pack method

@override Uint8List pack()

Corresponding parser should be called from frame_app data handler

Implementation

@override
Uint8List pack() {
  if (_lines.isEmpty) {
    throw Exception('_lines is empty: call rasterize() before pack()');
  }

  int widthMsb = _width >> 8;
  int widthLsb = _width & 0xFF;
  int heightMsb = _totalHeight >> 8;
  int heightLsb = _totalHeight & 0xFF;

  // store the x (16-bit) and y (16-bit) offsets as pairs for each of the lines
  Uint8List offsets = Uint8List(_displayLineMetrics.length * 4);

  for (int i = 0; i < _displayLineMetrics.length; i++) {
    var lm = _displayLineMetrics[i];
    int xOffset = lm.left.toInt();
    int yOffset = (lm.baseline - lm.ascent).toInt();
    offsets[4 * i] = xOffset >> 8;
    offsets[4 * i + 1] = xOffset & 0xFF;
    offsets[4 * i + 2] = yOffset >> 8;
    offsets[4 * i + 3] = yOffset & 0xFF;
  }

  // special marker for Block header 0xFF, size of the block (WxH), num lines, offsets within block for each line
  return Uint8List.fromList([
    0xFF,
    widthMsb,
    widthLsb,
    heightMsb,
    heightLsb,
    _lines.length & 0xFF,
    ...offsets
  ]);
}