# Header

A navigation bar with a back button, a centered title, actions and an optional large title that collapses on scroll.

Header is an open-source mobile component from suiss/uim 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/components/header

![Preview](https://uim.suiss.app/previews/components-header--default.light.webp)

```tsx
import { View } from "react-native"
import { Button } from "@/components/ui/button"
import { Header, HeaderActions, HeaderBack, HeaderTitle } from "@/components/ui/header"
import { Text } from "@/components/ui/text"

export function HeaderExample() {
  return (
    <View className="-mx-4 -mt-4">
      <Header>
        <HeaderBack>Settings</HeaderBack>
        <HeaderTitle>Profile</HeaderTitle>
        <HeaderActions>
          <Button variant="plain" size="sm">
            <Text className="font-semibold">Edit</Text>
          </Button>
        </HeaderActions>
      </Header>
    </View>
  )
}
```

```swift
import EsuissUI
import SwiftUI

struct HeaderExample: View {
  var body: some View {
    Header {
      HeaderTitle("Profile")
    } leading: {
      HeaderBack("Settings")
    } trailing: {
      HeaderActions {
        Button {} label: {
          Text("Edit").fontWeight(.semibold)
        }
        .buttonStyle(.variant(.plain, size: .sm))
      }
    }
    .headerStoryBleed()
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Column
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.layout
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.unit.dp
import com.esuiss.ui.components.Button
import com.esuiss.ui.components.ButtonSize
import com.esuiss.ui.components.ButtonVariant
import com.esuiss.ui.components.Header
import com.esuiss.ui.components.HeaderActions
import com.esuiss.ui.components.HeaderBack
import com.esuiss.ui.components.HeaderTitle
import com.esuiss.ui.components.Text

fun Modifier.headerBleed(): Modifier = layout { measurable, constraints ->
    val inset = 16.dp.roundToPx()
    val width = constraints.maxWidth + inset * 2
    val placeable = measurable.measure(constraints.copy(minWidth = width, maxWidth = width))
    layout(constraints.maxWidth, (placeable.height - inset).coerceAtLeast(0)) {
        placeable.place(-inset, -inset)
    }
}

@Composable
fun HeaderPlainAction(text: String) {
    Button(onClick = {}, variant = ButtonVariant.Plain, size = ButtonSize.Sm) {
        Text(text, style = TextStyle(fontWeight = FontWeight.SemiBold))
    }
}

@Composable
fun HeaderDefault() {
    Column(Modifier.headerBleed()) {
        Header {
            HeaderBack(onClick = {}, text = "Settings")
            HeaderTitle("Profile")
            HeaderActions { HeaderPlainAction("Edit") }
        }
    }
}
```

`Header` is a 44-point bar that sorts its children into three slots: `HeaderBack` and leading `HeaderActions` on the start side, `HeaderTitle` in the center, and everything else on the end side. The side slots share the remaining width equally, so the title stays centered.

For a large title, create a scroll state with `useHeaderScroll()`, pass it to both `Header` and `HeaderScrollView`, and put a `HeaderLargeTitle` at the top of the scroll view. As the large title scrolls away, the small title fades in and a hairline appears under the bar. Pulling down stretches the large title slightly.

## Installation

```bash title="Terminal"
npx @esuiss/uim@latest add header
```

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

```bash title="Terminal"
npx @esuiss/uim@latest add header --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).

3. Copy the source into `components/ui/header.tsx`:

```tsx title="uniwind/components/ui/header.tsx"
import { cn } from "cn"
import { CaretLeftIcon } from "phosphor-react-native"
import * as React from "react"
import {
  I18nManager,
  Pressable,
  type ScrollViewProps,
  View,
  type ViewProps,
} from "react-native"
import Animated, {
  interpolate,
  type SharedValue,
  useAnimatedScrollHandler,
  useAnimatedStyle,
  useSharedValue,
} from "react-native-reanimated"
import { AnimatedView } from "@/components/ui/animated-view"
import { Icon } from "@/components/ui/icon"
import { Text } from "@/components/ui/text"

type HeaderScroll = {
  scrollY: SharedValue<number>
  largeTitleHeight: SharedValue<number>
  onScroll: ReturnType<typeof useAnimatedScrollHandler>
}

const HeaderContext = React.createContext<HeaderScroll | null>(null)

function useHeaderScroll(): HeaderScroll {
  const scrollY = useSharedValue(0)
  const largeTitleHeight = useSharedValue(0)
  const onScroll = useAnimatedScrollHandler((event) => {
    scrollY.value = event.contentOffset.y
  })
  return React.useMemo(
    () => ({ scrollY, largeTitleHeight, onScroll }),
    [scrollY, largeTitleHeight, onScroll]
  )
}

function wrapText(children: React.ReactNode, className: string) {
  if (typeof children === "string" || typeof children === "number") {
    return (
      <Text numberOfLines={1} className={className}>
        {children}
      </Text>
    )
  }
  return children
}

function Header({
  scroll,
  className,
  children,
  ...props
}: ViewProps & {
  scroll?: HeaderScroll
}) {
  const leading: React.ReactNode[] = []
  const trailing: React.ReactNode[] = []
  const title: React.ReactNode[] = []

  for (const child of React.Children.toArray(children)) {
    if (React.isValidElement<{ side?: "leading" | "trailing" }>(child)) {
      if (child.type === HeaderTitle) {
        title.push(child)
        continue
      }
      if (
        child.type === HeaderBack ||
        (child.type === HeaderActions && child.props.side === "leading")
      ) {
        leading.push(child)
        continue
      }
    }
    trailing.push(child)
  }

  const scrollY = scroll?.scrollY

  const largeTitleHeight = scroll?.largeTitleHeight

  const borderStyle = useAnimatedStyle(() => {
    if (!scrollY || !largeTitleHeight) return { opacity: 0 }
    return {
      opacity: interpolate(
        scrollY.value - largeTitleHeight.value,
        [0, 8],
        [0, 1],
        "clamp"
      ),
    }
  })

  return (
    <HeaderContext.Provider value={scroll ?? null}>
      <View
        className={cn("h-11 flex-row items-center px-2", className)}
        {...props}
      >
        <View className="min-w-11 flex-1 basis-0 flex-row items-center justify-start">
          {leading}
        </View>
        {title}
        <View className="min-w-11 flex-1 basis-0 flex-row items-center justify-end">
          {trailing}
        </View>
        <AnimatedView
          className="absolute inset-x-0 bottom-0 h-px bg-separator"
          style={[{ pointerEvents: "none" }, borderStyle]}
        />
      </View>
    </HeaderContext.Provider>
  )
}

function HeaderTitle({
  subtitle,
  className,
  children,
  ...props
}: ViewProps & {
  subtitle?: React.ReactNode
}) {
  const scroll = React.useContext(HeaderContext)
  const scrollY = scroll?.scrollY
  const largeTitleHeight = scroll?.largeTitleHeight
  const animatedStyle = useAnimatedStyle(() => {
    if (!scrollY || !largeTitleHeight || largeTitleHeight.value <= 0)
      return { opacity: 1 }
    const height = largeTitleHeight.value
    return {
      opacity: interpolate(
        scrollY.value,
        [height * 0.6, height],
        [0, 1],
        "clamp"
      ),
    }
  })
  return (
    <AnimatedView
      role="heading"
      className={cn("shrink items-center px-2", className)}
      style={animatedStyle}
      {...props}
    >
      {wrapText(children, "text-base font-semibold")}
      {subtitle !== undefined
        ? wrapText(subtitle, "text-xs text-label-secondary")
        : null}
    </AnimatedView>
  )
}

function HeaderLargeTitle({
  subtitle,
  className,
  children,
  onLayout,
  ...props
}: ViewProps & {
  subtitle?: React.ReactNode
}) {
  const scroll = React.useContext(HeaderContext)
  const scrollY = scroll?.scrollY
  const largeTitleHeight = scroll?.largeTitleHeight

  React.useEffect(() => {
    if (!scroll) return
    return () => {
      scroll.largeTitleHeight.value = 0
    }
  }, [scroll])

  const animatedStyle = useAnimatedStyle(() => {
    if (!scrollY || !largeTitleHeight) return {}
    return {
      transform: [
        {
          scale: interpolate(scrollY.value, [-160, 0], [1.12, 1], "clamp"),
        },
      ],
    }
  })

  return (
    <AnimatedView
      className={cn("gap-0.5 px-4 pt-0.5 pb-2", className)}
      style={[
        { transformOrigin: I18nManager.isRTL ? "right" : "left" },
        animatedStyle,
      ]}
      onLayout={(event) => {
        if (scroll) {
          scroll.largeTitleHeight.value = event.nativeEvent.layout.height
        }
        onLayout?.(event)
      }}
      {...props}
    >
      {typeof children === "string" || typeof children === "number" ? (
        <Text role="heading" className="text-3xl font-bold">
          {children}
        </Text>
      ) : (
        children
      )}
      {subtitle !== undefined
        ? wrapText(subtitle, "text-sm text-label-secondary")
        : null}
    </AnimatedView>
  )
}

function HeaderBack({
  className,
  children,
  accessibilityLabel,
  ...props
}: Omit<React.ComponentProps<typeof Pressable>, "children"> & {
  children?: React.ReactNode
}) {
  return (
    <Pressable
      role="button"
      hitSlop={4}
      accessibilityLabel={
        accessibilityLabel ??
        (typeof children === "string" ? children : undefined) ??
        "Back"
      }
      className={cn(
        "h-9 shrink flex-row items-center gap-0.5 rounded-full ps-0.5 pe-3 active:bg-item-pressed",
        children === undefined && "pe-0.5",
        className
      )}
      {...props}
    >
      <Icon
        as={CaretLeftIcon}
        weight="bold"
        className={cn("size-6 text-link", I18nManager.isRTL && "rotate-180")}
      />
      {wrapText(children, "shrink text-base text-link")}
    </Pressable>
  )
}

function HeaderActions({
  side = "trailing",
  className,
  ...props
}: ViewProps & {
  side?: "leading" | "trailing"
}) {
  return (
    <View
      className={cn(
        "flex-row items-center gap-1",
        side === "leading" ? "justify-start" : "justify-end",
        className
      )}
      {...props}
    />
  )
}

function HeaderScrollView({
  scroll,
  className,
  scrollEventThrottle = 16,
  ...props
}: Omit<ScrollViewProps, "onScroll"> & {
  scroll: HeaderScroll
}) {
  return (
    <HeaderContext.Provider value={scroll}>
      <Animated.ScrollView
        onScroll={scroll.onScroll}
        scrollEventThrottle={scrollEventThrottle}
        className={cn("flex-1", className)}
        {...props}
      />
    </HeaderContext.Provider>
  )
}

export type { HeaderScroll }
export {
  Header,
  HeaderActions,
  HeaderBack,
  HeaderLargeTitle,
  HeaderScrollView,
  HeaderTitle,
  useHeaderScroll,
}
```

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).

3. Copy the source into `components/ui/header.tsx`:

