svelte-kit-vice/src/uix/soma/components/dropdown-menu/README.md

# DropdownMenu

A menu of actions triggered by a button. Supports submenus, checkbox items, radio groups, keyboard navigation, and typeahead.

## Anatomy

```svelte
<DropdownMenu.Provider bind:open>
	<DropdownMenu.Trigger>Actions</DropdownMenu.Trigger>

	<DropdownMenu.Content>
		<DropdownMenu.Item>Cut</DropdownMenu.Item>
		<DropdownMenu.Item>Copy</DropdownMenu.Item>
		<DropdownMenu.Separator />

		<DropdownMenu.CheckboxItem bind:checked>Show Toolbar</DropdownMenu.CheckboxItem>

		<DropdownMenu.RadioGroup bind:value>
			<DropdownMenu.RadioItem value="light">Light</DropdownMenu.RadioItem>
			<DropdownMenu.RadioItem value="dark">Dark</DropdownMenu.RadioItem>
		</DropdownMenu.RadioGroup>

		<DropdownMenu.Sub bind:open={subOpen}>
			<DropdownMenu.SubTrigger>More</DropdownMenu.SubTrigger>
			<DropdownMenu.SubContent>
				<DropdownMenu.Item>Submenu Item</DropdownMenu.Item>
			</DropdownMenu.SubContent>
		</DropdownMenu.Sub>
	</DropdownMenu.Content>
</DropdownMenu.Provider>
```

## Parts

| Part           | Element    | Description                                                  |
| -------------- | ---------- | ------------------------------------------------------------ |
| `Provider`     | none       | Root context. Manages open state.                            |
| `Trigger`      | `<button>` | Opens the menu on click or keyboard.                         |
| `Content`      | `<div>`    | Menu container. Focus scope, dismissal, floating integrated. |
| `Arrow`        | `<div>`    | Floating arrow pointing toward the trigger.                  |
| `Item`         | `<div>`    | Action item. Selectable via click or keyboard.               |
| `Group`        | `<div>`    | Groups related items with an optional heading.               |
| `GroupHeading` | `<div>`    | Label for a group, linked via `aria-labelledby`.             |
| `Separator`    | `<div>`    | Visual separator between items or groups.                    |
| `CheckboxItem` | `<div>`    | Toggleable item with checked/unchecked state.                |
| `CheckboxGroup` | none      | Optional parent. Binds `value: string[]` and flips checked state of child `CheckboxItem`s by their `value`. |
| `RadioGroup`   | `<div>`    | Group of mutually exclusive radio items.                     |
| `RadioItem`    | `<div>`    | Radio option within a RadioGroup.                            |
| `Sub`          | none       | Submenu context. Manages submenu open state.                 |
| `SubTrigger`   | `<div>`    | Opens a submenu on hover or keyboard.                        |
| `SubContent`   | `<div>`    | Submenu container. Positioned relative to SubTrigger.        |

## ARIA

| Part         | Attribute          | Value              |
| ------------ | ------------------ | ------------------ |
| Trigger      | `aria-haspopup`    | `menu`             |
| Trigger      | `aria-expanded`    | `true` \| `false`  |
| Trigger      | `aria-controls`    | ID of Content      |
| Content      | `role`             | `menu`             |
| Content      | `aria-orientation` | `vertical`         |
| Item         | `role`             | `menuitem`         |
| CheckboxItem | `role`             | `menuitemcheckbox` |
| CheckboxItem | `aria-checked`     | `true` \| `false`  |
| RadioGroup   | `role`             | `group`            |
| RadioItem    | `role`             | `menuitemradio`    |
| RadioItem    | `aria-checked`     | `true` \| `false`  |
| Group        | `role`             | `group`            |
| Group        | `aria-labelledby`  | ID of GroupHeading |
| Separator    | `role`             | `separator`        |
| Separator    | `aria-orientation` | `horizontal`       |
| SubTrigger   | `role`             | `menuitem`         |
| SubTrigger   | `aria-haspopup`    | `menu`             |
| SubTrigger   | `aria-expanded`    | `true` \| `false`  |
| SubTrigger   | `aria-controls`    | ID of SubContent   |
| SubContent   | `role`             | `menu`             |
| SubContent   | `aria-orientation` | `vertical`         |

