Spark Signals ⚡️

A standalone reactive signals library for Rust. Fine-grained reactivity, zero-overhead, and TypeScript-like ergonomics.

Spark Signals is a high-performance Rust port of the @rlabs-inc/signals TypeScript library. It solves the "hard problems" of Rust reactivity—type erasure, circular dependencies, and borrow checking—while providing an API that feels like writing TypeScript.

Features

⚡️ Blazing Fast: Benchmarked at ~4ns reads, ~22ns writes. Optimized for game engines and TUIs.
🧠 TypeScript-like Ergonomics: derived!, effect!, and prop! macros make Rust feel like a scripting language.
🔄 Deep Reactivity: TrackedSlotArray and TrackedSlot for fine-grained ECS and layout optimization.
🛡️ Memory Safe: Automatic dependency tracking and cleanup with zero unsafe code in the hot path.
🔌 Framework Agnostic: Use it for UI, games, state management, or backend logic.

Installation

[dependencies]
spark-signals = "0.1.2"

The "Pure Magic" Syntax

Spark Signals provides macros that handle Rc cloning and closure moving for you. Just list your dependencies and write code.

Signals & Deriveds

use spark_signals::{signal, derived};

fn main() {
    let width = signal(10);
    let height = signal(20);

    // "Derived depends on width and height"
    // The macro handles cloning 'width' and 'height' for the closure
    let area = derived!(width, height => width.get() * height.get());

    println!("Area: {}", area.get()); // 200

    width.set(5);
    println!("Area: {}", area.get()); // 100
}

Effects

Side effects that run automatically when dependencies change.

use spark_signals::{signal, effect};

let count = signal(0);

// "Effect reads count"
effect!(count => {
    println!("Count changed to: {}", count.get());
});

count.set(1); // Prints: Count changed to: 1

Props (for Components)

Create getters that capture signals effortlessly.

use spark_signals::{signal, prop, reactive_prop};

let first = signal("Sherlock");
let last = signal("Holmes");

// Create a prop getter
let full_name_prop = prop!(first, last => format!("{} {}", first.get(), last.get()));

// Convert to derived for uniform access
let full_name = reactive_prop(full_name_prop);

println!("{}", full_name.get()); // Sherlock Holmes

Advanced Primitives

Slots & Binding

Slot<T> is a stable reference that can switch between static values, signals, or getters. Perfect for component inputs that might change source type at runtime.

use spark_signals::{slot, signal, PropValue};

let s = slot::<i32>(None);
let sig = signal(42);

// Bind to a signal
s.bind(PropValue::from_signal(&sig));
assert_eq!(s.get(), Some(42));

// Bind to a static value
s.bind(PropValue::Static(100));
assert_eq!(s.get(), Some(100));

Tracked Slots (Optimization)

TrackedSlot automatically reports changes to a shared DirtySet. This is critical for optimizing layout engines (like Taffy) or ECS systems where you only want to process changed items.

use spark_signals::{tracked_slot, dirty_set};

let dirty = dirty_set();
// Slot ID 0 reports to 'dirty' set on change
let width = tracked_slot(Some(10), dirty.clone(), 0);

width.set_value(20);

assert!(dirty.borrow().contains(&0)); // We know ID 0 changed!

Architecture

This library implements the "Push-Pull" reactivity model:

Push: When a signal changes, it marks dependents as DIRTY or MAYBE_DIRTY.
Pull: When a derived is read, it re-executes only if its dependencies are dirty.

It uses a "Father State" pattern (inspired by ECS) where data lives in parallel arrays or stable slots, minimizing object allocation and pointer chasing.

License

MIT

spark-signals 0.2.0