---
title: "Side sheet"
description: "Holds supplementary content or a secondary task in a panel at the end edge, with a headline, a close button and optional actions, beside the content on a wide window or over it on a compact one."
url: "https://tanrei.chnotchy.com/components/side-sheet/"
last_updated: 2026-10-23T21:17:12.000Z
---

# Side sheet

> Holds supplementary content or a secondary task in a panel at the end edge, with a headline, a close button and optional actions, beside the content on a wide window or over it on a compact one.

## Overview

> [!NOTE]
> **A revised spec, not yet on every platform**
>
> This page describes the side sheet’s actions and close button as the spec has them now, the same as the dialog’s. The actions are a full-width row of tonal Buttons placed by their task: each is marked `confirming` or `dismissive`, and a modal sheet must offer at least one. The close button is a small tonal Button, drawn unless `closable` is false. A divider stands below the header as one stands above the actions, and the actions stay above the on-screen keyboard. The web component already does all of this, and so do the demos; it stays marked lagging above until the revision has been reviewed. SwiftUI, Compose, Flutter and React Native are lagging too: until they catch up they ship the previous revision, with a standard icon button to close, the actions in a row from the start edge in the order given, optional in both forms and 8 apart.

### Usage

A side sheet is controlled, and it never closes itself. You show it by setting `open`. When the person asks it to go, the sheet emits `close` with the reason, and you set `open` back to false. On SwiftUI, where `open` is a binding, the sheet writes false to it and then calls `onClose`. If you leave `open` true after a drag, the sheet slides back.

`close` carries one of five reasons, in the platform’s casing:

| Reason | What the person did | Which form |
| --- | --- | --- |
| `close` | Activated the close button | Standard and modal |
| `scrim` | Pressed the dim area beside a modal sheet | Modal |
| `escape` | Pressed Escape | Modal |
| `back` | Used the platform’s back: Android’s back button or gesture, the iOS accessibility escape gesture | Modal |
| `drag` | Dragged the sheet toward its edge past half its width, or flung it that way | Modal |

A standard sheet ignores Escape, back and drags. Its close button is the person’s only way to close it, unless your own control does.

The sheet has two forms on `variant`, and one product usually uses both: standard where the window is wide enough, modal where it is not.

- **Standard**, the default, is a layout region, not an overlay. While open it takes its width at the end of the row you place it in, and the content beside it resizes. It draws no scrim and never keeps focus.
- **Modal** is a modal overlay. It slides over the content from the end edge with a scrim, keeps focus inside, and returns it when it closes.

The sheet draws a header with the `headline` and, while `closable` is true (the default), a close button named by `closeLabel`. Your content goes below the header, and Tanrei Buttons in the actions slot go along the bottom, each marked `confirming` (it completes the task: Apply, Save) or `dismissive` (it backs out: Cancel). The sheet places them by those marks, so you give them in any order, and it draws an action whose `variant` you did not set as tonal. A modal sheet must offer at least one action; a standard sheet may have none. An action never closes the sheet by itself: close it from the action’s handler.

Mark the element that should get focus when the sheet opens with the platform’s own mark: `autofocus` on the web, `.defaultFocus` or an `@AccessibilityFocusState` on SwiftUI, a `FocusRequester` passed as `initialFocus` on Compose, `autofocus: true` on Flutter, and `initialFocusRef` on React Native. On SwiftUI, `.defaultFocus` moves keyboard focus, and an `@AccessibilityFocusState` binding passed as `initialFocus` moves VoiceOver. Without a mark, focus goes to the sheet itself, so its headline is read first.

The Web and React samples show the current spec. SwiftUI, Compose, Flutter and React Native are lagging: they still ship the previous revision of the side sheet, which has no `confirming` or `dismissive` marks and no tonal default, so their samples give each action the text variant and put the main action first, and show that revision until they catch up.

**Web**

```html
<tanrei-button id="filters" variant="outlined">Filters</tanrei-button>

<!-- Standard: the last item of a flex row. It is an <aside> named by the headline. -->
<div style="display: flex">
  <main style="flex: 1">…</main>
  <tanrei-side-sheet headline="Filters" close-label="Close filters">
    <p>Show results from the last 30 days with every selected label.</p>
    <!-- confirming goes at the end of the row. Without a variant, both are tonal. -->
    <tanrei-button slot="actions">Reset</tanrei-button>
    <tanrei-button slot="actions" confirming>Apply</tanrei-button>
  </tanrei-side-sheet>
</div>

<script type="module">
  import '@tanrei/web/components/side-sheet';
  const sheet = document.querySelector('tanrei-side-sheet');
  document.querySelector('#filters').addEventListener('click', () => (sheet.open = true));
  // The sheet never closes itself. detail.reason is close, scrim, escape, back or drag.
  sheet.addEventListener('close', (e) => (sheet.open = false));
  // On a window narrower than 840px, the same sheet as a modal <dialog> over a scrim.
  matchMedia('(width < 840px)').addEventListener('change', (e) => (sheet.variant = e.matches ? 'modal' : 'standard'));
</script>
```

**React**

```tsx
import { Button, SideSheet } from '@tanrei/react';

<SideSheet
  variant={wide ? 'standard' : 'modal'}
  open={open}
  headline="Filters"
  closeLabel="Close filters"
  onClose={() => setOpen(false)}
>
  <p>Show results from the last 30 days with every selected label.</p>
  <Button slot="actions" onClick={reset}>Reset</Button>
  <Button slot="actions" confirming onClick={apply}>Apply</Button>
</SideSheet>
```

