Keep your phone close to the one you want to pair.
{devices.map((device) => (
{device.name}{device.rssi} dBm
))}
);
}
```
## API reference
### Radar
Renders a div with role="img" and accepts its attributes; the ref points at it.
| Prop | Type | Default | Description |
| --- | --- | --- | --- |
| `blips` | `RadarBlip[]` | `[]` | Contacts on the scope. |
| `speed` | `number` | `4` | Seconds per revolution. |
| `rings` | `number` | `4` | Range rings, evenly spaced. |
| `size` | `"sm" \| "md" \| "lg" \| number` | `"md"` | 200, 280 or 360px across, or a diameter in pixels. It stays square and shrinks to fit a narrower container; a w-* class also works. |
| `label` | `string` | `"Radar"` | Accessible name. The contact count and labeled contacts are appended. |
| `color` | `NeonColor` | `inherited` | Phosphor color. Falls back to --neon-accent, then cyan. |
### RadarBlip
| Prop | Type | Default | Description |
| --- | --- | --- | --- |
| `angle` | `number` | — | Bearing in degrees, clockwise from the top. |
| `distance` | `number` | — | Distance from the center, 0 to 1. |
| `label` | `string` | — | Short tag beside the blip, also read to screen readers. |
| `color` | `NeonColor` | — | This blip's color. Defaults to the radar's. |
## Accessibility
- The scope is one image to screen readers, named like "Approach radar: 5 contacts. BAW 117 at bearing 038, 62% range…". Pass aria-label to replace it.
- Everything moves with CSS animations on transform and opacity, so there is no per-frame JavaScript. The blips' clocks are pinned to the sweep's in an effect.
- With reduced motion, the beam stops at a fixed bearing and each blip holds the brightness it would have at that point in the sweep.
## Source
`components/ui/radar.tsx`
```tsx
"use client";
import * as React from "react";
import { cn } from "@/lib/utils";
import { neonVars, toNeonRgb, type NeonColor } from "@/lib/neon";
// Blips flare when the beam crosses them and decay until the next pass. The
// blip clocks are pinned to the sweep's clock in an effect, so they stay in step.
const css = `
@keyframes nk-radar-sweep { to { transform: rotate(360deg); } }
@keyframes nk-radar-blip { 0% { opacity: 1; } 10% { opacity: 0.9; } 40% { opacity: 0.42; } 75% { opacity: 0.16; } 100% { opacity: 0.06; } }
@keyframes nk-radar-flare { 0% { transform: scale(1.9); } 12%, 100% { transform: scale(1); } }
@keyframes nk-radar-ping { 0% { opacity: 0.85; transform: scale(0.15); } 22%, 100% { opacity: 0; transform: scale(1); } }
.nk-radar-sweep { transform: rotate(var(--nk-radar-still)); }
.nk-radar-blip { opacity: 0; }
.nk-radar-ping { opacity: 0; }
[data-live] .nk-radar-sweep { animation: nk-radar-sweep var(--nk-radar-period) linear infinite; }
[data-live] .nk-radar-blip { animation: nk-radar-blip var(--nk-radar-period) linear infinite; }
[data-live] .nk-radar-dot { animation: nk-radar-flare var(--nk-radar-period) ease-out infinite; }
[data-live] .nk-radar-ping { animation: nk-radar-ping var(--nk-radar-period) cubic-bezier(0.23, 1, 0.32, 1) infinite; }
@media (prefers-reduced-motion: reduce) {
[data-live] .nk-radar-sweep, [data-live] .nk-radar-blip, [data-live] .nk-radar-dot, [data-live] .nk-radar-ping { animation: none; }
.nk-radar-blip { opacity: var(--nk-radar-rest); }
}
`;
// Width only: aspect-square sets the height, and max-w-full lets it shrink in a narrow container.
const sizes = { sm: "w-[200px]", md: "w-[280px]", lg: "w-[360px]" } as const;
// Layout effect on the client so the sweep never paints a frame out of step.
const useIsomorphicLayoutEffect = typeof window === "undefined" ? React.useEffect : React.useLayoutEffect;
// Where the beam rests when motion is reduced, and how bright each blip looks
// for its distance behind it (the same curve as the decay keyframes).
