components/iron-dropdown/iron-dropdown.html

<!--
@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="../iron-resizable-behavior/iron-resizable-behavior.html">
<link rel="import" href="../iron-a11y-keys-behavior/iron-a11y-keys-behavior.html">
<link rel="import" href="../iron-behaviors/iron-control-state.html">
<link rel="import" href="../iron-overlay-behavior/iron-overlay-behavior.html">
<link rel="import" href="../neon-animation/neon-animation-runner-behavior.html">
<link rel="import" href="../neon-animation/animations/opaque-animation.html">
<link rel="import" href="iron-dropdown-scroll-manager.html">

<!--
`<iron-dropdown>` is a generalized element that is useful when you have
hidden content (`.dropdown-content`) that is revealed due to some change in
state that should cause it to do so.

Note that this is a low-level element intended to be used as part of other
composite elements that cause dropdowns to be revealed.

Examples of elements that might be implemented using an `iron-dropdown`
include comboboxes, menubuttons, selects. The list goes on.

The `<iron-dropdown>` element exposes attributes that allow the position
of the `.dropdown-content` relative to the `.dropdown-trigger` to be
configured.

    <iron-dropdown horizontal-align="right" vertical-align="top">
      <div class="dropdown-content">Hello!</div>
    </iron-dropdown>

In the above example, the `<div>` with class `.dropdown-content` will be
hidden until the dropdown element has `opened` set to true, or when the `open`
method is called on the element.

@demo demo/index.html
-->

<dom-module id="iron-dropdown">
  <template>
    <style>
      :host {
        position: fixed;
      }

      #contentWrapper ::content > * {
        overflow: auto;
      }

      #contentWrapper.animating ::content > * {
        overflow: hidden;
      }
    </style>

    <div id="contentWrapper">
      <content id="content" select=".dropdown-content"></content>
    </div>
  </template>

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

      Polymer({
        is: 'iron-dropdown',

        behaviors: [
          Polymer.IronControlState,
          Polymer.IronA11yKeysBehavior,
          Polymer.IronOverlayBehavior,
          Polymer.NeonAnimationRunnerBehavior
        ],

        properties: {
          /**
           * The orientation against which to align the dropdown content
           * horizontally relative to the dropdown trigger.
           * Overridden from `Polymer.IronFitBehavior`.
           */
          horizontalAlign: {
            type: String,
            value: 'left',
            reflectToAttribute: true
          },

          /**
           * The orientation against which to align the dropdown content
           * vertically relative to the dropdown trigger.
           * Overridden from `Polymer.IronFitBehavior`.
           */
          verticalAlign: {
            type: String,
            value: 'top',
            reflectToAttribute: true
          },

          /**
           * An animation config. If provided, this will be used to animate the
           * opening of the dropdown. Pass an Array for multiple animations.
           * See `neon-animation` documentation for more animation configuration
           * details.
           */
          openAnimationConfig: {
            type: Object
          },

          /**
           * An animation config. If provided, this will be used to animate the
           * closing of the dropdown. Pass an Array for multiple animations.
           * See `neon-animation` documentation for more animation configuration
           * details.
           */
          closeAnimationConfig: {
            type: Object
          },

          /**
           * If provided, this will be the element that will be focused when
           * the dropdown opens.
           */
          focusTarget: {
            type: Object
          },

          /**
           * Set to true to disable animations when opening and closing the
           * dropdown.
           */
          noAnimations: {
            type: Boolean,
            value: false
          },

          /**
           * By default, the dropdown will constrain scrolling on the page
           * to itself when opened.
           * Set to true in order to prevent scroll from being constrained
           * to the dropdown when it opens.
           */
          allowOutsideScroll: {
            type: Boolean,
            value: false
          },

          /**
           * Callback for scroll events.
           * @type {Function}
           * @private
           */
          _boundOnCaptureScroll: {
            type: Function,
            value: function() {
              return this._onCaptureScroll.bind(this);
            }
          }
        },

        listeners: {
          'neon-animation-finish': '_onNeonAnimationFinish'
        },

        observers: [
          '_updateOverlayPosition(positionTarget, verticalAlign, horizontalAlign, verticalOffset, horizontalOffset)'
        ],

        /**
         * The element that is contained by the dropdown, if any.
         */
        get containedElement() {
          return Polymer.dom(this.$.content).getDistributedNodes()[0];
        },

        /**
         * The element that should be focused when the dropdown opens.
         * @deprecated
         */
        get _focusTarget() {
          return this.focusTarget || this.containedElement;
        },

        ready: function() {
          // Memoized scrolling position, used to block scrolling outside.
          this._scrollTop = 0;
          this._scrollLeft = 0;
          // Used to perform a non-blocking refit on scroll.
          this._refitOnScrollRAF = null;
        },

        attached: function () {
          if (!this.sizingTarget || this.sizingTarget === this) {
            this.sizingTarget = this.containedElement || this;
          }
        },

        detached: function() {
          this.cancelAnimation();
          document.removeEventListener('scroll', this._boundOnCaptureScroll);
          Polymer.IronDropdownScrollManager.removeScrollLock(this);
        },

