# Button Group (Notchset): prompt.md (v1.0.0)

- id: `button-group` · version 1.0.0 · component · free
- category: Actions
- build: Base UI (this item also ships a Radix build)
- install (this build): `npx shadcn@latest add https://notchset.dev/r/button-group.json`
- npm dependencies: @base-ui/react@^1, class-variance-authority@^0.7
- registry dependencies: utils, https://notchset.dev/r/notchset-foundation.json
- docs: https://notchset.dev/components/button-group
- The install command carries everything this item needs (files, CSS, tokens, npm and registry dependencies). Prefer it to copying source by hand.

shadcn's Button Group in Notchset: related actions in one ink frame sharing one hover block that stretches from key to key, leading edge first; with items, the instrument selector, where an ink block travels under the labels and the chosen node lights after it lands.

## Build it
- Stack: React 19 (`ref` is a plain prop), TypeScript, Tailwind CSS v4 utilities, a shadcn-initialised project with the `@/*` alias.
- Packages: `@base-ui/react@^1`, `class-variance-authority@^0.7` (Base UI build); `class-variance-authority@^0.7`, `radix-ui@^1` (Radix build).
- Files: `components/ui/notchset/button-group.tsx`; shared code: `lib/beautiful-ui/notchset/button-group.tsx`, `lib/beautiful-ui/notchset/instrument.tsx`, `lib/beautiful-ui/notchset/root.ts`.
- Registry dependencies, installed with it automatically: shadcn `utils` (cn), `notchset-foundation`.
- Builds: separate Base UI and Radix files. Install the one that matches the project (see Install): a free item's bare URL installs the Base UI build of it and its dependencies.
- Exports to keep: `ButtonGroup`, `ButtonGroupSeparator`, `ButtonGroupText`, `buttonGroupVariants`, and every exported type.
- CSS: the install adds the notchset foundation (tokens, keyframes, motion levels) to your global stylesheet once. Nothing to import by hand.
- Re-running `add` (or `--overwrite`) re-applies those rules: put overrides in your own CSS, never in the installed rules.
- Tokens: retheme with the `--notchset-*` custom properties (`--notchset-check`, `--notchset-control-edge`, `--notchset-draw-from`, `--notchset-ease-bloom`, `--notchset-ease-glide`, `--notchset-ease-key-down`, `--notchset-ease-key-up`, `--notchset-ease-travel`, `--notchset-fade`, `--notchset-focus-color`, `--notchset-focus-inset`, `--notchset-grow-to`, `--notchset-key-down`, `--notchset-key-up`, `--notchset-life-from`, `--notchset-life-ms`, `--notchset-node-blink`, `--notchset-node-bloom`, `--notchset-node-delay`, `--notchset-plate-color`, `--notchset-rise-from`, `--notchset-rule`, `--notchset-scan-to`, `--notchset-scroll`, `--notchset-sheet-from`, `--notchset-signal`, `--notchset-sweep-to`, `--notchset-travel`). Never add Tailwind colour classes inside the component.

```tsx
import { ButtonGroup } from "@/components/ui/notchset/button-group";
```

## Parts

| Part | data-slot | What it is for |
|---|---|---|
| `ButtonGroup` | `button-group` | The frame (or the selector's radiogroup). |
| `ButtonGroupSeparator` | `button-group-separator` | An ink divider. |
| `ButtonGroupText` | `button-group-text` | A text segment. |

Style a part with `[data-slot="<slot>"]` selectors or its `className`; keep the attributes when editing.

## Sound
- Keep every `data-slot` and `data-sound` attribute: the sound layer reads them.
- Installing this item adds no audio. Nothing plays until the app mounts `SoundProvider` once (install: `npx shadcn@latest add https://notchset.dev/r/notchset-sound.json`, import from `@/components/ui/notchset/sound-provider`); `useSound()` gives `muted` and `setMuted` for a mute control. Without a provider the audio engine never loads.

## Match the original
- Read `components/ui/notchset/button-group.tsx` as the reference implementation before changing or recreating anything, and match it: sizes, colours per theme, motion timings, copy and behaviour.
- If you deviate (a prop you can't honour, a style you changed, a dependency you swapped), say so in your reply, part by part.
- Keep the accessibility contract, the keyboard map and the motion levels listed below.

## Use it when
- button group, segmented control, range picker, time range, single select, toolbar group, Notchset
- Picking one of a few ranges or modes
- Joining related buttons, as shadcn's Button Group

### Not when
- More than five or six choices: use a Select

## Mistakes
- Give the selector an aria-label

## Usage

```tsx
"use client";

import * as React from "react";
import { ButtonGroup } from "@/components/ui/notchset/button-group";

export function RangePicker() {
  const [range, setRange] = React.useState("7D");
  return (
    <ButtonGroup
      aria-label="Range"
      items={[
        { value: "24H", label: "24H" },
        { value: "7D", label: "7D" },
        { value: "30D", label: "30D" },
      ]}
      value={range}
      onValueChange={setRange}
    />
  );
}
```

