class Screen:
  width = None
  height = None
  x0 = None
  y0 = None
  
  def __init__(self, width, height):
    self.width = width
    self.height = height
    self.x0 = int(width/2)
    self.y0 = int(height/2)
    
    self.screen = [[' ' for x in range(width)] for y in range(height)]


  def setPoint(self, x, y, v):
    self.screen[self.x0+x][self.y0-y] = v
      
  
  def moveOrigin(self, dx, dy):
    self.x0 += dx
    self.y0 -= dy


  def printScreen(self, fileName = None):
    s = ""
    for y in range(self.height):
      l = ""
      for x in range(self.width):
        v = self.screen[x][y]
        if x-self.x0 == 0 and y-self.y0 == 0:
          c = "+" if v == " " else v
        elif x-self.x0 == 0:
          c = "|" if v == " " else v
        elif y-self.y0 == 0:
          c = "-" if v == " " else v
        else:
          c = v
            
        l += c
      s += l + "\n"
        
    if fileName is None:
      print(s)
    else:
      with open(fileName, "wt") as f:
        f.write(s)