fix: focus popup when opened

fix #7

Author: jedwards1211

src/core.js

@@ -1,4 +1,5 @@
 // @flow
+/* eslint-env browser */
 
 import * as React from 'react'
 
@@ -62,6 +63,9 @@ export function createPopupState({
       if (!parentPopupState.isOpen) return
       parentPopupState._setChildPopupState(popupState)
     }
+    if (typeof document === 'object' && document.activeElement) {
+      document.activeElement.blur()
+    }
     setState({
       anchorEl:
         eventOrAnchorEl && eventOrAnchorEl.currentTarget

src/hooks.js

@@ -1,4 +1,5 @@
 // @flow
+/* eslint-env browser */
 
 import { useState, useRef, useEffect } from 'react'
 
@@ -42,6 +43,15 @@ export function usePopupState({
     },
     []
   )
+  useEffect(
+    () => {
+      if (popupId && typeof document === 'object') {
+        const popup = document.getElementById(popupId)
+        if (popup) popup.focus()
+      }
+    },
+    [popupId, state.anchorEl]
+  )
   const setState = (nextState: $Shape<CoreState>) => {
     if (isMounted.current) _setState({ ...state, ...nextState })
   }

src/index.js

@@ -1,4 +1,5 @@
 // @flow
+/* eslint-env browser */
 
 import * as React from 'react'
 import PropTypes from 'prop-types'
@@ -81,6 +82,19 @@ export default class PopupState extends React.Component<Props, CoreState> {
     if (this._mounted) this.setState(state)
   }
 
+  componentDidUpdate(prevProps: Props, prevState: CoreState) {
+    const { popupId } = this.props
+    if (
+      popupId !== prevProps.popupId ||
+      this.state.anchorEl !== prevState.anchorEl
+    ) {
+      if (popupId && typeof document === 'object') {
+        const popup = document.getElementById(popupId)
+        if (popup) popup.focus()
+      }
+    }
+  }
+
   render(): React.Node | null {
     const { children, popupId, variant, parentPopupState } = this.props