Motion Core

1/**
2 * BoldKit Motion Core — framework-agnostic primitives.
3 *
4 * Consumed by every L3 adapter (React, Vue, future Svelte/Solid/Qwik).
5 * Adding a new framework = wrap these functions. No CSS or token changes needed.
6 *
7 * All functions are SSR-safe: they no-op on the server.
8 */
9 
10const isBrowser = typeof window !== 'undefined' && typeof document !== 'undefined';
11 
12// ──────────────────────────────────────────────────────────────────
13// Reduced motion detection (cached; updates on media-query change)
14// ──────────────────────────────────────────────────────────────────
15 
16let _reducedMotion = false;
17let _reducedMotionMql: MediaQueryList | null = null;
18 
19if (isBrowser) {
20  _reducedMotionMql = window.matchMedia('(prefers-reduced-motion: reduce)');
21  _reducedMotion = _reducedMotionMql.matches;
22  _reducedMotionMql.addEventListener('change', (e) => {
23    _reducedMotion = e.matches;
24  });
25}
26 
27export function prefersReducedMotion(): boolean {
28  return _reducedMotion;
29}
30 
31// ──────────────────────────────────────────────────────────────────
32// observeReveal — IntersectionObserver-driven scroll reveal
33// ──────────────────────────────────────────────────────────────────
34 
35export type RevealOptions = {
36  /** Margin around the root. Negative bottom fires reveal slightly before viewport entry. */
37  rootMargin?: string;
38  /** Intersection ratio threshold. 0 = any pixel visible. */
39  threshold?: number;
40  /** If true, unobserves after first reveal. Default true. */
41  once?: boolean;
42  /** Delay before applying the reveal-in class, in ms. */
43  delay?: number;
44};
45 
46const DEFAULT_REVEAL_OPTS: Required<RevealOptions> = {
47  rootMargin: '0px 0px -10% 0px',
48  threshold: 0,
49  once: true,
50  delay: 0,
51};
52 
53/**
54 * Observes `el` and toggles `.bk-reveal-in` when it enters the viewport.
55 * The element must have the `.bk-reveal` class (and optionally a direction
56 * modifier like `.bk-reveal-up`) already applied for the CSS animation to fire.
57 *
58// … truncated