```tsx title="nativewind/components/ui/header.tsx"
import { cn } from "cn"
import { CaretLeftIcon } from "phosphor-react-native"
import * as React from "react"
import {
  I18nManager,
  Pressable,
  type ScrollViewProps,
  View,
  type ViewProps,
} from "react-native"
import Animated, {
  interpolate,
  type SharedValue,
  useAnimatedScrollHandler,
  useAnimatedStyle,
  useSharedValue,
} from "react-native-reanimated"
import { AnimatedView } from "@/components/ui/animated-view"
import { Icon } from "@/components/ui/icon"
import { Text } from "@/components/ui/text"

type HeaderScroll = {
  scrollY: SharedValue<number>
  largeTitleHeight: SharedValue<number>
  onScroll: ReturnType<typeof useAnimatedScrollHandler>
}

const HeaderContext = React.createContext<HeaderScroll | null>(null)

function useHeaderScroll(): HeaderScroll {
  const scrollY = useSharedValue(0)
  const largeTitleHeight = useSharedValue(0)
  const onScroll = useAnimatedScrollHandler((event) => {
    scrollY.value = event.contentOffset.y
  })
  return React.useMemo(
    () => ({ scrollY, largeTitleHeight, onScroll }),
    [scrollY, largeTitleHeight, onScroll]
  )
}

function wrapText(children: React.ReactNode, className: string) {
  if (typeof children === "string" || typeof children === "number") {
    return (
      <Text numberOfLines={1} className={className}>
        {children}
      </Text>
    )
  }
  return children
}

function Header({
  scroll,
  className,
  children,
  ...props
}: ViewProps & {
  scroll?: HeaderScroll
}) {
  const leading: React.ReactNode[] = []
  const trailing: React.ReactNode[] = []
  const title: React.ReactNode[] = []

  for (const child of React.Children.toArray(children)) {
    if (React.isValidElement<{ side?: "leading" | "trailing" }>(child)) {
      if (child.type === HeaderTitle) {
        title.push(child)
        continue
      }
      if (
        child.type === HeaderBack ||
        (child.type === HeaderActions && child.props.side === "leading")
      ) {
        leading.push(child)
        continue
      }
    }
    trailing.push(child)
  }

  const scrollY = scroll?.scrollY

  const largeTitleHeight = scroll?.largeTitleHeight

  const borderStyle = useAnimatedStyle(() => {
    if (!scrollY || !largeTitleHeight) return { opacity: 0 }
    return {
      opacity: interpolate(
        scrollY.value - largeTitleHeight.value,
        [0, 8],
        [0, 1],
        "clamp"
      ),
    }
  })

  return (
    <HeaderContext.Provider value={scroll ?? null}>
      <View
        className={cn("h-11 flex-row items-center px-2", className)}
        {...props}
      >
        <View className="min-w-11 flex-1 basis-0 flex-row items-center justify-start">
          {leading}
        </View>
        {title}
        <View className="min-w-11 flex-1 basis-0 flex-row items-center justify-end">
          {trailing}
        </View>
        <AnimatedView
          className="absolute inset-x-0 bottom-0 h-px bg-separator"
          style={[{ pointerEvents: "none" }, borderStyle]}
        />
      </View>
    </HeaderContext.Provider>
  )
}

function HeaderTitle({
  subtitle,
  className,
  children,
  ...props
}: ViewProps & {
  subtitle?: React.ReactNode
}) {
  const scroll = React.useContext(HeaderContext)
  const scrollY = scroll?.scrollY
  const largeTitleHeight = scroll?.largeTitleHeight
  const animatedStyle = useAnimatedStyle(() => {
    if (!scrollY || !largeTitleHeight || largeTitleHeight.value <= 0)
      return { opacity: 1 }
    const height = largeTitleHeight.value
    return {
      opacity: interpolate(
        scrollY.value,
        [height * 0.6, height],
        [0, 1],
        "clamp"
      ),
    }
  })
  return (
    <AnimatedView
      role="heading"
      className={cn("shrink items-center px-2", className)}
      style={animatedStyle}
      {...props}
    >
      {wrapText(children, "text-base font-semibold")}
      {subtitle !== undefined
        ? wrapText(subtitle, "text-xs text-label-secondary")
        : null}
    </AnimatedView>
  )
}

function HeaderLargeTitle({
  subtitle,
  className,
  children,
  onLayout,
  ...props
}: ViewProps & {
  subtitle?: React.ReactNode
}) {
  const scroll = React.useContext(HeaderContext)
  const scrollY = scroll?.scrollY
  const largeTitleHeight = scroll?.largeTitleHeight

  React.useEffect(() => {
    if (!scroll) return
    return () => {
      scroll.largeTitleHeight.value = 0
    }
  }, [scroll])

  const animatedStyle = useAnimatedStyle(() => {
    if (!scrollY || !largeTitleHeight) return {}
    return {
      transform: [
        {
          scale: interpolate(scrollY.value, [-160, 0], [1.12, 1], "clamp"),
        },
      ],
    }
  })

  return (
    <AnimatedView
      className={cn("gap-0.5 px-4 pt-0.5 pb-2", className)}
      style={[
        { transformOrigin: I18nManager.isRTL ? "right" : "left" },
        animatedStyle,
      ]}
      onLayout={(event) => {
        if (scroll) {
          scroll.largeTitleHeight.value = event.nativeEvent.layout.height
        }
        onLayout?.(event)
      }}
      {...props}
    >
      {typeof children === "string" || typeof children === "number" ? (
        <Text role="heading" className="text-3xl font-bold">
          {children}
        </Text>
      ) : (
        children
      )}
      {subtitle !== undefined
        ? wrapText(subtitle, "text-sm text-label-secondary")
        : null}
    </AnimatedView>
  )
}

function HeaderBack({
  className,
  children,
  accessibilityLabel,
  ...props
}: Omit<React.ComponentProps<typeof Pressable>, "children"> & {
  children?: React.ReactNode
}) {
  return (
    <Pressable
      role="button"
      hitSlop={4}
      accessibilityLabel={
        accessibilityLabel ??
        (typeof children === "string" ? children : undefined) ??
        "Back"
      }
      className={cn(
        "h-9 shrink flex-row items-center gap-0.5 rounded-full ps-0.5 pe-3 active:bg-item-pressed",
        children === undefined && "pe-0.5",
        className
      )}
      {...props}
    >
      <Icon
        as={CaretLeftIcon}
        weight="bold"
        className={cn("size-6 text-link", I18nManager.isRTL && "rotate-180")}
      />
      {wrapText(children, "shrink text-base text-link")}
    </Pressable>
  )
}

function HeaderActions({
  side = "trailing",
  className,
  ...props
}: ViewProps & {
  side?: "leading" | "trailing"
}) {
  return (
    <View
      className={cn(
        "flex-row items-center gap-1",
        side === "leading" ? "justify-start" : "justify-end",
        className
      )}
      {...props}
    />
  )
}

function HeaderScrollView({
  scroll,
  className,
  scrollEventThrottle = 16,
  ...props
}: Omit<ScrollViewProps, "onScroll"> & {
  scroll: HeaderScroll
}) {
  return (
    <HeaderContext.Provider value={scroll}>
      <Animated.ScrollView
        onScroll={scroll.onScroll}
        scrollEventThrottle={scrollEventThrottle}
        className={cn("flex-1", className)}
        {...props}
      />
    </HeaderContext.Provider>
  )
}

export type { HeaderScroll }
export {
  Header,
  HeaderActions,
  HeaderBack,
  HeaderLargeTitle,
  HeaderScrollView,
  HeaderTitle,
  useHeaderScroll,
}
```

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).

3. Copy the source into `components/ui/header.tsx`:

```tsx title="stylesheet/components/ui/header.tsx"
import { CaretLeftIcon } from "phosphor-react-native"
import * as React from "react"
import {
  I18nManager,
  Pressable,
  type ScrollViewProps,
  type StyleProp,
  StyleSheet,
  type TextStyle,
  View,
  type ViewProps,
  type ViewStyle,
} from "react-native"
import Animated, {
  interpolate,
  type SharedValue,
  useAnimatedScrollHandler,
  useAnimatedStyle,
  useSharedValue,
} from "react-native-reanimated"
import { AnimatedView } from "@/components/ui/animated-view"
import { Icon } from "@/components/ui/icon"
import { Text } from "@/components/ui/text"
import { fontSize, radius, useTheme } from "@/components/ui/theme"

type HeaderScroll = {
  scrollY: SharedValue<number>
  largeTitleHeight: SharedValue<number>
  onScroll: ReturnType<typeof useAnimatedScrollHandler>
}

const HeaderContext = React.createContext<HeaderScroll | null>(null)

function useHeaderScroll(): HeaderScroll {
  const scrollY = useSharedValue(0)
  const largeTitleHeight = useSharedValue(0)
  const onScroll = useAnimatedScrollHandler((event) => {
    scrollY.value = event.contentOffset.y
  })
  return React.useMemo(
    () => ({ scrollY, largeTitleHeight, onScroll }),
    [scrollY, largeTitleHeight, onScroll]
  )
}

const styles = StyleSheet.create({
  bar: {
    height: 44,
    flexDirection: "row",
    alignItems: "center",
    paddingHorizontal: 8,
  },
  slot: {
    minWidth: 44,
    flex: 1,
    flexBasis: 0,
    flexDirection: "row",
    alignItems: "center",
  },
  border: {
    position: "absolute",
    left: 0,
    right: 0,
    bottom: 0,
    height: 1,
    pointerEvents: "none",
  },
  title: { flexShrink: 1, alignItems: "center", paddingHorizontal: 8 },
  titleText: { ...fontSize.base, fontWeight: "600" },
  subtitleText: { ...fontSize.xs },
  largeTitle: {
    gap: 2,
    paddingHorizontal: 16,
    paddingTop: 2,
    paddingBottom: 8,
  },
  largeTitleText: { ...fontSize["3xl"], fontWeight: "700" },
  largeSubtitleText: { ...fontSize.sm },
  back: {
    height: 36,
    flexShrink: 1,
    flexDirection: "row",
    alignItems: "center",
    gap: 2,
    borderRadius: radius.full,
    paddingStart: 2,
    paddingEnd: 12,
  },
  backIconOnly: { paddingEnd: 2 },
  backText: { ...fontSize.base, flexShrink: 1 },
  flipped: { transform: [{ rotate: "180deg" }] },
  actions: { flexDirection: "row", alignItems: "center", gap: 4 },
  scroll: { flex: 1 },
})

function wrapText(children: React.ReactNode, style: TextStyle) {
  if (typeof children === "string" || typeof children === "number") {
    return (
      <Text numberOfLines={1} style={style}>
        {children}
      </Text>
    )
  }
  return children
}

function Header({
  scroll,
  style,
  children,
  ...props
}: ViewProps & {
  scroll?: HeaderScroll
}) {
  const { colors } = useTheme()
  const leading: React.ReactNode[] = []
  const trailing: React.ReactNode[] = []
  const title: React.ReactNode[] = []

  for (const child of React.Children.toArray(children)) {
    if (React.isValidElement<{ side?: "leading" | "trailing" }>(child)) {
      if (child.type === HeaderTitle) {
        title.push(child)
        continue
      }
      if (
        child.type === HeaderBack ||
        (child.type === HeaderActions && child.props.side === "leading")
      ) {
        leading.push(child)
        continue
      }
    }
    trailing.push(child)
  }

  const scrollY = scroll?.scrollY

  const largeTitleHeight = scroll?.largeTitleHeight

  const borderStyle = useAnimatedStyle(() => {
    if (!scrollY || !largeTitleHeight) return { opacity: 0 }
    return {
      opacity: interpolate(
        scrollY.value - largeTitleHeight.value,
        [0, 8],
        [0, 1],
        "clamp"
      ),
    }
  })

  return (
    <HeaderContext.Provider value={scroll ?? null}>
      <View style={[styles.bar, style]} {...props}>
        <View style={[styles.slot, { justifyContent: "flex-start" }]}>
          {leading}
        </View>
        {title}
        <View style={[styles.slot, { justifyContent: "flex-end" }]}>
          {trailing}
        </View>
        <AnimatedView
          style={[
            styles.border,
            { backgroundColor: colors.separator },
            borderStyle,
          ]}
        />
      </View>
    </HeaderContext.Provider>
  )
}

function HeaderTitle({
  subtitle,
  style,
  children,
  ...props
}: ViewProps & {
  subtitle?: React.ReactNode
}) {
  const { colors } = useTheme()
  const scroll = React.useContext(HeaderContext)
  const scrollY = scroll?.scrollY
  const largeTitleHeight = scroll?.largeTitleHeight
  const animatedStyle = useAnimatedStyle(() => {
    if (!scrollY || !largeTitleHeight || largeTitleHeight.value <= 0)
      return { opacity: 1 }
    const height = largeTitleHeight.value
    return {
      opacity: interpolate(
        scrollY.value,
        [height * 0.6, height],
        [0, 1],
        "clamp"
      ),
    }
  })
  return (
    <AnimatedView
      role="heading"
      style={[styles.title, animatedStyle, style]}
      {...props}
    >
      {wrapText(children, styles.titleText)}
      {subtitle !== undefined
        ? wrapText(subtitle, {
            ...styles.subtitleText,
            color: colors.labelSecondary,
          })
        : null}
    </AnimatedView>
  )
}

function HeaderLargeTitle({
  subtitle,
  style,
  children,
  onLayout,
  ...props
}: ViewProps & {
  subtitle?: React.ReactNode
}) {
  const { colors } = useTheme()
  const scroll = React.useContext(HeaderContext)
  const scrollY = scroll?.scrollY
  const largeTitleHeight = scroll?.largeTitleHeight

