# UiScreenDescription

> Talos 0.6 · Since 0.6

A whole screen, as `ctx.ui.screen` takes it.

## Signature

```ts
export interface UiScreenDescription {
  /** The contract version. Always 1. */
  format: 1
  /** The screen's name, as `push`, `replace` and `GET /ui/screens` use it. */
  screen: string
  root: UiNode
}
```

Import: `import type { UiScreenDescription } from "@argus/api"`

## Members

| Member | Signature | Description |
|---|---|---|
| `format` | `format: 1` | The contract version. Always 1. |
| `screen` | `screen: string` | The screen's name, as `push`, `replace` and `GET /ui/screens` use it. |
| `root` | `root: UiNode` |  |

## Example

The tested fixture `fixtures/recipes/hud-score-timer/scenes/behaviors/hud-score-timer.ts`.

```ts
import type { Behavior } from "@argus/api"

/**
 * A score and a countdown on the stock HUD.
 *
 * Space scores a point, the clock runs down from `seconds`, and at zero the round emits
 * `time-up` once and stops.
 *
 * How a number reads is the scene's business, not this file's: `meta.hud.timer` says
 * `format: "time"` so 29.5 draws as `0:30`, and `meta.hud.score` adds the `Score ` prefix.
 * Without those entries a number draws raw, as `timer: 29.5`. Writing both every tick is
 * fine — an unchanged HUD value costs nothing.
 */
interface State {
  score: number
  /** Seconds left in the round. */
  left: number
  over: boolean
}

interface Props {
  /** Length of the round in seconds. Default 30. */
  seconds?: number
}

export default {
  init(ctx) {
    if (typeof ctx.state.score !== "number") ctx.state.score = 0
    if (typeof ctx.state.left !== "number") ctx.state.left = ctx.props.seconds ?? 30
    if (typeof ctx.state.over !== "boolean") ctx.state.over = false
  },

  update(ctx, dt) {
    if (!ctx.state.over) {
      if (ctx.input !== null && ctx.input.pressed("score")) ctx.state.score += 1
      ctx.state.left = Math.max(0, ctx.state.left - dt)
      if (ctx.state.left === 0) {
        ctx.state.over = true
        ctx.events.emit("time-up", { score: ctx.state.score })
      }
    }
    ctx.hud.score(ctx.state.score)
    ctx.hud.timer(ctx.state.left)
  },
} satisfies Behavior<State, Props>
```