iron-overlay-backdrop.html

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@license
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This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
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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-overlay-manager.html">

<!--
`iron-overlay-backdrop` is a backdrop used by `Polymer.IronOverlayBehavior`. It should be a
singleton.

### Styling

The following custom properties and mixins are available for styling.

Custom property | Description | Default
-------------------------------------------|------------------------|---------
`--iron-overlay-backdrop-background-color` | Backdrop background color                                     | #000
`--iron-overlay-backdrop-opacity`          | Backdrop opacity                                              | 0.6
`--iron-overlay-backdrop`                  | Mixin applied to `iron-overlay-backdrop`.                      | {}
`--iron-overlay-backdrop-opened`           | Mixin applied to `iron-overlay-backdrop` when it is displayed | {}
-->

<dom-module id="iron-overlay-backdrop">

  <style>

    :host {
      position: fixed;
      top: 0;
      left: 0;
      width: 100vw;
      height: 100vh;
      background-color: var(--iron-overlay-backdrop-background-color, #000);
      opacity: 0;
      transition: opacity 0.2s;

      @apply(--iron-overlay-backdrop);
    }

    :host([opened]) {
      opacity: var(--iron-overlay-backdrop-opacity, 0.6);

      @apply(--iron-overlay-backdrop-opened);
    }

  </style>

  <template>
    <content></content>
  </template>

</dom-module>

<script>

(function() {

  Polymer({

    is: 'iron-overlay-backdrop',

    properties: {

      /**
       * Returns true if the backdrop is opened.
       */
      opened: {
        readOnly: true,
        reflectToAttribute: true,
        type: Boolean,
        value: false
      },

      _manager: {
        type: Object,
        value: Polymer.IronOverlayManager
      }

    },

    /**
     * Appends the backdrop to document body and sets its `z-index` to be below the latest overlay.
     */
    prepare: function() {
      if (!this.parentNode) {
        Polymer.dom(document.body).appendChild(this);
        this.style.zIndex = this._manager.currentOverlayZ() - 1;
      }
    },

    /**
     * Shows the backdrop if needed.
     */
    open: function() {
      // only need to make the backdrop visible if this is called by the first overlay with a backdrop
      if (this._manager.getBackdrops().length < 2) {
        this._setOpened(true);
      }
    },

    /**
     * Hides the backdrop if needed.
     */
    close: function() {
      // only need to make the backdrop invisible if this is called by the last overlay with a backdrop
      if (this._manager.getBackdrops().length < 2) {
        this._setOpened(false);
      }
    },

    /**
     * Removes the backdrop from document body if needed.
     */
    complete: function() {
      // only remove the backdrop if there are no more overlays with backdrops
      if (this._manager.getBackdrops().length === 0 && this.parentNode) {
        Polymer.dom(this.parentNode).removeChild(this);
      }
    }

  });

})();

</script>