## Props

| Prop | Type | Default | What it does |
|---|---|---|---|
| `items` | `{ value, label }[]` |  | Makes it the selector. Without items it is shadcn's ButtonGroup. |
| `value / defaultValue / onValueChange` | `string / (value) => void` |  | The selected item. |
| `nodes` | `boolean` |  | The nodes above the segments. Default true. |
| `segment` | `number` |  | Segment width in px. Default 56. |
| `orientation` | `"horizontal" \| "vertical"` |  | As shadcn; the selector stacks vertically too. |

Full docs: https://notchset.dev/components/button-group

## Customising
- Colours: the component reads your shadcn tokens (`--background`, `--foreground`, `--border` …), refined by the `--notchset-*` tokens. The signal colour is `--notchset-signal` (it falls back to `--destructive`). Set tokens on `:root`, or on any container to retheme one area.
- Dark mode follows the `.dark` class on an ancestor (the shadcn and next-themes convention).
- Update later by re-running the install with `--overwrite` (review the diff if you edited it). Changelog: https://notchset.dev/r/changelog.json

## Keyboard

| Keys | Action |
|---|---|
| ← → / ↑ ↓ | Move the choice |
| Home / End | First or last |

## Performance

- The selector thumb is one element moved with a transform; the count flips text only when it changes.

## Responsive

- Segments share the width evenly; long labels truncate.
- 44px segments on touch screens.

## Motion inventory

| Interaction | What moves |
|---|---|
| Choose | The ink block travels in 340ms cubic-bezier(.34,1.25,.5,1); the label colour switches after 110ms; the node lights 200ms after |

## Accessibility contract (preserve when editing)
- The selector is a radiogroup with roving tabindex; children mode is role=group as shadcn
- Selection reads from the ink block and the node, not colour alone

## Install

Base UI project (a base-* style in components.json):

```bash
npx shadcn@latest add https://notchset.dev/r/button-group.json
```

Radix project (a radix-*, new-york or default style):

```bash
npx shadcn@latest add https://notchset.dev/r/radix-nova/button-group.json
```

Or add the `@notchset` registry to components.json and run `npx shadcn@latest add @notchset/button-group`: the CLI picks the build from your style.

## Credits
- Built on shadcn/ui (https://ui.shadcn.com)

## Source (Base UI build)

### components/ui/notchset/button-group.tsx

```tsx
"use client";

/**
 * Button Group (Notchset) v1.0.0 · Notchset
 * Docs: https://notchset.dev/components/button-group
 * MIT licensed: free to use, change and share.
 */

import type * as React from "react";
import { mergeProps } from "@base-ui/react/merge-props";
import { useRender } from "@base-ui/react/use-render";
import { cn } from "@/lib/utils";
import { Separator as SeparatorPrimitive } from "@base-ui/react/separator";
import { withClass } from "@/lib/beautiful-ui/notchset/instrument";
import { ButtonGroup, buttonGroupSeparatorClass, buttonGroupTextClass, buttonGroupVariants } from "@/lib/beautiful-ui/notchset/button-group";

/*
 * Notchset Button Group (Base UI build). shadcn's Button Group in Notchset (ButtonGroup,
 * ButtonGroupSeparator, ButtonGroupText with `render`, buttonGroupVariants); with `items` it is
 * the instrument selector.
 */

function ButtonGroupText({ className, render, ...props }: useRender.ComponentProps<"div">) {
  return useRender({
    defaultTagName: "div",
    props: mergeProps<"div">({ className: cn(buttonGroupTextClass, className) }, props),
    render,
    state: { slot: "button-group-text" },
  });
}

/** shadcn's separator, on Base UI's Separator (render, orientation). */
function ButtonGroupSeparator({ className, orientation = "vertical", ...props }: SeparatorPrimitive.Props) {
  return <SeparatorPrimitive data-slot="button-group-separator" orientation={orientation} className={withClass(buttonGroupSeparatorClass(orientation), className)} {...props} />;
}

export { ButtonGroup, ButtonGroupSeparator, ButtonGroupText, buttonGroupVariants };
export type { ButtonGroupItem, ButtonGroupProps } from "@/lib/beautiful-ui/notchset/button-group";
export type ButtonGroupTextProps = React.ComponentProps<typeof ButtonGroupText>;
```

