Struct KeymapHandle 

pub struct KeymapHandle { /* private fields */ }

Editor-facing handle to the keymap registry.

Reads are wait-free. Self::lookup does one ArcSwap::load + one trie walk. The keystroke path holds the returned Arc<MergedKeymap> only for the duration of the lookup; concurrent writes (mode push/pop, user :bind, plugin registration) cannot stall it.

Writes are mutex-routed. Self::bind / Self::unbind / Self::push_layer / Self::pop_layer take a brief mutex on the layer stack, mutate the affected per-mode tries, rebuild the merged cell, and ArcSwap::store it. Writes are infrequent (startup; mode transitions; user commands), so the lock is uncontended in practice.

Implementations

impl KeymapHandle

pub fn new() -> Self

A handle on a fresh, empty KeymapRegistry. Clone the handle to share the registry; a second new() is an unrelated registry.

pub fn reverse_entries(&self, id: CommandId) -> Vec<(KeyChord, KeymapLayer)>

Reverse-lookup entries for id: the chord sequence that fires it, each chord paired with the layer providing the binding. Empty when nothing binds id. Freshens the derived state first.

Coverage is deliberately narrow (it feeds the : completion margin): Normal mode only, literal-only paths (a binding through a {char} wildcard is skipped), and first binding wins when several chords bind the same command. Both the always-on layers and every gated mode layer are indexed.

(C′) Prefer this over Self::reverse_cache_arc: a raw handle on the ArcSwap bypasses the registry’s lazy derived-state refresh and can read a cache that a pending bind has invalidated. Cold path (the command palette and the completion margin’s keybinding column), so paying a rebuild here is free where paying it per write was not.

pub fn reverse_cache_arc( &self, ) -> Arc<ArcSwap<HashMap<CommandId, Vec<(KeyChord, KeymapLayer)>>>>

The raw reverse-cache cell behind Self::reverse_entries.

Exists for lattice-host, which builds a KeymapReverseLookupHandle from it: lattice-keymap cannot depend on lattice-completion (circular dependency), so that type lives downstream and takes the cache through this accessor. Reads through it skip the lazy derived-state refresh, so they can lag a bind until the next lookup-style call freshens it.

pub fn lookup(&self, mode: BindingMode, chords: &[KeyChord]) -> LookupResult

Look up the typed binding for chords in mode. Wait-free.

K.1.c (2026-05-30): preserves pre-K.1.c semantics by treating every registered mode layer — major and minor — as active (overlaid in ModeId-alphabetical order, matching K.1.b’s sorted-layers-vec merge order). Legacy callers (the translate dispatcher’s completion-popup / snippet keystroke path) continue to work unchanged — their mode lifecycle already gates at push/pop, so “everything always active” matches the push/pop surface.

For per-buffer-gated lookup (the emacs-style composability story — do in diff-mode only fires when the active buffer has diff-mode active) use Self::lookup_with_context with the buffer’s active_modes. D.5 wires diff-mode through that path; other modes migrate as their consumers care.

pub fn lookup_with_context( &self, mode: BindingMode, chords: &[KeyChord], active_modes: &[ModeId], ) -> LookupResult

K.1.c (2026-05-30): mode-aware lookup.

Composes a fresh per-keystroke merged trie:

1. Start with the cached always-on merge (Builtin + User + Buffer).
2. For each mode_id in active_modes (in slice order — callers pass the active major first, then minors in activation order) overlay that mode’s MajorMode / MinorMode layer on top — later entries win, so a minor beats the major and the last-activated minor wins.
3. Note: the always-on cache already has User / Buffer overlaid above Builtin. The minor-mode overlay applied in step 2 therefore sits above User/Buffer at lookup time — which differs from the pre-K.1.c “MinorMode < User < Buffer” priority. Rationale: mode-scoped chords (do in diff-mode, M-d in corfu-popupinfo-map) intentionally claim their chord while the mode is active, even over the user’s global rebinds; users wanting to override a specific mode’s binding use the OwnedLayer { mode_id } capability to bind inside that mode’s layer (where same-layer last-write-wins applies). This matches emacs’s minor-mode-precedence-over-global semantics.

Wait-free reads: two ArcSwap::load calls (merged, gated_mode_tries) + per-active_modes merge work. Typical active_modes.len() is 0-3 so the overhead is small; with an empty slice no composite is built at all. A ModeId with no registered layer is skipped.

