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>

1 files changed, 109 insertions, 0 deletions

diff --git a/js/src/util/focustrap.js b/js/src/util/focustrap.js
new file mode 100644
index 0000000000..ab8462e237
--- /dev/null
+++ b/js/src/util/focustrap.js
@@ -0,0 +1,109 @@
+/**
+ * --------------------------------------------------------------------------
+ * Bootstrap (v5.0.2): util/focustrap.js
+ * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
+ * --------------------------------------------------------------------------
+ */
+
+import EventHandler from '../dom/event-handler'
+import SelectorEngine from '../dom/selector-engine'
+import { typeCheckConfig } from './index'
+
+const Default = {
+  trapElement: null, // The element to trap focus inside of
+  autofocus: true
+}
+
+const DefaultType = {
+  trapElement: 'element',
+  autofocus: 'boolean'
+}
+
+const NAME = 'focustrap'
+const DATA_KEY = 'bs.focustrap'
+const EVENT_KEY = `.${DATA_KEY}`
+const EVENT_FOCUSIN = `focusin${EVENT_KEY}`
+const EVENT_KEYDOWN_TAB = `keydown.tab${EVENT_KEY}`
+
+const TAB_KEY = 'Tab'
+const TAB_NAV_FORWARD = 'forward'
+const TAB_NAV_BACKWARD = 'backward'
+
+class FocusTrap {
+  constructor(config) {
+    this._config = this._getConfig(config)
+    this._isActive = false
+    this._lastTabNavDirection = null
+  }
+
+  activate() {
+    const { trapElement, autofocus } = this._config
+
+    if (this._isActive) {
+      return
+    }
+
+    if (autofocus) {
+      trapElement.focus()
+    }
+
+    EventHandler.off(document, EVENT_KEY) // guard against infinite focus loop
+    EventHandler.on(document, EVENT_FOCUSIN, event => this._handleFocusin(event))
+    EventHandler.on(document, EVENT_KEYDOWN_TAB, event => this._handleKeydown(event))
+
+    this._isActive = true
+  }
+
+  deactivate() {
+    if (!this._isActive) {
+      return
+    }
+
+    this._isActive = false
+    EventHandler.off(document, EVENT_KEY)
+  }
+
+  // Private
+
+  _handleFocusin(event) {
+    const { target } = event
+    const { trapElement } = this._config
+
+    if (
+      target === document ||
+      target === trapElement ||
+      trapElement.contains(target)
+    ) {
+      return
+    }
+
+    const elements = SelectorEngine.focusableChildren(trapElement)
+
+    if (elements.length === 0) {
+      trapElement.focus()
+    } else if (this._lastTabNavDirection === TAB_NAV_BACKWARD) {
+      elements[elements.length - 1].focus()
+    } else {
+      elements[0].focus()
+    }
+  }
+
+  _handleKeydown(event) {
+    if (event.key !== TAB_KEY) {
+      return
+    }
+
+    this._lastTabNavDirection = event.shiftKey ? TAB_NAV_BACKWARD : TAB_NAV_FORWARD
+  }
+
+  _getConfig(config) {
+    config = {
+      ...Default,
+      ...(typeof config === 'object' ? config : {})
+    }
+    typeCheckConfig(NAME, config, DefaultType)
+    return config
+  }
+}
+
+export default FocusTrap