**SwiftUI**

```swift
import Tanrei

// Standard: a view at the end of an HStack. Closing writes false to the binding, then calls onClose.
HStack(spacing: 0) {
    ResultsView()
    TanreiSideSheet("Filters", isPresented: $filtersShown, closable: true, closeLabel: "Close filters") {
        FilterForm()
    } actions: {
        TanreiButton("Apply", variant: .text) { apply() }
        TanreiButton("Reset", variant: .text) { reset() }
    }
}

// Modal: a modifier on the view it covers, presented as tanreiDialog is.
ResultsView()
    .tanreiSideSheet("Filters", isPresented: $filtersShown, closable: true, closeLabel: "Close filters") { … }
```

**Compose**

```kotlin
import io.github.chnotchy.tanrei.components.TanreiButton
import io.github.chnotchy.tanrei.components.TanreiSideSheet
import io.github.chnotchy.tanrei.tokens.TanreiButtonVariant
import io.github.chnotchy.tanrei.tokens.TanreiSideSheetVariant

// Standard: the last child of a Row. Modal: drawn in a Dialog window of its own.
// Set visible to false from onClose, which receives the reason.
Row {
    ResultsScreen(Modifier.weight(1f))
    TanreiSideSheet(
        visible = filtersShown,
        onClose = { filtersShown = false },
        headline = "Filters",
        variant = if (wide) TanreiSideSheetVariant.Standard else TanreiSideSheetVariant.Modal,
        closable = true,
        closeLabel = "Close filters",
        actions = {
            TanreiButton(text = "Apply", onClick = apply, variant = TanreiButtonVariant.Text)
            TanreiButton(text = "Reset", onClick = reset, variant = TanreiButtonVariant.Text)
        },
    ) {
        FilterForm()
    }
}
```

**Flutter**

```dart
import 'package:tanrei/tanrei.dart';

// Standard: at the end of a Row. A modal sheet goes in a Stack over the page instead.
Row(
  children: <Widget>[
    const Expanded(child: ResultsPage()),
    TanreiSideSheet(
      open: filtersShown,
      onClose: (TanreiSheetCloseReason reason) => setState(() => filtersShown = false),
      headline: 'Filters',
      showCloseButton: true,
      closeButtonSemanticLabel: 'Close filters',
      actions: <Widget>[
        TanreiButton(variant: TanreiButtonVariant.text, onPressed: apply, child: const Text('Apply')),
        TanreiButton(variant: TanreiButtonVariant.text, onPressed: reset, child: const Text('Reset')),
      ],
      child: const FilterForm(),
    ),
  ],
),
```

**React Native**

```tsx
import { View } from 'react-native';
import { Button, SideSheet } from '@tanrei/react-native';

// Standard: at the end of a row. A modal sheet is presented in a transparent Modal.
<View style={{ flex: 1, flexDirection: 'row' }}>
  <Results style={{ flex: 1 }} />
  <SideSheet
    variant={wide ? 'standard' : 'modal'}
    open={open}
    onClose={(reason) => setOpen(false)}
    headline="Filters"
    closable
    closeLabel="Close filters"
    actions={
      <>
        <Button variant="text" onPress={apply}>Apply</Button>
        <Button variant="text" onPress={reset}>Reset</Button>
      </>
    }
  >
    <FilterForm />
  </SideSheet>
</View>
```

## Specs

- Category: Containment
- Level: composed
- Listing: default
- Built from: Modal layer
- Page: https://tanrei.chnotchy.com/components/side-sheet/
- Spec: https://github.com/chnotchy/tanrei/blob/main/specs/side-sheet.spec.json

### Availability

| Design system | Has it | Notes |
| --- | --- | --- |
| Tanrei (`tanrei`) | Yes | — |
| 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-side-sheet>`, registered by importing `@tanrei/web` (or only its own module, `@tanrei/web/components/side-sheet`).
- React: `SideSheet` from `@tanrei/react`.

| Platform | Name | Status |
| --- | --- | --- |
| Web | `tanrei-side-sheet` | lagging |
| SwiftUI | `TanreiSideSheet` | lagging |
| Jetpack Compose | `TanreiSideSheet` | lagging |
| Flutter | `TanreiSideSheet` | lagging |
| React Native | `SideSheet` | lagging |

Names a platform gives in its own idiom:

| Spec | Web | SwiftUI | Jetpack Compose | Flutter | React Native |
| --- | --- | --- | --- | --- | --- |
| `open` (prop) | `open` | `isPresented` | `visible` | `open` | `open` |
| `closable` (prop) | `closable` | `closable` | `closable` | `showCloseButton` | `closable` |
| `closeLabel` (prop) | `closeLabel` | `closeLabel` | `closeLabel` | `closeButtonSemanticLabel` | `closeLabel` |
| `close` (event) | `close` | `onClose` | `onClose` | `onClose` | `onClose` |

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

- `container`: The panel at the end edge, the full height of its parent (standard) or of the window (modal). Standard: part of the layout. Modal: above the content, the corners that face the content rounded. Its color reaches under the system insets at its end, top and bottom.
- `outline`: The start edge of a standard sheet, which sets it apart from the content beside it.
- `scrim` (optional): The modal layer's scrim (MDL-1): it dims everything behind a modal sheet; a press on it asks the sheet to close.
- `header` (optional): The row at the top that holds the headline and the close button. It stays in place while the content scrolls.
- `headline` (optional): What the sheet is about ("Filters"). It is the sheet's accessible name.
- `close-button` (optional): An icon-only Button of the small size showing the close glyph at the end of the header, in the variant comp.side-sheet.close-button.variant names (tonal in the default system), as every host's close button is. The sheet places it and chooses its variant; everything else it reads from Button's own tokens.
- `content`: Whatever the product puts in the sheet. The sheet insets it, hands it a content color and scrolls it between the header and the actions; it does not lay it out.
- `divider` (optional): Hairlines across the sheet: above the actions, drawn while there are actions; and below the header, drawn whenever the header is in the default system, or only while the content is scrolled away from its top under dividerVisibility scroll.
- `actions` (optional): Tanrei Buttons at the bottom of the sheet, each marked confirming or dismissive, laid out as a full-width Button group: a row the actions share equally, or a column when they do not fit. A Button whose variant the product did not set is tonal in the default system. At least one in a modal sheet; optional in a standard one.