Examples

use lattice_grammar::{CommandId, CommandInvocation, SourceLocation};
use lattice_keymap::{BindingMode, ChordPattern, KeymapHandle, KeymapLayer, LookupResult, ModeId};
use lattice_protocol::KeyChord;

let keymap = KeymapHandle::new();
let path = [ChordPattern::Literal(KeyChord::char('g')), ChordPattern::Literal(KeyChord::char('d'))];
keymap.bind(KeymapLayer::MajorMode(ModeId::new("rust-mode")), BindingMode::Normal, &path,
    CommandInvocation::of(CommandId::new(9)), SourceLocation::synthetic("doc"));

let rust = [ModeId::new("rust-mode")];
let g = KeyChord::char('g');
assert!(matches!(keymap.lookup_with_context(BindingMode::Normal, &[g], &rust), LookupResult::Partial));
assert!(matches!(
    keymap.lookup_with_context(BindingMode::Normal, &[g, KeyChord::char('d')], &rust),
    LookupResult::Bound { .. },
));
// Not this buffer's major: the layer is invisible.
assert!(matches!(keymap.lookup_with_context(BindingMode::Normal, &[g], &[]), LookupResult::Unbound));

pub fn continuations_with_context( &self, mode: BindingMode, chords: &[KeyChord], active_modes: &[ModeId], ) -> Option<NodeView>

WK.1: the immediate continuations of chords in the same composite Self::lookup_with_context resolves against.

This is which-key’s source of truth, and design §2 makes it the feature’s one correctness property: the popup is derived from the trie the dispatcher walks, never from the static catalog. Both halves of this function mirror lookup_with_context exactly — the same always-on fast path, the same overlay order — and differ only in the terminal step, where that one resolves a binding and this one reports a node’s children. Any other construction reintroduces the :describe-bindings bug (a mode that shadows a builtin chord not reflected, so the view advertises a binding that will not fire) in a more visible place.

Not Self::continuations, which is :describe-key’s query: activation-agnostic, all-layers, one row per registration. That one answers “does this chord exist anywhere”; this one answers “what can I press next, here”. Same trie, opposite contexts.

None when the prefix leaves the trie. Telemetry path — runs on the actor thread after the idle delay, never per keystroke.

pub fn bind( &self, layer: KeymapLayer, mode: BindingMode, path: &[ChordPattern], command: CommandInvocation, source: SourceLocation, )

Register a binding at (layer, mode, path). Replaces any prior binding at the exact same triple within the same layer (last-bind-wins per layer); higher-priority layers shadow lower-priority ones automatically via the merged-trie rebuild.

pub fn bind_modes( &self, layer: KeymapLayer, modes: &[BindingMode], path: &[ChordPattern], command: CommandInvocation, source: SourceLocation, )

Register one binding across SEVERAL modes in a single call. Equivalent to calling Self::bind once per mode, but inserts into every mode’s trie under one lock and rebuilds the merged trie + reverse cache ONCE (not per mode). The same Arc<BoundCommand> is shared across the modes’ tries, except that a Visual or Select entry named alongside Normal gets its own copy: it’s an explicit declaration, and the motion mirror tells its own rows apart by identity (VM.4).

This is the imperative multi-mode primitive init.rs / plugins / host helpers use directly (the declarative peer is crate::Keymap::bind_chord_modes and the keymap_entry! mode: [..] form). modes must be non-empty; an empty slice is a no-op.

pub fn bind_bound( &self, layer: KeymapLayer, mode: BindingMode, path: &[ChordPattern], bound: Arc<BoundCommand>, )

Lower-level binder: register a pre-built Arc<BoundCommand> directly, e.g. one built with BoundCommand::with_fall_through or shared across several paths. Used by the per-mode registration helpers (lattice_ui_tui::keymap_replace::register_replace_bindings and siblings). Self::bind is this plus BoundCommand::from_invocation.

Same semantics as Self::bind: last write wins at the exact (layer, mode, path); with a command registry set, a Normal-mode motion is mirrored into Visual (and Select when its first chord cannot be typed). The binding’s own layer field is not consulted — layer decides where it goes.

pub fn unbind( &self, layer: KeymapLayer, mode: BindingMode, path: &[ChordPattern], ) -> Option<Arc<BoundCommand>>

Remove the binding at (layer, mode, path). No-op if nothing was registered there. Returns the dropped binding so callers can echo provenance (“unbound dd from user, init.rs:42”).

pub fn push_layer( &self, kind: PushLayerKind, label: impl Into<String>, bindings: HashMap<BindingMode, KeymapTrie>, ) -> LayerId

Install a minor-mode or buffer layer.