### lib/beautiful-ui/notchset/button-group.tsx

```tsx
"use client";

import * as React from "react";
import { cva } from "class-variance-authority";
import { cn } from "@/lib/utils";
import { Node, OWN_SOUND, playCue, NOTCHSET_ROOT, useComposedRefs } from "@/lib/beautiful-ui/notchset/instrument";

/*
 * Notchset Button Group, shared by both builds. With children it is shadcn's ButtonGroup in Notchset:
 * buttons joined in one ink frame with rule dividers. With `items` it is the instrument selector:
 * segments in an ink frame, an ink block that travels under the labels, and a row of nodes where
 * the chosen one lights after the block lands. Arrow keys move the choice (roving tabindex).
 */

const buttonGroupVariants = cva(
  "flex w-fit items-stretch border border-solid border-foreground bg-background has-[>[data-slot=button-group]]:gap-2 has-[>[data-slot=button-group]]:border-0 [&>*]:focus-visible:relative [&>*]:focus-visible:z-10 [&>[data-slot=button]]:border-0",
  {
    variants: {
      orientation: {
        // Wraps instead of running past a narrow container; each joined key is pulled back 1px, so the rule
        // that starts a wrapped row sits on the outer border instead of doubling it.
        horizontal: "max-w-full flex-wrap [&>*:not(:first-child)]:-ms-px [&>*:not(:first-child)]:border-l [&>*:not(:first-child)]:border-solid [&>*:not(:first-child)]:border-[var(--notchset-rule,var(--border))]",
        vertical: "flex-col [&>*:not(:first-child)]:border-t [&>*:not(:first-child)]:border-solid [&>*:not(:first-child)]:border-[var(--notchset-rule,var(--border))]",
      },
    },
    defaultVariants: { orientation: "horizontal" },
  },
);

export type ButtonGroupItem = { value: string; label: string };

export type ButtonGroupProps = Omit<React.ComponentProps<"div">, "defaultValue"> & {
  orientation?: "horizontal" | "vertical";
  /** Makes it the selector. */
  items?: readonly ButtonGroupItem[];
  value?: string;
  defaultValue?: string;
  onValueChange?: (value: string) => void;
  /** The selector's nodes. Default true. */
  nodes?: boolean;
  /** The selector's segment size along the group, px. Default 56 (horizontal) or 40 (vertical). */
  segment?: number;
};

function ButtonGroup({ items, value, defaultValue, onValueChange, nodes = true, segment, orientation = "horizontal", className, children, ...props }: ButtonGroupProps) {
  if (items) {
    return <ButtonGroupSelector items={items} value={value} defaultValue={defaultValue} onValueChange={onValueChange} nodes={nodes} segment={segment} orientation={orientation} className={className} {...props} />;
  }
  return (
    <JoinedGroup orientation={orientation} className={className} {...props}>
      {children}
    </JoinedGroup>
  );
}

type Block = { left: number; right: number; on: boolean; leadRight: boolean; snap: boolean };

/**
 * The joined group. Horizontal groups share one hover block: a field-coloured block behind the keys
 * that stretches from key to key, its leading edge first and the trailing edge 80ms later, and fades
 * when the pointer leaves. It is never drawn behind a pressed (ink) or disabled key.
 */
function JoinedGroup({ orientation, className, children, onPointerOver, onPointerLeave, ref, ...props }: React.ComponentProps<"div"> & { orientation: "horizontal" | "vertical" }) {
  const own = React.useRef<HTMLDivElement>(null);
  const refs = useComposedRefs<HTMLDivElement>(ref, own);
  const [block, setBlock] = React.useState<Block>({ left: 0, right: 0, on: false, leadRight: true, snap: true });
  const horizontal = orientation === "horizontal";
  const track = (e: React.PointerEvent<HTMLDivElement>) => {
    onPointerOver?.(e);
    const group = own.current;
    if (!group || !horizontal) return;
    let key = e.target as HTMLElement | null;
    while (key && key.parentElement !== group) key = key.parentElement;
    if (!key) return;
    const control = (key.matches("button") ? key : key.querySelector("button")) as HTMLButtonElement | null;
    if (control?.disabled || control?.getAttribute("aria-disabled") === "true" || control?.getAttribute("aria-pressed") === "true") {
      setBlock((b) => ({ ...b, on: false }));
      return;
    }
    const left = key.offsetLeft;
    const right = group.clientWidth - (key.offsetLeft + key.offsetWidth);
    // Appearing, it lands on the key; only moves between keys stretch.
    setBlock((b) => ({ left, right, on: true, leadRight: left >= b.left, snap: !b.on }));
  };
  const glide = "cubic-bezier(.65,0,.35,1)";
  return (
    <div
      {...NOTCHSET_ROOT}
      {...props}
      ref={refs}
      role="group"
      data-slot="button-group"
      data-orientation={orientation}
      onPointerOver={track}
      onPointerLeave={(e) => {
        onPointerLeave?.(e);
        setBlock((b) => ({ ...b, on: false }));
      }}
      className={cn(buttonGroupVariants({ orientation }), horizontal && "relative isolate [&>[data-slot=button]]:hover:bg-transparent", className)}
    >
      {horizontal && (
        <span
