iron-collapse.js

/**
@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
*/
import {IronResizableBehavior} from '@polymer/iron-resizable-behavior/iron-resizable-behavior.js';
import {Polymer} from '@polymer/polymer/lib/legacy/polymer-fn.js';
import {dom} from '@polymer/polymer/lib/legacy/polymer.dom.js';
import {html} from '@polymer/polymer/lib/utils/html-tag.js';
import {Base} from '@polymer/polymer/polymer-legacy.js';

/**
`iron-collapse` creates a collapsible block of content.  By default, the content
will be collapsed.  Use `opened` or `toggle()` to show/hide the content.

    <button on-click="toggle">toggle collapse</button>

    <iron-collapse id="collapse">
      <div>Content goes here...</div>
    </iron-collapse>

    ...

    toggle: function() {
      this.$.collapse.toggle();
    }

`iron-collapse` adjusts the max-height/max-width of the collapsible element to
show/hide the content.  So avoid putting padding/margin/border on the
collapsible directly, and instead put a div inside and style that.

    <style>
      .collapse-content {
        padding: 15px;
        border: 1px solid #dedede;
      }
    </style>

    <iron-collapse>
      <div class="collapse-content">
        <div>Content goes here...</div>
      </div>
    </iron-collapse>

### Styling

The following custom properties and mixins are available for styling:

Custom property | Description | Default
----------------|-------------|----------
`--iron-collapse-transition-duration` | Animation transition duration | `300ms`

@demo demo/index.html
@element iron-collapse
*/
Polymer({
  /** @override */
  _template: html`
    <style>
      :host {
        display: block;
        transition-duration: var(--iron-collapse-transition-duration, 300ms);
        /* Safari 10 needs this property prefixed to correctly apply the custom property */
        -webkit-transition-duration: var(--iron-collapse-transition-duration, 300ms);
        overflow: visible;
      }

      :host(.iron-collapse-closed) {
        display: none;
      }

      :host(:not(.iron-collapse-opened)) {
        overflow: hidden;
      }
    </style>

    <slot></slot>
`,

  is: 'iron-collapse',
  behaviors: [IronResizableBehavior],

  properties: {

    /**
     * If true, the orientation is horizontal; otherwise is vertical.
     */
    horizontal: {type: Boolean, value: false, observer: '_horizontalChanged'},

    /**
     * Set opened to true to show the collapse element and to false to hide it.
     */
    opened:
        {type: Boolean, value: false, notify: true, observer: '_openedChanged'},

    /**
     * When true, the element is transitioning its opened state. When false,
     * the element has finished opening/closing.
     */
    transitioning: {type: Boolean, notify: true, readOnly: true},

    /**
     * Set noAnimation to true to disable animations.
     */
    noAnimation: {type: Boolean},

    /**
     * Stores the desired size of the collapse body.
     * @private
     */
    _desiredSize: {type: String, value: ''}
  },

  get dimension() {
    return this.horizontal ? 'width' : 'height';
  },

  /**
   * `maxWidth` or `maxHeight`.
   * @private
   */
  get _dimensionMax() {
    return this.horizontal ? 'maxWidth' : 'maxHeight';
  },

  /**
   * `max-width` or `max-height`.
   * @private
   */
  get _dimensionMaxCss() {
    return this.horizontal ? 'max-width' : 'max-height';
  },

  hostAttributes: {
    role: 'group',
    'aria-hidden': 'true',
  },

  listeners: {transitionend: '_onTransitionEnd'},

  /**
   * Toggle the opened state.
   *
   * @method toggle
   */
  toggle: function() {
    this.opened = !this.opened;
  },

  show: function() {
    this.opened = true;
  },

  hide: function() {
    this.opened = false;
  },

  /**
   * Updates the size of the element.
   * @param {string} size The new value for `maxWidth`/`maxHeight` as css property value, usually `auto` or `0px`.
   * @param {boolean=} animated if `true` updates the size with an animation, otherwise without.
   */
  updateSize: function(size, animated) {
    // Consider 'auto' as '', to take full size.
    size = size === 'auto' ? '' : size;

    var willAnimate = animated && !this.noAnimation && this.isAttached &&
        this._desiredSize !== size;

    this._desiredSize = size;

    this._updateTransition(false);
    // If we can animate, must do some prep work.
    if (willAnimate) {
      // Animation will start at the current size.
      var startSize = this._calcSize();
      // For `auto` we must calculate what is the final size for the animation.
      // After the transition is done, _transitionEnd will set the size back to
      // `auto`.
      if (size === '') {
        this.style[this._dimensionMax] = '';
        size = this._calcSize();
      }
      // Go to startSize without animation.
      this.style[this._dimensionMax] = startSize;
      // Force layout to ensure transition will go. Set scrollTop to itself
      // so that compilers won't remove it.
      this.scrollTop = this.scrollTop;
      // Enable animation.
      this._updateTransition(true);
      // If final size is the same as startSize it will not animate.
      willAnimate = (size !== startSize);
    }
    // Set the final size.
    this.style[this._dimensionMax] = size;
    // If it won't animate, call transitionEnd to set correct classes.
    if (!willAnimate) {
      this._transitionEnd();
    }
  },

  /**
   * enableTransition() is deprecated, but left over so it doesn't break
   * existing code. Please use `noAnimation` property instead.
   *
   * @method enableTransition
   * @deprecated since version 1.0.4
   */
  enableTransition: function(enabled) {
    Base._warn(
        '`enableTransition()` is deprecated, use `noAnimation` instead.');
    this.noAnimation = !enabled;
  },

  _updateTransition: function(enabled) {
    this.style.transitionDuration = (enabled && !this.noAnimation) ? '' : '0s';
  },

  _horizontalChanged: function() {
    this.style.transitionProperty = this._dimensionMaxCss;
    var otherDimension =
        this._dimensionMax === 'maxWidth' ? 'maxHeight' : 'maxWidth';
    this.style[otherDimension] = '';
    this.updateSize(this.opened ? 'auto' : '0px', false);
  },

  _openedChanged: function() {
    this.setAttribute('aria-hidden', !this.opened);

    this._setTransitioning(true);
    this.toggleClass('iron-collapse-closed', false);
    this.toggleClass('iron-collapse-opened', false);
    this.updateSize(this.opened ? 'auto' : '0px', true);

    // Focus the current collapse.
    if (this.opened) {
      this.focus();
    }
  },

  _transitionEnd: function() {
    this.style[this._dimensionMax] = this._desiredSize;
    this.toggleClass('iron-collapse-closed', !this.opened);
    this.toggleClass('iron-collapse-opened', this.opened);
    this._updateTransition(false);
    this.notifyResize();
    this._setTransitioning(false);
  },

  _onTransitionEnd: function(event) {
    if (dom(event).rootTarget === this) {
      this._transitionEnd();
    }
  },

  _calcSize: function() {
    return this.getBoundingClientRect()[this.dimension] + 'px';
  }
});