## Data Attributes

| Part         | Attribute                          | Values                                 |
| ------------ | ---------------------------------- | -------------------------------------- |
| Trigger      | `data-dropdown-menu-trigger`       | Always present                         |
| Trigger      | `data-state`                       | `open` \| `closed`                     |
| Content      | `data-dropdown-menu-content`       | Always present                         |
| Content      | `data-state`                       | `open` \| `closed`                     |
| Content      | `data-side`                        | `top` \| `right` \| `bottom` \| `left` |
| Content      | `data-align`                       | `start` \| `center` \| `end`           |
| Content      | `data-starting-style`              | Present during open animation          |
| Content      | `data-ending-style`                | Present during close animation         |
| Item         | `data-dropdown-menu-item`          | Always present                         |
| Item         | `data-disabled`                    | Present when disabled                  |
| Item         | `data-text-value`                  | Text content for typeahead             |
| CheckboxItem | `data-dropdown-menu-checkbox-item` | Always present                         |
| CheckboxItem | `data-state`                       | `checked` \| `unchecked`               |
| CheckboxItem | `data-disabled`                    | Present when disabled                  |
| RadioItem    | `data-dropdown-menu-radio-item`    | Always present                         |
| RadioItem    | `data-state`                       | `checked` \| `unchecked`               |
| RadioItem    | `data-disabled`                    | Present when disabled                  |
| SubTrigger   | `data-dropdown-menu-sub-trigger`   | Always present                         |
| SubTrigger   | `data-state`                       | `open` \| `closed`                     |
| SubTrigger   | `data-disabled`                    | Present when disabled                  |
| SubContent   | `data-dropdown-menu-sub-content`   | Always present                         |
| SubContent   | `data-state`                       | `open` \| `closed`                     |
| Separator    | `data-dropdown-menu-separator`     | Always present                         |

## Keyboard

### On Trigger

| Key                             | Action                      |
| ------------------------------- | --------------------------- |
| `ArrowDown` / `Enter` / `Space` | Open menu, focus first item |

### On Content

| Key               | Action                            |
| ----------------- | --------------------------------- |
| `ArrowDown`       | Move to next item                 |
| `ArrowUp`         | Move to previous item             |
| `Home`            | Move to first item                |
| `End`             | Move to last item                 |
| `Enter` / `Space` | Activate focused item             |
| `Escape`          | Close menu                        |
| Character keys    | Typeahead — jump to matching item |

### On SubTrigger

| Key                | Action       |
| ------------------ | ------------ |
| `ArrowRight` (LTR) | Open submenu |
| `Enter` / `Space`  | Open submenu |

### On SubContent

| Key                          | Action                          |
| ---------------------------- | ------------------------------- |
| `ArrowLeft` (LTR) / `Escape` | Close submenu, focus SubTrigger |
| `ArrowDown` / `ArrowUp`      | Navigate items within submenu   |

## Motion — item cascade (opt-in)

`<DropdownMenu.Provider animation="cascade-slide">` (a `CoordinatedPresetName` — `cascade-slide` /
`-fade` / `-scale`) staggers the menu **rows** in on open and out on close. Omitted ⇒ the menu uses
its plain panel chrome, unchanged.

This is the motion service's **children-DOM coordination mode** (RFC §M9 / Apéndice C). The Content
is the owner `Presence`; its rows are static DOM, so there is no per-row `Presence` to coordinate.
Instead a `DomCascade` (`soma/layers/dom-cascade.svelte.ts`) propagates the owner's lifecycle onto
each row — it writes `data-animation-style` + the mirrored `data-starting/ending-style` +
`--motion-stagger-index`/`-count` over `getCascadeRows()` (every visible row incl. disabled), so the
generated `cascade-*` preset just works. On close the owner holds the panel until the exit cascade
settles (`pending`). The morfo declares it: the `content` part carries
`animation: { surface: true, staggerChildren: 'item' }`.

