Class SixelHandler

addons/addon-image/src/SixelHandler.ts:22–109

export class SixelHandler implements IDcsHandler, IResetHandler {
  private _size = 0;
  private _aborted = false;
  private _dec: Decoder | undefined;

  constructor(
    private readonly _opts: IImageAddonOptions,
    private readonly _storage: ImageStorage,
    private readonly _coreTerminal: ITerminalExt
  ) {
    DecoderAsync({
      memoryLimit: this._opts.pixelLimit * 4,
      palette: DEFAULT_PALETTE,
      paletteLimit: this._opts.sixelPaletteLimit
    }).then(d => this._dec = d);
  }

  public reset(): void {
    /**
     * reset sixel decoder to defaults:
     * - release all memory
     * - nullify palette (4096)
     * - apply default palette (256)
     */
    if (this._dec) {
      this._dec.release();
      // FIXME: missing interface on decoder to nullify full palette
      (this._dec as any)._palette.fill(0);
      this._dec.init(0, DEFAULT_PALETTE, this._opts.sixelPaletteLimit);
    }
  }

  public hook(params: IParams): void {
    this._size = 0;
    this._aborted = false;
    if (this._dec) {
      const fillColor = params.params[1] === 1 ? 0 : extractActiveBg(
        this._coreTerminal._core._inputHandler._curAttrData,
        this._coreTerminal._core._themeService?.colors);
      this._dec.init(fillColor, null, this._opts.sixelPaletteLimit);
    }
  }

  public put(data: Uint32Array, start: number, end: number): void {
    if (this._aborted || !this._dec) {
      return;
    }
    this._size += end - start;
    if (this._size > this._opts.sixelSizeLimit) {
      console.warn(`SIXEL: too much data, aborting`);
      this._aborted = true;
      this._dec.release();
      return;
    }
    try {
      this._dec.decode(data, start, end);
    } catch (e) {
      console.warn(`SIXEL: error while decoding image - ${e}`);