# Gauge (Lumen Halo): prompt.md (v1.0.0)
- id: `lumen-gauge` · version 1.0.0 · component · free
- category: Data
- build: Base UI (one set of files; its dependencies follow the build)
- install (this build): `npx shadcn@latest add https://beautiful-ui.dev/r/lumen-gauge.json`
- npm dependencies: none
- registry dependencies: utils, https://beautiful-ui.dev/r/lumen-foundation.json
- docs: https://beautiful-ui.dev/components/lumen-gauge
- The install command carries everything this item needs (files, CSS, tokens, npm and registry dependencies). Prefer it to copying source by hand.
A value in a known range, read as a dial of hairline ticks: ticks light to the value in the tone of its band, a longer tick marks where each band begins, and the band's word sits under the number.
## Build it
- Stack: React 19 (`ref` is a plain prop), TypeScript, Tailwind CSS v4 utilities, a shadcn-initialised project with the `@/*` alias.
- Packages: none beyond React.
- Files: `components/ui/lumen/controls/gauge.tsx`.
- Registry dependencies, installed with it automatically: shadcn `utils` (cn), `lumen-foundation`.
- Builds: one set of files for both, but its dependencies come in Base UI and Radix builds. 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: `Gauge`, and every exported type.
- CSS: the install merges this item's rules (the registry `css` field) into your global stylesheet, in `@layer components`, and adds the lumen foundation (tokens, keyframes, motion levels) 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 `--lumen-*` custom properties (`--lumen-accent`, `--lumen-accent-foreground`, `--lumen-accent-text`, `--lumen-bad`, `--lumen-bad-text`, `--lumen-chart-accent`, `--lumen-chart-accent-foreground`, `--lumen-chart-accent-text`, `--lumen-focus`, `--lumen-good`, `--lumen-good-text`, `--lumen-hairline`, `--lumen-ink`, `--lumen-muted-ink`, `--lumen-series-1`, `--lumen-series-2`, `--lumen-series-3`, `--lumen-series-4`, `--lumen-series-5`, `--lumen-series-6`, `--lumen-warn`, `--lumen-warn-text`); this item's CSS also reads `--lumen-font-sans`. Never add Tailwind colour classes inside the component.
```tsx
import { Gauge } from "@/components/ui/lumen/controls/gauge";
```
## Parts
| Part | data-slot | What it is for |
|---|---|---|
| `Gauge` | — | The meter: its dial (gauge-dial) and the number with its caption (gauge-readout). |
## 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 `GlassSoundProvider` once (install: `npx shadcn@latest add https://beautiful-ui.dev/r/glass-sound.json`, import from `@/components/beautiful-ui/glass-sound`); `GlassSoundToggle` is its mute control. Without a provider the audio engine never loads.
## Match the original
- Read `components/ui/lumen/controls/gauge.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
- gauge, dial, meter, speedometer, score, health score, CPU, latency, threshold, KPI dial
- One reading in a known range where thresholds matter: CPU, error budget, a health or credit score
- Status tiles where the zone matters more than the exact number
### Not when
- An allowance by category: use Usage Meter
- Progress toward done: use Progress
- Comparing several values: a bar chart reads better than several dials
## Mistakes
- Thresholds are where a band begins, in the gauge's own units (not 0–1)
- Give every band a word if colour carries meaning
## Usage
```tsx
"use client";
import { Gauge } from "@/components/ui/lumen/controls/gauge";
export function CpuGauge({ cpu }: { cpu: number }) {
return (
);
}
```
## Props
| Prop | Type | Default | What it does |
|---|---|---|---|
| `value` | `number` | | The reading. The dial clamps it to min–max; the number shows it as given. |
| `min / max` | `number` | `0 / 100` | The range. |
| `label` | `string` | | What is measured: the accessible name, and the caption when no band has a word. |
| `thresholds` | `{ at, tone: "neutral" \| "good" \| "warn" \| "bad", label? }[]` | `[]` | Where bands begin. Below the first, the dial is neutral ink. |
| `unit` | `string` | | After the number, e.g. "%" or "ms". |
| `format / locale` | `(v) => string / string` | | Formats the number. Default: the locale's number, up to one decimal. |
| `caption` | `ReactNode` | | Replaces the word under the number. |
| `ticks / size` | `number` | `41 / 176` | How many ticks, and the width in px. |
Full docs: https://beautiful-ui.dev/components/lumen-gauge
## Customising
- Colours: set the `--lumen-*` tokens on `:root`, or on a container with the `lumen-scope` class to retheme one area. Add the `lumen-inherit` class to follow your shadcn palette instead (`--chart-N`, `--destructive`).
