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import {
Children,
cloneElement,
isValidElement,
type ReactElement,
type ReactNode,
useCallback,
useEffect,
useMemo,
useRef,
} from 'react'
import {
AccessibilityInfo,
findNodeHandle,
Pressable,
Text,
View,
} from 'react-native'
import {msg} from '@lingui/macro'
import {useLingui} from '@lingui/react'
import {useA11y} from '#/state/a11y'
/**
* Conditionally wraps children in a `FocusTrap` component based on whether
* screen reader support is enabled. THIS SHOULD BE USED SPARINGLY, only when
* no better option is available.
*/
export function FocusScope({children}: {children: ReactNode}) {
const {screenReaderEnabled} = useA11y()
return screenReaderEnabled ? <FocusTrap>{children}</FocusTrap> : children
}
/**
* `FocusTrap` is intended as a last-ditch effort to ensure that users keep
* focus within a certain section of the app, like an overlay.
*
* It works by placing "guards" at the start and end of the active content.
* Then when the user reaches either of those guards, it will announce that
* they have reached the start or end of the content and tell them how to
* remain within the active content section.
*/
function FocusTrap({children}: {children: ReactNode}) {
const {_} = useLingui()
const child = useRef<View>(null)
/*
* Here we add a ref to the first child of this component. This currently
* overrides any ref already on that first child, so we throw an error here
* to prevent us from ever accidentally doing this.
*/
const decoratedChildren = useMemo(() => {
return Children.toArray(children).map((node, i) => {
if (i === 0 && isValidElement(node)) {
const n = node as ReactElement<any>
if (n.props.ref !== undefined) {
throw new Error(
'FocusScope needs to override the ref on its first child.',
)
}
return cloneElement(n, {
...n.props,
ref: child,
})
}
return node
})
}, [children])
const focusNode = useCallback((ref: View | null) => {
if (!ref) return
const node = findNodeHandle(ref)
if (node) {
AccessibilityInfo.setAccessibilityFocus(node)
}
}, [])
useEffect(() => {
setTimeout(() => {
focusNode(child.current)
}, 1e3)
}, [focusNode])
return (
<>
<Pressable
accessible
accessibilityLabel={_(
msg`You've reached the start of the active content.`,
)}
accessibilityHint={_(
msg`Please go back, or activate this element to return to the start of the active content.`,
)}
accessibilityActions={[{name: 'activate', label: 'activate'}]}
onAccessibilityAction={event => {
switch (event.nativeEvent.actionName) {
case 'activate': {
focusNode(child.current)
}
}
}}>
<Noop />
</Pressable>
<View
/**
* This property traps focus effectively on iOS, but not on Android.
*/
accessibilityViewIsModal>
{decoratedChildren}
</View>
<Pressable
accessibilityLabel={_(
msg`You've reached the end of the active content.`,
)}
accessibilityHint={_(
msg`Please go back, or activate this element to return to the start of the active content.`,
)}
accessibilityActions={[{name: 'activate', label: 'activate'}]}
onAccessibilityAction={event => {
switch (event.nativeEvent.actionName) {
case 'activate': {
focusNode(child.current)
}
}
}}>
<Noop />
</Pressable>
</>
)
}
function Noop() {
return (
<Text
accessible={false}
style={{
height: 1,
opacity: 0,
}}>
{' '}
</Text>
)
}
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