iron-overlay-renderer.html

<!--
@license
Copyright (c) 2016 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-element.html">
<link rel="import" href="iron-overlay-renderer-shared-styles.html">

<!--
`iron-overlay-renderer` renders the overlay content in the center of the screen,
and handles the switch from opened state to closed state & viceversa.

### Styling

`iron-overlay` sets its renderer attribute `data-overlay` to its id, so that
styling can be done like this:

    <style is="custom-style">
      iron-overlay-renderer {
        --iron-overlay-background-color: yellow;
      }
      [data-overlay="overlay1"] {
        --iron-overlay-background-color: orange;
      }
    </style>

    <iron-overlay-container></iron-overlay-container>

    <iron-overlay>
      <template>Overlay Content</template>
    </iron-overlay>
    <iron-overlay id="overlay1">
      <template>Overlay 1 Content</template>
    </iron-overlay>

@demo demo/index.html
-->

<dom-module id="iron-overlay-renderer">
  <template strip-whitespace>
    <style include="iron-overlay-renderer-shared-styles"></style>
    <div id="backdrop"></div>
    <div id="overlay">
      <slot></slot>
    </div>
  </template>

  <script>
    (() => {
      'use strict';

      class IronOverlayRenderer extends Polymer.Element {

        static get is() {
          return 'iron-overlay-renderer';
        }

        static get properties() {
          return {
            /**
             * True if the overlay is currently displayed.
             */
            opened: {
              type: Boolean,
              observer: '_openedChanged'
            },

            /**
             * True if the overlay has open/close animation.
             */
            animated: {
              type: Boolean
            },

            /**
             * True if the overlay should have a backdrop.
             */
            withBackdrop: {
              type: Boolean
            },

            /**
             * Is true during the transition from close to open and open to close.
             */
            transitioning: {
              type: Boolean,
              notify: true,
              readOnly: true
            }
          };
        }

        constructor() {
          super();
          // For a performant transition from open to close and close to open.
          this._pendingRAF = null;
        }

        ready() {
          super.ready();
          // If delegatesFocus is not supported or class is extended but doesn't
          // have a shadow root, make the element focusable but not tabbable.
          if (!this.shadowRoot || !this.shadowRoot.delegatesFocus) {
            this.setAttribute('tabindex', '-1');
          }
          this.$.overlay.addEventListener('transitionend', this._onTransitionEnd.bind(this));
        }

        /**
         * Overridden from Polymer.Element to ensure the shadow root delegates focus.
         * See Polymer/polymer#3988
         * @protected
         */
        _attachDom(dom) {
          // Create shadowRoot only when there is content to be added
          if (dom && this.attachShadow && !this.shadowRoot) {
            this.attachShadow({
              mode: 'open',
              delegatesFocus: true
            });
          }
          return super._attachDom(dom);
        }

        /**
         * Tasks to be performed to actually open/close. Override this to play
         * animations, and call `_finishRenderOpenedChanged()` when those are done.
         * @protected
         */
        _renderOpenedChanged() {
          // Doesn't wait for animations if animated is false.
          if (!this.animated) {
            this._finishRenderOpenedChanged();
          }
        }

        /**
         * @protected
         */
        _finishRenderOpenedChanged() {
          this._setTransitioning(false);
        }

        /**
         * @param {boolean} opened
         */
        _openedChanged(opened) {
          this._onNextAF(this._startRenderOpenedChanged);
        }

        /**
         * Starts the update from open to closed & viceversa.
         */
        _startRenderOpenedChanged() {
          this._setTransitioning(true);
          // Update interactions with element.
          this.style.pointerEvents = this.opened ? '' : 'none';
          // Need to force layout for any animation to trigger.
          if (this.animated) {
            this._forceLayout();
          }
          // Update classes for overlay and backdrop.
          this.$.overlay.classList.toggle('opened', this.opened);
          // Check if there is a backdrop in the shadow dom.
          this.$.backdrop && this.$.backdrop.classList.toggle('opened', this.opened);
          this._renderOpenedChanged();
        }

        /**
         * Forces layout.
         */
        _forceLayout() {
          return this.offsetWidth;
        }

        /**
         * Callback for transitionend, ends the animation.
         * @param {!Event} event
         */
        _onTransitionEnd(event) {
          if (event.target === this.$.overlay && this.transitioning) {
            // Since there might be multiple animations (e.g. opacity + transition),
            // call finish function only once (reuse RAF).
            this._onNextAF(this._finishRenderOpenedChanged);
          }
        }

        /**
         * Executes the callback at the next available animation frame.
         * @param {!Function} callback Its scope will be the renderer itself
         */
        _onNextAF(callback) {
          this._pendingRAF && window.cancelAnimationFrame(this._pendingRAF);
          const self = this;
          this._pendingRAF = window.requestAnimationFrame(function nextAnimationFrame() {
            self._pendingRAF = null;
            callback.call(self);
          });
        }

      }

      Polymer.IronOverlayRenderer = IronOverlayRenderer;
      customElements.define(IronOverlayRenderer.is, IronOverlayRenderer);

    })();
  </script>
</dom-module>