          aria-hidden
          data-slot="button-group-block"
          className="pointer-events-none absolute inset-y-0 -z-10 bg-[var(--notchset-sheet,var(--accent))] motion-reduce:transition-none"
          style={{
            left: block.left,
            right: block.right,
            opacity: block.on ? 1 : 0,
            // Moving right, the right edge leads; moving left, the left edge leads.
            transition: block.on && !block.snap
              ? `left 300ms ${glide} ${block.leadRight ? 80 : 0}ms, right 300ms ${glide} ${block.leadRight ? 0 : 80}ms, opacity 140ms linear`
              : "opacity 140ms linear",
          }}
        />
      )}
      {children}
    </div>
  );
}

function ButtonGroupSelector({
  items,
  value: valueProp,
  defaultValue,
  onValueChange,
  nodes,
  segment,
  orientation = "horizontal",
  className,
  style,
  onKeyDown,
  ref,
  ...props
}: Omit<ButtonGroupProps, "items"> & { items: readonly ButtonGroupItem[] }) {
  const vertical = orientation === "vertical";
  const seg = segment ?? (vertical ? 40 : 56);
  const [own, setOwn] = React.useState(defaultValue ?? items[0]?.value ?? "");
  const value = valueProp ?? own;
  const index = Math.max(0, items.findIndex((i) => i.value === value));
  const root = React.useRef<HTMLDivElement>(null);
  const refs = useComposedRefs<HTMLDivElement>(ref, root);
  const choose = (i: number, focus = false) => {
    const next = items[i];
    if (!next) return;
    if (next.value !== value) {
      playCue(root.current, "tick");
      setOwn(next.value);
      onValueChange?.(next.value);
    }
    if (focus) root.current?.querySelectorAll<HTMLButtonElement>("[role=radio]")[i]?.focus();
  };
  const move = (e: React.KeyboardEvent<HTMLDivElement>) => {
    onKeyDown?.(e);
    if (e.defaultPrevented) return;
    const d = e.key === "ArrowRight" || e.key === "ArrowDown" ? 1 : e.key === "ArrowLeft" || e.key === "ArrowUp" ? -1 : 0;
    const to = e.key === "Home" ? 0 : e.key === "End" ? items.length - 1 : d ? (index + d + items.length) % items.length : -1;
    if (to < 0) return;
    e.preventDefault();
    choose(to, true);
  };
  return (
    <div
      {...NOTCHSET_ROOT}
      ref={refs}
      role="radiogroup"
      aria-orientation={orientation}
      data-slot="button-group"
      data-orientation={orientation}
      onKeyDown={move}
      className={cn("inline-flex gap-[9px]", vertical ? "flex-row" : "flex-col", className)}
      style={{ "--seg": `${seg}px`, ...style } as React.CSSProperties}
      {...props}
    >
      {nodes && (
        <div aria-hidden className={cn("flex", vertical && "flex-col")}>
          {items.map((it, i) => (
            <span key={it.value} className={cn("flex items-center justify-center", vertical ? "h-(--seg)" : "w-(--seg)")}>
              <Node state={i === index ? "on" : "off"} delay={i === index ? 200 : 0} />
            </span>
          ))}
        </div>
      )}
      <div className={cn("relative flex w-max border border-solid border-foreground bg-background", vertical && "flex-col")}>
        <span
          aria-hidden
          data-slot="button-group-block"
          className={cn("absolute bg-primary transition-transform duration-[var(--notchset-block)] ease-[var(--notchset-ease-block)]", vertical ? "inset-x-0 top-0 h-(--seg)" : "inset-y-0 left-0 w-(--seg)")}
          style={{ transform: vertical ? `translateY(calc(${index} * var(--seg)))` : `translateX(calc(${index} * var(--seg)))` }}
        />
        {items.map((it, i) => (
          <button key={it.value}
            {...OWN_SOUND}
            type="button"
            role="radio"
            aria-checked={i === index}
            tabIndex={i === index ? 0 : -1}
            onClick={() => choose(i)}
            className={cn(
              `notchset-focus`,
              "relative cursor-pointer border-0 bg-transparent p-0 font-mono text-[12px] font-medium tracking-[0.08em] uppercase transition-colors delay-[110ms] duration-[120ms]",
              vertical ? "h-(--seg) min-w-14 px-3" : "h-10 w-(--seg) pointer-coarse:h-11",
              i > 0 && (vertical ? "border-t border-solid border-[var(--notchset-rule,var(--border))]" : "border-l border-solid border-[var(--notchset-rule,var(--border))]"),
              i === index ? "text-primary-foreground" : "text-foreground",
            )}
          >
            {it.label}
          </button>
        ))}
      </div>
    </div>
  );
}

const buttonGroupTextClass = "flex items-center gap-2 px-3 font-mono text-[12px] tracking-[0.07em] text-muted-foreground uppercase [&_svg]:pointer-events-none [&_svg:not([class*='size-'])]:size-4";

/** The separator's look; each build wraps its own Separator primitive with it (as shadcn does). */
const buttonGroupSeparatorClass = (orientation: "horizontal" | "vertical") => cn("relative !m-0 self-stretch bg-foreground", orientation === "vertical" ? "w-px" : "h-px");

export { ButtonGroup, buttonGroupSeparatorClass, buttonGroupTextClass, buttonGroupVariants };
```

