SGH / COMPONENTS

<!--
@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="../paper-styles/color.html">
<link rel="import" href="../iron-flex-layout/iron-flex-layout.html">

<!--
Element providing material design circular spinner.

    <paper-spinner active></paper-spinner>

The default spinner cycles between four layers of colors; by default they are
blue, red, yellow and green. It can be customized so that it uses one color only
by setting all the layer colors to the same value.

### Accessibility

Alt attribute should be set to provide adequate context for accessibility. If not provided,
it defaults to 'loading'.
Empty alt can be provided to mark the element as decorative if alternative content is provided
in another form (e.g. a text block following the spinner).

    <paper-spinner alt="Loading contacts list" active></paper-spinner>

### Styling

The following custom properties and mixins are available for styling:

Custom property | Description | Default
----------------|-------------|----------
`--paper-spinner-layer-1-color` | Color of the first spinner rotation | `--google-blue-500`
`--paper-spinner-layer-2-color` | Color of the second spinner rotation | `--google-red-500`
`--paper-spinner-layer-3-color` | Color of the third spinner rotation | `--google-yellow-500`
`--paper-spinner-layer-4-color` | Color of the fourth spinner rotation | `--google-green-500`

@group Paper Elements
@element paper-spinner
@hero hero.svg
@demo demo/index.html
-->

<dom-module id="paper-spinner">

  <link rel="import" type="css" href="paper-spinner.css">

  <template>

    <div id="spinnerContainer" class-name="[[_spinnerContainerClassName]]">
      <div class="spinner-layer layer-1">
        <div class="circle-clipper left">
          <div class="circle"></div>
        </div><div class="gap-patch">
          <div class="circle"></div>
        </div><div class="circle-clipper right">
          <div class="circle"></div>
        </div>
      </div>

      <div class="spinner-layer layer-2">
        <div class="circle-clipper left">
          <div class="circle"></div>
        </div><div class="gap-patch">
          <div class="circle"></div>
        </div><div class="circle-clipper right">
          <div class="circle"></div>
        </div>
      </div>

      <div class="spinner-layer layer-3">
        <div class="circle-clipper left">
          <div class="circle"></div>
        </div><div class="gap-patch">
          <div class="circle"></div>
        </div><div class="circle-clipper right">
          <div class="circle"></div>
        </div>
      </div>

      <div class="spinner-layer layer-4">
        <div class="circle-clipper left">
          <div class="circle"></div>
        </div><div class="gap-patch">
          <div class="circle"></div>
        </div><div class="circle-clipper right">
          <div class="circle"></div>
        </div>
      </div>
    </div>

  </template>

  <script>

    Polymer({

      is: 'paper-spinner',

      listeners: {
        'animationend': 'reset',
        'webkitAnimationEnd': 'reset'
      },

      properties: {

        /**
         * Displays the spinner.
         *
         * @attribute active
         * @type boolean
         * @default false
         */
        active: {
          type: Boolean,
          value: false,
          reflectToAttribute: true,
          observer: '_activeChanged'
        },

        /**
         * Alternative text content for accessibility support.
         * If alt is present, it will add an aria-label whose content matches alt when active.
         * If alt is not present, it will default to 'loading' as the alt value.
         *
         * @attribute alt
         * @type string
         * @default 'loading'
         */
        alt: {
          type: String,
          value: 'loading',
          observer: '_altChanged'
        },

        /**
         * True when the spinner is going from active to inactive. This is represented by a fade
         * to 0% opacity to the user.
         */
        _coolingDown: {
          type: Boolean,
          value: false
        },

        _spinnerContainerClassName: {
          type: String,
          computed: '_computeSpinnerContainerClassName(active, _coolingDown)'
        }

      },

      _computeSpinnerContainerClassName: function(active, coolingDown) {
        return [
          active || coolingDown ? 'active' : '',
          coolingDown ? 'cooldown' : ''
        ].join(' ');
      },

      _activeChanged: function(active, old) {
        this._setAriaHidden(!active);
        if (!active && old) {
          this._coolingDown = true;
        }
      },

      _altChanged: function(alt) {
        // user-provided `aria-label` takes precedence over prototype default
        if (alt === this.getPropertyInfo('alt').value) {
          this.alt = this.getAttribute('aria-label') || alt;
        } else {
          this._setAriaHidden(alt==='');
          this.setAttribute('aria-label', alt);
        }
      },

      _setAriaHidden: function(hidden) {
        var attr = 'aria-hidden';
        if (hidden) {
          this.setAttribute(attr, 'true');
        } else {
          this.removeAttribute(attr);
        }
      },

      reset: function() {
        this.active = false;
        this._coolingDown = false;
      }

    });

  </script>

</dom-module>