code: protected final boolean isValidSize (int width, int height)
      {
          if (width < 0 || height < 0) {
              log.warning("Attempt to add invalid dirty region?!",
                          "size", (width + "x" + height), new Exception());
              return false;
  
          } else if (width == 0 || height == 0) {
              // no need to complain about zero sized rectangles, just ignore them
              return false;
  
          } else {
              return true;
          }
      }
docs: Used to ensure our dirty regions are not invalid.