### lib/beautiful-ui/notchset/instrument.tsx

```tsx
"use client";

import * as React from "react";
import { createPortal } from "react-dom";
import { cn } from "@/lib/utils";

/*
 * Notchset instrument parts, shared by every member of a pack: the node (a round light that reports
 * state), the legend printed above a control, the plate a key presses onto, the traced check, the
 * five-tick scanner, and the glyph flip that lands a changed label left to right. Nodes and checks
 * are inline SVG (round at every DPR); the CSS lives in the Notchset foundation. Also: the one motion
 * policy (reduced motion or a data-motion="off" ancestor), ref composition, the portal container
 * and the sound attributes every Notchset root carries.
 */

// ---------------------------------------------------------------------------------------------
// Motion, refs, portals, sound
// ---------------------------------------------------------------------------------------------

/**
 * Whether motion is off for an element, kept live: it follows the OS reduced-motion setting and any
 * data-motion attribute change above it, so a preference switched mid-playback stops decoration at once.
 */
export function useMotionOff(ref: React.RefObject<Element | null>) {
  const [off, setOff] = React.useState(false);
  React.useEffect(() => {
    const read = () => setOff(motionOff(ref.current));
    const r = requestAnimationFrame(read);
    const mq = window.matchMedia?.("(prefers-reduced-motion: reduce)");
    mq?.addEventListener?.("change", read);
    const mo = new MutationObserver(read);
    mo.observe(document.documentElement, { attributes: true, attributeFilter: ["data-motion"], subtree: true });
    return () => {
      cancelAnimationFrame(r);
      mq?.removeEventListener?.("change", read);
      mo.disconnect();
    };
  }, [ref]);
  return off;
}

/**
 * The microphone, or a rejection after `timeoutMs` (a prompt left open, a denied permission). A stream
 * that arrives after the timeout is stopped at once, so a late "Allow" never leaves the mic on.
 */
export function requestMic(timeoutMs = 5000): Promise<MediaStream> {
  if (typeof navigator === "undefined" || !navigator.mediaDevices?.getUserMedia) return Promise.reject(new Error("no mic"));
  const ask = navigator.mediaDevices.getUserMedia({ audio: true });
  return new Promise((resolve, reject) => {
    let late = false;
    const t = setTimeout(() => {
      late = true;
      reject(new Error("timeout"));
    }, timeoutMs);
    ask.then(
      (stream) => {
        clearTimeout(t);
        if (late) stream.getTracks().forEach((track) => track.stop());
        else resolve(stream);
      },
      (err) => {
        clearTimeout(t);
        reject(err);
      },
    );
  });
}

/** True under prefers-reduced-motion or inside a data-motion="off" scope. Checked when an effect runs. */
export function motionOff(el: Element | null | undefined) {
  if (typeof window === "undefined") return true;
  if (window.matchMedia?.("(prefers-reduced-motion: reduce)").matches) return true;
  return Boolean(el?.closest('[data-motion="off"]'));
}

function assignRef<T>(ref: React.Ref<T> | undefined, node: T | null): () => void {
  if (typeof ref === "function") {
    const cleanup = ref(node);
    return typeof cleanup === "function" ? cleanup : () => ref(null);
  }
  if (ref) (ref as React.RefObject<T | null>).current = node;
  return () => {
    if (ref) (ref as React.RefObject<T | null>).current = null;
  };
}

/**
 * Puts text on the clipboard. Resolves true once it is there and false when the browser refuses (no
 * permission, an insecure page, no clipboard API), so a "copied" state is only ever shown for a copy.
 */
export async function copyText(text: string): Promise<boolean> {
  try {
    await navigator.clipboard.writeText(text);
    return true;
  } catch {
    return false;
  }
}

/** The glide easing shared by travelling marks (selection blocks, highlights, runs). */
export const GLIDE = "cubic-bezier(.65,0,.35,1)";

/** Base UI's className may be a function of state: merges ours with it in either form. */
export const withClass =
  <S,>(base: string, className: string | ((state: S) => string | undefined) | undefined) =>
  (state: S) =>
    cn(base, typeof className === "function" ? className(state) : className);

/** Composes two refs, keeping React 19 ref cleanups. */
export function useComposedRefs<T>(a: React.Ref<T> | undefined, b: React.Ref<T> | undefined): React.RefCallback<T> {
  return React.useCallback(
    (node: T | null) => {
      const release = [assignRef(a, node), assignRef(b, node)];
      return () => release.forEach((f) => f());
    },
    [a, b],
  );
}

/**
 * Runs each step on its own animation frame, in order (the first on the next frame), and returns one
 * cancel that stops whichever frame is pending. A no-op step just waits a frame: frames(set pre, wait,
 * go) lets the browser paint the start state before the transition begins.
 */
export function frames(...steps: (() => void)[]): () => void {
  let id = 0;
  let i = 0;
  const tick = () => {
