code: private Paint createTitleBarGradient(Shape s, int titleHeight, FourColors defColors) {
          Rectangle2D bounds = s.getBounds2D();
          float       midX   = (float) bounds.getCenterX();
          float       y      = (float) bounds.getY();
          float       h      = (float) bounds.getHeight();
  
          return createGradient(midX, y, midX, y + h, new float[] { 0.0f, 1.0f },
                                new Color[] { defColors.top, defColors.upperMid });
      }
docs: Create the gradient to paint the frame interior.
  
  @param  s           the interior shape.
  @param  titleHeight the height of the title bar, or 0 if none.
  @param  defColors   the color set to construct the gradient from.
  
  @return the gradient.