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<link rel=“import” href=“../polymer/polymer.html”>

<script>

/**
 * `IronResizableBehavior` is a behavior that can be used in Polymer elements to
 * coordinate the flow of resize events between "resizers" (elements that control the
 * size or hidden state of their children) and "resizables" (elements that need to be
 * notified when they are resized or un-hidden by their parents in order to take
 * action on their new measurements).
 *
 * Elements that perform measurement should add the `IronResizableBehavior` behavior to
 * their element definition and listen for the `iron-resize` event on themselves.
 * This event will be fired when they become showing after having been hidden,
 * when they are resized explicitly by another resizable, or when the window has been
 * resized.
 *
 * Note, the `iron-resize` event is non-bubbling.
 *
 * @polymerBehavior Polymer.IronResizableBehavior
 * @demo demo/index.html
 **/
Polymer.IronResizableBehavior = {
  properties: {
    /**
     * The closest ancestor element that implements `IronResizableBehavior`.
     */
    _parentResizable: {
      type: Object,
      observer: '_parentResizableChanged'
    },

    /**
     * True if this element is currently notifying its descedant elements of
     * resize.
     */
    _notifyingDescendant: {
      type: Boolean,
      value: false
    }
  },

  listeners: {
    'iron-request-resize-notifications': '_onIronRequestResizeNotifications'
  },

  created: function() {
    // We don't really need property effects on these, and also we want them
    // to be created before the `_parentResizable` observer fires:
    this._interestedResizables = [];
    this._boundNotifyResize = this.notifyResize.bind(this);
  },

  attached: function() {
    this.fire('iron-request-resize-notifications', null, {
      node: this,
      bubbles: true,
      cancelable: true
    });

    if (!this._parentResizable) {
      window.addEventListener('resize', this._boundNotifyResize);
      this.notifyResize();
    }
  },

  detached: function() {
    if (this._parentResizable) {
      this._parentResizable.stopResizeNotificationsFor(this);
    } else {
      window.removeEventListener('resize', this._boundNotifyResize);
    }

    this._parentResizable = null;
  },

  /**
   * Can be called to manually notify a resizable and its descendant
   * resizables of a resize change.
   */
  notifyResize: function() {
    if (!this.isAttached) {
      return;
    }

    this._interestedResizables.forEach(function(resizable) {
      if (this.resizerShouldNotify(resizable)) {
        this._notifyDescendant(resizable);
      }
    }, this);

    this._fireResize();
  },

  /**
   * Used to assign the closest resizable ancestor to this resizable
   * if the ancestor detects a request for notifications.
   */
  assignParentResizable: function(parentResizable) {
    this._parentResizable = parentResizable;
  },

  /**
   * Used to remove a resizable descendant from the list of descendants
   * that should be notified of a resize change.
   */
  stopResizeNotificationsFor: function(target) {
    var index = this._interestedResizables.indexOf(target);

    if (index > -1) {
      this._interestedResizables.splice(index, 1);
      this.unlisten(target, 'iron-resize', '_onDescendantIronResize');
    }
  },

  /**
   * This method can be overridden to filter nested elements that should or
   * should not be notified by the current element. Return true if an element
   * should be notified, or false if it should not be notified.
   *
   * @param {HTMLElement} element A candidate descendant element that
   * implements `IronResizableBehavior`.
   * @return {boolean} True if the `element` should be notified of resize.
   */
  resizerShouldNotify: function(element) { return true; },

  _onDescendantIronResize: function(event) {
    if (this._notifyingDescendant) {
      event.stopPropagation();
      return;
    }

    // NOTE(cdata): In ShadowDOM, event retargetting makes echoing of the
    // otherwise non-bubbling event "just work." We do it manually here for
    // the case where Polymer is not using shadow roots for whatever reason:
    if (!Polymer.Settings.useShadow) {
      this._fireResize();
    }
  },

  _fireResize: function() {
    this.fire('iron-resize', null, {
      node: this,
      bubbles: false
    });
  },

  _onIronRequestResizeNotifications: function(event) {
    var target = event.path ? event.path[0] : event.target;

    if (target === this) {
      return;
    }

    if (this._interestedResizables.indexOf(target) === -1) {
      this._interestedResizables.push(target);
      this.listen(target, 'iron-resize', '_onDescendantIronResize');
    }

    target.assignParentResizable(this);
    this._notifyDescendant(target);

    event.stopPropagation();
  },

  _parentResizableChanged: function(parentResizable) {
    if (parentResizable) {
      window.removeEventListener('resize', this._boundNotifyResize);
    }
  },

  _notifyDescendant: function(descendant) {
    // NOTE(cdata): In IE10, attached is fired on children first, so it's
    // important not to notify them if the parent is not attached yet (or
    // else they will get redundantly notified when the parent attaches).
    if (!this.isAttached) {
      return;
    }

    this._notifyingDescendant = true;
    descendant.notifyResize();
    this._notifyingDescendant = false;
  }
};

</script>