# react-dvd-screensaver

> DVD screensaver bouncing animation hook for React. Zero dependencies, fully typed, SSR-safe (Next.js App Router compatible), supports React 16 through 19.

## Install

```
npm i react-dvd-screensaver
# or
pnpm add react-dvd-screensaver
```

## Quick start

```tsx
import { useDvdScreensaver } from 'react-dvd-screensaver';

function MyComponent() {
  const { containerRef, elementRef, impactCount } = useDvdScreensaver({ speed: 3 });

  return (
    <div ref={containerRef} style={{ position: 'relative', width: '100%', height: '400px' }}>
      <div ref={elementRef} style={{ position: 'absolute', top: 0, left: 0 }}>
        <MyLogo />
      </div>
    </div>
  );
}
```

**Required CSS:** The container must have `position: relative` (or `absolute` / `fixed`) to establish a positioning context. The animated element must have `position: absolute; top: 0; left: 0` as its starting point.

## API

### `useDvdScreensaver(options?): UseDvdScreensaver`

**Options**

| Option | Type | Default | Description |
|---|---|---|---|
| `speed` | `number` | `2` | Speed in pixels per frame at 60 fps. Time-based internally, so consistent across 60/90/120 Hz displays. |
| `freezeOnHover` | `boolean` | `false` | Pause the animation on mouse hover or touch. |
| `paused` | `boolean` | `false` | Programmatically pause and resume the animation. |
| `impactCallback` | `(count: number) => void` | — | Called on each boundary hit with the running total impact count. |
| `onCornerHit` | `() => void` | — | Called when the element hits two boundaries simultaneously (a corner). |
| `hoverCallback` | `() => void` | — | Called when hover or touch begins on the element. |

**Return values**

| Property | Type | Description |
|---|---|---|
| `containerRef` | `RefObject<T>` | Attach to the container element. Falls back to `parentElement` if not provided. |
| `elementRef` | `RefObject<T>` | Attach to the element that should animate. |
| `hovered` | `boolean` | `true` while the element is hovered or touched. |
| `impactCount` | `number` | Running total of boundary impacts (reactive). |

The hook is generic: `useDvdScreensaver<HTMLDivElement>()` — default is `HTMLDivElement`.

## Examples

### Change color on every impact

```tsx
const COLORS = ['#ff4081', '#7c4dff', '#00bcd4', '#69f0ae'];

function MyComponent() {
  const [color, setColor] = useState(COLORS[0]);

  const { containerRef, elementRef } = useDvdScreensaver({
    impactCallback: (count) => setColor(COLORS[count % COLORS.length]),
  });

  return (
    <div ref={containerRef} style={{ position: 'relative', width: '100%', height: '400px' }}>
      <div ref={elementRef} style={{ position: 'absolute', top: 0, left: 0 }}>
        <MyLogo fill={color} />
      </div>
    </div>
  );
}
```

### Pause and resume

```tsx
function MyComponent() {
  const [paused, setPaused] = useState(false);
  const { containerRef, elementRef } = useDvdScreensaver({ paused });

  return (
    <>
      <div ref={containerRef} style={{ position: 'relative', width: '100%', height: '400px' }}>
        <div ref={elementRef} style={{ position: 'absolute', top: 0, left: 0 }}>
          <MyLogo />
        </div>
      </div>
      <button onClick={() => setPaused((p) => !p)}>{paused ? 'Resume' : 'Pause'}</button>
    </>
  );
}
```

### Corner hit detection

```tsx
function MyComponent() {
  const { containerRef, elementRef } = useDvdScreensaver({
    onCornerHit: () => console.log('Corner hit!'),
  });
  // ...
}
```

### Freeze on hover

```tsx
function MyComponent() {
  const { containerRef, elementRef, hovered } = useDvdScreensaver({ freezeOnHover: true });

  return (
    <div ref={containerRef} style={{ position: 'relative', width: '100%', height: '400px' }}>
      <div ref={elementRef} style={{ position: 'absolute', top: 0, left: 0, opacity: hovered ? 0.5 : 1 }}>
        <MyLogo />
      </div>
    </div>
  );
}
```

### Next.js App Router

Add the `'use client'` directive. The hook is SSR-safe and will not cause hydration mismatches.

```tsx
'use client';

import { useDvdScreensaver } from 'react-dvd-screensaver';

export default function ScreensaverPage() {
  const { containerRef, elementRef } = useDvdScreensaver({ speed: 3 });

  return (
    <div ref={containerRef} style={{ position: 'relative', width: '100%', height: '100vh' }}>
      <div ref={elementRef} style={{ position: 'absolute', top: 0, left: 0 }}>
        <MyLogo />
      </div>
    </div>
  );
}
```

## Notes

- Respects the OS `prefers-reduced-motion` accessibility setting — animation stops automatically when enabled.
- Uses `requestAnimationFrame` with a time-based delta so speed is consistent across 60 Hz, 90 Hz, and 120 Hz displays.
- Uses `ResizeObserver` to clamp the element position when the container resizes.
- Touch events are registered as passive listeners to avoid blocking page scroll.
- `containerRef` is optional — if omitted, `parentElement` is used as the bounding container.
- Zero runtime dependencies; peer dependency is React ≥ 16.3.

## License

MIT