"use client";
import { useEffect, useLayoutEffect, useRef, useState } from 'react';
import { Check } from '@phosphor-icons/react';
import { usePrefersReducedMotion } from './usePrefersReducedMotion';
import './ScrollgalleryDemo.css';
/* Owner-selected albums. Seven approved higher-resolution source files;
Wish You Were Here and Animals retain the supplied artwork and framing. */
const COVERS = [
{
"id": "wish-you-were-here",
"title": "Wish You Were Here",
"releaseYear": 1975,
"artist": "Pink Floyd",
"cover": "/assets/vault/scroll-gallery/wish-you-were-here.webp"
},
{
"id": "fragile",
"title": "Fragile",
"releaseYear": 1971,
"artist": "Yes",
"cover": "/assets/vault/scroll-gallery/fragile.jpg"
},
{
"id": "invaders-must-die",
"title": "Invaders Must Die",
"releaseYear": 2009,
"artist": "The Prodigy",
"cover": "/assets/vault/scroll-gallery/invaders-must-die.jpg"
},
{
"id": "boston",
"title": "Boston",
"releaseYear": 1976,
"artist": "Boston",
"cover": "/assets/vault/scroll-gallery/boston.jpg"
},
{
"id": "led-zeppelin",
"title": "Led Zeppelin",
"releaseYear": 1969,
"artist": "Led Zeppelin",
"cover": "/assets/vault/scroll-gallery/led-zeppelin.jpg"
},
{
"id": "balloonerism",
"title": "Balloonerism",
"releaseYear": 2025,
"artist": "Mac Miller",
"cover": "/assets/vault/scroll-gallery/balloonerism.jpg"
},
{
"id": "pink-moon",
"title": "Pink Moon",
"releaseYear": 1972,
"artist": "Nick Drake",
"cover": "/assets/vault/scroll-gallery/pink-moon.jpg"
},
{
"id": "flower-boy",
"title": "Flower Boy",
"releaseYear": 2017,
"artist": "Tyler, the Creator",
"cover": "/assets/vault/scroll-gallery/flower-boy.jpg"
},
{
"id": "animals",
"title": "Animals",
"releaseYear": 1977,
"artist": "Pink Floyd",
"cover": "/assets/vault/scroll-gallery/animals.jpg"
}
];
const DEFAULT_ID = 'led-zeppelin';
const PLAYBACK_RATE = 1.1;
const AUTOPLAY_INTERVAL_MS = 3600 / PLAYBACK_RATE;
function relativeIndex(index, active, length) {
let relative = index - active;
if (relative > length / 2)
relative -= length;
if (relative < -length / 2)
relative += length;
return relative;
}
export function ScrollgalleryDemo({ compact = false, thumbnail = false, interactive = !compact, controls, sessionRef, resumeAutoplayOnIdle = false, reducedMotion: reducedMotionOverride = false, }) {
const prefersReducedMotion = usePrefersReducedMotion();
const shouldReduceMotion = reducedMotionOverride || prefersReducedMotion;
const keyboardInteractive = interactive || thumbnail;
const idleAutoplay = resumeAutoplayOnIdle && compact && thumbnail && !interactive;
const [activeId, setActiveId] = useState(() => sessionRef?.current?.activeId ?? DEFAULT_ID);
const [theme, setTheme] = useState(() => sessionRef?.current?.theme ?? 'light');
const [menuOpen, setMenuOpen] = useState(false);
const shellRef = useRef(null);
const menuRef = useRef(null);
const stageRef = useRef(null);
const coverRefs = useRef([]);
const dragStart = useRef(null);
const dragging = useRef(false);
const suppressCoverClick = useRef(false);
/* Batch 24: `focus` is the continuous coverflow position (activeIndex +
fractional drag progress). -1 = uninitialized (snaps on first layout). */
const focus = useRef({ value: -1, raf: 0 });
const steps = useRef([217.16, 395.16, 573.16]);
const cardSize = useRef(300);
/* Manual input retires autoplay by default. Legacy interactive thumbnails
can opt into resuming after one preview interval without a gesture. */
const [autoAdvance, setAutoAdvance] = useState(() => sessionRef?.current?.autoAdvance ?? true);
const autoplayHasStarted = useRef(false);
const autoplayScheduler = useRef(null);
const heldAutoplayPointer = useRef(null);
const pauseAutoplayForInteraction = () => {
autoplayHasStarted.current = true;
setAutoAdvance(false);
if (idleAutoplay) autoplayScheduler.current?.restart();
