    # File ../lib/fox/core.rb, line 228
        def +(other)
          if other.kind_of?(FXRectangle)
            xx = [other.x, self.x].min
            ww = [other.x+other.w, self.x+self.w].max - xx
            yy = [other.y, self.y].min
            hh = [other.y+other.h, self.y+self.h].max - yy
            FXRectangle.new(xx, yy, ww, hh)
          else
            raise TypeError, 'expected FXRectangle'
          end
        end