# Tooltip

> A short description that shows up beside an element on hover and focus.

`<slab-tooltip>` · Overlays · built on `[role=tooltip]`

## Install

```sh
pnpm add slab-elements lit
```

## Usage

```html
<script type="module">
  import 'slab-elements/tooltip.js';
</script>

<slab-tooltip>
  <button slot="anchor">Save</button>
  <span>Saves a copy to your account</span>
</slab-tooltip>
```

## Example

Here's a styled version, `<slab-styled-tooltip>`. It's not in the package — it's an example of what you can build with the headless element. Copy it and make it yours at the bottom of this page.

```html
<slab-styled-tooltip placement="right">
  <button class="styled-button styled-button--icon" slot="anchor" type="button" aria-label="About slump">?</button>
  <span>Slump is how far a cone of fresh concrete sags. 4 inches is typical for a slab.</span>
</slab-styled-tooltip>
```

Swap `slab-styled-` for `slab-` in that markup and you've got the same example as it ships: the headless elements with no CSS at all. That's your starting point.

## Keyboard

| Key    | What it does                                                                  |
| ------ | ----------------------------------------------------------------------------- |
| Tab    | Focusing the anchor opens the tooltip at once. Leaving it closes the tooltip. |
| Escape | Closes the tooltip.                                                           |

## Behavior

A tooltip with no visual styles: `[role=tooltip]` content, shown in the top layer beside the element slotted as its `anchor`.

It opens when the anchor is hovered, after `open-delay`, and at once when the anchor is focused. It closes when the pointer leaves, after `close-delay`, when the anchor loses focus, and on Escape. The pointer can cross from the anchor onto the tooltip without it closing, so its content can be read at any zoom, which is what WCAG 1.4.13 asks of content shown on hover.

The anchor is described by the tooltip's content. ARIA references can't cross a shadow root, so the content is slotted rather than rendered: it stays in the anchor's tree, and the anchor's `aria-describedby` points at it.

It's placed beside its anchor with CSS anchor positioning, as Popover is, and flipped when it would leave the screen. `placement` picks the side and nothing else: the gap, the alignment, and every other visual choice are left to `::part(tooltip)`. Where anchor positioning isn't supported, the tooltip falls back to the browser's centering.

Style it through its `tooltip` part and `:state(open)`.

## API

### `<slab-tooltip>`

#### Attributes

| Name | Type | Default | Description |
| --- | --- | --- | --- |
| `close-delay` | `number` | `200` |  |
| `disabled` | `boolean` | `false` | The tooltip doesn't open and doesn't describe its anchor. |
| `open-delay` | `number` | `300` |  |
| `open` | `boolean` | `false` |  |
| `placement` | `'bottom' \| 'left' \| 'right' \| 'top'` | `'bottom'` | The side of its anchor it opens on, when there's room. It flips when there isn't. |
| `version` | `string` |  |  |

#### Events

| Name | Type | Description |
| --- | --- | --- |
| `toggle` | `Event` |  |

#### Slots

| Name | Type | Description |
| --- | --- | --- |
| `anchor` | `Element` | The element the tooltip is for. It should be one that can be focused. |
| `(default)` | `Element` | The tooltip's content, which describes the anchor |

#### CSS parts

| Name | Description |
| --- | --- |
| `tooltip` |  |

## Copy and own it

`<slab-styled-tooltip>` isn't in the package. It's an example — copy it into your project and change whatever you want. Under the hood, it's just the headless element, subclassed, with `styles` set. That's it. Keyboard, focus, ARIA, forms, and events all come from the headless element, and the styles only reach in through `::part()` and `:state()`, same as yours would.

To use it, copy these files, swap the tag in `@customElement()` for one of your own, and import it. `tokens.styles.ts` holds the colors and fonts every styled example shares, so you only need it once.