### Props

| Prop | Type | Default | Web attribute | Description |
| --- | --- | --- | --- | --- |
| `variant` | `enum`: `standard`, `modal` | `"standard"` | `variant` | Standard sits beside the content and takes its width in the layout (a layout region); modal slides over the content with a scrim and holds focus until it closes (a modal overlay). One product uses both: standard where the window is wide enough, modal where it is not. A design system may add values. |
| `open` | `boolean` | `false` | `open` | Whether the sheet is shown: for a standard sheet, whether it takes its place in the layout; for a modal one, whether it is presented. The product opens it, and closes it in answer to close; on SwiftUI, where it is a binding, the sheet writes false itself. |
| `headline` | `string` | `""` | `headline` | What the sheet is about, drawn in its header and used as its accessible name. Required. |
| `closable` | `boolean` | `true` | `not-closable` (turns it off) | Draws the close button at the end of the header. True by default, in both variants: a standard sheet has no other way for the person to close it, and a modal one shows a way out where the person reads. Set it to false only where the product's own control, or one of the sheet's actions, closes the sheet. |
| `closeLabel` | `string` | `""` | `close-label` | The close button's accessible name ("Close filters"). Required while closable is true, which is the default. |
| `dividerVisibility` | `enum`: `auto`, `always`, `scroll` | `"auto"` | `divider-visibility` | When the divider below the header is drawn. always: whenever the header is drawn, at rest as well as while the content is scrolled, as the divider above the actions always is. scroll: only while the content is scrolled away from its top. auto takes comp.side-sheet.divider.visibility, the design system's answer (always in the default system). |

### Events

| Event | Description |
| --- | --- |
| `close` | The sheet asks to be closed: its close button, or for a modal sheet a press on the scrim, Escape, the platform's back or a drag toward its edge. Carries which of these it was, named close, scrim, escape, back or drag (in the platform's casing). |

### Slots

| Slot | Description |
| --- | --- |
| `default` | The content, below the header. A fixture's content string is plain text, which takes sys.typescale.body in the content color (SSH-10). |
| `actions` | The action items: Tanrei Buttons, each marked confirming or dismissive; at least one in a modal sheet (SSH-16). The sheet places them (SSH-11) and gives those without a variant its own (SSH-17). A fixture fills it through its items. |

### Item: `action`

One action at the foot of the sheet: a Tanrei Button, placed by the sheet as a full-width Button group places its items and given the sheet's variant unless the product set one.

It is a Button.

Names: Web `tanrei-button`, SwiftUI `TanreiButton`, Jetpack Compose `TanreiButton`, Flutter `TanreiButton`, React Native `Button`.

| Prop | Type | Default | Web attribute | Description |
| --- | --- | --- | --- | --- |
| `variant` | `string` | `""` | `variant` | The Button's variant (filled, tonal, elevated, outlined, text, or one a system added). Empty, the default: the sheet gives it the variant comp.side-sheet.actions.variant names, tonal in the default system (SSH-17). Set it to give one action another look. |
| `disabled` | `boolean` | `false` | `disabled` | As the Button's disabled. A disabled action keeps its place and its share of the width. |
| `confirming` | `boolean` | `false` | — | The action completes the task (Apply, Save, Show results). Placed at the end of a row and at the top of a column (BGR-13, BGR-14). It decides the place only, never the look (BGR-19). |
| `dismissive` | `boolean` | `false` | — | The action backs out of the task (Cancel, Discard changes). Placed at the start of a row and at the bottom of a column (BGR-13, BGR-14). It decides the place only, never the look (BGR-19). |

| Event | Description |
| --- | --- |
| `click` | The action was activated, as the Button's click. The sheet does not close by itself (SSH-18). |

| Slot | Description |
| --- | --- |
| `label` | The Button's label, as its default slot. A fixture item's content is this label. |

### States

`enabled`

### Accessibility

- Role: `dialog`
- Labeling: The headline is the sheet's accessible name and is exposed as a heading: the modal dialog's name, or the standard sheet's complementary region's. The close button is named by closeLabel. Each action is named by its own label; confirming and dismissive are not announced, and the actions are read in the order they are placed (BGR-15). The dividers are decorative.
- Minimum target size: yes

| Keys | Action |
| --- | --- |
| Tab / Shift+Tab | Moves focus through the close button, the content's focusable elements and the actions, in that order, the actions in the order they are placed (BGR-15). In an open modal sheet it wraps and never leaves the sheet; from an open standard sheet it moves on to the content, and the sheet stays open. |
| Enter or Space | Activates the focused close button (close, reason close) or action (its click; the sheet does not close by itself, SSH-18). The sheet adds no default action to Enter. |
| Escape | Asks an open modal sheet to close (close, reason escape); with stacked overlays, only the topmost. A standard sheet ignores it. |