};
/* The portfolio remounts one engine when entering or leaving fullscreen. */
useEffect(() => {
if (sessionRef) sessionRef.current = { activeId, theme, autoAdvance };
}, [sessionRef, activeId, theme, autoAdvance]);
const ordered = COVERS;
const activeIndex = Math.max(0, ordered.findIndex((cover) => cover.id === activeId));
const active = ordered[activeIndex] ?? ordered[0];
const select = (id) => setActiveId(id);
const step = (direction) => {
const next = (activeIndex + direction + ordered.length) % ordered.length;
setActiveId(ordered[next].id);
};
const shuffle = () => {
if (ordered.length < 2)
return;
let next = activeIndex;
while (next === activeIndex)
next = Math.floor(Math.random() * ordered.length);
setActiveId(ordered[next].id);
};
const reset = () => {
setActiveId(DEFAULT_ID);
setTheme('light');
setMenuOpen(false);
};
if (controls) {
controls.reset = reset;
controls.shuffle = shuffle;
controls.openTheme = () => setMenuOpen((open) => !open);
}
useEffect(() => {
if (menuOpen)
menuRef.current?.querySelector('button')?.focus();
}, [menuOpen]);
useEffect(() => {
if (!compact || interactive || (!autoAdvance && !idleAutoplay) || shouldReduceMotion)
return;
/* Start on the first eligible frame without an initial reading pause.
The ref survives selection changes so subsequent advances keep their
cadence. Offscreen, hidden, and reduced-motion previews stay paused. */
const stage = stageRef.current;
if (!stage)
return;
let id = 0;
let visible = false;
const stop = () => {
if (id) window.clearTimeout(id);
id = 0;
};
const canAdvance = () => visible && !document.hidden && (!idleAutoplay || heldAutoplayPointer.current === null);
const restart = () => {
stop();
if (!canAdvance()) return;
id = window.setTimeout(() => {
id = 0;
if (!canAdvance()) return;
autoplayHasStarted.current = true;
if (idleAutoplay) setAutoAdvance(true);
step(1);
}, autoplayHasStarted.current ? AUTOPLAY_INTERVAL_MS : 0);
};
autoplayScheduler.current = { restart };
const io = new IntersectionObserver(([entry]) => {
visible = Boolean(entry?.isIntersecting);
restart();
});
io.observe(stage);
document.addEventListener('visibilitychange', restart);
return () => {
stop();
io.disconnect();
autoplayScheduler.current = null;
document.removeEventListener('visibilitychange', restart);
};
}, [activeIndex, compact, interactive, autoAdvance, ordered, shouldReduceMotion, idleAutoplay]);
const onKeyDown = (event) => {
if (!keyboardInteractive)
return;
if (event.key === 'Escape' && menuOpen) {
event.preventDefault();
event.stopPropagation();
setMenuOpen(false);
event.currentTarget.focus({ preventScroll: true });
return;
}
if (menuOpen)
return;
if (event.key === 'ArrowLeft') {
event.preventDefault();
pauseAutoplayForInteraction();
step(-1);
}
if (event.key === 'ArrowRight') {
event.preventDefault();
pauseAutoplayForInteraction();
step(1);
}
};
/* Batch 24 — fractional coverflow. A single float `focus` (activeIndex +
fractional drag progress) drives every cover's pose per frame: translateX,
translateZ, scale, rotateY, cover/img opacity, depth, and pointer-events
are interpolated between the integer keyframes that previously lived in
the cki-position-* classes, so the incoming cover grows, un-rotates, and
fades into the central pose continuously while dragging. Batch 64
(apple-design skill): settles run on a velocity-aware SPRING (damping 1.0
default / 0.82 with momentum, response ~0.38s) with Apple's momentum
projection picking the release target and the release velocity handed off
— mid-flight grabs and re-targets stay continuous. Reduced motion snaps
instantly. */
const DRAG_START_PX = 8;
/* Batch 64 — apple-design skill (emilkowalski/skills): the release settle
is now a REAL spring, not a fixed-duration bezier tween.
