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<!--
@license
Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-->
<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../iron-selector/iron-multi-selectable.html">
<link rel="import" href="../iron-a11y-keys-behavior/iron-a11y-keys-behavior.html">
<script>
/**
* `Polymer.IronMenuBehavior` implements accessible menu behavior.
*
* @demo demo/index.html
* @polymerBehavior Polymer.IronMenuBehavior
*/
Polymer.IronMenuBehaviorImpl = {
properties: {
/**
* Returns the currently focused item.
*
* @attribute focusedItem
* @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.
*
* @attribute attrForItemTitle
* @type String
*/
attrForItemTitle: {
type: String
}
},
hostAttributes: {
'role': 'menu',
'tabindex': '0'
},
observers: [
'_updateMultiselectable(multi)'
],
listeners: {
'focus': '_onFocus',
'keydown': '_onKeydown'
},
keyBindings: {
'up': '_onUpKey',
'down': '_onDownKey',
'esc': '_onEscKey',
'enter': '_onEnterKey',
'shift+tab:keydown': '_onShiftTabDown'
},
_updateMultiselectable: function(multi) {
if (multi) {
this.setAttribute('aria-multiselectable', 'true');
} else {
this.removeAttribute('aria-multiselectable');
}
},
_onShiftTabDown: function() {
var oldTabIndex;
Polymer.IronMenuBehaviorImpl._shiftTabPressed = true;
oldTabIndex = this.getAttribute('tabindex');
this.setAttribute('tabindex', '-1');
this.async(function() {
this.setAttribute('tabindex', oldTabIndex);
Polymer.IronMenuBehaviorImpl._shiftTabPressed = false;
// Note: polymer/polymer#1305
}, 1);
},
_applySelection: function(item, isSelected) {
if (isSelected) {
item.setAttribute('aria-selected', 'true');
} else {
item.removeAttribute('aria-selected');
}
Polymer.IronSelectableBehavior._applySelection.apply(this, arguments);
},
_focusedItemChanged: function(focusedItem, old) {
old && old.setAttribute('tabindex', '-1');
if (focusedItem) {
focusedItem.setAttribute('tabindex', '0');
focusedItem.focus();
}
},
select: function(value) {
if (this._defaultFocusAsync) {
this.cancelAsync(this._defaultFocusAsync);
this._defaultFocusAsync = null;
}
var item = this._valueToItem(value);
this._setFocusedItem(item);
Polymer.IronMultiSelectableBehaviorImpl.select.apply(this, arguments);
},
_onFocus: function(event) {
if (Polymer.IronMenuBehaviorImpl._shiftTabPressed) {
return;
}
// do not focus the menu itself
this.blur();
// clear the cached focus item
this._setFocusedItem(null);
this._defaultFocusAsync = this.async(function() {
// focus the selected item when the menu receives focus, or the first item
// if no item is selected
var selectedItem = this.multi ? (this.selectedItems && this.selectedItems[0]) : this.selectedItem;
if (selectedItem) {
this._setFocusedItem(selectedItem);
} else {
this._setFocusedItem(this.items[0]);
}
// async 100ms to wait for `select` to get called from `_itemActivate`
}, 100);
},
_onUpKey: function() {
// up and down arrows moves the focus
this._focusPrevious();
},
_onDownKey: function() {
this._focusNext();
},
_onEscKey: function() {
// esc blurs the control
this.focusedItem.blur();
},
_onEnterKey: function(event) {
// enter activates the item unless it is disabled
this._activateFocused(event.detail.keyboardEvent);
},
_onKeydown: function(event) {
if (this.keyboardEventMatchesKeys(event, 'up down esc enter')) {
return;
}
// all other keys focus the menu item starting with that character
this._focusWithKeyboardEvent(event);
},
_focusWithKeyboardEvent: function(event) {
for (var i = 0, item; item = this.items[i]; i++) {
var attr = this.attrForItemTitle || 'textContent';
var title = item[attr] || item.getAttribute(attr);
if (title && title.trim().charAt(0).toLowerCase() === String.fromCharCode(event.keyCode).toLowerCase()) {
this._setFocusedItem(item);
break;
}
}
},
_activateFocused: function(event) {
if (!this.focusedItem.hasAttribute('disabled')) {
this._activateHandler(event);
}
},
_focusPrevious: function() {
var length = this.items.length;
var index = (Number(this.indexOf(this.focusedItem)) - 1 + length) % length;
this._setFocusedItem(this.items[index]);
},
_focusNext: function() {
var index = (Number(this.indexOf(this.focusedItem)) + 1) % this.items.length;
this._setFocusedItem(this.items[index]);
}
};
Polymer.IronMenuBehaviorImpl._shiftTabPressed = false;
/** @polymerBehavior Polymer.IronMenuBehavior */
Polymer.IronMenuBehavior = [
Polymer.IronMultiSelectableBehavior,
Polymer.IronA11yKeysBehavior,
Polymer.IronMenuBehaviorImpl
];
</script>
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