prependString method

void prependString(Buffer newbuf, String str)

Prepends raw escape sequences to the output buffer.

Scrolls the screen content in newbuf to make room for str, which is inserted at the top of the visible area.

Implementation

void prependString(Buffer newbuf, String str) {
  // Upstream: `third_party/ultraviolet/terminal_renderer.go` (`PrependString`).
  if (str.isEmpty) return;

  final w = newbuf.width();
  final h = newbuf.height();
  _move(newbuf, 0, h - 1);

  final lines = str.split('\n');
  var offset = 0;
  for (final line in lines) {
    final lineWidth = WidthMethod.wcwidth.stringWidth(line);
    if (w > 0 && lineWidth > w) {
      offset += (lineWidth ~/ w);
    }
    if (lineWidth == 0 || (w > 0 && lineWidth % w != 0)) {
      offset++;
    }
  }

  if (offset <= 0) return;

  _buf.write(List.filled(offset, '\n').join());
  _cur.y += offset;

  // Move to top and insert new lines.
  _moveCursor(newbuf, 0, 0, false);
  _buf.write(UvAnsi.insertLine(offset));
  for (final line in lines) {
    _buf.write(line);
    _buf.write('\r\n');
  }
}