· §4 damping+response parameterization (move/reposition 1.0/0.4;
momentum 0.8/0.3–0.4)
· §5 velocity handoff: the release velocity becomes the spring's
initial velocity — no seam between drag and settle
· §6 momentum projection uses Apple's exact function
(v/1000)·d/(1−d), d = 0.992 (snappier), clamped ±4 cards
· §3 interruptibility: re-targets keep the live spring velocity — no
"brick wall" — and grabbing mid-flight re-tracks from the live
on-screen float. */
const SPRING_RESPONSE = 0.42 / PLAYBACK_RATE;
const SPRING_RESPONSE_FLICK = 0.34 / PLAYBACK_RATE;
const SPRING_DAMPING = 1.0; /* critically damped default (skill §4) */
const SPRING_DAMPING_FLICK = 0.82; /* bounce only when momentum preceded it */
const DECEL_RATE = 0.992; /* Apple's projection decelerationRate (§6) */
const MAX_PROJECT_CARDS = 4;
const spring = useRef({ v: 0 }); /* focus units per second */
const reducedMotion = () => shouldReduceMotion;
/* Apple's momentum projection (Designing Fluid Interfaces sample code) —
NOT the physics-textbook v²/2d form. */
const projectMomentum = (velocityPxPerMs) => (velocityPxPerMs * 1000 / 1000) * DECEL_RATE / (1 - DECEL_RATE);
const measureSteps = () => {
const stage = stageRef.current;
if (!stage)
return;
const style = window.getComputedStyle(stage);
const read = (name, fallback) => {
const value = parseFloat(style.getPropertyValue(name));
return Number.isFinite(value) && value > 0 ? value : fallback;
};
steps.current = [
read('--cki-step-1', steps.current[0]),
read('--cki-step-2', steps.current[1]),
read('--cki-step-3', steps.current[2]),
];
cardSize.current = read('--cki-card-size', cardSize.current);
};
const writePoses = () => {
const covers = coverRefs.current;
const length = ordered.length;
if (length === 0)
return;
const f = focus.current.value;
const [s1, s2, s3] = steps.current;
/* Integer keyframes, |relative| 0 → 4 (4 = parked offscreen pose). */
const X = [0, s1, s2, s3, s3];
/* Normalize the lens to the card, so desktop and phone share the same
trapezoid. Side poses keep one outer-edge height instead of shrinking
toward the panel edges. Preserve the original center magnification. */
const perspective = cardSize.current * 1.8;
const Z = [perspective * (120 / 1100), 0, 0, 0, 0];
const SCALE = [1, 0.84, 0.84, 0.84, 0.84];
const IMG_OPACITY = [1, 0.78, 0.56, 0.34, 0];
const OPACITY = [1, 1, 1, 1, 0];
for (let index = 0; index < length; index += 1) {
const el = covers[index];
if (!el)
continue;
// Spring targets retain their lap for seamless wraparound. Normalize
// every pose across any number of laps so all six neighbors remain.
const relative = ((index - f + length / 2) % length + length) % length - length / 2;
const sign = relative < 0 ? -1 : 1;
const amount = Math.min(4, Math.abs(relative));
const lower = Math.floor(amount);
const frac = amount - lower;
const lerp = (table) => table[lower] + (table[Math.min(4, lower + 1)] - table[lower]) * frac;
const x = sign * lerp(X);
const z = lerp(Z);
const scale = lerp(SCALE);
const rotate = -sign * 52 * Math.min(1, amount);
el.style.transform = `translateX(${x.toFixed(2)}px) perspective(${perspective.toFixed(2)}px) translateZ(${z.toFixed(2)}px) scale3d(${scale.toFixed(4)}, ${scale.toFixed(4)}, ${scale.toFixed(4)}) rotateY(${rotate.toFixed(2)}deg)`;
el.style.opacity = lerp(OPACITY).toFixed(3);
el.style.zIndex = String(Math.round(20 - amount));
el.style.pointerEvents = amount < 3.5 ? 'auto' : 'none';
el.style.setProperty('--cki-img-opacity', lerp(IMG_OPACITY).toFixed(3));
}
};
const cancelFocusTween = () => {
window.cancelAnimationFrame(focus.current.raf);
focus.current.raf = 0;
};
/* Batch 64: spring settle. One semi-implicit Euler integrator on the focus
float; velocity state PERSISTS across re-targets (skill §3 — a reversal
blends velocity instead of hard-cutting it). `handoff` is the release
velocity in focus units/s (skill §5); `momentum` picks the under-damped
spring only when the gesture carried speed (skill §4). */
const startFocusSpring = (targetIndex, { handoff, momentum = false } = {}) => {
