Crate day_reactive 

day-reactive — the reactive core (DESIGN.md §3.3, §4).

Build-once / bind-forever: signals, memos, effects, bind, and watch over a thread-local generational arena. All handles are Copy and !Send; the only cross-thread door is Setter. Writes batch; the drain runs to fixpoint in (priority, scope-depth, creation-seq) order; layout/turn-end callbacks run once after the fixpoint (§3.3’s turn state machine).

Signal is !Send:

fn assert_send<T: Send>(_: T) {}
let s = day_reactive::Signal::new(1);
assert_send(s); // must not compile

Structs

Effect

A reaction that re-runs when its tracked reads change. Runs once at creation.

Memo

Cached, equality-diffed derived value (§4.2).

NodeKey

Resource

Declarative async data loading (§4.5): a TRACKED source whose value feeds an async fetcher; the result lands in a Signal<Load<T>>. The source re-runs when its tracked reads change; an unchanged source value refetches nothing, Resource::refetch always does. Latest wins: a source change supersedes the in-flight fetch (aborting its task — dropping any FetchFuture inside cancels the platform request) and a stale completion writes nothing. Scope disposal aborts the in-flight fetch the same way.

Scope

Ownership scope for signals/effects (§4.3). Copy handle; not Send.

ScopeKey

Setter

Send write-only handle to a signal; delivery hops to the UI thread via the main poster. Writes after disposal are silent no-ops (§4.3).

Signal

A Copy, !Send reactive value handle (§4.2).

Trigger

Data-less invalidation source.

Enums

Load

The lifecycle of an async-loaded value. Failed carries the fetcher’s error as a shared trait object so Load stays Clone for signal reads.

Functions

batch

bind

The binding primitive (§4.2): compute (tracked) + apply (untracked), equality-gated. Structural priority — bindings drain before plain effects. apply receives the new value by reference so V needs only PartialEq (no Clone).

bind_always

bind for payloads without PartialEq — applies on every recompute.

bind_seeded

bind pre-seeded with the value already applied at build time: the initial run does NOT re-apply (pieces pass initial values through realize props; §5.2’s no-duplicate-op rule).

flush_now

Force a synchronous fixpoint drain now, even inside an open batch. Event dispatch wraps handlers in a batch (day-core), so a handler that needs its writes to drain immediately — namely with_animation, whose ambient animation must be live while the resulting patches apply — cannot rely on the batch’s own close (that runs later, after the scope ends). This temporarily drops the batch depth so flush_sync runs, then restores it. No-op if a drain is already in progress (the writes fold into it); harmless if nothing is pending.

flush_sync

Drain the pending queue to fixpoint, then run turn-end callbacks once (§3.3 steps 2–3).

has_main_poster

Whether a backend has installed the main poster yet — i.e. whether on_main would work rather than panic. Platform glue that can be called BEFORE launch (a notification tap that cold-starts the process) probes this and buffers instead of posting. The poster is set once and never cleared, so a false can only become true: a caller that buffers on a false negative is still correct, provided something drains the buffer at launch.

install_delayed_poster

Install the timer door (Platform::post_delayed). Backends call this once at startup.

install_main_poster

Install the cross-thread → main-thread door. Backends call this once at startup.

install_scheduler

Install “post a drain on the main loop”. Backends call this once at startup.

install_spawner

Install the async-spawn door: spawn runs a future on the app’s main-loop executor and returns an ABORT closure (remove + drop the future). The abort MUST be a no-op once the task has completed — Resource stores it after an eager first poll, so a synchronously ready future has already finished by then. day-core’s launch_with wires this to day::task / TaskHandle::abort; call it once at startup (docs/async.md).

on_main

Schedule f on the UI thread (usable from any thread once a backend installed the poster).

on_main_delayed

Schedule f on the UI thread after (at least) ms milliseconds — the rail behind day::sleep (docs/async.md).

on_turn_end

Register a callback run once after every fixpoint drain (day-core’s layout turn).

recover_from_panic

Reset the runtime to a clean idle state after a panic unwound through a drain or batch — e.g. a reactive-cycle assertion ([RERUN_CAP]) that tripped inside a native event callback which the backend contained (rather than letting it abort the process across the C ABI — a GTK/Qt signal trampoline can’t unwind). The in-flight pending work and the observer stack are dropped (the next interaction re-derives them); persistent registrations (effects, memos, turn-end hooks) are kept.

untrack

Run f without tracking reads.

watch

Derive-state without effect-write loops (§4.2): source is tracked; cb runs untracked with (new, old). Does NOT fire for the initial value.

Type Aliases

LocalBoxFuture

A boxed, !Send future for the install_spawner executor door.