  React.useEffect(() => {
    if (!scroll) return
    return () => {
      scroll.largeTitleHeight.value = 0
    }
  }, [scroll])

  const animatedStyle = useAnimatedStyle(() => {
    if (!scrollY || !largeTitleHeight) return {}
    return {
      transform: [
        {
          scale: interpolate(scrollY.value, [-160, 0], [1.12, 1], "clamp"),
        },
      ],
    }
  })

  return (
    <AnimatedView
      style={[
        styles.largeTitle,
        { transformOrigin: I18nManager.isRTL ? "right" : "left" },
        animatedStyle,
        style,
      ]}
      onLayout={(event) => {
        if (scroll) {
          scroll.largeTitleHeight.value = event.nativeEvent.layout.height
        }
        onLayout?.(event)
      }}
      {...props}
    >
      {typeof children === "string" || typeof children === "number" ? (
        <Text role="heading" style={styles.largeTitleText}>
          {children}
        </Text>
      ) : (
        children
      )}
      {subtitle !== undefined
        ? wrapText(subtitle, {
            ...styles.largeSubtitleText,
            color: colors.labelSecondary,
          })
        : null}
    </AnimatedView>
  )
}

function HeaderBack({
  style,
  children,
  accessibilityLabel,
  ...props
}: Omit<React.ComponentProps<typeof Pressable>, "children" | "style"> & {
  children?: React.ReactNode
  style?: StyleProp<ViewStyle>
}) {
  const { colors } = useTheme()
  return (
    <Pressable
      role="button"
      hitSlop={4}
      accessibilityLabel={
        accessibilityLabel ??
        (typeof children === "string" ? children : undefined) ??
        "Back"
      }
      style={({ pressed }) => [
        styles.back,
        children === undefined && styles.backIconOnly,
        pressed && { backgroundColor: colors.itemPressed },
        style,
      ]}
      {...props}
    >
      <Icon
        as={CaretLeftIcon}
        weight="bold"
        size={24}
        color={colors.link}
        style={I18nManager.isRTL ? styles.flipped : undefined}
      />
      {wrapText(children, { ...styles.backText, color: colors.link })}
    </Pressable>
  )
}

function HeaderActions({
  side = "trailing",
  style,
  ...props
}: ViewProps & {
  side?: "leading" | "trailing"
}) {
  return (
    <View
      style={[
        styles.actions,
        { justifyContent: side === "leading" ? "flex-start" : "flex-end" },
        style,
      ]}
      {...props}
    />
  )
}

function HeaderScrollView({
  scroll,
  style,
  scrollEventThrottle = 16,
  ...props
}: Omit<ScrollViewProps, "onScroll"> & {
  scroll: HeaderScroll
}) {
  return (
    <HeaderContext.Provider value={scroll}>
      <Animated.ScrollView
        onScroll={scroll.onScroll}
        scrollEventThrottle={scrollEventThrottle}
        style={[styles.scroll, style]}
        {...props}
      />
    </HeaderContext.Provider>
  )
}

export type { HeaderScroll }
export {
  Header,
  HeaderActions,
  HeaderBack,
  HeaderLargeTitle,
  HeaderScrollView,
  HeaderTitle,
  useHeaderScroll,
}
```

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/Components/Header.swift"
import PhosphorSwift
import SwiftUI

extension EnvironmentValues {
  @Entry var headerProgress: CGFloat?
  @Entry var headerReport: ((CGFloat) -> Void)?
}

enum HeaderMath {
  static func progress(minY: CGFloat, height: CGFloat) -> CGFloat {
    guard height > 0 else { return 0 }
    return min(max(-minY / height, 0), 1)
  }
}

public struct Header<Title: View, Leading: View, Trailing: View>: View {
  let title: Title
  let leading: Leading
  let trailing: Trailing

  @Environment(\.headerProgress) private var progress
  @Environment(\.screenBackground) private var background

  public init(
    @ViewBuilder title: () -> Title,
    @ViewBuilder leading: () -> Leading,
    @ViewBuilder trailing: () -> Trailing
  ) {
    self.title = title()
    self.leading = leading()
    self.trailing = trailing()
  }

  public var body: some View {
    HeaderLayout {
      HStack(spacing: 0) { leading }
        .frame(maxHeight: .infinity)
      ZStack { title }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
      HStack(spacing: 0) { trailing }
        .frame(maxHeight: .infinity)
    }
    .padding(.horizontal, 8)
    .frame(height: 44)
    .frame(maxWidth: .infinity)
    .background(background.ignoresSafeArea(.container, edges: .top))
    .overlay(alignment: .bottom) {
      Color.separator
        .frame(height: 1)
        .opacity(progress ?? 0)
    }
    .accessibilityElement(children: .contain)
    .accessibilityAddTraits(.isHeader)
  }
}

extension Header where Leading == EmptyView {
  public init(@ViewBuilder title: () -> Title, @ViewBuilder trailing: () -> Trailing) {
    self.init(title: title, leading: { EmptyView() }, trailing: trailing)
  }
}

extension Header where Trailing == EmptyView {
  public init(@ViewBuilder title: () -> Title, @ViewBuilder leading: () -> Leading) {
    self.init(title: title, leading: leading, trailing: { EmptyView() })
  }
}

extension Header where Leading == EmptyView, Trailing == EmptyView {
  public init(@ViewBuilder title: () -> Title) {
    self.init(title: title, leading: { EmptyView() }, trailing: { EmptyView() })
  }
}

struct HeaderLayout: Layout {
  var spacing: CGFloat = 8
  var minSide: CGFloat = 44

  func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
    let ideal = subviews.reduce(0) { $0 + $1.sizeThatFits(.unspecified).width }
    return CGSize(width: proposal.width ?? ideal, height: proposal.height ?? 44)
  }

  func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) {
    guard subviews.count == 3 else { return }
    let leading = subviews[0]
    let title = subviews[1]
    let trailing = subviews[2]
    let trailingWidth = trailing.sizeThatFits(.unspecified).width
    let leadingIdeal = leading.sizeThatFits(.unspecified).width
    let leadingMinimum = leading.sizeThatFits(ProposedViewSize(width: 0, height: nil)).width
    let reserve = max(minSide, trailingWidth, leadingMinimum) + spacing
    let titleWidth = max(0, min(title.sizeThatFits(.unspecified).width, bounds.width - reserve * 2))
    let side = max(0, (bounds.width - titleWidth) / 2 - spacing)
    let leadingProposal = ProposedViewSize(width: min(side, leadingIdeal), height: nil)
    let leadingWidth = leading.sizeThatFits(leadingProposal).width
    let titleInset = max(leadingWidth, trailingWidth) + spacing
    leading.place(
      at: CGPoint(x: bounds.minX, y: bounds.minY),
      anchor: .topLeading,
      proposal: ProposedViewSize(width: leadingProposal.width, height: bounds.height)
    )
    title.place(
      at: CGPoint(x: bounds.minX + titleInset, y: bounds.minY),
      anchor: .topLeading,
      proposal: ProposedViewSize(width: max(0, bounds.width - titleInset * 2), height: bounds.height)
    )
    trailing.place(
      at: CGPoint(x: bounds.maxX - trailingWidth, y: bounds.minY),
      anchor: .topLeading,
      proposal: ProposedViewSize(width: trailingWidth, height: bounds.height)
    )
  }
}

public struct HeaderTitle: View {
  let title: Text
  let subtitle: Text?

  @Environment(\.headerProgress) private var progress

  public init(_ title: LocalizedStringKey, subtitle: LocalizedStringKey? = nil) {
    self.title = Text(title)
    self.subtitle = subtitle.map { Text($0) }
  }

  public init(verbatim title: String, subtitle: String? = nil) {
    self.title = Text(verbatim: title)
    self.subtitle = subtitle.map { Text(verbatim: $0) }
  }

  public var body: some View {
    VStack(spacing: 0) {
      title
        .scaledFont(.base, weight: .semibold)
        .foregroundStyle(Color.label)
      if let subtitle {
        subtitle
          .scaledFont(.xs2)
          .foregroundStyle(Color.labelSecondary)
      }
    }
    .lineLimit(1)
    .multilineTextAlignment(.center)
    .opacity(progress ?? 1)
    .accessibilityElement(children: .combine)
    .accessibilityHidden((progress ?? 1) < 0.5)
  }
}

public struct HeaderLargeTitle: View {
  let title: Text
  let subtitle: Text?

  @Environment(\.headerReport) private var report

  public init(_ title: LocalizedStringKey, subtitle: LocalizedStringKey? = nil) {
    self.title = Text(title)
    self.subtitle = subtitle.map { Text($0) }
  }

  public init(verbatim title: String, subtitle: String? = nil) {
    self.title = Text(verbatim: title)
    self.subtitle = subtitle.map { Text(verbatim: $0) }
  }

  public var body: some View {
    VStack(alignment: .leading, spacing: 2) {
      title
        .scaledFont(.xl3, weight: .bold)
        .foregroundStyle(Color.label)
        .accessibilityAddTraits(.isHeader)
      if let subtitle {
        subtitle
          .scaledFont(.sm)
          .foregroundStyle(Color.labelSecondary)
      }
    }
    .lineLimit(2)
    .padding(.horizontal, 16)
    .padding(.top, 4)
    .padding(.bottom, 8)
    .frame(maxWidth: .infinity, alignment: .leading)
    .onGeometryChange(for: CGFloat.self) { proxy in
      HeaderMath.progress(minY: proxy.frame(in: .scrollView).minY, height: proxy.size.height)
    } action: { value in
      report?(value)
    }
  }
}

public struct HeaderBack: View {
  let label: Text?
  let action: (() -> Void)?

  @Environment(\.dismiss) private var dismiss
  @Environment(\.isEnabled) private var isEnabled

  public init(_ label: LocalizedStringKey? = nil, action: (() -> Void)? = nil) {
    self.label = label.map { Text($0) }
    self.action = action
  }

  public init(verbatim label: String, action: (() -> Void)? = nil) {
    self.label = Text(verbatim: label)
    self.action = action
  }

  public var body: some View {
    Button {
      if let action {
        action()
      } else {
        dismiss()
      }
    } label: {
      EmptyView()
    }
    .buttonStyle(PressReader { pressed in
      HStack(spacing: 2) {
        Ph.caretLeft.bold
          .frame(width: 20, height: 20)
          .flipsForRightToLeftLayoutDirection(true)
        if let label {
          label
            .scaledFont(.base)
            .lineLimit(1)
        }
      }
      .foregroundStyle(!isEnabled ? Color.labelQuaternary : pressed ? .link.opacity(0.4) : .link)
      .padding(.horizontal, 4)
      .frame(minWidth: 44, minHeight: 44, alignment: .leading)
      .contentShape(Rectangle())
    })
    .accessibilityLabel(label ?? Text("Back"))
  }
}

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

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

  public var body: some View {
    HStack(spacing: 4) {
      content
    }
    .buttonStyle(.variant(.ghost, size: .icon))
  }
}

public struct HeaderScrollView<HeaderContent: View, Content: View>: View {
  let header: HeaderContent
  let content: Content

  @State private var progress: CGFloat?

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

  public var body: some View {
    VStack(spacing: 0) {
      header
        .environment(\.headerProgress, progress)
        .zIndex(1)
      KeyboardScrollView {
        VStack(alignment: .leading, spacing: 0) {
          content
        }
      }
      .environment(\.headerReport) { value in
        if progress != value { progress = value }
      }
    }
  }
}
```

```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/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/KeyboardScrollView.swift"
import SwiftUI
import UIKit

public struct KeyboardScrollView<Content: View>: View {
  let showsIndicators: Bool
  let content: Content

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

  public var body: some View {
    ScrollView(.vertical, showsIndicators: showsIndicators) {
      content
        .frame(maxWidth: .infinity, alignment: .topLeading)
        .background {
          Color.clear
            .contentShape(Rectangle())
            .onTapGesture { KeyboardScrollView.dismissKeyboard() }
        }
    }
    .scrollDismissesKeyboard(.interactively)
  }

  @MainActor
  static func dismissKeyboard() {
    UIApplication.shared.sendAction(#selector(UIResponder.resignFirstResponder), to: nil, from: nil, for: nil)
  }
}
```