When `animation` is set the provider also stamps `data-cascade` on the content so eidos can suppress
the panel's OWN signature (`dismiss-fade`) — otherwise the panel fades whole, taking the rows
cascading inside it, before the stagger finishes. Full design + the coexistence fixes (transition
collision, disabled opacity, dismiss-fade, the trigger/dismissal toggle) are in
[RFC Apéndice C](../../../eidos/MOTION_SERVICE_RFC.md#apéndice-c--m9-el-modo-children-dom-la-segunda-coordinación).

## Sema events

| Event           | Family   | Verb     | Target    | Intent   | Sequence | When                                              |
| --------------- | -------- | -------- | --------- | -------- | -------- | ------------------------------------------------- |
| `open`          | `emerge` | `open`   | `content` | —        | `pre`    | Menu opens (`handleOpen` central state mutator).  |
| `close`         | `emerge` | `close`  | `content` | —        | `pre`    | Menu closes (`handleClose`).                       |
| `commit-select` | `commit` | `select` | `item`    | `affirm` | `post`   | User activates an item (mouse click or keyboard). |

`open` / `close` use sequence `pre` so the perceptual signal lands at the gesture moment, before the structural flip (the content is still in DOM, the cascade matches `[data-dropdown-menu-content]`). `commit-select` fires from MenuItem `onclick` and `onkeydown` with `e.currentTarget` as fallback target.

**Pack**: [`src/uix/sema/components/dropdown-menu.ts`](../../../sema/components/dropdown-menu.ts):
- `open` → `emerge.soft` (soft chime, gain 0.08).
- `close` → `emerge.exit.soft` (descending pitch + gain 0.05).
- `commit-select` → `form.commit.subtle` + light `tap` haptic. Softer than radio-group because close-emerge + select-commit + downstream-surface fire in quick succession; spreading intensity avoids double-tap fatigue.

## Usage

### Basic

```svelte
<script>
	import { DropdownMenu } from '$soma/components';

	let open = $state(false);
</script>

<DropdownMenu.Provider bind:open>
	<DropdownMenu.Trigger>Options</DropdownMenu.Trigger>

	<DropdownMenu.Content>
		<DropdownMenu.Item>Edit</DropdownMenu.Item>
		<DropdownMenu.Item>Duplicate</DropdownMenu.Item>
		<DropdownMenu.Separator />
		<DropdownMenu.Item>Delete</DropdownMenu.Item>
	</DropdownMenu.Content>
</DropdownMenu.Provider>
```

### Checkbox item

```svelte
<script>
	let showToolbar = $state(true);
</script>

<DropdownMenu.CheckboxItem bind:checked={showToolbar}>Show Toolbar</DropdownMenu.CheckboxItem>
```

### Radio group

```svelte
<script>
	let theme = $state('light');
</script>

<DropdownMenu.RadioGroup bind:value={theme}>
	<DropdownMenu.RadioItem value="light">Light</DropdownMenu.RadioItem>
	<DropdownMenu.RadioItem value="dark">Dark</DropdownMenu.RadioItem>
	<DropdownMenu.RadioItem value="system">System</DropdownMenu.RadioItem>
</DropdownMenu.RadioGroup>
```

### Submenu

```svelte
<DropdownMenu.Sub>
	<DropdownMenu.SubTrigger>Share</DropdownMenu.SubTrigger>
	<DropdownMenu.SubContent>
		<DropdownMenu.Item>Email</DropdownMenu.Item>
		<DropdownMenu.Item>Slack</DropdownMenu.Item>
	</DropdownMenu.SubContent>
</DropdownMenu.Sub>
```