cancelFocusTween();
const f = focus.current;
const length = ordered.length;
/* Wrap the target to whichever lap is closest to the current float, so a
step across the first/last boundary scrubs one position, not the whole
deck backwards. */
const target = targetIndex + length * Math.round((f.value - targetIndex) / length);
if ((Math.abs(target - f.value) < 0.0005 && Math.abs(spring.current.v) < 0.001 && !handoff) || reducedMotion()) {
f.value = target;
spring.current.v = 0;
writePoses();
return;
}
const response = momentum ? SPRING_RESPONSE_FLICK : SPRING_RESPONSE;
const damping = momentum ? SPRING_DAMPING_FLICK : SPRING_DAMPING;
const omega = (2 * Math.PI) / response;
const k = omega * omega;
const c = 2 * damping * omega;
if (handoff !== undefined)
spring.current.v = handoff;
window.__ckiMotion = {
engine: 'spring', damping, response,
handoff: handoff ?? null, target, at: performance.now(),
};
let last = performance.now();
const tick = (now) => {
const dt = Math.min(0.032, Math.max(0.001, (now - last) / 1000));
last = now;
const x = f.value;
const accel = -k * (x - target) - c * spring.current.v;
spring.current.v += accel * dt;
f.value = x + spring.current.v * dt;
writePoses();
if (Math.abs(f.value - target) < 0.0008 && Math.abs(spring.current.v) < 0.01) {
f.value = target;
spring.current.v = 0;
writePoses();
f.raf = 0;
}
else {
f.raf = window.requestAnimationFrame(tick);
}
};
f.raf = window.requestAnimationFrame(tick);
};
/* Every non-drag change of the active index (keyboard, cover click,
shuffle/reset, auto-advance, release step) springs focus to it. A release
that crosses cards hands its momentum through pendingMomentum (batch 64:
the effect can't see endDrag's locals). */
const pendingMomentum = useRef(false);
useEffect(() => {
if (focus.current.value < 0)
focus.current.value = activeIndex;
if (!dragging.current) {
const momentum = pendingMomentum.current;
pendingMomentum.current = false;
startFocusSpring(activeIndex, { momentum });
}
}, [activeIndex, shouldReduceMotion]);
/* Mount: measure the container-query step distances and snap the pose table
to the fixed album order. Resize updates are handled by the observer. */
useLayoutEffect(() => {
measureSteps();
if (focus.current.value < 0)
focus.current.value = activeIndex;
writePoses();
}, []);
useEffect(() => {
const stage = stageRef.current;
if (!stage)
return;
const observer = new ResizeObserver(() => {
measureSteps();
writePoses();
});
observer.observe(stage);
/* Cold-load guard (batch 31): the first measurement can land before the
shell's fonts settle; re-measure and rewrite poses once they're ready
so the resting layout never reflects a pre-font geometry. */
let cancelled = false;
document.fonts?.ready.then(() => {
if (cancelled)
return;
measureSteps();
writePoses();
}).catch(() => { });
return () => { cancelled = true; observer.disconnect(); };
}, []);
useEffect(() => cancelFocusTween, []);
const onPointerDown = (event) => {
if ((!interactive && !thumbnail) || event.button !== 0)
return;
if (idleAutoplay) {
heldAutoplayPointer.current = event.pointerId;
pauseAutoplayForInteraction();
}
/* The thumbnail sits inside a draggable anchor — preventDefault keeps the
browser from starting a native link drag (which would pointercancel us)
without affecting the plain-click navigation path. */
event.preventDefault();
/* Interrupting a settle mid-flight normalizes the float to the nearest
lap around the active index and keeps it as the drag base — no jump
(skill §3: re-track from the live presentation value). The drag owns
the motion now, so the spring velocity is zeroed here; pointermove
re-measures velocity from the pointer itself. */
cancelFocusTween();
spring.current.v = 0;
const f = focus.current;
const length = ordered.length;
let value = f.value;
value = activeIndex + ((((value - activeIndex) % length) + length) % length);
if (value - activeIndex > length / 2)
value -= length;
if (value - activeIndex < -length / 2)
value += length;
