vaadin-radio-group.html

<!--
@license
Copyright (c) 2017 Vaadin Ltd.
This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
-->

<link rel="import" href="../../polymer/polymer-element.html">
<link rel="import" href="../../polymer/lib/utils/flattened-nodes-observer.html">
<link rel="import" href="../../vaadin-themable-mixin/vaadin-themable-mixin.html">
<link rel="import" href="vaadin-radio-button.html">

<dom-module id="vaadin-radio-group">
  <template>
    <style>
      :host {
        display: inline-block;
      }

      [part="label"] {
        display: block;
      }

      [part="label"]:empty {
        display: none;
      }
    </style>
    <label part="label">[[label]]</label>
    <slot id="slot"></slot>
  </template>

  <script>
    (function() {
      /**
       * `<vaadin-radio-group>` is a Polymer element for grouping vaadin-radio-buttons.
       *
       * ```html
       * <vaadin-radio-group>
       *   <vaadin-radio-button name="foo">Foo</vaadin-radio-button>
       *   <vaadin-radio-button name="bar">Bar</vaadin-radio-button>
       *   <vaadin-radio-button name="baz">Baz</vaadin-radio-button>
       * </vaadin-radio-group>
       * ```
       *
       * ### Styling
       *
       * The following shadow DOM parts are available for styling:
       *
       * Part name | Description
       * ----------------|----------------
       * `label` | The label element
       *
       * The following state attributes are available for styling:
       *
       * Attribute  | Description | Part name
       * -----------|-------------|------------
       * `disabled` | Set when the radio group and its children are disabled. | :host
       * `has-label` | Set when the element has a label | :host
       *
       * See [ThemableMixin – how to apply styles for shadow parts](https://github.com/vaadin/vaadin-themable-mixin/wiki)
       *
       * @memberof Vaadin
       * @mixes Vaadin.ThemableMixin
       * @element vaadin-radio-group
       * @demo demo/index.html
       */
      class RadioGroupElement extends Vaadin.ThemableMixin(Polymer.Element) {
        static get is() {
          return 'vaadin-radio-group';
        }

        static get properties() {
          return {
            /**
             * The current disabled state of the radio group. True if group and all internal radio buttons are disabled.
             */
            disabled: {
              type: Boolean,
              reflectToAttribute: true,
              observer: '_disabledChanged'
            },

            _checkedButton: {
              type: Object,
              observer: '_checkedButtonChanged'
            },

            /**
            * String used for the label element.
            */
            label: {
              type: String,
              value: '',
              observer: '_labelChanged'
            },

            /**
             * Value of the radio group.
             */
            value: {
              type: String,
              notify: true,
              observer: '_valueChanged'
            }
          };
        }

        /**
         * @private
         */
        connectedCallback() {
          super.connectedCallback();
          this._observer = new Polymer.FlattenedNodesObserver(this, (info) => {
            var checkedChangedListener = (e) => {
              if (e.target.checked) {
                this._changeSelectedButton(e.target);
              }
            };

            this._filterRadioButtons(info.addedNodes).forEach(button => {
              button.addEventListener('checked-changed', checkedChangedListener);
              if (this.disabled) {
                button.disabled = true;
              }
            });

            this._filterRadioButtons(info.removedNodes).forEach(button => {
              button.removeEventListener('checked-changed', checkedChangedListener);
            });

          });
        }

        ready() {
          super.ready();

          this._addActiveListeners();

          if (this._radioButtons.length) {
            this._setFocusable(0);
          }

          this.setAttribute('role', 'radiogroup');
        }

        get _radioButtons() {
          return this._filterRadioButtons(this.querySelectorAll('*'));
        }

        _filterRadioButtons(nodes) {
          return Array.from(nodes)
            .filter(child => child instanceof Vaadin.RadioButtonElement);
        }

        _disabledChanged(disabled) {
          this.setAttribute('aria-disabled', disabled);

          this._radioButtons.forEach(button => button.disabled = disabled);
        }

        _addActiveListeners() {
          this.addEventListener('keydown', e => {
            // if e.target is vaadin-radio-group then assign to checkedRadioButton currently checked radio button
            var checkedRadioButton = (e.target == this) ? this._checkedButton : e.target;
            if (this.disabled) {
              return;
            }

            // LEFT, UP - select previous radio button
            if (e.keyCode === 37 || e.keyCode === 38) {
              e.preventDefault();
              this._selectPreviousButton(checkedRadioButton);
            }

            // RIGHT, DOWN - select next radio button
            if (e.keyCode === 39 || e.keyCode === 40) {
              e.preventDefault();
              this._selectNextButton(checkedRadioButton);
            }
          });
        }

        _selectButton(element, setFocusRing) {
          if (this._containsFocus()) {
            element.focus();
            if (setFocusRing) {
              element.setAttribute('focus-ring', '');
            }
          }
          this._changeSelectedButton(element);
        }

        _containsFocus() {
          const root = this.getRootNode();
          // Safari 9 needs polyfilled `_activeElement` to return correct node
          const activeElement = root._activeElement !== undefined ? root._activeElement : root.activeElement;
          return this.contains(activeElement);
        }

        _hasEnabledButtons() {
          return !this._radioButtons.every((button) => button.disabled);
        }

        _selectNextButton(element) {
          if (!this._hasEnabledButtons()) {
            return;
          }

          var nextButton = element.nextElementSibling || this.firstElementChild;

          if (nextButton.disabled) {
            this._selectNextButton(nextButton);
          } else {
            this._selectButton(nextButton, true);
          }
        }

        _selectPreviousButton(element) {
          if (!this._hasEnabledButtons()) {
            return;
          }

          var previousButton = element.previousElementSibling || this.lastElementChild;

          if (previousButton.disabled) {
            this._selectPreviousButton(previousButton);
          } else {
            this._selectButton(previousButton, true);
          }
        }

        _changeSelectedButton(button) {
          this._checkedButton = button;

          this._setFocusable(this._radioButtons.indexOf(button));
        }

        _checkedButtonChanged(checkedButton) {
          this._radioButtons.forEach(button => button.checked = button === checkedButton);

          this.value = checkedButton.value;
        }

        _valueChanged(newV, oldV) {
          if (!this._checkedButton || newV != this._checkedButton.value) {
            const newCheckedButton = this._radioButtons.filter(button => button.value == newV)[0];

            if (newCheckedButton) {
              this._selectButton(newCheckedButton);
            } else {
              console.warn(`No <vaadin-radio-button> with value ${newV} found.`);
            }
          }
        }

        _setFocusable(idx) {
          const items = this._radioButtons;
          items.forEach(e => e.tabindex = e === items[idx] ? 0 : -1);
        }

        _labelChanged(label) {
          if (label) {
            this.setAttribute('has-label', '');
          } else {
            this.removeAttribute('has-label');
          }
        }

      }

      customElements.define(RadioGroupElement.is, RadioGroupElement);

      /**
       * @namespace Vaadin
       */
      window.Vaadin = window.Vaadin || {};
      Vaadin.RadioGroupElement = RadioGroupElement;
    })();
  </script>
</dom-module>