coral-spectrum/coral-component-sidenav/src/scripts/SideNavLevel.js

/**
 * Copyright 2019 Adobe. All rights reserved.
 * This file is licensed to you under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License. You may obtain a copy
 * of the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under
 * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
 * OF ANY KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */

import {commons} from '../../../coral-utils';
import {BaseComponent} from '../../../coral-base-component';
import {Decorator} from '../../../coral-decorator';

const CLASSNAME = '_coral-SideNav';

/**
 @class Coral.SideNav.Level
 @classdesc A SideNav Level component
 @htmltag coral-sidenav-level
 @extends {HTMLElement}
 @extends {BaseComponent}
 */
const SideNavLevel = Decorator(class extends BaseComponent(HTMLElement) {
  /** @ignore */
  static get observedAttributes() {
    return super.observedAttributes.concat(['_expanded']);
  }

  /** @ignore */
  attributeChangedCallback(name, oldValue, value) {
    if (name === '_expanded') {
      const isExpanded = value === 'on';

      if (oldValue !== value) {
        this.classList.toggle('is-expanded', isExpanded);

        // Do animation in next frame to avoid a forced reflow
        window.requestAnimationFrame(() => {
          // Don't animate on initialization
          if (this._animate) {
            // Remove height as we want the level to naturally grow if content is added later
            commons.transitionEnd(this, () => {
              if (isExpanded) {
                this.style.height = '';
              } else {
                this.hidden = true;
              }
            });

            // Force height to enable transition
            if (!isExpanded) {
              this.style.height = `${this.scrollHeight}px`;
            } else {
              this.hidden = false;
            }

            // We read the offset height to force a reflow, this is needed to start the transition between absolute values
            // https://blog.alexmaccaw.com/css-transitions under Redrawing
            // eslint-disable-next-line no-unused-vars
            const offsetHeight = this.offsetHeight;

            this.style.height = isExpanded ? `${this.scrollHeight}px` : 0;
          } else {
            // Make sure it's animated next time
            this._animate = true;

            // Hide it on initialization if closed
            if (!isExpanded) {
              this.style.height = 0;
              this.hidden = true;
            }
          }
        });
      }
    } else {
      super.attributeChangedCallback(name, oldValue, value);
    }
  }

  /** @ignore */
  render() {
    super.render();

    this.classList.add(CLASSNAME);

    // a11y
    this.setAttribute('role', 'region');
  }
});

export default SideNavLevel;