MD-Settings A11y: Disable radio list if all options are disabled.

third_party/polymer/v1_0/components-chromium/iron-menu-behavior/iron-menu-behavior-extracted.js

 /**
    * `Polymer.IronMenuBehavior` implements accessible menu behavior.
    *
    * @demo demo/index.html
    * @polymerBehavior Polymer.IronMenuBehavior
    */
   Polymer.IronMenuBehaviorImpl = {
 
     properties: {
 
       /**
        * Returns the currently focused item.
        * @type {?Object}
        */
       focusedItem: {
         observer: '_focusedItemChanged',
         readOnly: true,
         type: Object
       },
 
       /**
        * The attribute to use on menu items to look up the item title. Typing the first
        * letter of an item when the menu is open focuses that item. If unset, `textContent`
        * will be used.
        */
       attrForItemTitle: {
         type: String
+      },
+
+      disabled: {
+        type: Boolean,
+        value: false,
+        reflectToAttribute: true,
+        observer: '_disableTabindex',
       }
     },
 
     hostAttributes: {
       'role': 'menu',
-      'tabindex': '0'
     },
 
     observers: [
       '_updateMultiselectable(multi)'
     ],
 
     listeners: {
       'focus': '_onFocus',
       'keydown': '_onKeydown',
       'iron-items-changed': '_onIronItemsChanged'
@@ skipping 32 matching lines @@
     /**
      * Resets all tabindex attributes to the appropriate value based on the
      * current selection state. The appropriate value is `0` (focusable) for
      * the default selected item, and `-1` (not keyboard focusable) for all
      * other items.
      */
     _resetTabindices: function() {
       var selectedItem = this.multi ? (this.selectedItems && this.selectedItems[0]) : this.selectedItem;
 
       this.items.forEach(function(item) {
-        item.setAttribute('tabindex', item === selectedItem ? '0' : '-1');
+        // Don't enable tab index if an item is disabled, even if it's selected.
+        if (item === selectedItem && !selectedItem.hasAttribute('disabled') && !this.disabled)
+          item.setAttribute('tabindex', 0);
+        else
+          item.removeAttribute('tabindex');
       }, this);
     },
 
     /**
      * Sets appropriate ARIA based on whether or not the menu is meant to be
      * multi-selectable.
      *
      * @param {boolean} multi True if the menu should be multi-selectable.
      */
     _updateMultiselectable: function(multi) {
@@ skipping 90 matching lines @@
 
     /**
      * Discretely updates tabindex values among menu items as the focused item
      * changes.
      *
      * @param {Element} focusedItem The element that is currently focused.
      * @param {?Element} old The last element that was considered focused, if
      * applicable.
      */
     _focusedItemChanged: function(focusedItem, old) {
-      old && old.setAttribute('tabindex', '-1');
-      if (focusedItem) {
+      old && old.removeAttribute('tabindex');
+      if (focusedItem && !focusedItem.hasAttribute('disabled') && !this.disabled) {
         focusedItem.setAttribute('tabindex', '0');
         focusedItem.focus();
       }
     },
 
     /**
      * A handler that responds to mutation changes related to the list of items
      * in the menu.
      *
      * @param {CustomEvent} event An event containing mutation records as its
      * detail.
      */
     _onIronItemsChanged: function(event) {
       if (event.detail.addedNodes.length) {
         this._resetTabindices();
       }
     },
 
     /**
      * Handler that is called when a shift+tab keypress is detected by the menu.
      *
      * @param {CustomEvent} event A key combination event.
      */
     _onShiftTabDown: function(event) {
-      var oldTabIndex = this.getAttribute('tabindex');
+      var couldTab = this.getAttribute('tabindex') == 0;
 
       Polymer.IronMenuBehaviorImpl._shiftTabPressed = true;
 
       this._setFocusedItem(null);
 
-      this.setAttribute('tabindex', '-1');
+      this._disableTabindex(true);
 
       this.async(function() {
-        this.setAttribute('tabindex', oldTabIndex);
+      this._disableTabindex(!couldTab);

[Dan Beam, 2017/03/17 23:58:53]

indent off

[hcarmona, 2017/03/18 01:05:07]

Done.

         Polymer.IronMenuBehaviorImpl._shiftTabPressed = false;
         // NOTE(cdata): polymer/polymer#1305
       }, 1);
     },
 
     /**
      * Handler that is called when the menu receives focus.
      *
      * @param {FocusEvent} event A focus event.
      */
@@ skipping 69 matching lines @@
         // all other keys focus the menu item starting with that character
         this._focusWithKeyboardEvent(event);
       }
       event.stopPropagation();
     },
 
     // override _activateHandler
     _activateHandler: function(event) {
       Polymer.IronSelectableBehavior._activateHandler.call(this, event);
       event.stopPropagation();
+    },
+
+    /**
+     * Updates this element's tab index when it's enabled/disabled.
+     * @param {boolean} disabled
+     */
+    _disableTabindex: function(disabled) {
+      if (disabled)
+        this.removeAttribute('tabindex');  // No tabindex means not tab-able or select-able.
+      else
+        this.setAttribute('tabindex', 0);  // tabindex of 0 means tab-able.
     }
   };
 
   Polymer.IronMenuBehaviorImpl._shiftTabPressed = false;
 
   /** @polymerBehavior Polymer.IronMenuBehavior */
   Polymer.IronMenuBehavior = [
     Polymer.IronMultiSelectableBehavior,
     Polymer.IronA11yKeysBehavior,
     Polymer.IronMenuBehaviorImpl
-  ];
+  ];