sclass AbstractTickerPainter extends ScaledDiagram {
  // how many lines are drawn to indicate percent changes
  settable double percentLineDistance = 0.1;
  
  settable bool drawPercentLines = true;
  
  void drawPercentLines(Graphics2D g) {
    if (!drawPercentLines) ret;
    double percentStep = center(verticalRange)*percentLineDistance/100;
    for (double y = verticalRange.start; y <= verticalRange.end; y += percentStep) {
      var yy = iround(yToScreen(y));
      drawLine(g, 0, yy, w-1, yy, Color.gray);
    }
  }
}