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 var(--tp-splitter-width, 5px) 1fr;
        }

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

        [hidden] {
          display: none !important;
        }

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

        #splitter {
          display: flex;
          flex-direction: row;
          align-items: center;
          justify-content: center;
          background: var(--tp-splitter-line-color, #3b3b3b);
          cursor: row-resize;
          opacity: 1;
          z-index: 2;
        }

        #splitter:hover {
          background: var(--tp-splitter-line-color-hover, #007dd1);
          opacity: 0.5;
        }
      `
    ];
  }

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

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

  static get properties() {
    return {
      topHidden: { type: Boolean, reflect: true },
      bottomHidden: { type: Boolean, reflect: true },
      dragging: { type: Boolean, reflect: true },
      minSideHeight: { type: Number },
      lateResize: { type: Boolean },
      initialTopHeight: { type: String },
    };
  }

  constructor() {
    super();

    this._disableDrag = this._disableDrag.bind(this);
    this._resize = this._resize.bind(this);
    this._bufferedDelta = 0;
  }

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

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

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

  firstUpdated() {
    if (this.initialTopHeight) {
      this.style.gridTemplateRows = `${this.initialTopHeight} var(--tp-splitter-width, 5px) 1fr`;
    }
  }

  disconnectedCallback() {
    super.disconnectedCallback();
    document.removeEventListener('mouseup', this._disableDrag)
    document.removeEventListener('mousemove', this._resize);
    document.body.style['userSelect'] = '';
  }

  _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;

    let finalHeight;
    if (this.lateResize && this._bufferedDelta) {
      finalHeight = this._topHeight + this._bufferedDelta;
      this.splitter.style.transform = '';
      this.style.gridTemplateRows = `${finalHeight}px 5px 1fr`;
      this._bufferedDelta = 0;
    } else {
      finalHeight = this.top.offsetHeight;
    }

    this.dispatchEvent(new CustomEvent('resize-done', { detail: finalHeight, bubbles: true, composed: true }));
  }

  _resize(e) {
    const delta = e.clientY - this._startY;
    const totalHeight = this.offsetHeight;
    const minHeight = this.minSideHeight || 0;
    const splitterWidth = parseInt(getComputedStyle(this).getPropertyValue('--tp-splitter-width')) || 5;
    
    // Calculate restricted delta
    const maxDelta = totalHeight - splitterWidth - minHeight - this._topHeight;
    const minDelta = -this._topHeight + minHeight;
    const restrictedDelta = Math.max(minDelta, Math.min(delta, maxDelta));
  
    if (this.lateResize) {
      this._bufferedDelta = restrictedDelta;
      this.splitter.style.transform = `translateY(${this._bufferedDelta}px)`;
      return;
    }
  
    const newTopHeight = this._topHeight + restrictedDelta;
    this.style.gridTemplateRows = `${newTopHeight}px ${splitterWidth}px 1fr`;
    this.dispatchEvent(new CustomEvent('resized', { detail: null, bubbles: true, composed: true }));
  }
}

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