- The sheet has no target of its own; its close button and its actions are Tanrei Buttons, which meet the minimum target themselves (BTN-5). comp.side-sheet.actions.gap keeps each action's whole target in a column in the default system.
- A modal sheet offers at least one action (SSH-16): it holds focus until the person is done, so a person using a screen reader or a switch finds a way to finish the task where they finish reading it, not only a way out. The close button, Escape, back and the scrim still dismiss it. A standard sheet sits beside the content, which the person keeps working in, so it may have no action.
- Placement is by task, not by code order: in a row the dismissive action is at the start and the confirming one at the end; in a column the confirming one is on top. Focus and screen readers follow the placed order.
- Dragging is never the only way (WCAG 2.5.7): a modal sheet also closes with its close button, Escape, back or a press on the scrim.
- The standard form is a layout region, not an overlay: opening it moves focus in and closing it returns focus, and focus leaving it never closes it. The modal form is a modal overlay. The web presents it with a modal \<dialog> element (showModal gives inertness and the top layer; its cancel event is cancelled and becomes close with the reason escape); Compose draws it in a window of its own (a Dialog, as TanreiDialog and the modal drawer are) and Flutter as a controlled overlay in a Stack over the page, each with a scrim, trapping focus and answering back; SwiftUI presents it as the dialog is, with a full-screen cover on iOS; React Native presents it in a transparent Modal.
- Opening a modal sheet by a swipe from the screen edge is left out, as for the drawer: the product opens it from a button.

### Behaviour

Requirements in EARS form, each with its stable id.