    steps[i++]?.();
    if (i < steps.length) id = requestAnimationFrame(tick);
  };
  id = requestAnimationFrame(tick);
  return () => cancelAnimationFrame(id);
}
export const wait = () => {};

let idSeq = 0;
/** A unique id for something the user creates (a milestone, a note): random where the browser can, else a counter. */
export const newId = () => (typeof crypto !== "undefined" && "randomUUID" in crypto ? crypto.randomUUID() : `id-${Date.now()}-${++idSeq}`);

/**
 * True while an input method (Japanese, Chinese, Korean…) is composing: Enter, Tab and delimiters
 * then belong to the composition, not to the component. keyCode 229 covers Safari's late flag.
 */
export function composing(e: React.KeyboardEvent | KeyboardEvent) {
  const native = "nativeEvent" in e ? e.nativeEvent : e;
  return native.isComposing || native.keyCode === 229;
}

const hotkeyOwners = new Map<string, number[]>();
let hotkeySeq = 0;
/**
 * A page-wide shortcut ("/" or "mod+k", mod being ⌘ or Ctrl) with a single owner: when several
 * components claim the same key, only the one mounted last answers, so one press never opens two.
 * A plain key is ignored while typing in a field.
 */
export function useHotkey(combo: string | undefined, run: () => void) {
  const latest = useLatest(run);
  React.useEffect(() => {
    if (!combo) return;
    const me = ++hotkeySeq;
    const stack = hotkeyOwners.get(combo) ?? [];
    stack.push(me);
    hotkeyOwners.set(combo, stack);
    const mod = combo.startsWith("mod+");
    const key = (mod ? combo.slice(4) : combo).toLowerCase();
    const onKey = (e: KeyboardEvent) => {
      if (hotkeyOwners.get(combo)?.at(-1) !== me || e.key.toLowerCase() !== key) return;
      if (mod ? !(e.metaKey || e.ctrlKey) : e.metaKey || e.ctrlKey || e.altKey) return;
      if (!mod && (e.target as HTMLElement | null)?.closest("input, textarea, select, [contenteditable=true]")) return;
      e.preventDefault();
      latest.current();
    };
    window.addEventListener("keydown", onKey);
    return () => {
      window.removeEventListener("keydown", onKey);
      const s = hotkeyOwners.get(combo) ?? [];
      s.splice(s.indexOf(me), 1);
    };
  }, [combo, latest]);
}

/** Keeps the latest value in a ref, for callbacks read inside timers and animation frames. */
export function useLatest<T>(value: T) {
  const ref = React.useRef(value);
  React.useLayoutEffect(() => {
    ref.current = value;
  });
  return ref;
}

/*
 * Where Notchset overlays (menus, popovers, tooltips) portal to. Unset, document.body, as shadcn's
 * do. Provide an element to keep them inside a scoped theme: a preview, a widget, a shadow root.
 */
export const NotchsetPortalContext = React.createContext<HTMLElement | null>(null);
export function useNotchsetPortal(): HTMLElement | undefined {
  return React.useContext(NotchsetPortalContext) ?? undefined;
}

const subscribeNothing = () => () => {};

/**
 * A scope that turns motion or sound off for everything inside it, popups included. A plain
 * data-motion="off" wrapper can't reach a menu that portals to the body; this one also gives its
 * overlays a portal host carrying the same preferences (inside any outer scope's host), so motionOff
 * and the cues see them there too.
 */
export function NotchsetScope({ motion, sound, children, ...props }: React.ComponentProps<"div"> & { motion?: "off"; sound?: "off" }) {
  const outer = React.useContext(NotchsetPortalContext);
  const [host, setHost] = React.useState<HTMLElement | null>(null);
  const client = React.useSyncExternalStore(subscribeNothing, () => true, () => false);
  return (
    <div data-motion={motion} data-sound={sound} {...props}>
      <NotchsetPortalContext value={host ?? outer}>{children}</NotchsetPortalContext>
      {client && createPortal(<div ref={setHost} data-slot="notchset-scope-host" data-motion={motion} data-sound={sound} />, outer ?? document.body)}
    </div>
  );
}

export { NOTCHSET_ROOT, OWN_SOUND } from "@/lib/beautiful-ui/notchset/root";

// ---------------------------------------------------------------------------------------------
// Parts
// ---------------------------------------------------------------------------------------------

export type NodeState = "off" | "on" | "live" | "signal";

/** The node: a 9×9 ring whose dot blooms on (`on`), blinks (`live`) or turns signal. */
function Node({ state = "off", delay, className, style, ...props }: Omit<React.ComponentProps<"svg">, "children"> & { state?: NodeState; delay?: number }) {
  return (
    <svg
      aria-hidden
      data-slot="indicator"
      data-state={state}
      width="9"
      height="9"
      viewBox="0 0 9 9"
      className={cn(`notchset-node`, className)}
      style={delay ? ({ "--notchset-node-delay": `${delay}ms`, ...style } as React.CSSProperties) : style}
      {...props}
    >
      <circle data-slot="indicator-ring" cx="4.5" cy="4.5" r="3.25" fill="none" strokeWidth="1" />
      <circle data-slot="indicator-dot" cx="4.5" cy="4.5" />
    </svg>
  );
}

/** A small solid round mark (the node where a leader meets a popup, a pointer): SVG, round at every DPR. */
