---
title: "Select field"
description: "Lets people choose one value from a closed list as one complete field of a form — a label that can say the field is required or optional, a trigger that shows the chosen option and opens a list of options, and a line of help or an error below — tied together for assistive technology and taking part in a form as one control."
url: "https://tanrei.chnotchy.com/components/select-field/"
last_updated: 2026-10-23T21:17:12.000Z
---

# Select field

> Lets people choose one value from a closed list as one complete field of a form — a label that can say the field is required or optional, a trigger that shows the chosen option and opens a list of options, and a line of help or an error below — tied together for assistive technology and taking part in a form as one control.

## Overview

Use a select field in a form for one value out of a list that is known and closed: a country, a time zone, a plan. It is the ordinary case, ready to use: a label, the box that shows the chosen option and opens the list, a line of help, and the words for a value that was refused.

**Built from** a [field](https://tanrei.chnotchy.com/components/field/) and a [select](https://tanrei.chnotchy.com/components/select/). The field is the frame: the label, the required or optional mark, the help and the error. The select is the control: the trigger, the list and everything a person does in them. The select field draws nothing of its own and has no token: every property it has is a property of one of the two, given to it unchanged, and the options you give it are its select’s.

It is as wide as the place it is put in, and its box fills it. Give it a narrower place for a narrower box.

On the web it is `<tanrei-select-field>` with `<tanrei-option>` children. The other platforms have not implemented it yet.

### Usage

The options are children of the select field: each has a value and a label. `value` names the chosen one. `change` and `toggle` are the select’s own events, and when either is heard the field’s `value` and `open` are already the new ones.

**Web**

```html
<form>
  <tanrei-select-field name="country" label="Country" value="jp" required required-text="Required"
    supporting-text="Where your invoices are addressed.">
    <tanrei-option value="ca">Canada</tanrei-option>
    <tanrei-option value="jp">Japan</tanrei-option>
  </tanrei-select-field>
</form>

<!-- Grouped, with a line under a label and a glyph that stands for the field. -->
<tanrei-select-field label="Time zone" value="Europe/Lisbon">
  <span slot="leading-icon">public</span>
  <tanrei-option-group label="Asia">
    <tanrei-option value="Asia/Tokyo" supporting-text="UTC+9">Tokyo</tanrei-option>
  </tanrei-option-group>
  <tanrei-option-group label="Europe">
    <tanrei-option value="Europe/Lisbon" supporting-text="UTC+0">Lisbon</tanrei-option>
  </tanrei-option-group>
</tanrei-select-field>

<script type="module">
  import '@tanrei/web/components/select-field';

  const country = document.querySelector('[name="country"]');
  // The person chose another option. The value is already the new one.
  country.addEventListener('change', () => save(country.value));
  // Opened or closed by the person; a close says why.
  country.addEventListener('toggle', (e) => console.log(e.detail.open, e.detail.reason));
  // Validation is yours: the select field never sets error itself.
  country.error = submitted && !ships(country.value);
  country.errorText = 'We cannot ship there yet. Choose another country.';
</script>
```

**React**

```tsx
import { Option, SelectField } from '@tanrei/react';

<SelectField label="Country" value={country} required requiredText="Required" onChange={(event) => setCountry(event.currentTarget.value)}>
  <Option value="ca">Canada</Option>
  <Option value="jp">Japan</Option>
</SelectField>
```

### One level down

The same field, written by hand from its two members, is the same picture and the same control to assistive technology:

```html
<tanrei-field label="Country" required required-text="Required"
  supporting-text="Where your invoices are addressed.">
  <tanrei-select name="country" placeholder="Choose a country">
    <tanrei-option value="jp">Japan</tanrei-option>
    <tanrei-option value="ke">Kenya</tanrei-option>
  </tanrei-select>
</tanrei-field>
```

Go one level down when you need an arrangement the select field does not offer:

| You need | Use |
| --- | --- |
| A label, the box, help and an error | The select field |
| Something of your own inside the frame, beside or below the box | A [field](https://tanrei.chnotchy.com/components/field/) with a [select](https://tanrei.chnotchy.com/components/select/) and your own element in it |
| The box alone, where its label stands elsewhere: a theme in a bar, a sort order in a toolbar, a cell of a table | The [select](https://tanrei.chnotchy.com/components/select/) alone, named by its own `label` |
| A list long enough that people would rather type than scroll | A [combobox](https://tanrei.chnotchy.com/components/combobox/) |

What changes one level down is where things are said. `name`, `value` and the options are on the select, which is then the control the form meets, and its events are heard on it. `label`, `error` and `disabled` stay on the field, which passes them to the control: do not set the select’s own.