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

extension EnvironmentValues {
  @Entry var screenBackground: Color = .surface
}

public struct Screen<Content: View>: View {
  public enum Background: CaseIterable, Sendable {
    case surface, surfaceSecondary

    var color: Color {
      switch self {
      case .surface: .surface
      case .surfaceSecondary: .surfaceSecondary
      }
    }
  }

  let edges: Edge.Set
  let background: Background
  let content: Content

  public init(
    edges: Edge.Set = .all,
    background: Background = .surface,
    @ViewBuilder content: () -> Content
  ) {
    self.edges = edges
    self.background = background
    self.content = content()
  }

  public var body: some View {
    VStack(spacing: 0) {
      content
    }
    .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .top)
    .ignoresSafeArea(.container, edges: Edge.Set.all.subtracting(edges))
    .foregroundStyle(Color.label)
    .background(background.color.ignoresSafeArea())
    .environment(\.screenBackground, background.color)
  }
}

public struct ScreenContent<Content: View>: View {
  let scroll: Bool
  let padded: Bool
  let content: Content

  public init(scroll: Bool = true, padded: Bool = true, @ViewBuilder content: () -> Content) {
    self.scroll = scroll
    self.padded = padded
    self.content = content()
  }

  public var body: some View {
    if scroll {
      KeyboardScrollView {
        stack
      }
    } else {
      stack
        .frame(maxHeight: .infinity, alignment: .top)
    }
  }

  private var stack: some View {
    VStack(alignment: .leading, spacing: 16) {
      content
    }
    .padding(padded ? 16 : 0)
    .frame(maxWidth: .infinity, alignment: .leading)
  }
}
```

```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/components/Header.kt"
package com.esuiss.ui.components

import androidx.compose.animation.core.animate
import androidx.compose.animation.core.animateFloatAsState
import androidx.compose.animation.core.tween
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.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.RowScope
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.text.BasicText
import androidx.compose.runtime.Composable
import androidx.compose.runtime.CompositionLocalProvider
import androidx.compose.runtime.Stable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableFloatStateOf
import androidx.compose.runtime.remember
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.clipToBounds
import androidx.compose.ui.draw.drawWithContent
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.graphicsLayer
import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
import androidx.compose.ui.input.nestedscroll.NestedScrollSource
import androidx.compose.ui.layout.Layout
import androidx.compose.ui.layout.layoutId
import androidx.compose.ui.semantics.Role
import androidx.compose.ui.semantics.heading
import androidx.compose.ui.semantics.semantics
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.text.style.TextOverflow
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.unit.Velocity
import androidx.compose.ui.unit.dp
import com.adamglin.PhosphorIcons
import com.adamglin.phosphoricons.Regular
import com.adamglin.phosphoricons.regular.CaretLeft
import com.esuiss.ui.theme.EsuissTheme
import com.esuiss.ui.theme.Typography

private val HeaderBarHeight = 44.dp

private enum class HeaderSlot { Back, Start, End, Title, LargeTitle }

enum class HeaderActionsSide { Leading, Trailing }

@Stable
class HeaderState {
    internal var range by mutableFloatStateOf(0f)
    internal var offset by mutableFloatStateOf(0f)

    val collapsedFraction: Float
        get() = if (range <= 0f) 1f else (offset / range).coerceIn(0f, 1f)

    val nestedScrollConnection: NestedScrollConnection = object : NestedScrollConnection {
        override fun onPreScroll(available: Offset, source: NestedScrollSource): Offset {
            if (available.y >= 0f || range <= 0f) return Offset.Zero
            val next = (offset - available.y).coerceAtMost(range)
            val used = next - offset
            offset = next
            return Offset(0f, -used)
        }

        override fun onPostScroll(consumed: Offset, available: Offset, source: NestedScrollSource): Offset {
            if (available.y <= 0f || range <= 0f) return Offset.Zero
            val next = (offset - available.y).coerceAtLeast(0f)
            val used = offset - next
            offset = next
            return Offset(0f, used)
        }

        override suspend fun onPostFling(consumed: Velocity, available: Velocity): Velocity {
            settle()
            return Velocity.Zero
        }
    }

    internal suspend fun settle() {
        if (range <= 0f || offset <= 0f || offset >= range) return
        val target = if (offset < range / 2f) 0f else range
        animate(offset, target, animationSpec = tween(250)) { value, _ -> offset = value }
    }
}

@Composable
fun rememberHeaderState(): HeaderState = remember { HeaderState() }

private val LocalHeaderState = staticCompositionLocalOf<HeaderState?> { null }

@Composable
fun Header(
    modifier: Modifier = Modifier,
    state: HeaderState = rememberHeaderState(),
    content: @Composable () -> Unit,
) {
    val colors = EsuissTheme.colors
    val collapsed = state.range > 0f && state.offset >= state.range
    val separator by animateFloatAsState(if (state.range <= 0f || collapsed) 1f else 0f, tween(150), label = "separator")
    CompositionLocalProvider(LocalHeaderState provides state) {
        Layout(
            content = content,
            modifier = modifier
                .clipToBounds()
                .drawWithContent {
                    drawContent()
                    val stroke = 1.dp.toPx()
                    drawRect(colors.separator.copy(alpha = colors.separator.alpha * separator), Offset(0f, size.height - stroke), Size(size.width, stroke))
                },
        ) { measurables, constraints ->
            val width = constraints.maxWidth
            val bar = HeaderBarHeight.roundToPx()
            val inset = 8.dp.roundToPx()
            val loose = Constraints(maxWidth = width, maxHeight = bar)
            val back = measurables.firstOrNull { it.layoutId == HeaderSlot.Back }?.measure(loose)
            val start = measurables.firstOrNull { it.layoutId == HeaderSlot.Start }?.measure(loose)
            val end = measurables.firstOrNull { it.layoutId == HeaderSlot.End }?.measure(loose)
            val leading = (back?.width ?: 0) + (start?.width ?: 0)
            val side = maxOf(leading, end?.width ?: 0) + inset
            val titleWidth = (width - side * 2).coerceAtLeast(0)
            val title = measurables.firstOrNull { it.layoutId == HeaderSlot.Title }
                ?.measure(Constraints(maxWidth = titleWidth, maxHeight = bar))
            val large = measurables.firstOrNull { it.layoutId == HeaderSlot.LargeTitle }
                ?.measure(Constraints(minWidth = width, maxWidth = width))
            val range = (large?.height ?: 0).toFloat()
            if (state.range != range) state.range = range
            val offset = state.offset.coerceIn(0f, range).toInt()
            val height = bar + (large?.height ?: 0) - offset
            layout(width, height) {
                var x = inset
                back?.let {
                    it.placeRelative(x, (bar - it.height) / 2)
                    x += it.width
                }
                start?.placeRelative(x, (bar - (start.height)) / 2)
                end?.let { it.placeRelative(width - inset - it.width, (bar - it.height) / 2) }
                title?.placeRelative((width - title.width) / 2, (bar - title.height) / 2)
                large?.placeRelative(0, bar - offset)
            }
        }
    }
}

@Composable
fun HeaderTitle(
    text: String,
    modifier: Modifier = Modifier,
    subtitle: String? = null,
) {
    val colors = EsuissTheme.colors
    val state = LocalHeaderState.current
    Column(
        modifier = modifier
            .layoutId(HeaderSlot.Title)
            .graphicsLayer {
                val fraction = state?.collapsedFraction ?: 1f
                alpha = if (state == null || state.range <= 0f) 1f else ((fraction - 0.6f) / 0.4f).coerceIn(0f, 1f)
            }
            .semantics { heading() },
        horizontalAlignment = Alignment.CenterHorizontally,
    ) {
        BasicText(
            text,
            style = Typography.base.copy(color = colors.label, fontWeight = FontWeight.SemiBold, textAlign = TextAlign.Center),
            maxLines = 1,
            overflow = TextOverflow.Ellipsis,
        )
        if (subtitle != null) {
            BasicText(
                subtitle,
                style = Typography.xs2.copy(color = colors.labelSecondary, textAlign = TextAlign.Center),
                maxLines = 1,
                overflow = TextOverflow.Ellipsis,
            )
        }
    }
}

@Composable
fun HeaderLargeTitle(
    text: String,
    modifier: Modifier = Modifier,
    subtitle: String? = null,
) {
    val colors = EsuissTheme.colors
    val state = LocalHeaderState.current
    Column(
        modifier = modifier
            .layoutId(HeaderSlot.LargeTitle)
            .graphicsLayer {
                val fraction = state?.collapsedFraction ?: 0f
                alpha = (1f - fraction * 1.4f).coerceIn(0f, 1f)
            }
            .padding(start = 16.dp, end = 16.dp, top = 4.dp, bottom = 8.dp),
        verticalArrangement = Arrangement.spacedBy(2.dp),
    ) {
        BasicText(
            text,
            modifier = Modifier.semantics { heading() },
            style = Typography.xl3.copy(color = colors.label, fontWeight = FontWeight.Bold),
            maxLines = 2,
            overflow = TextOverflow.Ellipsis,
        )
        if (subtitle != null) {
            BasicText(subtitle, style = Typography.sm.copy(color = colors.labelSecondary))
        }
    }
}

@Composable
fun HeaderBack(
    onClick: () -> Unit,
    modifier: Modifier = Modifier,
    text: String? = "Back",
    contentDescription: String = text ?: "Back",
) {
    val colors = EsuissTheme.colors
    val interaction = remember { MutableInteractionSource() }
    val pressed by interaction.collectIsPressedAsState()
    Row(
        modifier = modifier
            .layoutId(HeaderSlot.Back)
            .height(HeaderBarHeight)
            .clickable(
                interactionSource = interaction,
                indication = null,
                role = Role.Button,
                onClickLabel = contentDescription,
                onClick = onClick,
            )
            .graphicsLayer { alpha = if (pressed) 0.4f else 1f }
            .padding(end = 8.dp),
        horizontalArrangement = Arrangement.spacedBy(2.dp),
        verticalAlignment = Alignment.CenterVertically,
    ) {
        Icon(PhosphorIcons.Regular.CaretLeft, contentDescription = if (text == null) contentDescription else null, size = 24.dp, tint = colors.link)
        if (text != null) {
            BasicText(text, style = Typography.base.copy(color = colors.link), maxLines = 1)
        }
    }
}