function Dot({ size = 7, className, style }: { size?: number; className?: string; style?: React.CSSProperties }) {
  return (
    <svg aria-hidden width={size} height={size} viewBox={`0 0 ${size} ${size}`} className={cn("pointer-events-none absolute overflow-visible", className)} style={style}>
      <circle cx={size / 2} cy={size / 2} r={size / 2} fill="currentColor" />
    </svg>
  );
}

/** The legend: a mono label above a control, with an optional node (or any trailing reading). */
function Legend({ label, node, children, className, ...props }: React.ComponentProps<"div"> & { label?: React.ReactNode; node?: NodeState }) {
  return (
    <div data-slot="legend" className={cn(`notchset-legend`, className)} {...props}>
      <span data-slot="legend-label">{label}</span>
      {(children != null || node) && (
        <span data-slot="legend-reading" className="flex items-center gap-2">
          {children}
          {node && <Node state={node} />}
        </span>
      )}
    </div>
  );
}

/** A key on its plate: the plate is an offset frame behind the child; `--notchset-plate-color` tints it. */
function Plated({ className, children, ...props }: React.ComponentProps<"span">) {
  return (
    <span data-slot="plated" className={cn("relative inline-flex", className)} {...props}>
      <span aria-hidden data-slot="plate" className={`notchset-plate`} />
      {children}
    </span>
  );
}

/**
 * The success check. Mounted, it traces itself in over --notchset-check (instant under reduced
 * motion); pass `drawn` to drive the trace yourself.
 */
function Check({ drawn, size = 16 }: { drawn?: boolean; size?: number }) {
  return (
    <svg aria-hidden data-slot="check" width={size} height={size} viewBox="0 0 24 24">
      <path
        d="M4 12.5 L9.5 18 L20 6"
        fill="none"
        stroke="currentColor"
        strokeWidth={1.75}
        strokeLinecap="square"
        pathLength={1}
        strokeDasharray={1}
        className={drawn === undefined ? `notchset-check-draw` : undefined}
        style={drawn === undefined ? undefined : { strokeDashoffset: drawn ? 0 : 1, transition: "stroke-dashoffset var(--notchset-check) var(--notchset-ease-travel)" }}
      />
    </svg>
  );
}

/** The scanner: five 1px ticks fading in turn while something works (static, centre lit, when motion is off). */
function Scanner({ height = 12 }: { height?: number }) {
  return (
    <span aria-hidden data-slot="scanner" className={cn(`notchset-scanner`, "inline-flex items-end gap-[2px]")} style={{ height }}>
      {[0.82, 0.66, 1, 0.66, 0.82].map((h, i) => (
        <span key={i} className="w-px bg-current" style={{ height: height * h, animationDelay: `${i * 140 - 700}ms` }} />
      ))}
    </span>
  );
}

// ---------------------------------------------------------------------------------------------
// Glyph flip: each character cycles through glyphs and lands at 110 + i·14ms, left to right
// ---------------------------------------------------------------------------------------------

const GLYPHS = "ABCDEFGHJKLMNPRSTUVWXYZ0123456789#/+=";
const STILL = new Set([" ", "·", "/", ".", ":"]);
const FLIP_CHARS = 24;

export function scramble(text: string, elapsed: number) {
  let out = "";
  for (let i = 0; i < text.length; i++) {
    const ch = text[i]!;
    // Characters past the 24th land with the 24th, so a long label flips as briefly as a short one.
    out += STILL.has(ch) || elapsed >= 110 + Math.min(i, FLIP_CHARS) * 14 ? ch : GLYPHS[(Math.floor(elapsed / 36) * 5 + i * 11) % GLYPHS.length];
  }
  return out;
}

/**
 * The text to show for `text`: when it changes, a few frames of glyphs that land left to right.
 * Runs on requestAnimationFrame only while a flip is active; the settled text is never state. Off
 * under reduced motion, inside data-motion="off" (pass the element) or with `off`.
 */
export function useGlyphFlip(text: string, { off = false, el }: { off?: boolean; el?: React.RefObject<Element | null> } = {}) {
  const [frame, setFrame] = React.useState<{ for: string; shown: string } | null>(null);
  const first = React.useRef(true);
  React.useEffect(() => {
    if (first.current) {
      first.current = false;
      return;
    }
    if (off || motionOff(el?.current)) return;
    let raf = 0;
    const t0 = performance.now();
    const end = 110 + Math.min(text.length, FLIP_CHARS) * 14 + 40;
    const step = (now: number) => {
      const elapsed = now - t0;
      if (elapsed >= end) {
        setFrame(null);
        return;
      }
      setFrame({ for: text, shown: scramble(text, elapsed) });
      raf = requestAnimationFrame(step);
    };
    raf = requestAnimationFrame(step);
    return () => cancelAnimationFrame(raf);
  }, [text, off, el]);
  // Turned off mid-flip, the label shows its text at once (the cancelled frame never lingers).
  return !off && frame && frame.for === text ? frame.shown : text;
}

/** A label that flips when its text changes; screen readers read the final text only. */