## Specs

### What each member gives

| Aspect | From the field | From the select |
| --- | --- | --- |
| Properties | `label`, `labelHidden`, `supportingText`, `errorText`, `error`, `disabled`, `required`, `optional`, `requiredMark`, `requiredText`, `optionalText` | `variant`, `size`, `value`, `placeholder`, `readOnly`, `open`, `separation`, `iconSpace`, `status`, `statusText`, `emptyText` |
| Events | — | `change`, `toggle` |
| Slots | `label-icon` | `leading-icon`, and the options |
| Tokens | `comp.field.*` | `comp.input-box.*` for the box, which every input box reads; `comp.select.*` for the list |

The select has a `label`, a `labelHidden`, an `error` and a `disabled` of its own. They are not properties of the select field: the field’s `label` names the control, its `error` puts the box in its error condition and its `disabled` disables it. So you set each of them once, on the select field, and its label changes with the control.

In the `stacked` look the label is the field’s row above the box. In the `filled` and the `outlined` look the select draws the same label itself, floating in its box, and the field draws no label row; a required field is then marked by an asterisk after the label, whichever mark the design system names. The help starts where the value starts, past a leading icon. While the list is open the label and the help are drawn focused, as the box is.

What the trigger and the list do — opening, the arrow keys, typing, choosing, the groups — is on the [select’s page](https://tanrei.chnotchy.com/components/select/). What the frame does — the required mark, the help, the error and how it is announced — is on the [field’s page](https://tanrei.chnotchy.com/components/field/).

### Setting one field apart

The select field has no token of its own. Its frame reads the field’s tokens and its box and its list the select’s, wherever they are set. To change one instance, set the member’s token on it:

```html
<tanrei-select-field label="Country"
  style="--tanrei-comp-field-label-gap: 12px"></tanrei-select-field>
```

- Category: Selection
- Level: composed
- Listing: default
- Built from: Field, Select
- Page: https://tanrei.chnotchy.com/components/select-field/
- Spec: https://github.com/chnotchy/tanrei/blob/main/specs/select-field.spec.json

### Availability

| Design system | Has it | Notes |
| --- | --- | --- |
| Tanrei (`tanrei`) | Yes | Variants left out: `filled`, `outlined`. |
| Cupertino (Apple HIG-inspired) (`cupertino`) | Yes | — |
| M3 Expressive-like (Material 3 Expressive-inspired) (`m3-expressive-like`) | Yes | — |
| M3-like (Material 3-inspired) (`m3-like`) | Yes | — |

### Platforms

- Web: the element `<tanrei-select-field>`, registered by importing `@tanrei/web` (or only its own module, `@tanrei/web/components/select-field`).
- React: `SelectField` from `@tanrei/react`.

| Platform | Name | Status |
| --- | --- | --- |
| Web | `tanrei-select-field` | lagging |
| SwiftUI | `TanreiSelectField` | planned |
| Jetpack Compose | `TanreiSelectField` | planned |
| Flutter | `TanreiSelectField` | planned |
| React Native | `SelectField` | planned |

