# Split View

Sidebar, list and detail columns side by side on wide screens, shown one at a time with back navigation on phones.

Split View is an open-source mobile pattern from suiss/uim: components composed into a flow for React Native and Expo, with SwiftUI and Jetpack Compose versions built from the same design tokens. The @esuiss/uim CLI copies its source into your project, so you own the code.

Source: https://uim.suiss.app/docs/patterns/split-view

![Preview](https://uim.suiss.app/previews/patterns-split-view--default.light.webp)

```tsx
import * as React from "react"
import { View } from "react-native"
import { SplitView, type SplitViewColumn, SplitViewDetail, SplitViewItem, SplitViewList, SplitViewSidebar } from "@/components/patterns/split-view"
import { Text } from "@/components/ui/text"

const mailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

const messages = [
  {
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
  },
  {
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
  },
  {
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space.",
  },
] as const

function MailExample({
  withSidebar = true,
  defaultColumn,
  breakpoint,
}: {
  withSidebar?: boolean
  defaultColumn?: SplitViewColumn
  breakpoint?: number
}) {
  const [mailbox, setMailbox] = React.useState("Inbox")
  const [messageId, setMessageId] = React.useState<string>("order")
  const message = messages.find((item) => item.id === messageId) ?? messages[0]

  return (
    <SplitView defaultColumn={defaultColumn} breakpoint={breakpoint}>
      {withSidebar ? (
        <SplitViewSidebar title="Mailboxes">
          {mailboxes.map((name) => (
            <SplitViewItem
              key={name}
              isActive={mailbox === name}
              onPress={() => setMailbox(name)}
            >
              {name}
            </SplitViewItem>
          ))}
        </SplitViewSidebar>
      ) : null}
      <SplitViewList title={mailbox}>
        {messages.map((item) => (
          <SplitViewItem
            key={item.id}
            isActive={item.id === messageId}
            onPress={() => setMessageId(item.id)}
          >
            <View className="flex-row items-baseline justify-between gap-2">
              <Text className="shrink font-semibold" numberOfLines={1}>
                {item.from}
              </Text>
              <Text className="text-sm text-label-secondary">{item.time}</Text>
            </View>
            <Text numberOfLines={1}>{item.subject}</Text>
            <Text className="text-sm text-label-secondary" numberOfLines={1}>
              {item.body}
            </Text>
          </SplitViewItem>
        ))}
      </SplitViewList>
      <SplitViewDetail title={message.subject}>
        <Text className="text-sm text-label-secondary">
          {message.from} · {message.time}
        </Text>
        <Text className="mt-6">{message.body}</Text>
      </SplitViewDetail>
    </SplitView>
  )
}

export function SplitViewExample() {
  return (
    <MailExample />
  )
}
```

```swift
import EsuissUI
import SwiftUI

struct SplitViewMessage: Identifiable {
  let id: String
  let from: String
  let time: String
  let subject: String
  let body: String
}

let splitViewMailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

let splitViewMessages = [
  SplitViewMessage(
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42."
  ),
  SplitViewMessage(
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan."
  ),
  SplitViewMessage(
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space."
  ),
]

struct SplitViewMail: View {
  var withSidebar = true

  @State private var column: SplitViewColumn
  @State private var mailbox = "Inbox"
  @State private var messageID = "order"

  init(column: SplitViewColumn = .list, withSidebar: Bool = true) {
    _column = State(initialValue: column)
    self.withSidebar = withSidebar
  }

  var message: SplitViewMessage {
    splitViewMessages.first { $0.id == messageID } ?? splitViewMessages[0]
  }

  var body: some View {
    SplitView(column: $column) {
      if withSidebar {
        SplitViewSidebar("Mailboxes") {
          ForEach(splitViewMailboxes, id: \.self) { name in
            SplitViewItem(isActive: mailbox == name, action: { mailbox = name }) {
              Text(verbatim: name)
            }
          }
        }
      }
      SplitViewList(verbatim: mailbox) {
        ForEach(splitViewMessages) { item in
          SplitViewItem(isActive: item.id == messageID, action: { messageID = item.id }) {
            HStack(alignment: .firstTextBaseline, spacing: 8) {
              Text(verbatim: item.from)
                .fontWeight(.semibold)
                .lineLimit(1)
                .frame(maxWidth: .infinity, alignment: .leading)
              Text(verbatim: item.time)
                .textStyle(.sm)
                .foregroundStyle(Color.labelSecondary)
            }
            Text(verbatim: item.subject)
              .lineLimit(1)
            Text(verbatim: item.body)
              .textStyle(.sm)
              .foregroundStyle(Color.labelSecondary)
              .lineLimit(1)
          }
        }
      }
      SplitViewDetail(verbatim: message.subject) {
        Text(verbatim: "\(message.from) · \(message.time)")
          .textStyle(.sm)
          .foregroundStyle(Color.labelSecondary)
        Text(verbatim: message.body)
          .foregroundStyle(Color.label)
          .fixedSize(horizontal: false, vertical: true)
          .padding(.top, 24)
      }
    }
    .containerRelativeFrame(.vertical) { height, _ in height - 32 }
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.style.TextOverflow
import androidx.compose.ui.unit.dp
import com.esuiss.ui.components.Text
import com.esuiss.ui.patterns.SplitView
import com.esuiss.ui.patterns.SplitViewColumn
import com.esuiss.ui.patterns.SplitViewItem
import com.esuiss.ui.theme.EsuissTheme
import com.esuiss.ui.theme.Typography

class SplitViewMessage(
    val id: String,
    val from: String,
    val time: String,
    val subject: String,
    val body: String,
)

val splitViewMailboxes = listOf("Inbox", "Sent", "Drafts", "Archive")

val splitViewMessages = listOf(
    SplitViewMessage(
        "order",
        "Acme Store",
        "09:12",
        "Your order has shipped",
        "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
    ),
    SplitViewMessage(
        "meeting",
        "Jordan Lee",
        "Yesterday",
        "Tomorrow's meeting",
        "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
    ),
    SplitViewMessage(
        "storage",
        "Cloud Drive",
        "Mon",
        "Your storage is almost full",
        "Your cloud storage is 90% full. Upgrade your plan to get more space.",
    ),
)

@Composable
fun SplitViewMail(withSidebar: Boolean = true, defaultColumn: SplitViewColumn = SplitViewColumn.List) {
    var mailbox by rememberSaveable { mutableStateOf("Inbox") }
    var messageId by rememberSaveable { mutableStateOf("order") }
    val message = splitViewMessages.firstOrNull { it.id == messageId } ?: splitViewMessages.first()
    val colors = EsuissTheme.colors
    SplitView(modifier = Modifier.fillMaxWidth().height(640.dp), defaultColumn = defaultColumn) {
        if (withSidebar) {
            SplitViewSidebar(title = "Mailboxes") {
                splitViewMailboxes.forEach { name ->
                    SplitViewItem(isActive = mailbox == name, onClick = { mailbox = name }) {
                        Text(name)
                    }
                }
            }
        }
        SplitViewList(title = mailbox) {
            splitViewMessages.forEach { item ->
                SplitViewItem(isActive = item.id == messageId, onClick = { messageId = item.id }) {
                    Row(
                        modifier = Modifier.fillMaxWidth(),
                        horizontalArrangement = Arrangement.spacedBy(8.dp),
                        verticalAlignment = Alignment.CenterVertically,
                    ) {
                        Text(
                            item.from,
                            modifier = Modifier.weight(1f),
                            style = Typography.base.copy(fontWeight = FontWeight.SemiBold),
                            maxLines = 1,
                            overflow = TextOverflow.Ellipsis,
                        )
                        Text(item.time, style = Typography.sm.copy(color = colors.labelSecondary), maxLines = 1)
                    }
                    Text(item.subject, maxLines = 1, overflow = TextOverflow.Ellipsis)
                    Text(
                        item.body,
                        style = Typography.sm.copy(color = colors.labelSecondary),
                        maxLines = 1,
                        overflow = TextOverflow.Ellipsis,
                    )
                }
            }
        }
        SplitViewDetail(title = message.subject) {
            Text("${message.from} · ${message.time}", style = Typography.sm.copy(color = colors.labelSecondary))
            Text(message.body, modifier = Modifier.padding(top = 24.dp))
        }
    }
}
```

`SplitView` lays out up to three panes: `SplitViewSidebar`, `SplitViewList` and `SplitViewDetail`. When the window is at least `breakpoint` wide (768 by default), they sit side by side in a bordered row, sized 20, 32 and 48 parts.

Below the breakpoint only the current column is shown, full screen and scrollable, with a large title. Pressing a `SplitViewItem` moves to the next column, and a back button titled with the previous pane returns to it. On Android the hardware back button also goes back. Use it for mail, notes or settings screens that drill down.

## Installation

```bash title="Terminal"
npx @esuiss/uim@latest add split-view
```

```bash title="Terminal"
npx @esuiss/uim@latest add split-view --platform swift
```

```bash title="Terminal"
npx @esuiss/uim@latest add split-view --platform kotlin
```

The CLI also adds what it builds on: [Icon](/docs/components/icon), [Text](/docs/components/text).

### Manual

**Uniwind**

1. Install the dependencies:

```bash title="Terminal"
npx expo install cn phosphor-react-native react-native-reanimated react-native-svg react-native-worklets
```

2. Add the pieces it builds on: [Icon](/docs/components/icon), [Text](/docs/components/text), and the primitives `components/primitives/hooks.tsx`.

3. Copy the source into `components/patterns/split-view.tsx`:

```tsx title="uniwind/components/patterns/split-view.tsx"
import { cn } from "cn"
import { CaretLeftIcon, CaretRightIcon } from "phosphor-react-native"
import * as React from "react"
import {
  AccessibilityInfo,
  I18nManager,
  Pressable,
  type Text as RNText,
  ScrollView,
  useWindowDimensions,
  View,
  type ViewProps,
} from "react-native"
import { FadeIn, ReduceMotion } from "react-native-reanimated"
import { useBackHandler } from "@/components/primitives/hooks"
import { AnimatedView } from "@/components/ui/animated-view"
import { Icon } from "@/components/ui/icon"
import { Text, TextClassContext } from "@/components/ui/text"

type SplitViewColumn = "sidebar" | "list" | "detail"

type SplitViewContextProps = {
  isCompact: boolean
  column: SplitViewColumn
  setColumn: (column: SplitViewColumn) => void
  titles: Partial<Record<SplitViewColumn, React.ReactNode>>
  kinds: SplitViewColumn[]
}

const SplitViewContext = React.createContext<SplitViewContextProps | null>(null)

const SplitViewColumnContext = React.createContext<SplitViewColumn | null>(null)

function useSplitView() {
  const context = React.useContext(SplitViewContext)
  if (!context) {
    throw new Error("useSplitView must be used within a <SplitView />")
  }
  return context
}

const NEXT: Record<SplitViewColumn, SplitViewColumn> = {
  sidebar: "list",
  list: "detail",
  detail: "detail",
}

const PREVIOUS: Record<SplitViewColumn, SplitViewColumn | null> = {
  sidebar: null,
  list: "sidebar",
  detail: "list",
}

const RATIO: Record<SplitViewColumn, number> = {
  sidebar: 20,
  list: 32,
  detail: 48,
}

const TITLE_CLASS: Record<SplitViewColumn, string> = {
  sidebar: "px-3 pt-3 pb-2 text-xs font-semibold text-label-secondary",
  list: "",
  detail: "pb-1 text-2xl font-semibold",
}

const PANE_CLASS: Record<SplitViewColumn, string> = {
  sidebar: "p-3 pt-1",
  list: "p-3",
  detail: "p-8",
}

type SplitViewPaneProps = ViewProps & {
  title?: React.ReactNode
}

function SplitView({
  column: columnProp,
  defaultColumn = "list",
  onColumnChange,
  breakpoint = 768,
  className,
  children,
  ...props
}: ViewProps & {
  column?: SplitViewColumn
  defaultColumn?: SplitViewColumn
  onColumnChange?: (column: SplitViewColumn) => void
  breakpoint?: number
}) {
  const { width } = useWindowDimensions()
  const isCompact = width < breakpoint
  const [uncontrolledColumn, setUncontrolledColumn] =
    React.useState(defaultColumn)
  const column = columnProp ?? uncontrolledColumn

  const panes = React.Children.toArray(children).filter(React.isValidElement)
  const titles: SplitViewContextProps["titles"] = {}
  const kinds: SplitViewColumn[] = []
  for (const pane of panes) {
    const kind = PANES.get(pane.type)
    if (!kind) continue
    kinds.push(kind)
    titles[kind] = (pane.props as { title?: React.ReactNode }).title
  }

  const setColumn = React.useCallback(
    (next: SplitViewColumn) => {
      if (columnProp === undefined) setUncontrolledColumn(next)
      onColumnChange?.(next)
    },
    [columnProp, onColumnChange]
  )

  const previous = PREVIOUS[column]
  const backColumn =
    previous && kinds.includes(previous) && titles[previous] !== undefined
      ? previous
      : null

  useBackHandler(isCompact && backColumn !== null, () => {
    if (backColumn) setColumn(backColumn)
  })

  const contextValue = { isCompact, column, setColumn, titles, kinds }

  return (
    <SplitViewContext.Provider value={contextValue}>
      <View
        className={cn(
          "flex-1",
          !isCompact &&
            "flex-row overflow-hidden rounded-2xl border border-separator",
          className
        )}
        {...props}
      >
        {children}
      </View>
    </SplitViewContext.Provider>
  )
}

function SplitViewPane({
  kind,
  title,
  className,
  children,
  ...props
}: SplitViewPaneProps & {
  kind: SplitViewColumn
}) {
  const { isCompact, column, setColumn, titles, kinds } = useSplitView()
  const headingRef = React.useRef<RNText>(null)
  const mountedRef = React.useRef(false)
  const visible = !isCompact || column === kind
  const previous = PREVIOUS[kind]
  const backColumn =
    previous && kinds.includes(previous) && titles[previous] !== undefined
      ? previous
      : null
  const total = kinds.reduce((sum, item) => sum + RATIO[item], 0) || 1

  React.useEffect(() => {
    if (!isCompact || !visible) return
    if (!mountedRef.current) {
      mountedRef.current = true
      return
    }
    const node = headingRef.current
    if (!node) return
    const timeout = setTimeout(() => {
      AccessibilityInfo.sendAccessibilityEvent(node, "focus")
    }, 50)
    return () => clearTimeout(timeout)
  }, [isCompact, visible])

  if (!visible) return null

  const content = (
    <SplitViewColumnContext.Provider value={kind}>
      {isCompact && backColumn ? (
        <Pressable
          role="button"
          onPress={() => setColumn(backColumn)}
          hitSlop={8}
          className="-ms-1.5 min-h-11 flex-row items-center gap-0.5 self-start pe-1.5 active:opacity-60"
        >
          <Icon
            as={CaretLeftIcon}
            weight="bold"
            mirrored={I18nManager.isRTL}
            className="size-4.5 text-link"
          />
          <TextClassContext.Provider value="text-base text-link">
            {typeof titles[backColumn] === "string" ? (
              <Text>{titles[backColumn]}</Text>
            ) : (
              titles[backColumn]
            )}
          </TextClassContext.Provider>
        </Pressable>
      ) : null}
      {title !== undefined && (isCompact || kind !== "list") ? (
        <Text
          ref={headingRef as unknown as React.Ref<typeof RNText>}
          role="heading"
          className={isCompact ? "pb-2 text-3xl font-bold" : TITLE_CLASS[kind]}
        >
          {title}
        </Text>
      ) : null}
      {children}
    </SplitViewColumnContext.Provider>
  )

  if (isCompact) {
    return (
      <AnimatedView
        key={kind}
        entering={FadeIn.duration(200).reduceMotion(ReduceMotion.System)}
        className="flex-1"
        accessibilityLabel={typeof title === "string" ? title : undefined}
        {...props}
      >
        <ScrollView className="flex-1" contentContainerClassName={className}>
          {content}
        </ScrollView>
      </AnimatedView>
    )
  }

  return (
    <View
      className={cn(
        "min-h-0",
        kinds[0] !== kind && "border-s border-separator"
      )}
      style={{ flex: RATIO[kind] / total }}
      accessibilityLabel={typeof title === "string" ? title : undefined}
      {...props}
    >
      <ScrollView
        className="flex-1"
        contentContainerClassName={cn(PANE_CLASS[kind], className)}
      >
        {content}
      </ScrollView>
    </View>
  )
}

function SplitViewSidebar(props: SplitViewPaneProps) {
  return <SplitViewPane kind="sidebar" {...props} />
}

function SplitViewList(props: SplitViewPaneProps) {
  return <SplitViewPane kind="list" {...props} />
}

function SplitViewDetail(props: SplitViewPaneProps) {
  return <SplitViewPane kind="detail" {...props} />
}

const PANES = new Map<unknown, SplitViewColumn>([
  [SplitViewSidebar, "sidebar"],
  [SplitViewList, "list"],
  [SplitViewDetail, "detail"],
])

function SplitViewItem({
  isActive = false,
  className,
  children,
  onPress,
  ...props
}: React.ComponentProps<typeof Pressable> & {
  isActive?: boolean
  children?: React.ReactNode
}) {
  const { isCompact, setColumn } = useSplitView()
  const kind = React.useContext(SplitViewColumnContext) ?? "list"
  return (
    <Pressable
      role="button"
      accessibilityState={{ selected: isActive }}
      onPress={(event) => {
        onPress?.(event)
        setColumn(NEXT[kind])
      }}
      className={cn(
        "flex-row items-center gap-3",
        isCompact
          ? "min-h-11 border-b border-separator py-3 active:bg-item-pressed"
          : cn(
              "rounded-lg px-3 py-2",
              isActive ? "bg-surface-secondary" : "active:bg-item-pressed",
              kind === "list" && "rounded-xl py-3"
            ),
        typeof className === "string" ? className : undefined
      )}
      {...props}
    >
      <View className="min-w-0 flex-1 gap-0.5">
        {typeof children === "string" || typeof children === "number" ? (
          <Text>{children}</Text>
        ) : (
          children
        )}
      </View>
      {isCompact && kind !== "detail" ? (
        <Icon
          as={CaretRightIcon}
          mirrored={I18nManager.isRTL}
          className="size-4 text-label-tertiary"
        />
      ) : null}
    </Pressable>
  )
}

export {
  SplitView,
  type SplitViewColumn,
  SplitViewDetail,
  SplitViewItem,
  SplitViewList,
  SplitViewSidebar,
  useSplitView,
}
```

4. Update the import paths to match your project.

**NativeWind**

1. Install the dependencies:

```bash title="Terminal"
npx expo install cn phosphor-react-native react-native-reanimated react-native-svg react-native-worklets
```

2. Add the pieces it builds on: [Icon](/docs/components/icon), [Text](/docs/components/text), and the primitives `components/primitives/hooks.tsx`.

