Struct UiLiveness 

pub struct UiLiveness {
    probe_sent: Option<(u64, Instant)>,
    last_alive: Option<Instant>,
    consecutive_misses: u32,
}

Fields

probe_sent: Option<(u64, Instant)>

Most recent probe: (nonce, when sent). One outstanding probe at a time is enough at the Phase-1 rate; an unanswered probe is simply overwritten by the next tick (the gap shows up as last_alive growing stale, which is the exact signal Phase 2 consumes).

last_alive: Option<Instant>

Last time ANY ReportUiThreadAlive arrived — proof the UI thread pumped at that moment, regardless of nonce matching.

consecutive_misses: u32

Phase 2 — consecutive DELIVERED-but-unanswered probes. Incremented when a new probe overwrites an unanswered one; reset by any reply. Retracted probes (send failed — transport evidence, not liveness evidence) never reach the overwrite path, so they can’t inflate this. Consumed by the armed teardown rule (teardown_backstop::should_teardown).

Implementations

impl UiLiveness

pub fn record_probe_sent(&mut self, nonce: u64) -> Option<(u64, Instant)>

Record a probe about to be sent. Returns the previous probe’s (nonce, sent) if it was never answered — the caller logs the miss.

pub fn retract_probe(&mut self, nonce: u64)

Retract an outstanding probe whose SEND failed (reagent P1: a transport failure must never age into a false “UI thread did not pump” report — the probe was never delivered, so its silence is transport evidence, not liveness evidence). No-op if a different probe is outstanding.

pub fn record_alive(&mut self, nonce: u64) -> Option<Duration>

Record a ReportUiThreadAlive. Returns the round-trip latency when the nonce matches the outstanding probe (None for a late/unmatched reply — still recorded as aliveness, since ANY reply proves the UI thread pumped after its probe was sent).

pub fn last_alive(&self) -> Option<Instant>

Phase-2 consumer surface: when did the host’s UI thread last prove itself alive? None = never (host hasn’t answered a single probe yet — startup, or standalone mode with no pipe).

pub fn consecutive_misses(&self) -> u32

Phase-2 consumer surface: consecutive delivered-but-unanswered probes. See the field doc for what does (and doesn’t) count.

Trait Implementations

impl Default for UiLiveness

fn default() -> UiLiveness

Returns the “default value” for a type.