iron-iconset-svg.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 '@polymer/polymer/polymer-legacy.js';

import {IronMeta} from '@polymer/iron-meta/iron-meta.js';
import {Polymer} from '@polymer/polymer/lib/legacy/polymer-fn.js';
import {dom} from '@polymer/polymer/lib/legacy/polymer.dom.js';
/**
 * The `iron-iconset-svg` element allows users to define their own icon sets
 * that contain svg icons. The svg icon elements should be children of the
 * `iron-iconset-svg` element. Multiple icons should be given distinct id's.
 *
 * Using svg elements to create icons has a few advantages over traditional
 * bitmap graphics like jpg or png. Icons that use svg are vector based so
 * they are resolution independent and should look good on any device. They
 * are stylable via css. Icons can be themed, colorized, and even animated.
 *
 * Example:
 *
 *     <iron-iconset-svg name="my-svg-icons" size="24">
 *       <svg>
 *         <defs>
 *           <g id="shape">
 *             <rect x="12" y="0" width="12" height="24" />
 *             <circle cx="12" cy="12" r="12" />
 *           </g>
 *         </defs>
 *       </svg>
 *     </iron-iconset-svg>
 *
 * This will automatically register the icon set "my-svg-icons" to the iconset
 * database.  To use these icons from within another element, make a
 * `iron-iconset` element and call the `byId` method
 * to retrieve a given iconset. To apply a particular icon inside an
 * element use the `applyIcon` method. For example:
 *
 *     iconset.applyIcon(iconNode, 'car');
 *
 * @element iron-iconset-svg
 * @demo demo/index.html
 * @implements {Polymer.Iconset}
 */
Polymer({
  is: 'iron-iconset-svg',
  /** @override */
  _template: null,

  properties: {

    /**
     * The name of the iconset.
     */
    name: {type: String, observer: '_nameChanged'},

    /**
     * The size of an individual icon. Note that icons must be square.
     */
    size: {type: Number, value: 24},

    /**
     * Set to true to enable mirroring of icons where specified when they are
     * stamped. Icons that should be mirrored should be decorated with a
     * `mirror-in-rtl` attribute.
     *
     * NOTE: For performance reasons, direction will be resolved once per
     * document per iconset, so moving icons in and out of RTL subtrees will
     * not cause their mirrored state to change.
     */
    rtlMirroring: {type: Boolean, value: false},

    /**
     * Set to true to measure RTL based on the dir attribute on the body or
     * html elements (measured on document.body or document.documentElement as
     * available).
     */
    useGlobalRtlAttribute: {type: Boolean, value: false}
  },

  /** @override */
  created: function() {
    this._meta = new IronMeta({type: 'iconset', key: null, value: null});
  },

  /** @override */
  attached: function() {
    this.style.display = 'none';
  },

  /**
   * Construct an array of all icon names in this iconset.
   *
   * @return {!Array} Array of icon names.
   */
  getIconNames: function() {
    this._icons = this._createIconMap();
    return Object.keys(this._icons).map(function(n) {
      return this.name + ':' + n;
    }, this);
  },

  /**
   * Applies an icon to the given element.
   *
   * An svg icon is prepended to the element's shadowRoot if it exists,
   * otherwise to the element itself.
   *
   * If RTL mirroring is enabled, and the icon is marked to be mirrored in
   * RTL, the element will be tested (once and only once ever for each
   * iconset) to determine the direction of the subtree the element is in.
   * This direction will apply to all future icon applications, although only
   * icons marked to be mirrored will be affected.
   *
   * @method applyIcon
   * @param {Element} element Element to which the icon is applied.
   * @param {string} iconName Name of the icon to apply.
   * @return {?Element} The svg element which renders the icon.
   */
  applyIcon: function(element, iconName) {
    // Remove old svg element
    this.removeIcon(element);
    // install new svg element
    var svg = this._cloneIcon(
        iconName, this.rtlMirroring && this._targetIsRTL(element));
    if (svg) {
      // insert svg element into shadow root, if it exists
      var pde = dom(element.root || element);
      pde.insertBefore(svg, pde.childNodes[0]);
      return element._svgIcon = svg;
    }
    return null;
  },