3. Copy the source into `components/patterns/split-view.tsx`:

```tsx title="nativewind/components/patterns/split-view.tsx"
import { cn } from "cn"
import { CaretLeftIcon, CaretRightIcon } from "phosphor-react-native"
import * as React from "react"
import {
  AccessibilityInfo,
  I18nManager,
  Pressable,
  type Text as RNText,
  ScrollView,
  useWindowDimensions,
  View,
  type ViewProps,
} from "react-native"
import { FadeIn, ReduceMotion } from "react-native-reanimated"
import { useBackHandler } from "@/components/primitives/hooks"
import { AnimatedView } from "@/components/ui/animated-view"
import { Icon } from "@/components/ui/icon"
import { Text, TextClassContext } from "@/components/ui/text"

type SplitViewColumn = "sidebar" | "list" | "detail"

type SplitViewContextProps = {
  isCompact: boolean
  column: SplitViewColumn
  setColumn: (column: SplitViewColumn) => void
  titles: Partial<Record<SplitViewColumn, React.ReactNode>>
  kinds: SplitViewColumn[]
}

const SplitViewContext = React.createContext<SplitViewContextProps | null>(null)

const SplitViewColumnContext = React.createContext<SplitViewColumn | null>(null)

function useSplitView() {
  const context = React.useContext(SplitViewContext)
  if (!context) {
    throw new Error("useSplitView must be used within a <SplitView />")
  }
  return context
}

const NEXT: Record<SplitViewColumn, SplitViewColumn> = {
  sidebar: "list",
  list: "detail",
  detail: "detail",
}

const PREVIOUS: Record<SplitViewColumn, SplitViewColumn | null> = {
  sidebar: null,
  list: "sidebar",
  detail: "list",
}

const RATIO: Record<SplitViewColumn, number> = {
  sidebar: 20,
  list: 32,
  detail: 48,
}

const TITLE_CLASS: Record<SplitViewColumn, string> = {
  sidebar: "px-3 pt-3 pb-2 text-xs font-semibold text-label-secondary",
  list: "",
  detail: "pb-1 text-2xl font-semibold",
}

const PANE_CLASS: Record<SplitViewColumn, string> = {
  sidebar: "p-3 pt-1",
  list: "p-3",
  detail: "p-8",
}

type SplitViewPaneProps = ViewProps & {
  title?: React.ReactNode
}

function SplitView({
  column: columnProp,
  defaultColumn = "list",
  onColumnChange,
  breakpoint = 768,
  className,
  children,
  ...props
}: ViewProps & {
  column?: SplitViewColumn
  defaultColumn?: SplitViewColumn
  onColumnChange?: (column: SplitViewColumn) => void
  breakpoint?: number
}) {
  const { width } = useWindowDimensions()
  const isCompact = width < breakpoint
  const [uncontrolledColumn, setUncontrolledColumn] =
    React.useState(defaultColumn)
  const column = columnProp ?? uncontrolledColumn

  const panes = React.Children.toArray(children).filter(React.isValidElement)
  const titles: SplitViewContextProps["titles"] = {}
  const kinds: SplitViewColumn[] = []
  for (const pane of panes) {
    const kind = PANES.get(pane.type)
    if (!kind) continue
    kinds.push(kind)
    titles[kind] = (pane.props as { title?: React.ReactNode }).title
  }

  const setColumn = React.useCallback(
    (next: SplitViewColumn) => {
      if (columnProp === undefined) setUncontrolledColumn(next)
      onColumnChange?.(next)
    },
    [columnProp, onColumnChange]
  )

  const previous = PREVIOUS[column]
  const backColumn =
    previous && kinds.includes(previous) && titles[previous] !== undefined
      ? previous
      : null

  useBackHandler(isCompact && backColumn !== null, () => {
    if (backColumn) setColumn(backColumn)
  })

  const contextValue = { isCompact, column, setColumn, titles, kinds }

  return (
    <SplitViewContext.Provider value={contextValue}>
      <View
        className={cn(
          "flex-1",
          !isCompact &&
            "flex-row overflow-hidden rounded-2xl border border-separator",
          className
        )}
        {...props}
      >
        {children}
      </View>
    </SplitViewContext.Provider>
  )
}

function SplitViewPane({
  kind,
  title,
  className,
  children,
  ...props
}: SplitViewPaneProps & {
  kind: SplitViewColumn
}) {
  const { isCompact, column, setColumn, titles, kinds } = useSplitView()
  const headingRef = React.useRef<RNText>(null)
  const mountedRef = React.useRef(false)
  const visible = !isCompact || column === kind
  const previous = PREVIOUS[kind]
  const backColumn =
    previous && kinds.includes(previous) && titles[previous] !== undefined
      ? previous
      : null
  const total = kinds.reduce((sum, item) => sum + RATIO[item], 0) || 1

  React.useEffect(() => {
    if (!isCompact || !visible) return
    if (!mountedRef.current) {
      mountedRef.current = true
      return
    }
    const node = headingRef.current
    if (!node) return
    const timeout = setTimeout(() => {
      AccessibilityInfo.sendAccessibilityEvent(node, "focus")
    }, 50)
    return () => clearTimeout(timeout)
  }, [isCompact, visible])

  if (!visible) return null

  const content = (
    <SplitViewColumnContext.Provider value={kind}>
      {isCompact && backColumn ? (
        <Pressable
          role="button"
          onPress={() => setColumn(backColumn)}
          hitSlop={8}
          className="-ms-1.5 min-h-11 flex-row items-center gap-0.5 self-start pe-1.5 active:opacity-60"
        >
          <Icon
            as={CaretLeftIcon}
            weight="bold"
            mirrored={I18nManager.isRTL}
            className="size-[1.125rem] text-link"
          />
          <TextClassContext.Provider value="text-base text-link">
            {typeof titles[backColumn] === "string" ? (
              <Text>{titles[backColumn]}</Text>
            ) : (
              titles[backColumn]
            )}
          </TextClassContext.Provider>
        </Pressable>
      ) : null}
      {title !== undefined && (isCompact || kind !== "list") ? (
        <Text
          ref={headingRef as unknown as React.Ref<typeof RNText>}
          role="heading"
          className={isCompact ? "pb-2 text-3xl font-bold" : TITLE_CLASS[kind]}
        >
          {title}
        </Text>
      ) : null}
      {children}
    </SplitViewColumnContext.Provider>
  )

  if (isCompact) {
    return (
      <AnimatedView
        key={kind}
        entering={FadeIn.duration(200).reduceMotion(ReduceMotion.System)}
        className="flex-1"
        accessibilityLabel={typeof title === "string" ? title : undefined}
        {...props}
      >
        <ScrollView className="flex-1" contentContainerClassName={className}>
          {content}
        </ScrollView>
      </AnimatedView>
    )
  }

  return (
    <View
      className={cn(
        "min-h-0",
        kinds[0] !== kind && "border-s border-separator"
      )}
      style={{ flex: RATIO[kind] / total }}
      accessibilityLabel={typeof title === "string" ? title : undefined}
      {...props}
    >
      <ScrollView
        className="flex-1"
        contentContainerClassName={cn(PANE_CLASS[kind], className)}
      >
        {content}
      </ScrollView>
    </View>
  )
}

function SplitViewSidebar(props: SplitViewPaneProps) {
  return <SplitViewPane kind="sidebar" {...props} />
}

function SplitViewList(props: SplitViewPaneProps) {
  return <SplitViewPane kind="list" {...props} />
}

function SplitViewDetail(props: SplitViewPaneProps) {
  return <SplitViewPane kind="detail" {...props} />
}

const PANES = new Map<unknown, SplitViewColumn>([
  [SplitViewSidebar, "sidebar"],
  [SplitViewList, "list"],
  [SplitViewDetail, "detail"],
])

function SplitViewItem({
  isActive = false,
  className,
  children,
  onPress,
  ...props
}: React.ComponentProps<typeof Pressable> & {
  isActive?: boolean
  children?: React.ReactNode
}) {
  const { isCompact, setColumn } = useSplitView()
  const kind = React.useContext(SplitViewColumnContext) ?? "list"
  return (
    <Pressable
      role="button"
      accessibilityState={{ selected: isActive }}
      onPress={(event) => {
        onPress?.(event)
        setColumn(NEXT[kind])
      }}
      className={cn(
        "flex-row items-center gap-3",
        isCompact
          ? "min-h-11 border-b border-separator py-3 active:bg-item-pressed"
          : cn(
              "rounded-lg px-3 py-2",
              isActive ? "bg-surface-secondary" : "active:bg-item-pressed",
              kind === "list" && "rounded-xl py-3"
            ),
        typeof className === "string" ? className : undefined
      )}
      {...props}
    >
      <View className="min-w-0 flex-1 gap-0.5">
        {typeof children === "string" || typeof children === "number" ? (
          <Text>{children}</Text>
        ) : (
          children
        )}
      </View>
      {isCompact && kind !== "detail" ? (
        <Icon
          as={CaretRightIcon}
          mirrored={I18nManager.isRTL}
          className="size-4 text-label-tertiary"
        />
      ) : null}
    </Pressable>
  )
}

export {
  SplitView,
  type SplitViewColumn,
  SplitViewDetail,
  SplitViewItem,
  SplitViewList,
  SplitViewSidebar,
  useSplitView,
}
```

4. Update the import paths to match your project.

**StyleSheet**

1. Install the dependencies:

```bash title="Terminal"
npx expo install phosphor-react-native react-native-reanimated react-native-svg react-native-worklets
```

2. Add the pieces it builds on: [Icon](/docs/components/icon), [Text](/docs/components/text), and the primitives `components/primitives/hooks.tsx`.

3. Copy the source into `components/patterns/split-view.tsx`:

```tsx title="stylesheet/components/patterns/split-view.tsx"
import { CaretLeftIcon, CaretRightIcon } from "phosphor-react-native"
import * as React from "react"
import {
  AccessibilityInfo,
  I18nManager,
  Pressable,
  type Text as RNText,
  ScrollView,
  StyleSheet,
  type TextStyle,
  useWindowDimensions,
  View,
  type ViewProps,
  type ViewStyle,
} from "react-native"
import { FadeIn, ReduceMotion } from "react-native-reanimated"
import { useBackHandler } from "@/components/primitives/hooks"
import { AnimatedView } from "@/components/ui/animated-view"
import { Icon } from "@/components/ui/icon"
import { Text, TextStyleContext } from "@/components/ui/text"
import {
  fontSize,
  radius,
  type ThemeColors,
  useTheme,
} from "@/components/ui/theme"

type SplitViewColumn = "sidebar" | "list" | "detail"

type SplitViewContextProps = {
  isCompact: boolean
  column: SplitViewColumn
  setColumn: (column: SplitViewColumn) => void
  titles: Partial<Record<SplitViewColumn, React.ReactNode>>
  kinds: SplitViewColumn[]
}

const SplitViewContext = React.createContext<SplitViewContextProps | null>(null)

const SplitViewColumnContext = React.createContext<SplitViewColumn | null>(null)

function useSplitView() {
  const context = React.useContext(SplitViewContext)
  if (!context) {
    throw new Error("useSplitView must be used within a <SplitView />")
  }
  return context
}

const NEXT: Record<SplitViewColumn, SplitViewColumn> = {
  sidebar: "list",
  list: "detail",
  detail: "detail",
}

const PREVIOUS: Record<SplitViewColumn, SplitViewColumn | null> = {
  sidebar: null,
  list: "sidebar",
  detail: "list",
}

const RATIO: Record<SplitViewColumn, number> = {
  sidebar: 20,
  list: 32,
  detail: 48,
}

const styles = StyleSheet.create({
  root: { flex: 1 },
  rootWide: {
    flexDirection: "row",
    overflow: "hidden",
    borderRadius: radius["2xl"],
    borderWidth: 1,
  },
  back: {
    marginStart: -6,
    minHeight: 44,
    flexDirection: "row",
    alignItems: "center",
    gap: 2,
    alignSelf: "flex-start",
    paddingEnd: 6,
  },
  pressed: { opacity: 0.6 },
  compactTitle: { paddingBottom: 8, ...fontSize["3xl"], fontWeight: "700" },
  sidebarTitle: {
    paddingHorizontal: 12,
    paddingTop: 12,
    paddingBottom: 8,
    ...fontSize.xs,
    fontWeight: "600",
  },
  detailTitle: { paddingBottom: 4, ...fontSize["2xl"], fontWeight: "600" },
  fill: { flex: 1 },
  pane: { minHeight: 0 },
  paneDivider: { borderStartWidth: 1 },
  sidebarPane: { padding: 12, paddingTop: 4 },
  listPane: { padding: 12 },
  detailPane: { padding: 32 },
  item: { flexDirection: "row", alignItems: "center", gap: 12 },
  itemCompact: { minHeight: 44, borderBottomWidth: 1, paddingVertical: 12 },
  itemWide: {
    borderRadius: radius.lg,
    paddingHorizontal: 12,
    paddingVertical: 8,
  },
  itemWideList: { borderRadius: radius.xl, paddingVertical: 12 },
  itemBody: { minWidth: 0, flex: 1, gap: 2 },
})

const PANE_STYLE: Record<SplitViewColumn, ViewStyle> = {
  sidebar: styles.sidebarPane,
  list: styles.listPane,
  detail: styles.detailPane,
}

function titleStyle(
  kind: SplitViewColumn,
  isCompact: boolean,
  colors: ThemeColors
): TextStyle {
  if (isCompact) return styles.compactTitle
  if (kind === "sidebar") {
    return { ...styles.sidebarTitle, color: colors.labelSecondary }
  }
  return styles.detailTitle
}

type SplitViewPaneProps = ViewProps & {
  title?: React.ReactNode
}

function SplitView({
  column: columnProp,
  defaultColumn = "list",
  onColumnChange,
  breakpoint = 768,
  style,
  children,
  ...props
}: ViewProps & {
  column?: SplitViewColumn
  defaultColumn?: SplitViewColumn
  onColumnChange?: (column: SplitViewColumn) => void
  breakpoint?: number
}) {
  const { colors } = useTheme()
  const { width } = useWindowDimensions()
  const isCompact = width < breakpoint
  const [uncontrolledColumn, setUncontrolledColumn] =
    React.useState(defaultColumn)
  const column = columnProp ?? uncontrolledColumn

  const panes = React.Children.toArray(children).filter(React.isValidElement)
  const titles: SplitViewContextProps["titles"] = {}
  const kinds: SplitViewColumn[] = []
  for (const pane of panes) {
    const kind = PANES.get(pane.type)
    if (!kind) continue
    kinds.push(kind)
    titles[kind] = (pane.props as { title?: React.ReactNode }).title
  }

  const setColumn = React.useCallback(
    (next: SplitViewColumn) => {
      if (columnProp === undefined) setUncontrolledColumn(next)
      onColumnChange?.(next)
    },
    [columnProp, onColumnChange]
  )

  const previous = PREVIOUS[column]
  const backColumn =
    previous && kinds.includes(previous) && titles[previous] !== undefined
      ? previous
      : null

  useBackHandler(isCompact && backColumn !== null, () => {
    if (backColumn) setColumn(backColumn)
  })

  const contextValue = { isCompact, column, setColumn, titles, kinds }

  return (
    <SplitViewContext.Provider value={contextValue}>
      <View
        style={[
          styles.root,
          !isCompact && [styles.rootWide, { borderColor: colors.separator }],
          style,
        ]}
        {...props}
      >
        {children}
      </View>
    </SplitViewContext.Provider>
  )
}

function SplitViewPane({
  kind,
  title,
  style,
  children,
  ...props
}: SplitViewPaneProps & {
  kind: SplitViewColumn
}) {
  const { colors } = useTheme()
  const { isCompact, column, setColumn, titles, kinds } = useSplitView()
  const headingRef = React.useRef<RNText>(null)
  const mountedRef = React.useRef(false)
  const visible = !isCompact || column === kind
  const previous = PREVIOUS[kind]
  const backColumn =
    previous && kinds.includes(previous) && titles[previous] !== undefined
      ? previous
      : null
  const total = kinds.reduce((sum, item) => sum + RATIO[item], 0) || 1

  React.useEffect(() => {
    if (!isCompact || !visible) return
    if (!mountedRef.current) {
      mountedRef.current = true
      return
    }
    const node = headingRef.current
    if (!node) return
    const timeout = setTimeout(() => {
      AccessibilityInfo.sendAccessibilityEvent(node, "focus")
    }, 50)
    return () => clearTimeout(timeout)
  }, [isCompact, visible])

  if (!visible) return null

  const content = (
    <SplitViewColumnContext.Provider value={kind}>
      {isCompact && backColumn ? (
        <Pressable
          role="button"
          onPress={() => setColumn(backColumn)}
          hitSlop={8}
          style={({ pressed }) => [styles.back, pressed && styles.pressed]}
        >
          <Icon
            as={CaretLeftIcon}
            weight="bold"
            mirrored={I18nManager.isRTL}
            size={18}
            color={colors.link}
          />
          <TextStyleContext.Provider
            value={{ ...fontSize.base, color: colors.link }}
          >
            {typeof titles[backColumn] === "string" ? (
              <Text>{titles[backColumn]}</Text>
            ) : (
              titles[backColumn]
            )}
          </TextStyleContext.Provider>
        </Pressable>
      ) : null}
      {title !== undefined && (isCompact || kind !== "list") ? (
        <Text
          ref={headingRef as unknown as React.Ref<typeof RNText>}
          role="heading"
          style={titleStyle(kind, isCompact, colors)}
        >
          {title}
        </Text>
      ) : null}
      {children}
    </SplitViewColumnContext.Provider>
  )

  if (isCompact) {
    return (
      <AnimatedView
        key={kind}
        entering={FadeIn.duration(200).reduceMotion(ReduceMotion.System)}
        style={styles.fill}
        accessibilityLabel={typeof title === "string" ? title : undefined}
        {...props}
      >
        <ScrollView style={styles.fill} contentContainerStyle={style}>
          {content}
        </ScrollView>
      </AnimatedView>
    )
  }

  return (
    <View
      style={[
        styles.pane,
        kinds[0] !== kind && [
          styles.paneDivider,
          { borderColor: colors.separator },
        ],
        { flex: RATIO[kind] / total },
      ]}
      accessibilityLabel={typeof title === "string" ? title : undefined}
      {...props}
    >
      <ScrollView
        style={styles.fill}
        contentContainerStyle={[PANE_STYLE[kind], style]}
      >
        {content}
      </ScrollView>
    </View>
  )
}

function SplitViewSidebar(props: SplitViewPaneProps) {
  return <SplitViewPane kind="sidebar" {...props} />
}

function SplitViewList(props: SplitViewPaneProps) {
  return <SplitViewPane kind="list" {...props} />
}

function SplitViewDetail(props: SplitViewPaneProps) {
  return <SplitViewPane kind="detail" {...props} />
}

const PANES = new Map<unknown, SplitViewColumn>([
  [SplitViewSidebar, "sidebar"],
  [SplitViewList, "list"],
  [SplitViewDetail, "detail"],
])

function SplitViewItem({
  isActive = false,
  style,
  children,
  onPress,
  ...props
}: Omit<React.ComponentProps<typeof Pressable>, "style"> & {
  isActive?: boolean
  children?: React.ReactNode
  style?: ViewStyle
}) {
  const { colors } = useTheme()
  const { isCompact, setColumn } = useSplitView()
  const kind = React.useContext(SplitViewColumnContext) ?? "list"
  return (
    <Pressable
      role="button"
      accessibilityState={{ selected: isActive }}
      onPress={(event) => {
        onPress?.(event)
        setColumn(NEXT[kind])
      }}
      style={({ pressed }) => [
        styles.item,
        isCompact
          ? [styles.itemCompact, { borderColor: colors.separator }]
          : [styles.itemWide, kind === "list" && styles.itemWideList],
        !isCompact && isActive && { backgroundColor: colors.surfaceSecondary },
        pressed &&
          (isCompact || !isActive) && { backgroundColor: colors.itemPressed },
        style,
      ]}
      {...props}
    >
      <View style={styles.itemBody}>
        {typeof children === "string" || typeof children === "number" ? (
          <Text>{children}</Text>
        ) : (
          children
        )}
      </View>
      {isCompact && kind !== "detail" ? (
        <Icon
          as={CaretRightIcon}
          mirrored={I18nManager.isRTL}
          size={16}
          color={colors.labelTertiary}
        />
      ) : null}
    </Pressable>
  )
}

export {
  SplitView,
  type SplitViewColumn,
  SplitViewDetail,
  SplitViewItem,
  SplitViewList,
  SplitViewSidebar,
  useSplitView,
}
```

4. Update the import paths to match your project.

**SwiftUI**

1. Target iOS 17 or later.

2. Add the Swift package to your app:

```swift title="Package.swift"
.package(url: "https://github.com/phosphor-icons/swift", from: "2.1.0")
```

3. Copy the theme files every view uses:

```swift title="swift/Theme/Theme.swift"
import SwiftUI
import UIKit

struct RGBA: Sendable {
  let red: CGFloat
  let green: CGFloat
  let blue: CGFloat
  let alpha: CGFloat

  init(_ hex: UInt32, _ alpha: CGFloat = 1) {
    red = CGFloat((hex >> 16) & 0xFF) / 255
    green = CGFloat((hex >> 8) & 0xFF) / 255
    blue = CGFloat(hex & 0xFF) / 255
    self.alpha = alpha
  }

  var uiColor: UIColor {
    UIColor(red: red, green: green, blue: blue, alpha: alpha)
  }
}

extension Color {
  static func adaptive(light: RGBA, dark: RGBA) -> Color {
    let lightColor = light.uiColor
    let darkColor = dark.uiColor
    return Color(uiColor: UIColor { traits in
      traits.userInterfaceStyle == .dark ? darkColor : lightColor
    })
  }
}

public struct TextStyle: Sendable, Hashable {
  public let size: CGFloat
  public let lineHeight: CGFloat
  public let letterSpacing: CGFloat

  public init(size: CGFloat, lineHeight: CGFloat, letterSpacing: CGFloat) {
    self.size = size
    self.lineHeight = lineHeight
    self.letterSpacing = letterSpacing
  }

  public func font(weight: Font.Weight = .regular) -> Font {
    .system(size: size, weight: weight)
  }

  public var lineSpacing: CGFloat {
    max(0, lineHeight - UIFont.systemFont(ofSize: size).lineHeight)
  }
}

extension Hashable where Self == Font {
  public static func textStyle(_ style: TextStyle, weight: Font.Weight = .regular) -> Font {
    style.font(weight: weight)
  }
}

private struct TextStyleModifier: ViewModifier {
  let style: TextStyle
  let weight: Font.Weight

  func body(content: Content) -> some View {
    content
      .font(style.font(weight: weight))
      .tracking(style.letterSpacing)
      .lineSpacing(style.lineSpacing)
      .padding(.vertical, style.lineSpacing / 2)
  }
}

extension View {
  public func textStyle(_ style: TextStyle, weight: Font.Weight = .regular) -> some View {
    modifier(TextStyleModifier(style: style, weight: weight))
  }
}

public struct Shadow: Sendable, Hashable {
  public let color: Color
  public let radius: CGFloat
  public let x: CGFloat
  public let y: CGFloat

  public init(color: Color, radius: CGFloat, x: CGFloat = 0, y: CGFloat = 0) {
    self.color = color
    self.radius = radius
    self.x = x
    self.y = y
  }
}

extension View {
  public func shadow(_ shadow: Shadow) -> some View {
    self.shadow(color: shadow.color, radius: shadow.radius, x: shadow.x, y: shadow.y)
  }
}
```

```swift title="swift/Theme/Tokens.swift"
import SwiftUI

extension Color {
  public static let surface = Color.adaptive(light: .init(0xFFFFFF), dark: .init(0x000000))
  public static let surfaceSecondary = Color.adaptive(light: .init(0xF5F5F7), dark: .init(0x161617))
  public static let surfaceTertiary = Color.adaptive(light: .init(0xE8E8ED), dark: .init(0x2C2C2E))
  public static let surfaceRaised = Color.adaptive(light: .init(0xFFFFFF), dark: .init(0x1D1D1F))
  public static let label = Color.adaptive(light: .init(0x1D1D1F), dark: .init(0xF5F5F7))
  public static let labelSecondary = Color.adaptive(light: .init(0x6E6E73), dark: .init(0xA1A1A6))
  public static let labelTertiary = Color.adaptive(light: .init(0x86868B), dark: .init(0x86868B))
  public static let labelQuaternary = Color.adaptive(light: .init(0xD2D2D7), dark: .init(0x424245))
  public static let control = Color.adaptive(light: .init(0x000000, 0.04), dark: .init(0xFFFFFF, 0.1))
  public static let controlPressed = Color.adaptive(light: .init(0x000000, 0.12), dark: .init(0xFFFFFF, 0.22))
  public static let controlSelected = Color.adaptive(light: .init(0x1D1D1F), dark: .init(0xF5F5F7))
  public static let controlDisabled = Color.adaptive(light: .init(0x000000, 0.03), dark: .init(0xFFFFFF, 0.05))
  public static let onControlSelected = Color.adaptive(light: .init(0xFFFFFF), dark: .init(0x000000))
  public static let itemPressed = Color.adaptive(light: .init(0x000000, 0.08), dark: .init(0xFFFFFF, 0.12))
  public static let itemSelected = Color.adaptive(light: .init(0x000000, 0.06), dark: .init(0xFFFFFF, 0.1))
  public static let separator = Color.adaptive(light: .init(0xD2D2D7), dark: .init(0x424245))
  public static let separatorStrong = Color.adaptive(light: .init(0x86868B), dark: .init(0x6E6E73))
  public static let accent = Color.adaptive(light: .init(0x0071E3), dark: .init(0x0071E3))
  public static let accentPressed = Color.adaptive(light: .init(0x005BB8), dark: .init(0x004D9E))
  public static let accentSelected = Color.adaptive(light: .init(0x0071E3), dark: .init(0x0071E3))
  public static let accentDisabled = Color.adaptive(light: .init(0x0071E3, 0.4), dark: .init(0x0071E3, 0.4))
  public static let onAccent = Color.adaptive(light: .init(0xFFFFFF), dark: .init(0xFFFFFF))
  public static let accentSurface = Color.adaptive(light: .init(0x0071E3, 0.09), dark: .init(0x0071E3, 0.18))
  public static let accentSurfacePressed = Color.adaptive(light: .init(0x0071E3, 0.18), dark: .init(0x0071E3, 0.3))
  public static let link = Color.adaptive(light: .init(0x0066CC), dark: .init(0x2997FF))
  public static let focus = Color.adaptive(light: .init(0x0071E3), dark: .init(0x0071E3))
  public static let scrim = Color.adaptive(light: .init(0x000000, 0.48), dark: .init(0x000000, 0.48))
  public static let media = Color.adaptive(light: .init(0x000000), dark: .init(0x000000))
  public static let onMedia = Color.adaptive(light: .init(0xFFFFFF), dark: .init(0xFFFFFF))
  public static let danger = Color.adaptive(light: .init(0xD0000A), dark: .init(0xFF5447))
  public static let dangerSurface = Color.adaptive(light: .init(0xD70015, 0.08), dark: .init(0xFF453A, 0.2))
  public static let dangerSurfacePressed = Color.adaptive(light: .init(0xD70015, 0.16), dark: .init(0xFF453A, 0.36))
  public static let success = Color.adaptive(light: .init(0x008009), dark: .init(0x30D158))
  public static let successSurface = Color.adaptive(light: .init(0xEFFAF1), dark: .init(0x30D158, 0.16))
  public static let warning = Color.adaptive(light: .init(0xB64400), dark: .init(0xFF9F0A))
  public static let warningSurface = Color.adaptive(light: .init(0xFFF5EA), dark: .init(0xFF9F0A, 0.16))
}

public enum Radius {
  public static let xs: CGFloat = 3
  public static let sm: CGFloat = 5
  public static let md: CGFloat = 8
  public static let lg: CGFloat = 10
  public static let xl: CGFloat = 12
  public static let xl2: CGFloat = 18
  public static let xl3: CGFloat = 28
  public static let full: CGFloat = 9999
}

extension TextStyle {
  public static let xs3 = TextStyle(size: 11, lineHeight: 13, letterSpacing: 0.066)
  public static let xs2 = TextStyle(size: 12, lineHeight: 16, letterSpacing: 0)
  public static let xs = TextStyle(size: 13, lineHeight: 18, letterSpacing: -0.078)
  public static let sm = TextStyle(size: 15, lineHeight: 20, letterSpacing: -0.24)
  public static let md = TextStyle(size: 16, lineHeight: 21, letterSpacing: -0.32)
  public static let base = TextStyle(size: 17, lineHeight: 22, letterSpacing: -0.442)
  public static let lg = TextStyle(size: 20, lineHeight: 25, letterSpacing: -0.46)
  public static let xl = TextStyle(size: 22, lineHeight: 28, letterSpacing: -0.264)
  public static let xl2 = TextStyle(size: 28, lineHeight: 34, letterSpacing: 0.392)
  public static let xl3 = TextStyle(size: 34, lineHeight: 41, letterSpacing: 0.408)

  public static let allCases: [TextStyle] = [.xs3, .xs2, .xs, .sm, .md, .base, .lg, .xl, .xl2, .xl3]
}

extension Shadow {
  public static let md = Shadow(color: .black.opacity(0.08), radius: 6, x: 2, y: 4)
  public static let lg = Shadow(color: .black.opacity(0.12), radius: 12, y: 4)
}
```