const STILL = 58;
const curve: [number, number][] = [
[0, 1],
[0.1, 0.9],
[0.4, 0.42],
[0.75, 0.16],
[1, 0.06],
];
function restingOpacity(angle: number) {
const age = ((((STILL - angle) % 360) + 360) % 360) / 360;
for (let i = 1; i < curve.length; i++) {
const [x1, y1] = curve[i];
const [x0, y0] = curve[i - 1];
if (age <= x1) return y0 + ((age - x0) / (x1 - x0)) * (y1 - y0);
}
return 0.06;
}
// Trig results can differ in the last bit between the server's and the browser's
// engine, so anything rendered from them is rounded first to hydrate cleanly.
const fix = (value: number) => value.toFixed(3);
const bearing = (angle: number) => String(Math.round(((angle % 360) + 360) % 360)).padStart(3, "0");
export interface RadarBlip {
/** Bearing in degrees, clockwise from the top. */
angle: number;
/** Distance from the center, 0 to 1. */
distance: number;
/** Short tag drawn beside the blip and read to screen readers. */
label?: string;
/** Palette name or hex for this blip. Defaults to the radar's color. */
color?: NeonColor;
}
export interface RadarProps
extends Omit, "color"> {
/** Contacts on the scope. */
blips?: RadarBlip[];
/** Seconds per revolution. */
speed?: number;
/** Range rings. */
rings?: number;
/** Named size, or a diameter in pixels. */
size?: keyof typeof sizes | number;
/** Accessible name. The contacts are appended to it. */
label?: string;
/** Phosphor color. Inherits `--neon-accent` when omitted. */
color?: NeonColor;
}
const Radar = React.forwardRef(
(
{
className,
style,
color,
blips = [],
speed = 4,
rings = 4,
size = "md",
label = "Radar",
...props
},
ref,
) => {
const rootRef = React.useRef(null);
const sweepRef = React.useRef(null);
const born = React.useRef(new WeakMap());
const period = Math.max(0.5, speed) * 1000;
const ringCount = Math.max(1, Math.round(rings));
React.useImperativeHandle(ref, () => rootRef.current as HTMLDivElement);
const signature = blips.map((blip) => blip.angle).join(",");
useIsomorphicLayoutEffect(() => {
const root = rootRef.current;
if (!root) return;
root.setAttribute("data-live", "");
const now = Number(document.timeline?.currentTime ?? performance.now());
// The sweep's clock starts at the timeline's origin, so its angle is a pure function of time.
for (const animation of sweepRef.current?.getAnimations?.() ?? []) animation.startTime = 0;
root.querySelectorAll("[data-radar-blip]").forEach((node) => {
const angle = Number(node.dataset.angle) || 0;
if (!born.current.has(node)) born.current.set(node, now);
const offset = ((((angle % 360) + 360) % 360) / 360) * period;
// The most recent pass over this bearing; a new contact waits for the next one.
let start = offset + Math.floor((now - offset) / period) * period;
if (start < (born.current.get(node) ?? now)) start += period;
for (const animation of node.getAnimations?.({ subtree: true }) ?? []) animation.startTime = start;
});
}, [period, signature]);
const named = typeof size === "number";
const contacts = blips.length;
const summary = [
`${label}: ${contacts} ${contacts === 1 ? "contact" : "contacts"}`,
...blips
.filter((blip) => blip.label)
.map((blip) => `${blip.label} at bearing ${bearing(blip.angle)}, ${Math.round(blip.distance * 100)}% range`),
].join(". ");
const ticks = Array.from({ length: 72 }, (_, i) => i * 5);
return (
{/* The bezel: an engraved compass ring. */}
{/* The scope face. */}
{blips.map((blip, i) => {
const rad = (blip.angle * Math.PI) / 180;
const reach = Math.min(1, Math.max(0, blip.distance)) * 48;
// Labels sit to the right, or to the left near the right rim so the glass doesn't clip them.
const flip = Math.sin(rad) * reach > 12;
return (
{blip.label && (
{blip.label}
)}
);
})}
{/* Curved glass. */}