@Composable
fun HeaderActions(
    modifier: Modifier = Modifier,
    side: HeaderActionsSide = HeaderActionsSide.Trailing,
    content: @Composable RowScope.() -> Unit,
) {
    Row(
        modifier = modifier.layoutId(if (side == HeaderActionsSide.Leading) HeaderSlot.Start else HeaderSlot.End),
        horizontalArrangement = Arrangement.spacedBy(4.dp),
        verticalAlignment = Alignment.CenterVertically,
        content = content,
    )
}
```

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

import androidx.compose.foundation.background
import androidx.compose.foundation.border
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.Row
import androidx.compose.foundation.layout.RowScope
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.shape.CircleShape
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.foundation.text.BasicText
import androidx.compose.runtime.Composable
import androidx.compose.runtime.CompositionLocalProvider
import androidx.compose.runtime.getValue
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.clip
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.semantics.Role
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.style.TextDecoration
import androidx.compose.ui.unit.Dp
import androidx.compose.ui.unit.dp
import com.esuiss.ui.theme.Colors
import com.esuiss.ui.theme.EsuissTheme
import com.esuiss.ui.theme.Radius
import com.esuiss.ui.theme.Typography

enum class ButtonVariant { Default, Outline, Secondary, Tinted, Ghost, Plain, Destructive, Link }

enum class ButtonSize(
    val height: Dp,
    val horizontalPadding: Dp,
    val spacing: Dp,
    val iconSize: Dp,
    val blockRadius: Dp,
    val isIcon: Boolean,
) {
    Default(36.dp, 16.dp, 6.dp, 16.dp, Radius.md, false),
    Xs(24.dp, 11.dp, 4.dp, 12.dp, Radius.sm, false),
    Sm(32.dp, 12.dp, 4.dp, 16.dp, Radius.md, false),
    Lg(44.dp, 22.dp, 6.dp, 16.dp, Radius.lg, false),
    Xl(56.dp, 31.dp, 8.dp, 16.dp, Radius.xl, false),
    Icon(36.dp, 0.dp, 6.dp, 16.dp, Radius.md, true),
    IconXs(24.dp, 0.dp, 4.dp, 12.dp, Radius.sm, true),
    IconSm(32.dp, 0.dp, 4.dp, 16.dp, Radius.md, true),
    IconLg(44.dp, 0.dp, 6.dp, 16.dp, Radius.lg, true),
    IconXl(56.dp, 0.dp, 8.dp, 16.dp, Radius.xl, true),
    ;

    val textStyle: TextStyle
        get() = when (this) {
            Xs, IconXs -> Typography.xs2
            Lg, Xl -> Typography.base
            else -> Typography.sm
        }
}

@Composable
fun Button(
    onClick: () -> Unit,
    modifier: Modifier = Modifier,
    variant: ButtonVariant = ButtonVariant.Default,
    size: ButtonSize = ButtonSize.Default,
    block: Boolean = false,
    enabled: Boolean = true,
    content: @Composable RowScope.() -> Unit,
) {
    val colors = EsuissTheme.colors
    val interaction = remember { MutableInteractionSource() }
    val pressed by interaction.collectIsPressedAsState()
    val foreground = buttonForeground(variant, colors, enabled)
    val group = LocalButtonGroup.current?.takeIf { variant != ButtonVariant.Ghost && variant != ButtonVariant.Plain }
    RegisterButtonGroupOutline(group, variant == ButtonVariant.Outline)
    val shape = group.itemShape(if (block) RoundedCornerShape(size.blockRadius) else CircleShape)
    val sizing = when {
        block -> Modifier.fillMaxWidth().height(size.height)
        size.isIcon -> Modifier.size(size.height)
        else -> Modifier.height(size.height)
    }

    Row(
        modifier = modifier
            .then(sizing)
            .clip(shape)
            .background(buttonBackground(variant, colors, pressed && enabled, enabled), shape)
            .then(
                when {
                    variant != ButtonVariant.Outline -> Modifier
                    group != null -> Modifier.buttonGroupEdge(group, colors.separator)
                    else -> Modifier.border(1.dp, colors.separator, shape)
                },
            )
            .clickable(
                interactionSource = interaction,
                indication = null,
                enabled = enabled,
                role = Role.Button,
                onClick = onClick,
            )
            .padding(horizontal = size.horizontalPadding),
        horizontalArrangement = Arrangement.spacedBy(size.spacing, Alignment.CenterHorizontally),
        verticalAlignment = Alignment.CenterVertically,
    ) {
        CompositionLocalProvider(
            LocalButtonGroup provides null,
            LocalContentStyle provides size.textStyle.copy(
                color = foreground,
                textDecoration = if (variant == ButtonVariant.Link && pressed && enabled) {
                    TextDecoration.Underline
                } else {
                    null
                },
            ),
            LocalContentColor provides foreground,
            LocalIconSize provides size.iconSize,
        ) {
            content()
        }
    }
}

@Composable
fun Button(
    text: String,
    onClick: () -> Unit,
    modifier: Modifier = Modifier,
    variant: ButtonVariant = ButtonVariant.Default,
    size: ButtonSize = ButtonSize.Default,
    block: Boolean = false,
    enabled: Boolean = true,
) {
    Button(onClick, modifier, variant, size, block, enabled) {
        BasicText(text, style = LocalContentStyle.current, maxLines = 1)
    }
}

private fun buttonForeground(variant: ButtonVariant, colors: Colors, enabled: Boolean): Color =
    when (variant) {
        ButtonVariant.Default -> colors.onAccent
        ButtonVariant.Outline, ButtonVariant.Secondary, ButtonVariant.Ghost ->
            if (enabled) colors.label else colors.labelQuaternary
        ButtonVariant.Tinted, ButtonVariant.Plain ->
            if (enabled) colors.link else colors.link.copy(alpha = 0.4f)
        ButtonVariant.Destructive ->
            if (enabled) colors.danger else colors.danger.copy(alpha = 0.4f)
        ButtonVariant.Link -> if (enabled) colors.link else colors.labelQuaternary
    }

private fun buttonBackground(variant: ButtonVariant, colors: Colors, pressed: Boolean, enabled: Boolean): Color =
    when (variant) {
        ButtonVariant.Default -> when {
            !enabled -> colors.accentDisabled
            pressed -> colors.accentPressed
            else -> colors.accent
        }
        ButtonVariant.Outline -> when {
            pressed -> colors.itemPressed
            colors.isDark -> Color.Transparent
            else -> colors.surface
        }
        ButtonVariant.Secondary -> when {
            !enabled -> colors.controlDisabled
            pressed -> colors.controlPressed
            else -> colors.control
        }
        ButtonVariant.Tinted -> if (pressed) colors.accentSurfacePressed else colors.accentSurface
        ButtonVariant.Ghost -> if (pressed) colors.itemPressed else Color.Transparent
        ButtonVariant.Plain -> if (pressed) colors.itemPressed else Color.Transparent
        ButtonVariant.Destructive -> if (pressed) colors.dangerSurfacePressed else colors.dangerSurface
        ButtonVariant.Link -> Color.Transparent
    }
```

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

import androidx.compose.foundation.background
import androidx.compose.foundation.gestures.Orientation
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.RowScope
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.shape.CircleShape
import androidx.compose.foundation.shape.CornerSize
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.runtime.Composable
import androidx.compose.runtime.CompositionLocalProvider
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.Immutable
import androidx.compose.runtime.Stable
import androidx.compose.runtime.compositionLocalOf
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableIntStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
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.draw.drawWithContent
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.RectangleShape
import androidx.compose.ui.graphics.Shape
import androidx.compose.ui.graphics.drawOutline
import androidx.compose.ui.graphics.drawscope.Stroke
import androidx.compose.ui.graphics.drawscope.translate
import androidx.compose.ui.graphics.takeOrElse
import androidx.compose.ui.layout.Layout
import androidx.compose.ui.layout.Placeable
import androidx.compose.ui.layout.layout
import androidx.compose.ui.layout.layoutId
import androidx.compose.ui.layout.onPlaced
import androidx.compose.ui.platform.LocalLayoutDirection
import androidx.compose.ui.semantics.isTraversalGroup
import androidx.compose.ui.semantics.semantics
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.unit.LayoutDirection
import androidx.compose.ui.unit.constrainHeight
import androidx.compose.ui.unit.constrainWidth
import androidx.compose.ui.unit.dp
import com.esuiss.ui.theme.EsuissTheme
import com.esuiss.ui.theme.Radius
import com.esuiss.ui.theme.Typography

enum class ButtonGroupOrientation { Horizontal, Vertical }

@Stable
internal class ButtonGroupState(val orientation: ButtonGroupOrientation) {
    var nested by mutableIntStateOf(0)
    var outlined by mutableIntStateOf(0)
}

internal val LocalButtonGroup = compositionLocalOf<ButtonGroupState?> { null }

internal object ButtonGroupFill

private object ButtonGroupDivider

internal fun ButtonGroupState?.itemShape(default: Shape): Shape = if (this == null) default else RectangleShape

@Immutable
internal class ButtonGroupItem(val shape: Shape, val modifier: Modifier)

@Composable
internal fun rememberButtonGroupItem(group: ButtonGroupState?, default: Shape): ButtonGroupItem {
    var edges by remember { mutableIntStateOf(0) }
    val horizontal = group?.orientation != ButtonGroupOrientation.Vertical
    val rtl = LocalLayoutDirection.current == LayoutDirection.Rtl
    val shape = remember(edges, horizontal) {
        val round = if (horizontal) CornerSize(50) else CornerSize(Radius.xl2)
        val square = CornerSize(0)
        val start = if (edges and 1 != 0) round else square
        val end = if (edges and 2 != 0) round else square
        if (horizontal) {
            RoundedCornerShape(topStart = start, topEnd = end, bottomEnd = end, bottomStart = start)
        } else {
            RoundedCornerShape(topStart = start, topEnd = start, bottomEnd = end, bottomStart = end)
        }
    }
    if (group == null || group.nested > 0) return ButtonGroupItem(default, Modifier)
    return ButtonGroupItem(
        shape = shape,
        modifier = Modifier.onPlaced { coordinates ->
            val parent = coordinates.parentLayoutCoordinates ?: return@onPlaced
            val bounds = parent.localBoundingBoxOf(coordinates, clipBounds = false)
            val first: Boolean
            val last: Boolean
            if (horizontal) {
                val left = bounds.left <= 0.5f
                val right = bounds.right >= parent.size.width - 0.5f
                first = if (rtl) right else left
                last = if (rtl) left else right
            } else {
                first = bounds.top <= 0.5f
                last = bounds.bottom >= parent.size.height - 0.5f
            }
            edges = (if (first) 1 else 0) or (if (last) 2 else 0)
        },
    )
}

internal fun Modifier.buttonGroupEdge(group: ButtonGroupState?, color: Color): Modifier {
    if (group == null) return this
    return drawBehind {
        val stroke = 1.dp.toPx()
        if (group.orientation == ButtonGroupOrientation.Horizontal) {
            val x = if (layoutDirection == LayoutDirection.Rtl) 0f else size.width - stroke
            drawRect(color, Offset(x, 0f), Size(stroke, size.height))
        } else {
            drawRect(color, Offset(0f, size.height - stroke), Size(size.width, stroke))
        }
    }
}

@Composable
internal fun RegisterButtonGroupOutline(group: ButtonGroupState?, outlined: Boolean) {
    DisposableEffect(group, outlined) {
        if (group != null && outlined) group.outlined += 1
        onDispose {
            if (group != null && outlined) group.outlined -= 1
        }
    }
}

@Composable
fun ButtonGroup(
    modifier: Modifier = Modifier,
    orientation: ButtonGroupOrientation = ButtonGroupOrientation.Horizontal,
    content: @Composable () -> Unit,
) {
    val parent = LocalButtonGroup.current
    DisposableEffect(parent) {
        parent?.let { it.nested += 1 }
        onDispose { parent?.let { it.nested -= 1 } }
    }
    val state = remember(orientation) { ButtonGroupState(orientation) }
    val colors = EsuissTheme.colors
    val joined = state.nested == 0
    val horizontal = orientation == ButtonGroupOrientation.Horizontal
    val shape = if (horizontal) CircleShape else RoundedCornerShape(Radius.xl2)
    val outline = colors.separator
    Layout(
        content = {
            CompositionLocalProvider(LocalButtonGroup provides state, content = content)
        },
        modifier = modifier
            .semantics { isTraversalGroup = true }
            .then(
                if (joined) {
                    Modifier
                        .clip(shape)
                        .drawWithContent {
                            drawContent()
                            if (state.outlined > 0) {
                                val stroke = 1.dp.toPx()
                                val inset = stroke / 2
                                val path = shape.createOutline(
                                    Size(size.width - stroke, size.height - stroke),
                                    layoutDirection,
                                    this,
                                )
                                translate(inset, inset) {
                                    drawOutline(path, outline, style = Stroke(stroke))
                                }
                            }
                        }
                } else {
                    Modifier
                },
            ),
    ) { measurables, constraints ->
        val gap = if (joined) 0 else 8.dp.roundToPx()
        val items = measurables.filter { it.layoutId != ButtonGroupDivider }
        if (horizontal) {
            val height = if (constraints.hasFixedHeight) {
                constraints.maxHeight
            } else {
                constraints.constrainHeight(items.maxOfOrNull { it.maxIntrinsicHeight(Constraints.Infinity) } ?: 0)
            }
            val fills = measurables.count { it.layoutId == ButtonGroupFill }
            val placeables = arrayOfNulls<Placeable>(measurables.size)
            var used = 0
            measurables.forEachIndexed { index, measurable ->
                if (measurable.layoutId != ButtonGroupFill) {
                    val placeable = measurable.measure(Constraints(minHeight = height, maxHeight = height))
                    placeables[index] = placeable
                    used += placeable.width
                }
            }
            val gaps = gap * (items.size - 1).coerceAtLeast(0)
            val remaining = if (constraints.hasBoundedWidth) {
                (constraints.maxWidth - used - gaps).coerceAtLeast(0)
            } else {
                0
            }
            measurables.forEachIndexed { index, measurable ->
                if (measurable.layoutId == ButtonGroupFill) {
                    val placeable = if (constraints.hasBoundedWidth) {
                        val width = remaining / fills
                        measurable.measure(Constraints(width, width, height, height))
                    } else {
                        measurable.measure(Constraints(minHeight = height, maxHeight = height))
                    }
                    placeables[index] = placeable
                    used += placeable.width
                }
            }
            val width = constraints.constrainWidth(used + gaps)
            layout(width, height) {
                var x = 0
                measurables.forEachIndexed { index, measurable ->
                    val placeable = placeables[index] ?: return@forEachIndexed
                    val divider = measurable.layoutId == ButtonGroupDivider
                    placeable.placeRelative(x, 0, zIndex = if (divider) 1f else 0f)
                    if (!divider) x += placeable.width + gap
                }
            }
        } else {
            val width = if (constraints.hasFixedWidth) {
                constraints.maxWidth
            } else {
                constraints.constrainWidth(items.maxOfOrNull { it.maxIntrinsicWidth(Constraints.Infinity) } ?: 0)
            }
            val placeables = measurables.map { it.measure(Constraints(minWidth = width, maxWidth = width)) }
            val gaps = gap * (items.size - 1).coerceAtLeast(0)
            val height = constraints.constrainHeight(
                placeables.filterIndexed { index, _ -> measurables[index].layoutId != ButtonGroupDivider }.sumOf { it.height } + gaps,
            )
            layout(width, height) {
                var y = 0
                measurables.forEachIndexed { index, measurable ->
                    val divider = measurable.layoutId == ButtonGroupDivider
                    placeables[index].placeRelative(0, y, zIndex = if (divider) 1f else 0f)
                    if (!divider) y += placeables[index].height + gap
                }
            }
        }
    }
}