4. Copy the source and every file it uses:

```swift title="swift/Patterns/SplitView.swift"
import PhosphorSwift
import SwiftUI

public enum SplitViewColumn: CaseIterable, Sendable {
  case sidebar, list, detail

  var next: SplitViewColumn {
    switch self {
    case .sidebar: .list
    case .list, .detail: .detail
    }
  }

  var previous: SplitViewColumn? {
    switch self {
    case .sidebar: nil
    case .list: .sidebar
    case .detail: .list
    }
  }

  var order: Int {
    switch self {
    case .sidebar: 0
    case .list: 1
    case .detail: 2
    }
  }

  var weight: CGFloat {
    switch self {
    case .sidebar: 20
    case .list: 32
    case .detail: 48
    }
  }
}

enum SplitViewMath {
  static let wideWidth: CGFloat = 768

  static func isWide(_ width: CGFloat) -> Bool {
    width >= wideWidth
  }

  static func backColumn(for kind: SplitViewColumn, present: [SplitViewColumn]) -> SplitViewColumn? {
    guard let previous = kind.previous else { return nil }
    return present.contains(previous) ? previous : nil
  }

  static func widths(total: CGFloat, present: [SplitViewColumn]) -> [SplitViewColumn: CGFloat] {
    let available = max(0, total - CGFloat(max(present.count - 1, 0)))
    let sum = present.reduce(0) { $0 + $1.weight }
    guard sum > 0 else { return [:] }
    var result: [SplitViewColumn: CGFloat] = [:]
    for column in present {
      result[column] = (available * column.weight / sum).rounded(.down)
    }
    return result
  }
}

struct SplitViewColumnKey: LayoutValueKey {
  static let defaultValue: SplitViewColumn? = nil
}

struct SplitViewColumnsLayout: Layout {
  func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
    let width = proposal.width ?? SplitViewMath.wideWidth
    if let height = proposal.height { return CGSize(width: width, height: height) }
    let widths = columnWidths(total: width, subviews: subviews)
    let height = zip(subviews, widths).map { $0.sizeThatFits(ProposedViewSize(width: $1, height: nil)).height }.max() ?? 0
    return CGSize(width: width, height: height)
  }

  func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) {
    let widths = columnWidths(total: bounds.width, subviews: subviews)
    var x = bounds.minX
    for (subview, width) in zip(subviews, widths) {
      subview.place(
        at: CGPoint(x: x, y: bounds.minY),
        anchor: .topLeading,
        proposal: ProposedViewSize(width: width, height: bounds.height)
      )
      x += width + 1
    }
  }

  private func columnWidths(total: CGFloat, subviews: Subviews) -> [CGFloat] {
    let kinds = subviews.map { $0[SplitViewColumnKey.self] ?? .detail }
    let widths = SplitViewMath.widths(total: total, present: kinds)
    var result = kinds.map { widths[$0] ?? 0 }
    if !result.isEmpty {
      let used = result.dropLast().reduce(0, +) + CGFloat(result.count - 1)
      result[result.count - 1] = max(0, total - used)
    }
    return result
  }
}

struct SplitViewPaneInfo: Equatable {
  let kind: SplitViewColumn
  let title: Text?
}

struct SplitViewPanesKey: PreferenceKey {
  static var defaultValue: [SplitViewPaneInfo] { [] }

  static func reduce(value: inout [SplitViewPaneInfo], nextValue: () -> [SplitViewPaneInfo]) {
    value.append(contentsOf: nextValue())
  }
}

struct SplitViewContext: @unchecked Sendable {
  var wide = false
  var column: SplitViewColumn = .list
  var panes: [SplitViewPaneInfo] = []
  var forward = true
  var select: @MainActor @Sendable (SplitViewColumn) -> Void = { _ in }

  func title(_ kind: SplitViewColumn) -> Text? {
    panes.first { $0.kind == kind }?.title
  }
}

extension EnvironmentValues {
  @Entry var splitView: SplitViewContext? = nil
  @Entry var splitViewColumn: SplitViewColumn = .list
}

public struct SplitView<Content: View>: View {
  let external: Binding<SplitViewColumn>?
  let content: Content

  @State private var local: SplitViewColumn
  @State private var width: CGFloat = 0
  @State private var panes: [SplitViewPaneInfo] = []
  @State private var forward = true
  @Environment(\.accessibilityReduceMotion) private var reduceMotion

  public init(column: Binding<SplitViewColumn>, @ViewBuilder content: () -> Content) {
    self.external = column
    self._local = State(initialValue: column.wrappedValue)
    self.content = content()
  }

  public init(defaultColumn: SplitViewColumn = .list, @ViewBuilder content: () -> Content) {
    self.external = nil
    self._local = State(initialValue: defaultColumn)
    self.content = content()
  }

  public var body: some View {
    let binding = external ?? $local
    let current = binding.wrappedValue
    let wide = SplitViewMath.isWide(width)
    let animation: Animation? = reduceMotion ? nil : .timingCurve(0.32, 0.72, 0, 1, duration: 0.35)
    let context = SplitViewContext(
      wide: wide,
      column: current,
      panes: panes,
      forward: forward,
      select: { next in
        guard next != binding.wrappedValue else { return }
        forward = next.order > binding.wrappedValue.order
        if wide {
          binding.wrappedValue = next
        } else {
          withAnimation(animation) { binding.wrappedValue = next }
        }
      }
    )
    Group {
      if wide {
        SplitViewColumnsLayout { content }
      } else {
        ZStack(alignment: .topLeading) { content }
      }
    }
    .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .topLeading)
    .clipped()
    .environment(\.splitView, context)
    .onGeometryChange(for: CGFloat.self) { $0.size.width } action: { width = $0 }
    .onPreferenceChange(SplitViewPanesKey.self) { value in panes = value }
  }
}

struct SplitViewPane<Content: View>: View {
  let kind: SplitViewColumn
  let title: Text?
  let content: Content

  @Environment(\.splitView) private var splitView
  @Environment(\.layoutDirection) private var layoutDirection

  var body: some View {
    let context = splitView ?? SplitViewContext()
    Group {
      if context.wide {
        pane(context)
          .frame(maxHeight: .infinity, alignment: .top)
          .overlay(alignment: .leading) {
            if context.panes.first?.kind != kind {
              Color.separator.frame(width: 1).offset(x: -1)
            }
          }
          .layoutValue(key: SplitViewColumnKey.self, value: kind)
      } else if context.column == kind {
        pane(context)
          .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .top)
          .transition(
            .asymmetric(
              insertion: .move(edge: context.forward ? .trailing : .leading),
              removal: .move(edge: context.forward ? .leading : .trailing)
            )
          )
      } else {
        Color.clear
          .frame(width: 0, height: 0)
          .accessibilityHidden(true)
      }
    }
    .preference(key: SplitViewPanesKey.self, value: [SplitViewPaneInfo(kind: kind, title: title)])
  }

  private func pane(_ context: SplitViewContext) -> some View {
    let back = context.wide ? nil : SplitViewMath.backColumn(for: kind, present: context.panes.map(\.kind))
    return ScrollView {
      VStack(alignment: .leading, spacing: 0) {
        if let back {
          Button {
            context.select(back)
          } label: {
            HStack(spacing: 2) {
              Ph.caretLeft.bold
                .frame(width: 18, height: 18)
                .flipsForRightToLeftLayoutDirection(true)
              if let title = context.title(back) {
                title.lineLimit(1)
              } else {
                Text("Back")
              }
            }
            .scaledFont(.base)
            .foregroundStyle(Color.link)
            .frame(minHeight: 44)
            .contentShape(Rectangle())
          }
          .buttonStyle(SplitViewBackStyle())
          .padding(.leading, -6)
        }
        if let title {
          heading(title, wide: context.wide)
        }
        VStack(alignment: .leading, spacing: 0) {
          content
        }
        .padding(.top, context.wide ? 0 : -1)
        .clipped()
        .environment(\.splitViewColumn, kind)
      }
      .padding(padding(wide: context.wide))
      .frame(maxWidth: .infinity, alignment: .leading)
    }
  }

  @ViewBuilder
  private func heading(_ title: Text, wide: Bool) -> some View {
    if !wide {
      title
        .scaledFont(.xl3, weight: .bold)
        .foregroundStyle(Color.label)
        .padding(.bottom, 8)
        .accessibilityAddTraits(.isHeader)
    } else {
      switch kind {
      case .sidebar:
        title
          .scaledFont(.xs, weight: .semibold)
          .foregroundStyle(Color.labelSecondary)
          .padding(.horizontal, 12)
          .padding(.top, 12)
          .padding(.bottom, 8)
          .accessibilityAddTraits(.isHeader)
      case .list:
        title
          .frame(width: 0, height: 0)
          .opacity(0)
          .accessibilityAddTraits(.isHeader)
      case .detail:
        title
          .scaledFont(.xl, weight: .semibold)
          .foregroundStyle(Color.label)
          .padding(.bottom, 4)
          .accessibilityAddTraits(.isHeader)
      }
    }
  }

  private func padding(wide: Bool) -> EdgeInsets {
    guard wide else { return EdgeInsets(top: 0, leading: 16, bottom: 16, trailing: 16) }
    switch kind {
    case .sidebar: return EdgeInsets(top: 4, leading: 12, bottom: 12, trailing: 12)
    case .list: return EdgeInsets(top: 12, leading: 12, bottom: 12, trailing: 12)
    case .detail: return EdgeInsets(top: 32, leading: 32, bottom: 32, trailing: 32)
    }
  }
}

private struct SplitViewBackStyle: ButtonStyle {
  func makeBody(configuration: Configuration) -> some View {
    configuration.label.opacity(configuration.isPressed ? 0.6 : 1)
  }
}

public struct SplitViewSidebar<Content: View>: View {
  let title: Text?
  let content: Content

  public init(_ title: LocalizedStringKey? = nil, @ViewBuilder content: () -> Content) {
    self.title = title.map { Text($0) }
    self.content = content()
  }

  public init(verbatim title: String, @ViewBuilder content: () -> Content) {
    self.title = Text(verbatim: title)
    self.content = content()
  }

  public var body: some View {
    SplitViewPane(kind: .sidebar, title: title, content: content)
  }
}

public struct SplitViewList<Content: View>: View {
  let title: Text?
  let content: Content

  public init(_ title: LocalizedStringKey? = nil, @ViewBuilder content: () -> Content) {
    self.title = title.map { Text($0) }
    self.content = content()
  }

  public init(verbatim title: String, @ViewBuilder content: () -> Content) {
    self.title = Text(verbatim: title)
    self.content = content()
  }

  public var body: some View {
    SplitViewPane(kind: .list, title: title, content: content)
  }
}

public struct SplitViewDetail<Content: View>: View {
  let title: Text?
  let content: Content

  public init(_ title: LocalizedStringKey? = nil, @ViewBuilder content: () -> Content) {
    self.title = title.map { Text($0) }
    self.content = content()
  }

  public init(verbatim title: String, @ViewBuilder content: () -> Content) {
    self.title = Text(verbatim: title)
    self.content = content()
  }

  public var body: some View {
    SplitViewPane(kind: .detail, title: title, content: content)
  }
}

public struct SplitViewItem<Label: View>: View {
  let isActive: Bool
  let action: (() -> Void)?
  let label: Label

  @Environment(\.splitView) private var splitView
  @Environment(\.splitViewColumn) private var kind

  public init(isActive: Bool = false, action: (() -> Void)? = nil, @ViewBuilder label: () -> Label) {
    self.isActive = isActive
    self.action = action
    self.label = label()
  }

  public var body: some View {
    let wide = splitView?.wide ?? false
    Button {
      action?()
      splitView?.select(kind.next)
    } label: {
      HStack(spacing: 12) {
        VStack(alignment: .leading, spacing: 2) {
          label
        }
        .scaledFont(.base)
        .frame(maxWidth: .infinity, alignment: .leading)
        if !wide && kind != .detail {
          Ph.caretRight.regular
            .frame(width: 16, height: 16)
            .foregroundStyle(Color.labelTertiary)
            .flipsForRightToLeftLayoutDirection(true)
            .accessibilityHidden(true)
        }
      }
    }
    .buttonStyle(SplitViewItemStyle(wide: wide, kind: kind, active: isActive))
    .accessibilityAddTraits(isActive ? .isSelected : [])
  }
}

private struct SplitViewItemStyle: ButtonStyle {
  let wide: Bool
  let kind: SplitViewColumn
  let active: Bool

  @Environment(\.isEnabled) private var isEnabled

  func makeBody(configuration: Configuration) -> some View {
    let pressed = configuration.isPressed && isEnabled
    if wide {
      let shape = RoundedRectangle(cornerRadius: kind == .list ? Radius.xl : Radius.lg, style: .continuous)
      configuration.label
        .foregroundStyle(isEnabled ? Color.label : .labelQuaternary)
        .padding(.horizontal, 12)
        .padding(.vertical, kind == .list ? 12 : 8)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(pressed ? Color.itemPressed : active ? .itemSelected : .clear, in: shape)
        .contentShape(shape)
    } else {
      configuration.label
        .foregroundStyle(isEnabled ? Color.label : .labelQuaternary)
        .padding(.vertical, 12)
        .frame(maxWidth: .infinity, minHeight: 44, alignment: .leading)
        .background(pressed ? Color.itemPressed : .clear)
        .overlay(alignment: .top) {
          Color.separator.frame(height: 1)
        }
        .contentShape(Rectangle())
    }
  }
}
```

```swift title="swift/Components/Button.swift"
import SwiftUI

public struct VariantButtonStyle: ButtonStyle {
  public enum Variant: CaseIterable, Sendable {
    case `default`, outline, secondary, tinted, ghost, plain, destructive, link
  }

  public enum Size: CaseIterable, Sendable {
    case `default`, xs, sm, lg, xl, icon, iconXs, iconSm, iconLg, iconXl

    var height: CGFloat {
      switch self {
      case .xs, .iconXs: 24
      case .sm, .iconSm: 32
      case .default, .icon: 36
      case .lg, .iconLg: 44
      case .xl, .iconXl: 56
      }
    }

    var horizontalPadding: CGFloat {
      switch self {
      case .xs: 11
      case .sm: 12
      case .default: 16
      case .lg: 22
      case .xl: 31
      case .icon, .iconXs, .iconSm, .iconLg, .iconXl: 0
      }
    }

    var spacing: CGFloat {
      switch self {
      case .xs, .sm, .iconXs, .iconSm: 4
      case .xl, .iconXl: 8
      default: 6
      }
    }

    var textStyle: TextStyle {
      switch self {
      case .xs, .iconXs: .xs2
      case .lg, .xl: .base
      default: .sm
      }
    }

    public var iconSize: CGFloat {
      switch self {
      case .xs, .iconXs: 12
      default: 16
      }
    }

    var blockRadius: CGFloat {
      switch self {
      case .xs, .iconXs: Radius.sm
      case .lg, .iconLg: Radius.lg
      case .xl, .iconXl: Radius.xl
      default: Radius.md
      }
    }

    var isIcon: Bool {
      switch self {
      case .icon, .iconXs, .iconSm, .iconLg, .iconXl: true
      default: false
      }
    }
  }

  let variant: Variant
  let size: Size
  let block: Bool
  var metrics: ButtonMetrics?

  public init(_ variant: Variant = .default, size: Size = .default, block: Bool = false) {
    self.variant = variant
    self.size = size
    self.block = block
  }

  init(_ variant: Variant, size: Size, metrics: ButtonMetrics) {
    self.variant = variant
    self.size = size
    self.block = false
    self.metrics = metrics
  }

  public func makeBody(configuration: Configuration) -> some View {
    StyledButton(configuration: configuration, variant: variant, size: size, block: block, metrics: metrics)
  }
}

struct ButtonMetrics: Sendable {
  var horizontalPadding: CGFloat
  var spacing: CGFloat
  var iconSize: CGFloat
  var textStyle: TextStyle
}

private struct StyledButton: View {
  let configuration: ButtonStyleConfiguration
  let variant: VariantButtonStyle.Variant
  let size: VariantButtonStyle.Size
  let block: Bool
  let metrics: ButtonMetrics?

  @Environment(\.colorScheme) private var colorScheme
  @Environment(\.isEnabled) private var isEnabled
  @Environment(\.buttonGroup) private var group

  var body: some View {
    let joined = group != nil && variant != .ghost && variant != .plain
    let rounded = RoundedRectangle(
      cornerRadius: block ? size.blockRadius : Radius.full,
      style: .continuous
    )
    let shape = joined ? AnyShape(Rectangle()) : AnyShape(rounded)
    configuration.label
      .labelStyle(ButtonLabelStyle(spacing: metrics?.spacing ?? size.spacing, iconSize: metrics?.iconSize ?? size.iconSize))
    .font((metrics?.textStyle ?? size.textStyle).font())
    .tracking((metrics?.textStyle ?? size.textStyle).letterSpacing)
    .underline(variant == .link && pressed && isEnabled)
    .lineLimit(1)
    .foregroundStyle(foreground)
    .padding(.horizontal, metrics?.horizontalPadding ?? size.horizontalPadding)
    .frame(width: size.isIcon && !block ? size.height : nil, height: size.height)
    .frame(maxWidth: block || group == .vertical ? .infinity : nil)
    .background(background, in: shape)
    .overlay {
      if variant == .outline && !joined {
        rounded.strokeBorder(Color.separator)
      }
    }
    .contentShape(shape)
    .anchorPreference(key: ButtonGroupFramesKey.self, value: .bounds) { anchor in
      joined ? [ButtonGroupFrame(bounds: anchor, outlined: variant == .outline)] : []
    }
  }

  private var isDark: Bool { colorScheme == .dark }
  private var pressed: Bool { configuration.isPressed }

  private var foreground: Color {
    switch variant {
    case .default:
      .onAccent
    case .outline, .secondary, .ghost:
      isEnabled ? .label : .labelQuaternary
    case .tinted, .plain:
      isEnabled ? .link : .link.opacity(0.4)
    case .destructive:
      isEnabled ? .danger : .danger.opacity(0.4)
    case .link:
      isEnabled ? .link : .labelQuaternary
    }
  }

  private var background: Color {
    switch variant {
    case .default:
      !isEnabled ? .accentDisabled : pressed ? .accentPressed : .accent
    case .outline:
      isEnabled && pressed ? .itemPressed : isDark ? .clear : .surface
    case .secondary:
      !isEnabled ? .controlDisabled : pressed ? .controlPressed : .control
    case .tinted:
      isEnabled && pressed ? .accentSurfacePressed : .accentSurface
    case .ghost:
      isEnabled && pressed ? .itemPressed : .clear
    case .plain:
      isEnabled && pressed ? .itemPressed : .clear
    case .destructive:
      isEnabled && pressed ? .dangerSurfacePressed : .dangerSurface
    case .link:
      .clear
    }
  }
}

struct ButtonLabelStyle: LabelStyle {
  let spacing: CGFloat
  let iconSize: CGFloat

  func makeBody(configuration: Configuration) -> some View {
    HStack(spacing: spacing) {
      configuration.icon
        .frame(width: iconSize, height: iconSize)
      configuration.title
    }
  }
}

extension ButtonStyle where Self == VariantButtonStyle {
  public static func variant(
    _ variant: VariantButtonStyle.Variant = .default,
    size: VariantButtonStyle.Size = .default,
    block: Bool = false
  ) -> VariantButtonStyle {
    VariantButtonStyle(variant, size: size, block: block)
  }
}
```

```swift title="swift/Components/ButtonGroup.swift"
import SwiftUI

extension EnvironmentValues {
  @Entry var buttonGroup: Axis? = nil
  @Entry var buttonGroupSize: CGSize = .zero
}

enum ButtonGroupSpace: Hashable {
  case group
}

struct ButtonGroupFrame {
  let bounds: Anchor<CGRect>
  let outlined: Bool
}

struct ButtonGroupFramesKey: PreferenceKey {
  static var defaultValue: [ButtonGroupFrame] { [] }

  static func reduce(value: inout [ButtonGroupFrame], nextValue: () -> [ButtonGroupFrame]) {
    value.append(contentsOf: nextValue())
  }
}

struct ButtonGroupNestedKey: PreferenceKey {
  static var defaultValue: Bool { false }

  static func reduce(value: inout Bool, nextValue: () -> Bool) {
    value = value || nextValue()
  }
}

public struct ButtonGroup<Content: View>: View {
  let orientation: Axis
  let content: Content

  @State private var nested = false
  @State private var size: CGSize = .zero

  public init(orientation: Axis = .horizontal, @ViewBuilder content: () -> Content) {
    self.orientation = orientation
    self.content = content()
  }

  public var body: some View {
    let shape = orientation == .horizontal
      ? AnyShape(Capsule())
      : AnyShape(RoundedRectangle(cornerRadius: Radius.xl2, style: .continuous))
    stack
      .coordinateSpace(.named(ButtonGroupSpace.group))
      .onGeometryChange(for: CGSize.self) { $0.size } action: { size = $0 }
      .environment(\.buttonGroup, nested ? nil : orientation)
      .environment(\.buttonGroupSize, size)
      .onPreferenceChange(ButtonGroupNestedKey.self) { nested = $0 }
      .modifier(ButtonGroupClip(shape: nested ? nil : shape))
      .overlayPreferenceValue(ButtonGroupFramesKey.self) { frames in
        if !nested {
          GeometryReader { proxy in
            outline(frames.map { (proxy[$0.bounds], $0.outlined) }, shape: shape)
          }
        }
      }
      .transformPreference(ButtonGroupFramesKey.self) { $0 = [] }
      .transformPreference(ButtonGroupNestedKey.self) { $0 = true }
      .fixedSize(horizontal: orientation == .vertical, vertical: orientation == .horizontal)
      .accessibilityElement(children: .contain)
  }

  @ViewBuilder private var stack: some View {
    switch orientation {
    case .horizontal:
      HStack(spacing: nested ? 8 : 0) { content }
    case .vertical:
      VStack(spacing: nested ? 8 : 0) { content }
    }
  }

  @ViewBuilder private func outline(_ frames: [(CGRect, Bool)], shape: AnyShape) -> some View {
    if frames.contains(where: \.1) {
      ZStack(alignment: .topLeading) {
        shape
          .stroke(Color.separator, lineWidth: 1)
          .padding(0.5)
          .mask {
            Path { path in
              for (rect, outlined) in frames where outlined {
                path.addRect(rect)
              }
            }
          }
        ForEach(Array(frames.dropLast().enumerated()), id: \.offset) { _, frame in
          if frame.1 {
            divider(frame.0)
          }
        }
      }
      .clipShape(shape)
      .allowsHitTesting(false)
    }
  }

  private func divider(_ rect: CGRect) -> some View {
    let horizontal = orientation == .horizontal
    return Rectangle()
      .fill(Color.separator)
      .frame(width: horizontal ? 1 : rect.width, height: horizontal ? rect.height : 1)
      .position(
        x: horizontal ? rect.maxX - 0.5 : rect.midX,
        y: horizontal ? rect.midY : rect.maxY - 0.5
      )
  }
}

struct ButtonGroupItem<Content: View>: View {
  let radius: CGFloat
  let content: (UnevenRoundedRectangle) -> Content

  @State private var frame: CGRect = .zero
  @Environment(\.buttonGroup) private var group
  @Environment(\.buttonGroupSize) private var groupSize

  init(radius: CGFloat, @ViewBuilder content: @escaping (UnevenRoundedRectangle) -> Content) {
    self.radius = radius
    self.content = content
  }

  var body: some View {
    if let group {
      content(shape(group))
        .onGeometryChange(for: CGRect.self) { $0.frame(in: .named(ButtonGroupSpace.group)) } action: { frame = $0 }
    } else {
      content(UnevenRoundedRectangle(cornerRadii: RectangleCornerRadii(
        topLeading: radius,
        bottomLeading: radius,
        bottomTrailing: radius,
        topTrailing: radius
      ), style: .continuous))
    }
  }

  private func shape(_ group: Axis) -> UnevenRoundedRectangle {
    let horizontal = group == .horizontal
    let first = horizontal ? frame.minX <= 0.5 : frame.minY <= 0.5
    let last = horizontal
      ? frame.maxX >= groupSize.width - 0.5
      : frame.maxY >= groupSize.height - 0.5
    let round = horizontal ? frame.height / 2 : Radius.xl2
    let start: CGFloat = first ? round : 0
