# global variables and funtions

_root = tk.Tk()
_root.withdraw()

_update_lasttime = time.time()

def update(rate=None):
global _update_lasttime
if rate:
   now = time.time()
   pauseLength = 1/rate-(now-_update_lasttime)
   if pauseLength > 0:
         time.sleep(pauseLength)
         _update_lasttime = now + pauseLength
   else:
         _update_lasttime = now

_root.update()

# Graphics classes start here

class GraphWin(tk.Canvas):

"""A GraphWin is a toplevel window for displaying graphics."""

def __init__(self, title="Graphics Window",
            width=200, height=200, autoflush=True):
   assert type(title) == type(""), "Title must be a string"
   master = tk.Toplevel(_root)
   master.protocol("WM_DELETE_WINDOW", self.close)
   tk.Canvas.__init__(self, master, width=width, height=height,
                        highlightthickness=0, bd=0)
   self.master.title(title)
   self.pack()
   master.resizable(0,0)
   self.foreground = "black"
   self.items = []
   self.mouseX = None
   self.mouseY = None
   self.bind("<Button-1>", self._onClick)
   self.bind_all("<Key>", self._onKey)
   self.height = int(height)
   self.width = int(width)
   self.autoflush = autoflush
   self._mouseCallback = None
   self.trans = None
   self.closed = False
   master.lift()
   self.lastKey = ""
   if autoflush: _root.update()

def __repr__(self):
   if self.isClosed():
         return "<Closed GraphWin>"
   else:
         return "GraphWin('{}', {}, {})".format(self.master.title(),
                                          self.getWidth(),
                                          self.getHeight())

def __str__(self):
   return repr(self)

def __checkOpen(self):
   if self.closed:
         raise GraphicsError("window is closed")

def _onKey(self, evnt):
   self.lastKey = evnt.keysym

def setBackground(self, color):
   """Set background color of the window"""
   self.__checkOpen()
   self.config(bg=color)
   self.__autoflush()

def setCoords(self, x1, y1, x2, y2):
   """Set coordinates of window to run from (x1,y1) in the
   lower-left corner to (x2,y2) in the upper-right corner."""
   self.trans = Transform(self.width, self.height, x1, y1, x2, y2)
   self.redraw()

def close(self):
   """Close the window"""

   if self.closed: return
   self.closed = True
   self.master.destroy()
   self.__autoflush()

def isClosed(self):
   return self.closed

def isOpen(self):
   return not self.closed

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