Names a platform gives in its own idiom:

| Spec | Web | SwiftUI | Jetpack Compose | Flutter | React Native |
| --- | --- | --- | --- | --- | --- |
| `value` (prop) | `value` | `selection` | `value` | `value` | `value` |
| `label` (prop) | `label` | `label` | `label` | `labelText` | `label` |
| `labelHidden` (prop) | `labelHidden` | `labelsHidden` | `labelHidden` | `labelHidden` | `labelHidden` |
| `placeholder` (prop) | `placeholder` | `prompt` | `placeholder` | `hintText` | `placeholder` |
| `supportingText` (prop) | `supportingText` | `supportingText` | `supportingText` | `helperText` | `supportingText` |
| `error` (prop) | `error` | `error` | `isError` | `isError` | `error` |
| `disabled` (prop) | `disabled` | `disabled` | `enabled` | `enabled` | `disabled` |
| `required` (prop) | `required` | `isRequired` | `required` | `required` | `required` |
| `optional` (prop) | `optional` | `isOptional` | `optional` | `optional` | `optional` |
| `open` (prop) | `open` | `isPresented` | `expanded` | `controller` | `open` |
| `change` (event) | `change` | `selection` | `onValueChange` | `onChanged` | `onValueChange` |
| `toggle` (event) | `toggle` | `isPresented` | `onExpandedChange` | `onOpenChanged` | `onOpenChange` |

Statuses: `planned` — In the inventory. Nothing shippable exists yet. `lagging` — An implementation of an earlier spec exists; it has not caught up with the current one. `alpha` — Implemented with tests. The API may still change. `beta` — Feature complete and at parity. Only fixes are expected. `stable` — Covered by semantic versioning. `deprecated` — Still shipped; scheduled for removal.

### Anatomy

- `field`: The Field: the label row with its glyph and its requirement mark, and the supporting row with the help and the error text. In a look whose select floats the label it draws no label row.
- `select`: The select, as the Field's one control: the trigger with the value it shows, its leading icon and its chevron, the label that floats in it in the looks that float one, and the list of options that opens from it.