    let end: CGFloat = last ? round : 0
    let radii = horizontal
      ? RectangleCornerRadii(topLeading: start, bottomLeading: start, bottomTrailing: end, topTrailing: end)
      : RectangleCornerRadii(topLeading: start, bottomLeading: end, bottomTrailing: end, topTrailing: start)
    return UnevenRoundedRectangle(cornerRadii: radii, style: .continuous)
  }
}

private struct ButtonGroupClip: ViewModifier {
  let shape: AnyShape?

  func body(content: Content) -> some View {
    if let shape {
      content.clipShape(shape)
    } else {
      content
    }
  }
}

public struct ButtonGroupText<Content: View>: View {
  let content: Content

  @Environment(\.buttonGroup) private var group

  public init(@ViewBuilder content: () -> Content) {
    self.content = content()
  }

  public var body: some View {
    let shape = group == nil ? AnyShape(Capsule()) : AnyShape(Rectangle())
    HStack(spacing: 8) {
      content
    }
    .labelStyle(ButtonLabelStyle(spacing: 8, iconSize: 16))
    .scaledFont(.sm)
    .lineLimit(1)
    .foregroundStyle(Color.label)
    .padding(.horizontal, 10)
    .frame(minHeight: 36)
    .frame(maxWidth: group == .vertical ? .infinity : nil, maxHeight: group == .horizontal ? .infinity : nil)
    .background(Color.control, in: shape)
    .anchorPreference(key: ButtonGroupFramesKey.self, value: .bounds) { anchor in
      group == nil ? [] : [ButtonGroupFrame(bounds: anchor, outlined: false)]
    }
  }
}

extension ButtonGroupText where Content == Text {
  public init(_ title: LocalizedStringKey) {
    self.init { Text(title) }
  }

  public init(verbatim title: String) {
    self.init { Text(verbatim: title) }
  }
}

public struct ButtonGroupSeparator: View {
  let orientation: Axis

  public init(_ orientation: Axis = .vertical) {
    self.orientation = orientation
  }

  public var body: some View {
    let vertical = orientation == .vertical
    Rectangle()
      .fill(Color.label.opacity(0.2))
      .frame(width: vertical ? 1 : nil, height: vertical ? nil : 1)
      .padding(vertical ? .vertical : .horizontal, 9)
      .frame(maxWidth: vertical ? nil : .infinity, maxHeight: vertical ? .infinity : nil)
      .padding(vertical ? .trailing : .bottom, -1)
      .zIndex(1)
      .accessibilityHidden(true)
  }
}
```

```swift title="swift/Components/Checkbox.swift"
import PhosphorSwift
import SwiftUI

extension Shadow {
  static let control = Shadow(color: .black.opacity(0.08), radius: 0.5, y: 0.5)
  static let thumb = Shadow(color: .black.opacity(0.12), radius: 1.5, y: 1)
}

struct SelectionIndicator<Mark: View>: View {
  let checked: Bool
  let pressed: Bool
  let cornerRadius: CGFloat
  let mark: Mark

  @Environment(\.isEnabled) private var isEnabled
  @Environment(\.isInvalid) private var invalid
  @Environment(\.colorScheme) private var colorScheme

  init(checked: Bool, pressed: Bool, cornerRadius: CGFloat, @ViewBuilder mark: () -> Mark) {
    self.checked = checked
    self.pressed = pressed
    self.cornerRadius = cornerRadius
    self.mark = mark()
  }

  var body: some View {
    let shape = RoundedRectangle(cornerRadius: cornerRadius, style: .continuous)
    ZStack {
      shape.fill(fill)
      shape.strokeBorder(border, lineWidth: 1)
      if checked {
        mark
      }
    }
    .frame(width: 16, height: 16)
    .shadow(raised ? .control : Shadow(color: .clear, radius: 0))
  }

  private var isDark: Bool { colorScheme == .dark }

  private var raised: Bool { !checked && isEnabled && !isDark }

  private var fill: Color {
    if checked {
      return !isEnabled ? .accentDisabled : pressed ? .accentPressed : .accent
    }
    if !isEnabled { return .controlDisabled }
    if isDark { return pressed ? .labelTertiary.opacity(0.6) : .labelQuaternary }
    return pressed ? .control : .surface
  }

  private var border: Color {
    if checked {
      return !isEnabled ? .clear : pressed ? .accentPressed : .accent
    }
    if !isEnabled { return isDark ? .clear : .label.opacity(0.1) }
    if invalid { return .danger }
    return isDark ? .clear : .label.opacity(0.25)
  }
}

struct PressReader<Content: View>: ButtonStyle {
  let content: (Bool) -> Content

  init(@ViewBuilder content: @escaping (Bool) -> Content) {
    self.content = content
  }

  func makeBody(configuration: Configuration) -> some View {
    content(configuration.isPressed)
  }
}

public struct CheckboxStyle: ToggleStyle {
  public init() {}

  public func makeBody(configuration: Configuration) -> some View {
    HapticButton(style: PressReader { pressed in
      HStack(spacing: 12) {
        SelectionIndicator(
          checked: configuration.isOn || configuration.isMixed,
          pressed: pressed,
          cornerRadius: 4
        ) {
          (configuration.isMixed ? Ph.minus.regular : Ph.check.regular)
            .frame(width: 14, height: 14)
            .foregroundStyle(Color.onAccent)
        }
        configuration.label
      }
      .contentShape(Rectangle().inset(by: -8))
    }) {
      configuration.isOn.toggle()
      return true
    }
    .accessibilityElement(children: .combine)
    .accessibilityRemoveTraits(.isButton)
    .accessibilityAddTraits(.isToggle)
    .accessibilityValue(
      configuration.isMixed
        ? Text("Mixed")
        : configuration.isOn ? Text("Checked") : Text("Unchecked")
    )
  }
}

extension ToggleStyle where Self == CheckboxStyle {
  public static var checkbox: CheckboxStyle { CheckboxStyle() }
}
```

```swift title="swift/Components/DropdownMenu.swift"
import PhosphorSwift
import SwiftUI

enum MenuPresentation: Sendable {
  case system, popup
}

extension EnvironmentValues {
  @Entry var menuPresentation: MenuPresentation = .system
  @Entry var menuRadio = MenuRadioContext()
}

struct MenuRadioContext: @unchecked Sendable {
  var selected: AnyHashable?
  var select: @MainActor @Sendable (AnyHashable) -> Void = { _ in }
}

public struct DropdownMenu<Label: View, Content: View>: View {
  let side: Edge
  let align: PopupAlignment
  let sideOffset: CGFloat
  let alignOffset: CGFloat
  let external: Binding<Bool>?
  let content: () -> Content
  let label: Label

  @State private var local = false

  public init(
    isPresented: Binding<Bool>? = nil,
    side: Edge = .bottom,
    align: PopupAlignment = .start,
    sideOffset: CGFloat = 4,
    alignOffset: CGFloat = 0,
    @ViewBuilder content: @escaping () -> Content,
    @ViewBuilder label: () -> Label
  ) {
    self.external = isPresented
    self.side = side
    self.align = align
    self.sideOffset = sideOffset
    self.alignOffset = alignOffset
    self.content = content
    self.label = label()
  }

  public var body: some View {
    let binding = external ?? $local
    Button {
      binding.wrappedValue = true
    } label: {
      label
    }
    .accessibilityHint(Text("Opens a menu"))
    .anchoredPopup(
      isPresented: binding,
      side: side,
      align: align,
      sideOffset: sideOffset,
      alignOffset: alignOffset,
      minWidth: 192
    ) {
      MenuPanel(content: content)
    }
  }
}

extension DropdownMenu where Label == Text {
  public init(
    _ title: LocalizedStringKey,
    isPresented: Binding<Bool>? = nil,
    side: Edge = .bottom,
    align: PopupAlignment = .start,
    @ViewBuilder content: @escaping () -> Content
  ) {
    self.init(isPresented: isPresented, side: side, align: align, content: content) { Text(title) }
  }
}

struct MenuPanel<Content: View>: View {
  @ViewBuilder let content: () -> Content

  var body: some View {
    let stack = VStack(alignment: .leading, spacing: 0) {
      content()
    }
    .padding(6)
    ViewThatFits(in: .vertical) {
      stack
      ScrollView { stack }
    }
    .font(TextStyle.base.font())
    .tracking(TextStyle.base.letterSpacing)
    .foregroundStyle(Color.label)
    .environment(\.menuPresentation, .popup)
    .popupSurface(radius: Radius.xl)
    .accessibilityElement(children: .contain)
  }
}

struct MenuRowStyle: ButtonStyle {
  var destructive = false
  var inset = false
  var trailing: CGFloat = 12
  var selected = false

  @Environment(\.isEnabled) private var isEnabled

  func makeBody(configuration: Configuration) -> some View {
    configuration.label
      .labelStyle(ButtonLabelStyle(spacing: 10, iconSize: 16))
      .lineLimit(1)
      .foregroundStyle(!isEnabled ? Color.labelQuaternary : destructive ? .danger : .label)
      .padding(.leading, inset ? 38 : 12)
      .padding(.trailing, trailing)
      .padding(.vertical, 8)
      .frame(maxWidth: .infinity, alignment: .leading)
      .background(background(pressed: configuration.isPressed), in: RoundedRectangle(cornerRadius: Radius.md, style: .continuous))
      .contentShape(Rectangle())
  }

  private func background(pressed: Bool) -> Color {
    if pressed && isEnabled {
      return destructive ? .dangerSurfacePressed : .itemPressed
    }
    return selected ? .itemSelected : .clear
  }
}

private struct MenuCheckmark: View {
  let visible: Bool

  var body: some View {
    Ph.check.regular
      .frame(width: 16, height: 16)
      .opacity(visible ? 1 : 0)
      .padding(.trailing, 8)
      .accessibilityHidden(true)
  }
}

public struct DropdownMenuItem<Label: View>: View {
  public enum Variant: CaseIterable, Sendable {
    case `default`, destructive
  }

  let variant: Variant
  let inset: Bool
  let action: () -> Void
  let label: Label

  @Environment(\.menuPresentation) private var presentation
  @Environment(\.overlayDismiss) private var dismiss

  public init(
    variant: Variant = .default,
    inset: Bool = false,
    action: @escaping () -> Void,
    @ViewBuilder label: () -> Label
  ) {
    self.variant = variant
    self.inset = inset
    self.action = action
    self.label = label()
  }

  public var body: some View {
    if presentation == .system {
      Button(role: variant == .destructive ? .destructive : nil, action: action) {
        label
      }
    } else {
      Button {
        action()
        dismiss?()
      } label: {
        HStack(spacing: 10) {
          label
        }
      }
      .buttonStyle(MenuRowStyle(destructive: variant == .destructive, inset: inset))
    }
  }
}

extension DropdownMenuItem where Label == Text {
  public init(
    _ title: LocalizedStringKey,
    variant: Variant = .default,
    inset: Bool = false,
    action: @escaping () -> Void
  ) {
    self.init(variant: variant, inset: inset, action: action) { Text(title) }
  }
}

extension DropdownMenuItem where Label == SwiftUI.Label<Text, Image> {
  public init(
    _ title: LocalizedStringKey,
    icon: Image,
    variant: Variant = .default,
    action: @escaping () -> Void
  ) {
    self.init(variant: variant, action: action) {
      SwiftUI.Label { Text(title) } icon: { icon }
    }
  }
}

public struct DropdownMenuCheckboxItem<Label: View>: View {
  let isOn: Binding<Bool>
  let inset: Bool
  let label: Label

  @Environment(\.menuPresentation) private var presentation

  public init(isOn: Binding<Bool>, inset: Bool = false, @ViewBuilder label: () -> Label) {
    self.isOn = isOn
    self.inset = inset
    self.label = label()
  }

  public var body: some View {
    if presentation == .system {
      Toggle(isOn: isOn) { label }
    } else {
      Button {
        isOn.wrappedValue.toggle()
      } label: {
        label
      }
      .buttonStyle(MenuRowStyle(inset: inset, trailing: 32))
      .overlay(alignment: .trailing) { MenuCheckmark(visible: isOn.wrappedValue) }
      .accessibilityAddTraits(isOn.wrappedValue ? [.isToggle, .isSelected] : .isToggle)
    }
  }
}

extension DropdownMenuCheckboxItem where Label == Text {
  public init(_ title: LocalizedStringKey, isOn: Binding<Bool>, inset: Bool = false) {
    self.init(isOn: isOn, inset: inset) { Text(title) }
  }
}

public struct DropdownMenuRadioGroup<Content: View>: View {
  let selection: Binding<AnyHashable>
  let content: Content

  public init<Value: Hashable & Sendable>(selection: Binding<Value>, @ViewBuilder content: () -> Content) {
    self.selection = Binding(
      get: { AnyHashable(selection.wrappedValue) },
      set: { value in
        if let value = value.base as? Value { selection.wrappedValue = value }
      }
    )
    self.content = content()
  }

  public var body: some View {
    let binding = selection
    content
      .environment(
        \.menuRadio,
        MenuRadioContext(selected: binding.wrappedValue, select: { binding.wrappedValue = $0 })
      )
  }
}

public struct DropdownMenuRadioItem<Label: View>: View {
  let value: AnyHashable
  let inset: Bool
  let label: Label

  @Environment(\.menuPresentation) private var presentation
  @Environment(\.menuRadio) private var radio

  public init<Value: Hashable & Sendable>(value: Value, inset: Bool = false, @ViewBuilder label: () -> Label) {
    self.value = AnyHashable(value)
    self.inset = inset
    self.label = label()
  }

  public var body: some View {
    let selected = radio.selected == value
    if presentation == .system {
      let radio = radio
      let value = value
      Toggle(isOn: Binding(get: { selected }, set: { if $0 { radio.select(value) } })) { label }
    } else {
      Button {
        radio.select(value)
      } label: {
        label
      }
      .buttonStyle(MenuRowStyle(inset: inset, trailing: 32))
      .overlay(alignment: .trailing) { MenuCheckmark(visible: selected) }
      .accessibilityAddTraits(selected ? .isSelected : [])
    }
  }
}

extension DropdownMenuRadioItem where Label == Text {
  public init<Value: Hashable & Sendable>(_ title: LocalizedStringKey, value: Value, inset: Bool = false) {
    self.init(value: value, inset: inset) { Text(title) }
  }
}

public struct DropdownMenuLabel: View {
  let title: LocalizedStringKey
  let inset: Bool

  @Environment(\.menuPresentation) private var presentation

  public init(_ title: LocalizedStringKey, inset: Bool = false) {
    self.title = title
    self.inset = inset
  }

  public var body: some View {
    if presentation == .system {
      Text(title)
    } else {
      Text(title)
        .font(TextStyle.xs.font(weight: .semibold))
        .tracking(TextStyle.xs.letterSpacing)
        .foregroundStyle(Color.labelSecondary)
        .padding(.leading, inset ? 38 : 12)
        .padding(.trailing, 12)
        .padding(.vertical, 10)
        .frame(maxWidth: .infinity, alignment: .leading)
        .accessibilityAddTraits(.isHeader)
    }
  }
}

public struct DropdownMenuGroup<Content: View>: View {
  let content: Content

  @Environment(\.menuPresentation) private var presentation

  public init(@ViewBuilder content: () -> Content) {
    self.content = content()
  }

  public var body: some View {
    if presentation == .system {
      Section { content }
    } else {
      VStack(alignment: .leading, spacing: 0) { content }
    }
  }
}

public struct DropdownMenuSeparator: View {
  @Environment(\.menuPresentation) private var presentation

  public init() {}

  public var body: some View {
    if presentation == .system {
      Divider()
    } else {
      Rectangle()
        .fill(Color.separator.opacity(0.5))
        .frame(height: 1)
        .padding(.vertical, 6)
        .padding(.horizontal, -6)
        .accessibilityHidden(true)
    }
  }
}

public struct DropdownMenuSub<Label: View, Content: View>: View {
  let inset: Bool
  let content: Content
  let label: Label

  @State private var open = false
  @Environment(\.menuPresentation) private var presentation
  @Environment(\.accessibilityReduceMotion) private var reduceMotion

  public init(inset: Bool = false, @ViewBuilder content: () -> Content, @ViewBuilder label: () -> Label) {
    self.inset = inset
    self.content = content()
    self.label = label()
  }

  public var body: some View {
    if presentation == .system {
      Menu { content } label: { label }
    } else {
      VStack(alignment: .leading, spacing: 0) {
        Button {
          withAnimation(reduceMotion ? nil : .easeInOut(duration: 0.2)) { open.toggle() }
        } label: {
          HStack(spacing: 8) {
            label
            Spacer(minLength: 16)
            Ph.caretRight.regular
              .frame(width: 16, height: 16)
              .rotationEffect(.degrees(open ? 90 : 0))
          }
        }
        .buttonStyle(MenuRowStyle(inset: inset, selected: open))
        .accessibilityValue(Text(open ? "Expanded" : "Collapsed"))
        if open {
          VStack(alignment: .leading, spacing: 0) { content }
            .padding(.leading, 12)
            .transition(.opacity)
        }
      }
    }
  }
}

extension DropdownMenuSub where Label == Text {
  public init(_ title: LocalizedStringKey, inset: Bool = false, @ViewBuilder content: () -> Content) {
    self.init(inset: inset, content: content) { Text(title) }
  }
}

extension DropdownMenuSub where Label == SwiftUI.Label<Text, Image> {
  public init(_ title: LocalizedStringKey, icon: Image, @ViewBuilder content: () -> Content) {
    self.init(content: content) {
      SwiftUI.Label { Text(title) } icon: { icon }
    }
  }
}
```

```swift title="swift/Components/Field.swift"
import SwiftUI

extension EnvironmentValues {
  @Entry public var isInvalid = false
  @Entry var fieldInset = false
  @Entry var fieldGroupInset = false
  @Entry var fieldSetInset = false
}

extension View {
  public func invalid(_ isInvalid: Bool = true) -> some View {
    environment(\.isInvalid, isInvalid)
  }
}

public enum FieldOrientation: CaseIterable, Sendable {
  case vertical, horizontal
}

public struct Field<Content: View>: View {
  let orientation: FieldOrientation
  let invalid: Bool?
  let content: Content

  @Environment(\.fieldGroupInset) private var inset
  @Environment(\.isInvalid) private var inheritedInvalid

  public init(
    orientation: FieldOrientation = .vertical,
    invalid: Bool? = nil,
    @ViewBuilder content: () -> Content
  ) {
    self.orientation = orientation
    self.invalid = invalid
    self.content = content()
  }

  public var body: some View {
    Group {
      switch orientation {
      case .vertical:
        VStack(alignment: .leading, spacing: 12) { content }
      case .horizontal:
        HStack(alignment: .center, spacing: 12) { content }
      }
    }
    .frame(maxWidth: .infinity, alignment: .leading)
    .padding(.horizontal, inset ? 16 : 0)
    .padding(.vertical, inset ? 6 : 0)
    .frame(minHeight: inset ? 44 : nil)
    .overlay(alignment: .top) {
      if inset {
        Color.separator
          .frame(height: 1)
          .padding(.leading, 16)
          .offset(y: -1)
      }
    }
    .environment(\.fieldInset, inset)
    .environment(\.fieldGroupInset, false)
    .environment(\.isInvalid, invalid ?? inheritedInvalid)
  }
}

public struct FieldContent<Content: View>: View {
  let content: Content

  public init(@ViewBuilder content: () -> Content) {
    self.content = content()
  }

  public var body: some View {
    VStack(alignment: .leading, spacing: 4) {
      content
    }
    .frame(maxWidth: .infinity, alignment: .leading)
  }
}

public struct FieldTitle: View {
  let text: Text

  @Environment(\.isEnabled) private var isEnabled

  public init(_ title: LocalizedStringKey) {
    text = Text(title)
  }

  public init<S: StringProtocol>(_ title: S) {
    text = Text(title)
  }

  public var body: some View {
    text
      .scaledTextStyle(.base, weight: .semibold)
      .foregroundStyle(isEnabled ? Color.label : .labelQuaternary)
  }
}

public struct FieldDescription: View {
  let text: Text

  @Environment(\.fieldSetInset) private var inset

  public init(_ description: LocalizedStringKey) {
    text = Text(description)
  }

  public init<S: StringProtocol>(_ description: S) {
    text = Text(description)
  }

  public var body: some View {
    text
      .scaledTextStyle(inset ? .xs : .sm)
      .foregroundStyle(Color.labelSecondary)
      .multilineTextAlignment(.leading)
      .fixedSize(horizontal: false, vertical: true)
      .padding(.leading, inset ? 16 : 0)
  }
}

public struct FieldError: View {
  let messages: [String]
  let text: Text?

  public init(_ message: LocalizedStringKey) {
    messages = []
    text = Text(message)
  }

  public init(errors: [String?]) {
    var seen = Set<String>()
    messages = errors.compactMap { $0 }.filter { !$0.isEmpty && seen.insert($0).inserted }
    text = nil
  }

  public var body: some View {
    if let content {
      content
        .scaledTextStyle(.sm)
        .foregroundStyle(Color.danger)
        .multilineTextAlignment(.leading)
        .fixedSize(horizontal: false, vertical: true)
    }
  }

  private var content: Text? {
    if let text { return text }
    switch messages.count {
    case 0: return nil
    case 1: return Text(verbatim: messages[0])
    default: return Text(verbatim: messages.map { "\u{2022} \($0)" }.joined(separator: "\n"))
    }
  }
}

public enum FieldGroupVariant: CaseIterable, Sendable {
  case `default`, inset
}

public struct FieldGroup<Content: View>: View {
  let variant: FieldGroupVariant
  let content: Content

  public init(_ variant: FieldGroupVariant = .default, @ViewBuilder content: () -> Content) {
    self.variant = variant
    self.content = content()
  }

  public var body: some View {
    styled
      .environment(\.fieldGroupInset, variant == .inset)
      .environment(\.fieldSetInset, false)
      .transformPreference(FieldSetInsetKey.self) { $0 = variant == .inset }
  }

  @ViewBuilder private var styled: some View {
    let stack = VStack(alignment: .leading, spacing: variant == .inset ? 0 : 28) {
      content
    }
    .frame(maxWidth: .infinity, alignment: .leading)
    if variant == .inset {
      let shape = RoundedRectangle(cornerRadius: Radius.xl2, style: .continuous)
      stack
        .background(Color.surfaceSecondary, in: shape)
        .clipShape(shape)
    } else {
      stack
    }
  }
}

struct FieldSetInsetKey: PreferenceKey {
  static let defaultValue = false

  static func reduce(value: inout Bool, nextValue: () -> Bool) {
    value = value || nextValue()
  }
}

public struct FieldSet<Content: View>: View {
  let content: Content

  @State private var inset = false

  public init(@ViewBuilder content: () -> Content) {
    self.content = content()
  }

  public var body: some View {
    VStack(alignment: .leading, spacing: inset ? 8 : 24) {
      content
    }
    .frame(maxWidth: .infinity, alignment: .leading)
    .environment(\.fieldSetInset, inset)
    .onPreferenceChange(FieldSetInsetKey.self) { inset = $0 }
    .transformPreference(FieldSetInsetKey.self) { $0 = false }
    .accessibilityElement(children: .contain)
  }
}

public struct FieldLegend: View {
  public enum Variant: CaseIterable, Sendable {
    case legend, label
  }

  let text: Text
  let variant: Variant

  @Environment(\.fieldSetInset) private var inset
  @Environment(\.isEnabled) private var isEnabled

  public init(_ title: LocalizedStringKey, variant: Variant = .legend) {
    text = Text(title)
    self.variant = variant
  }

  public init<S: StringProtocol>(_ title: S, variant: Variant = .legend) {
    text = Text(title)
    self.variant = variant
  }

  public var body: some View {
    Group {
      if inset {
        text
          .textCase(.uppercase)
          .scaledTextStyle(.xs)
          .foregroundStyle(isEnabled ? Color.labelSecondary : .labelQuaternary)
          .padding(.leading, 16)
      } else {
        text
          .scaledTextStyle(.base, weight: .semibold)
          .foregroundStyle(isEnabled ? Color.label : .labelQuaternary)
          .padding(.bottom, 12)
      }
    }
    .accessibilityAddTraits(variant == .legend ? .isHeader : [])
  }
}

public struct FieldSeparator<Content: View>: View {
  let content: Content

  public init(@ViewBuilder content: () -> Content) {
    self.content = content()
  }

  public var body: some View {
    ZStack {
      Separator()
      content
        .scaledTextStyle(.sm)
        .foregroundStyle(Color.labelSecondary)
