From 7646f6bd33a03132e446fb060880bbf051a1639f Mon Sep 17 00:00:00 2001
From: Ryan Berliner <22206986+RyanBerliner@users.noreply.github.com>
Date: Tue, 27 Jul 2021 01:01:04 -0400
Subject: Add shift-tab keyboard support for dialogs (modal & Offcanvas
 components) (#33865)

* consolidate dialog focus trap logic

* add shift-tab support to focustrap

* remove redundant null check of trap element

Co-authored-by: GeoSot <geo.sotis@gmail.com>

* remove area support forom focusableChildren

* fix no expectations warning in focustrap tests

Co-authored-by: GeoSot <geo.sotis@gmail.com>
Co-authored-by: XhmikosR <xhmikosr@gmail.com>
---
 js/src/modal.js | 36 +++++++++++-------------------------
 1 file changed, 11 insertions(+), 25 deletions(-)

(limited to 'js/src/modal.js')

diff --git a/js/src/modal.js b/js/src/modal.js
index 0e8346d6f3..53a3ccfd1c 100644
--- a/js/src/modal.js
+++ b/js/src/modal.js
@@ -19,6 +19,7 @@ import SelectorEngine from './dom/selector-engine'
 import ScrollBarHelper from './util/scrollbar'
 import BaseComponent from './base-component'
 import Backdrop from './util/backdrop'
+import FocusTrap from './util/focustrap'
 
 /**
  * ------------------------------------------------------------------------
@@ -49,7 +50,6 @@ const EVENT_HIDE_PREVENTED = `hidePrevented${EVENT_KEY}`
 const EVENT_HIDDEN = `hidden${EVENT_KEY}`
 const EVENT_SHOW = `show${EVENT_KEY}`
 const EVENT_SHOWN = `shown${EVENT_KEY}`
-const EVENT_FOCUSIN = `focusin${EVENT_KEY}`
 const EVENT_RESIZE = `resize${EVENT_KEY}`
 const EVENT_CLICK_DISMISS = `click.dismiss${EVENT_KEY}`
 const EVENT_KEYDOWN_DISMISS = `keydown.dismiss${EVENT_KEY}`
@@ -81,6 +81,7 @@ class Modal extends BaseComponent {
     this._config = this._getConfig(config)
     this._dialog = SelectorEngine.findOne(SELECTOR_DIALOG, this._element)
     this._backdrop = this._initializeBackDrop()
+    this._focustrap = this._initializeFocusTrap()
     this._isShown = false
     this._ignoreBackdropClick = false
     this._isTransitioning = false
@@ -167,7 +168,7 @@ class Modal extends BaseComponent {
     this._setEscapeEvent()
     this._setResizeEvent()
 
-    EventHandler.off(document, EVENT_FOCUSIN)
+    this._focustrap.deactivate()
 
     this._element.classList.remove(CLASS_NAME_SHOW)
 
@@ -182,14 +183,8 @@ class Modal extends BaseComponent {
       .forEach(htmlElement => EventHandler.off(htmlElement, EVENT_KEY))
 
     this._backdrop.dispose()
+    this._focustrap.deactivate()
     super.dispose()
-
-    /**
-     * `document` has 2 events `EVENT_FOCUSIN` and `EVENT_CLICK_DATA_API`
-     * Do not move `document` in `htmlElements` array
-     * It will remove `EVENT_CLICK_DATA_API` event that should remain
-     */
-    EventHandler.off(document, EVENT_FOCUSIN)
   }
 
   handleUpdate() {
@@ -205,6 +200,12 @@ class Modal extends BaseComponent {
     })
   }
 
+  _initializeFocusTrap() {
+    return new FocusTrap({
+      trapElement: this._element
+    })
+  }
+
   _getConfig(config) {
     config = {
       ...Default,
@@ -240,13 +241,9 @@ class Modal extends BaseComponent {
 
     this._element.classList.add(CLASS_NAME_SHOW)
 
-    if (this._config.focus) {
-      this._enforceFocus()
-    }
-
     const transitionComplete = () => {
       if (this._config.focus) {
-        this._element.focus()
+        this._focustrap.activate()
       }
 
       this._isTransitioning = false
@@ -258,17 +255,6 @@ class Modal extends BaseComponent {
     this._queueCallback(transitionComplete, this._dialog, isAnimated)
   }
 
-  _enforceFocus() {
-    EventHandler.off(document, EVENT_FOCUSIN) // guard against infinite focus loop
-    EventHandler.on(document, EVENT_FOCUSIN, event => {
-      if (document !== event.target &&
-          this._element !== event.target &&
-          !this._element.contains(event.target)) {
-        this._element.focus()
-      }
-    })
-  }
-
   _setEscapeEvent() {
     if (this._isShown) {
       EventHandler.on(this._element, EVENT_KEYDOWN_DISMISS, event => {
-- 
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