- 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://beautiful-ui.dev/r/changelog.json
## Keyboard
| Keys | Action |
|---|---|
| Tab | Not focusable: it reports a reading |
## Motion inventory
| Interaction | What moves |
|---|---|
| First paint and changes | Ticks light in order from the start; reduced motion shows them at once |
## Accessibility contract (preserve when editing)
- role=meter with min, max and now; the value text adds the band's word ("72%, Busy")
- The zone is in words under the number, never colour alone
## Install
Base UI project (a base-* style in components.json):
```bash
npx shadcn@latest add https://beautiful-ui.dev/r/lumen-gauge.json
```
Radix project (a radix-*, new-york or default style):
```bash
npx shadcn@latest add https://beautiful-ui.dev/r/radix-nova/lumen-gauge.json
```
Or add the `@beautiful-ui` registry to components.json and run `npx shadcn@latest add @beautiful-ui/lumen-gauge`: the CLI picks the build from your style.
## Credits
- Built on shadcn/ui (https://ui.shadcn.com)
## Source (Base UI build)
### components/ui/lumen/controls/gauge.tsx
```tsx
"use client";
// Generated from src/registry/core/controls/gauge.tsx by scripts/gen-systems.ts. Edit the core file, not this one.
import * as React from "react";
import { cn } from "@/lib/utils";
/*
* Gauge: a value in a known range, read as a dial of hairline ticks. Ticks light up to the value, in the
* tone of the band the value is in (thresholds), and a longer tick marks where each band begins, so the
* zones ahead are readable before the value reaches them. The number sits in the middle with the band's
* word under it: the state never relies on colour alone. A meter for assistive tech.
*
*
*/
export type GaugeTone = "neutral" | "good" | "warn" | "bad";
export interface GaugeThreshold {
/** The band starts at this value (in the gauge's own range). */
at: number;
tone: GaugeTone;
/** The word under the number while the value is in this band. */
label?: string | undefined;
}
const START = 150; // degrees clockwise from 3 o'clock: the dial opens at the bottom
const SWEEP = 240;
/** The band a value falls in: the last threshold at or below it (none below the first). */
export function gaugeBand(value: number, thresholds: readonly GaugeThreshold[]): GaugeThreshold | undefined {
return [...thresholds].sort((a, b) => a.at - b.at).filter((t) => value >= t.at).pop();
}
const pt = (c: number, r: number, deg: number) => {
const a = (deg * Math.PI) / 180;
return [+(c + r * Math.cos(a)).toFixed(2), +(c + r * Math.sin(a)).toFixed(2)] as const;
};
function Gauge({
value,
min = 0,
max = 100,
label,
thresholds = [],
ticks = 41,
size = 176,
unit,
format,
locale,
caption,
className,
style,
...props
}: Omit, "children"> & {
/** The reading. Clamped to min–max for the dial; the number shows it as given. */
value: number;
min?: number;
max?: number;
/** What is measured. The accessible name, and the caption when no band has a word. */
label: string;
/** Where bands begin, with their tone and word. Below the first: neutral. */
thresholds?: readonly GaugeThreshold[];
/** How many ticks draw the dial. Default 41. */
ticks?: number;
/** Width in px. Default 176. */
size?: number;
/** After the number, e.g. "%" or "ms". */
unit?: string | undefined;
/** Formats the number. Default: the locale's number, up to one decimal. */
format?: ((value: number) => string) | undefined;
locale?: string | undefined;
/** Replaces the word under the number. */
caption?: React.ReactNode;
}) {
const span = max - min || 1;
const clamped = Math.min(max, Math.max(min, Number.isFinite(value) ? value : min));
const t = (clamped - min) / span;
const band = gaugeBand(clamped, thresholds);
const tone: GaugeTone = band?.tone ?? "neutral";
const fmt = format ?? ((v: number) => new Intl.NumberFormat(locale, { maximumFractionDigits: 1 }).format(v));
const text = `${fmt(value)}${unit ? (unit === "%" ? "%" : ` ${unit}`) : ""}`;
// Numeric props from config or a CMS can be anything: keep the dial drawable.
const n = Number.isFinite(ticks) ? Math.max(2, Math.min(120, Math.round(ticks))) : 41;
const dial = Number.isFinite(size) && size >= 48 ? size : 176;
const c = dial / 2;
const outer = c - 2;
const len = Math.max(6, dial * 0.065);
const lit = Math.round(t * (n - 1));
// Ticks where a band begins are drawn longer.
const edges = new Set(thresholds.filter((th) => th.at > min && th.at < max).map((th) => Math.round(((th.at - min) / span) * (n - 1))));
const height = Math.ceil(c + outer * Math.sin((START * Math.PI) / 180) + 4);
return (