        .padding(.horizontal, 8)
        .background(Color.surface)
    }
    .frame(minHeight: 20)
    .padding(.vertical, -8)
  }
}

extension FieldSeparator where Content == EmptyView {
  public init() {
    self.init { EmptyView() }
  }
}

extension FieldSeparator where Content == Text {
  public init(_ title: LocalizedStringKey) {
    self.init { Text(title) }
  }
}
```

```swift title="swift/Components/Haptics.swift"
import SwiftUI

extension EnvironmentValues {
  @Entry public var hapticsEnabled = true
}

extension View {
  public func haptics(_ enabled: Bool) -> some View {
    environment(\.hapticsEnabled, enabled)
  }

  func hapticFeedback<Trigger: Equatable>(_ feedback: SensoryFeedback, trigger: Trigger) -> some View {
    modifier(HapticFeedbackModifier(feedback: feedback, trigger: trigger) { _, _ in true })
  }

  func hapticFeedback<Trigger: Equatable>(
    _ feedback: SensoryFeedback,
    trigger: Trigger,
    condition: @escaping (Trigger, Trigger) -> Bool
  ) -> some View {
    modifier(HapticFeedbackModifier(feedback: feedback, trigger: trigger, condition: condition))
  }
}

private struct HapticFeedbackModifier<Trigger: Equatable>: ViewModifier {
  let feedback: SensoryFeedback
  let trigger: Trigger
  let condition: (Trigger, Trigger) -> Bool

  @Environment(\.hapticsEnabled) private var enabled

  func body(content: Content) -> some View {
    let enabled = enabled
    let condition = condition
    content.sensoryFeedback(feedback, trigger: trigger) { old, new in
      enabled && condition(old, new)
    }
  }
}

enum HapticMoments {
  static func step(_ value: Double, bounds: ClosedRange<Double>, step: Double?) -> Int? {
    guard let step, step > 0 else { return nil }
    return Int(((value - bounds.lowerBound) / step).rounded())
  }

  static func lifted<Value: Equatable>(_ old: Value?, _ new: Value?) -> Bool {
    new != nil && old != new
  }

  static func crossed<Value: Equatable>(_ old: Value?, _ new: Value?) -> Bool {
    old == nil && new != nil
  }

  static func moved(_ old: Int?, _ new: Int?) -> Bool {
    guard let old, let new else { return false }
    return old != new
  }
}

struct HapticButton<Style: ButtonStyle>: View {
  let feedback: SensoryFeedback
  let action: () -> Bool
  let style: Style

  @State private var count = 0

  init(_ feedback: SensoryFeedback = .selection, style: Style, action: @escaping () -> Bool) {
    self.feedback = feedback
    self.style = style
    self.action = action
  }

  var body: some View {
    Button {
      if action() { count += 1 }
    } label: {
      EmptyView()
    }
    .buttonStyle(style)
    .hapticFeedback(feedback, trigger: count)
  }
}
```

```swift title="swift/Components/Overlay.swift"
import PhosphorSwift
import Observation
import SwiftUI

public enum PopupAlignment: Sendable, CaseIterable {
  case start, center, end
}

struct OverlayDismiss: Sendable {
  let action: @MainActor @Sendable () -> Void

  @MainActor func callAsFunction() {
    action()
  }
}

extension EnvironmentValues {
  @Entry var overlayDismiss: OverlayDismiss? = nil
}

private var instantTransaction: Transaction {
  var transaction = Transaction()
  transaction.disablesAnimations = true
  return transaction
}

struct CoverPresenter<Cover: View>: ViewModifier {
  @Binding var isPresented: Bool
  var enter: Animation = .easeOut(duration: 0.15)
  var exit: Animation = .easeIn(duration: 0.1)
  @ViewBuilder let cover: (Bool) -> Cover

  @State private var presented = false
  @State private var visible = false

  func body(content: Content) -> some View {
    let binding = $isPresented
    content
      .fullScreenCover(isPresented: coverBinding) {
        cover(visible)
          .environment(\.overlayDismiss, OverlayDismiss { binding.wrappedValue = false })
          .presentationBackground(.clear)
          .onAppear {
            withAnimation(enter) { visible = true }
          }
      }
      .onChange(of: isPresented, initial: true) { _, value in
        if value {
          withTransaction(instantTransaction) { presented = true }
        } else if presented {
          withAnimation(exit) {
            visible = false
          } completion: {
            withTransaction(instantTransaction) { presented = false }
          }
        }
      }
  }

  private var coverBinding: Binding<Bool> {
    Binding(
      get: { presented },
      set: { value in
        presented = value
        if !value {
          visible = false
          isPresented = false
        }
      }
    )
  }
}

struct PopupLayout: Layout {
  var anchor: CGRect
  var side: Edge
  var align: PopupAlignment
  var sideOffset: CGFloat
  var alignOffset: CGFloat
  var matchWidth: Bool
  var minWidth: CGFloat
  var maxHeight: CGFloat
  var margin: CGFloat = 8

  func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
    proposal.replacingUnspecifiedDimensions()
  }

  func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) {
    guard let view = subviews.first else { return }
    let anchor = anchor.offsetBy(dx: bounds.minX, dy: bounds.minY)
    let maxWidth = max(0, bounds.width - margin * 2)
    var width: CGFloat
    if matchWidth {
      width = max(anchor.width, minWidth)
    } else {
      width = max(view.sizeThatFits(ProposedViewSize(width: nil, height: nil)).width, minWidth)
    }
    width = min(width, maxWidth)
    let natural = view.sizeThatFits(ProposedViewSize(width: width, height: nil))
    let vertical = side == .top || side == .bottom
    let before = vertical
      ? anchor.minY - sideOffset - bounds.minY - margin
      : anchor.minX - sideOffset - bounds.minX - margin
    let after = vertical
      ? bounds.maxY - margin - anchor.maxY - sideOffset
      : bounds.maxX - margin - anchor.maxX - sideOffset
    let extent = vertical ? natural.height : natural.width
    var resolved = side
    switch side {
    case .bottom where extent > after && before > after: resolved = .top
    case .top where extent > before && after > before: resolved = .bottom
    case .trailing where extent > after && before > after: resolved = .leading
    case .leading where extent > before && after > before: resolved = .trailing
    default: break
    }
    var height = natural.height
    let space: CGFloat
    switch resolved {
    case .top, .leading: space = before
    case .bottom, .trailing: space = after
    }
    if vertical {
      height = min(height, maxHeight, max(space, 0))
    } else {
      height = min(height, maxHeight, bounds.height - margin * 2)
      width = min(width, max(space, 0))
    }
    var x: CGFloat
    var y: CGFloat
    if vertical {
      switch align {
      case .start: x = anchor.minX + alignOffset
      case .center: x = anchor.midX - width / 2 + alignOffset
      case .end: x = anchor.maxX - width - alignOffset
      }
      y = resolved == .bottom ? anchor.maxY + sideOffset : anchor.minY - sideOffset - height
    } else {
      switch align {
      case .start: y = anchor.minY + alignOffset
      case .center: y = anchor.midY - height / 2 + alignOffset
      case .end: y = anchor.maxY - height - alignOffset
      }
      x = resolved == .trailing ? anchor.maxX + sideOffset : anchor.minX - sideOffset - width
    }
    x = min(max(x, bounds.minX + margin), bounds.maxX - margin - width)
    y = min(max(y, bounds.minY + margin), bounds.maxY - margin - height)
    view.place(
      at: CGPoint(x: x, y: y),
      anchor: .topLeading,
      proposal: ProposedViewSize(width: width, height: height)
    )
  }
}

struct PopupPresenter<Popup: View>: ViewModifier {
  @Binding var isPresented: Bool
  var side: Edge = .bottom
  var align: PopupAlignment = .start
  var sideOffset: CGFloat = 4
  var alignOffset: CGFloat = 0
  var matchWidth = false
  var minWidth: CGFloat = 0
  var maxHeight: CGFloat = .infinity
  @ViewBuilder let popup: () -> Popup

  @State private var anchor = PopupAnchor()

  func body(content: Content) -> some View {
    content
      .onGeometryChange(for: CGRect.self) { proxy in
        proxy.frame(in: .global)
      } action: { frame in
        anchor.frame = frame
      }
      .modifier(
        CoverPresenter(isPresented: $isPresented) { visible in
          PopupCanvas(
            anchor: anchor,
            side: side,
            align: align,
            sideOffset: sideOffset,
            alignOffset: alignOffset,
            matchWidth: matchWidth,
            minWidth: minWidth,
            maxHeight: maxHeight,
            visible: visible,
            popup: popup
          )
        }
      )
  }
}

@Observable
final class PopupAnchor {
  var frame: CGRect = .zero
}

struct PopupCanvas<Popup: View>: View {
  let anchor: PopupAnchor
  let side: Edge
  let align: PopupAlignment
  let sideOffset: CGFloat
  let alignOffset: CGFloat
  let matchWidth: Bool
  let minWidth: CGFloat
  let maxHeight: CGFloat
  let visible: Bool
  @ViewBuilder let popup: () -> Popup

  @Environment(\.overlayDismiss) private var dismiss
  @Environment(\.accessibilityReduceMotion) private var reduceMotion

  var body: some View {
    GeometryReader { proxy in
      let origin = proxy.frame(in: .global).origin
      PopupLayout(
        anchor: anchor.frame.offsetBy(dx: -origin.x, dy: -origin.y),
        side: side,
        align: align,
        sideOffset: sideOffset,
        alignOffset: alignOffset,
        matchWidth: matchWidth,
        minWidth: minWidth,
        maxHeight: maxHeight
      ) {
        popup()
          .accessibilityAddTraits(.isModal)
          .scaleEffect(visible || reduceMotion ? 1 : 0.96, anchor: scaleAnchor)
          .opacity(visible ? 1 : 0)
      }
    }
    .background {
      Color.clear
        .contentShape(Rectangle())
        .ignoresSafeArea()
        .onTapGesture { dismiss?() }
        .accessibilityHidden(true)
    }
    .accessibilityAction(.escape) { dismiss?() }
  }

  private var scaleAnchor: UnitPoint {
    switch side {
    case .top: .bottom
    case .bottom: .top
    case .leading: .trailing
    case .trailing: .leading
    }
  }
}

extension View {
  func anchoredPopup<Popup: View>(
    isPresented: Binding<Bool>,
    side: Edge = .bottom,
    align: PopupAlignment = .start,
    sideOffset: CGFloat = 4,
    alignOffset: CGFloat = 0,
    matchWidth: Bool = false,
    minWidth: CGFloat = 0,
    maxHeight: CGFloat = .infinity,
    @ViewBuilder popup: @escaping () -> Popup
  ) -> some View {
    modifier(
      PopupPresenter(
        isPresented: isPresented,
        side: side,
        align: align,
        sideOffset: sideOffset,
        alignOffset: alignOffset,
        matchWidth: matchWidth,
        minWidth: minWidth,
        maxHeight: maxHeight,
        popup: popup
      )
    )
  }

  func popupSurface(radius: CGFloat = Radius.xl, shadow: Shadow = .lg) -> some View {
    modifier(PopupSurface(radius: radius, shadow: shadow))
  }
}

struct PopupSurface: ViewModifier {
  let radius: CGFloat
  let shadow: Shadow

  @Environment(\.colorScheme) private var colorScheme

  func body(content: Content) -> some View {
    let shape = RoundedRectangle(cornerRadius: radius, style: .continuous)
    content
      .clipShape(shape)
      .background {
        shape
          .fill(Color.surfaceRaised)
          .shadow(shadow)
      }
      .overlay {
        shape.strokeBorder(Color.label.opacity(colorScheme == .dark ? 0.1 : 0.05))
      }
  }
}

struct OverlayCloseButton: View {
  let label: LocalizedStringKey?

  @Environment(\.overlayDismiss) private var dismiss

  var body: some View {
    if let label {
      Button {
        dismiss?()
      } label: {
        Text(label).font(TextStyle.base.font())
      }
      .buttonStyle(.variant(.plain, size: .sm))
    } else {
      Button {
        dismiss?()
      } label: {
        Ph.x.regular
          .frame(width: 16, height: 16)
          .foregroundStyle(Color.label)
      }
      .buttonStyle(CloseIconButtonStyle())
      .accessibilityLabel(Text("Close"))
    }
  }
}

private struct CloseIconButtonStyle: ButtonStyle {
  func makeBody(configuration: Configuration) -> some View {
    configuration.label
      .frame(width: 32, height: 32)
      .background(configuration.isPressed ? Color.separator : .surfaceTertiary, in: Circle())
      .contentShape(Circle().inset(by: -8))
  }
}

struct ReversedVStack: Layout {
  var spacing: CGFloat

  func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
    let width = proposal.width
    var height: CGFloat = 0
    var widest: CGFloat = 0
    for view in subviews {
      let size = view.sizeThatFits(ProposedViewSize(width: width, height: nil))
      height += size.height
      widest = max(widest, size.width)
    }
    height += spacing * CGFloat(max(subviews.count - 1, 0))
    return CGSize(width: width ?? widest, height: height)
  }

  func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) {
    var y = bounds.minY
    for view in subviews.reversed() {
      let size = view.sizeThatFits(ProposedViewSize(width: bounds.width, height: nil))
      view.place(
        at: CGPoint(x: bounds.minX, y: y),
        anchor: .topLeading,
        proposal: ProposedViewSize(width: bounds.width, height: size.height)
      )
      y += size.height + spacing
    }
  }
}

struct ScrimLayer: View {
  let visible: Bool
  var dismissible = true

  @Environment(\.overlayDismiss) private var dismiss

  var body: some View {
    Color.scrim
      .ignoresSafeArea()
      .opacity(visible ? 1 : 0)
      .contentShape(Rectangle())
      .onTapGesture {
        if dismissible { dismiss?() }
      }
      .accessibilityHidden(true)
  }
}
```

```swift title="swift/Components/Select.swift"
import PhosphorSwift
import SwiftUI

struct SelectContext: @unchecked Sendable {
  var selected: AnyHashable?
  var registering = false
  var select: @MainActor @Sendable (AnyHashable) -> Void = { _ in }
}

extension EnvironmentValues {
  @Entry var select = SelectContext()
}

struct SelectLabelsKey: PreferenceKey {
  static var defaultValue: [AnyHashable: Text] { [:] }

  static func reduce(value: inout [AnyHashable: Text], nextValue: () -> [AnyHashable: Text]) {
    value.merge(nextValue()) { current, _ in current }
  }
}

public enum SelectSize: CaseIterable, Sendable {
  case `default`, sm
}

public struct SelectField<Value: Hashable & Sendable, Content: View>: View {
  public typealias Size = SelectSize

  let selection: Binding<Value?>
  let placeholder: LocalizedStringKey
  let size: Size
  let content: () -> Content

  @State private var open = false
  @State private var labels: [AnyHashable: Text] = [:]
  @Environment(\.isEnabled) private var isEnabled
  @Environment(\.isInvalid) private var invalid
  @Environment(\.colorScheme) private var colorScheme

  public init(
    selection: Binding<Value?>,
    placeholder: LocalizedStringKey = "Select",
    size: Size = .default,
    @ViewBuilder content: @escaping () -> Content
  ) {
    self.selection = selection
    self.placeholder = placeholder
    self.size = size
    self.content = content
  }

  public var body: some View {
    let binding = selection
    let current = binding.wrappedValue.map { AnyHashable($0) }
    let valueText = current.flatMap { labels[$0] }
    let context = SelectContext(
      selected: current,
      select: { value in
        if let value = value.base as? Value { binding.wrappedValue = value }
      }
    )
    ButtonGroupItem(radius: size == .sm ? Radius.md : Radius.lg) { shape in
      Button {
        open = true
      } label: {
        HStack(spacing: 6) {
          (valueText ?? Text(placeholder))
            .font(TextStyle.base.font())
            .tracking(TextStyle.base.letterSpacing)
            .lineLimit(1)
            .foregroundStyle(!isEnabled ? Color.labelQuaternary : valueText == nil ? .labelSecondary : .label)
            .frame(maxWidth: .infinity, alignment: .leading)
          Ph.caretUpDown.regular
            .frame(width: 16, height: 16)
            .foregroundStyle(Color.labelSecondary)
            .accessibilityHidden(true)
        }
        .padding(.horizontal, 12)
        .frame(height: size == .sm ? 36 : 44)
        .background(background, in: shape)
        .overlay {
          if invalid {
            shape.strokeBorder(Color.danger)
          }
        }
        .contentShape(shape)
      }
      .buttonStyle(SelectTriggerStyle())
    }
    .accessibilityHint(Text("Shows options"))
    .background {
      VStack(spacing: 0) { content() }
        .environment(\.select, SelectContext(registering: true))
        .hidden()
        .frame(width: 0, height: 0)
        .clipped()
        .accessibilityHidden(true)
        .allowsHitTesting(false)
    }
    .onPreferenceChange(SelectLabelsKey.self) { value in
      labels = value
    }
    .anchoredPopup(
      isPresented: $open,
      side: .bottom,
      align: .center,
      matchWidth: true,
      minWidth: 144
    ) {
      SelectPanel(content: content)
        .environment(\.select, context)
    }
  }

  private var background: Color {
    if !isEnabled { return .controlDisabled }
    if invalid { return .danger.opacity(colorScheme == .dark ? 0.1 : 0.05) }
    return .control
  }
}

private struct SelectTriggerStyle: ButtonStyle {
  func makeBody(configuration: Configuration) -> some View {
    configuration.label.opacity(configuration.isPressed ? 0.8 : 1)
  }
}

struct SelectPanel<Content: View>: View {
  @ViewBuilder let content: () -> Content

  var body: some View {
    let stack = VStack(alignment: .leading, spacing: 0) {
      content()
    }
    .padding(6)
    ViewThatFits(in: .vertical) {
      stack
      ScrollView { stack }
    }
    .font(TextStyle.base.font())
    .tracking(TextStyle.base.letterSpacing)
    .foregroundStyle(Color.label)
    .popupSurface(radius: Radius.xl)
    .accessibilityElement(children: .contain)
  }
}

public struct SelectItem: View {
  let value: AnyHashable
  let title: Text

  @Environment(\.select) private var select
  @Environment(\.overlayDismiss) private var dismiss

  public init<Value: Hashable & Sendable>(_ title: LocalizedStringKey, value: Value) {
    self.value = AnyHashable(value)
    self.title = Text(title)
  }

  public init<Value: Hashable & Sendable>(verbatim title: String, value: Value) {
    self.value = AnyHashable(value)
    self.title = Text(verbatim: title)
  }

  public var body: some View {
    if select.registering {
      Color.clear
        .frame(width: 0, height: 0)
        .preference(key: SelectLabelsKey.self, value: [value: title])
    } else {
      let selected = select.selected == value
      Button {
        select.select(value)
        dismiss?()
      } label: {
        title
      }
      .buttonStyle(MenuRowStyle(trailing: 32))
      .overlay(alignment: .trailing) {
        if selected {
          Ph.check.regular
            .frame(width: 16, height: 16)
            .foregroundStyle(Color.link)
            .padding(.trailing, 8)
            .accessibilityHidden(true)
        }
      }
      .accessibilityAddTraits(selected ? .isSelected : [])
    }
  }
}

public struct SelectGroup<Content: View>: View {
  let content: Content

  @Environment(\.select) private var select

  public init(@ViewBuilder content: () -> Content) {
    self.content = content()
  }

  public var body: some View {
    VStack(alignment: .leading, spacing: 0) { content }
  }
}

public struct SelectLabel: View {
  let title: LocalizedStringKey

  @Environment(\.select) private var select

  public init(_ title: LocalizedStringKey) {
    self.title = title
  }

  public var body: some View {
    if !select.registering {
      Text(title)
        .font(TextStyle.xs.font(weight: .semibold))
        .tracking(TextStyle.xs.letterSpacing)
        .foregroundStyle(Color.labelSecondary)
        .padding(.horizontal, 12)
        .padding(.vertical, 10)
        .frame(maxWidth: .infinity, alignment: .leading)
        .accessibilityAddTraits(.isHeader)
    }
  }
}

public struct SelectSeparator: View {
  @Environment(\.select) private var select

  public init() {}

  public var body: some View {
    if !select.registering {
      Rectangle()
        .fill(Color.separator)
        .frame(height: 1)
        .padding(.vertical, 6)
        .padding(.horizontal, -6)
        .accessibilityHidden(true)
    }
  }
}
```

```swift title="swift/Components/Separator.swift"
import SwiftUI

public struct Separator: View {
  let orientation: Axis

  public init(_ orientation: Axis = .horizontal) {
    self.orientation = orientation
  }

  public var body: some View {
    Rectangle()
      .fill(Color.separator)
      .frame(width: orientation == .vertical ? 1 : nil, height: orientation == .horizontal ? 1 : nil)
      .frame(maxWidth: orientation == .horizontal ? .infinity : nil, maxHeight: orientation == .vertical ? .infinity : nil)
      .accessibilityHidden(true)
  }
}
```

```swift title="swift/Components/TextVariant.swift"
import SwiftUI

public enum TextVariant: CaseIterable, Sendable {
  case `default`, h1, h2, h3, h4, p, blockquote, code, lead, large, small, muted

  var style: TextStyle {
    switch self {
    case .h1: .xl3
    case .h2: .xl2
    case .h3: .xl
    case .h4, .lead, .large: .lg
    case .code, .small, .muted: .sm
    default: .base
    }
  }

  var weight: Font.Weight {
    switch self {
    case .h1, .h2: .bold
    case .h3, .h4, .large, .code: .semibold
    case .small: .medium
    default: .regular
    }
  }

  var color: Color {
    switch self {
    case .lead, .muted: .labelSecondary
    default: .label
    }
  }

  var isHeading: Bool {
    switch self {
    case .h1, .h2, .h3, .h4: true
    default: false
    }
  }
}

private struct TextVariantModifier: ViewModifier {
  let variant: TextVariant

  func body(content: Content) -> some View {
    switch variant {
    case .blockquote:
      styled(content)
        .italic()
        .padding(.leading, 12)
        .overlay(alignment: .leading) {
          Rectangle().fill(Color.separator).frame(width: 2)
        }
        .padding(.top, 16)
    case .code:
      styled(content)
        .monospaced()
        .padding(.horizontal, 4)
        .padding(.vertical, 2)
        .background(Color.surfaceSecondary, in: RoundedRectangle(cornerRadius: Radius.sm, style: .continuous))
    case .p:
      styled(content).padding(.top, 12)
    default:
      styled(content)
    }
  }

  private func styled(_ content: Content) -> some View {
    content
      .scaledTextStyle(variant.style, weight: variant.weight)
      .foregroundStyle(variant.color)
      .accessibilityAddTraits(variant.isHeading ? .isHeader : [])
  }
}

extension View {
  public func textVariant(_ variant: TextVariant) -> some View {
    modifier(TextVariantModifier(variant: variant))
  }
}

private struct ScaledTextStyleModifier: ViewModifier {
  let style: TextStyle
  let weight: Font.Weight

  @ScaledMetric(relativeTo: .body) private var scale: CGFloat = 1

  func body(content: Content) -> some View {
    let size = style.size * scale
    let lineSpacing = max(0, style.lineHeight * scale - UIFont.systemFont(ofSize: size).lineHeight)
    content
      .font(.system(size: size, weight: weight))
      .tracking(style.letterSpacing)
      .lineSpacing(lineSpacing)
      .padding(.vertical, lineSpacing / 2)
  }
}

extension View {
  func scaledTextStyle(_ style: TextStyle, weight: Font.Weight = .regular) -> some View {
    modifier(ScaledTextStyleModifier(style: style, weight: weight))
  }

  func scaledFont(_ style: TextStyle, weight: Font.Weight = .regular) -> some View {
    modifier(ScaledFontModifier(style: style, weight: weight))
  }
}

private struct ScaledFontModifier: ViewModifier {
  let style: TextStyle
  let weight: Font.Weight

  @ScaledMetric(relativeTo: .body) private var scale: CGFloat = 1

  func body(content: Content) -> some View {
    content
      .font(.system(size: style.size * scale, weight: weight))
      .tracking(style.letterSpacing)
  }
}
```