function FlipText({ children, off, className, ref: refProp, ...props }: Omit<React.ComponentProps<"span">, "children"> & { children: string; off?: boolean }) {
  const ref = React.useRef<HTMLSpanElement>(null);
  const refs = useComposedRefs<HTMLSpanElement>(refProp, ref);
  const shown = useGlyphFlip(children, { off, el: ref });
  return (
    <span {...props} ref={refs} data-slot="flip-text" className={cn("relative whitespace-nowrap", className)}>
      <span aria-hidden>{shown}</span>
      <span className="sr-only">{children}</span>
    </span>
  );
}

// ---------------------------------------------------------------------------------------------
// Sound: Notchset components announce cues; the page's beautiful-ui-sound layer (opt-in) plays them.
// ---------------------------------------------------------------------------------------------

/** The Notchset cues, in the shared sound layer's names (played in the mechanical voice). */
export const NOTCHSET_CUES = { tap: "tap", latch: "lock", signal: "destructive", confirm: "halt", done: "success", tick: "tick" } as const;
export type NotchsetCue = keyof typeof NOTCHSET_CUES;

export function playCue(el: Element | null, cue: NotchsetCue) {
  if (!el || typeof CustomEvent === "undefined" || el.closest('[data-sound="off"]')) return;
  el.dispatchEvent(new CustomEvent("beautiful-ui:sound", { bubbles: true, detail: { cue: NOTCHSET_CUES[cue] } }));
}

// ---------------------------------------------------------------------------------------------
// Shortcuts: "⌘↵" → "Meta+Enter Control+Enter" (aria-keyshortcuts)
// ---------------------------------------------------------------------------------------------

const KEY_NAMES: Record<string, string> = { "⌘": "Meta", "⌃": "Control", "⌥": "Alt", "⇧": "Shift", "↵": "Enter", "⏎": "Enter", "⎋": "Escape", "⌫": "Backspace", "⇥": "Tab", "␣": "Space" };

export function kbdToShortcut(kbd: string | undefined): string | undefined {
  if (!kbd) return undefined;
  const parts = [...kbd.replace(/\s+/g, "")].map((c) => KEY_NAMES[c] ?? c.toUpperCase());
  if (!parts.length) return undefined;
  const combo = parts.join("+");
  // ⌘ on a Mac is Ctrl elsewhere: announce both.
  return combo.includes("Meta") ? `${combo} ${combo.replace("Meta", "Control")}` : combo;
}

/**
 * Digits that roll: each digit is a 0–9 strip; the ones digit moves first and each digit to its left
 * 40ms later, counting digits only (620ms, a small overshoot). `delay` offsets the whole text. Other
 * characters (",", "$", "%", letters) sit still. Screen readers get the plain text. The one
 * implementation behind RollingNumber and the calendar's RollingLabel.
 */
export function DigitRoll({ text, height, delay = 0, className }: { text: string; height: number; delay?: number; className?: string }) {
  const chars = [...text];
  let k = 0;
  const order = chars.map((_, i) => (/\d/.test(chars[chars.length - 1 - i]!) ? k++ : 0)).reverse();
  return (
    <span className={cn("relative inline-flex flex-none overflow-hidden tabular-nums", className)} style={{ height, lineHeight: `${height}px` }}>
      <span className="sr-only">{text}</span>
      <span aria-hidden className="flex">
        {chars.map((d, i) =>
          /\d/.test(d) ? (
            <span
              key={chars.length - i}
              className="flex flex-col transition-transform duration-[620ms] ease-[cubic-bezier(.34,1.15,.5,1)] motion-reduce:transition-none"
              style={{ transform: `translateY(${-Number(d) * height}px)`, transitionDelay: `${delay + order[i]! * 40}ms` }}
            >
              {Array.from({ length: 10 }, (_, n) => (
                <span key={n} style={{ height }}>
                  {n}
                </span>
              ))}
            </span>
          ) : (
            <span key={`s${chars.length - i}`}>{d}</span>
          ),
        )}
      </span>
    </span>
  );
}

/** A number that rolls (DigitRoll at the readout's own size). `delay` offsets it (rows 60ms apart). */
function RollingNumber({ value, height = 32, delay = 0, className }: { value: string | number; height?: number; delay?: number; className?: string }) {
  return <DigitRoll text={String(value)} height={height} delay={delay} {...(className ? { className } : {})} />;
}

export { Check, Dot, FlipText, Legend, Node, Plated, RollingNumber, Scanner };
```

### lib/beautiful-ui/notchset/root.ts

```tsx
/*
 * Notchset's root attributes, server-safe (no client directive), so server components can spread
 * them too. Every Notchset root (and portalled popup) carries data-notchset (the motion policy's
 * scope), plays its own cues in the mechanical voice, and keeps the page's click layer out.
 */
export const NOTCHSET_ROOT = { "data-notchset": "", "data-sound": "none", "data-sound-voice": "analogue" } as const;

/** On every interactive element: it plays its own cues, so the page's click layer adds no tap. */
export const OWN_SOUND = { "data-sound": "none" } as const;
```

The notchset foundation (the tokens listed above, keyframes and motion levels) installs once with the first component; its CSS is public at https://notchset.dev/r/notchset-foundation.json.