K.1.b (2026-05-30): for PushLayerKind::MinorMode(mode_id), the layer’s identity is the mode_id — pushing for the same mode_id is idempotent on the layer: the existing layer’s bindings are replaced, no sibling layer is minted. The same holds for MajorMode(mode_id) and for Buffer: the registry finds an existing layer by its KeymapLayer key, so a second Buffer push replaces the first’s bindings and returns the same LayerId.

A replacing push also replaces the layer’s label, and discards any bindings previously added to that layer with Self::bind.

bindings is the layer’s full per-mode binding set – computed by the caller (e.g. completion-popup wires its overrides at activation time). The registry copies the tries in; the caller’s KeymapTrie instances are no longer needed after the call returns.

Returns the LayerId of the installed layer (whether freshly minted or pre-existing for the same mode_id). For MinorMode, prefer popping via Self::pop_minor_mode_layer (by mode_id) over Self::pop_layer (by LayerId); both work but the former is what matches the install signature.

pub fn pop_layer(&self, id: LayerId)

Pop the layer issued by an earlier push_layer. No-op if the id is unknown (caller may double-pop on the way out of an error path; defensive).

pub fn remove_layer(&self, layer: KeymapLayer)

Remove an entire layer by its KeymapLayer identity, dropping every binding it holds across all binding-modes, then rebuild the merged / gated / reverse caches. The teardown seam for a plugin mode’s keymap (PH7.12b): lattice-plugin-host’s bind_mode_keymap binds a plugin mode’s chords into KeymapLayer::MinorMode(mode_id) via Self::try_bind_chord_string — an implicitly-created layer, so the host never holds a LayerId to pop_layer with. This removes it by the layer key the host does know (the mode’s own MinorMode(mode_id)). No-op if no such layer exists (idempotent second unload / a mode that bound nothing). Mirrors pop_layer’s rebuild exactly — every site that stores merged / gated_mode_tries must also rebuild the reverse cache.

pub fn set_command_registry(&self, commands: CommandRegistryHandle)

VM.4: give the keymap the command registry it asks “is this a motion?”.

From here on every write mirrors motions into Visual, and into Select when their first chord can’t be typed (keymap-architecture.md §15). Rescans every existing layer, so calling this after bindings have landed is exactly as good as calling it first. Boot calls it the moment the handle exists.

pub fn layers(&self) -> Vec<KeymapLayer>

VM.4: every registered layer, lowest priority first.

Exists so an invariant can be asserted across ALL layers rather than the one a test happens to name. The “a motion is live in Visual” drift test used to check Builtin only, so it could never have noticed a re-pushed mode layer losing its mirror.

pub fn binding_count(&self) -> usize

Total binding count across all layers. Telemetry + tests; not on the hot path.

pub fn enumerate_chord_bindings( &self, mode: BindingMode, chords: &[KeyChord], ) -> Vec<(KeymapLayer, Arc<BoundCommand>)>

K.1.d (2026-05-30): enumerate every binding registered for chords in mode across all layers, returning the layer + binding pair for each. Telemetry path (drives :describe-key‘s mode-aware section); not on the keystroke hot path. Order: layer-priority ascending (Builtin first, then MajorMode, then MinorMode layers in ModeId-alphabetical order, then User, then Buffer). Callers cross-reference the layers’ MinorMode entries against the active buffer’s ActiveModes to mark which would actually fire right now.

pub fn resolve_trace( &self, mode: BindingMode, chords: &[KeyChord], active_modes: &[ModeId], ) -> KeymapResolution

Full per-layer trace for chords in mode.

Returns a KeymapResolution whose hits list every registered layer that has a terminal binding at the given chord path, in priority order ascending (Builtin first, Buffer last). The active flag on each hit is set by crossing the layer against active_modes:

• Builtin, User, Buffer are always active.
• MajorMode(id) and MinorMode(id) are active iff id is contained in active_modes.

Telemetry path; not on the keystroke hot path.

pub fn resolve_trace_all_modes( &self, chords: &[KeyChord], active_modes: &[ModeId], ) -> Vec<KeymapResolution>

Run Self::resolve_trace for every BindingMode variant.

Returns only the modes that have at least one registered binding for chords (i.e. non-empty hits). Callers that want to display :describe-key with all modes iterate the returned vec; modes with no bindings are omitted to keep output compact.

Telemetry path; not on the keystroke hot path.

pub fn any_layer_expects_more(&self, chords: &[KeyChord]) -> bool

Is chords still an INCOMPLETE prefix of some REGISTERED binding — in any binding mode, in any layer, active here or not?

