Struct MotionContext 

pub struct MotionContext<'a> {

    pub buffer: &'a Buffer,
    pub buffer_id: BufferId,
    pub from: Position,
    pub count: Count,
    pub has_explicit_count: bool,
    pub args: Args,
    pub cancel: &'a CancellationToken,
    pub scope_resolver: Option<&'a dyn ScopeResolver>,
    pub path: Option<&'a Path>,
    pub syntax: Option<&'a Arc<dyn Any + Send + Sync>>,
    pub last_find: Option<LastFind>,
    pub fold_resolver: Option<&'a dyn FoldResolver>,
    pub last_search: Option<&'a LastSearch>,
    pub marks: Option<&'a dyn MarkResolver>,
    pub viewport: Option<&'a dyn ViewportResolver>,
    pub nostartofline: bool,
    pub curswant: Option<Curswant>,
    pub display: Option<&'a dyn DisplayResolver>,
    pub scrolloff: u32,
    pub operator_pending: bool,
}

Context passed to a motion’s evaluator.

M.2.b.0.A (2026-05-31): buffer_id carries the active buffer’s registry identity through to motion handlers. Built- in motions (purely content-based: w / e / ]p / etc.) ignore it; kind-specific motions (multibuffer ]e / [e / ]E / [E, future file-tree / oil structural motions, future plugin-defined kinds) use it to look up the active major mode’s typed state through a service registry their handler closure captures at registration time. Adding it here keeps the grammar layer free of lattice-mode / ServiceRegistry coupling — the handler decides what to look up.

Fields

buffer: &'a Buffer

The buffer text the motion reads. Motions never edit.

buffer_id: BufferId

Registry-level identity of the active buffer this motion is firing against. Distinct from lattice_protocol::ids:: DocumentId (per-actor stable id); BufferId is the registry key that mode-state lookups use.

from: Position

Where the motion starts: the cursor, or the Visual head.

count: Count

The count, 1 when none was typed; see Self::has_explicit_count.

has_explicit_count: bool

True when the invocation carried an explicit count (e.g. 5G). False for bare invocations (G alone). Motions whose semantic changes with an explicit count (goto-last- line: last vs. specific line) use this to disambiguate.

args: Args

The motion’s own arguments, e.g. Args::Char for f{char} or a mark name for 'x.

cancel: &'a CancellationToken

Cooperative cancellation handle (DESIGN.md §5.2.5). Hot loops should poll cancel.check()? on each iteration; on a flipped token the evaluator returns crate::CommandError::Cancelled and the dispatcher commits no effect.

scope_resolver: Option<&'a dyn ScopeResolver>

N.1.4-motions: the active buffer’s tree-sitter resolver for structural motions (]f/[c/…). None on Plain buffers with no parse — the motion then no-ops. Threaded by the host, identical to TextObjectContext.

path: Option<&'a Path>

OM.6b: the file the motion’s buffer is backed by, so a plugin motion’s document handle can answer path(). A borrow — this context is already borrowing, so carrying it costs nothing on the keystroke path (motions fire on every j). None for a buffer with no file.

syntax: Option<&'a Arc<dyn Any + Send + Sync>>

OT.1: the same type-erased tree-sitter snapshot ActionContext::syntax carries, so a plugin motion can resolve structurally instead of scanning text. Copied straight from GrammarEnv::syntax, which the host has always threaded here — until OT.1 motions simply did not read it.

Borrowed, not cloned, unlike the owned ActionContext peer: motions fire on every j, so a native motion (which ignores this) must pay nothing, and only a plugin motion that actually mints a tree-snapshot resource pays the Arc bump. Same reasoning as path above.

Acquired the same instant as buffer, so tree and text versions agree (plugin-treesitter-seam.md §7). None when the buffer has no parse.

last_find: Option<LastFind>

VM.3c: the last f / F / t / T, copied from GrammarEnv::last_find. Read by motion:find-repeat and its reverse; every other motion ignores it. Copy, so carrying it costs nothing on the keystroke path.

fold_resolver: Option<&'a dyn FoldResolver>

VM.3i: the fold edges zj / zk step between, copied from GrammarEnv::fold_resolver. Borrowed, so a motion that ignores it pays nothing.

last_search: Option<&'a LastSearch>

VM.3d-2: the search n / N / * / # repeat, copied from GrammarEnv::last_search. Borrowed; every other motion ignores it.

marks: Option<&'a dyn MarkResolver>

VM.3e: the marks 'x / `x jump to, copied from GrammarEnv::marks. Borrowed; every other motion ignores it.

viewport: Option<&'a dyn ViewportResolver>

VM.3f: the window’s lines for H / M / L, copied from GrammarEnv::viewport.

nostartofline: bool

VM.3f: vim’s nostartofline — H / M / L keep the cursor’s column instead of landing on the first non-blank.

curswant: Option<Curswant>

VM.3g-1: the goal column, copied from GrammarEnv::curswant.

display: Option<&'a dyn DisplayResolver>

VM.3g-2: the display geometry gj / gk / g0 / g$ read.

scrolloff: u32

VM.3f: see GrammarEnv::scrolloff.

operator_pending: bool

VM.3f: whether this motion is resolving an OPERATOR’s target.

H / L are adjusted for scrolloff “unless an operator is pending” (:h H), so dH reaches the window’s real top edge while a bare H stops at the margin. Checked in vim 9.2.