function drawStrokedRect(x, y, w, h, color) {
  const cr = this.cr;
  const lw = Math.max(0.55, 0.55 * cr);
  const buffer = this.cache.fg;
  buffer.strokeStyle = color;
  buffer.lineWidth = lw;
  // main rectangle
  buffer.strokeRect(
    x - (lw / 2), y - (lw / 2),
    w + lw, h + lw
  );
}
Draws a stroked rectangle
@param {Number} x
@param {Number} y
@param {Number} w
@param {Number} h
@param {String} color