@tamagui/react-native-web-lite/src/Modal/ModalFocusTrap.js

React Native for Web

/**
 * Copyright (c) Nicolas Gallagher.
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 *
 */
import * as React from 'react'
import { StyleSheet, UIManager, canUseDOM } from '@tamagui/react-native-web-internals'

import createElement from '../createElement/index'
import View from '../View'

/**
 * This Component is used to "wrap" the modal we're opening
 * so that changing focus via tab will never leave the document.
 *
 * This allows us to properly trap the focus within a modal
 * even if the modal is at the start or end of a document.
 */

var FocusBracket = () => {
  return createElement('div', {
    accessibilityRole: 'none',
    tabIndex: 0,
    style: styles.focusBracket,
  })
}

function attemptFocus(element) {
  if (!canUseDOM) {
    return false
  }

  try {
    element.focus()
  } catch (e) {
    // Do nothing
  }

  return document.activeElement === element
}

function focusFirstDescendant(element) {
  for (var i = 0; i < element.childNodes.length; i++) {
    var child = element.childNodes[i]

    if (attemptFocus(child) || focusFirstDescendant(child)) {
      return true
    }
  }

  return false
}

function focusLastDescendant(element) {
  for (var i = element.childNodes.length - 1; i >= 0; i--) {
    var child = element.childNodes[i]

    if (attemptFocus(child) || focusLastDescendant(child)) {
      return true
    }
  }

  return false
}

var ModalFocusTrap = (_ref) => {
  var active = _ref.active,
    children = _ref.children
  var trapElementRef = React.useRef()
  var focusRef = React.useRef({
    trapFocusInProgress: false,
    lastFocusedElement: null,
  })
  React.useEffect(() => {
    if (canUseDOM) {
      var trapFocus = () => {
        // We should not trap focus if:
        // - The modal hasn't fully initialized with an HTMLElement ref
        // - Focus is already in the process of being trapped (e.g., we're refocusing)
        // - isTrapActive prop being falsey tells us to do nothing
        if (
          trapElementRef.current == null ||
          focusRef.current.trapFocusInProgress ||
          !active
        ) {
          return
        }

        try {
          focusRef.current.trapFocusInProgress = true

          if (
            document.activeElement instanceof Node &&
            !trapElementRef.current.contains(document.activeElement)
          ) {
            // To handle keyboard focusing we can make an assumption here.
            // If you're tabbing through the focusable elements, the previously
            // active element will either be the first or the last.
            // If the previously selected element is the "first" descendant
            // and we're leaving it - this means that we should be looping
            // around to the other side of the modal.
            var hasFocused = focusFirstDescendant(trapElementRef.current)

            if (focusRef.current.lastFocusedElement === document.activeElement) {
              hasFocused = focusLastDescendant(trapElementRef.current)
            } // If we couldn't focus a new element then we need to focus onto the trap target

            if (!hasFocused && trapElementRef.current != null && document.activeElement) {
              UIManager.focus(trapElementRef.current)
            }
          }
        } finally {
          focusRef.current.trapFocusInProgress = false
        }

        focusRef.current.lastFocusedElement = document.activeElement
      } // Call the trapFocus callback at least once when this modal has been activated.

      trapFocus()
      document.addEventListener('focus', trapFocus, true)
      return () => document.removeEventListener('focus', trapFocus, true)
    }
  }, [active]) // To be fully compliant with WCAG we need to refocus element that triggered opening modal
  // after closing it

  React.useEffect(function () {
    if (canUseDOM) {
      var lastFocusedElementOutsideTrap = document.activeElement
      return function () {
        if (
          lastFocusedElementOutsideTrap &&
          document.contains(lastFocusedElementOutsideTrap)
        ) {
          UIManager.focus(lastFocusedElementOutsideTrap)
        }
      }
    }
  }, [])
  return /*#__PURE__*/ React.createElement(
    React.Fragment,
    null,
    /*#__PURE__*/ React.createElement(FocusBracket, null),
    /*#__PURE__*/ React.createElement(
      View,
      {
        ref: trapElementRef,
      },
      children
    ),
    /*#__PURE__*/ React.createElement(FocusBracket, null)
  )
}

export default ModalFocusTrap
var styles = StyleSheet.create({
  focusBracket: {
    outlineStyle: 'none',
  },
})