- **SSH-1** WHILE variant is standard THE side sheet SHALL take its width in the layout at the end of the row the product places it in WHILE open is true, and no width and no presence to assistive technology or focus WHILE open is false; WHEN open changes it SHALL slide in or out at the end edge while the content beside it resizes, over comp.side-sheet.motion.enter-duration with comp.side-sheet.motion.enter-easing when opening and comp.side-sheet.motion.exit-duration with comp.side-sheet.motion.exit-easing when closing, and at once where motion is reduced. A standard sheet SHALL draw no scrim, SHALL NOT keep focus inside it, SHALL let Tab and Shift+Tab move focus out of it without closing it, and SHALL ignore Escape, the platform's back and drags (a standard sheet is a layout region, not an overlay).
- **SSH-2** WHEN open becomes true WHILE variant is modal THE side sheet SHALL slide in from the window's end edge over the content on its modal layer, fading the layer's scrim in comp.side-sheet.scrim.color and comp.side-sheet.scrim.blur in over the rest of the window in step with it (MDL-1, MDL-7), over comp.side-sheet.motion.enter-duration with comp.side-sheet.motion.enter-easing; WHEN open becomes false it SHALL slide out to the end edge from wherever it is and fade the scrim out, over comp.side-sheet.motion.exit-duration with comp.side-sheet.motion.exit-easing. WHERE motion is reduced it SHALL fade in and out without sliding, or appear and disappear at once on a platform whose reduced-motion setting removes every animation (Android's). WHILE it is open THE side sheet SHALL make everything behind it inert and keep focus inside it, as its modal layer does (MDL-2, MDL-4).
- **SSH-3** WHEN open changes from false to true THE side sheet SHALL move focus to the element in it that the product marked for initial focus (the platform's own mark, named in the platform notes) or, without one, to its container, so that assistive technology reads the headline first; WHEN it closes while focus is inside it THE side sheet SHALL return focus to the element that had it when the sheet opened or, where that element no longer exists or cannot take focus, to the platform's default. Focus SHALL move when the sheet opens or closes, not when its motion ends. This holds for both variants (a modal sheet moves and returns focus as its modal layer does, MDL-3, MDL-5); a standard sheet mounted with open true SHALL NOT move focus, and a modal sheet mounted with open true SHALL move focus in as if it had just opened, because it makes everything behind it unfocusable and focus must be somewhere it can reach.
- **SSH-4** WHILE variant is modal and the sheet is open, WHEN the user presses the scrim, presses Escape, uses the platform's back, as its modal layer answers them (MDL-6), or drags the sheet toward its end edge past half its width or flings it that way, THE side sheet SHALL emit close exactly once with the reason scrim, escape, back or drag; a drag SHALL follow the finger or pointer once it passes the platform's touch slop, and a released drag that does not ask to close SHALL slide the sheet back over comp.side-sheet.motion.enter-duration with comp.side-sheet.motion.enter-easing (at once where motion is reduced). The fling, the touch slop and the stillness after which a release is no fling are those BSH-9 names for the bottom sheet: the platform's own, or 0.5 points per millisecond, 8 points and 40 milliseconds where the platform names none.
- **SSH-5** WHILE closable is true THE side sheet SHALL draw at the end of its header an icon-only Button of the small size showing the close glyph and named by closeLabel, in the variant comp.side-sheet.close-button.variant names, given through the channel a Button reads from the component that places it, and otherwise unrestyled: it reads Button's own tokens, answers hover, focus and press as any Button does and keeps its own minimum target (BTN-5); WHEN the user activates it THE side sheet SHALL emit close exactly once with the reason close, in either variant. WHILE closable is true and closeLabel is empty it SHALL still draw the button, and in debug builds report that the button has no accessible name.
- **SSH-6** WHEN the side sheet has emitted close THE side sheet SHALL be closed through its binding where open is one (SwiftUI), and by the product setting open to false where open is a plain value (web, Compose, Flutter, React Native); a released drag that asked to close SHALL hold where it left the sheet for one frame, then slide out from there IF open has become false, or slide back IF open is still true (the product declined to close it).
- **SSH-7** THE side sheet SHALL be comp.side-sheet.container.width wide beside the end system inset — WHILE variant is modal never wider than the window less sys.target.touch, so that a strip of scrim stays pressable — and the full height of its parent (standard) or of the window (modal), filled with its variant's container color (comp.side-sheet.container.color.standard or comp.side-sheet.container.color.modal), raised by its variant's elevation (comp.side-sheet.container.elevation.standard, comp.side-sheet.container.elevation.modal), with the corners at its start edge rounded by its variant's shape (comp.side-sheet.container.shape.standard, comp.side-sheet.container.shape.modal) eased by sys.shape.corner-smoothing (0 is a quarter circle, 0.6 the iOS continuous corner; a platform with only the OS curve draws it for any amount above 0) and square corners at its end edge, and edged at its start by comp.side-sheet.outline.width of its variant's outline color (comp.side-sheet.outline.color.standard, comp.side-sheet.outline.color.modal); right-to-left layouts SHALL put it at the left edge, mirrored.
- **SSH-8** THE side sheet SHALL lay out, top to bottom: WHILE headline is not empty or closable is true, the header, a row at least comp.side-sheet.header.height high holding the headline from comp.side-sheet.container.padding-inline after the start edge and, WHILE closable is true, the close button ending comp.side-sheet.header.padding-inline-end before the end edge, comp.side-sheet.header.gap after the headline, both centred in the row; then the content, inset by comp.side-sheet.container.padding-inline from the start and end edges, starting directly below the header or, without one, comp.side-sheet.container.padding-block below the top edge; then, WHILE the sheet has at least one action, the divider and the actions pinned to the bottom (SSH-11), or else comp.side-sheet.container.padding-block of space below the content. It SHALL extend its container under the system insets at its end, top and bottom and place the header, content and actions inside them.
- **SSH-9** WHILE headline is not empty THE side sheet SHALL draw it in comp.side-sheet.headline.typescale and comp.side-sheet.headline.color, wrapping onto more lines rather than truncating and growing the header with it, and SHALL expose it as a heading. THE side sheet SHALL set the headline's letter-spacing by the script of its text, as every title is set (PRS-20): no negative letter-spacing WHERE its language is Chinese, Japanese or Korean, and none WHERE its script joins its letters or stacks marks on them.
- **SSH-10** THE side sheet SHALL hand its content comp.side-sheet.content.color as the platform's inherited foreground (the web's inherited color, SwiftUI's foreground style, Compose's content color, Flutter's default text and icon style, React Native's Tanrei text context); plain text given as content, where the platform must style it, SHALL take sys.typescale.body. WHILE the content is taller than the room between the header and the actions THE side sheet SHALL scroll it there, keeping the header and the actions in place, and SHALL let assistive technology and keyboard focus scroll it.
- **SSH-11** WHILE the sheet has at least one action THE side sheet SHALL draw a divider of comp.side-sheet.divider.width in comp.side-sheet.divider.color across its full width below the content, whether or not the content scrolls, and below it lay out its actions as a standard Button group lays out its items (BGR-12 to BGR-19), comp.side-sheet.actions.gap apart, comp.side-sheet.container.padding-inline from each side edge and comp.side-sheet.actions.padding-block above and below them, in the order the group gives them — dismissive at the start and confirming at the end of a row, confirming on top and dismissive at the bottom of a column, unflagged actions between them in the order given — with focus and reading order following that order (BGR-15). WHILE comp.side-sheet.actions.arrangement is fill it SHALL make them a full-width group across the sheet's inner width, the actions sharing a row equally (BGR-17) or each as wide as the column; WHILE it is start it SHALL keep them at their own widths, the row aligned to the start edge, and a column as wide as its widest action and aligned to the start. It SHALL place them in a row WHILE every action's label fits its share on one line (fill) or the row at its own widths fits the inner width (start), and otherwise in a column, re-deciding when the sheet's width or the text size changes. WHEN the layout direction is right-to-left it SHALL place them as a Button group places them right to left (BGR-8). It SHALL hide the divider from assistive technology.
- **SSH-12** THE side sheet SHALL expose its container, WHILE variant is modal, as its modal layer's modal dialog (MDL-10) named by headline and, WHILE variant is standard, as a complementary region named by headline (the web's aside landmark); WHILE headline is empty it SHALL still render, and in debug builds report that it has no accessible name.
- **SSH-13** WHEN variant names a value that the active design system does not have THE side sheet SHALL render with the default value's tokens, and in debug builds report the unknown value.
- **SSH-14** WHILE the text size is enlarged THE side sheet SHALL keep its width, grow its header with the headline (its height is a minimum), scroll its content (SSH-10), stack its actions once a label no longer fits its share (SSH-11), and SHALL NOT scale the close button beyond what the Button itself does.
- **SSH-15** WHEN a dialog, a menu or another modal sheet opens from a modal side sheet THE side sheet SHALL stay below it, become inert with the rest of the window, and on the other overlay's closing receive back the focus that overlay returns, as its modal layer does (MDL-8, MDL-9); Escape SHALL dismiss only the topmost overlay.
- **SSH-16** WHILE variant is modal, IF the sheet opens with no action THE side sheet SHALL still open and lay out its other parts, and in debug builds SHALL report as an error that a modal side sheet must offer at least one action; a platform whose modal sheet has an API of its own that can require an action (a required, non-empty builder or list of actions) SHALL require it there, and one that can count its actions only when the sheet opens SHALL count them then. WHILE variant is standard THE side sheet SHALL accept having no action and report nothing, and SHALL then draw neither the divider above the actions nor the actions (SSH-8).
- **SSH-17** WHILE an action's variant is empty THE side sheet SHALL give that Button the variant comp.side-sheet.actions.variant names, through the channel a Button reads from the component that places it, so that the Button renders from that variant's tokens and states as it would with the variant set; WHILE an action's variant is set THE side sheet SHALL leave it as set. THE side sheet SHALL NOT change an action's size or tokens, and SHALL NOT change its look or emphasis for its confirming or dismissive (BGR-19).
- **SSH-18** WHEN the user activates an action THE side sheet SHALL let the Button emit its own click and SHALL NOT close, emit close or otherwise answer it itself, whether the action is confirming, dismissive or neither; the product closes the sheet from the action's handler, as it does in answer to close.
- **SSH-19** WHILE the header is drawn THE side sheet SHALL draw a divider of comp.side-sheet.divider.width in comp.side-sheet.divider.color across its full width below the header, hidden from assistive technology: WHILE its divider visibility (SSH-23) is always, at rest as well as while the content is scrolled, as the divider above the actions is drawn whether or not the content scrolls (SSH-11); WHILE it is scroll, only WHILE the content is scrolled away from its top. WHILE there is no header it SHALL draw none there. It SHALL show and hide this divider at once, without motion.
- **SSH-20** WHILE the on-screen keyboard covers the bottom of the sheet THE side sheet SHALL keep its header in place, raise its divider and actions to sit directly above the keyboard, scroll the content in the room left between them, and scroll the focused element into that room; WHEN the keyboard hides it SHALL return the actions to the bottom edge. It SHALL move them as the platform moves content for its keyboard, and at once where motion is reduced.
- **SSH-21** THE side sheet SHALL take its layout direction from where it is used — the direction of the nearest ancestor that sets one, and the platform's own where none does — and SHALL have no direction setting of its own; WHEN that direction changes while the side sheet is shown THE side sheet SHALL draw itself for the new direction at once, without a motion of its own, keeping its open state and its focus.
- **SSH-22** THE side sheet SHALL lay out its headline as text of its own direction, isolated from the text around it: each takes the base direction of its first strong character, or the layout direction where it has none, so that a left-to-right word, a number with its sign or unit, a telephone number and an address keep their own order in a right-to-left layout and reorder nothing beside them; THE side sheet SHALL still place the headline and align its lines by the layout direction, not by the text's own.
- **SSH-23** THE side sheet SHALL draw the divider below its header (SSH-19) as its dividerVisibility names: WHILE dividerVisibility is auto, as comp.side-sheet.divider.visibility names, which follows sys.behavior.divider-visibility unless a design system sets the side sheet apart; WHILE dividerVisibility is always or scroll, as that value names, whatever the tokens say. WHEN dividerVisibility, or the token it follows, changes THE side sheet SHALL draw the other form at once, moving no part and keeping the scroll position and focus; WHEN dividerVisibility names a value the side sheet does not define THE side sheet SHALL treat it as auto and in debug builds report the unknown value. A platform that cannot draw a choice SHALL fall back to the first value, always, and state that in its README.
- **SSH-24** 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 side sheet 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 its container (SSH-12) — its dialog WHILE variant is modal, its complementary region otherwise — an id reference by the elements it names in the host's tree or a tree around it, a description after its own. WHILE headline is not empty it is the container's name, over a name given so; WHILE headline is empty, a name given so is the container's name and SHALL NOT be reported as having none in debug builds. 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 side sheet SHALL take it off that element.

