Struct DefaultHost 

pub struct DefaultHost { /* private fields */ }

Default no-op Host implementation. Suitable for tests, headless embedding, or any host that doesn’t yet need clipboard / cursor-shape / cancellation plumbing.

Behaviour:

• write_clipboard stores the most recent payload in an in-memory slot; read_clipboard returns it. Round-trip-only — no OS-level clipboard touched.
• now returns wall-clock duration since construction.
• prompt_search returns None (search is aborted).
• emit_cursor_shape records the most recent shape; readable via DefaultHost::last_cursor_shape.
• emit_intent discards intents (intent type is ()).

Implementations

impl DefaultHost

pub const DEFAULT_VIEWPORT: Viewport

Default viewport size for headless / test hosts: 80x24, no soft-wrap. Matches the conventional terminal default.

pub fn new() -> Self

pub fn with_viewport(viewport: Viewport) -> Self

Construct a DefaultHost with a custom initial viewport. Useful for tests that want to exercise scrolloff math at a specific window size.

pub fn last_cursor_shape(&self) -> CursorShape

Most recent cursor shape requested by the engine.

Trait Implementations

impl Debug for DefaultHost

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

Formats the value using the given formatter.

impl Default for DefaultHost

fn default() -> Self

Returns the “default value” for a type.

impl Host for DefaultHost

type Intent = ()

Custom intent type. Hosts that don’t fan out actions back to themselves can use the unit type via the default impl approach (set associated type explicitly).

fn write_clipboard(&mut self, text: String)

Fire-and-forget clipboard write. Engine never blocks; the host queues internally and flushes on its own task (OSC52, wl-copy, pbcopy, …).

fn read_clipboard(&mut self) -> Option<String>

Returns the last-known cached clipboard value. May be stale — matches the OSC52/wl-paste model neovim and helix both ship.

fn now(&self) -> Duration

Monotonic time. Multi-key timeout (timeoutlen) resolution reads this; engine never reads Instant::now() directly so macro replay stays deterministic.

fn prompt_search(&mut self) -> Option<String>

Synchronously prompt the user for a search pattern. Returning None aborts the search.

fn emit_cursor_shape(&mut self, shape: CursorShape)

Engine emits this on every mode transition. Hosts repaint the cursor in the requested shape.

fn viewport(&self) -> &Viewport

Borrow the host’s viewport. The host writes width/height/ text_width/wrap per render frame; the engine reads/writes top_row / top_col to scroll. 0.0.34 (Patch C-δ.1) moved this off hjkl_buffer::Buffer onto Host.

fn viewport_mut(&mut self) -> &mut Viewport

Mutable viewport access. Engine motion + scroll code routes here when scrolloff math advances top_row.

fn emit_intent(&mut self, _intent: Self::Intent)

Host-defined event the engine raises (LSP request, fold op, buffer switch, …).

fn should_cancel(&self) -> bool

Cooperative cancellation. Engine polls during long search / regex / multi-cursor edit loops. Default returns false.

fn display_line_for(&self, pos: Pos) -> u32

Map a logical position to its display line for gj/gk. Hosts without wrapping may use the default identity impl.

fn pos_for_display(&self, line: u32, col: u32) -> Pos

Inverse of [display_line_for]. Default identity.

fn syntax_highlights(&self, range: Range<Pos>) -> Vec<Highlight>

Host-supplied syntax highlights for range. Empty by default; hosts wire tree-sitter or LSP semantic tokens here.