### Props

| Prop | Type | Default | Web attribute | Description |
| --- | --- | --- | --- | --- |
| `variant` | `enum`: `stacked`, `filled`, `outlined` | `"stacked"` | `variant` | The text input's three looks, so that a select is drawn as the text inputs beside it. Stacked is a filled box that shows focus and error with a line inside its edge and draws no label: the label of the Field that frames it stands above it. Filled and outlined float the label inside the box. Use one style per form. A design system may leave some out (the Tanrei system ships stacked only) or add values. (From Select.) |
| `size` | `enum`: `small`, `medium`, `large` | `"medium"` | `size` | Minimum height of the container: stacked 32 / 40 / 56, as tall as a Button of the same size, so that the box and a Button side by side in one row stand as tall as each other; filled and outlined 40 / 48 / 56, which hold the label that floats inside them. The text input's three sizes: medium and large for forms, small for a select in an app bar, a toolbar or a dense row of controls, where nothing frames it. The hit area always meets the minimum target. A design system may add values. (From Select.) |
| `value` | `string` | `""` | `value` | The value of the chosen option. The select shows that option's label; while value names no option it shows the placeholder. An option whose value is the empty string is a choice like any other ("None", "Any") and is the chosen one while value is empty. (From Select.) |
| `label` | `string` | `""` | `label` | Names the control, visibly and to assistive technology. Required, unless the control names itself (a checkbox or a switch with its own label): then leave it empty and the field adds only help and an error. (From Field: Names the select. In a filled or outlined look the select draws it, floating in its box, and the Field draws no label row (FLD-25, SEL-15).) |
| `labelHidden` | `boolean` | `false` | `label-hidden` | Does not draw the label, which stays the accessible name. For a control whose visible label is elsewhere (a table column, a toolbar). (From Field: Hides the label wherever it would be drawn: the Field's row, or the select's floating label (FLD-25).) |
| `placeholder` | `string` | `""` | `placeholder` | A hint shown while nothing is chosen and the label is not in the line ("Choose a country"). Never a replacement for label, and never a choice. (From Select.) |
| `supportingText` | `string` | `""` | `supporting-text` | Help shown below the control and given to assistive technology as the control's description. While the field is in error it gives way to errorText, unless the design system keeps both (comp.field.error-text.placement append). (From Field.) |
| `errorText` | `string` | `""` | `error-text` | Shown while error is true, in supportingText's place — or below it, which then stays, where the design system's comp.field.error-text.placement is append: what is wrong and how to put it right, in words. (From Field.) |
| `error` | `boolean` | `false` | `error` | Puts the field in the error condition: the error text is drawn, the control is exposed as invalid and, where it has an error condition of its own, drawn in it. What a value means is the product's to validate; the field never sets this itself. (From Field: The Field puts its select in the select's own error condition (FLD-8, SEL-9).) |
| `disabled` | `boolean` | `false` | `disabled` | Disables the control and draws the frame as disabled. Disable a framed control here, not on the control, so that its label follows. (From Field: The Field disables its select (FLD-14, SEL-46); the select field is then left out of its form (SEF-2).) |
| `readOnly` | `boolean` | `false` | `readonly` | The value is shown, can be focused and is submitted, but cannot be changed: the list does not open and no chevron is drawn. (From Select.) |
| `required` | `boolean` | `false` | `required` | What the form asks of the control: true exposes it as required and draws the required mark beside the label. It never validates: a missing answer is the product's to report with error. (From Field: The Field exposes its select as required (FLD-10, SEL-11).) |
| `optional` | `boolean` | `false` | `optional` | Draws the optional tag after the label and adds optionalText to the control's description, because assistive technology has no state for it. Ignored while required is true: a control is never both. (From Field.) |
| `requiredMark` | `enum`: `auto`, `tag`, `asterisk`, `none` | `"auto"` | `required-mark` | How this control shows that it is required: tag is a small filled Tag with requiredText, asterisk is "*" after the label, none draws nothing and keeps the semantics. Auto takes comp.field.requirement.mark, which follows sys.behavior.requirement-mark, the system's one answer. Ignored unless required is true. (From Field.) |
| `requiredText` | `string` | `""` | `required-text` | The text of the required tag, in the product's language ("Required", "必須"). The product's: Tanrei has no word for it. Empty reads the product's words; with neither, FLD-24 says what is drawn. (From Field.) |
| `optionalText` | `string` | `""` | `optional-text` | The text of the optional tag, in the product's language ("Optional", "任意"); also read to assistive technology as part of the description. The product's: Tanrei has no word for it. Empty reads the product's words. (From Field.) |
| `open` | `boolean` | `false` | `open` | Whether the list is shown. The select opens and closes itself and emits toggle; the product may also set it. Ignored while the select is disabled or read-only or has nothing to show: no option, no status row and no empty text (SEL-61). (From Select.) |
| `separation` | `enum`: `auto`, `divider`, `gap` | `"auto"` | `separation` | How a group of options is told from what is next to it. divider: a line between them. gap: empty space and no line. Auto takes comp.select.separation, which follows the design system's choice. (From Select.) |
| `iconSpace` | `enum`: `auto`, `always`, `never` | `"auto"` | `icon-space` | Whether an option keeps the room of the leading icon column where it has no icon, so that the labels of a section start on one line — a section being an option group, or a run of adjacent options outside any group. auto: an option keeps the column while another option of its section has a leading icon, so that a section without icons starts its labels where the row's content starts. always: every option keeps it. never: only an option that has an icon has the column. The menu's iconSpace, with the same values and default (SEL-66). (From Select.) |
| `density` | `enum`: `regular`, `compact` | `"regular"` | `density` | How much room an option of the list takes: its least height, its paddings, the gap between its columns and the size of its glyphs (the leading icon, the check), and never its text style. regular (a 48 row in the default system) is for a product used by touch as well as by pointer; compact (a 32 row with 20 glyphs, the menu's compact row) is for a tool used with a pointer, whose lists are long. For touch an option is never lower than the touch target in either (SEL-37). The field's own box is not changed: its height is size's. A design system may add values. (From Select.) |
| `status` | `enum`: `idle`, `loading`, `error` | `"idle"` | `status` | What the product's source of options is doing, which the product sets: idle (the options given are final), loading (options are on their way: the status row shows a loading indicator and the list is marked busy) or error (the source failed: the status row shows statusText in the error color, announced at once). The combobox's and the search's values, with the same meaning. The select never loads anything itself. (From Select.) |
| `statusText` | `string` | `""` | `status-text` | The status row's text, in the product's language, read to assistive technology when the list opens and when it changes: a count ("20 of 340 projects shown"), that loading failed ("Projects could not be loaded"), or, while status is loading, the loading indicator's name ("Loading projects"). Empty draws no status row unless status is loading. (From Select.) |
| `emptyText` | `string` | `""` | `empty-text` | Shown in the list while the select holds no option, status is idle and statusText is empty, in the product's language ("No projects yet"), so that the select still opens and says why there is nothing to choose. The product's: Tanrei has no words for it. Empty reads the product's words (noOptionsText); with neither, the select has nothing to show and does not open (SEL-61), and it is reported. (From Select.) |