This is the question that lets :describe-key’s chord capture end a sequence without reserving a terminator key. A chord argument is a sequence (gg, <C-w>v, <leader>fz), so capture cannot submit on the first keystroke; but the trie already distinguishes “waiting for more” from “this is the answer” on every keystroke of ordinary dispatch, and that is exactly the distinction capture needs. Asking here is what frees <CR> / <Esc> / <BS> to be describable keys rather than controls.

Any LAYER, not the active ones (DK.4). This deliberately does not take an active_modes slice, and the omission is the fix for a user-reported truncation: capture runs while the *command-line* buffer is focused, so an activation-gated query resolves against the MINIBUFFER’s modes — which are never the org / magit / plugin modes whose chords the user is asking about. <C-c><C-x><C-b> submitted after two chords and described <C-c><C-x>, because org-mode’s MajorMode layer was invisible to the question. No multi-chord binding owned by a major mode or a plugin could be captured at all.

The rule that replaces it: :describe-key answers for EVERY key, not only the keys active where you stand — so capture keeps reading while any registered binding anywhere could extend the sequence, and the rendered answer marks each layer [active] / [inactive] for the buffer the prompt was opened from. Sequence SHAPE is a property of the keymap; what FIRES is a property of the buffer. Only the second one is contextual.

Any mode, not the current one, for the same reason: an Insert-mode-only prefix must not submit early mid-sequence.

Unbound deliberately terminates. “This key does nothing” is a first- class answer — it is the one a user asking why <M-k> did nothing needs — and treating it as “keep waiting” would hang capture on exactly the query that motivated it. A chord that is BOUND at this depth also terminates, matching dispatch: the trie stops at the first binding, so anything grown beneath it can never fire (the continuations are still listed in the answer, flagged as unreachable).

Telemetry path; not on the keystroke hot path.

pub fn continuations( &self, chords: &[KeyChord], active_modes: &[ModeId], ) -> Vec<Continuation>

DK.4: every binding registered strictly BELOW chords, across all layers and all binding modes, annotated with whether its layer is active on the buffer described by active_modes.

The prefix half of “:describe-key answers for every key”. A prefix has no binding of its own, so the layer trace is empty and the honest answer is its subtree: what can follow, what each continuation runs, and which of them can fire here.

Results are sorted by binding mode (declaration order), then by rendered chord suffix, so the output is stable across runs. Continuations whose path crosses a CharLiteral wildcard (f{char}, '{mark}) are included with the wildcard rendered as {char}.

Telemetry path; not on the keystroke hot path.

pub fn layer_label_string(&self, layer: KeymapLayer) -> String

Human-readable label for a KeymapLayer, derived from the layer’s registered label string (set at push_layer / bind time). Falls back to default_label when the layer hasn’t been explicitly named. Used by :describe-key output.

pub fn layer_label(&self, id: LayerId) -> Option<String>

Human-readable label for the layer carrying id, if any. Drives :describe-key’s provenance row (“user, init.rs:42”; “minor-mode:completion-popup”). Telemetry path; not on the hot path.

pub fn try_bind( &self, capability: KeymapCapability, layer: KeymapLayer, mode: BindingMode, path: &[ChordPattern], command: CommandInvocation, source: SourceLocation, ) -> Result<(), KeymapError>

Capability-gated Self::bind. The host hands every caller a KeymapCapability derived from its manifest; this entry point checks the capability before committing the write so plugins / init.rs can’t escape their declared scope.

Scope: Full → any layer; User → User only; MinorMode → any MinorMode(_) or Buffer; OwnedLayer { mode_id } → that mode’s own MinorMode(mode_id) or MajorMode(mode_id).

Errors

KeymapError::CapabilityDenied when the capability does not cover layer; nothing is written.

pub fn try_bind_chord_string( &self, capability: KeymapCapability, layer: KeymapLayer, mode: BindingMode, chord_str: &str, command: CommandInvocation, source: SourceLocation, ) -> Result<(), KeymapError>

Capability-gated convenience that parses chord_str ("<leader>w", "gd", "<C-w>j") into a Vec<ChordPattern::Literal> before delegating to Self::try_bind. The host’s WIT bind host-fn calls this; user init.rs calls a thin wrapper around it.

chord_str must round-trip through [lattice_protocol::chord::parse_chord_sequence]; wildcards (<CharLiteral>) aren’t expressible from chord strings today and require Self::try_bind with a hand-built &[ChordPattern]. <leader> / <Leader> is expanded first against Self::leader.

Errors

KeymapError::InvalidChord when the (leader-expanded) string does not parse; otherwise as Self::try_bind. The chord is parsed before the capability is checked.