### 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.side-sheet.…` → `--tanrei-comp-side-sheet-…`).

#### `tanrei.comp.side-sheet`

| Token | Type | Value |
| --- | --- | --- |
| `comp.side-sheet.container.color.standard` | `color` | `{tanrei.sys.color.surface}` |
| `comp.side-sheet.container.color.modal` | `color` | `{tanrei.sys.color.surface-container-low}` |
| `comp.side-sheet.container.elevation.standard` | `shadow` | `{tanrei.sys.elevation.level0}` |
| `comp.side-sheet.container.elevation.modal` | `shadow` | `{tanrei.sys.elevation.level2}` |
| `comp.side-sheet.container.shape.standard` | `dimension` | `{tanrei.sys.shape.corner.none}` |
| `comp.side-sheet.container.shape.modal` | `dimension` | `{tanrei.sys.shape.corner.large}` |
| `comp.side-sheet.container.width` | `dimension` | `320px` |
| `comp.side-sheet.container.padding-inline` | `dimension` | `{tanrei.sys.space.space300}` |
| `comp.side-sheet.container.padding-block` | `dimension` | `{tanrei.sys.space.space300}` |
| `comp.side-sheet.outline.color.standard` | `color` | `{tanrei.sys.color.outline-variant}` |
| `comp.side-sheet.outline.color.modal` | `color` | `{"colorSpace":"srgb","components":[0,0,0],"alpha":0,"hex":"#000000"}` |
| `comp.side-sheet.outline.width` | `dimension` | `{tanrei.sys.border.hairline}` |
| `comp.side-sheet.scrim.color` | `color` | `{tanrei.comp.modal-layer.scrim.color}` |
| `comp.side-sheet.scrim.blur` | `dimension` | `{tanrei.comp.modal-layer.scrim.blur}` |
| `comp.side-sheet.header.height` | `dimension` | `64px` |
| `comp.side-sheet.header.gap` | `dimension` | `{tanrei.sys.space.space100}` |
| `comp.side-sheet.header.padding-inline-end` | `dimension` | `{tanrei.sys.space.space150}` |
| `comp.side-sheet.close-button.variant` | `number` | `1` |
| `comp.side-sheet.headline.color` | `color` | `{tanrei.sys.color.on-surface}` |
| `comp.side-sheet.headline.typescale` | `typography` | `{tanrei.sys.typescale.heading-5}` |
| `comp.side-sheet.content.color` | `color` | `{tanrei.sys.color.on-surface}` |
| `comp.side-sheet.divider.color` | `color` | `{tanrei.sys.color.outline-variant}` |
| `comp.side-sheet.divider.width` | `dimension` | `{tanrei.sys.border.hairline}` |
| `comp.side-sheet.divider.visibility` | `number` | `{tanrei.sys.behavior.divider-visibility}` |
| `comp.side-sheet.actions.gap` | `dimension` | `{tanrei.sys.space.space200}` |
| `comp.side-sheet.actions.arrangement` | `number` | `0` |
| `comp.side-sheet.actions.variant` | `number` | `1` |
| `comp.side-sheet.actions.padding-block` | `dimension` | `{tanrei.sys.space.space200}` |
| `comp.side-sheet.motion.enter-duration` | `duration` | `{tanrei.sys.motion.role.appear.sheet.enter}` |
| `comp.side-sheet.motion.enter-easing` | `cubicBezier` | `{tanrei.sys.motion.easing.enter}` |
| `comp.side-sheet.motion.exit-duration` | `duration` | `{tanrei.sys.motion.role.appear.sheet.exit}` |
| `comp.side-sheet.motion.exit-easing` | `cubicBezier` | `{tanrei.sys.motion.easing.exit}` |

