@jupyterlab/ui-components/src/components/styling.ts

// Copyright (c) Jupyter Development Team.
// Distributed under the terms of the Modified BSD License.

import { caretDownEmptyIcon } from '../icon';

/**
 * A namespace for node styling.
 */
export namespace Styling {
  /**
   * Style a node and its child elements with the default tag names.
   *
   * @param node - The base node.
   *
   * @param className - The optional CSS class to add to styled nodes.
   */
  export function styleNode(node: HTMLElement, className = ''): void {
    styleNodeByTag(node, 'select', className);
    styleNodeByTag(node, 'textarea', className);
    styleNodeByTag(node, 'input', className);
    styleNodeByTag(node, 'button', className);
  }

  /**
   * Style a node and its elements that have a given tag name.
   *
   * @param node - The base node.
   *
   * @param tagName - The html tag name to style.
   *
   * @param className - The optional CSS class to add to styled nodes.
   */
  export function styleNodeByTag(
    node: HTMLElement,
    tagName: string,
    className = ''
  ): void {
    if (node.localName === tagName) {
      node.classList.add('jp-mod-styled');
    }
    if (node.localName === 'select') {
      const multiple = node.hasAttribute('multiple');
      wrapSelect(node as HTMLSelectElement, multiple);
    }
    const nodes = node.getElementsByTagName(tagName);
    for (let i = 0; i < nodes.length; i++) {
      const child = nodes[i];
      child.classList.add('jp-mod-styled');
      if (className) {
        child.classList.add(className);
      }
      if (tagName === 'select') {
        const multiple = child.hasAttribute('multiple');
        wrapSelect(child as HTMLSelectElement, multiple);
      }
    }
  }

  /**
   * Wrap a select node.
   */
  export function wrapSelect(
    node: HTMLSelectElement,
    multiple?: boolean
  ): HTMLElement {
    const wrapper = document.createElement('div');
    wrapper.classList.add('jp-select-wrapper');
    node.addEventListener('focus', Private.onFocus);
    node.addEventListener('blur', Private.onFocus);
    node.classList.add('jp-mod-styled');
    if (node.parentElement) {
      node.parentElement.replaceChild(wrapper, node);
    }
    wrapper.appendChild(node);

    if (multiple) {
      wrapper.classList.add('multiple');
    } else {
      // add the icon node
      wrapper.appendChild(
        caretDownEmptyIcon.element({
          tag: 'span',
          stylesheet: 'select',
          right: '8px',
          top: '5px',
          width: '18px'
        })
      );
    }

    return wrapper;
  }
}

/**
 * The namespace for module private data.
 */
namespace Private {
  /**
   * Handle a focus event on a styled select.
   */
  export function onFocus(event: FocusEvent): void {
    const target = event.target as Element;
    const parent = target.parentElement;
    if (!parent) {
      return;
    }
    if (event.type === 'focus') {
      parent.classList.add('jp-mod-focused');
    } else {
      parent.classList.remove('jp-mod-focused');
    }
  }
}