@Composable
fun ButtonGroupText(
    modifier: Modifier = Modifier,
    content: @Composable RowScope.() -> Unit,
) {
    val colors = EsuissTheme.colors
    val shape = LocalButtonGroup.current.itemShape(CircleShape)
    Row(
        modifier = modifier
            .clip(shape)
            .background(colors.control, shape)
            .padding(horizontal = 10.dp),
        horizontalArrangement = Arrangement.spacedBy(8.dp),
        verticalAlignment = Alignment.CenterVertically,
    ) {
        CompositionLocalProvider(
            LocalButtonGroup provides null,
            LocalContentStyle provides Typography.sm.copy(color = colors.label),
            LocalContentColor provides colors.label,
            LocalIconSize provides 16.dp,
        ) {
            content()
        }
    }
}

@Composable
fun ButtonGroupSeparator(
    modifier: Modifier = Modifier,
    orientation: Orientation = Orientation.Vertical,
    color: Color = Color.Unspecified,
) {
    val line = color.takeOrElse { EsuissTheme.colors.label.copy(alpha = 0.2f) }
    Box(
        modifier = modifier
            .layoutId(ButtonGroupDivider)
            .then(
                if (orientation == Orientation.Vertical) {
                    Modifier.layout { measurable, constraints ->
                        val placeable = measurable.measure(constraints.copy(minWidth = 0, maxWidth = 0))
                        layout(0, placeable.height) { placeable.place(0, 0) }
                    }
                } else {
                    Modifier.layout { measurable, constraints ->
                        val placeable = measurable.measure(constraints.copy(minHeight = 0, maxHeight = 0))
                        layout(placeable.width, 0) { placeable.place(0, 0) }
                    }
                },
            )
            .drawBehind {
                val stroke = 1.dp.toPx()
                val inset = 9.dp.toPx()
                if (orientation == Orientation.Vertical) {
                    val x = if (layoutDirection == LayoutDirection.Rtl) -stroke else 0f
                    drawRect(line, Offset(x, inset), Size(stroke, (size.height - inset * 2).coerceAtLeast(0f)))
                } else {
                    drawRect(line, Offset(inset, 0f), Size((size.width - inset * 2).coerceAtLeast(0f), stroke))
                }
            },
    )
}
```

```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 { Header, HeaderTitle, HeaderLargeTitle, HeaderBack, HeaderActions, HeaderScrollView } from "@/components/ui/header"
```

```tsx
<View className="-mx-4 -mt-4">
  <Header>
    <HeaderBack>Settings</HeaderBack>
    <HeaderTitle>Profile</HeaderTitle>
    <HeaderActions>
      <Button variant="plain" size="sm">
        <Text className="font-semibold">Edit</Text>
      </Button>
    </HeaderActions>
  </Header>
</View>
```

`HeaderBack` shows a caret and an optional text label such as the previous screen's name; wire `onPress` to your navigation. Group icon buttons in `HeaderActions`, and set `side="leading"` to place a group on the start side.

Both `HeaderTitle` and `HeaderLargeTitle` accept a `subtitle`. Plain strings are wrapped in `Text` and truncated to one line in the bar.

Without a large title, you can still pass the same `scroll` to `Header` and `HeaderScrollView` to show the hairline once content scrolls under the bar.

## Examples

### Large title

A large title that collapses into the bar on scroll.

![Preview](https://uim.suiss.app/previews/components-header--large-title.light.webp)

```tsx
import { MagnifyingGlassIcon, PlusIcon } from "phosphor-react-native"
import { View } from "react-native"
import { Button } from "@/components/ui/button"
import { Header, HeaderActions, HeaderBack, HeaderLargeTitle, HeaderScrollView, HeaderTitle, useHeaderScroll } from "@/components/ui/header"
import { Icon } from "@/components/ui/icon"
import { Text } from "@/components/ui/text"

const messages = [
  "Lunch on Friday?",
  "The draft is ready for review",
  "Photos from the trip",
  "Invoice for September",
  "Your order has shipped",
  "Team sync moved to 3 PM",
  "Weekend plans",
  "Book club picks",
  "Flight confirmation",
  "New comment on your post",
  "Reminder: dentist at 10",
  "Quarterly report",
  "Welcome to the beta",
  "Parking update",
  "Recipe you asked for",
]

function MessageRows() {
  return (
    <View className="px-4">
      {messages.map((message, index) => (
        <View
          key={message}
          className={index > 0 ? "border-t border-separator py-3" : "py-3"}
        >
          <Text numberOfLines={1}>{message}</Text>
        </View>
      ))}
    </View>
  )
}

function TrailingActions() {
  return (
    <HeaderActions>
      <Button variant="ghost" size="icon" accessibilityLabel="Search">
        <Icon as={MagnifyingGlassIcon} className="size-5" />
      </Button>
      <Button variant="ghost" size="icon" accessibilityLabel="New message">
        <Icon as={PlusIcon} className="size-5" />
      </Button>
    </HeaderActions>
  )
}

function LargeTitleDemo({ subtitle }: { subtitle?: string }) {
  const scroll = useHeaderScroll()
  return (
    <View className="-m-4 flex-1">
      <Header scroll={scroll}>
        <HeaderBack>Mailboxes</HeaderBack>
        <HeaderTitle>Inbox</HeaderTitle>
        <TrailingActions />
      </Header>
      <HeaderScrollView scroll={scroll}>
        <HeaderLargeTitle subtitle={subtitle}>Inbox</HeaderLargeTitle>
        <MessageRows />
      </HeaderScrollView>
    </View>
  )
}

export function HeaderLargeTitleExample() {
  return (
    <LargeTitleDemo />
  )
}
```

```swift
import EsuissUI
import PhosphorSwift
import SwiftUI

let headerMessages = [
  "Lunch on Friday?",
  "The draft is ready for review",
  "Photos from the trip",
  "Invoice for September",
  "Your order has shipped",
  "Team sync moved to 3 PM",
  "Weekend plans",
  "Book club picks",
  "Flight confirmation",
  "New comment on your post",
  "Reminder: dentist at 10",
  "Quarterly report",
  "Welcome to the beta",
  "Parking update",
  "Recipe you asked for",
]

extension View {
  func headerStoryBleed() -> some View {
    padding(.horizontal, -16).padding(.top, -16)
  }
}

struct HeaderMessageRows: View {
  var body: some View {
    VStack(alignment: .leading, spacing: 0) {
      ForEach(Array(headerMessages.enumerated()), id: \.offset) { index, message in
        Text(LocalizedStringKey(message))
          .textStyle(.base)
          .foregroundStyle(Color.label)
          .lineLimit(1)
          .padding(.vertical, 12)
          .frame(maxWidth: .infinity, alignment: .leading)
          .overlay(alignment: .top) {
            if index > 0 {
              Color.separator.frame(height: 1)
            }
          }
      }
    }
    .padding(.horizontal, 16)
  }
}

struct HeaderIconButton: View {
  let icon: Image
  let label: LocalizedStringKey

  var body: some View {
    Button {} label: {
      icon.frame(width: 20, height: 20)
    }
    .accessibilityLabel(Text(label))
  }
}

struct HeaderTrailingActions: View {
  var body: some View {
    HeaderActions {
      HeaderIconButton(icon: Ph.magnifyingGlass.regular, label: "Search")
      HeaderIconButton(icon: Ph.plus.regular, label: "New message")
    }
  }
}

struct HeaderLargeTitleDemo: View {
  var subtitle: LocalizedStringKey?

  var body: some View {
    HeaderScrollView {
      HeaderLargeTitle("Inbox", subtitle: subtitle)
      HeaderMessageRows()
    } header: {
      Header {
        HeaderTitle("Inbox")
      } leading: {
        HeaderBack("Mailboxes")
      } trailing: {
        HeaderTrailingActions()
      }
    }
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.verticalScroll
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.input.nestedscroll.nestedScroll
import androidx.compose.ui.layout.layout
import androidx.compose.ui.text.style.TextOverflow
import androidx.compose.ui.unit.dp
import com.adamglin.PhosphorIcons
import com.adamglin.phosphoricons.Regular
import com.adamglin.phosphoricons.regular.MagnifyingGlass
import com.adamglin.phosphoricons.regular.Plus
import com.esuiss.ui.components.Button
import com.esuiss.ui.components.ButtonSize
import com.esuiss.ui.components.ButtonVariant
import com.esuiss.ui.components.Header
import com.esuiss.ui.components.HeaderActions
import com.esuiss.ui.components.HeaderBack
import com.esuiss.ui.components.HeaderLargeTitle
import com.esuiss.ui.components.HeaderTitle
import com.esuiss.ui.components.Icon
import com.esuiss.ui.components.Screen
import com.esuiss.ui.components.Separator
import com.esuiss.ui.components.Text
import com.esuiss.ui.components.rememberHeaderState

@Composable
fun HeaderLargeTitleExample() {
    HeaderLargeTitleDemo(subtitle = null)
}

val HeaderMessages = listOf(
    "Lunch on Friday?",
    "The draft is ready for review",
    "Photos from the trip",
    "Invoice for September",
    "Your order has shipped",
    "Team sync moved to 3 PM",
    "Weekend plans",
    "Book club picks",
    "Flight confirmation",
    "New comment on your post",
    "Reminder: dentist at 10",
    "Quarterly report",
    "Welcome to the beta",
    "Parking update",
    "Recipe you asked for",
)

fun Modifier.headerBleed(): Modifier = layout { measurable, constraints ->
    val inset = 16.dp.roundToPx()
    val width = constraints.maxWidth + inset * 2
    val placeable = measurable.measure(constraints.copy(minWidth = width, maxWidth = width))
    layout(constraints.maxWidth, (placeable.height - inset).coerceAtLeast(0)) {
        placeable.place(-inset, -inset)
    }
}

@Composable
fun HeaderMessageRows() {
    Column(Modifier.fillMaxWidth().padding(horizontal = 16.dp)) {
        HeaderMessages.forEachIndexed { index, message ->
            if (index > 0) Separator()
            Text(
                message,
                modifier = Modifier.fillMaxWidth().padding(vertical = 12.dp),
                maxLines = 1,
                overflow = TextOverflow.Ellipsis,
            )
        }
    }
}

@Composable
fun HeaderTrailingActions() {
    HeaderActions {
        Button(onClick = {}, variant = ButtonVariant.Ghost, size = ButtonSize.Icon) {
            Icon(PhosphorIcons.Regular.MagnifyingGlass, contentDescription = "Search")
        }
        Button(onClick = {}, variant = ButtonVariant.Ghost, size = ButtonSize.Icon) {
            Icon(PhosphorIcons.Regular.Plus, contentDescription = "New message")
        }
    }
}

@Composable
fun HeaderLargeTitleDemo(subtitle: String?) {
    val state = rememberHeaderState()
    Screen {
        Column(Modifier.fillMaxSize().nestedScroll(state.nestedScrollConnection)) {
            Header(state = state) {
                HeaderBack(onClick = {}, text = "Mailboxes")
                HeaderTitle("Inbox")
                HeaderLargeTitle("Inbox", subtitle = subtitle)
                HeaderTrailingActions()
            }
            Column(Modifier.weight(1f).fillMaxWidth().verticalScroll(rememberScrollState())) {
                HeaderMessageRows()
            }
        }
    }
}
```

### Large title with subtitle

A large title with a subtitle.

![Preview](https://uim.suiss.app/previews/components-header--large-title-with-subtitle.light.webp)