## Guidelines

### When to use

Use a side sheet for content that supports what the person is working on without replacing it: filters for a list, the details of a selected row, the properties of a selected object. On a wide window it sits beside the content, so the person can change a filter and see the results change. On a compact window the same sheet slides over the content, and the person finishes with it or dismisses it before going back.

On a phone, a [bottom sheet](https://tanrei.chnotchy.com/components/bottom-sheet/) often fits better: it rises from the edge within reach of the thumb. Use a [dialog](https://tanrei.chnotchy.com/components/dialog/) for a decision the task cannot go on without, and a [navigation drawer](https://tanrei.chnotchy.com/components/navigation-drawer/), at the start edge, for the product’s destinations.

### Standard or modal

| Variant | What it is | Use for |
| --- | --- | --- |
| Standard (default) | A layout region: a panel at the end of the row, set apart from the content by a hairline at its start edge. The content beside it resizes as it opens and closes. It draws no scrim, and it stays open while the person works in the content. | Wide windows, where the sheet can stay open beside the content. |
| Modal | A modal overlay: a raised panel with its corners toward the content rounded, sliding in from the end edge over a scrim. Everything behind it is inert, and focus stays inside until it closes. | Compact windows, and tasks that must be finished or dismissed before the person goes on. |

A standard sheet is part of the layout, like a standard navigation drawer or an app bar: focus leaving it never closes it, because closing a panel whenever Tab moved on would make it unusable from the keyboard. Its modal form is an overlay, and everything a modal overlay promises applies.

A modal sheet is never as wide as a narrow window. It stays at least one touch target narrower, so a strip of scrim is always there to press. A design system may add variants.

### Parts

| Part | Set with | Notes |
| --- | --- | --- |
| Headline | `headline` | Required. What the sheet is about, such as “Filters”. It is the sheet’s accessible name and a heading, and it wraps rather than being cut. |
| Close button | `closable`, `closeLabel` | A small icon-only Button with the `close` glyph at the end of the header, tonal in the default system, as every close button in Tanrei is (a bare glyph under m3-like). Drawn by default; set `closable` to false (the `not-closable` attribute) where your own control or an action closes the sheet. The sheet draws it and wires it to `close`; you give it a label. |
| Content | the default slot | Whatever the sheet is for. The sheet insets it, hands it a content color and scrolls it between the header and the actions. |
| Actions | the actions slot | Tanrei Buttons, each marked `confirming` or `dismissive`, under a divider. Required in a modal sheet, optional in a standard one. The sheet places them and draws those without a variant as tonal; it never restyles them otherwise. |

The actions share the sheet’s inner width equally, with 16 between them. In a row, the dismissive action is at the start and the confirming one at the end, with unmarked actions between them in the order given. When a label would wrap in its share, they stack into a column with the confirming action on top. Focus and screen readers follow the placed order. Set one Button’s `variant` to give that action another look; a product that wants another look for every sheet sets it once in its layer (`actions.variant`, and `actions.arrangement` for a compact row at the start, or `close-button.variant` for the close button).

The header and the actions stay in place while the content scrolls. The divider above the actions is always drawn, and so, in the default system, is a matching divider below the header: both are edges of a panel that stays beside the page. Set `dividerVisibility` to `scroll` (`divider-visibility` on the web) to draw the one below the header only while the content is scrolled away from its top; `cupertino` and `m3-like` choose that for every sheet. While the on-screen keyboard covers the bottom of the sheet, the actions rise to sit just above it, and the content scrolls in the room left. The sheet’s color reaches under the system insets at its end, top and bottom, and its header, content and actions stay inside them. In a right-to-left layout the sheet sits at the left edge, mirrored.