        /**
         * Called when the value of `opened` changes.
         * Overridden from `IronOverlayBehavior`
         */
        _openedChanged: function() {
          if (this.opened && this.disabled) {
            this.cancel();
          } else {
            this.cancelAnimation();
            this._updateAnimationConfig();
            this._saveScrollPosition();
            if (this.opened) {
              document.addEventListener('scroll', this._boundOnCaptureScroll);
              !this.allowOutsideScroll && Polymer.IronDropdownScrollManager.pushScrollLock(this);
            } else {
              document.removeEventListener('scroll', this._boundOnCaptureScroll);
              Polymer.IronDropdownScrollManager.removeScrollLock(this);
            }
            Polymer.IronOverlayBehaviorImpl._openedChanged.apply(this, arguments);
          }
        },

        /**
         * Overridden from `IronOverlayBehavior`.
         */
        _renderOpened: function() {
          if (!this.noAnimations && this.animationConfig.open) {
            this.$.contentWrapper.classList.add('animating');
            this.playAnimation('open');
          } else {
            Polymer.IronOverlayBehaviorImpl._renderOpened.apply(this, arguments);
          }
        },

        /**
         * Overridden from `IronOverlayBehavior`.
         */
        _renderClosed: function() {

          if (!this.noAnimations && this.animationConfig.close) {
            this.$.contentWrapper.classList.add('animating');
            this.playAnimation('close');
          } else {
            Polymer.IronOverlayBehaviorImpl._renderClosed.apply(this, arguments);
          }
        },

        /**
         * Called when animation finishes on the dropdown (when opening or
         * closing). Responsible for "completing" the process of opening or
         * closing the dropdown by positioning it or setting its display to
         * none.
         */
        _onNeonAnimationFinish: function() {
          this.$.contentWrapper.classList.remove('animating');
          if (this.opened) {
            this._finishRenderOpened();
          } else {
            this._finishRenderClosed();
          }
        },

        _onCaptureScroll: function() {
          if (!this.allowOutsideScroll) {
            this._restoreScrollPosition();
          } else {
            this._refitOnScrollRAF && window.cancelAnimationFrame(this._refitOnScrollRAF);
            this._refitOnScrollRAF = window.requestAnimationFrame(this.refit.bind(this));
          }
        },

        /**
         * Memoizes the scroll position of the outside scrolling element.
         * @private
         */
        _saveScrollPosition: function() {
          if (document.scrollingElement) {
            this._scrollTop = document.scrollingElement.scrollTop;
            this._scrollLeft = document.scrollingElement.scrollLeft;
          } else {
            // Since we don't know if is the body or html, get max.
            this._scrollTop = Math.max(document.documentElement.scrollTop, document.body.scrollTop);
            this._scrollLeft = Math.max(document.documentElement.scrollLeft, document.body.scrollLeft);
          }
        },

        /**
         * Resets the scroll position of the outside scrolling element.
         * @private
         */
        _restoreScrollPosition: function() {
          if (document.scrollingElement) {
            document.scrollingElement.scrollTop = this._scrollTop;
            document.scrollingElement.scrollLeft = this._scrollLeft;
          } else {
            // Since we don't know if is the body or html, set both.
            document.documentElement.scrollTop = this._scrollTop;
            document.documentElement.scrollLeft = this._scrollLeft;
            document.body.scrollTop = this._scrollTop;
            document.body.scrollLeft = this._scrollLeft;
          }
        },

        /**
         * Constructs the final animation config from different properties used
         * to configure specific parts of the opening and closing animations.
         */
        _updateAnimationConfig: function() {
          // Update the animation node to be the containedElement.
          var animationNode = this.containedElement;
          var animations = [].concat(this.openAnimationConfig || []).concat(this.closeAnimationConfig || []);
          for (var i = 0; i < animations.length; i++) {
            animations[i].node = animationNode;
          }
          this.animationConfig = {
            open: this.openAnimationConfig,
            close: this.closeAnimationConfig
          };
        },

        /**
         * Updates the overlay position based on configured horizontal
         * and vertical alignment.
         */
        _updateOverlayPosition: function() {
          if (this.isAttached) {
            // This triggers iron-resize, and iron-overlay-behavior will call refit if needed.
            this.notifyResize();
          }
        },

        /**
         * Apply focus to focusTarget or containedElement
         */
        _applyFocus: function () {
          var focusTarget = this.focusTarget || this.containedElement;
          if (focusTarget && this.opened && !this.noAutoFocus) {
            focusTarget.focus();
          } else {
            Polymer.IronOverlayBehaviorImpl._applyFocus.apply(this, arguments);
          }
        }
      });
    })();
  </script>
</dom-module>