# LegendLayer.attach

## Summary
LegendLayer.attach builds and mounts the legend container, gradient canvas, and tick label nodes under the overlay root. This is typically called by `OverlaySystem.addLayer`.

## Syntax
```ts
LegendLayer.attach(root: HTMLDivElement): void
layer.attach(root);
```

## Parameters
| Name | Type | Required | Description |
| --- | --- | --- | --- |
| `root` | `HTMLDivElement` | Yes | Overlay root container for legend DOM content. |

## Returns
`void` - No return value.

## Type Details
```ts
// No additional descriptor expansion is required for this signature.
```

## Example
```js
const canvas = document.querySelector("canvas");
const wgpu = await WasmGPU.create(canvas);

const overlay = wgpu.createOverlay.system();
const legend = wgpu.createOverlay.legend({
    source: { scaleTransform: { mode: "linear", domainMin: 0, domainMax: 1 }, colormap: "viridis" }
});
overlay.addLayer(legend); // attach called internally
```

## See Also
- [LegendLayer.detach](./wasmgpu-world-legendlayer-detach.md)
- [LegendLayer.update](./wasmgpu-world-legendlayer-update.md)
- [OverlaySystem.addLayer](./wasmgpu-world-overlaysystem-addlayer.md)