5. Add the files to your app target.

**Jetpack Compose**

1. Set `minSdk` to 24 or higher and add the dependencies:

```kotlin title="build.gradle.kts"
implementation(platform("androidx.compose:compose-bom:2026.09.00"))
implementation("androidx.compose.foundation:foundation")
implementation("androidx.compose.ui:ui")
implementation("com.adamglin:phosphor-icon-android:1.0.0")
```

2. Copy the theme files every view uses:

```kt title="kotlin/theme/Theme.kt"
package com.esuiss.ui.theme

import androidx.compose.foundation.isSystemInDarkTheme
import androidx.compose.runtime.Composable
import androidx.compose.runtime.CompositionLocalProvider
import androidx.compose.runtime.Immutable
import androidx.compose.runtime.staticCompositionLocalOf
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.dropShadow
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.Shape
import androidx.compose.ui.graphics.shadow.Shadow as DropShadow
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.style.LineHeightStyle
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.DpOffset
import androidx.compose.ui.unit.em
import androidx.compose.ui.unit.sp

internal fun textStyle(size: Double, lineHeight: Double, letterSpacing: Double) = TextStyle(
    fontSize = size.sp,
    lineHeight = lineHeight.sp,
    letterSpacing = letterSpacing.em,
    lineHeightStyle = LineHeightStyle(
        alignment = LineHeightStyle.Alignment.Center,
        trim = LineHeightStyle.Trim.None,
    ),
)

@Immutable
data class Shadow(
    val offsetX: Dp,
    val offsetY: Dp,
    val blur: Dp,
    val color: Color,
)

fun Modifier.shadow(shadow: Shadow, shape: Shape): Modifier = dropShadow(
    shape,
    DropShadow(
        radius = shadow.blur,
        color = shadow.color,
        offset = DpOffset(shadow.offsetX, shadow.offsetY),
    ),
)

val LocalColors = staticCompositionLocalOf { LightColors }

object EsuissTheme {
    val colors: Colors
        @Composable get() = LocalColors.current

    val typography: Typography
        get() = Typography

    val radius: Radius
        get() = Radius

    val shadows: Shadows
        get() = Shadows
}

@Composable
fun EsuissTheme(
    darkTheme: Boolean = isSystemInDarkTheme(),
    content: @Composable () -> Unit,
) {
    CompositionLocalProvider(
        LocalColors provides if (darkTheme) DarkColors else LightColors,
        content = content,
    )
}
```

```kt title="kotlin/theme/Tokens.kt"
package com.esuiss.ui.theme

import androidx.compose.runtime.Immutable
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp

@Immutable
data class Colors(
    val surface: Color,
    val surfaceSecondary: Color,
    val surfaceTertiary: Color,
    val surfaceRaised: Color,
    val label: Color,
    val labelSecondary: Color,
    val labelTertiary: Color,
    val labelQuaternary: Color,
    val control: Color,
    val controlPressed: Color,
    val controlSelected: Color,
    val controlDisabled: Color,
    val onControlSelected: Color,
    val itemPressed: Color,
    val itemSelected: Color,
    val separator: Color,
    val separatorStrong: Color,
    val accent: Color,
    val accentPressed: Color,
    val accentSelected: Color,
    val accentDisabled: Color,
    val onAccent: Color,
    val accentSurface: Color,
    val accentSurfacePressed: Color,
    val link: Color,
    val focus: Color,
    val scrim: Color,
    val media: Color,
    val onMedia: Color,
    val danger: Color,
    val dangerSurface: Color,
    val dangerSurfacePressed: Color,
    val success: Color,
    val successSurface: Color,
    val warning: Color,
    val warningSurface: Color,
    val blue: Color,
    val green: Color,
    val orange: Color,
    val red: Color,
    val yellow: Color,
    val purple: Color,
    val pink: Color,
    val indigo: Color,
    val teal: Color,
    val mint: Color,
    val cyan: Color,
    val brown: Color,
    val gray: Color,
    val isDark: Boolean,
)

val LightColors = Colors(
    surface = Color(0xFFFFFFFF),
    surfaceSecondary = Color(0xFFF5F5F7),
    surfaceTertiary = Color(0xFFE8E8ED),
    surfaceRaised = Color(0xFFFFFFFF),
    label = Color(0xFF1D1D1F),
    labelSecondary = Color(0xFF6E6E73),
    labelTertiary = Color(0xFF86868B),
    labelQuaternary = Color(0xFFD2D2D7),
    control = Color(0xFF000000).copy(alpha = 0.04f),
    controlPressed = Color(0xFF000000).copy(alpha = 0.12f),
    controlSelected = Color(0xFF1D1D1F),
    controlDisabled = Color(0xFF000000).copy(alpha = 0.03f),
    onControlSelected = Color(0xFFFFFFFF),
    itemPressed = Color(0xFF000000).copy(alpha = 0.08f),
    itemSelected = Color(0xFF000000).copy(alpha = 0.06f),
    separator = Color(0xFFD2D2D7),
    separatorStrong = Color(0xFF86868B),
    accent = Color(0xFF0071E3),
    accentPressed = Color(0xFF005BB8),
    accentSelected = Color(0xFF0071E3),
    accentDisabled = Color(0xFF0071E3).copy(alpha = 0.4f),
    onAccent = Color(0xFFFFFFFF),
    accentSurface = Color(0xFF0071E3).copy(alpha = 0.09f),
    accentSurfacePressed = Color(0xFF0071E3).copy(alpha = 0.18f),
    link = Color(0xFF0066CC),
    focus = Color(0xFF0071E3),
    scrim = Color(0xFF000000).copy(alpha = 0.48f),
    media = Color(0xFF000000),
    onMedia = Color(0xFFFFFFFF),
    danger = Color(0xFFD0000A),
    dangerSurface = Color(0xFFD70015).copy(alpha = 0.08f),
    dangerSurfacePressed = Color(0xFFD70015).copy(alpha = 0.16f),
    success = Color(0xFF008009),
    successSurface = Color(0xFFEFFAF1),
    warning = Color(0xFFB64400),
    warningSurface = Color(0xFFFFF5EA),
    blue = Color(0xFF007AFF),
    green = Color(0xFF34C759),
    orange = Color(0xFFFF9500),
    red = Color(0xFFFF3B30),
    yellow = Color(0xFFFFCC00),
    purple = Color(0xFFAF52DE),
    pink = Color(0xFFFF2D55),
    indigo = Color(0xFF5856D6),
    teal = Color(0xFF30B0C7),
    mint = Color(0xFF00C7BE),
    cyan = Color(0xFF32ADE6),
    brown = Color(0xFFA2845E),
    gray = Color(0xFF8E8E93),
    isDark = false,
)

val DarkColors = Colors(
    surface = Color(0xFF000000),
    surfaceSecondary = Color(0xFF161617),
    surfaceTertiary = Color(0xFF2C2C2E),
    surfaceRaised = Color(0xFF1D1D1F),
    label = Color(0xFFF5F5F7),
    labelSecondary = Color(0xFFA1A1A6),
    labelTertiary = Color(0xFF86868B),
    labelQuaternary = Color(0xFF424245),
    control = Color(0xFFFFFFFF).copy(alpha = 0.1f),
    controlPressed = Color(0xFFFFFFFF).copy(alpha = 0.22f),
    controlSelected = Color(0xFFF5F5F7),
    controlDisabled = Color(0xFFFFFFFF).copy(alpha = 0.05f),
    onControlSelected = Color(0xFF000000),
    itemPressed = Color(0xFFFFFFFF).copy(alpha = 0.12f),
    itemSelected = Color(0xFFFFFFFF).copy(alpha = 0.1f),
    separator = Color(0xFF424245),
    separatorStrong = Color(0xFF6E6E73),
    accent = Color(0xFF0071E3),
    accentPressed = Color(0xFF004D9E),
    accentSelected = Color(0xFF0071E3),
    accentDisabled = Color(0xFF0071E3).copy(alpha = 0.4f),
    onAccent = Color(0xFFFFFFFF),
    accentSurface = Color(0xFF0071E3).copy(alpha = 0.18f),
    accentSurfacePressed = Color(0xFF0071E3).copy(alpha = 0.3f),
    link = Color(0xFF2997FF),
    focus = Color(0xFF0071E3),
    scrim = Color(0xFF000000).copy(alpha = 0.48f),
    media = Color(0xFF000000),
    onMedia = Color(0xFFFFFFFF),
    danger = Color(0xFFFF5447),
    dangerSurface = Color(0xFFFF453A).copy(alpha = 0.2f),
    dangerSurfacePressed = Color(0xFFFF453A).copy(alpha = 0.36f),
    success = Color(0xFF30D158),
    successSurface = Color(0xFF30D158).copy(alpha = 0.16f),
    warning = Color(0xFFFF9F0A),
    warningSurface = Color(0xFFFF9F0A).copy(alpha = 0.16f),
    blue = Color(0xFF0A84FF),
    green = Color(0xFF30D158),
    orange = Color(0xFFFF9F0A),
    red = Color(0xFFFF453A),
    yellow = Color(0xFFFFD60A),
    purple = Color(0xFFBF5AF2),
    pink = Color(0xFFFF375F),
    indigo = Color(0xFF5E5CE6),
    teal = Color(0xFF40C8E0),
    mint = Color(0xFF66D4CF),
    cyan = Color(0xFF64D2FF),
    brown = Color(0xFFAC8E68),
    gray = Color(0xFF8E8E93),
    isDark = true,
)

object Radius {
    val xs = 3.dp
    val sm = 5.dp
    val md = 8.dp
    val lg = 10.dp
    val xl = 12.dp
    val xl2 = 18.dp
    val xl3 = 28.dp
    val full = 9999.dp
}

object Typography {
    val xs3 = textStyle(11.0, 13.0, 0.006)
    val xs2 = textStyle(12.0, 16.0, 0.0)
    val xs = textStyle(13.0, 18.0, -0.006)
    val sm = textStyle(15.0, 20.0, -0.016)
    val md = textStyle(16.0, 21.0, -0.02)
    val base = textStyle(17.0, 22.0, -0.026)
    val lg = textStyle(20.0, 25.0, -0.023)
    val xl = textStyle(22.0, 28.0, -0.012)
    val xl2 = textStyle(28.0, 34.0, 0.014)
    val xl3 = textStyle(34.0, 41.0, 0.012)

    val all = listOf(xs3, xs2, xs, sm, md, base, lg, xl, xl2, xl3)
}

object Shadows {
    val md = Shadow(2.dp, 4.dp, 12.dp, Color.Black.copy(alpha = 0.08f))
    val lg = Shadow(0.dp, 4.dp, 24.dp, Color.Black.copy(alpha = 0.12f))
}
```