  /**
   * Remove an icon from the given element by undoing the changes effected
   * by `applyIcon`.
   *
   * @param {Element} element The element from which the icon is removed.
   */
  removeIcon: function(element) {
    // Remove old svg element
    if (element._svgIcon) {
      dom(element.root || element).removeChild(element._svgIcon);
      element._svgIcon = null;
    }
  },

  /**
   * Measures and memoizes the direction of the element. Note that this
   * measurement is only done once and the result is memoized for future
   * invocations.
   */
  _targetIsRTL: function(target) {
    if (this.__targetIsRTL == null) {
      if (this.useGlobalRtlAttribute) {
        var globalElement =
            (document.body && document.body.hasAttribute('dir')) ?
            document.body :
            document.documentElement;

        this.__targetIsRTL = globalElement.getAttribute('dir') === 'rtl';
      } else {
        if (target && target.nodeType !== Node.ELEMENT_NODE) {
          target = target.host;
        }

        this.__targetIsRTL =
            target && window.getComputedStyle(target)['direction'] === 'rtl';
      }
    }

    return this.__targetIsRTL;
  },

  /**
   *
   * When name is changed, register iconset metadata
   *
   */
  _nameChanged: function() {
    this._meta.value = null;
    this._meta.key = this.name;
    this._meta.value = this;

    this.async(function() {
      this.fire('iron-iconset-added', this, {node: window});
    });
  },

  /**
   * Create a map of child SVG elements by id.
   *
   * @return {!Object} Map of id's to SVG elements.
   */
  _createIconMap: function() {
    // Objects chained to Object.prototype (`{}`) have members. Specifically,
    // on FF there is a `watch` method that confuses the icon map, so we
    // need to use a null-based object here.
    var icons = Object.create(null);
    dom(this).querySelectorAll('[id]').forEach(function(icon) {
      icons[icon.id] = icon;
    });
    return icons;
  },

  /**
   * Produce installable clone of the SVG element matching `id` in this
   * iconset, or `undefined` if there is no matching element.
   *
   * @return {Element} Returns an installable clone of the SVG element
   * matching `id`.
   */
  _cloneIcon: function(id, mirrorAllowed) {
    // create the icon map on-demand, since the iconset itself has no discrete
    // signal to know when it's children are fully parsed
    this._icons = this._icons || this._createIconMap();
    return this._prepareSvgClone(this._icons[id], this.size, mirrorAllowed);
  },

  /**
   * @param {Element} sourceSvg
   * @param {number} size
   * @param {Boolean} mirrorAllowed
   * @return {Element}
   */
  _prepareSvgClone: function(sourceSvg, size, mirrorAllowed) {
    if (sourceSvg) {
      var content = sourceSvg.cloneNode(true),
          svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg'),
          viewBox =
              content.getAttribute('viewBox') || '0 0 ' + size + ' ' + size,
          cssText =
              'pointer-events: none; display: block; width: 100%; height: 100%;';

      if (mirrorAllowed && content.hasAttribute('mirror-in-rtl')) {
        cssText +=
            '-webkit-transform:scale(-1,1);transform:scale(-1,1);transform-origin:center;';
      }

      svg.setAttribute('viewBox', viewBox);
      svg.setAttribute('preserveAspectRatio', 'xMidYMid meet');
      svg.setAttribute('focusable', 'false');
      // TODO(dfreedm): `pointer-events: none` works around
      // https://crbug.com/370136
      // TODO(sjmiles): inline style may not be ideal, but avoids requiring a
      // shadow-root
      svg.style.cssText = cssText;
      svg.appendChild(content).removeAttribute('id');
      return svg;
    }
    return null;
  }

});