tp-splitter/tp-vsplitter.js

/**
@license
Copyright (c) 2023 trading_peter
*/

import { LitElement, html, css } from 'lit';

class TpVSplitter extends LitElement {
  static get styles() {
    return [
      css`
        :host {
          display: grid;
          grid-template-columns: 1fr 5px 1fr;
        }

        #left,
        #right {
          position: relative;
          overflow: hidden;
        }

        .splitter {
          background: var(--lighter-black);
          cursor: col-resize;
          opacity: 1;
        }

        .splitter:hover {
          background: var(--hl-color);
          opacity: 0.5;
        }
      `
    ];
  }

  render() {
    return html`
      <div id="left"><slot name="left"></slot></div>
      <div class="splitter" @mousedown=${this._enableDrag}></div>
      <div id="right"><slot name="right"></slot></div>
    `;
  }

  static get properties() {
    return {
      columns: { type: String },
      _dragging: { type: Boolean },
    };
  }

  constructor() {
    super();

    this._disableDrag = this._disableDrag.bind(this);
    this._resize = this._resize.bind(this);
  }

  get left() {
    return this.shadowRoot.querySelector('#left');
  }

  get right() {
    return this.shadowRoot.querySelector('#right');
  }

  shouldUpdate(changes) {
    if (changes.has('columns')) {
      this.style.gridTemplateColumns = this.columns;
    }

    return true;
  }

  _enableDrag(e) {
    document.addEventListener('mouseup', this._disableDrag)
    document.addEventListener('mousemove', this._resize);
    document.body.style['userSelect'] = 'none';
    this._startX = e.clientX;
    this._topWidth = this.left.offsetWidth;
    this._dragging = true;
  }

  _disableDrag() {
    document.removeEventListener('mouseup', this._disableDrag)
    document.removeEventListener('mousemove', this._resize);
    document.body.style['userSelect'] = '';
    this._dragging = false;
    this.dispatchEvent(new CustomEvent('resize-done', { detail: this.style.gridTemplateColumns, bubbles: true, composed: true }));
  }

  _resize(e) {
    const delta = e.clientX - this._startX;
    this.style.gridTemplateColumns = `${this._topWidth + delta}px 5px 1fr`;
    this.dispatchEvent(new CustomEvent('resized', { detail: null, bubbles: true, composed: true }));
  }
}

window.customElements.define('tp-vsplitter', TpVSplitter);