3. Copy the source and every file it uses:

```kt title="kotlin/patterns/SplitView.kt"
package com.esuiss.ui.patterns

import androidx.compose.animation.AnimatedContent
import androidx.compose.animation.core.tween
import androidx.compose.animation.fadeIn
import androidx.compose.animation.fadeOut
import androidx.compose.animation.slideInHorizontally
import androidx.compose.animation.slideOutHorizontally
import androidx.compose.animation.togetherWith
import androidx.compose.foundation.background
import androidx.compose.foundation.clickable
import androidx.compose.foundation.interaction.MutableInteractionSource
import androidx.compose.foundation.interaction.collectIsPressedAsState
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.BoxWithConstraints
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.ColumnScope
import androidx.compose.foundation.layout.PaddingValues
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxHeight
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.heightIn
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.width
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.foundation.text.BasicText
import androidx.compose.foundation.verticalScroll
import androidx.compose.runtime.Composable
import androidx.compose.runtime.CompositionLocalProvider
import androidx.compose.runtime.Immutable
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableFloatStateOf
import androidx.compose.runtime.mutableStateMapOf
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.setValue
import androidx.compose.runtime.staticCompositionLocalOf
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.clip
import androidx.compose.ui.draw.drawBehind
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.layout.onPlaced
import androidx.compose.ui.layout.positionInRoot
import androidx.compose.ui.semantics.Role
import androidx.compose.ui.semantics.heading
import androidx.compose.ui.semantics.contentDescription
import androidx.compose.ui.semantics.semantics
import androidx.compose.ui.semantics.selected
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.unit.dp
import com.adamglin.PhosphorIcons
import com.adamglin.phosphoricons.Bold
import com.adamglin.phosphoricons.Regular
import com.adamglin.phosphoricons.bold.CaretLeft
import com.adamglin.phosphoricons.regular.CaretRight
import com.esuiss.ui.components.Icon
import com.esuiss.ui.components.LocalContentColor
import com.esuiss.ui.components.LocalContentStyle
import com.esuiss.ui.theme.EsuissTheme
import com.esuiss.ui.theme.Radius
import com.esuiss.ui.theme.Typography
import kotlin.math.abs

enum class SplitViewColumn { Sidebar, List, Detail }

private class SplitViewPane(
    val kind: SplitViewColumn,
    val title: String?,
    val modifier: Modifier,
    val content: @Composable ColumnScope.() -> Unit,
)

interface SplitViewScope {
    fun SplitViewSidebar(title: String? = null, modifier: Modifier = Modifier, content: @Composable ColumnScope.() -> Unit)

    fun SplitViewList(title: String? = null, modifier: Modifier = Modifier, content: @Composable ColumnScope.() -> Unit)

    fun SplitViewDetail(title: String? = null, modifier: Modifier = Modifier, content: @Composable ColumnScope.() -> Unit)
}

private class SplitViewScopeImpl : SplitViewScope {
    val panes = mutableListOf<SplitViewPane>()

    override fun SplitViewSidebar(title: String?, modifier: Modifier, content: @Composable ColumnScope.() -> Unit) {
        panes += SplitViewPane(SplitViewColumn.Sidebar, title, modifier, content)
    }

    override fun SplitViewList(title: String?, modifier: Modifier, content: @Composable ColumnScope.() -> Unit) {
        panes += SplitViewPane(SplitViewColumn.List, title, modifier, content)
    }

    override fun SplitViewDetail(title: String?, modifier: Modifier, content: @Composable ColumnScope.() -> Unit) {
        panes += SplitViewPane(SplitViewColumn.Detail, title, modifier, content)
    }
}

private class SplitViewItemEdges {
    val edges = mutableStateMapOf<Any, Pair<Float, Float>>()
}

@Immutable
private class SplitViewContext(
    val compact: Boolean,
    val kind: SplitViewColumn,
    val setColumn: (SplitViewColumn) -> Unit,
    val items: SplitViewItemEdges = SplitViewItemEdges(),
)

private val LocalSplitView = staticCompositionLocalOf<SplitViewContext?> { null }

private fun next(kind: SplitViewColumn): SplitViewColumn = when (kind) {
    SplitViewColumn.Sidebar -> SplitViewColumn.List
    SplitViewColumn.List, SplitViewColumn.Detail -> SplitViewColumn.Detail
}

private fun previous(kind: SplitViewColumn): SplitViewColumn? = when (kind) {
    SplitViewColumn.Sidebar -> null
    SplitViewColumn.List -> SplitViewColumn.Sidebar
    SplitViewColumn.Detail -> SplitViewColumn.List
}

private val WideBreakpoint = 768.dp

@Composable
fun SplitView(
    modifier: Modifier = Modifier,
    column: SplitViewColumn? = null,
    defaultColumn: SplitViewColumn = SplitViewColumn.List,
    onColumnChange: (SplitViewColumn) -> Unit = {},
    content: SplitViewScope.() -> Unit,
) {
    val panes = SplitViewScopeImpl().apply(content).panes.toList()
    var uncontrolled by rememberSaveable { mutableStateOf(defaultColumn) }
    val current = column ?: uncontrolled
    val setColumn: (SplitViewColumn) -> Unit = { nextColumn ->
        if (column == null) uncontrolled = nextColumn
        onColumnChange(nextColumn)
    }
    val titles = panes.associate { it.kind to it.title }
    BoxWithConstraints(modifier = modifier) {
        if (maxWidth >= WideBreakpoint) {
            WideSplitView(panes, setColumn)
        } else {
            AnimatedContent(
                targetState = current,
                transitionSpec = {
                    val forward = targetState.ordinal > initialState.ordinal
                    (slideInHorizontally(tween(300)) { if (forward) it / 3 else -it / 3 } + fadeIn(tween(300))) togetherWith
                        (slideOutHorizontally(tween(300)) { if (forward) -it / 3 else it / 3 } + fadeOut(tween(200)))
                },
                label = "splitView",
            ) { shown ->
                val pane = panes.firstOrNull { it.kind == shown }
                if (pane != null) {
                    val back = previous(pane.kind)?.takeIf { target ->
                        panes.any { it.kind == target } && !(target == SplitViewColumn.Sidebar && titles[target] == null)
                    }
                    CompactPane(pane, back, back?.let { titles[it] }, setColumn)
                }
            }
        }
    }
}

@Composable
private fun CompactPane(
    pane: SplitViewPane,
    back: SplitViewColumn?,
    backTitle: String?,
    setColumn: (SplitViewColumn) -> Unit,
) {
    val colors = EsuissTheme.colors
    CompositionLocalProvider(
        LocalSplitView provides SplitViewContext(compact = true, kind = pane.kind, setColumn = setColumn, items = remember { SplitViewItemEdges() }),
        LocalContentStyle provides Typography.base.copy(color = colors.label),
        LocalContentColor provides colors.label,
    ) {
        Column(
            modifier = pane.modifier
                .fillMaxSize()
                .verticalScroll(rememberScrollState())
                .padding(PaddingValues(horizontal = 16.dp, vertical = 8.dp)),
        ) {
            if (back != null) {
                val interaction = remember { MutableInteractionSource() }
                val pressed by interaction.collectIsPressedAsState()
                val tint = if (pressed) colors.link.copy(alpha = 0.6f) else colors.link
                Row(
                    modifier = Modifier
                        .heightIn(min = 44.dp)
                        .clickable(interactionSource = interaction, indication = null, role = Role.Button) { setColumn(back) },
                    verticalAlignment = Alignment.CenterVertically,
                    horizontalArrangement = Arrangement.spacedBy(2.dp),
                ) {
                    Icon(PhosphorIcons.Bold.CaretLeft, contentDescription = if (backTitle == null) "Back" else null, size = 18.dp, tint = tint)
                    if (backTitle != null) BasicText(backTitle, style = Typography.base.copy(color = tint))
                }
            }
            if (pane.title != null) {
                BasicText(
                    pane.title,
                    modifier = Modifier.padding(bottom = 8.dp).semantics { heading() },
                    style = Typography.xl2.copy(color = colors.label, fontWeight = FontWeight.Bold),
                )
            }
            pane.content(this)
        }
    }
}

@Composable
private fun WideSplitView(panes: List<SplitViewPane>, setColumn: (SplitViewColumn) -> Unit) {
    val colors = EsuissTheme.colors
    val weights = panes.map {
        when (it.kind) {
            SplitViewColumn.Sidebar -> 0.20f
            SplitViewColumn.List -> 0.32f
            SplitViewColumn.Detail -> 0.48f
        }
    }
    Row(modifier = Modifier.fillMaxSize()) {
        panes.forEachIndexed { index, pane ->
            if (index > 0) Box(modifier = Modifier.width(1.dp).fillMaxHeight().background(colors.separator))
            CompositionLocalProvider(
                LocalSplitView provides SplitViewContext(compact = false, kind = pane.kind, setColumn = setColumn),
                LocalContentStyle provides Typography.base.copy(color = colors.label),
                LocalContentColor provides colors.label,
            ) {
                Column(
                    modifier = Modifier
                        .weight(weights[index])
                        .fillMaxHeight()
                        .verticalScroll(rememberScrollState())
                        .then(pane.modifier)
                        .padding(
                            when (pane.kind) {
                                SplitViewColumn.Sidebar -> PaddingValues(start = 12.dp, end = 12.dp, top = 4.dp, bottom = 12.dp)
                                SplitViewColumn.List -> PaddingValues(12.dp)
                                SplitViewColumn.Detail -> PaddingValues(32.dp)
                            },
                        ),
                ) {
                    if (pane.title != null) {
                        when (pane.kind) {
                            SplitViewColumn.Sidebar -> BasicText(
                                pane.title,
                                modifier = Modifier.padding(start = 12.dp, end = 12.dp, top = 12.dp, bottom = 8.dp).semantics { heading() },
                                style = Typography.xs.copy(color = colors.labelSecondary, fontWeight = FontWeight.SemiBold),
                            )
                            SplitViewColumn.List -> Box(
                                modifier = Modifier.semantics {
                                    heading()
                                    contentDescription = pane.title
                                },
                            )
                            SplitViewColumn.Detail -> BasicText(
                                pane.title,
                                modifier = Modifier.padding(bottom = 4.dp).semantics { heading() },
                                style = Typography.xl2.copy(color = colors.label, fontWeight = FontWeight.SemiBold),
                            )
                        }
                    }
                    pane.content(this)
                }
            }
        }
    }
}

@Composable
fun SplitViewItem(
    modifier: Modifier = Modifier,
    isActive: Boolean = false,
    onClick: () -> Unit = {},
    content: @Composable ColumnScope.() -> Unit,
) {
    val context = LocalSplitView.current ?: SplitViewContext(compact = true, kind = SplitViewColumn.List, setColumn = {})
    val colors = EsuissTheme.colors
    val interaction = remember { MutableInteractionSource() }
    val pressed by interaction.collectIsPressedAsState()
    val id = remember { Any() }
    var top by remember { mutableFloatStateOf(Float.NaN) }
    val click = {
        onClick()
        context.setColumn(next(context.kind))
    }
    if (context.compact) {
        val separator = colors.separator
        val edges = context.items.edges
        DisposableEffect(edges) { onDispose { edges.remove(id) } }
        val divided = edges.any { (key, edge) -> key !== id && abs(edge.second - top) < 1f }
        Row(
            modifier = modifier
                .fillMaxWidth()
                .heightIn(min = 44.dp)
                .onPlaced {
                    val y = it.positionInRoot().y
                    top = y
                    edges[id] = y to y + it.size.height
                }
                .background(if (pressed) colors.itemPressed else Color.Transparent)
                .drawBehind { if (divided) drawRect(separator, Offset.Zero, Size(size.width, 1.dp.toPx())) }
                .clickable(interactionSource = interaction, indication = null, role = Role.Button, onClick = click)
                .semantics { selected = isActive }
                .padding(vertical = 12.dp),
            horizontalArrangement = Arrangement.spacedBy(12.dp),
            verticalAlignment = Alignment.CenterVertically,
        ) {
            Column(modifier = Modifier.weight(1f), verticalArrangement = Arrangement.spacedBy(2.dp), content = content)
            if (context.kind != SplitViewColumn.Detail) {
                Icon(PhosphorIcons.Regular.CaretRight, contentDescription = null, size = 16.dp, tint = colors.labelTertiary)
            }
        }
    } else {
        val list = context.kind == SplitViewColumn.List
        val shape = RoundedCornerShape(if (list) Radius.xl else Radius.lg)
        Row(
            modifier = modifier
                .fillMaxWidth()
                .clip(shape)
                .background(
                    when {
                        pressed -> colors.itemPressed
                        isActive -> colors.surfaceSecondary
                        else -> Color.Transparent
                    },
                    shape,
                )
                .clickable(interactionSource = interaction, indication = null, role = Role.Button, onClick = click)
                .semantics { selected = isActive }
                .padding(horizontal = 12.dp, vertical = if (list) 12.dp else 8.dp),
            horizontalArrangement = Arrangement.spacedBy(12.dp),
            verticalAlignment = Alignment.CenterVertically,
        ) {
            Column(modifier = Modifier.weight(1f), verticalArrangement = Arrangement.spacedBy(2.dp), content = content)
        }
    }
}
```

```kt title="kotlin/components/Content.kt"
package com.esuiss.ui.components

import androidx.compose.runtime.compositionLocalOf
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.dp

val LocalContentStyle = compositionLocalOf { TextStyle.Default }

val LocalContentColor = compositionLocalOf { Color.Unspecified }

val LocalIconSize = compositionLocalOf { 20.dp }
```

```kt title="kotlin/components/Icon.kt"
package com.esuiss.ui.components

import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.size
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.ColorFilter
import androidx.compose.ui.graphics.takeOrElse
import androidx.compose.ui.graphics.vector.ImageVector
import androidx.compose.ui.unit.Dp
import com.esuiss.ui.theme.EsuissTheme

@Composable
fun Icon(
    imageVector: ImageVector,
    contentDescription: String?,
    modifier: Modifier = Modifier,
    size: Dp = LocalIconSize.current,
    tint: Color = LocalContentColor.current.takeOrElse { EsuissTheme.colors.label },
) {
    Image(
        imageVector = imageVector,
        contentDescription = contentDescription,
        modifier = modifier.size(size),
        colorFilter = ColorFilter.tint(tint),
    )
}
```

4. Update the `com.esuiss.ui` package names to match your project.

## Usage

```tsx
import { SplitView, SplitViewSidebar, SplitViewList, SplitViewDetail, SplitViewItem } from "@/components/patterns/split-view"
```

```tsx
<MailExample />
```

Give each pane a `title`; the back button only appears when the previous pane exists and has a title. Put `SplitViewItem`s in the sidebar and list panes, and use their `onPress` to set the selection in your own state.

The current column is uncontrolled with `defaultColumn` (`list` by default) or controlled with `column` and `onColumnChange`. `useSplitView` returns `isCompact`, `column` and `setColumn` for custom navigation.

## Examples

### Detail column

Starts on the detail column.

![Preview](https://uim.suiss.app/previews/patterns-split-view--detail-column.light.webp)

```tsx
import * as React from "react"
import { View } from "react-native"
import { SplitView, type SplitViewColumn, SplitViewDetail, SplitViewItem, SplitViewList, SplitViewSidebar } from "@/components/patterns/split-view"
import { Text } from "@/components/ui/text"

const mailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

const messages = [
  {
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
  },
  {
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
  },
  {
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space.",
  },
] as const

function MailExample({
  withSidebar = true,
  defaultColumn,
  breakpoint,
}: {
  withSidebar?: boolean
  defaultColumn?: SplitViewColumn
  breakpoint?: number
}) {
  const [mailbox, setMailbox] = React.useState("Inbox")
  const [messageId, setMessageId] = React.useState<string>("order")
  const message = messages.find((item) => item.id === messageId) ?? messages[0]

  return (
    <SplitView defaultColumn={defaultColumn} breakpoint={breakpoint}>
      {withSidebar ? (
        <SplitViewSidebar title="Mailboxes">
          {mailboxes.map((name) => (
            <SplitViewItem
              key={name}
              isActive={mailbox === name}
              onPress={() => setMailbox(name)}
            >
              {name}
            </SplitViewItem>
          ))}
        </SplitViewSidebar>
      ) : null}
      <SplitViewList title={mailbox}>
        {messages.map((item) => (
          <SplitViewItem
            key={item.id}
            isActive={item.id === messageId}
            onPress={() => setMessageId(item.id)}
          >
            <View className="flex-row items-baseline justify-between gap-2">
              <Text className="shrink font-semibold" numberOfLines={1}>
                {item.from}
              </Text>
              <Text className="text-sm text-label-secondary">{item.time}</Text>
            </View>
            <Text numberOfLines={1}>{item.subject}</Text>
            <Text className="text-sm text-label-secondary" numberOfLines={1}>
              {item.body}
            </Text>
          </SplitViewItem>
        ))}
      </SplitViewList>
      <SplitViewDetail title={message.subject}>
        <Text className="text-sm text-label-secondary">
          {message.from} · {message.time}
        </Text>
        <Text className="mt-6">{message.body}</Text>
      </SplitViewDetail>
    </SplitView>
  )
}

export function SplitViewDetailColumnExample() {
  return (
    <MailExample defaultColumn="detail" />
  )
}
```

```swift
import EsuissUI
import SwiftUI

struct SplitViewDetailColumnExample: View {
  var body: some View {
    SplitViewMail(column: .detail)
  }
}

struct SplitViewMessage: Identifiable {
  let id: String
  let from: String
  let time: String
  let subject: String
  let body: String
}

let splitViewMailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

let splitViewMessages = [
  SplitViewMessage(
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42."
  ),
  SplitViewMessage(
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan."
  ),
  SplitViewMessage(
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space."
  ),
]

struct SplitViewMail: View {
  var withSidebar = true

  @State private var column: SplitViewColumn
  @State private var mailbox = "Inbox"
  @State private var messageID = "order"

  init(column: SplitViewColumn = .list, withSidebar: Bool = true) {
    _column = State(initialValue: column)
    self.withSidebar = withSidebar
  }

  var message: SplitViewMessage {
    splitViewMessages.first { $0.id == messageID } ?? splitViewMessages[0]
  }

  var body: some View {
    SplitView(column: $column) {
      if withSidebar {
        SplitViewSidebar("Mailboxes") {
          ForEach(splitViewMailboxes, id: \.self) { name in
            SplitViewItem(isActive: mailbox == name, action: { mailbox = name }) {
              Text(verbatim: name)
            }
          }
        }
      }
      SplitViewList(verbatim: mailbox) {
        ForEach(splitViewMessages) { item in
          SplitViewItem(isActive: item.id == messageID, action: { messageID = item.id }) {
            HStack(alignment: .firstTextBaseline, spacing: 8) {
              Text(verbatim: item.from)
                .fontWeight(.semibold)
                .lineLimit(1)
                .frame(maxWidth: .infinity, alignment: .leading)
              Text(verbatim: item.time)
                .textStyle(.sm)
                .foregroundStyle(Color.labelSecondary)
            }
            Text(verbatim: item.subject)
              .lineLimit(1)
            Text(verbatim: item.body)
              .textStyle(.sm)
              .foregroundStyle(Color.labelSecondary)
              .lineLimit(1)
          }
        }
      }
      SplitViewDetail(verbatim: message.subject) {
        Text(verbatim: "\(message.from) · \(message.time)")
          .textStyle(.sm)
          .foregroundStyle(Color.labelSecondary)
        Text(verbatim: message.body)
          .foregroundStyle(Color.label)
          .fixedSize(horizontal: false, vertical: true)
          .padding(.top, 24)
      }
    }
    .containerRelativeFrame(.vertical) { height, _ in height - 32 }
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.style.TextOverflow
import androidx.compose.ui.unit.dp
import com.esuiss.ui.components.Text
import com.esuiss.ui.patterns.SplitView
import com.esuiss.ui.patterns.SplitViewColumn
import com.esuiss.ui.patterns.SplitViewItem
import com.esuiss.ui.theme.EsuissTheme
import com.esuiss.ui.theme.Typography

@Composable
fun SplitViewDetailColumnExample() {
    SplitViewMail(defaultColumn = SplitViewColumn.Detail)
}

class SplitViewMessage(
    val id: String,
    val from: String,
    val time: String,
    val subject: String,
    val body: String,
)

val splitViewMailboxes = listOf("Inbox", "Sent", "Drafts", "Archive")

val splitViewMessages = listOf(
    SplitViewMessage(
        "order",
        "Acme Store",
        "09:12",
        "Your order has shipped",
        "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
    ),
    SplitViewMessage(
        "meeting",
        "Jordan Lee",
        "Yesterday",
        "Tomorrow's meeting",
        "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
    ),
    SplitViewMessage(
        "storage",
        "Cloud Drive",
        "Mon",
        "Your storage is almost full",
        "Your cloud storage is 90% full. Upgrade your plan to get more space.",
    ),
)

@Composable
fun SplitViewMail(withSidebar: Boolean = true, defaultColumn: SplitViewColumn = SplitViewColumn.List) {
    var mailbox by rememberSaveable { mutableStateOf("Inbox") }
    var messageId by rememberSaveable { mutableStateOf("order") }
    val message = splitViewMessages.firstOrNull { it.id == messageId } ?: splitViewMessages.first()
    val colors = EsuissTheme.colors
    SplitView(modifier = Modifier.fillMaxWidth().height(640.dp), defaultColumn = defaultColumn) {
        if (withSidebar) {
            SplitViewSidebar(title = "Mailboxes") {
                splitViewMailboxes.forEach { name ->
                    SplitViewItem(isActive = mailbox == name, onClick = { mailbox = name }) {
                        Text(name)
                    }
                }
            }
        }
        SplitViewList(title = mailbox) {
            splitViewMessages.forEach { item ->
                SplitViewItem(isActive = item.id == messageId, onClick = { messageId = item.id }) {
                    Row(
                        modifier = Modifier.fillMaxWidth(),
                        horizontalArrangement = Arrangement.spacedBy(8.dp),
                        verticalAlignment = Alignment.CenterVertically,
                    ) {
                        Text(
                            item.from,
                            modifier = Modifier.weight(1f),
                            style = Typography.base.copy(fontWeight = FontWeight.SemiBold),
                            maxLines = 1,
                            overflow = TextOverflow.Ellipsis,
                        )
                        Text(item.time, style = Typography.sm.copy(color = colors.labelSecondary), maxLines = 1)
                    }
                    Text(item.subject, maxLines = 1, overflow = TextOverflow.Ellipsis)
                    Text(
                        item.body,
                        style = Typography.sm.copy(color = colors.labelSecondary),
                        maxLines = 1,
                        overflow = TextOverflow.Ellipsis,
                    )
                }
            }
        }
        SplitViewDetail(title = message.subject) {
            Text("${message.from} · ${message.time}", style = Typography.sm.copy(color = colors.labelSecondary))
            Text(message.body, modifier = Modifier.padding(top = 24.dp))
        }
    }
}
```

### Start on sidebar

Starts on the sidebar column.

