• modal-editing — the vim grammar; mode entry/exit; registers, marks, macros.
• modes — major + minor modes; how modes contribute keymaps and what each mode offers.
• options — :set, :customize, TOML config.
• ex-commands — the full : command reference.