SerializeAddon.ts

import { Terminal, ITerminalAddon, IBufferCell } from 'xterm';

export class SerializeAddon implements ITerminalAddon {
  private _terminal: Terminal|undefined = undefined;
  public dispose(): void {}
  public activate(terminal: Terminal): void {
    this._terminal = terminal;
  }

  private _extractAttributes(oldCell: IBufferCell, newCell: IBufferCell): string {
    if (oldCell.equalAttibutes(newCell)) {
      return '';
    }
    const switches: number[] = [];
    // flags
    if (!oldCell.equalFlags(newCell)) {
      if (oldCell.flags.bold !== newCell.flags.bold) switches.push(newCell.flags.bold ? 1 : 22);
      if (oldCell.flags.underline !== newCell.flags.underline) switches.push(newCell.flags.underline ? 4 : 24);
      if (oldCell.flags.inverse !== newCell.flags.inverse) switches.push(newCell.flags.inverse ? 7 : 27);
      if (oldCell.flags.invisible !== newCell.flags.invisible) switches.push(newCell.flags.invisible ? 8 : 28);
      if (oldCell.flags.blink !== newCell.flags.blink) switches.push(newCell.flags.blink ? 5 : 25);
      if (oldCell.flags.italic !== newCell.flags.italic) switches.push(newCell.flags.italic ? 3 : 23);
      if (oldCell.flags.dim !== newCell.flags.dim) switches.push(newCell.flags.dim ? 2 : 22);
    }
    // colors
    if (!oldCell.equalFg(newCell)) {
      switch (newCell.fg.colorMode) {
        case 'RGB':
          switches.push(38);
          switches.push(2);
          switches.push((newCell.fg.color >> 16) & 0xFF);
          switches.push((newCell.fg.color >> 8) & 0xFF);
          switches.push(newCell.fg.color & 0xFF);
          break;
        case 'P256':
          switches.push(38);
          switches.push(5);
          switches.push(newCell.fg.color);
          break;
        case 'P16':
          switches.push(newCell.fg.color & 8 ? 90 + (newCell.fg.color & 7) : 30 + (newCell.fg.color & 7));
          break;
        default:
          switches.push(39);
      }
    }
    if (!oldCell.equalBg(newCell)) {
      switch (newCell.bg.colorMode) {
        case 'RGB':
          switches.push(48);
          switches.push(2);
          switches.push((newCell.bg.color >> 16) & 0xFF);
          switches.push((newCell.bg.color >> 8) & 0xFF);
          switches.push(newCell.bg.color & 0xFF);
          break;
        case 'P256':
          switches.push(48);
          switches.push(5);
          switches.push(newCell.bg.color);
          break;
        case 'P16':
          switches.push(newCell.bg.color & 8 ? 100 + (newCell.bg.color & 7) : 40 + (newCell.bg.color & 7));
          break;
        default:
          switches.push(49);
      }
    }
    if (switches.length) {
      return `\x1b[${switches.join(';')}m`;
    }
    return '';
  }

  public serialize(): string {
    if (!this._terminal) {
      return '';
    }

    // cells for ref style usage
    // we need two of them to flip between old and new cell
    const cell1 = this._terminal.buffer.getNullCell();
    const cell2 = this._terminal.buffer.getNullCell();
    let oldCell = cell1;

    const result: string[] = [];

    const end = this._terminal.buffer.length;
    for (let y = 0; y < end; ++y) {
      const sLine: string[] = [];
      const line = this._terminal.buffer.getLine(y);
      if (!line) {
        continue;
      }
      const length = this._terminal.cols;
      for (let x = 0; x < length;) {
        const newCell = line.getCell(x, oldCell === cell1 ? cell2 : cell1);
        if (!newCell) {
          continue;
        }
        const diff = this._extractAttributes(oldCell, newCell);
        if (diff) {
          sLine.push(diff);
          oldCell = newCell;
        }
        sLine.push(newCell.char || ' ');
        x += newCell.width || 1;  // always advance by 1!
      }
      result.push(sLine.join(''));
    }
    return result.join('\r\n');
  }
}