tp-splitter/tp-hsplitter.js

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

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

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

        :host([tophidden]),
        :host([bottomhidden]) {
          grid-template-rows: 1fr;
        }

        [hidden] {
          display: none !important;
        }

        #top,
        #bottom {
          position: relative;
          overflow: hidden;
        }

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

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

  render() {
    const { topHidden, bottomHidden } = this;

    return html`
      <div id="top" ?hidden=${topHidden}><slot name="top"></slot></div>
      <div class="splitter" @mousedown=${this._enableDrag} ?hidden=${topHidden || bottomHidden}></div>
      <div id="bottom" ?hidden=${bottomHidden}><slot name="bottom"></slot></div>
    `;
  }

  static get properties() {
    return {
      topHidden: { type: Boolean, reflect: true },
      bottomHidden: { type: Boolean, reflect: true },
      rows: { type: String },
      _dragging: { type: Boolean },
    };
  }

  constructor() {
    super();

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

  shouldUpdate(changes) {
    if (changes.has('rows')) {
      this.style.gridTemplateRows = this.rows;
    }

    return true;
  }

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

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

  _enableDrag(e) {
    document.addEventListener('mouseup', this._disableDrag)
    document.addEventListener('mousemove', this._resize);
    document.body.style['userSelect'] = 'none';
    this._startY = e.clientY;
    this._topHeight = this.top.offsetHeight;
    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.gridTemplateRows, bubbles: true, composed: true }));
  }

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

window.customElements.define('tp-hsplitter', TpHSplitter);