code: def setbb(self, x, y):
          
          self.__xmin = min(self.__xmin, max(x, self.__clip_box[0]))
          self.__xmax = max(self.__xmax, min(x, self.__clip_box[2]))
          self.__ymin = min(self.__ymin, max(y, self.__clip_box[1]))
          self.__ymax = max(self.__ymax, min(y, self.__clip_box[3]))
docs: Call this method when point (X,Y) is to be drawn in the
          canvas. This methods expands the bounding box to include
          this point.