paper-toast.html

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<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../paper-styles/typography.html">

<dom-module id="paper-toast">
  <style>
    :host {
      display: inline-block;
      position: fixed;

      background: #323232;
      color: #f1f1f1;
      min-height: 48px;
      min-width: 288px;
      padding: 16px 24px 12px;
      box-sizing: border-box;
      box-shadow: 0 2px 5px 0 rgba(0, 0, 0, 0.26);
      border-radius: 2px;
      bottom: 12px;
      left: 12px;
      font-size: 14px;
      cursor: default;

      -webkit-transition: visibility 0.3s, -webkit-transform 0.3s;
      transition: visibility 0.3s, transform 0.3s;

      -webkit-transform: translateY(100px);
      transform: translateY(100px);

      visibility: hidden;
    }

    :host(.capsule) {
      border-radius: 24px;
    }

    :host(.fit-bottom) {
      bottom: 0;
      left: 0;
      width: 100%;
      min-width: 0;
      border-radius: 0;
    }

    :host(.paper-toast-open){
      visibility: visible;

      -webkit-transform: translateY(0px);
      transform: translateY(0px);
    }
  </style>
  <template>
    <span id="label" role="alert" aria-live="assertive">{{text}}</span>
    <content></content>
  </template>
</dom-module>
<script>
(function() {

  var PaperToast = Polymer({
    is: 'paper-toast',

    properties: {
      /**
       * The duration in milliseconds to show the toast.
       */
      duration: {
        type: Number,
        value: 3000
      },

      /**
       * The text to display in the toast.
       */
      text: {
        type: String,
        value: ""
      },

      visible: {
        type: Boolean,
        readOnly: true,
        value: false,
        observer: '_visibleChanged'
      }
    },

    hostAttributes: {
      role: 'alert',
      'aria-live': 'assertive'
    },

    ready: function() {
      this.async(function() {
        this.hide();
      });
    },

    /**
     * Show the toast.
     * @method show
     */
    show: function() {
      if (PaperToast.currentToast) {
        PaperToast.currentToast.hide();
      }
      PaperToast.currentToast = this;
      this._setVisible(true);
      this._ariaAnnounce();
      this.debounce('hide', this.hide, this.duration);
    },

    /**
     * Hide the toast
     * @return {[type]} [description]
     */
    hide: function() {
      this.setAttribute('aria-live', 'off');
      this.$.label.removeAttribute('role');
      this.$.label.removeAttribute('aria-live');

      this._setVisible(false);
    },

    /**
     * Toggle the opened state of the toast.
     * @method toggle
     */
    toggle: function() {
      if (!this.visible) {
        this.show();
      } else {
        this.hide();
      }
    },

    _visibleChanged: function(visible) {
      this.toggleClass('paper-toast-open', visible);
    },

    _ariaAnnounce: function() {
      // Allow me to explain:
      // http://www.paciellogroup.com/blog/2012/06/html5-accessibility-chops-aria-rolealert-browser-support/
      var oldText = this.text;

      this.setAttribute('aria-live', 'assertive');
      this.$.label.setAttribute('role', 'alert');
      this.$.label.setAttribute('aria-live', 'assertive');

      this.text = '';
      this.text = oldText;

      this.$.label.style.visibility = 'hidden';
      this.$.label.style.visibility = 'visible';
    }

  });

  PaperToast.currentToast = null;

})();
</script>