### Events

| Event | Description |
| --- | --- |
| `change` | The person chose an option whose value differs from the select's; carries the new value. Not emitted when the product sets value, when the chosen option is chosen again, or while the person only moves through the list. (From Select.) |
| `toggle` | The list was opened or closed by the person; carries the new open and, for a close, the reason: select, escape, back, outside, focus-out, anchor-hidden, press or tab (in the platform's casing). After a choice it follows change. (From Select.) |

### Slots

| Slot | Description |
| --- | --- |
| `leading-icon` | A glyph at the start of the container that stands for the field whatever is chosen (a globe before a language). It takes the place of the chosen option's own glyph. (From Select.) |
| `label-icon` | A glyph before the label. (From Field.) |

### Item: `option`

One choice of the select: a label, the value it stands for, and optionally a supporting line and a glyph.

Names: Web `tanrei-option`, SwiftUI `TanreiSelectOption`, Jetpack Compose `TanreiSelectOption`, Flutter `TanreiSelectOption`, React Native `SelectOption`.

| Prop | Type | Default | Web attribute | Description |
| --- | --- | --- | --- | --- |
| `label` | `string` | `""` | `label` | The option's text and its accessible name; the container shows it once the option is chosen. Required. |
| `value` | `string` | `""` | `value` | Identifies the choice: the option is the chosen one while the select's value equals it. Unique within the select. The empty string is a value like any other, for an option that stands for no choice ("None"). |
| `supportingText` | `string` | `""` | `supporting-text` | A line below the label that says more about the choice. Shown in the list, not in the container. |
| `leadingIcon` | `string` | `""` | `leading-icon` | The name of an icon (a glyph of the system's icon set) before the label; the container shows it too while the option is chosen and the select has no leading icon of its own. |
| `disabled` | `boolean` | `false` | `disabled` | Prevents the option from being chosen. It stays reachable with the arrow keys. |

### Item: `option-group`

A run of related options, optionally titled. The select separates a group from what is next to it by a divider or a gap.

Names: Web `tanrei-option-group`, SwiftUI `TanreiSelectSection`, Jetpack Compose `TanreiSelectGroup`, Flutter `TanreiSelectGroup`, React Native `SelectOptionGroup`.

| Prop | Type | Default | Web attribute | Description |
| --- | --- | --- | --- | --- |
| `title` | `string` | `""` | — | A short heading drawn above the group's options, which also names the group; empty draws none and leaves the group unnamed. |

### States

`enabled`, `disabled`, `hovered`, `focused`, `pressed`, `selected`, `error`

### Accessibility

- Role: `combobox`
- Labeling: The select field adds nothing to what its members expose and coordinates nothing: the Field gives the select its name, its description and its required, invalid and disabled states (FLD-8, FLD-10, FLD-11, FLD-14), and the select carries them on its own trigger and names its list by the same name (SEL-11, SEL-48). Assistive technology meets one control that opens a list of choices, named by label, with the chosen option's label as its value — exactly as it meets a Field around a select written by hand.
- Minimum target size: yes

| Keys | Action |
| --- | --- |
| Every key | The select's (its accessibility block; SEL-23, SEL-27, SEL-28, SEL-31, SEL-33, SEL-34). The select field handles no key and adds no focus stop (SEF-3). |

- One level down is the same thing: a Field with a select in it, holding the same options. Every fixture has that pair as its twin, and the accessibility tree of the two is the same (SEF-1).
- On the web the two members stand in the select field's own shadow root, so the form meets the select field and not the select (SEF-2), focus passes through to the trigger (SEF-3), and the options, which stay the product's children, reach the select through a slot and are read by it as data.
- A select with no visible label of its own — in a header, a toolbar, a column of a table — is the bare select, named by its own label, not a select field with labelHidden.

