@sigx/lynx-motion

Spring and tween animation drivers for SignalX on Lynx, built directly on SharedValue from @sigx/lynx. One customer of the cross-thread bridge alongside gestures and scroll.

The differentiator: animation progress is observable from the background thread for free. Mutate a SharedValue on MT via withSpring(sv, target) — the existing diff/publish bridge ships every frame to a BG-side sigx signal, so effect(() => sv.value) re-runs reactively.

📚 Documentation

Full API, springs vs tweens, composition, easings and live examples → sigx.dev/lynx/modules/motion/overview

Install

npm install @sigx/lynx-motion

A taste

The animation tick runs on MT, so withSpring / withTiming / animate calls must sit inside a 'main thread' context (e.g. a main-thread-bindtap handler):

import { component, useSharedValue, useAnimatedStyle, useMainThreadRef } from '@sigx/lynx';
import { withSpring, withTiming } from '@sigx/lynx-motion';

const App = component(() => {
  const x = useSharedValue(0);
  const boxRef = useMainThreadRef(null);
  useAnimatedStyle(boxRef, x, 'translateX', { factor: 1 });

  return () => (
    <view>
      <view main-thread:ref={boxRef} style={{ width: 60, height: 60, backgroundColor: '#facc15' }} />
      <view main-thread-bindtap={() => {
        'main thread';
        withSpring(x, 200, { stiffness: 200, damping: 20 });
      }}>
        <text>spring</text>
      </view>
      {/* BG-reactive — updates per animation frame for free */}
      <text>x = {x.value.toFixed(0)}px</text>
    </view>
  );
});

The full animate / withSpring / withTiming API, composition patterns (concurrent, sequential, cancellation), the easing set, tick scheduling and current limitations are documented on the docs site.

Attribution

Spring solver and easing functions are ported from @lynx-js/motion v0.0.3, motion-dom v12.23.12, and motion-utils v12.23.6 — all Apache-2.0. The cubic bezier code is in turn modified from Gaëtan Renaudeau's bezier-easing (MIT).

License

MIT (sigx adaptation). Ported portions remain under their upstream licenses (Apache-2.0 and MIT, see attribution above).