f.value = value;
dragStart.current = { x: event.clientX, pointerId: event.pointerId, focusBase: value, lastX: event.clientX, lastT: event.timeStamp, vx: 0 };
dragging.current = false;
};
const onPointerMove = (event) => {
const start = dragStart.current;
if (!start || start.pointerId !== event.pointerId)
return;
if (!dragging.current && Math.abs(event.clientX - start.x) > DRAG_START_PX) {
dragging.current = true;
suppressCoverClick.current = true;
if (!interactive)
pauseAutoplayForInteraction();
event.currentTarget.setPointerCapture(event.pointerId);
}
if (!dragging.current)
return;
if (!reducedMotion()) {
/* Batch 32 — multi-card drag: no clamp. focus follows the finger
continuously across as many positions as the gesture covers; the
wrapped fractional pose math in writePoses already renders arbitrary
relative indexes, so covers stream past live. */
focus.current.value = start.focusBase - (event.clientX - start.x) / steps.current[0];
writePoses();
}
const dt = event.timeStamp - start.lastT;
if (dt > 0) {
const v = (event.clientX - start.lastX) / dt;
start.vx = start.vx * 0.7 + v * 0.3;
start.lastX = event.clientX;
start.lastT = event.timeStamp;
}
};
const endDrag = (event, cancelled) => {
if (idleAutoplay && heldAutoplayPointer.current === event.pointerId) {
heldAutoplayPointer.current = null;
autoplayScheduler.current?.restart();
}
const start = dragStart.current;
if (start === null)
return;
const velocity = start.vx;
const didDrag = dragging.current && !cancelled;
dragStart.current = null;
dragging.current = false;
if (event.currentTarget.hasPointerCapture(event.pointerId))
event.currentTarget.releasePointerCapture(event.pointerId);
if (didDrag) {
/* Batch 64 (apple-design §5+§6): pick the target from Apple's momentum
projection of the release point, then hand the spring the release
velocity — the settle continues at the finger's exact speed, with a
slight bounce (damping 0.82) ONLY when the gesture carried momentum.
A slow drag projects ~0 → nearest integer + critically damped. */
const length = ordered.length;
const projectedPx = projectMomentum(velocity);
const extra = Math.max(-MAX_PROJECT_CARDS, Math.min(MAX_PROJECT_CARDS, -projectedPx / steps.current[0]));
const target = Math.round(focus.current.value + extra);
const handoff = (-velocity * 1000) / steps.current[0]; /* focus units/s */
const momentum = Math.abs(extra) > 0.15 || Math.abs(handoff) > 1.5;
const nextIndex = ((target % length) + length) % length;
window.__ckiRelease = {
projectedPx, extra, handoff, momentum, target, at: performance.now(),
};
if (nextIndex !== activeIndex) {
spring.current.v = handoff; /* carried into the effect's re-target */
pendingMomentum.current = momentum;
setActiveId(ordered[nextIndex].id);
}
else {
startFocusSpring(activeIndex, { handoff, momentum });
}
}
else {
startFocusSpring(activeIndex);
}
window.setTimeout(() => { suppressCoverClick.current = false; }, 0);
};
const onPointerUp = (event) => endDrag(event, false);
const onPointerCancel = (event) => endDrag(event, true);
useEffect(() => {
if (!idleAutoplay) return;
/* A press can leave the stage before reaching the drag threshold.
Route that release through cancellation so no stale drag survives. */
const releaseOutsideStage = (event) => {
if (heldAutoplayPointer.current !== event.pointerId || !stageRef.current) return;
endDrag({ pointerId: event.pointerId, currentTarget: stageRef.current }, true);
};
window.addEventListener('pointerup', releaseOutsideStage);
window.addEventListener('pointercancel', releaseOutsideStage);
return () => {
window.removeEventListener('pointerup', releaseOutsideStage);
window.removeEventListener('pointercancel', releaseOutsideStage);
};
}, [idleAutoplay, activeIndex, ordered, shouldReduceMotion]);
const chooseTheme = (mode) => {
setTheme(mode);
setMenuOpen(false);
shellRef.current?.focus({ preventScroll: true });
};
/* After a drag, the trailing click must not bubble into the surrounding
LinkCard (feed thumbnail) or fire a cover select (interactive views).