```tsx
import { MagnifyingGlassIcon, PlusIcon } from "phosphor-react-native"
import { View } from "react-native"
import { Button } from "@/components/ui/button"
import { Header, HeaderActions, HeaderBack, HeaderLargeTitle, HeaderScrollView, HeaderTitle, useHeaderScroll } from "@/components/ui/header"
import { Icon } from "@/components/ui/icon"
import { Text } from "@/components/ui/text"

const messages = [
  "Lunch on Friday?",
  "The draft is ready for review",
  "Photos from the trip",
  "Invoice for September",
  "Your order has shipped",
  "Team sync moved to 3 PM",
  "Weekend plans",
  "Book club picks",
  "Flight confirmation",
  "New comment on your post",
  "Reminder: dentist at 10",
  "Quarterly report",
  "Welcome to the beta",
  "Parking update",
  "Recipe you asked for",
]

function MessageRows() {
  return (
    <View className="px-4">
      {messages.map((message, index) => (
        <View
          key={message}
          className={index > 0 ? "border-t border-separator py-3" : "py-3"}
        >
          <Text numberOfLines={1}>{message}</Text>
        </View>
      ))}
    </View>
  )
}

function TrailingActions() {
  return (
    <HeaderActions>
      <Button variant="ghost" size="icon" accessibilityLabel="Search">
        <Icon as={MagnifyingGlassIcon} className="size-5" />
      </Button>
      <Button variant="ghost" size="icon" accessibilityLabel="New message">
        <Icon as={PlusIcon} className="size-5" />
      </Button>
    </HeaderActions>
  )
}

function LargeTitleDemo({ subtitle }: { subtitle?: string }) {
  const scroll = useHeaderScroll()
  return (
    <View className="-m-4 flex-1">
      <Header scroll={scroll}>
        <HeaderBack>Mailboxes</HeaderBack>
        <HeaderTitle>Inbox</HeaderTitle>
        <TrailingActions />
      </Header>
      <HeaderScrollView scroll={scroll}>
        <HeaderLargeTitle subtitle={subtitle}>Inbox</HeaderLargeTitle>
        <MessageRows />
      </HeaderScrollView>
    </View>
  )
}

export function HeaderLargeTitleWithSubtitleExample() {
  return (
    <LargeTitleDemo subtitle="3 unread" />
  )
}
```

```swift
import EsuissUI
import PhosphorSwift
import SwiftUI

struct HeaderLargeTitleWithSubtitleExample: View {
  var body: some View {
    HeaderLargeTitleDemo(subtitle: "3 unread")
  }
}

let headerMessages = [
  "Lunch on Friday?",
  "The draft is ready for review",
  "Photos from the trip",
  "Invoice for September",
  "Your order has shipped",
  "Team sync moved to 3 PM",
  "Weekend plans",
  "Book club picks",
  "Flight confirmation",
  "New comment on your post",
  "Reminder: dentist at 10",
  "Quarterly report",
  "Welcome to the beta",
  "Parking update",
  "Recipe you asked for",
]

extension View {
  func headerStoryBleed() -> some View {
    padding(.horizontal, -16).padding(.top, -16)
  }
}

struct HeaderMessageRows: View {
  var body: some View {
    VStack(alignment: .leading, spacing: 0) {
      ForEach(Array(headerMessages.enumerated()), id: \.offset) { index, message in
        Text(LocalizedStringKey(message))
          .textStyle(.base)
          .foregroundStyle(Color.label)
          .lineLimit(1)
          .padding(.vertical, 12)
          .frame(maxWidth: .infinity, alignment: .leading)
          .overlay(alignment: .top) {
            if index > 0 {
              Color.separator.frame(height: 1)
            }
          }
      }
    }
    .padding(.horizontal, 16)
  }
}

struct HeaderIconButton: View {
  let icon: Image
  let label: LocalizedStringKey

  var body: some View {
    Button {} label: {
      icon.frame(width: 20, height: 20)
    }
    .accessibilityLabel(Text(label))
  }
}

struct HeaderTrailingActions: View {
  var body: some View {
    HeaderActions {
      HeaderIconButton(icon: Ph.magnifyingGlass.regular, label: "Search")
      HeaderIconButton(icon: Ph.plus.regular, label: "New message")
    }
  }
}

struct HeaderLargeTitleDemo: View {
  var subtitle: LocalizedStringKey?

  var body: some View {
    HeaderScrollView {
      HeaderLargeTitle("Inbox", subtitle: subtitle)
      HeaderMessageRows()
    } header: {
      Header {
        HeaderTitle("Inbox")
      } leading: {
        HeaderBack("Mailboxes")
      } trailing: {
        HeaderTrailingActions()
      }
    }
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.verticalScroll
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.input.nestedscroll.nestedScroll
import androidx.compose.ui.layout.layout
import androidx.compose.ui.text.style.TextOverflow
import androidx.compose.ui.unit.dp
import com.adamglin.PhosphorIcons
import com.adamglin.phosphoricons.Regular
import com.adamglin.phosphoricons.regular.MagnifyingGlass
import com.adamglin.phosphoricons.regular.Plus
import com.esuiss.ui.components.Button
import com.esuiss.ui.components.ButtonSize
import com.esuiss.ui.components.ButtonVariant
import com.esuiss.ui.components.Header
import com.esuiss.ui.components.HeaderActions
import com.esuiss.ui.components.HeaderBack
import com.esuiss.ui.components.HeaderLargeTitle
import com.esuiss.ui.components.HeaderTitle
import com.esuiss.ui.components.Icon
import com.esuiss.ui.components.Screen
import com.esuiss.ui.components.Separator
import com.esuiss.ui.components.Text
import com.esuiss.ui.components.rememberHeaderState

@Composable
fun HeaderLargeTitleWithSubtitleExample() {
    HeaderLargeTitleDemo(subtitle = "3 unread")
}

val HeaderMessages = listOf(
    "Lunch on Friday?",
    "The draft is ready for review",
    "Photos from the trip",
    "Invoice for September",
    "Your order has shipped",
    "Team sync moved to 3 PM",
    "Weekend plans",
    "Book club picks",
    "Flight confirmation",
    "New comment on your post",
    "Reminder: dentist at 10",
    "Quarterly report",
    "Welcome to the beta",
    "Parking update",
    "Recipe you asked for",
)

fun Modifier.headerBleed(): Modifier = layout { measurable, constraints ->
    val inset = 16.dp.roundToPx()
    val width = constraints.maxWidth + inset * 2
    val placeable = measurable.measure(constraints.copy(minWidth = width, maxWidth = width))
    layout(constraints.maxWidth, (placeable.height - inset).coerceAtLeast(0)) {
        placeable.place(-inset, -inset)
    }
}

@Composable
fun HeaderMessageRows() {
    Column(Modifier.fillMaxWidth().padding(horizontal = 16.dp)) {
        HeaderMessages.forEachIndexed { index, message ->
            if (index > 0) Separator()
            Text(
                message,
                modifier = Modifier.fillMaxWidth().padding(vertical = 12.dp),
                maxLines = 1,
                overflow = TextOverflow.Ellipsis,
            )
        }
    }
}

@Composable
fun HeaderTrailingActions() {
    HeaderActions {
        Button(onClick = {}, variant = ButtonVariant.Ghost, size = ButtonSize.Icon) {
            Icon(PhosphorIcons.Regular.MagnifyingGlass, contentDescription = "Search")
        }
        Button(onClick = {}, variant = ButtonVariant.Ghost, size = ButtonSize.Icon) {
            Icon(PhosphorIcons.Regular.Plus, contentDescription = "New message")
        }
    }
}

@Composable
fun HeaderLargeTitleDemo(subtitle: String?) {
    val state = rememberHeaderState()
    Screen {
        Column(Modifier.fillMaxSize().nestedScroll(state.nestedScrollConnection)) {
            Header(state = state) {
                HeaderBack(onClick = {}, text = "Mailboxes")
                HeaderTitle("Inbox")
                HeaderLargeTitle("Inbox", subtitle = subtitle)
                HeaderTrailingActions()
            }
            Column(Modifier.weight(1f).fillMaxWidth().verticalScroll(rememberScrollState())) {
                HeaderMessageRows()
            }
        }
    }
}
```

### Compact with scroll

A compact title whose hairline appears on scroll.

![Preview](https://uim.suiss.app/previews/components-header--compact-with-scroll.light.webp)

```tsx
import { DotsThreeIcon } from "phosphor-react-native"
import { View } from "react-native"
import { Button } from "@/components/ui/button"
import { Header, HeaderActions, HeaderBack, HeaderScrollView, HeaderTitle, useHeaderScroll } from "@/components/ui/header"
import { Icon } from "@/components/ui/icon"
import { Text } from "@/components/ui/text"

const messages = [
  "Lunch on Friday?",
  "The draft is ready for review",
  "Photos from the trip",
  "Invoice for September",
  "Your order has shipped",
  "Team sync moved to 3 PM",
  "Weekend plans",
  "Book club picks",
  "Flight confirmation",
  "New comment on your post",
  "Reminder: dentist at 10",
  "Quarterly report",
  "Welcome to the beta",
  "Parking update",
  "Recipe you asked for",
]

function MessageRows() {
  return (
    <View className="px-4">
      {messages.map((message, index) => (
        <View
          key={message}
          className={index > 0 ? "border-t border-separator py-3" : "py-3"}
        >
          <Text numberOfLines={1}>{message}</Text>
        </View>
      ))}
    </View>
  )
}

function CompactScrollDemo() {
  const scroll = useHeaderScroll()
  return (
    <View className="-m-4 flex-1">
      <Header scroll={scroll}>
        <HeaderBack />
        <HeaderTitle subtitle="15 messages">Inbox</HeaderTitle>
        <HeaderActions>
          <Button variant="ghost" size="icon" accessibilityLabel="More">
            <Icon as={DotsThreeIcon} weight="bold" className="size-5" />
          </Button>
        </HeaderActions>
      </Header>
      <HeaderScrollView scroll={scroll}>
        <MessageRows />
      </HeaderScrollView>
    </View>
  )
}

export function HeaderCompactWithScrollExample() {
  return (
    <CompactScrollDemo />
  )
}
```

```swift
import EsuissUI
import PhosphorSwift
import SwiftUI

struct HeaderCompactWithScrollExample: View {
  var body: some View {
    HeaderScrollView {
      HeaderMessageRows()
    } header: {
      Header {
        HeaderTitle("Inbox", subtitle: "15 messages")
      } leading: {
        HeaderBack()
      } trailing: {
        HeaderActions {
          HeaderIconButton(icon: Ph.dotsThree.bold, label: "More")
        }
      }
    }
  }
}

let headerMessages = [
  "Lunch on Friday?",
  "The draft is ready for review",
  "Photos from the trip",
  "Invoice for September",
  "Your order has shipped",
  "Team sync moved to 3 PM",
  "Weekend plans",
  "Book club picks",
  "Flight confirmation",
  "New comment on your post",
  "Reminder: dentist at 10",
  "Quarterly report",
  "Welcome to the beta",
  "Parking update",
  "Recipe you asked for",
]

extension View {
  func headerStoryBleed() -> some View {
    padding(.horizontal, -16).padding(.top, -16)
  }
}

struct HeaderMessageRows: View {
  var body: some View {
    VStack(alignment: .leading, spacing: 0) {
      ForEach(Array(headerMessages.enumerated()), id: \.offset) { index, message in
        Text(LocalizedStringKey(message))
          .textStyle(.base)
          .foregroundStyle(Color.label)
          .lineLimit(1)
          .padding(.vertical, 12)
          .frame(maxWidth: .infinity, alignment: .leading)
          .overlay(alignment: .top) {
            if index > 0 {
              Color.separator.frame(height: 1)
            }
          }
      }
    }
    .padding(.horizontal, 16)
  }
}

struct HeaderIconButton: View {
  let icon: Image
  let label: LocalizedStringKey

  var body: some View {
    Button {} label: {
      icon.frame(width: 20, height: 20)
    }
    .accessibilityLabel(Text(label))
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.verticalScroll
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.layout
import androidx.compose.ui.text.style.TextOverflow
import androidx.compose.ui.unit.dp
import com.adamglin.PhosphorIcons
import com.adamglin.phosphoricons.Bold
import com.adamglin.phosphoricons.bold.DotsThree
import com.esuiss.ui.components.Button
import com.esuiss.ui.components.ButtonSize
import com.esuiss.ui.components.ButtonVariant
import com.esuiss.ui.components.Header
import com.esuiss.ui.components.HeaderActions
import com.esuiss.ui.components.HeaderBack
import com.esuiss.ui.components.HeaderTitle
import com.esuiss.ui.components.Icon
import com.esuiss.ui.components.Screen
import com.esuiss.ui.components.Separator
import com.esuiss.ui.components.Text

val HeaderMessages = listOf(
    "Lunch on Friday?",
    "The draft is ready for review",
    "Photos from the trip",
    "Invoice for September",
    "Your order has shipped",
    "Team sync moved to 3 PM",
    "Weekend plans",
    "Book club picks",
    "Flight confirmation",
    "New comment on your post",
    "Reminder: dentist at 10",
    "Quarterly report",
    "Welcome to the beta",
    "Parking update",
    "Recipe you asked for",
)

fun Modifier.headerBleed(): Modifier = layout { measurable, constraints ->
    val inset = 16.dp.roundToPx()
    val width = constraints.maxWidth + inset * 2
    val placeable = measurable.measure(constraints.copy(minWidth = width, maxWidth = width))
    layout(constraints.maxWidth, (placeable.height - inset).coerceAtLeast(0)) {
        placeable.place(-inset, -inset)
    }
}

