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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">
<!--
`iron-a11y-announcer` is a singleton element that is intended to add a11y
to features that require on-demand announcement from screen readers. In
order to make use of the announcer, it is best to request its availability
in the announcing element.
Example:
Polymer({
is: 'x-chatty',
attached: function() {
// This will create the singlton element if it has not
// been created yet:
Polymer.IronA11yAnnouncer.requestAvailability();
}
});
After the `iron-a11y-announcer` has been made available, elements can
make announces by firing bubbling `iron-announce` events.
Example:
this.fire('iron-announce', {
text: 'This is an announcement!'
}, { bubbles: true });
Note: announcements are only audible if you have a screen reader enabled.
@group Iron Elements
@demo demo/index.html
-->
<dom-module id="iron-a11y-announcer">
<style>
:host {
display: inline-block;
position: fixed;
clip: rect(0px,0px,0px,0px);
}
</style>
<template>
<span aria-live$="[[mode]]">[[_text]]</span>
</template>
<script>
(function() {
'use strict';
Polymer.IronA11yAnnouncer = Polymer({
is: 'iron-a11y-announcer',
properties: {
/**
* The value of mode is used to set the `aria-live` attribute
* for the element that will be announced. Valid values are: `off`,
* `polite` and `assertive`.
*/
mode: {
type: String,
value: 'polite'
},
_text: {
type: String,
value: ''
}
},
created: function() {
if (!Polymer.IronA11yAnnouncer.instance) {
Polymer.IronA11yAnnouncer.instance = this;
}
document.body.addEventListener('iron-announce', this._onIronAnnounce.bind(this));
},
/**
* Cause a text string to be announced by screen readers.
*
* @param {string} text The text that should be announced.
*/
announce: function(text) {
this._text = '';
this.async(function() {
this._text = text;
}, 100);
},
_onIronAnnounce: function(event) {
if (event.detail && event.detail.text) {
this.announce(event.detail.text);
}
}
});
Polymer.IronA11yAnnouncer.instance = null;
Polymer.IronA11yAnnouncer.requestAvailability = function() {
if (!Polymer.IronA11yAnnouncer.instance) {
Polymer.IronA11yAnnouncer.instance = document.createElement('iron-a11y-announcer');
}
document.body.appendChild(Polymer.IronA11yAnnouncer.instance);
};
})();
</script>
</dom-module>
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