### Behaviour

Requirements in EARS form, each with its stable id.

- **SEF-1** THE select field SHALL be a Field that frames one select, and nothing else. It SHALL give label, labelHidden, supportingText, errorText, error, disabled, required, optional, requiredMark, requiredText and optionalText to its Field and every other prop to its select, each unchanged; SHALL hold the label-icon slot for its Field and the leading-icon slot for its select; SHALL give its select every option and option group the product gives it, in the order given, as that select's own items, read, drawn and chosen by the select (SEL-17, SEL-31 to SEL-45); and SHALL emit its select's events as its own, each once. It SHALL draw no part of its own, hold no state of its own and have no token of its own: what it shows, how it behaves and what it exposes to assistive technology SHALL be exactly what that Field and that select do when a product places the one in the other (FLD-1 to FLD-28; SEL-1 to SEL-64) — the label row and its requirement mark (FLD-2 to FLD-6), or the label that floats in the box with the Field's row left out (FLD-25, SEL-15, SEL-7); the supporting row and the error, started where the value starts (FLD-7 to FLD-9, FLD-26); the rows drawn focused while the list is open (FLD-13, SEL-20); the name, the description and the states (FLD-10, FLD-11, FLD-14, SEL-11); and the width, which is the Field's and which the select fills (FLD-1, SEL-49).
- **SEF-2** WHERE the platform has forms (the web) THE select field SHALL be the one control the form sees: it SHALL take name, submit its select's value, reset to the value it was first given, restore it on navigation, report to the form's constraint validation exactly what its select would report there (SEL-11), be submitted WHILE readOnly is true (SEL-47), and be left out WHILE disabled is true or a disabled group of the form holds it (SEL-46); its select and its Field SHALL take no part in the form themselves.
- **SEF-3** WHEN the select field is given focus — by the product, by a press on its label row (FLD-12), or by a form that reports its validity — THE select field SHALL pass the focus to its select's container and SHALL add no stop to the focus order: the one stop inside it is its select's (SEL-13). WHILE focus is anywhere inside it, or its select's list is open, THE select field SHALL count as focused for its Field (FLD-13).
- **SEF-4** IF the select field is placed in a Field THE select field SHALL in debug builds report that it is a field already and that the bare control is the select, and both SHALL still render (FLD-15). WHILE it stands in a field group THE select field SHALL follow that group's disabled, through its own Field, and take nothing else from the group (FGR-20).
- **SEF-5** THE select field SHALL have no words of its own and SHALL read none: requiredText and optionalText are read by its Field (FLD-24), emptyText by its select (SEL-62), each from the instance's prop and then from the product's words.
- **SEF-6** WHERE the platform has ARIA attributes (the web), WHEN the product sets an aria- attribute on the host, by the attribute or by the ARIA property that reflects it, THE select field SHALL move it to the data-aria- attribute of the same name, so that the host is no second node with its name, description or state, and SHALL expose it on the element that carries its role — an id reference by the elements it names in the host's tree or a tree around it, an error message as part of the description while the select field is invalid — except those the select field owns (aria-label, aria-labelledby, aria-disabled, aria-haspopup, aria-expanded, aria-controls), which it SHALL move and not expose: its name is label (SEF-1). WHEN the product removes the aria- attribute or its data-aria- twin, or sets the ARIA property that reflects it (ariaLabel, ariaDescribedByElements…) to null, THE select field SHALL take it off that element. WHEN the product sets an aria- attribute the select field owns THE select field SHALL report it in debug builds.

### Tokens

As written in the token documents (DTCG): an alias in braces names the token it takes its value from, which each design system resolves. On the web each token is a CSS custom property: `--tanrei` and the name after `tanrei`, joined by hyphens (`tanrei.comp.field.…` → `--tanrei-comp-field-…`).