### Opening, focus and closing

- **Opening a standard sheet.** It slides in at the end edge while the content beside it makes room. Focus moves to the element you marked, or to the sheet, so its headline is read first. A sheet that is open from the start moves no focus.
- **Working beside a standard sheet.** Tab moves from the sheet into the content, and the sheet stays open. Escape, back and drags do nothing to it.
- **Opening a modal sheet.** It slides in from the end edge while the scrim fades in over the rest of the window. Focus moves in as for the standard sheet and stays inside: Tab from the last focusable element goes to the first, and Shift+Tab from the first goes to the last. Everything behind it is inert. A modal sheet that is open from the start moves focus in too, because nothing behind it can take focus.
- **Closing.** The sheet slides out to the end edge and, for a modal sheet, the scrim fades. If focus was inside, it returns to the element that had it when the sheet opened.
- **Dragging a modal sheet.** It follows the finger once it passes the platform’s touch slop. A release past half its width toward the end edge, or a fling that way, asks it to close with the reason `drag`. A shorter, slower drag slides it back. The fling and the slop are those the [bottom sheet](https://tanrei.chnotchy.com/components/bottom-sheet/) uses.
- **Stacking.** A dialog, a menu or another modal sheet opened from a modal side sheet stacks above it. Escape dismisses only the topmost.
- **No edge swipe to open.** The sheet opens from a button, never from a swipe at the screen’s edge.
- Where motion is reduced, a standard sheet opens and closes at once, and a modal sheet fades without sliding.

### Do

- Write a short headline that names the sheet’s content: “Filters”, “Details”, “Properties”.
- Keep a standard sheet’s close button, which it draws by default, unless a control of your own, such as a toggled Filters button, closes it.
- Use the same content in both forms, so the product switches between them by window width alone.
- Mark every action `confirming` or `dismissive`, and let the sheet place them.
- Give a modal sheet an action that finishes the task, such as Apply, not only ways out.

### Don’t

- Don’t use a modal side sheet on a window wide enough for a standard one.
- Don’t put the product’s navigation in a side sheet. Use a [navigation drawer](https://tanrei.chnotchy.com/components/navigation-drawer/).
- Don’t restyle the close button or the buttons in the actions slot beyond their `variant`, or order the actions by hand.
- Don’t open a side sheet the person did not ask for.

## Accessibility

### What the component handles

- A modal sheet is exposed as a modal dialog named by its headline. A standard sheet is a complementary region named by its headline, the aside landmark on the web.
- The headline is exposed as a heading. The divider is hidden from assistive technology.
- Opening moves focus to the element you marked, or to the sheet. Closing returns focus to the element that had it when the sheet opened. This holds for both forms.
- In a modal sheet, Tab and Shift+Tab wrap inside it, everything behind it is inert and hidden from assistive technology, and Escape, back and a press on the scrim ask it to close. With stacked overlays, only the topmost is dismissed.
- From a standard sheet, Tab moves on to the content, and the sheet stays open. It ignores Escape and back.
- The close button is a Tanrei icon-only Button named by `closeLabel`, and the actions are Tanrei Buttons. Each meets the minimum target itself, and the 16 between stacked actions keeps each whole target.
- Focus and screen readers meet the actions in the placed order, the same order a sighted person sees. The actions stay above the on-screen keyboard, so they stay reachable while a person types in the sheet.
- Enter and Space activate the focused close button or action. The sheet adds no default action to Enter.
- A drag is never the only way to close: the close button, Escape, back and the scrim do it too.
- Larger text keeps the sheet’s width, grows its header with the headline, and scrolls the content.
- Debug builds report a sheet without a headline, a close button without a `closeLabel`, a modal sheet opened with no action, and a variant the design system does not have.

Known platform gaps:

- SwiftUI, Compose, Flutter and React Native: `dividerVisibility` waits for those platforms to catch up. They draw the divider below the header only while the content is scrolled, as `scroll` does.
- Web: in Firefox a modal sheet leaves at once instead of sliding out, as the dialog does. Touch drags and the real safe-area insets are not covered by a test.
- SwiftUI has neither a dialog nor a complementary-region role: the sheet is a container named by its headline, with the modal trait while modal. SwiftUI cannot give keyboard focus to the sheet itself: without a mark, VoiceOver moves to the headline and keyboard focus stays where it was. Closing gives keyboard focus back to nothing; on iOS the modal cover gives VoiceOver back, and a standard sheet lets it go. A standard sheet is not clipped while it slides, so place it at the trailing edge of the window’s row. On macOS a modal sheet covers only the view the modifier is attached to, so attach it to the window’s root.
- SwiftUI: plain text in the content takes the body font without its line height, so it is not placed exactly where the other platforms place it. Escape and the iOS escape gesture are wired but no test presses them.
- Compose: while a modal sheet closes, its window keeps focus until the exit motion ends. Until it catches up, the actions are called in a `RowScope`, but the sheet lays them out itself, so `weight` and the alignments do nothing. Its drags are verified under Robolectric only, not on a device.
- Flutter: a standard sheet is a named container, not a complementary landmark, because Flutter 3.32 has no such role. The sheet has not yet been checked with TalkBack and VoiceOver on a device.
- React Native cannot tell which element had focus, so when the sheet closes, focus goes where the platform puts it, not back to the element that opened it. The Modal, the drag, the width animation and the insets are verified in Jest only, never on a device.
- Under `m3-like`, the sheet keeps the default system’s width and the hairline edge of the standard form: Material’s values wait for the fidelity reference to cover the side sheet.

### What you need to do

- Give every sheet a `headline`. It is the sheet’s name.
- Give the close button, drawn by default, a `closeLabel` that says what it closes, such as “Close filters”.
- Close the sheet yourself: set `open` to false in answer to `close` (the `close` event on the web, `onClose` on Compose, Flutter and React Native). On SwiftUI the sheet writes false to the binding for you.
- Give a standard sheet a way to close it: its close button, or a control of your own with a label.
- Give a modal sheet at least one action, mark each one `confirming` or `dismissive`, and close the sheet from its handler.
- Open the sheet from a visible button with its own label.
- Mark initial focus where it helps, such as the first filter.