### TypeScript

These files are TypeScript, and `@customElement()` is one of Lit's decorators (TypeScript's experimental flavor). You'll need two options in your tsconfig, per [Lit's docs](https://lit.dev/docs/components/decorators/#decorators-typescript): `experimentalDecorators` to compile them, and `useDefineForClassFields` turned off so class fields don't stomp on the accessors Lit sets up.

```json
{
  "compilerOptions": {
    "experimentalDecorators": true,
    "useDefineForClassFields": false
  }
}
```

Using plain JavaScript? Drop the types and register the class with `customElements.define()` instead of the decorator.

### tooltip.ts

```ts
import { customElement } from 'lit/decorators.js';
import Tooltip from 'slab-elements/tooltip.js';
import styles from './tooltip.styles.js';
import tokens from './tokens.styles.js';

declare global {
  interface HTMLElementTagNameMap {
    'slab-styled-tooltip': StyledTooltip;
  }
}

/**
 * Tooltip, styled: a small block of paper-on-ink monospace with an ember
 * shadow.
 */
@customElement('slab-styled-tooltip')
export default class StyledTooltip extends Tooltip {
  static override styles = [tokens, styles];
}
```

### tooltip.styles.ts

```ts
import { css } from 'lit';

export default css`
  /* A closed tooltip isn't displayed, so this runs each time it opens. */
  [part~='tooltip'] {
    animation: fade 120ms ease-out;
    background-color: var(--ink);
    border: 0;
    box-shadow: 3px 3px 0 var(--ember);
    color: var(--paper);
    font-family: var(--font-mono);
    font-size: 0.8125rem;
    line-height: 1.4;
    margin: 0.625rem;
    max-inline-size: 18rem;
    padding: 0.5rem 0.75rem;
  }

  @keyframes fade {
    from {
      opacity: 0;
    }
  }

  @media (prefers-reduced-motion: reduce) {
    [part~='tooltip'] {
      animation: none;
    }
  }
`;
```

### tokens.styles.ts

```ts
import { css } from 'lit';

/*
  The styled components' palette and type, taken from the logo: ink for the
  courses, ember for the base, paper behind them.

  Each is a short alias for a "--slab-styled-*" property, with the default as
  its fallback. Retheming is "--slab-styled-ember" and the rest on ":root",
  which every shadow root inherits. Were the defaults declared under those
  names here instead, each host's own declaration would shadow the page's.

  Each default is "light-dark()", so the components follow the page's
  "color-scheme": "dark" for dark, "light" for light, and "light dark" to
  follow the operating system. Ink and paper trade places in the dark, so
  ink is always the text and paper always what's behind it. Contrast is given
  as light, then dark.
*/
export default css`
  :host {
    /* Secondary text. 6.8:1 and 6.9:1 on paper. */
    --ash: var(--slab-styled-ash, light-dark(#5e5a55, #a8a19a));
    --border: 2px solid var(--ink);

    /* Behind disabled and read-only controls, and hovered rows. */
    --chalk: var(--slab-styled-chalk, light-dark(#f4f1ec, #2b2926));

    /*
      The logo's orange, brighter in the dark. 4.25:1 and 5.2:1 on paper is
      enough for borders, fills and large text, but not always for small text,
      which takes "--ember-deep".
    */
    --ember: var(--slab-styled-ember, light-dark(#d9492a, #ec5f3b));

    /*
      Orange for small text on paper, and for paper text on it. 5.7:1 and
      7.4:1.
    */
    --ember-deep: var(--slab-styled-ember-deep, light-dark(#b3381a, #ff8566));
    --font-body: var(
      --slab-styled-font-body,
      'IBM Plex Sans',
      system-ui,
      sans-serif
    );
    --font-display: var(
      --slab-styled-font-display,
      'Zilla Slab',
      rockwell,
      'Roboto Slab',
      serif
    );
    --font-mono: var(
      --slab-styled-font-mono,
      'IBM Plex Mono',
      ui-monospace,
      monospace
    );
    --ink: var(--slab-styled-ink, light-dark(#1c1c1c, #f4f1ec));
    --paper: var(--slab-styled-paper, light-dark(#fff, #1a1918));

    /* The hard, offset shadow a raised surface casts. */
    --shadow: 4px 4px 0 var(--ink);
  }
`;
```