![Preview](https://uim.suiss.app/previews/patterns-split-view--start-on-sidebar.light.webp)

```tsx
import * as React from "react"
import { View } from "react-native"
import { SplitView, type SplitViewColumn, SplitViewDetail, SplitViewItem, SplitViewList, SplitViewSidebar } from "@/components/patterns/split-view"
import { Text } from "@/components/ui/text"

const mailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

const messages = [
  {
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
  },
  {
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
  },
  {
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space.",
  },
] as const

function MailExample({
  withSidebar = true,
  defaultColumn,
  breakpoint,
}: {
  withSidebar?: boolean
  defaultColumn?: SplitViewColumn
  breakpoint?: number
}) {
  const [mailbox, setMailbox] = React.useState("Inbox")
  const [messageId, setMessageId] = React.useState<string>("order")
  const message = messages.find((item) => item.id === messageId) ?? messages[0]

  return (
    <SplitView defaultColumn={defaultColumn} breakpoint={breakpoint}>
      {withSidebar ? (
        <SplitViewSidebar title="Mailboxes">
          {mailboxes.map((name) => (
            <SplitViewItem
              key={name}
              isActive={mailbox === name}
              onPress={() => setMailbox(name)}
            >
              {name}
            </SplitViewItem>
          ))}
        </SplitViewSidebar>
      ) : null}
      <SplitViewList title={mailbox}>
        {messages.map((item) => (
          <SplitViewItem
            key={item.id}
            isActive={item.id === messageId}
            onPress={() => setMessageId(item.id)}
          >
            <View className="flex-row items-baseline justify-between gap-2">
              <Text className="shrink font-semibold" numberOfLines={1}>
                {item.from}
              </Text>
              <Text className="text-sm text-label-secondary">{item.time}</Text>
            </View>
            <Text numberOfLines={1}>{item.subject}</Text>
            <Text className="text-sm text-label-secondary" numberOfLines={1}>
              {item.body}
            </Text>
          </SplitViewItem>
        ))}
      </SplitViewList>
      <SplitViewDetail title={message.subject}>
        <Text className="text-sm text-label-secondary">
          {message.from} · {message.time}
        </Text>
        <Text className="mt-6">{message.body}</Text>
      </SplitViewDetail>
    </SplitView>
  )
}

export function SplitViewStartOnSidebarExample() {
  return (
    <MailExample defaultColumn="sidebar" />
  )
}
```

```swift
import EsuissUI
import SwiftUI

struct SplitViewStartOnSidebarExample: View {
  var body: some View {
    SplitViewMail(column: .sidebar)
  }
}

struct SplitViewMessage: Identifiable {
  let id: String
  let from: String
  let time: String
  let subject: String
  let body: String
}

let splitViewMailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

let splitViewMessages = [
  SplitViewMessage(
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42."
  ),
  SplitViewMessage(
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan."
  ),
  SplitViewMessage(
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space."
  ),
]

struct SplitViewMail: View {
  var withSidebar = true

  @State private var column: SplitViewColumn
  @State private var mailbox = "Inbox"
  @State private var messageID = "order"

  init(column: SplitViewColumn = .list, withSidebar: Bool = true) {
    _column = State(initialValue: column)
    self.withSidebar = withSidebar
  }

  var message: SplitViewMessage {
    splitViewMessages.first { $0.id == messageID } ?? splitViewMessages[0]
  }

  var body: some View {
    SplitView(column: $column) {
      if withSidebar {
        SplitViewSidebar("Mailboxes") {
          ForEach(splitViewMailboxes, id: \.self) { name in
            SplitViewItem(isActive: mailbox == name, action: { mailbox = name }) {
              Text(verbatim: name)
            }
          }
        }
      }
      SplitViewList(verbatim: mailbox) {
        ForEach(splitViewMessages) { item in
          SplitViewItem(isActive: item.id == messageID, action: { messageID = item.id }) {
            HStack(alignment: .firstTextBaseline, spacing: 8) {
              Text(verbatim: item.from)
                .fontWeight(.semibold)
                .lineLimit(1)
                .frame(maxWidth: .infinity, alignment: .leading)
              Text(verbatim: item.time)
                .textStyle(.sm)
                .foregroundStyle(Color.labelSecondary)
            }
            Text(verbatim: item.subject)
              .lineLimit(1)
            Text(verbatim: item.body)
              .textStyle(.sm)
              .foregroundStyle(Color.labelSecondary)
              .lineLimit(1)
          }
        }
      }
      SplitViewDetail(verbatim: message.subject) {
        Text(verbatim: "\(message.from) · \(message.time)")
          .textStyle(.sm)
          .foregroundStyle(Color.labelSecondary)
        Text(verbatim: message.body)
          .foregroundStyle(Color.label)
          .fixedSize(horizontal: false, vertical: true)
          .padding(.top, 24)
      }
    }
    .containerRelativeFrame(.vertical) { height, _ in height - 32 }
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.style.TextOverflow
import androidx.compose.ui.unit.dp
import com.esuiss.ui.components.Text
import com.esuiss.ui.patterns.SplitView
import com.esuiss.ui.patterns.SplitViewColumn
import com.esuiss.ui.patterns.SplitViewItem
import com.esuiss.ui.theme.EsuissTheme
import com.esuiss.ui.theme.Typography

@Composable
fun SplitViewStartOnSidebarExample() {
    SplitViewMail(defaultColumn = SplitViewColumn.Sidebar)
}

class SplitViewMessage(
    val id: String,
    val from: String,
    val time: String,
    val subject: String,
    val body: String,
)

val splitViewMailboxes = listOf("Inbox", "Sent", "Drafts", "Archive")

val splitViewMessages = listOf(
    SplitViewMessage(
        "order",
        "Acme Store",
        "09:12",
        "Your order has shipped",
        "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
    ),
    SplitViewMessage(
        "meeting",
        "Jordan Lee",
        "Yesterday",
        "Tomorrow's meeting",
        "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
    ),
    SplitViewMessage(
        "storage",
        "Cloud Drive",
        "Mon",
        "Your storage is almost full",
        "Your cloud storage is 90% full. Upgrade your plan to get more space.",
    ),
)

@Composable
fun SplitViewMail(withSidebar: Boolean = true, defaultColumn: SplitViewColumn = SplitViewColumn.List) {
    var mailbox by rememberSaveable { mutableStateOf("Inbox") }
    var messageId by rememberSaveable { mutableStateOf("order") }
    val message = splitViewMessages.firstOrNull { it.id == messageId } ?: splitViewMessages.first()
    val colors = EsuissTheme.colors
    SplitView(modifier = Modifier.fillMaxWidth().height(640.dp), defaultColumn = defaultColumn) {
        if (withSidebar) {
            SplitViewSidebar(title = "Mailboxes") {
                splitViewMailboxes.forEach { name ->
                    SplitViewItem(isActive = mailbox == name, onClick = { mailbox = name }) {
                        Text(name)
                    }
                }
            }
        }
        SplitViewList(title = mailbox) {
            splitViewMessages.forEach { item ->
                SplitViewItem(isActive = item.id == messageId, onClick = { messageId = item.id }) {
                    Row(
                        modifier = Modifier.fillMaxWidth(),
                        horizontalArrangement = Arrangement.spacedBy(8.dp),
                        verticalAlignment = Alignment.CenterVertically,
                    ) {
                        Text(
                            item.from,
                            modifier = Modifier.weight(1f),
                            style = Typography.base.copy(fontWeight = FontWeight.SemiBold),
                            maxLines = 1,
                            overflow = TextOverflow.Ellipsis,
                        )
                        Text(item.time, style = Typography.sm.copy(color = colors.labelSecondary), maxLines = 1)
                    }
                    Text(item.subject, maxLines = 1, overflow = TextOverflow.Ellipsis)
                    Text(
                        item.body,
                        style = Typography.sm.copy(color = colors.labelSecondary),
                        maxLines = 1,
                        overflow = TextOverflow.Ellipsis,
                    )
                }
            }
        }
        SplitViewDetail(title = message.subject) {
            Text("${message.from} · ${message.time}", style = Typography.sm.copy(color = colors.labelSecondary))
            Text(message.body, modifier = Modifier.padding(top = 24.dp))
        }
    }
}
```

### Two columns

Only list and detail panes, without a sidebar.

![Preview](https://uim.suiss.app/previews/patterns-split-view--two-columns.light.webp)

```tsx
import * as React from "react"
import { View } from "react-native"
import { SplitView, type SplitViewColumn, SplitViewDetail, SplitViewItem, SplitViewList, SplitViewSidebar } from "@/components/patterns/split-view"
import { Text } from "@/components/ui/text"

const mailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

const messages = [
  {
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
  },
  {
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
  },
  {
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space.",
  },
] as const

function MailExample({
  withSidebar = true,
  defaultColumn,
  breakpoint,
}: {
  withSidebar?: boolean
  defaultColumn?: SplitViewColumn
  breakpoint?: number
}) {
  const [mailbox, setMailbox] = React.useState("Inbox")
  const [messageId, setMessageId] = React.useState<string>("order")
  const message = messages.find((item) => item.id === messageId) ?? messages[0]

  return (
    <SplitView defaultColumn={defaultColumn} breakpoint={breakpoint}>
      {withSidebar ? (
        <SplitViewSidebar title="Mailboxes">
          {mailboxes.map((name) => (
            <SplitViewItem
              key={name}
              isActive={mailbox === name}
              onPress={() => setMailbox(name)}
            >
              {name}
            </SplitViewItem>
          ))}
        </SplitViewSidebar>
      ) : null}
      <SplitViewList title={mailbox}>
        {messages.map((item) => (
          <SplitViewItem
            key={item.id}
            isActive={item.id === messageId}
            onPress={() => setMessageId(item.id)}
          >
            <View className="flex-row items-baseline justify-between gap-2">
              <Text className="shrink font-semibold" numberOfLines={1}>
                {item.from}
              </Text>
              <Text className="text-sm text-label-secondary">{item.time}</Text>
            </View>
            <Text numberOfLines={1}>{item.subject}</Text>
            <Text className="text-sm text-label-secondary" numberOfLines={1}>
              {item.body}
            </Text>
          </SplitViewItem>
        ))}
      </SplitViewList>
      <SplitViewDetail title={message.subject}>
        <Text className="text-sm text-label-secondary">
          {message.from} · {message.time}
        </Text>
        <Text className="mt-6">{message.body}</Text>
      </SplitViewDetail>
    </SplitView>
  )
}

export function SplitViewTwoColumnsExample() {
  return (
    <MailExample withSidebar={false} />
  )
}
```

```swift
import EsuissUI
import SwiftUI

struct SplitViewTwoColumnsExample: View {
  var body: some View {
    SplitViewMail(withSidebar: false)
  }
}

struct SplitViewMessage: Identifiable {
  let id: String
  let from: String
  let time: String
  let subject: String
  let body: String
}

let splitViewMailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

let splitViewMessages = [
  SplitViewMessage(
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42."
  ),
  SplitViewMessage(
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan."
  ),
  SplitViewMessage(
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space."
  ),
]

struct SplitViewMail: View {
  var withSidebar = true

  @State private var column: SplitViewColumn
  @State private var mailbox = "Inbox"
  @State private var messageID = "order"

  init(column: SplitViewColumn = .list, withSidebar: Bool = true) {
    _column = State(initialValue: column)
    self.withSidebar = withSidebar
  }

  var message: SplitViewMessage {
    splitViewMessages.first { $0.id == messageID } ?? splitViewMessages[0]
  }

  var body: some View {
    SplitView(column: $column) {
      if withSidebar {
        SplitViewSidebar("Mailboxes") {
          ForEach(splitViewMailboxes, id: \.self) { name in
            SplitViewItem(isActive: mailbox == name, action: { mailbox = name }) {
              Text(verbatim: name)
            }
          }
        }
      }
      SplitViewList(verbatim: mailbox) {
        ForEach(splitViewMessages) { item in
          SplitViewItem(isActive: item.id == messageID, action: { messageID = item.id }) {
            HStack(alignment: .firstTextBaseline, spacing: 8) {
              Text(verbatim: item.from)
                .fontWeight(.semibold)
                .lineLimit(1)
                .frame(maxWidth: .infinity, alignment: .leading)
              Text(verbatim: item.time)
                .textStyle(.sm)
                .foregroundStyle(Color.labelSecondary)
            }
            Text(verbatim: item.subject)
              .lineLimit(1)
            Text(verbatim: item.body)
              .textStyle(.sm)
              .foregroundStyle(Color.labelSecondary)
              .lineLimit(1)
          }
        }
      }
      SplitViewDetail(verbatim: message.subject) {
        Text(verbatim: "\(message.from) · \(message.time)")
          .textStyle(.sm)
          .foregroundStyle(Color.labelSecondary)
        Text(verbatim: message.body)
          .foregroundStyle(Color.label)
          .fixedSize(horizontal: false, vertical: true)
          .padding(.top, 24)
      }
    }
    .containerRelativeFrame(.vertical) { height, _ in height - 32 }
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.style.TextOverflow
import androidx.compose.ui.unit.dp
import com.esuiss.ui.components.Text
import com.esuiss.ui.patterns.SplitView
import com.esuiss.ui.patterns.SplitViewColumn
import com.esuiss.ui.patterns.SplitViewItem
import com.esuiss.ui.theme.EsuissTheme
import com.esuiss.ui.theme.Typography

@Composable
fun SplitViewTwoColumnsExample() {
    SplitViewMail(withSidebar = false)
}

class SplitViewMessage(
    val id: String,
    val from: String,
    val time: String,
    val subject: String,
    val body: String,
)

val splitViewMailboxes = listOf("Inbox", "Sent", "Drafts", "Archive")

val splitViewMessages = listOf(
    SplitViewMessage(
        "order",
        "Acme Store",
        "09:12",
        "Your order has shipped",
        "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
    ),
    SplitViewMessage(
        "meeting",
        "Jordan Lee",
        "Yesterday",
        "Tomorrow's meeting",
        "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
    ),
    SplitViewMessage(
        "storage",
        "Cloud Drive",
        "Mon",
        "Your storage is almost full",
        "Your cloud storage is 90% full. Upgrade your plan to get more space.",
    ),
)

@Composable
fun SplitViewMail(withSidebar: Boolean = true, defaultColumn: SplitViewColumn = SplitViewColumn.List) {
    var mailbox by rememberSaveable { mutableStateOf("Inbox") }
    var messageId by rememberSaveable { mutableStateOf("order") }
    val message = splitViewMessages.firstOrNull { it.id == messageId } ?: splitViewMessages.first()
    val colors = EsuissTheme.colors
    SplitView(modifier = Modifier.fillMaxWidth().height(640.dp), defaultColumn = defaultColumn) {
        if (withSidebar) {
            SplitViewSidebar(title = "Mailboxes") {
                splitViewMailboxes.forEach { name ->
                    SplitViewItem(isActive = mailbox == name, onClick = { mailbox = name }) {
                        Text(name)
                    }
                }
            }
        }
        SplitViewList(title = mailbox) {
            splitViewMessages.forEach { item ->
                SplitViewItem(isActive = item.id == messageId, onClick = { messageId = item.id }) {
                    Row(
                        modifier = Modifier.fillMaxWidth(),
                        horizontalArrangement = Arrangement.spacedBy(8.dp),
                        verticalAlignment = Alignment.CenterVertically,
                    ) {
                        Text(
                            item.from,
                            modifier = Modifier.weight(1f),
                            style = Typography.base.copy(fontWeight = FontWeight.SemiBold),
                            maxLines = 1,
                            overflow = TextOverflow.Ellipsis,
                        )
                        Text(item.time, style = Typography.sm.copy(color = colors.labelSecondary), maxLines = 1)
                    }
                    Text(item.subject, maxLines = 1, overflow = TextOverflow.Ellipsis)
                    Text(
                        item.body,
                        style = Typography.sm.copy(color = colors.labelSecondary),
                        maxLines = 1,
                        overflow = TextOverflow.Ellipsis,
                    )
                }
            }
        }
        SplitViewDetail(title = message.subject) {
            Text("${message.from} · ${message.time}", style = Typography.sm.copy(color = colors.labelSecondary))
            Text(message.body, modifier = Modifier.padding(top = 24.dp))
        }
    }
}
```

### Wide

Sets `breakpoint` to `0` to always show the columns side by side.

![Preview](https://uim.suiss.app/previews/patterns-split-view--wide.light.webp)

```tsx
import * as React from "react"
import { View } from "react-native"
import { SplitView, type SplitViewColumn, SplitViewDetail, SplitViewItem, SplitViewList, SplitViewSidebar } from "@/components/patterns/split-view"
import { Text } from "@/components/ui/text"

const mailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

const messages = [
  {
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
  },
  {
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
  },
  {
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space.",
  },
] as const

function MailExample({
  withSidebar = true,
  defaultColumn,
  breakpoint,
}: {
  withSidebar?: boolean
  defaultColumn?: SplitViewColumn
  breakpoint?: number
}) {
  const [mailbox, setMailbox] = React.useState("Inbox")
  const [messageId, setMessageId] = React.useState<string>("order")
  const message = messages.find((item) => item.id === messageId) ?? messages[0]

  return (
    <SplitView defaultColumn={defaultColumn} breakpoint={breakpoint}>
      {withSidebar ? (
        <SplitViewSidebar title="Mailboxes">
          {mailboxes.map((name) => (
            <SplitViewItem
              key={name}
              isActive={mailbox === name}
              onPress={() => setMailbox(name)}
            >
              {name}
            </SplitViewItem>
          ))}
        </SplitViewSidebar>
      ) : null}
      <SplitViewList title={mailbox}>
        {messages.map((item) => (
          <SplitViewItem
            key={item.id}
            isActive={item.id === messageId}
            onPress={() => setMessageId(item.id)}
          >
            <View className="flex-row items-baseline justify-between gap-2">
              <Text className="shrink font-semibold" numberOfLines={1}>
                {item.from}
              </Text>
              <Text className="text-sm text-label-secondary">{item.time}</Text>
            </View>
            <Text numberOfLines={1}>{item.subject}</Text>
            <Text className="text-sm text-label-secondary" numberOfLines={1}>
              {item.body}
            </Text>
          </SplitViewItem>
        ))}
      </SplitViewList>
      <SplitViewDetail title={message.subject}>
        <Text className="text-sm text-label-secondary">
          {message.from} · {message.time}
        </Text>
        <Text className="mt-6">{message.body}</Text>
      </SplitViewDetail>
    </SplitView>
  )
}

export function SplitViewWideExample() {
  return (
    <MailExample breakpoint={0} />
  )
}
```

### Wide two columns

Side-by-side list and detail panes without a sidebar.

![Preview](https://uim.suiss.app/previews/patterns-split-view--wide-two-columns.light.webp)

```tsx
import * as React from "react"
import { View } from "react-native"
import { SplitView, type SplitViewColumn, SplitViewDetail, SplitViewItem, SplitViewList, SplitViewSidebar } from "@/components/patterns/split-view"
import { Text } from "@/components/ui/text"

const mailboxes = ["Inbox", "Sent", "Drafts", "Archive"]

const messages = [
  {
    id: "order",
    from: "Acme Store",
    time: "09:12",
    subject: "Your order has shipped",
    body: "Order #1042 will be delivered tomorrow. Tracking number: 4815 1623 42.",
  },
  {
    id: "meeting",
    from: "Jordan Lee",
    time: "Yesterday",
    subject: "Tomorrow's meeting",
    body: "Does 10:00 work for you? On the agenda: the Q4 budget and the campaign plan.",
  },
  {
    id: "storage",
    from: "Cloud Drive",
    time: "Mon",
    subject: "Your storage is almost full",
    body: "Your cloud storage is 90% full. Upgrade your plan to get more space.",
  },
] as const

function MailExample({
  withSidebar = true,
  defaultColumn,
  breakpoint,
}: {
  withSidebar?: boolean
  defaultColumn?: SplitViewColumn
  breakpoint?: number
}) {
  const [mailbox, setMailbox] = React.useState("Inbox")
  const [messageId, setMessageId] = React.useState<string>("order")
  const message = messages.find((item) => item.id === messageId) ?? messages[0]

  return (
    <SplitView defaultColumn={defaultColumn} breakpoint={breakpoint}>
      {withSidebar ? (
        <SplitViewSidebar title="Mailboxes">
          {mailboxes.map((name) => (
            <SplitViewItem
              key={name}
              isActive={mailbox === name}
              onPress={() => setMailbox(name)}
            >
              {name}
            </SplitViewItem>
          ))}
        </SplitViewSidebar>
      ) : null}
      <SplitViewList title={mailbox}>
        {messages.map((item) => (
          <SplitViewItem
            key={item.id}
            isActive={item.id === messageId}
            onPress={() => setMessageId(item.id)}
          >
            <View className="flex-row items-baseline justify-between gap-2">
              <Text className="shrink font-semibold" numberOfLines={1}>
                {item.from}
              </Text>
              <Text className="text-sm text-label-secondary">{item.time}</Text>
            </View>
            <Text numberOfLines={1}>{item.subject}</Text>
            <Text className="text-sm text-label-secondary" numberOfLines={1}>
              {item.body}
            </Text>
          </SplitViewItem>
        ))}
      </SplitViewList>
      <SplitViewDetail title={message.subject}>
        <Text className="text-sm text-label-secondary">
          {message.from} · {message.time}
        </Text>
        <Text className="mt-6">{message.body}</Text>
      </SplitViewDetail>
    </SplitView>
  )
}

export function SplitViewWideTwoColumnsExample() {
  return (
    <MailExample withSidebar={false} breakpoint={0} />
  )
}
```

## API Reference

### SplitView

The root that tracks the current column and the layout mode.

### SplitViewSidebar

The first pane, for top-level sections.

### SplitViewList

The middle pane, for the items in a section.

### SplitViewDetail

The last pane, for the selected item.

### SplitViewItem

A pressable row that moves to the next column.

## Accessibility

- Pane titles have the `heading` role, and panes are labelled by string titles.
- On phones, screen reader focus moves to the new pane's heading after navigating.
- `SplitViewItem` exposes its `selected` state.
- Back and row chevrons mirror in right-to-left layouts.

## Notes

- On phones the new pane fades in, respecting the system reduce motion setting.
- Active rows use `bg-surface-secondary`; panes are divided by `border-separator`.