@Composable
fun HeaderMessageRows() {
    Column(Modifier.fillMaxWidth().padding(horizontal = 16.dp)) {
        HeaderMessages.forEachIndexed { index, message ->
            if (index > 0) Separator()
            Text(
                message,
                modifier = Modifier.fillMaxWidth().padding(vertical = 12.dp),
                maxLines = 1,
                overflow = TextOverflow.Ellipsis,
            )
        }
    }
}

@Composable
fun HeaderCompactScroll() {
    Screen {
        Column(Modifier.fillMaxSize()) {
            Header {
                HeaderBack(onClick = {}, text = null)
                HeaderTitle("Inbox", subtitle = "15 messages")
                HeaderActions {
                    Button(onClick = {}, variant = ButtonVariant.Ghost, size = ButtonSize.Icon) {
                        Icon(PhosphorIcons.Bold.DotsThree, contentDescription = "More")
                    }
                }
            }
            Column(Modifier.weight(1f).fillMaxWidth().verticalScroll(rememberScrollState())) {
                HeaderMessageRows()
            }
        }
    }
}
```

### Subtitle

A two-line title with a subtitle.

![Preview](https://uim.suiss.app/previews/components-header--subtitle.light.webp)

```tsx
import { MagnifyingGlassIcon, PlusIcon } from "phosphor-react-native"
import { View } from "react-native"
import { Button } from "@/components/ui/button"
import { Header, HeaderActions, HeaderBack, HeaderTitle } from "@/components/ui/header"
import { Icon } from "@/components/ui/icon"

function TrailingActions() {
  return (
    <HeaderActions>
      <Button variant="ghost" size="icon" accessibilityLabel="Search">
        <Icon as={MagnifyingGlassIcon} className="size-5" />
      </Button>
      <Button variant="ghost" size="icon" accessibilityLabel="New message">
        <Icon as={PlusIcon} className="size-5" />
      </Button>
    </HeaderActions>
  )
}

export function HeaderSubtitleExample() {
  return (
    <View className="-mx-4 -mt-4">
      <Header>
        <HeaderBack />
        <HeaderTitle subtitle="Last seen today">Alex Morgan</HeaderTitle>
        <TrailingActions />
      </Header>
    </View>
  )
}
```

```swift
import EsuissUI
import PhosphorSwift
import SwiftUI

struct HeaderSubtitleExample: View {
  var body: some View {
    Header {
      HeaderTitle("Alex Morgan", subtitle: "Last seen today")
    } leading: {
      HeaderBack()
    } trailing: {
      HeaderTrailingActions()
    }
    .headerStoryBleed()
  }
}

extension View {
  func headerStoryBleed() -> some View {
    padding(.horizontal, -16).padding(.top, -16)
  }
}

struct HeaderIconButton: View {
  let icon: Image
  let label: LocalizedStringKey

  var body: some View {
    Button {} label: {
      icon.frame(width: 20, height: 20)
    }
    .accessibilityLabel(Text(label))
  }
}

struct HeaderTrailingActions: View {
  var body: some View {
    HeaderActions {
      HeaderIconButton(icon: Ph.magnifyingGlass.regular, label: "Search")
      HeaderIconButton(icon: Ph.plus.regular, label: "New message")
    }
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Column
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.layout
import androidx.compose.ui.unit.dp
import com.adamglin.PhosphorIcons
import com.adamglin.phosphoricons.Regular
import com.adamglin.phosphoricons.regular.MagnifyingGlass
import com.adamglin.phosphoricons.regular.Plus
import com.esuiss.ui.components.Button
import com.esuiss.ui.components.ButtonSize
import com.esuiss.ui.components.ButtonVariant
import com.esuiss.ui.components.Header
import com.esuiss.ui.components.HeaderActions
import com.esuiss.ui.components.HeaderBack
import com.esuiss.ui.components.HeaderTitle
import com.esuiss.ui.components.Icon

fun Modifier.headerBleed(): Modifier = layout { measurable, constraints ->
    val inset = 16.dp.roundToPx()
    val width = constraints.maxWidth + inset * 2
    val placeable = measurable.measure(constraints.copy(minWidth = width, maxWidth = width))
    layout(constraints.maxWidth, (placeable.height - inset).coerceAtLeast(0)) {
        placeable.place(-inset, -inset)
    }
}

@Composable
fun HeaderTrailingActions() {
    HeaderActions {
        Button(onClick = {}, variant = ButtonVariant.Ghost, size = ButtonSize.Icon) {
            Icon(PhosphorIcons.Regular.MagnifyingGlass, contentDescription = "Search")
        }
        Button(onClick = {}, variant = ButtonVariant.Ghost, size = ButtonSize.Icon) {
            Icon(PhosphorIcons.Regular.Plus, contentDescription = "New message")
        }
    }
}

@Composable
fun HeaderSubtitle() {
    Column(Modifier.headerBleed()) {
        Header {
            HeaderBack(onClick = {}, text = null)
            HeaderTitle("Alex Morgan", subtitle = "Last seen today")
            HeaderTrailingActions()
        }
    }
}
```

### Leading actions

Actions on both sides of the title.

![Preview](https://uim.suiss.app/previews/components-header--leading-actions.light.webp)

```tsx
import { ListIcon } from "phosphor-react-native"
import { View } from "react-native"
import { Button } from "@/components/ui/button"
import { Header, HeaderActions, HeaderTitle } from "@/components/ui/header"
import { Icon } from "@/components/ui/icon"
import { Text } from "@/components/ui/text"

export function HeaderLeadingActionsExample() {
  return (
    <View className="-mx-4 -mt-4">
      <Header>
        <HeaderActions side="leading">
          <Button variant="ghost" size="icon" accessibilityLabel="Menu">
            <Icon as={ListIcon} className="size-5" />
          </Button>
        </HeaderActions>
        <HeaderTitle>Library</HeaderTitle>
        <HeaderActions>
          <Button variant="plain" size="sm">
            <Text className="font-semibold">Done</Text>
          </Button>
        </HeaderActions>
      </Header>
    </View>
  )
}
```

```swift
import EsuissUI
import PhosphorSwift
import SwiftUI

struct HeaderLeadingActionsExample: View {
  var body: some View {
    Header {
      HeaderTitle("Library")
    } leading: {
      HeaderActions {
        HeaderIconButton(icon: Ph.list.regular, label: "Menu")
      }
    } trailing: {
      HeaderActions {
        Button {} label: {
          Text("Done").fontWeight(.semibold)
        }
        .buttonStyle(.variant(.plain, size: .sm))
      }
    }
    .headerStoryBleed()
  }
}

extension View {
  func headerStoryBleed() -> some View {
    padding(.horizontal, -16).padding(.top, -16)
  }
}

struct HeaderIconButton: View {
  let icon: Image
  let label: LocalizedStringKey

  var body: some View {
    Button {} label: {
      icon.frame(width: 20, height: 20)
    }
    .accessibilityLabel(Text(label))
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Column
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.layout
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.unit.dp
import com.adamglin.PhosphorIcons
import com.adamglin.phosphoricons.Regular
import com.adamglin.phosphoricons.regular.List
import com.esuiss.ui.components.Button
import com.esuiss.ui.components.ButtonSize
import com.esuiss.ui.components.ButtonVariant
import com.esuiss.ui.components.Header
import com.esuiss.ui.components.HeaderActions
import com.esuiss.ui.components.HeaderActionsSide
import com.esuiss.ui.components.HeaderTitle
import com.esuiss.ui.components.Icon
import com.esuiss.ui.components.Text

fun Modifier.headerBleed(): Modifier = layout { measurable, constraints ->
    val inset = 16.dp.roundToPx()
    val width = constraints.maxWidth + inset * 2
    val placeable = measurable.measure(constraints.copy(minWidth = width, maxWidth = width))
    layout(constraints.maxWidth, (placeable.height - inset).coerceAtLeast(0)) {
        placeable.place(-inset, -inset)
    }
}

@Composable
fun HeaderPlainAction(text: String) {
    Button(onClick = {}, variant = ButtonVariant.Plain, size = ButtonSize.Sm) {
        Text(text, style = TextStyle(fontWeight = FontWeight.SemiBold))
    }
}

@Composable
fun HeaderLeadingActions() {
    Column(Modifier.headerBleed()) {
        Header {
            HeaderActions(side = HeaderActionsSide.Leading) {
                Button(onClick = {}, variant = ButtonVariant.Ghost, size = ButtonSize.Icon) {
                    Icon(PhosphorIcons.Regular.List, contentDescription = "Menu")
                }
            }
            HeaderTitle("Library")
            HeaderActions { HeaderPlainAction("Done") }
        }
    }
}
```

### Back only

A long back label that truncates.

![Preview](https://uim.suiss.app/previews/components-header--back-only.light.webp)

```tsx
import { View } from "react-native"
import { Header, HeaderBack, HeaderTitle } from "@/components/ui/header"

export function HeaderBackOnlyExample() {
  return (
    <View className="-mx-4 -mt-4">
      <Header>
        <HeaderBack>A very long previous screen title</HeaderBack>
        <HeaderTitle>Details</HeaderTitle>
      </Header>
    </View>
  )
}
```

```swift
import EsuissUI
import SwiftUI

struct HeaderBackOnlyExample: View {
  var body: some View {
    Header {
      HeaderTitle("Details")
    } leading: {
      HeaderBack("A very long previous screen title")
    }
    .headerStoryBleed()
  }
}
```

```kotlin
import androidx.compose.foundation.layout.Column
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.layout
import androidx.compose.ui.unit.dp
import com.esuiss.ui.components.Header
import com.esuiss.ui.components.HeaderBack
import com.esuiss.ui.components.HeaderTitle

fun Modifier.headerBleed(): Modifier = layout { measurable, constraints ->
    val inset = 16.dp.roundToPx()
    val width = constraints.maxWidth + inset * 2
    val placeable = measurable.measure(constraints.copy(minWidth = width, maxWidth = width))
    layout(constraints.maxWidth, (placeable.height - inset).coerceAtLeast(0)) {
        placeable.place(-inset, -inset)
    }
}

@Composable
fun HeaderBackOnly() {
    Column(Modifier.headerBleed()) {
        Header {
            HeaderBack(onClick = {}, text = "A very long previous screen title")
            HeaderTitle("Details")
        }
    }
}
```

## API Reference

### Header

Bar that lays out the back button, title and actions.

### HeaderTitle

Centered title with optional subtitle.

### HeaderLargeTitle

Large title at the top of the scroll content.

### HeaderBack

Back button with a caret and optional label.

### HeaderActions

Row of actions for either side.

### HeaderScrollView

Scroll view that drives the header animations.

## Accessibility

- `HeaderTitle` and a string `HeaderLargeTitle` have the `heading` role.
- `HeaderBack` has the `button` role and is labelled with its text, or "Back" when it has none.
- Give icon-only actions an `accessibilityLabel`.

## Notes

- The back caret rotates and the large title scales from the correct edge in right-to-left layouts.
- Uses `text-link`, `bg-separator` and `bg-item-pressed` tokens; light and dark follow the system appearance.