#### `tanrei.comp.field`

| Token | Type | Value |
| --- | --- | --- |
| `comp.field.label.typescale` | `typography` | `{tanrei.sys.typescale.label}` |
| `comp.field.label.gap` | `dimension` | `{tanrei.sys.space.space100}` |
| `comp.field.label-icon.size` | `dimension` | `{tanrei.sys.icon.small}` |
| `comp.field.label-icon.gap` | `dimension` | `{tanrei.sys.space.space100}` |
| `comp.field.requirement.mark` | `number` | `{tanrei.sys.behavior.requirement-mark}` |
| `comp.field.requirement.gap` | `dimension` | `{tanrei.sys.space.space100}` |
| `comp.field.requirement.asterisk-gap` | `dimension` | `{tanrei.sys.space.space25}` |
| `comp.field.supporting-text.typescale` | `typography` | `{tanrei.sys.typescale.label-small}` |
| `comp.field.supporting-text.gap` | `dimension` | `{tanrei.sys.space.space50}` |
| `comp.field.counter.gap` | `dimension` | `{tanrei.sys.space.space200}` |
| `comp.field.motion.state-duration` | `duration` | `{tanrei.sys.motion.role.state.default}` |
| `comp.field.motion.state-easing` | `cubicBezier` | `{tanrei.sys.motion.easing.state}` |
| `comp.field.standard.label.color` | `color` | `{tanrei.sys.color.on-surface}` |
| `comp.field.standard.label-icon.color` | `color` | `{tanrei.sys.color.on-surface-variant}` |
| `comp.field.standard.supporting-text.color` | `color` | `{tanrei.sys.color.on-surface-variant}` |
| `comp.field.standard.counter.color` | `color` | `{tanrei.sys.color.on-surface-variant}` |
| `comp.field.standard.required-asterisk.color` | `color` | `{tanrei.sys.color.primary}` |
| `comp.field.standard.error.label.color` | `color` | `{tanrei.sys.color.on-surface}` |
| `comp.field.standard.error.label-icon.color` | `color` | `{tanrei.sys.color.on-surface-variant}` |
| `comp.field.standard.error.supporting-text.color` | `color` | `{tanrei.sys.color.on-surface-variant}` |
| `comp.field.standard.error.counter.color` | `color` | `{tanrei.sys.color.on-surface-variant}` |
| `comp.field.standard.error.required-asterisk.color` | `color` | `{tanrei.sys.color.primary}` |
| `comp.field.standard.error.value-text.color` | `color` | `{tanrei.sys.color.on-surface-variant}` |
| `comp.field.standard.value-text.color` | `color` | `{tanrei.sys.color.on-surface-variant}` |
| `comp.field.standard.error-text.color` | `color` | `{tanrei.sys.color.error}` |
| `comp.field.value-text.typescale` | `typography` | `{tanrei.sys.typescale.label}` |
| `comp.field.value-text.gap` | `dimension` | `{tanrei.sys.space.space200}` |
| `comp.field.error-text.gap` | `dimension` | `{tanrei.sys.space.space50}` |
| `comp.field.error-text.placement` | `number` | `0` |

Per-state tokens, valued by the design system's pattern rules (not written by hand):

- `comp.field.<variant>.<state>.<property>` for the variants `standard`, the states `focused`, `disabled` and the properties `label.color`, `label-icon.color`, `supporting-text.color`, `required-asterisk.color`, `error.label.color`, `error.label-icon.color`, `error.supporting-text.color`, `error.required-asterisk.color`, `counter.color`, `error.counter.color`, `value-text.color`, `error.value-text.color`, `error-text.color`.

