code: @Override
      protected boolean prepare(final Context2D context, final Attributes attr, final double alpha)
      {
          final double r = attr.getRadius();
  
          if (r > 0)
          {
              context.beginPath();
  
              context.arc(0, 0, r, 0, Math.PI * 2, true);
  
              context.closePath();
  
              return true;
          }
          return false;
      }
docs: Draws this circle
  
  @param context the {@link Context2D} used to draw this circle.