Examples

use lattice_grammar::{CommandId, CommandInvocation, SourceLocation};
use lattice_keymap::{BindingMode, KeymapCapability, KeymapError, KeymapHandle, KeymapLayer, LookupResult};
use lattice_protocol::KeyChord;

let keymap = KeymapHandle::new();
keymap.set_leader(",");
let cmd = CommandInvocation::of(CommandId::new(3));
keymap.try_bind_chord_string(KeymapCapability::User, KeymapLayer::User, BindingMode::Normal,
    "<leader>w", cmd.clone(), SourceLocation::synthetic("init.rs")).unwrap();

let hit = keymap.lookup(BindingMode::Normal, &[KeyChord::char(','), KeyChord::char('w')]);
assert!(matches!(hit, LookupResult::Bound { command, .. } if command.command == cmd));

let bad = keymap.try_bind_chord_string(KeymapCapability::User, KeymapLayer::User,
    BindingMode::Normal, "<Nope>", cmd, SourceLocation::synthetic("init.rs"));
assert!(matches!(bad, Err(KeymapError::InvalidChord(_))));

pub fn layer_bindings( &self, layer: KeymapLayer, mode: BindingMode, ) -> Vec<(Vec<ChordPattern>, Arc<BoundCommand>)>

OM.4b: every terminal binding in ONE layer’s mode trie, as (chord path, bound command) pairs.

The existing walks are either global (merged, every layer folded together) or per-CommandId (the reverse cache). Neither answers “what did this layer bind”, which is what a caller expanding a mode’s contributions needs: the chord comes from the layer, the command’s kind comes from the CommandRegistry, and only the pairing identifies e.g. a text object that needs operator-pending rows generating.

Snapshots into a Vec rather than lending an iterator, because the caller’s next move is to write bindings into the same registry and it must not be holding the lock while doing so. O(bindings in one layer), off any hot path — this runs at plugin load, not per keystroke.

pub fn leader(&self) -> Arc<String>

OM.2b: the chord <leader> expands to at bind time.

pub fn set_leader(&self, leader: &str)

Set what <leader> expands to. The host calls this at boot from the keymap.leader option, BEFORE any subsystem or plugin registers its bindings — expansion is bind-time, so a leader set afterwards does not move bindings that already landed.

pub fn expand_leader(&self, chord_str: &str) -> String

Expand <leader> in chord_str against the current leader. Exposed so a caller that must parse a binding string itself (:describe-key) resolves it the same way binding did.

pub fn try_unbind_chord_string( &self, capability: KeymapCapability, layer: KeymapLayer, mode: BindingMode, chord_str: &str, ) -> Result<Option<Arc<BoundCommand>>, KeymapError>

Capability-gated Self::unbind from a vim-notation chord string — the symmetric counterpart to try_bind_chord_string, so a caller that bound by string (a plugin’s register-binding, PL8.D) can reverse it by the same string on unload without re-parsing to ChordPatterns itself. An unparseable chord is KeymapError::InvalidChord; a capability denial is KeymapError::CapabilityDenied; Ok(None) means the path wasn’t bound (idempotent re-unbind).

pub fn try_unbind( &self, capability: KeymapCapability, layer: KeymapLayer, mode: BindingMode, path: &[ChordPattern], ) -> Result<Option<Arc<BoundCommand>>, KeymapError>

Capability-gated Self::unbind. Returns the dropped binding (or None when the path wasn’t bound) so the host can echo “unbound dd (was: delete-line)”.

pub fn try_push_layer( &self, capability: KeymapCapability, kind: PushLayerKind, label: impl Into<String>, bindings: HashMap<BindingMode, KeymapTrie>, ) -> Result<LayerId, KeymapError>

Capability-gated Self::push_layer. Permitted for every capability except User, whatever kind names: MinorMode and OwnedLayer { mode_id } are NOT checked against the pushed layer’s kind or mode id here, unlike Self::try_bind. The User capability can’t push runtime layers – user config writes live in the static User layer registered at boot.

Errors

KeymapError::CapabilityDenied for User, naming the layer the push would have created.

pub fn pop_minor_mode_layer(&self, mode_id: ModeId) -> bool

K.1.b (2026-05-30): pop a minor-mode layer by its ModeId. The natural complement to push_layer(PushLayerKind::MinorMode(mode_id), …) — callers don’t have to thread a separate LayerId through teardown when the mode id is what they already know. No-op if no layer for mode_id is currently installed (defensive against double-pop on error paths). Returns true iff a layer was removed.

Trait Implementations

impl Clone for KeymapHandle

fn clone(&self) -> KeymapHandle

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for KeymapHandle

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for KeymapHandle

fn default() -> Self

Returns the “default value” for a type.