Capturing and killing it here keeps plain clicks navigating as before. */
const onClickCapture = (event) => {
if (!suppressCoverClick.current)
return;
event.preventDefault();
event.stopPropagation();
};
return (<div ref={shellRef} className={`cki-shell ${compact ? 'cki-compact' : ''} ${thumbnail ? 'cki-thumbnail' : ''} ${shouldReduceMotion ? 'cki-reduced-motion' : ''} cki-theme-${theme}`} tabIndex={keyboardInteractive ? 0 : undefined} onKeyDown={onKeyDown} onClickCapture={onClickCapture} aria-label={keyboardInteractive ? 'Album cover gallery. Use left and right arrow keys to browse.' : undefined}>
<div className="cki-gallery">
<div ref={stageRef} className="cki-stage" onPointerDown={onPointerDown} onPointerMove={onPointerMove} onPointerUp={onPointerUp} onPointerCancel={onPointerCancel}>
<div className="cki-mask" aria-hidden="true"/>
{ordered.map((cover, index) => {
const relative = relativeIndex(index, activeIndex, ordered.length);
const className = `cki-cover ${relative === 0 ? 'is-active' : ''}`;
/* Batch 31: the artwork starts transparent (placeholder surface
shows from the first frame) and fades in on decode. The ref
check covers images that were already complete from cache. */
const markLoaded = (img) => {
if (img?.complete && img.naturalWidth > 0)
img.style.setProperty('--cki-loaded', '1');
};
const setCoverRef = (el) => {
coverRefs.current[index] = el;
markLoaded(el?.querySelector('img') ?? null);
};
const onImgLoad = (event) => {
event.currentTarget.style.setProperty('--cki-loaded', '1');
};
/* Covers have fixed geometry. Their image loads must not
trigger a full-page scroll refresh in the portfolio. */
if (!interactive) {
return (
/* Feed thumbnail (batch 22): covers select in place instead
of navigating — the click is stopped before it reaches the
wrapping LinkCard, and taking manual control also pauses
the auto-advance, same as a drag. Kept as a plain div
(aria-hidden) so no button nests inside the card anchor. */
<div key={cover.id} ref={setCoverRef} className={className} aria-hidden="true" onClick={thumbnail ? (event) => {
event.preventDefault();
event.stopPropagation();
if (suppressCoverClick.current)
return;
pauseAutoplayForInteraction();
select(cover.id);
} : undefined}>
<img src={cover.cover} alt="" draggable={false} data-smooth-scroll-static-media="" onLoad={onImgLoad}/>
<span className="cki-cover-caption" aria-hidden="true"><strong>{cover.title}</strong><small>{cover.artist}</small></span>
</div>);
}
return (<button key={cover.id} ref={setCoverRef} type="button" className={className} data-cover-index={index} data-cover-id={cover.id} aria-current={relative === 0 ? 'true' : undefined} aria-label={cover.title} onClick={(event) => {
if (suppressCoverClick.current) {
event.preventDefault();
return;
}
select(cover.id);
}}>
<img src={cover.cover} alt="" draggable={false} data-smooth-scroll-static-media="" onLoad={onImgLoad}/>
<span className="cki-cover-caption" aria-hidden="true"><strong>{cover.title}</strong><small>{cover.artist}</small></span>
</button>);
})}
</div>
</div>
{/* The cover carries the visible caption; announce selection without
adding metadata or controls to the white canvas. */}
{keyboardInteractive ? (<div className="cki-heading" aria-live={interactive || !autoAdvance ? 'polite' : 'off'}>
<h2>{active.title}</h2>
<p>{active.artist}</p>
</div>) : null}
{menuOpen && interactive ? (<div ref={menuRef} className="cki-menu" role="group" aria-label="Gallery theme">
<button type="button" aria-pressed={theme === 'light'} onClick={() => chooseTheme('light')}>Light{theme === 'light' && <Check size={14}/>}</button>
<button type="button" aria-pressed={theme === 'dark'} onClick={() => chooseTheme('dark')}>Dark{theme === 'dark' && <Check size={14}/>}</button>
</div>) : null}
</div>);
}