### What the web draws differently

- The element’s shadow root holds a `<tanrei-field>` with a `<tanrei-select>` in it, and nothing else. Importing the element defines both.
- The options stay your children of `<tanrei-select-field>`. They are never moved or copied: they reach the select inside through a slot, and the select reads them again when they change. Replacing them by hand (`replaceChildren()`) works as on a select.
- The element is form-associated. It takes `name` and `form`, submits the value alone — nothing while disabled, and still while read-only —, resets to the `value` attribute, follows a disabled `<fieldset>`, and reports a missing value while `required` is set and the value is empty. Its two members add no entry to the form.
- `change` is the select’s composed, bubbling event. `toggle` is the select’s CustomEvent with `detail.open` and `detail.reason`: composed, and not bubbling, so it is heard on the element and never by an ancestor such as a `<details>`. Their target is the element, and `event.target.value` and `event.target.open` are new in every listener.
- Parts: `field` and `select` are the two members. Their own parts have the same names here as one level down: `label-icon`, `supporting-text`; `container`, `outline`, `active-indicator`, `value`, `placeholder`, `leading-icon`, `chevron`, `list`, `option`, `option-label`, `option-supporting-text`, `option-leading-icon`, `mark`, `group`, `group-title`, `divider`, `status`. `label` and `requirement-label` are the drawn one of the two — the field’s row, or the select’s floating label — and `field-label`, `select-label`, `field-requirement-label` and `select-requirement-label` name one member’s alone.
- The element is not focusable itself: `focus()` goes to the trigger, and a page’s own `<label for>` moves focus there. A press on the label row focuses the trigger and opens nothing; a press on the trigger opens the list; a press on the help does nothing.
- The element has no role. Name it with `label` — with `label-hidden` where the label is drawn elsewhere — and never with `aria-label`, which names nothing here.
- The attributes are the members’ own: `label-hidden`, `supporting-text`, `error-text`, `required-mark`, `required-text`, `optional-text`, `readonly`.
- A child that is neither an option, a group of options nor a glyph for `label-icon` or `leading-icon` is not drawn; a debug build says so.
- Before the element is defined, its options are running text. Hide `tanrei-select-field:not(:defined) > *` and reserve the height. A page that must work without script uses a native `<select>` with its own `<label>`.

## Guidelines

### Do

- Write a label that names what is chosen, and keep it visible in a form.
- Order options the way people look for them: alphabetically, by number, or the common ones first.
- Group a long list and give each group a short title.
- Preselect a value only where most people would choose it.
- Give the field a width by its place: a column of a form. The box fills it.

### Don’t

- Don’t use a select field with `labelHidden` in a bar or a toolbar. That is the bare [select](https://tanrei.chnotchy.com/components/select/), named by its own `label`.
- Don’t use the placeholder as the label. It goes away once something is chosen.
- Don’t navigate, submit or delete on `change` without saying so. People move through a list to read it.
- Don’t put a select field inside a field. It is a field already; a debug build says so. The control a field frames is the select.
- Don’t name it with `aria-label`. Where no label should be drawn, give `label` and `labelHidden`.

## Accessibility

### What the component handles

- It is one combobox that is not editable, the select’s. Its name is `label`, drawn or not; its description is the shown supporting or error text, with the optional text while the field is optional.
- It is exposed as invalid while `error` is true, as required while `required` is set, as disabled while `disabled` is true, as read-only while `readOnly` is true, and as expanded while its list is open.
- The name, the description and the states are tied exactly as a field ties them to any control it frames. The field written by hand, one level down, is the same control.
- The drawn label, the requirement mark and the glyphs are not exposed a second time.
- It is one stop for the Tab key. A press on the label moves focus to the trigger and opens nothing; a press on the help does nothing.
- An error that appears while focus is in the select field is announced once, politely, by its field member.
- Everything in the list — the active option, the options’ names, descriptions and states, the groups — is the select’s, as on the [select’s page](https://tanrei.chnotchy.com/components/select/#accessibility).
- Direction, enlarged text and forced colors are each member’s own answer.
- It has no words of its own. `requiredText` and `optionalText` left empty are read from the product’s words by the field.

Known gaps on the web are its members’: the divider between two groups is not exposed as a separator, typing compares labels the way JavaScript does, and before the element is defined nothing is drawn but the options as text.

### What you need to do

- Give every select field a `label`, and every option a label.
- Validate the value yourself, set `error`, and write `errorText` so that it says how to put the answer right.
- Give the words of the requirement: `required-text` and `optional-text` on the select field, or once for the whole product with `setWords({ requiredText, optionalText })`. Tanrei ships none: without `requiredText` an asterisk stands in the tag’s place, and without `optionalText` no tag is drawn and nothing is said. See [The product’s words](https://tanrei.chnotchy.com/foundations/words/).
- Keep option values unique within a select field.